SSP – Stratigraphy, Sedimentology & Palaeontology

SSP1.1 – Open session on stratigraphy, sedimentology and palaeontology

EGU22-6816 | Presentations | SSP1.1

Postdepositional Controls on Fossil Body Size Distributions

Niklas Hohmann, Stella Buchwald, Dieter Korn, Christian Klug, Kenneth De Baets, and Emilia Jarochowska

Animal body size provides information about the trophic position and reproductive strategies of species, and the presence of environmental stressors. The distribution of body sizes in fossils can be easily measured, making it an important tool for paleoecological studies. However, preservational and collection biases might influence the primary measurements and thus the results. Intuitively, smaller specimens of the same species should be more prone to destructive processes such as fracturing and dissolution. It is often assumed that body size distributions in death assemblages reflect those in living populations. We test this assumption.
Using the body size distributions in monospecific assemblages of Devonian ammonoids, we show that common depositional environments yield distinct distributions of conch sizes. We then simulate postdepositional conditions in recent analogues of these environments. If conch size is proportional to robustness (or disintegration rate), sedimentation rates and mixing intensities characterizing these recent analogues allow us to reconstruct conch size distributions observed in Devonian counterparts of these environments.
The results show that shape parameters of body size distributions (skewness and kurtosis) are modified in predictable ways in sedimentary environments. This implies that fossil body size distributions are not a direct reflection of ecological signals, but can be altered by postdepositional processes. We conclude that parameters of body size distributions, such as mean and dispersion, may not be comparable with parameters in standing populations. If changes in these parameters coincide with changes in the depositional environment, the effect of (post)depositional processes needs to be considered.

How to cite: Hohmann, N., Buchwald, S., Korn, D., Klug, C., De Baets, K., and Jarochowska, E.: Postdepositional Controls on Fossil Body Size Distributions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6816, https://doi.org/10.5194/egusphere-egu22-6816, 2022.

EGU22-3774 | Presentations | SSP1.1

How UV light photography can be of help to palaeontologists?

Gaia Crippa and Stefano Masini

The analysis of fossil specimens under ultraviolet (UV) light represents a powerful tool in palaeontology. It has been frequently applied in this field only in the last twenty years, although it was discovered at the beginning of the 20th Century. Up to now this technique has been applied mainly on mollusc shells, but the number of studies dealing with other taxa, like vertebrate specimens, is increasing. Despite this, the analysis of fossil specimens under UV light represents a technique still not fully comprehended; the knowledge of the best procedure of sample preparation and photography still needs to be clarified and new data are required to better understand the real potential of this method. Here, we have tested different preparation (bleached vs not bleached specimens) and photographic techniques to define a protocol for UV analysis of fossil specimens and have explored its main applications analysing specimens from different stratigraphic contexts (from the Permian to the Holocene, from Oman to Italy), having different biominerals (calcite, aragonite, bioapatite and silicified and phosphatized specimens) and belonging to invertebrate and vertebrate taxa (bivalves, gastropods, brachiopods, fish, crustacean and reptile); also, we use two different wavelengths: the commonly used 365 nm, and the 440 nm, a “borderline wavelength” here adopted for the first time. Our results indicate that bleach treatment is not recommended for calcite-shelled brachiopods, whereas is suggested for aragonite-shelled molluscs. We show that UV photography enhances morphological characters and colour patterns and allows to distinguish soft-bodied fossils from the matrix, having important implications in several palaeontological fields and no limitations for its application in invertebrate or vertebrate specimens. Also, the use of UV light provides an inexpensive method to detect man-made interventions in fossil specimens and thus fake fossils. However, the nature of the biomineral and shell microstructures cause different UV responses, whereas the stratigraphic context affects specimen preservation influencing pigment preservation.

How to cite: Crippa, G. and Masini, S.: How UV light photography can be of help to palaeontologists?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3774, https://doi.org/10.5194/egusphere-egu22-3774, 2022.

Of the many biocrises that occurred during the Devonian period, the most studied ones are the end-Devonian Kelwasser event (Frasnian-Famennian Boundary) and the Hangenberg event (Devonian-Carboniferous Boundary). However, the Middle Devonian crisis are receiving an increasing attention. The crisis occurring immediately before the Eifelian-Givetian Boundary (ensensis conodont zone) is known as the Kačák event. It has essentially been identified by time-specific lithofacies in deep-environment settings where pelagic faunas (conodonts, ammonoids, dacryoconaridids) suffered extinctions. On the Belgian neritic carbonate shelf system the Kačák event has been identified, in the lower part of the Hanonet Formation where a complex faunal turnover took place but with few changes in the depositional settings as known in deeper environments. The event is also recognised on a palaeobiological base as the pre-crisis Old World Realm fauna-dominated assemblages are suddenly facing the invasion of East American Realm fauna such as siphonophrentid and heliophillid rugose corals. After the crisis, these corals are very uncommon and the Old World Realm assemblages become largely dominant again. This palaeobiological criterion is proposed to help, especially when the typical pelagic guides are missing, in the identification of the Kačák event.

How to cite: Jamart, V. and Denayer, J.: The late Eifelian (Middle Devonian) Kačák event and its effects on rugose coral palaeobiodiversity (Ardennes, Belgium), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9898, https://doi.org/10.5194/egusphere-egu22-9898, 2022.

EGU22-9154 | Presentations | SSP1.1

Fish fossil remains from the Khartam Member, Khuff Formation in Central Saudi Arabia: Implications for placement of the Permo/Triassic Boundary

Jarrah Babiker, John Humphrey, Khalid Al-Ramadan, Jonathan Payne, Michael Kaminski, and Abdullah Alqubalee

Recognition of the Permian/Triassic boundary in Saudi Arabia by previous researchers using a variety of methods has resulted in placement of the boundary at different stratigraphic levels. In this study, we discovered two lithological horizons containing fossil fish teeth (sharks and Actinopterygii) in different stratigraphic positions within the Khartam Member of the Khuff Formation. Thin-section petrography initially revealed the fossil fish teeth, while XRF, XRD, SEM, and QEMSCAN techniques were used to confirm the presence of biogenic apatite. Fish teeth collected from the two stratigraphic levels in the Khartam Member show distinct and different morphological features. The fossil assemblage recovered from the lower unit belongs to the classes Euselachii and Actinopterygii, while fish teeth from the upper unit belong to the shark genus Lissodus.  The stratigraphic position of the recovered Lissodus microfossils supports the previous placement of the Permo/Triassic boundary by Vaslet et al. (2005) and Crasquin-Soleau et al. (2006), who placed the boundary exactly at the stratigraphic boundary between the Lower and Upper Khartam Members. The results of this study do not corroborate the boundary placement by Eltom et al. (2016), who placed the Permo/Triassic boundary in a higher stratigraphic position within the Upper Khartam Member. Lissodus species are common from the Early Triassic to Late Cretaceous, suggesting new paleontological evidence for the placement of the Permo/Triassic boundary in Saudi Arabia.

How to cite: Babiker, J., Humphrey, J., Al-Ramadan, K., Payne, J., Kaminski, M., and Alqubalee, A.: Fish fossil remains from the Khartam Member, Khuff Formation in Central Saudi Arabia: Implications for placement of the Permo/Triassic Boundary, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9154, https://doi.org/10.5194/egusphere-egu22-9154, 2022.

EGU22-8957 | Presentations | SSP1.1 | Highlight

Terminal-Cretaceous Dinosauria and Pterosauria from a Cretaceous-Paleogene mass-death assemblage, Hell Creek Formation, U.S.A.

Robert DePalma, David Unwin, Anton Oleinik, David Burnham, Loren Gurche, Jeremy Klingler, Peter Larson, Thomas Beasley, Uwe Bergmann, Nicholas Edwards, Roy Wogelius, Victoria Egerton, and Phillip Manning

Dinosaurs and pterosaurs, critical components of late Mesozoic terrestrial biomes, have thus far never been reported in-situ from deposits immediately below the Cretaceous-Paleogene (KPg) boundary. Strata from the KPg boundary preserve worldwide evidence of a massive cosmic impact that resulted in grave consequences for Earth’s biota, triggering a rapid global mass extinction that ultimately claimed ~75% of species. While trends in long-term biotic effects are well-documented, little is known about the fate of biota coeval with the impact because well-preserved fossil evidence is lacking for that brief time interval. Here we report the first-known occurrences of in-situ dinosaur and pterosaur remains coincident with the KPg boundary, providing a vantage point that is closer in temporal proximity to the Chicxulub impact than any prior known records for these clades. The fossils, preserved in a Chicxulub impact-triggered surge deposit and mass-death assemblage in the Hell Creek Formation, U.S.A., consist of a well-developed semi-articulated prenatal pterosaur in ovum and partially articulated remains of a subadult ornithischian dinosaur (Family Thescelosauridae). Examination via synchrotron rapid scanning X-ray fluorescence (SRS-XRF), scanning electron microscopy (SEM), and traditional light microscopy revealed extensive preservation of soft tissue consisting of distinct signatures of organic residues as well as three-dimensional structure. The pterosaur embryo, which comprises the first known from the Late Cretaceous and the only example thus far from North America, contributes information pivotal to understanding the prenatal development and early ontogeny of these animals from a time interval for which no such data exists. The ornithischian (c.f. Thescelosaurus sp.) dinosaur, which includes a remarkably complete articulated hind limb enclosed within three-dimensional lithified tubercular skin envelope, provides important data regarding the osseous and soft-tissue anatomy of the Thescelosauridae. In addition to contributing invaluable new anatomical and physiological insights, these specimens constitute the first conclusive evidence of the direct participation of pterosaurs and dinosaurs in the terminal-Cretaceous extinction event.

How to cite: DePalma, R., Unwin, D., Oleinik, A., Burnham, D., Gurche, L., Klingler, J., Larson, P., Beasley, T., Bergmann, U., Edwards, N., Wogelius, R., Egerton, V., and Manning, P.: Terminal-Cretaceous Dinosauria and Pterosauria from a Cretaceous-Paleogene mass-death assemblage, Hell Creek Formation, U.S.A., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8957, https://doi.org/10.5194/egusphere-egu22-8957, 2022.

EGU22-12752 | Presentations | SSP1.1

Palaeobiogeographic evolution and climatic adaptation within the plant family Linaceae

Mahi Bansal, Shivaprakash Nagaraju, Srikanta Murthy, Anjum Farooqui, and Vandana Prasad

Around 37% of the Mediterranean territory is covered with polyploid angiosperms, of which the genus Linum occupies a considerable region. Linum is the most diversified genus of the plant family Linaceae that comprises a “family pair” of Hugonioideae distributed in tropical regions and Linoideae mainly distributed in temperate to subtropical regions. We provide the oldest fossils of Linaceae, comparable to the living genera Linum and Reinwardtia, from the Late Cretaceous Infratrappean Deccan volcano sedimentary sequences of Maharashtra, India. The phylogenetic analysis conducted by combining the morphological characters of the pollen fossils recovered and the pollen morphological as well as molecular characters of extant species of Linaceae reveals that the family originated in the wet and warm tropical zones of South America in the Late Cretaceous. Thereafter, the family dispersed to Africa giving rise to the lineage of Linoideae that further diverged into two main clades, one of which evolved either on seasonally wet areas of Kohistan-Ladakh Island arc (KLIA) or on the Indian Plate in Maastrichtian-Paleocene. The second clade encompassing the genus Linum originated on seasonally wet areas of Africa and later dispersed to Mediterranean region via Boreotropical route in Paleocene where it adapted to seasonally dry climatic conditions that prevailed during late Eocene. The family further expanded its geographical range and spread to Eurasia, and to North America via Bering land bridge. We also propose the dual colonization of Linaceae in India. The seasonally wet lineages dispersed from Africa to India via KLIA in the Maastrichtian-Paleocene. Whereas, the seasonally dry lineages of Linum migrated from Eurasia into India probably during the Oligocene when the climatic conditions were dry and warm arid. The decline in global temperature towards the end of Eocene escalated the diversification rates within Linaceae that is currently found in the regions of meso- and microthermal climate. The next major shift in diversification rate was detected on the crown node of North American Linaceae during the Middle Miocene Climate Transition.

How to cite: Bansal, M., Nagaraju, S., Murthy, S., Farooqui, A., and Prasad, V.: Palaeobiogeographic evolution and climatic adaptation within the plant family Linaceae, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12752, https://doi.org/10.5194/egusphere-egu22-12752, 2022.

EGU22-8602 | Presentations | SSP1.1

Assessing past arthropod diversity - a case study for Eocene ecosystems

Stephanie F. Loria, Ulrich Kottoff, and Danilo Harms

Zoological collections of extant taxa allow assessment of biodiversity only for the past few centuries, when it was already affected by human activity. To understand present-day diversity declines, documenting biodiversity changes in fossil taxa and the drivers behind these shifts is crucial. We present an ongoing project on arthropod palaeodiversity as a case study. In this project, arthropods – particularly arachnids – in different amber deposits are examined to assess the effect of ecosystem shifts and climate variability on biodiversity from the Eocene until today and to analyze evolutionary trends and biogeographical scenarios. We aim to compare past changes with current diversity trends in order to better predict the future of our arachnid fauna.

How to cite: Loria, S. F., Kottoff, U., and Harms, D.: Assessing past arthropod diversity - a case study for Eocene ecosystems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8602, https://doi.org/10.5194/egusphere-egu22-8602, 2022.

EGU22-1086 | Presentations | SSP1.1

Cenozoic larger foraminifera and palaeonvironmental reconstruction from the Prebetic Domain (SE Spain)

Paula Granero Ordóñez, Carles Ferràndez-Cañadell, and Concepción Herrero Matesanz

The Cenozoic shallow marine deposits of the External Prebetic of Alicante (SE Iberian Peninsula) shows a rich association of benthic foraminifera, dominated by hyaline walled macroforaminifera such as myogypsinids, lepidocyclinids and nummulitids. This study analyses the microbiofacies and systematics of benthic foraminifera at genus and species level in the stratigraphic sections of "El Barranc dels Molins", in the surroundings of the locality of Ibi, and in the Natural Park of "El Carrascal de la Font Roja", nearby the city of Alcoi. The aim of this work is to develop a biostratigraphic study complemented by a sequential stratigraphic analysis and a palaeoenvironmental and depositional interpretation.

The section of Ibi includes benthic foraminifera characteristic of the Upper Eocene and the Oligocene, corresponding to SB zones 19 to 23 (Priabonian-Chattian). The Upper Eocene assemblage includes: Borelis vonderschmitti, Orbitolites aff. armoricensis, Nummulites fabianii, Nummulites sp., Discocyclina sp., Asterocyclina sp., Silvestriella tetraedra, Asterigerina rotula, Fabiania cassis, Halkyardia maxima, Chapmanina gassinensis and Acervulina linearis. The Oligonene species identified are: Pennarchaias glynnjonesi, Peneroplis thomasi, P. flabeliformis, Sorites sp., Sivasina egribucakensis, Borelis pygmaeus, B. inflata, Amphistegina bohdanowiczi, A. mammilla, Risananeiza pustulosa, Heterostegina assilinoides, Cycloclypeus carpenter and C. mediterraneus.

This work extends the stratigraphic distribution of Archaias sp. and Sorites sp. to the Chattian (SBZ 23) in the Tethys. It also confirms the extension of the range of Cycloclypeus mediterraneus and Amphistegina mammilla, and the presence of large-sized Victoriella conoidea (more than 3 mm in length) in the Upper Chattian of the Prebetic Domain.

In both localities, the identification of larger foraminifera and other fossil fauna, such as scleractinian corals, indicate a low-latitude shallow marine environment, at a depth of less than 40 metres. The vertical repetition of microbiofacies observed throughout the studied record is consistent with inner carbonate platform environments outgoing aggrading. This high-stand aggrading system was punctuated by low-stand regressive pulses that ended with the subaerial exposure of the inner platform, as indicated by the presence of several Microcodium horizons.

How to cite: Granero Ordóñez, P., Ferràndez-Cañadell, C., and Herrero Matesanz, C.: Cenozoic larger foraminifera and palaeonvironmental reconstruction from the Prebetic Domain (SE Spain), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1086, https://doi.org/10.5194/egusphere-egu22-1086, 2022.

EGU22-9230 | Presentations | SSP1.1

Planktic foraminiferal resilience to the Early Eocene Climatic Optimum (EECO, ~53-49 Ma) at the Atlantic Ocean

Valeria Luciani, Roberta D'Onofrio, Antonella Gandolfi, Gerald R. Dickens, Bridget S. Wade, Massimo Tiepolo, and Enrico Cannaò

There is consensus since the last IPCC report that the rate of climate warming related to high CO2 pressure is generating a strength of the greenhouse state thus the comprehension of marine ecosystems resilience is a pressing humankind issue. The long-term response of the biota under elevated temperatures and CO2 concentrations remains uncertain because modern studies are limited in time.  The geological archive offers the key opportunity to evaluate the resilience of planktic foraminifera on a long-term perspective. Planktic foraminifera are important marine calcifiers, regulating biogeochemical cycles, abundant in marine sediments since the Cretaceous, and largely adopted for paleoecological and paleoceanographic reconstructions as they are extremely sensitive to environmental parameters. The Early Eocene Climatic Optimum (EECO, ~ 53-49 Ma) is a crucial interval of Earth’ history to investigate as recording the maximum temperature and pCO2 of the entire Cenozoic (Zachos et al., 2001, Sciences; Anagnostou et al. 2016, Nature; Inglis et al., 2020 Clim. Past). Our recent research shows that the EECO markedly impacted the planktic foraminifera communities by inducing an important turnover as recorded from the latitudinally spaced Atlantic sites 1051, 125 and 1263. Specifically, the mixed-layer symbiont-bearing genus Morozovella, that dominated tropical-subtropical early Paleogene assemblages, abruptly and permanently declined its abundance (up to one-third), size, and diversity at the EECO beginning, close to the carbon isotope excursion known as the J event (~ 53 Ma) whereas the abundance and diversity of Acarinina markedly increased (Luciani et al., 2016 Clim. Past; Luciani et al. 2017 Paleoceanogr.; Luciani et al. 2017 GloPlaCha; D’Onofrio et al., 2020 Geosciences). In addition, the Morozovella morphospecies (or criptic species) display different coiling direction (the ability to add chambers in clock- or counter-clock wise) that was dominantly dextral below the EECO and becoming dominantly sinistral at the EECO, within ~ 200 kyr after the carbon isotope excursion known as K/X event (~ 52.8 Ma) (Luciani et al. 2021 GloPlaCha). Therefore, the sinistral morphotypes represent the main survivors at the expense of dextral forms, that were less resilient to the EECO stressors. Our stable carbon and oxygen data on dextral and sinistral morphotypes performed below and above the major coiling shift, show that sinistral morphotypes typically have lower δ13C values. The lower δ13C signatures of the sinistral specimens, suggests that they were less dependent on their photosymbiotic partnerships, possibly migrating slightly deeper in the mixed-layer. This strategy could have made them able to better tolerate the pressure occurring during the EECO. Our record strongly advises on a causal relationship to chemical-physical modifications in the surface waters, possibly to the temperature increase. Preliminary Mg/Ca derived paleotemperatures through (LA)-ICP-MS from Site 1263 reveal that Morozovella crater and M. subbotinae record a greater warming at the EECO than Acarinina coalingensis and A. soldadoensis. The higher rise in temperature recorded by morozovellids may explain the reduced symbiotic relationship, even though further geochemical analyses are in progress to explore the influence of other potential stressors such as pH decrease.

How to cite: Luciani, V., D'Onofrio, R., Gandolfi, A., Dickens, G. R., Wade, B. S., Tiepolo, M., and Cannaò, E.: Planktic foraminiferal resilience to the Early Eocene Climatic Optimum (EECO, ~53-49 Ma) at the Atlantic Ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9230, https://doi.org/10.5194/egusphere-egu22-9230, 2022.

EGU22-9591 | Presentations | SSP1.1

Test-size reduction of Tethyan calcareous plankton at the ETM2: combined effect of global warming and biolimiting metals?

Roberta D'Onofrio, Valeria Luciani, Daniela N. Schmidt, Ruby Barrett, Eliana Fornaciari, Luca Giusberti, Gianluca Frija, and Thierry Adatte

The scientific community is increasingly focused on the study of past climate analogues to better comprehend future implications of global warming on marine ecosystem and biogeochemical cycles. Through an integrated calcareous plankton and geochemical approach, we examined the Terche and Madeago (NE Italy) Tethyan sections, that encompass the hyperthermal Eocene Thermal Maximum 2 (ETM2, ~54 Ma). The ETM2 shares similarities with the current climate context such as global warming, carbon cycle perturbations, high pCO2 and ocean acidification, thus representing a key event in which investigate links between climate and biotic changes.

Our planktic foraminiferal and calcareous nannofossil records show significant, though transient, changes in both the sections across this event. Our record of multiple dissolution proxies from both the sections ensures that dissolution did not affect calcareous plankton assemblages. Planktic foraminifera exhibit a marked increase in warm index surface-dweller Acarinina paralleled by a decline in abundance of the deeper-dweller chiloguembelinids and subbotinids. This implies that the ETM2 warming impacted the entire upper water column. Both chiloguembelinids and subbotinids, recognized as eutrophic and colder taxa, may have suffered, beside warming, of reduced food supply at the thermocline due to the increased surface-water remineralization of organic matter as induced by the significant warmth. Increase of Cretaceous calcareous nannofossils testifies reworking related to enhanced hydrological cycle that also generated input of nutrients from land. Surface water eutrophication during the ETM2 was inferred by rise in calcareous nannofossil eutrophic indices. This group proved to be more sensitive to the nutrient supply rather than warming. The ETM2 consequence on marine calcifiers test-size were not previously explored. We provide here new evidence of a striking test size reduction in planktic foraminiferal assemblages (up to 40%) during the ETM2 that involved both the surface and deeper-dweller taxa that is particularly marked at Madeago. Although loss of symbionts (bleaching) is known to affect test calcification, it cannot represent a likely cause in the studied case as both symbiotic and asymbiotic planktic foraminifera were affected at the same scale across the ETM2. The increased abundance of small placoliths Toweius and Ericsonia indicates that size reduction also impacted nannofossils, though to a lesser degree.

We collected Hg (ppb), TOC (wt%) and Hg/TOC (ppb/wt%) data throughout our sections to test whether the reduction in size was related to environmental stressors not commonly linked to the ETM2. An increase in Hg was indeed detected in both sections at the base of the ETM2 and not corresponding to the intervals of reworking. Coeval submarine igneous events in this area might have introduced biolimiting metals thus involving the calcareous plankton productivity and possibly affecting test sizes. We hypothesize that the striking plankton dwarfism here recorded across the ETM2 is the result of the combined effect of paleoenvironmental perturbations induced by this event and increase in biolimiting metals. Our study alerts on possible consequences related to intense warming as associated to igneous events. Further data from different locations are needed to evaluate the geographic extension of impact on test-size variations in calcareous plankton assemblages.

How to cite: D'Onofrio, R., Luciani, V., Schmidt, D. N., Barrett, R., Fornaciari, E., Giusberti, L., Frija, G., and Adatte, T.: Test-size reduction of Tethyan calcareous plankton at the ETM2: combined effect of global warming and biolimiting metals?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9591, https://doi.org/10.5194/egusphere-egu22-9591, 2022.

EGU22-2039 | Presentations | SSP1.1

Preservation of Nummulites tests in shallow-water limestones regarding the Middle Eocene Climate Optimum (Dinaric foreland basin, Croatia)

Vlasta Ćosović, Dunja Aljinović, Damir Bucković, Marina Čančar, Igor Felja, Ines Galovic, Marija Horvat, Dražen Kurtanjek, Igor Pejnović, Đurđica Pezelj, Nenad Tomašić, and Stjepan Coric

The Eocene sediments along the eastern Adriatic coast, deposited in the Dinaric foreland basin, are characterized by an abundance of larger benthic foraminifera (LBF). Representatives of the Nummulites are abundant in limestones deposited in oligotrophic, euphotic to mesophotic carbonate ramp settings and in deep basin sediments (being redeposited in mass - transport deposits). Nummulite-rich Lutetian to Bartonian sediments occur in the northwestern part of the basin and Bartonian to Priabonian in the SE part. For this study, nummulite tests from 60 thin sections of shallow-water limestones collected in the northern and southern parts of the foreland basin were examined in detail. The foraminiferal tests from the different areas show signs of mechanical, biological, or chemical degradation, which varies greatly depending on the area. The study of Lutetian carbonates from Istria and Northern Adriatic region has shown that 2 to 5% of all Nummulites tests show boring marks. The A– and B– generation representatives were equally affected by bioerosion. The traces are small and randomly distributed holes near to the outer walls. The Nummulites tests of Bartonian – Priabonian (Hvar Is., Pelješac) are more frequently bioeroded, about 10% of all specimens show boring marks, and preferably B-generation specimens are destroyed. Destruction varies from multiple holes of the same size distributed in a line along the test diameter to complete destruction of the internal test structure. There is a kind of size selection of the bioeroders, because the boring marks in the B-generation tests are larger, than those in the A-generation tests. The more intense bioturbation suggests greater biological competition in the middle to outer ramp settings around the Middle Eocene Climate Optimum in this part of the Neotethys. There are several possible causes for this: (i) a slightly higher seawater temperature around the MECO led to a higher occurrence of bioeroders (even the appearance of some new forms, such as the recorded crabs from the eastern Neotethys, Schweitzer et al., 2007), or (ii) a difference in sedimentation rate (burial history) between the two areas, or (iii) the Lutetian LBF assemblages were more resistant to biological destruction?

Schweitzer, C.E., Shirk, A.M., Ćosović, V., Okan, Y., Feldmann, R.M. and Hosgor; I.: New species of Harpactocarcinus from the Tethys Eocene and their paleoecological settings, Journal of Paleontology, 81/5, 1091-1100, 2007.

This study is conducted within the framework of the scientific project IP-2019-04-5775 BREEMECO, funded by the Croatian Scientific Foundation.

How to cite: Ćosović, V., Aljinović, D., Bucković, D., Čančar, M., Felja, I., Galovic, I., Horvat, M., Kurtanjek, D., Pejnović, I., Pezelj, Đ., Tomašić, N., and Coric, S.: Preservation of Nummulites tests in shallow-water limestones regarding the Middle Eocene Climate Optimum (Dinaric foreland basin, Croatia), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2039, https://doi.org/10.5194/egusphere-egu22-2039, 2022.

EGU22-117 | Presentations | SSP1.1

Neoproterozoic geodynamics of South China and implications on the Rodinia configuration: the Kunyang Group revisited

Li Sun, Wei Wang, Guimei Lu, Erkun Xue, Sifang Huang, Manoj K. Pandit, Bin Huang, Xirun Tong, Yang Tian, and Yang Zhang

The late Mesoproterozoic to early Neoproterozoic strata in the Yangtze Block hold a key position in deciphering the tectonic evolution of the South China Block and implicate upon the reconstruction of the Rodinia supercontinent. The sedimentological, geochronologic, and geochemical data on the Kunyang Group, southwestern Yangtze Block, were evaluated for a better understanding of the regional geodynamics and refinement in its paleoposition in the Rodinia supercontinent. Our findings constrain the deposition of the Kunyang Group sediments occurring during 1152 Ma and 1000 Ma, under a stable environment with alternating neritic and littoral facies sedimentation. In contrast, deposition of the Meidang Formation, traditionally thought to represent the upper part of the Kunyang Group, continued up to 866 Ma in an active setting at varying basin depths and hydrodynamic conditions. Moderate to high SiO2 contents (57.7-95.4 wt%), highly variable K2O/Na2O ratios (0.01-55.8), and critical trace element abundances (Zr: 57.6-578 ppm, Th: 1.95-28.3 ppm, Sc: 0.75-24.3 ppm), detrital zircon age distribution, sedimentological characteristics, and bimodal magmatism cumulatively underline a transition from continental rift to passive continental margin setting, followed by an active continental marginsetting. The onset of oceanic subduction below the SW-NW margin of the Yangtze Block caused a hiatus in sedimentation, marked by an unconformity between the Kunyang Group and Meidang Formation.

Paleocurrent data, zircon U-Pb ages, and Lu-Hf isotopic characteristics indicate that the Kunyang Group received detritus from some interior sources and exotic terranes, such as the Gawler Craton in Australia, the Transantarctic Mountains in East Antarctica, and the Ongole domain in the Eastern Dharwar Craton of India. The Yangtze Block was likely located to the west of Australia and East Antarctica and north of India in the Rodinia supercontinent. Paleocurrent data also confirm an external location for the Yangtze Block in the Rodinia paleogeographic configuration.

How to cite: Sun, L., Wang, W., Lu, G., Xue, E., Huang, S., Pandit, M. K., Huang, B., Tong, X., Tian, Y., and Zhang, Y.: Neoproterozoic geodynamics of South China and implications on the Rodinia configuration: the Kunyang Group revisited, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-117, https://doi.org/10.5194/egusphere-egu22-117, 2022.

EGU22-3751 | Presentations | SSP1.1

Active versus arrested silica diagenetic front: Implications on the Palaeoceanographic evolution across the Falkland Plateau

Banafsheh Najjarifarizhendi and Gabriele Uenzelmann-Neben

3300 km of newly collected 2D seismic reflection data across the Falkland Plateau, acquired during cruise MSM81 (2019) allowed for mapping of two distinct bottom-simulating-reflection (BSR) features, which are mostly pronounced within the western and southern sectors of the Falkland Plateau Basin (FPB-BSR) and the eastern sector of the Falkland Trough (FT-BSR). The nature of these BSRs is investigated by means of their reflection characteristics and seismic expressions and is concluded to be associated with silica diagenetic fronts. In absence of a proximal borehole, age information is derived through correlation with the Deep Sea Drilling Project Leg 36 Sites 327 and 330 and Leg 71 Site 511, on the easternmost proximity of the FPB, along the seismic profiles. It is argued in this study, that despite their similar origin, presumably in connection to an Opal A/CT diagenetic front, FPB- and FT-BSR display dissimilar geometrical characters. While the FPB-BSR is by definition a true BSR, which mimics the present seafloor, the geometrical extent of the FT-BSR, which shows parallelism with a shallower buried (Early/Middle Miocene?) reflector, favors a fossilized diagenetic front parallel to a paleo-isotherm. Palaeoceanic and palaeomorphologic implications are brought based on observed depth properties of the BSRs by considering different scenarios for the geothermal gradients. The observations suggest the absence of up to a few hundred meters of sedimentary deposits which presumably have been eroded due to the erosive action of the bottom currents.

How to cite: Najjarifarizhendi, B. and Uenzelmann-Neben, G.: Active versus arrested silica diagenetic front: Implications on the Palaeoceanographic evolution across the Falkland Plateau, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3751, https://doi.org/10.5194/egusphere-egu22-3751, 2022.

EGU22-535 | Presentations | SSP1.1

Recognizing the effect of modern and paleo bottom currents across deep-marine basins: insights from sedimentological and geophysical data across the Western Gap and Josephine Seamount (NE Atlantic)

Zarina Urazmuratova, Leila Bashirova, Liubov Kuleshova, Tatiana Glazkova, Mark Rikhman, Diana Kazakova, and Sara Rodrigues

We present geophysical and sedimentological data acquired during the 59th cruise of the P/V Akademik Ioffe (September – October 2021) from the eastern North Atlantic. Two sediment cores AI-59022 and AI-59027 were recovered southwest of the Western Gap entrance sill (water depth 4872 m) and from the western slope of the Josephine seamount (water depth 3282 m), respectively.  The collected data is valuable for reconstructions of the Pleistocene to Holocene sedimentary record and recognizing the influence of near-bottom currents on sediment deposition in the study areas.

Using high-resolution sub-bottom profiling, sediment waves (up to 50 m in amplitude) were found southwest of the entrance sill of the Western Gap. The presence of ripples and scours north of this sill also indicate elevated bottom current velocities in the gap which is in agreement with direct current velocity measurements (30 cm/s). Given that temperatures of <2 °C, which are characteristic of the AABW (Morozov et al., 2010), were recorded by CTD profiling near the seafloor, it is possible that AABW has played a significant role in shaping the sedimentary and morphological features in the Western Gap.

On the western slope of the Josephine seamount, a contourite drift intercalated with mixed features was identified, characterized by multiple, continuous sub-parallel reflections.  High-resolution sub-bottom profiling has also allowed us to identify a distinct erosional furrow at 1410 m (water depth). The depth of this feature corresponds to the present depth of the Mediterranean Outflow Water and may be related to the erosive passage of MOW currents.

The sponge species Pheronema carpenter was also observed on the western slope of the Josephine seamount. This species is typically associated with areas of high productivity, and possibly with regions of enhanced bottom tidal currents which promote the resuspension of organic matter. Thus, the presence of this sponge indicates elevated near-bottom hydrodynamic activity in the Josephine seamount area.

The dataset across the western slope of the Josephine seamount was supported by an IO RAS state assignment (№0128-2021-0012), whereas the study in the Western Gap was financed by RFBR (№20-08-00246).

How to cite: Urazmuratova, Z., Bashirova, L., Kuleshova, L., Glazkova, T., Rikhman, M., Kazakova, D., and Rodrigues, S.: Recognizing the effect of modern and paleo bottom currents across deep-marine basins: insights from sedimentological and geophysical data across the Western Gap and Josephine Seamount (NE Atlantic), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-535, https://doi.org/10.5194/egusphere-egu22-535, 2022.

EGU22-2958 | Presentations | SSP1.1

Magnetostratigraphy of the Pikermian fauna-bearing late Miocene central Anatolian Sivas Basin (Turkey)

Maud J.M. Meijers, Ferhat Kaya, Ahmet Peynircioglu, Faysal Bibi, Cesur Pehlevan, Andreas Mulch, and Cor G. Langereis

The Pikermian chronofauna is associated with C4 vegetation and the potential hominin Graecopithecus freybergi in Greece and Bulgaria and forms part of the Old World Savannah Paleobiome. This study provides a new magnetostratigraphy for thestratigraphic interval that includes the Haliminhanı and Hayranlı mammal sites from the central Anatolian Sivas Basin (Turkey), which show high faunal similarities to the Pikermian chronofauna.

Dated sites harboring Pikermian fauna in Turkey, Greece, and Bulgaria range in age between 11 and 7.3 Ma. Based on biostratigraphy, the Haliminhanı and Hayranlı fossil horizons were previously placed within European Mammal Neogene (MN) zones MN11-MN12 (ca. 9 to 7 Ma). A new magnetostratigraphy in 140 m thick continental deposits refines the age estimate to 8.0–6.5 Ma for the fossil mammal-bearing levels of the Sivas Basin.

Negative covariance between δ13C and δ18O values of bulk carbonate from the fluvio-lacustrine beds indicates an open lake hydrology; δ13C and δ18O values suggest a positive water balance and no significant long-term changes in hydrology and primary productivity within the lake that once covered the Sivas Basin. Two intervals of increased δ13C (by ca. 6–8‰) within the section are followed by a similar decrease over total time intervals of ca. 150 kyr. An increase of biogenic productivity can increase δ13C in lacustrine carbonate and may either result from changes in nutrient input or temperature. The absence of simultaneous changes in δ18O during peaks in δ13C make temperature an unlikely driver and we therefore conclude that nutrient input adjustments to the basin were responsible for the two peaks in δ13C.

Our results suggest that the Pikermian chronofauna of the Sivas Basin thrived under relatively stable local hydrological and climatic conditions. In the Sivas Basin, the Pikermian fauna flourished well into the Messinian, as opposed to Greek and Bulgarian sites where faunal turnover was observed under a cooling climate and mid-latitude desertification across the Tortonian-Messinian boundary.

Key words magnetostratigraphy, stable isotope geochemistry, mammal stratigraphy, late Miocene, Pikermian, central Anatolia

References Böhme et al. (2017). PLoS ONE, https://doi.org/10.1371/journal.pone.0177347; Böhme et al. (2018). Global and Planetary Change, https://doi.org/10.1016/j.gloplacha.2018.07.019 ; Meijers et al. (2018). Earth and Planetary Science Letters, https://doi.org/10.1016/j.epsl.2018.05.040; Meijers et al. (2020). Geosphere, https://doi.org/10.1130/GES02135.1; Meijers et al. (2022). Newsletters on Stratigraphy, https://doi.org/10.1127/nos/2021/0623

How to cite: Meijers, M. J. M., Kaya, F., Peynircioglu, A., Bibi, F., Pehlevan, C., Mulch, A., and Langereis, C. G.: Magnetostratigraphy of the Pikermian fauna-bearing late Miocene central Anatolian Sivas Basin (Turkey), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2958, https://doi.org/10.5194/egusphere-egu22-2958, 2022.

EGU22-9404 | Presentations | SSP1.1

Stratigraphy, Provenance, and Geodynamic setting of the Lower-Middle Jurassic succession in the Prerif foreland basin (Rif Chain, Morocco)

Hajar Kairouani, Anas Abbassi, Mohamed Najib Zaghloul, and Mohamed El Mourabet

The Rif chain is located on the western edge of the Apennine-Maghrebian Chain. It is classically subdivided into three main superimposed tectonic domains: The Internal, Flysch Basin, and the External domains. The latter regroups three sub-domains: Intrarif, Mesorif, and Prerif. The present work is based on new geological mapping with lithostratigraphic logging and sampling for geochemical analysis from Lower-Middle Jurassic sedimentary successions belonging to the Prerif sub-domain. Four stratigraphic sections have been analyzed (Jbel Zerhoune, Dhar Nsour I and II, and Jbel Outita section). The Lower Jurassic successions are mainly characterized by alternating marls with limestones, bioclastic limestone, and calcareous sandstones, whereas the Middle Jurassic ones are mainly represented by calcareous sandstones and bioclastic limestones, both alternating with marly intervals.

The collected fifteen samples have been examined using Laser Ablation–Inductively Coupled Plasma–Mass Spectrometry (LA-ICP-MS) and X-Ray Fluorescent (XRF) for Elemental geochemical analysis to provide new insights about provenance, source rocks, paleoweathering, mechanical sorting/recycling, and geodynamic setting.

The elemental geochemistry (Major, Trace, and Rare Earth Elements) reveals that major oxides concentrations (SiO2, Al2O3, MgO, and K2O) are relatively close to the Post-Archean Australian Shales (PAAS) except for MnO and Na2O, which show a depletion trend, while Cao and Sr display an enrichment, also Zr, Hf and REEs show low concentrations and indicate weak recycling processes. In order to characterize the provenance, we used a combination of the Cr/V vs. Y/Ni plot, the Cr/Th vs. Th/Sc plot, and the elemental ratios of provenance (La/Sc, Th/Sc, Th/Co, Th/Cr, and Cr/Th). Various discriminant diagrams were used to reveal the paleoweathering intensity, sorting, and maturity of sediment during their source to sink fate. The Chemical Index of Alteration (CIA) shows values varying from 49.09 % to 77.01 %. Th/Sc versus Zr/Sc ratios and the Al2O3-Zr-TiO2 plots have been used to assess the sorting related to the fractionation of sediment during their transport. This is also corroborated by the relatively high values of the compositional variability index (ICV) of Jbel Zerhoune and Dhar Nsour (I and II) and Jbel Outita (ICV<1 and ICV>1, respectively). We also used multidimensional discriminant function diagrams to characterize the geodynamics setting on the analyzed samples.

The main expected results and related interpretations reveal that the provenance of the lower-Middle Jurassic sediments mainly indicates a supply from felsic source rock areas as attested by prevalent enrichment in Sr and probably from a minor mafic supply. The chemical index of alteration indicates a low to moderate degree of source area weathering. The Th/Sc versus Zr/Sc ratios and the Al2O3-Zr-TiO2 recycling plots, and the depletion of Hf and Zr reflect poor mechanical sorting and recycling processes which are confirmed by the high ICV values indicating that almost all samples are immature first-cycle sediments with unweathered detrital minerals. The analyzed sediments have been deposited within a passive margin controlled by a rifting/drifting geodynamic evolution of the northern African margin during the Early-Middle Jurassic.

How to cite: Kairouani, H., Abbassi, A., Zaghloul, M. N., and El Mourabet, M.: Stratigraphy, Provenance, and Geodynamic setting of the Lower-Middle Jurassic succession in the Prerif foreland basin (Rif Chain, Morocco), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9404, https://doi.org/10.5194/egusphere-egu22-9404, 2022.

EGU22-6008 | Presentations | SSP1.1

Toarcian marine vertebrate preservation in the Grands Causses Basin (France)

Brahimsamba Bomou, Guillaume Suan, Jan Schlögl, Anne-Sabine Grosjean, Baptiste Suchéras-Marx, Thierry Adatte, Jorge Spangenberg, Stéphane Fouché, Axelle Zacaï, Corentin Gibert, Jean-Michel Brazier, Vincent Perrier, Peggy Vincent, Kévin Janneau, and Jeremy E. Martin

Several episodes of strong climate change and environmental perturbation marked the Early Jurassic, and culminated during the Toarcian Oceanic Anoxic Event (T-OAE), characterised by widespread deposition of organic-rich shales. Exceptionally preserved fossils of marine vertebrates and invertebrates have been discovered in the Toarcian shales of NW Europe, but the potential links between the occurrences of these exceptionally preserved fossils and the T-OAE remain poorly investigated. Paleontological excavations realized in Toarcian strata near Lodève (Grands Causses Basin, southern France) have yielded several specimens of marine vertebrates and abundant invertebrate fauna. We have developed a multiproxy approach (ammonite biostratigraphy, X-ray diffraction-bulk mineralogy, Rock-Eval pyrolysis, stable isotopes, trace element, phosphorus and mercury contents) to place these findings in a well-defined temporal and paleoenvironmental context, and hence constrain the factors that led to their extraordinary preservation. The Jenkyns Event interval, unambiguously identified at the base of the Toarcian organic-rich shales by a 5‰ negative carbon isotope excursion, records higher mercury fluxes, which suggest a causal link with intense volcanic activity of the Karoo–Ferrar large igneous province. This interval is very condensed and unfossiliferous, and might have been deposited under abnormally low-salinity conditions. Our data exhibit that the deposition of the vertebrate-yielding horizons post-dated the T-OAE by several hundreds of ka, and took place during a prolonged period of widespread oxygen-deficiency and high carbon burial. Our results indicate that the unusual richness in vertebrates of the studied site can be explained by a combination of regional factors such as warming-induced, prolonged seafloor anoxia, and more local factors, such as extreme condensation owing to reduced dilution by carbonate and detrital input.

How to cite: Bomou, B., Suan, G., Schlögl, J., Grosjean, A.-S., Suchéras-Marx, B., Adatte, T., Spangenberg, J., Fouché, S., Zacaï, A., Gibert, C., Brazier, J.-M., Perrier, V., Vincent, P., Janneau, K., and Martin, J. E.: Toarcian marine vertebrate preservation in the Grands Causses Basin (France), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6008, https://doi.org/10.5194/egusphere-egu22-6008, 2022.

EGU22-3697 | Presentations | SSP1.1

Palaeoenvironmental changes in the Moesian Basin (Bulgaria) during the Toarcian

Lubomir Metodiev, Elena Koleva-Rekalova, Milena Georgieva, and Tanya Stoylkova

There is a wide range of data behind the concept that the late Pliensbachian–early Toarcian span (184.5–181.5 Ma) was a time of Earth-scale palaeoenvironmental changes. Rapid global warming, sea-level rise, perturbations in the carbon cycle and the development of widespread anoxia, known as the early Toarcian Oceanic Anoxic Event (T-OAE), are deemed amongst the major biogeochemical disturbances in the Mesozoic. A biotic crisis in the marine realm, with ~30% taxonomic loss, known as the early Toarcian mass extinction (T-ME), was broadly recognized. Many studies linked the T-OAE and the T-ME with the eruption of the Karoo–Ferrar igneous province in the southern hemisphere. The volcanism–warming–anoxia–extinction link has been well established and continues to collect evidence in numerous sites from around the world. The T-OAE has been indicated in several Bulgarian stratigraphic sections to date. The latter represent inner-shelf deposits of the Moesian Basin, which was developed proximal to the southern Eurasian passive continental margin. The overall depositional trend fits into the regressive phase of the second-order Ligurian (R6) T-R cycle, which is widely recognizable in the Jurassic basins of NW Europe. Locally, the deposition took place within a rapid late Pliensbachian–early Toarcian transgression, followed by a gradual regression to the mid-Bajocian times. It is related with widespread condensations and a collapse of the carbonate platform productivity. The manifestations of anoxia have been weak and more enhanced at post-T-OAE levels. Oxygen deficiency was evidenced in narrow and diachronous redox intervals with elevated TOC contents, V/Cr, V/(Ni+V) and Th/U ratios, and smallest mean framboid diameters. The δ13Cbel and δ18Obel profiles showed similar trends to coeval European sections, in having a decline in oxygen-isotope signatures and rising in carbon-isotope values, both of >3‰, around the Pliensbachian/Toarcian (P/T) boundary. A decrease in 87Sr/86Sr ratios through the upper Pliensbachian, reaching a minimum around the P/T boundary, and followed by gradual increase throughout the Toarcian was also recorded. The isotope data revealed an increased freshwater influx and rapid seawater warming. The warming was attributed to the eruption of the Karoo-Ferrar, reflected by enrichments in mercury (Hg) recorded as a shift in sedimentary Hg/TOC ratios and concomitant with the δ13Cbel and δ18Obel excursions. A biotic crisis was recorded amongst the benthic (bivalve and brachiopod) faunas and considered to be part of the T-ME. Both bivalves and brachiopods displayed clear NW European affinity, but characteristic ‘black shale’ taxa are virtually absent. A loss of ~40% of extinct bivalve species was evidenced around the P/T boundary. In brachiopods, the loss is even greater, with a prominent P/T boundary-hiatus and straggling occurrences above it, consisting mainly of autochthonous taxa. In the absence of ‘true’ anoxic setting, the T-OAE–T-ME link remains unclear. Therefore, rapid warming rather than oxygen deficiency has been driving the T-ME in the Moesian Basin.

This account takes part of the National Science Program “Environmental Protection and Reduction of Risks of Adverse Events and Natural Disasters”, approved by the Resolution of the Bulgarian Council of Ministers (No. 577/17.08.2018).

How to cite: Metodiev, L., Koleva-Rekalova, E., Georgieva, M., and Stoylkova, T.: Palaeoenvironmental changes in the Moesian Basin (Bulgaria) during the Toarcian, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3697, https://doi.org/10.5194/egusphere-egu22-3697, 2022.

EGU22-2422 | Presentations | SSP1.1

A flashback to changes across the Cretaceous-Paleogene boundary (K/Pg) in Turkey:  a faunal and environmental portray

A. Uygar Karabeyoglu, Jorge Spangenberg, and Thierry Adatte

EGU22-8704 | Presentations | SSP1.1

Dramatic decline and change in coiling direction of planktic foraminifer Morozovella at the Early Eocene Climatic Optimum (EECO; ~53-49 Ma) from the Pacific Ocean

Giulia Filippi, Valeria Luciani, Roberta D'Onofrio, Thomas Westerhold, Bridget S. Wade, and Gerald R. Dickens

Improved knowledge of the connection between striking variations in the abundance and coiling direction of the trochospiral planktic foraminiferal genus Morozovella and early Eocene carbon-cycle changes, is presented in this study as deriving from new data recorded from the Pacific Ocean (Shatsky Rise, Ocean Drilling Program Sites 1209, 1210). This location spans the Early Eocene Climatic Optimum (EECO; ~53-49 Ma), the interval when Earth surface temperatures and atmospheric pCO2 reached the maximum peak of entire Cenozoic (Zachos et al., 2001, Sciences; Anagnostou et al. 2016, Nature; Inglis et al., 2020 Clim. Past). A significative impact of the EECO on planktic foraminiferal assemblages has recently been recorded in previous works from the Atlantic Ocean, where a definitive marked decline in abundance, diversity, test-size and change in coiling direction of the mixed-layer symbiont-bearing genus Morozovella, took place within the first ~600 kyr of this interval (Luciani et al., 2016 Clim. Past; Luciani et al. 2017 Paleoceanogr.; Luciani et al., 2017 GloPlaCha; D’Onofrio et al., 2020 Geosciences; Luciani et al., 2021 GloPlaCha). As registered in Atlantic sites, in the tropical Pacific Ocean Sites 1209 and 1210, the morozovellids drop permanently their relative abundance at the carbon isotope excursion (CIE) known as J event (~53 Ma), which marks the EECO beginning. A second major change affected all the morphologically defined species of Morozovella (possibly criptic species) at the Atlantic Ocean, resulting in a switch from dominant dextral to sinistrally coiling preference, within ~200 kyr after the K/X event (~52.8 Ma). Although the coiling direction preference of Morozovella at Shatsky Rise changed from dominant dextral to dominant sinistral after the K/X event as well as in the Atlantic sites, here the switch occurred with a delay of ~200 kyr. The recorded modifications clearly reflect important changes in evolution or environment. These changes may include temperature increase and pH decrease that could have reduced the symbiotic relationship and induced calcification crisis. Searching for the driving causes of the observed variations, our data clearly demonstrate their wide geographic and possibly global character and the evident relationship between the environmental perturbations occurred in the mixed-layer at the EECO and the striking changes on planktic foraminiferal assemblages during the first ~800 kyr of this intriguing interval.

How to cite: Filippi, G., Luciani, V., D'Onofrio, R., Westerhold, T., Wade, B. S., and Dickens, G. R.: Dramatic decline and change in coiling direction of planktic foraminifer Morozovella at the Early Eocene Climatic Optimum (EECO; ~53-49 Ma) from the Pacific Ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8704, https://doi.org/10.5194/egusphere-egu22-8704, 2022.

River deltas have long been considered as important carbon sinks. However, the presence of shallow gas (mainly composed of methane) and the processes of delta erosion caused by diminished sediment supply bring complexities to the present situation. This study investigates the response of the gas charged deposits in the Yangtze subaqueous delta to erosion process based on historical bathymetric data and the dataset obtained from a seismic survey. Both seismic and bathymetric data reveal a prominent erosion belt at water depth ranging from 5-20 m, extending from the southwest to the northeast in the nearshore area of the Yangtze subaqueous delta. Erosion is severe in the south while slight in the north area due to the differences in hydrodynamic condition, sediment erodibility and sensitivity to sediment reduction. Seabed erosion reduces the thickness of cap bed, as well as overburden pressure at gas front, making it easier for gas to seep through the sediment column and bypass the process of anerobic oxidation of methane within the SMT (an important methane filter). The spatial coincidence between the shallower gas front and pockmarks also indicates that sea bed erosion accelerates gas seeping activities. It expected more greenhouse gas would be expelled into atmosphere under the impact of bed erosion induced by ongoing decline of riverine sediment supply.

How to cite: Chen, Y., Deng, B., Zhang, W., and Gao, S.: Response of shallow gas charged Holocene deposits in the Yangtze Delta to erosion induced by diminished sediment supply: Increasing greenhouse gas emission, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3993, https://doi.org/10.5194/egusphere-egu22-3993, 2022.

EGU22-9355 | Presentations | SSP1.1

Defining the basic rules that describe long-term shoreface dynamics: A process-mimicking approach for reservoir modelling

Agustín Argüello Scotti, Christian Haug Eide, Ingrid Aarnes, Jacob Skauvold, and Ragnar Hauge

Producing geologically reasonable subsurface reservoir models which also honor wellbore and seismic data is still a major challenge for geoscientists at a range of energy and mining industries. Models based purely on geostatistics usually don’t satisfy the expected representation of geological concepts, while process-based models can hardly be constrained by subsurface data. Our research project GEOPARD aims to add a new tool in this context by providing a process-mimicking approach. In this method, sedimentary units are placed in 3D space constrained by subsurface data while simultaneously following a set of geological rules. This contribution aims to share and discuss the methodological workflow under development, from the geological domain, to test this method on the shoreface accumulation system. The first major step of the workflow is to specify the geological unit(s) to be modelled, which must be of interest as a control upon reservoir heterogeneity and of an adequate scale for representation. Afterwards, geological rules can be defined. These can be classified as (i) element geometry, scale, and infill specifications, (ii) basic element-set rules, which define the expected relationship between a set of geological units, and (iii) advanced element-set rules, which define how these relationship between elements might change over a sedimentary sequence. Each set of rules is linked to appropriate references for justification and exemplified from virtual outcrops of the Blackhawk Formation at Central Utah, which is one of the most studied and best-preserved examples of this type of depositional system. Feedback from the modelling domain is itself incorporated into refining the geological rules, resulting in an iterative effort to improve the methodology. Testing the method in these type of accumulation systems, that can be said to follow relatively straight-forward rules, are key before advancing into systems which typically exhibit more complex sedimentary architecture. We expect that the development of this modelling method can be a powerful tool to produce more useful models for oilfield assessment and development, CO2 storage projects, hydrocarbon exploration, among many others.

How to cite: Argüello Scotti, A., Haug Eide, C., Aarnes, I., Skauvold, J., and Hauge, R.: Defining the basic rules that describe long-term shoreface dynamics: A process-mimicking approach for reservoir modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9355, https://doi.org/10.5194/egusphere-egu22-9355, 2022.

EGU22-6404 | Presentations | SSP1.1

Composition and accumulation conditions of the Belokatay Formation of the Lower Permian (Middle Urals)

Ekaterina Volodina, Alexandr Tevelev, Alexandra Borisenko, and Egor Koptev

Introduction. Deposits of the Belokatay Formation were studied in four quarries in Belyanka region and Kirikeevo region (Belokataisky District, Bashkortostan). All of these careers are quite similar to each other. The Belokatay Formation is represented by polymictic conglomerates with rare layers of fine-medium-grained polymictic sandstones. The composition of the pebbles is extremely diverse - there are fragments of all types of rocks - sedimentary (70%), magmatic (20%), metamorphic (10%). Sedimentary rocks: pelitomorphic limestones, fragments of coral reefs and organogenic-detrital limestones. Igneous rocks - basaltoids and granitoids. Metamorphic rocks - shales, gneisses, quartzites. The roundness of all the pebbles is very good, there are no angular fragments. The size: more than 70% of fragments – 5-10 cm, which accords to a medium-grained conglomerate (although rare boulders, as well as smaller pebbles, are also sometimes found).

Materials and methods. We analyzed thinsections of matrix rocks and individual fragments in the amount of 60 pieces, identified foraminifera from pebbles of organogenic limestones, and also examined some samples for the presence of conodonts and other fauna.

Results and discussion. The diversity of the composition of the fragments, their consistent size and good roundness, as well as their high thickness (more than 700 meters) indicate that the formation accumulated in a very active hydrodynamic environment. In literary sources, faults are reported - but they were not found on our territory. On the other hand, in the conglomerates vertically layers of sandstones were found. Perhaps these are not layers, but olistoplaks from older formations. However, olistoplaks, as well as faults, only confirms a very active environment. The main source of material for this formation was the Ural Orogen located to the east of the trough. When the mountains were uplifting, fragments of rocks of different formations were demolished into this basin. And not only the rocks of the orogen could be eroded, but also the sediments, which filled the trough earlier (Late Carboniferous-Permian). The formation of sediments of the Ural foredeep has certain patterns: from the bottom up the section, there is an alternation of coarse-grained rocks (including the Belokatay Formation) and fine-rhythmic flysch strata. The formation of Ural foredeep occurs simultaneously with the collision. There are several stages in this process. The accumulation of the Belokaty Formation characterizes the beginning of one of the stages of collision, as the rocks change – from flysch to conglomerates.

Financial support. The research has been funded by RFBR and CNF as a part of the research project № 19-55-26009 Czechia_a

How to cite: Volodina, E., Tevelev, A., Borisenko, A., and Koptev, E.: Composition and accumulation conditions of the Belokatay Formation of the Lower Permian (Middle Urals), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6404, https://doi.org/10.5194/egusphere-egu22-6404, 2022.

Gamma ray logs are most useful in identifying subsurface lithology and interpreting depositional environments. This study highlights the use of outcrop gamma-ray logs along with outcrop observations and total organic carbon (TOC) analysis to provide the stratigraphic framework of the organic-rich rocks of Huai Hin Lat Formation in central Thailand. The study reveals five sedimentary facies including (1) structureless sandstone, (2) structured sandstone, (3) interbedded sandstone and siltstone, (4) interbedded mudstone and siltstone and (5) calcareous mudstone. These facies can be grouped into two facies associations; mudstone-dominated and sandstone-dominated facies associations. The depositional environment was interpreted as lacustrine basin- fill subdivided into deep lacustrine environment and sublacustrine fan associated with the turbidity currents. The total gamma-log characteristics are closely related to the lithologies controlled primarily by clay mineral compositions. Whist, the use of spectral gamma-ray can reveal more details on depositional environments and conditions. In this study, uranium (U) concentrations is proven to be useful in highlighting organic-rich rocks in low potassium (K) and thorium (Th) concentration successions due to its ability to be fixed in clay minerals and organic materials under an anoxic condition. Thus, the U spectral gamma ray is suggested to combine with conventional gamma ray log for depositional environment and recognition of organic-rich rocks.

How to cite: Phujareanchaiwon, C., Chenrai, P., and Laitrakull, K.: Interpretation and Reconstruction of Depositional Environment and Petroleum Source Rock Using Outcrop Gamma-ray Log Spectrometry From the Huai Hin Lat Formation, Thailand, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1519, https://doi.org/10.5194/egusphere-egu22-1519, 2022.

EGU22-4605 | Presentations | SSP1.1

Harmonisation of Opalinus Clay descriptions in Northern Switzerland: towards a uniform Subfacies Classification Scheme

Géraldine Zimmerli, Bruno Lauper, Gaudenz Deplazes, David Jaeggi, Stephan Wohlwend, and Anneleen Foubert

The Opalinus Clay, an argillaceous to silty claystone formation, is known in Switzerland as being the selected host rock for deep geological disposal of high-, intermediate- and low-level radioactive waste. Since the 1990s, various properties of the Opalinus Clay have been studied within the framework of the Nagra (National Cooperative for the Disposal of Radioactive Waste) deep drilling campaigns and the Mont Terri Project (international research program dedicated to the investigation of claystone). The Opalinus Clay succession was deposited during the Late Toarcian to Early Aalenian in an epicontinental sea covering central Europe.

Although the Opalinus Clay is relatively homogeneous at formation-scale compared to other Mesozoic formations in northern Switzerland, significant lithological variations occur at lower scales. Besides m-scale lithofacies variations, high, intra-facies lithological variability occur at dm- to cm-scale. The facies diversity is primary attributed to regional differences in depositional, environmental and diagenetic conditions. In order to harmonize petrographic descriptions in an objective and quantitative way within all fields of research related to the Opalinus Clay, a subfacies classification scheme has been developed (SF1 to SF5, applied mostly on Mont Terri drill cores). The subfacies are distinguished by parameters such as texture (grain size, bedding, fabric and colour) and composition (nature and mineralogy of components). The five subfacies types can be further refined by additional attributes and sedimentary characteristics (biogenic, diagenetic, structural).

Subfacies descriptions are crucial to understand the lateral and vertical facies variability at regional scale. Moreover, accurate petrographic descriptions are a crucial prerequisite to many geotechnical studies and the prediction of petrophysical properties.

The main goal of the present study is to define a subfacies classification model covering the entire Opalinus Clay succession of the Mont Terri rock laboratory and successions deposited further to the east. Nagra is currently investigating three potential sites for radioactive waste storage within the Opalinus Clay in northern Switzerland. Nine new drill cores are used to apply the subfacies classification scheme. If necessary, the subfacies classification scheme will be adapted considering regional facies heterogeneities. Based on the new subfacies classification, depositional models for the Opalinus Clay will be refined.

How to cite: Zimmerli, G., Lauper, B., Deplazes, G., Jaeggi, D., Wohlwend, S., and Foubert, A.: Harmonisation of Opalinus Clay descriptions in Northern Switzerland: towards a uniform Subfacies Classification Scheme, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4605, https://doi.org/10.5194/egusphere-egu22-4605, 2022.

EGU22-9638 | Presentations | SSP1.1

The identity of the Chicxulub impactor: KPg ejecta-encapsulated meteoric fragments

Phillip Manning, Robert DePalma, Florentin Maurrasse, David Burnham, Loren Gurche, Jeremy Klingler, Peter Larson, Thomas Beasley, Anton Oleinik, Tina Geraki, Konstantin Ignatyev, Victoria Egerton, and Roy Wogelius

The Cretaceous-Paleogene (KPg) boundary is demarked by two critical and intimately linked events: a global-scale impact caused by a massive extraterrestrial body, and a resultant catastrophic planet-wide mass-extinction, with pivotal long-term consequences for life on Earth. The site of impact has been identified as the ~180 km wide Chicxulub crater complex [Yucatan peninsula, Mexico] based on strong geochemical, sedimentological, and temporal evidence. However, the impactor, which was obliterated on contact during the cratering process, has eluded identification. Previous studies struggled to identify the projectile based on scant geochemical and isotopic traces admixed with the ejecta and melt-rock, plus a single heavily altered microscopic fragment possibly from the impactor. While those efforts helped to rule out some potential sources and narrowed down the best potential candidates to a CM, CR, or CO carbonaceous chondrite, the data was insufficient to provide an incontrovertible diagnosis, and the identity of the Chicxulub projectile remained a critical missing detail. Here we describe new, exceptionally-preserved fragments of cosmic origin that were directly associated with Chicxulub impact ejecta from a temporally constrained KPg boundary site in North Dakota (U.S.A.). The fragments occur as inclusions within unaltered glassy ejecta spherules, which likely protected them against chemical and physical degradation, leading to their marked preservation. The spherules themselves were also uniquely preserved in amber, which inhibited their usual breakdown to smectitic clay. Geochemical examination of the inclusions were undertaken using electron microprobe, laser-ablation inductively-coupled-plasma-mass-spectroscopy, and synchrotron X-ray techniques. Results provide multiple lines of evidence that support a cosmic origin and chemistry indicative of a CM subtype carbonaceous chondrite, offering new support of prior hypotheses. The data is also in agreement with projectile residues from the Chicxulub impact fallout. In addition to its utility in reconstructing the dynamics of the Chicxulub event, this data helps provide extra dimension to our understanding of major impact processes and their effects on Earth.

How to cite: Manning, P., DePalma, R., Maurrasse, F., Burnham, D., Gurche, L., Klingler, J., Larson, P., Beasley, T., Oleinik, A., Geraki, T., Ignatyev, K., Egerton, V., and Wogelius, R.: The identity of the Chicxulub impactor: KPg ejecta-encapsulated meteoric fragments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9638, https://doi.org/10.5194/egusphere-egu22-9638, 2022.

Combined with a series of analysis and test data such as seismic, core, drilling, logging and carbon oxygen isotope, this paper analyzes the reservoir differences of the East Zone, middle zone and West zone of the third member of Liushagangzu in the steep slope zone of Weixinan Sag, Beibuwan Basin, analyzes the main reservoir controlling factors of the three zones, and summarizes the reservoir development model. In the study area , reservoir diversity is mainly affected by five factors; 1) Structural factors: structural factors control trap types. In the study area , West zone and middle zone fans mainly develop glutenite deposits controlled by linear provenance, and structural traps are developed; The East zone mainly develop glutenite deposits controlled by point provenance, and lithologic traps are developed. 2) Sedimentary facies factors: sedimentary facies types control reservoir characteristics. Fan delta sedimentary system is developed in the three zones in the study area. The main dominant sedimentary microfacies are underwater distributary channel, with large sand body thickness, low matrix and cement content The main characteristics are the development of primary and secondary pores. 3) Sand thickness factors: sandstone thickness mainly controls the oil and gas bearing property of the reservoir. Taking the oil and gas bearing property of 50% as the boundary, the sand thickness of the West Zone in the study area is 3m; The sand thickness of the middle zone is 5m; The sand thickness of the East Zone is 8m; 4) Physical factors: physical factors mainly control reservoir classification. In the study area ,type I conventional reservoirs (porosity > 12%, permeability > 10md) are mainly developed in the West Zone; middle zone mainly develops type II low permeability reservoir (porosity 6-12%, permeability 1-10md); West Zone mainly develops type III tight reservoir (porosity < 6%, permeability < 1md) 5) Diagenetic facies factors: diagenetic facies factors control the reservoir type. In the study area, West Zone mainly develops weakly compacted and weakly cemented diagenetic facies (type I diagenetic facies); middle zone mainly develops medium compaction medium dissolution and strong compaction medium strong dissolution diagenetic facies; East Zone mainly develops strong compaction medium strong dissolution diagenetic facies. Combined with reservoir control factors and reservoir differences in steep slope zone, two types of multi-factor control reservoir prediction models are summarized: steep slope zone prediction model and conversion zone prediction model. The high-quality reservoir in the steep slope zone is mainly in the middle of the sand body, mainly medium coarse sandstone. The organic acid + atmospheric fresh water two-stage acid fluid is active, the dissolution is strong, and the dissolved substances migrate out of the system. The intergranular dissolved pores, intragranular dissolved pores and matrix dissolved pores are developed, and the physical properties are the best. The high-quality reservoirs in the conversion zone are mainly located in the middle of the sand body, mainly medium coarse sandstone, dissolved by organic acid fluid, developed intergranular dissolved pores, intragranular dissolved pores and matrix dissolved pores, and have the best physical properties.

How to cite: liu, S.: Study on Reservoir Diversity Controlled by Multiple Factors:Anexample from Liushagangzu 3rd member of Northern Steep SlopeZone in Weixinan Depression ,Beibuwan Basin, South China Sea , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4941, https://doi.org/10.5194/egusphere-egu22-4941, 2022.

EGU22-3705 | Presentations | SSP1.1

Fluid features during hydrocarbon generation and expulsion from laminated source rocks

Miao Wang, Yong Chen, and Steele-MacInnis Matthew

Bed-parallel, fibrous calcite veins are widespread within Eocene, lacustrine, laminated organic-rich source rocks in the Dongying Depression of Bohai Bay Basin, East China. Such veins mainly occur in the horizontal organic-rich laminae (composed of horizontal banded lamalginites) of mature source rocks, with higher TOC and lower carbonate contents than the adjacent non-vein sections vertically. They are products of diagenesis accompanying burial, and their formation was coeval with hydrocarbon generation and expulsion from the initial fracture opening and subsequent dilation, which was evinced by the occurrence of medium plane (calcite+bitumen) and primary hydrocarbon inclusions in the fibrous calcites. Petrographically primary two-phase (oil+gas) hydrocarbon inclusions, and coeval aqueous inclusions are distributed either within individual fibrous calcite grains or between two adjacent fibres. In rare cases, inclusions with only liquid hydrocarbons were observation. The hydrocarbon liquid shows various UV-fluorescence colours (brownish, yellow, yellow-green, green), indicating different composition of oil from less mature to relatively high maturity. The micro-spectrofluorimetry of yellow-green fluid inclusions contains the two dramatic peaks (511 nm and 568 nm) of yellow and green fluorescence, suggesting that it was the by-product by fractionation. In addition, many bitumen-bearing oil inclusions could also be observed in the fibrous calcite veins. Consequently, we surmise that immiscibility and heterogeneous trapping of liquid hydrocarbon, bitumen and aqueous solution during the fibrous calcite growth are the best explanation for these above features. The PVT calculation by use of isochores intersection of oil inclusions and aqueous inclusions, combined with study of the burial history show that veins were formed during the Oligocene Dongying sedimentary stage (32.8-24.6Ma). We conclude the fluid overpressure up to approximately twice (2x) the hydrostatic value (i.e., ~0.5–0.6x lithostatic) are the most common during the hydrocarbon generation and primary migration. The highest degrees of overpressure are recorded by the rare monophase petroleum inclusions. The resulting isochores of these highest density inclusions project to pressures that overlap with the lithostatic gradient. Thus, we contend that vein dilation in the absence of lithostatic fluid pressure suggested a primarily steady-state process, in which dilation was accommodated and offset by concomitant narrowing of the adjacent wall rock laminae. And this process was likely driven by dissolution of CaCO3 from adjacent wall rocks, coupled with the later reprecipitation of calcite into the nascent horizontal fractures.

How to cite: Wang, M., Chen, Y., and Matthew, S.-M.: Fluid features during hydrocarbon generation and expulsion from laminated source rocks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3705, https://doi.org/10.5194/egusphere-egu22-3705, 2022.

The Yinggehai Basin (YGHB) and Qiongdongnan Basin (QDNB) has received a large amount of terrigenous sediment from different continental blocks since the Paleogene, preserving Cenozoic sedimentary records of the Tibetan Plateau uplift, the tectonic activity of the adjacent plate, and climate change in Southeast Asia. Large scale of oil and gas reservoirs have been discovered in the YGHB and QDNB recently, but the provenance of the marine sediments in this area are poorly understood. In this study, sandstone samples were taken from drilling cores in the joint area of YGHB and QDNB, and cover all Oligocene, Miocene and Pliocene formations. The trace element, rare earth element (REE) and detrital zircon U-Pb geochronology of sedimentary rocks from the Oligocene to Pliocene is examined in this study to investigate the temporal and spatial variations in provenance since the early Oligocene. The Red River has been supplying sediments with positive Eu anomalies from basic-ultrabasic metamorphic and volcanic parent rocks to most parts of two basins, while Hainan Island has delivered sediments with negative Eu anomalies from granitic and sedimentary parent rocks to the eastern slope area of YGHB. The U-Pb ages of detrital zircon range from 3000 to 30 Ma, suggesting that sediment input is derived from multiple sources. Importantly, the Upper Oligocene Formation contained exclusively Cenozoic, Mesozoic, Palaeozoic, and Proterozoic zircon ages, and the age spectrum showed two major peaks at ca. 245 and 423 Ma, indicates that Upper Oligocene sediments in the northwestern area of the QDNB may have originated from the Red River, which had four major peaks at 254, 418, 751, and 1848 Ma, suggesting that sediments from the Red River entered the QDNB as early as the Late Oligocene. Detailed analyses of these components indicate that both the Red River and Hainan are likely the major sources of the sediments in the two basins, with additional minor contributions from Central Vietnam.

How to cite: meng, F.: Linking source and sink: geochemistry and zircon U-Pb geochronology provenance record of drainage systems in potential provenance area and Yinggehai-Qiongdongnan Basin, South China Sea, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1780, https://doi.org/10.5194/egusphere-egu22-1780, 2022.

The caves and palaeocaves from the Cradle of Humankind (Cradle), South Africa preserve a rich fossil record of early hominin evolution representing at least three genera: (Australopithecus, Paranthropus, early Homo) and have consequently been the subject of much research. Direct dating of the South African caves had long been hampered by the perception the sedimentary fills are not amenable to direct radiometric dating. The last decade has, however, seen major advances in the ability to reliably date the fossil sites. While some dating methods have been applied directly to fossils and their encasing sediments, the most precise and consistent results come from uranium lead (U-Pb) dating of cave carbonates, known as flowstones and a relatively large dataset places the cave deposits and fossils between 3 and 1.5 Ma. Coupled with the dating issues, there is a second, long held view that the stratigraphy of these sites is too complex and, in many cases, unresolvable. However, coupled with the advances in direct dating the flowstones, there has been a considerable change in understanding of the depositional setting and stratigraphy of these ancient caves. Here we present a model to demystify the stratigraphy and sedimentology of the cave deposits and offer a set of facies which can be applied, in modified site-by-site basis, at all the fossil localities throughout the Cradle. Sedimentary facies vary laterally, depending on the distance from the cave entrance, with entrance facies characterised by coarse-grained material, even piles of boulders. Hydrodynamic sorting winnows finer material and bone into the deeper reaches of the cave resulting in red-brown layered or massive sediments. These clastic sediments are almost all externally derived, and in our model are correlated to times during which the cave entrances are more open; we argue these time windows correlate to a drier external hydroclimate. The stacked occurrence of flowstones and these clastic sediments point to these conditions, both how open the caves are and the general climate state, have oscillated repeatedly in the past. The U-Pb flowstone chronology pins the flowstones and their deposition to specific time windows and investigations into the bigger climatic picture are ongoing. This has the potential to provide a detailed palaeoenvironmental context for the rich early human fossil record, as well as provide otherwise rare southern hemisphere terrestrial records of hydroclimate variability.

How to cite: Edwards, T. and Pickering, R.: A simple sedimentological model demystifying the complexity of fossil bearing cave deposits in the Cradle of Humankind, South Africa., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6299, https://doi.org/10.5194/egusphere-egu22-6299, 2022.

EGU22-6973 | Presentations | SSP1.1

An interdisciplinary approach for reconstructing environmental evolution since the mid Holocene, in Agia (Lemnos Island, Greece)

Nikolaos Theocharidis, Olga Koukousioura, Katerina Kouli, Myrsini Gkouma, Elina Aidona, Georgios Syrides, and Nikos Efstratiou

Lemnos Island (NE Aegean Sea) was inhabited since the Paleolithic times, as is suggested by archaeological evidence from the hunting campsite of Ouriakos (~12.000 BP). The Agia Bay, in the vicinity of Ouriakos site, is located on the southeastern coast of Lemnos Island. The coastal area today is characterized by aeolian sandy deposits (dunes), while a small river is discharging in the bay. The systematic investigation of a 15.5-m long sediment core from the coastal plain of Agia aims to set light to the paleoenvironmental evolution of the area. The exhaustive study of the faunal and floral remains of the deposits, including benthic foraminifera, ostracoda, molluscs, pollen and NPPs was further supported by sedimentological, micromorphological and elemental analyses, magnetic susceptibility measurements and radiocarbon dating.

Four main evolutionary stages are identified: (1) at the base of the sequence the fluvial activity is dominating the sedimentation in the area, while progressively seawater intrusions are observed as suggested by reworked marine foraminifera and mollusc specimens (2) before ~7000 BP a restricted fresh water wetland is formed, characterized by land snails, Cyperaceae and the presence of aquatic plant seeds (3) after ~7000 and until ~5000 BP a connection of the wetland to communication to the sea is established as indicated by the occurrence of euryhaline foraminifera (Ammonia tepida, Haynesina germanica), ostracoda (Cyprideis torosa, Cyprinotus salinus) and mollusc (Cerastoderma glaucum, Abra sp., Hydrobia sp.) assemblages accompanied by marine dinoflagellate cysts and charophytes (4) after ~5000 BP a nearshore environment is developed due the sea-level rise, characterized by Peneroplis pertusus, rotaliids and miliolids as well as Loxoconcha sp., Cerithium sp. and reworked foraminifera and mollusc specimens. Pollen assemblages record the occurrence of mixed deciduous oak forest with Ulmus and Carpinus/Ostrya in the island interior, while agricultural activities are inferred by pollen indicator species.

How to cite: Theocharidis, N., Koukousioura, O., Kouli, K., Gkouma, M., Aidona, E., Syrides, G., and Efstratiou, N.: An interdisciplinary approach for reconstructing environmental evolution since the mid Holocene, in Agia (Lemnos Island, Greece), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6973, https://doi.org/10.5194/egusphere-egu22-6973, 2022.

SSP1.2 – Achievements and perspectives in scientific ocean and continental drilling

EGU22-1509 | Presentations | SSP1.2 | Highlight

A Campaign of Scientific Drilling for Monsoon Exploration in the Asian Marginal Seas

Peter Clift, Christian Betzler, Steven Clemens, Beth Christensen, Gregor Eberli, Christian France-Lanord, Stephen Gallagher, Ann Holbourn, Wolfgang Kuhnt, Richard Murray, Yair Rosenthal, Ryuji Tada, and Shiming Wan

International Ocean Discovery Program (IODP) conducted a series of expeditions between 2014 and 2016 that were designed to address the development of monsoon climate systems in Asia and Australia. Significant progress was made in recovering Neogene sections spanning the region from the Arabian Sea to the Japan Sea and south to western Australia. High recovery by advanced piston core (APC) technology has provided a host of semi-continuous sections that have been used to examine monsoonal evolution. Use of half APC was successful in sampling sand-rich sediment in Indian Ocean submarine fans. The records show that humidity and seasonality developed diachronously across the region, although most regions show drying since the middle Miocene and especially since ~4 Ma, likely linked to global cooling. The transition from C3 to C4 vegetation often accompanied the drying, but may be more linked to global cooling. Western Australia, and possibly southern China diverge from the general trend in becoming wetter during the late Miocene, with the Australian monsoon being more affected by the Indonesian Throughflow, while the Asian Monsoon is tied more to the rising Himalaya in South Asia and to the Tibetan Plateau in East Asia. The monsoon shows sensitivity to orbital forcing, with many regions having a weaker summer monsoon during times of Northern Hemispheric Glaciation. Stronger monsoons are associated with faster continental erosion, but not weathering intensity, which either shows no trend or decreasing strength since the middle Miocene in Asia. Marine productivity proxies and terrestrial environmental proxies are often seen to diverge. Future work on the almost unknown Paleogene is highlighted, as well as the potential of carbonate platforms as archives of paleoceanographic conditions.

How to cite: Clift, P., Betzler, C., Clemens, S., Christensen, B., Eberli, G., France-Lanord, C., Gallagher, S., Holbourn, A., Kuhnt, W., Murray, R., Rosenthal, Y., Tada, R., and Wan, S.: A Campaign of Scientific Drilling for Monsoon Exploration in the Asian Marginal Seas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1509, https://doi.org/10.5194/egusphere-egu22-1509, 2022.

Together with amphibole and garnet, epidote-group minerals are one of the three most important heavy minerals found in orogenic sediments (Garzanti and Andò, 2007). Their chemical composition and optical properties vary markedly with temperature and pressure conditions, and thus provide useful information in provenance analysis on the metamorphic grade of source rocks.

The aim of this study is to devise an efficient and quick method, with micrometric resolution to distinguish among the different species of the epidote group during routine point-counting of heavy-mineral slides, which can be applied on a vast ranges of grain-sizes from fine silt to medium sand.

The geochemical variability of epidote-supergroup minerals from different source rock collected in different sectors of the Alpine orogenic belt was first investigated by coupling Raman Spectroscopy, Scanning Electron Microscopy, and Energy-dispersed X-ray Spectroscopy (SEM-EDS). The geochemical composition, optical properties, and Raman fingerprints of these standard epidote grains were described and in-house database of Raman spectra was created, combining geochemical data and Raman response in the low wavenumbers region and OH stretching bands. A program, written in Matlab® language, has been established which allows to obtain a quick estimate of the amount of iron from the Raman spectra in the clinozoisite-epidote series.

Raman spectra of detrital epidotes contained in turbiditic sediments of the Bengal Fan (IODP Expedition 354) were next compared with Raman spectra of epidote-group standards to determine their composition. The identification and relative amount of detrital epidote, clinozoisite and zoisite in silt- and sand-sized deep-sea sediments contribute to constrain the metamorphic grade of Himalayan source rocks, reconstruct the erosional evolution of the Himalayan orogen, and provide information on climate change and strengthening of the Indian Ocean monsoon throughout the Neogene and Quaternary.

Key words: epidote, provenance, Himalaya, Raman spectroscopy, Microprobe analyses, optical microscope.

Garzanti, E., Andò S., 2007. Plate tectonics and heavy-mineral suites of modern sands. In: Mange, M.A., Wright, D.T. (Eds.), Heavy Minerals in Use, Developments in Sedimentology Series, 58. Elsevier, Amsterdam, pp. 741-763.

How to cite: Limonta, M., Andò, S., Bersani, D., France-Lanord, C., and Garzanti, E.: Raman identification of epidote-group minerals in turbiditic sediments from the Bengal Fan (IODP Exp. 354): a complementary tool to better constrain metamorphic grade of source rocks., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6161, https://doi.org/10.5194/egusphere-egu22-6161, 2022.

EGU22-8339 | Presentations | SSP1.2

How was the Bushveld Complex assembled? A search for cryptic layering in ICDP drillcores from the Main Zone

Robert B. Trumbull, Ilya V. Veksler, Wilhelm Nikonov, and Dieter Rammlmair

The Main Zone of the Bushveld Complex in South Africa is the most voluminous but least studied part of the world’s largest igneous intrusion. Modal layering is poorly developed compared with the units above and below (Upper and Critical Zones, resp.), and most of the ca. 3000 meter-thick Main Zone consists of monotonous gabbronorite, occasionally grading into norite and anorthosite. An exception is the ultramafic “Pyroxenite Marker” near the top of the Main Zone, which is present regionally in the complex and represents a major event of magma recharge into the chamber. However, studies of drillcore through the Main Zone in the Bushveld Northern limb (Ashwal et al., 2005; Hayes et al., 2017) found evidence for layering by periodic variations in rock density at vertical length-scales of 40 to 170 m. This implies there were many more episodes of magma recharge than previously thought.

Our study in the Eastern Limb of the complex tests if cryptic layering in the Main Zone is a local phenomenon or is regionally developed like the Pyroxenite Marker. The first step, reported here, was a vertical profile of bulk density data (Archimedes method) for a 1450 m section of the upper Main Zone below the Pyroxenite Marker. Samples were taken at 1 to 5 m intervals and the results show several intervals of density variations at length-scales of 30 to 120 m, comparable to those previously described in the Northern Limb. Periodicity in density changes is not so well developed as in the earlier study, and we identified several 50 to 75 m intervals where density variations are below 0.05 g/cm3. The second step of the study will use multispectral and laser-induced breakdown spectroscopy (LIBS) scanning to provide modal mineralogy profiles of the same drillcore samples used for density measurement. After cryptic modal layering is documented in this way, follow-up petrologic-geochemical studies at the layer boundaries will aim to characterize the composition and temperature of the magmas involved.

For this project the Bushveld Complex Drilling Project (BVDP) provided access to the BH7771 borehole, donated by Impala Platinum’s Marula mine.

References:

Ashwal, L..D., Webb, S.J. and Knoper, M.W. (2005) S. Afr. Jour. Geol., 108, 199-232.

Hayes, B., Ashwal, L.D., Webb, S.J. and Bybee, G.M. (2017) Contrib. Mineral. Petrol., 172, 13.

How to cite: Trumbull, R. B., Veksler, I. V., Nikonov, W., and Rammlmair, D.: How was the Bushveld Complex assembled? A search for cryptic layering in ICDP drillcores from the Main Zone, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8339, https://doi.org/10.5194/egusphere-egu22-8339, 2022.

A 6-meter drill core from Merensky Reef, Bushveld Complex, South Africa, was scanned in detail with a drill core scanner based on Laser Induced Breakdown Spectroscopy (LIBS). The purpose of the investigation was to visualize variations in the chemical composition along the core, and following a mineral classification of the LIBS data, of variations in the mineral chemical composition, e.g. of Fe/Mg, Cr/Al, and Ca/Na ratios, as well.

The LIBS technology is based on atomic emission spectroscopy, in which the excitation of the atomic species occurs in-situ on the sample surface. The excitation source was a pulsed 50 mJ 1064 nm Nd:YAG laser, and the emitted light was collected with a high-resolution wide-range echelle spectrograph with CCD detector. This approach for measuring mineral chemical ratios such as Mg/Fe, Cr/Al, and Ca/Na, is based on the strength of LIBS in detecting chemical variations using intensity ratios within a single matrix, which in this application is one single particular type of mineral phase. For validation purposes, selected samples were analysed with bulk chemical analysis and electron probe microanalysis as well.

Distinct trends could indeed be extracted from the 6 m core section through the Merensky Reef. From a saw-cut core surface without further preparation, a continuous record could be extracted consisting of Mg/Fe of orthopyroxene, Ca/Na of plagioclase, bulk chemical patterns, modal composition, and direct neighbourhood. The data can be used to highlight the presence of unusual patterns and to relate them to Ni, Cu, PGE or other mineralization. When applied to different core sections, it may become an important tool for comparing lateral variability of diagnostic horizons in vertical sequences in layered intrusions such as Merensky Reef and UG-2.

How to cite: Meima, J., Rammlmair, D., Junge, M., and Nikonow, W.: Continuous measurement of Mg/Fe and Ca/Na ratios with scanning Laser Induced Breakdown Spectroscopy in 6 meter of drill core through Merensky Reef, Bushveld Complex, South Africa , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7513, https://doi.org/10.5194/egusphere-egu22-7513, 2022.

EGU22-3372 | Presentations | SSP1.2

Re–Os geochemistry of altered dacitic rock at Site U1527, IODP Expedition 376: Implications for the Re cycle in intraoceanic arcs

Mizuki Ishida, Tatsuo Nozaki, Yutaro Takaya, Junichiro Ohta, Qing Chang, Jun-Ichi Kimura, Kentaro Nakamura, and Yasuhiro Kato

The Re–Os isotopic system is a powerful tool for both geochronology and tracing various geochemical processes. Because the Os isotopic ratio (187Os/188Os) distinctly differs between modern seawater (∼1.06) and hydrothermal fluid (∼0.13), the Re–Os isotopic system is potentially a sensitive tracer of subseafloor fluid flow and the release or uptake of hydrogenous/magmatic Re and Os. The effect of alteration on the Re–Os budget in oceanic crust has been examined for mid-ocean ridge basalt (MORB) and lower oceanic crustal gabbro. In contrast, applications of the Re–Os system in intraoceanic arc settings are limited mainly to fresh igneous rocks; the role of hydrothermal alteration has not yet been examined.

Here, we provide a depth profile of Re–Os geochemistry at Site U1527, located on the NW caldera rim of the Brothers volcano hydrothermal field in the Kermadec arc, which was drilled during International Ocean Discovery Program (IODP) Expedition 376 in 2018. Volcaniclastic rocks from Hole U1527C that had experienced various degrees of high- and low-temperature hydrothermal alteration were analyzed for bulk chemical composition as well as Re–Os concentrations and isotopes. The concentration of Re varied from 0.172 to 18.7 ppb, and that of Os ranges from 9.7 to 147.1 ppt. Hydrothermal alteration usually resulted in the Re uptake by rocks, but a part of Re was released into the ocean by later oxidative weathering. Compared with Re, Os mobility resulting from hydrothermal alteration was limited. Before alteration, our samples likely had homogenous 187Os/188Os of between 0.13 and 0.14, whereas alteration added hydrogenous Os to some drill core sections in two different ways. Elevated 187Os/188Os with Ba enrichment and abundant pyrite occurrence suggests Os precipitation induced by subseafloor mixing of seawater and high-temperature hydrothermal fluid. The highest Re and Os concentrations at Hole U1527C, found in the same interval, were associated with high concentrations of Bi, Sb, and Tl. In contrast, elevated 187Os/188Os without Ba and Os enrichment can be explained by adsorption of seawater-derived radiogenic Os onto Fe hydroxide during seawater ingress into volcaniclastic rocks with a high matrix volume.

Intense Re enrichment at Hole U1527 relative to the high-temperature alteration zone in altered MORB may be related to abundant pyrite precipitation and high Re content in primary arc magmas. We propose that degassed Re from shallow intraoceanic arc magmas may be sequestered by subseafloor high-temperature alteration. Part of the stored Re might also be released into the ocean by later oxidative seawater circulation and seafloor weathering, raising a question about the role of alteration zones in the Re cycle in subduction zones. This study is one of the first attempts to apply the Re–Os system to altered rocks in arc settings, and future research should provide more information about the fate of Re in intraoceanic arcs and the detailed role of hydrothermal alteration in the Re cycle on the Earth.

How to cite: Ishida, M., Nozaki, T., Takaya, Y., Ohta, J., Chang, Q., Kimura, J.-I., Nakamura, K., and Kato, Y.: Re–Os geochemistry of altered dacitic rock at Site U1527, IODP Expedition 376: Implications for the Re cycle in intraoceanic arcs, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3372, https://doi.org/10.5194/egusphere-egu22-3372, 2022.

EGU22-10040 | Presentations | SSP1.2

A profile through fast-spreading oceanic crust in the Oman ophiolite: reference frame for the crustal drillings within the ICDP Oman Drilling Project 

Jürgen Koepke, Dieter Garbe-Schönberg, Dominik Mock, and Samuel Müller

The Oman Ophiolite is the largest and best-investigated piece of ancient oceanic lithosphere on our planet. This ophiolite was target of the Oman Drilling Project (OmanDP) within the frame of ICDP (International Continental Scientific Drilling Program) which aimed to establish a comprehensive drilling program in order to understand essential processes related to the geodynamics of mid-ocean ridges, as magmatic formation, cooling/alteration by seawater-derived fluids, and the weathering with focus on the carbonatisation of peridotites.

Over two drilling seasons, the OmanDP has sampled the Samail Ophiolite sequence from crust to basal thrust. The total cumulative drilled length is 5458 m, with 3221 m of which was at 100% recovery. These cores were logged to IODP standards aboard the Japanese drilling vessel Chikyu during two description campaigns in summer 2017 and 2018. 

Here we present the main results of the working groups of the Universities Hannover and Kiel, focusing on the magmatic accretion of the Oman paleoridge. During 5 field campaigns these groups established a 5 km long profile through the whole crust of the Oman ophiolite by systematic outcrop sampling, providing the reference frame for the 400 m long OmanDP drill cores. The profile contains 463 samples from the mantle, through gabbros up to the dike/gabbro transition. Identical samples have been analyzed by several methods (bulk rock geochemistry, mineral analysis, Isotope geochemistry, EBSD analysis).

The results allow implication on the mechanism of accretion of fast-spreading lower oceanic crust. Depth profiles of mineral compositions combined with petrological modeling reveal insights into the mode of magmatic formation of fast-spreading lower oceanic crust, implying a hybrid accretion mechanism. The lower two thirds of the crust, mainly consisting of layered gabbros, formed via the injection of melt sills and in situ crystallization. Here, upward moving fractionated melts mixed with more primitive melts through melt replenishments, resulting in a slight but distinct upward differentiation trend. The upper third of the gabbroic crust is significantly more differentiated, in accord with a model of downward differentiation of a primitive parental melt originated from the axial melt lens located at the top of the gabbroic crust. Our hybrid model for crustal accretion requires a system to cool the deep crust, which was established by hydrothermal fault zones, initially formed on-axis at very high temperatures.

How to cite: Koepke, J., Garbe-Schönberg, D., Mock, D., and Müller, S.: A profile through fast-spreading oceanic crust in the Oman ophiolite: reference frame for the crustal drillings within the ICDP Oman Drilling Project , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10040, https://doi.org/10.5194/egusphere-egu22-10040, 2022.

EGU22-640 | Presentations | SSP1.2

DeepStor-1 exploration well at KIT Campus North (Upper Rhine Graben, Germany)

Schill Eva, Florian Bauer, Ulrich Steiner, Bernd Frieg, and Thomas Kohl

DeepStor-1 is the exploration well to the Helmholtz research infrastructure "DeepStor". DeepStor focuses on the investigation of high-temperature heat storage at the rim of the fromer oil-field „Leopoldshafen“. It is located about 10 km north of the city of Karlsruhe (Germany). The DeepStor-1 well is planned to reach the Pechelbronn group at 1‘460 m, i.e. it includes nearly the entire Oligocene sediments at the site. Seismic investigation reveal a structurally undisturbed section that below 200 m depth covers the Landau, Bruchsal, Niederrödern and Froidefontaine Formations. Cores will be taken from the entire section below 820 m. In addition to coring, the logging program is planned to include besides technical logging, a caliper-, self-potential-, temperature-, dual latero-, natural gamma spectrometry-, neutron-gamma porosity-, sonic-, elemental capture spectroscopy-, as well as image-logs in the sections 215-820 m as well as 820-1460 m. Drilling of DeepStor-1 is planned between 2022 and 2023.

How to cite: Eva, S., Bauer, F., Steiner, U., Frieg, B., and Kohl, T.: DeepStor-1 exploration well at KIT Campus North (Upper Rhine Graben, Germany), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-640, https://doi.org/10.5194/egusphere-egu22-640, 2022.

EGU22-8952 | Presentations | SSP1.2

‘SaltGiant’ drilling in the Sorbas Basin: Structural, Petrophysical and Geochemical characterization of the Messinian Salinity Crisis deposits

Fadl Raad, Philippe Pezard, Cesar Viseras, Francisco J. Sierro, Luis M. Yeste, Javier J. Aguila, Paula Jerez, Andrea Schleifer, Fabio Meneghini, Cinzia Bellezza, Johanna Lofi, Angelo Camerlenghi, and Giovanni Aloisi

The Late Miocene deposits in the Sorbas Basin (Spain) have been of an extreme importance in the understanding of the Messinian Salinity Crisis (MSC) events (5.97-5.33 Ma). They consist of four formations. The pre-crisis Abad marls topped by the evaporitic Yesares gypsum member, followed by two non-evaporitic units known as the Sorbas and Zorreras members. Those deposits have been widely explored and studied thanks to the numerous outcropping sections in the basin.


The ‘SaltGiant’ European Training Network held a training school in October 2021 in the Sorbas Basin, where four boreholes (named SG0, 1, 2 and 3) covering most of the Messinian Salinity Crisis sequence, were drilled, cored and logged in this context along an overall thickness of about 175 m. The drillings took place inside and in the vicinity of the Torralba gypsum mine. It allowed for the first time in the scientific non-industrial domain, access to a continuous and non-outcropping succession of the Messinian deposits in the Sorbas basin. In addition to the recovered cores, borehole geophysical data were obtained from the four holes and digital images of the area were collected with a drone. Prior to the drilling, an OBO (Outcrop / Behind Outcrop) workflow was followed, which will allow integrating the outcrop and subsurface data by combining the 3D geometry of geobodies with geophysical information.


Optical borehole wall images provide mm-scale images of the borehole walls, highlighting the sedimentological and structural characteristics of the deposits. Downhole geophysical measurements included acoustic velocity, electrical resistivity and natural spectral gamma ray, which allowed determining the petrophysical characteristics of the penetrated lithologies. In addition to the petrophysical logs, a Vertical Seismic Profiling was performed in holes SG2 and SG3, including a multi-offset VSP survey in hole SG3.


The petrophysical characterization of the Messinian deposits will provide a reference case study for the lithologic characterization of MSC deposits in the subsurface elsewhere. VSP analysis provided an in-field preliminary seismic velocity evaluation in the encountered formations. Preliminary results confirm the astronomical precession-driven cyclicity observed elsewhere in the Messinian gypsum. Further processing and analyses of the large amount of acquired data will lead to identifying the astronomical and possibly higher-frequency cyclicity in the post-evaporitic deposits in the Sorbas member.

How to cite: Raad, F., Pezard, P., Viseras, C., Sierro, F. J., Yeste, L. M., Aguila, J. J., Jerez, P., Schleifer, A., Meneghini, F., Bellezza, C., Lofi, J., Camerlenghi, A., and Aloisi, G.: ‘SaltGiant’ drilling in the Sorbas Basin: Structural, Petrophysical and Geochemical characterization of the Messinian Salinity Crisis deposits, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8952, https://doi.org/10.5194/egusphere-egu22-8952, 2022.

EGU22-2525 | Presentations | SSP1.2

Biological sulfate reduction in deep subseafloor sediment of Guaymas Basin

Toshiki Nagakura, Florian Schubert, and Jens Kallmeyer and the IODP Exp. 385 Scientists

Sulfate reduction is the quantitatively most important process to degrade organic matter in anoxic marine sediment and has been studied intensively in a variety of settings. Guaymas Basin, a young marginal ocean basin, offers the unique opportunity to study sulfate reduction in an environment characterized by organic-rich sediment, high sedimentation rates, and high geothermal gradients (100-958°C km-1). We measured sulfate reduction rates (SRR) in samples of the International Ocean Discovery Program (IODP) Expedition 385 using incubation experiments with radiolabeled 35SO42- carried out at in-situ pressure and temperature. Site U1548C, outside of a circular hydrothermal mound above a hot sill intrusion (Ringvent), has the highest geothermal gradient (958°C km-1) of all eight sampling sites. In near-surface sediment from this site, we measured the highest SRR (387 nmol cm-3 d-1) of all samples from this expedition. At Site U1548C SRR were generally over an order of magnitude higher than at similar depths at other sites. Site U1546D also had a sill intrusion, but it had already reached thermal equilibrium and SRR were in the same range as nearby Site U1545C, which is minimally affected by sills. The wide temperature range found in the stratigraphic section at each drill site leads to major shifts in microbial community composition with very different temperature optima. At the transition between the mesophilic and thermophilic range around 40 to 60°C, sulfate-reducing activity appears to be decreased, particularly in more oligotrophic settings but shows a slight recovery at higher temperatures.

How to cite: Nagakura, T., Schubert, F., and Kallmeyer, J. and the IODP Exp. 385 Scientists: Biological sulfate reduction in deep subseafloor sediment of Guaymas Basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2525, https://doi.org/10.5194/egusphere-egu22-2525, 2022.

EGU22-2909 | Presentations | SSP1.2 | Highlight

Microbial survival through high metabolic rates in a deep and hot subseafloor environment

Florian Schubert, Felix Beulig, Rishi Ram Adhikari, Clemens Glombitza, Verena Heuer, Kai-Uwe Hinrichs, Kira Homola, Fumio Inagaki, Bo Barker Jørgensen, Jens Kallmeyer, Sebastian Krause, Yuki Morono, Justine Sauvage, Arthur Spivack, and Tina Treude

A fourth of the global seabed sediment volume is buried at depths where temperatures exceed 80 °C, a previously proposed thermal barrier for life in the subsurface. Here, we demonstrate, utilizing an extensive suite of radiotracer experiments, the prevalence of active methanogenic and sulfate-reducing populations in deeply buried marine sediment from the Nankai Trough subduction zone, heated to extreme temperature (up to ~120 °C). Sediment cores were recovered during International Ocean Discovery Program (IODP) Expedition 370 to Nankai Trough, off the cost of Moroto, Japan. The steep geothermal gradient of ~100 °C km-1 allowed for the exploration of most of the known temperature range for life over just 1 km of drill core. Despite the high temperatures, microbial cells were detected almost throughout the entire sediment column, albeit at extremely low concentration of <500 cells per cm³ in sediment above ~50 °C. In millions of years old sediment a small microbial community subsisted with high potential cell-specific rates of energy metabolism, which approach the rates of active surface sediments and laboratory cultures. Even under the most conservative assumptions, potential biomass turnover times for the recovered sediment ranges from days to years and therefore many orders of magnitude faster than in colder deep sediment.

Our discovery is in stark contrast to the extremely low metabolic rates otherwise observed in the deep subseafloor. As cells appear to invest most of their energy to repair thermal cell damage in the hot sediment, they are forced to balance delicately between subsistence near the upper temperature limit for life and a rich supply of substrates and energy from thermally driven reactions of the sediment organic matter.

How to cite: Schubert, F., Beulig, F., Adhikari, R. R., Glombitza, C., Heuer, V., Hinrichs, K.-U., Homola, K., Inagaki, F., Jørgensen, B. B., Kallmeyer, J., Krause, S., Morono, Y., Sauvage, J., Spivack, A., and Treude, T.: Microbial survival through high metabolic rates in a deep and hot subseafloor environment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2909, https://doi.org/10.5194/egusphere-egu22-2909, 2022.

EGU22-1679 | Presentations | SSP1.2

Direct evidence of high pore pressure at the toe of the Nankai accretionary prism

Joshua Pwavodi and Mai-Linh Doan

The Nankai Trough is a locus of slow slip, low frequency earthquakes and Mw>8 classical earthquakes. It is assumed that high pore pressure contributes substantially to earthquake dynamics. Hence, a full understanding of the hydraulic regime of the Nankai accretionary prism is needed to understand this diversity of behaviors. We contribute to this understanding by innovatively integrating the drilling and logging data of the NanTroSEIZE project. We focus on the toe of the accretionary prism by studying data from Hole C0024A drilled and intersected the décollement at 813 mbsf about 3km away from the trench.

Down Hole Annular Pressure was monitored during drilling. We perform a careful quantitative reanalysis of its variation and show localized fluid exchange between the formation and the borehole (excess of 0.05m3/s), especially in the damage zones at the footwall of the décollement.

Pore pressure was estimated using Eaton’s method on both drilling and sonic velocity data. The formation fluids are getting significantly over-pressurized only a few hundred meters from the toe of the accretionary prism near the décollement with excess pore-pressure (P*≈0.04–4.79MPa) and lithostatic load (λ≈88-0.96 & λ*≈0.1-0.62 ) contributing to maximum 62% of the overburden stress.

The hydraulic profile suggests that the plate boundary acts as a barrier inhibiting upward fluid convection, as well as a lateral channel along the damage zone, favouring high pore pressure at the footwall. Such high pressure at the toe of the subsection zone makes high pressure probable further down in the locus of tremors and slow slip events.

How to cite: Pwavodi, J. and Doan, M.-L.: Direct evidence of high pore pressure at the toe of the Nankai accretionary prism, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1679, https://doi.org/10.5194/egusphere-egu22-1679, 2022.

EGU22-1729 | Presentations | SSP1.2

IODP Expedition 386 “Japan Trench Paleoseismology”: Mission Specific Platform Giant Piston Coring to track past megathrust earthquakes and their consequences in a deep-sea subduction trench. 

Michael Strasser, Ken Ikehara, Jeremy Everest, and Lena Maeda and the IODP Expedition 386 Science Party

International Ocean Discovery Program (IODP) Expedition 386, Japan Trench Paleoseismology (offshore period: 13 April to 1 June 2021; Onshore Science Party: 14 February to 14 March 2022) was designed to test the concept of submarine paleoseismology in the Japan Trench, the area where the last, and globally only one out of four instrumentally-recorded, giant (i.e. magnitude 9 class) earthquake occurred back in 2011. “Submarine paleoseismology” is a promising approach to investigate deposits from the deep sea, where earthquakes leave traces preserved in the stratigraphic succession, to reconstruct the long-term history of earthquakes and to deliver observational data that help to reduce uncertainties in seismic hazard assessment for long return periods. This expedition marks the first time, giant piston coring (GPC) was used in IODP, and also the first time, partner IODP implementing organizations cooperated in jointly implementing a mission-specific platform expedition.

We successfully collected 29 GPCs at 15 sites (1 to 3 holes each; total core recovery 831 meters), recovering 20 to 40-meter-long, continuous, upper Pleistocene to Holocene stratigraphic successions of 11 individual trench-fill basins along an axis-parallel transect from 36°N – 40.4°N, at water depth between 7445-8023 m below sea level. These offshore expedition achievements reveal the first high-temporal and high spatial resolution investigation and sampling of a hadal oceanic trench, that form the deepest and least explored environments on our planet.

The cores are currently being examined by multimethod applications to characterize and date hadal trench sediments and extreme event deposits, for which the detailed sedimentological, physical and (bio-)geochemical features, stratigraphic expressions and spatiotemporal distribution will be analyzed for proxy evidence of giant earthquakes and (bio-)geochemical cycling in deep sea sediments. Initial preliminary results presented in this EGU presentation reveal event-stratigraphic successions comprising several 10s of potentially giant-earthquake related event beds, revealing a fascinating record that will unravel the earthquake history of the different along-strike segments that is 10–100 times longer than currently available information. Post-Expedition research projects further analyzing these initial IODP data sets will (i) enable statistically robust assessment of the recurrence patterns of giant earthquakes, there while advancing our understanding of earthquake-induced geohazards along subduction zones and (ii) provide new constraints on sediment and carbon flux of event-triggered sediment mobilization to a deep-sea trench and its influence on the hadal environment.

 

How to cite: Strasser, M., Ikehara, K., Everest, J., and Maeda, L. and the IODP Expedition 386 Science Party: IODP Expedition 386 “Japan Trench Paleoseismology”: Mission Specific Platform Giant Piston Coring to track past megathrust earthquakes and their consequences in a deep-sea subduction trench. , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1729, https://doi.org/10.5194/egusphere-egu22-1729, 2022.

EGU22-3538 | Presentations | SSP1.2 | Highlight

Deformation mechanisms along the Main Marmara Fault around the ICDP-site GONAF

Magdalena Scheck-Wenderoth, Mauro Cacace, Oliver Heidbach, Marco Bohnhoff, Murat Nurlu, Naiara Fernandez Terrones, Judith Bott, and Ershad Gholamrezaie

The Main Marmara Fault (MMF) in NW Turkey south of Istanbul is a segment of the North Anatolian Fault Zone (NAFZ) that constitutes a right-lateral continental transform fault.  Several well-documented strong (M7+) earthquakes indicate that the MMF poses a great risk to the Istanbul metropolitan region. A 150 km long stretch of the MMF has not ruptured since 1766 and the recurrence time of 250 yrs for M7+ events derived from historical records indicate that the fault is overdue. We introduce a new project addressing how the rheological configuration of the lithosphere in concert with active fluid dynamics within the crust and mantle influence the present-day deformation along the MMF in the Marmara Sea region. We test the following hypotheses: (1) the seismic gap is related to the mechanical segmentation along the MMF which originates from the rheological configuration of the crust and lithosphere; (2) variations in deformation mechanisms with depth in response to variations in temperature and (fluid) pressure exert a first-order control on the mode of seismic activity along the MMF, and, (3) stress and strain concentrations due to strength and structural variability along the MMF can be used as an indicator for potential nucleation areas of expected earthquakes. To assess what mechanisms control the deformation along the MMF, we use data from the ICDP GONAF observatory (International Continental Drilling Programme – Geophysical Observatory at the North Anatolian Fault) and a combined work flow of data integration and process modelling to derive a quantitative description of the physical state of the MMF and its surrounding crust and upper mantle. Seismic and strain observations from the ICDP-GONAF site are integrated with regional observations on active seismicity, on the present-day deformation field at the surface, on the deep structure (crust and upper mantle) and on the present-day stress and thermal fields. This will be complemented by numerical forward simulations of coupled thermo-hydraulic-mechanical processes based on the observation-derived 3D models to evaluate the key controlling factors for the present-day mechanical configuration of the MMF and to contribute to a physics-based seismic hazard assessment.

How to cite: Scheck-Wenderoth, M., Cacace, M., Heidbach, O., Bohnhoff, M., Nurlu, M., Fernandez Terrones, N., Bott, J., and Gholamrezaie, E.: Deformation mechanisms along the Main Marmara Fault around the ICDP-site GONAF, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3538, https://doi.org/10.5194/egusphere-egu22-3538, 2022.

EGU22-11265 | Presentations | SSP1.2

Heterogeneous deformation across the Papaku fault, Hikurangi accretionary prism 

Rebecca Kühn, Annika Greve, Rüdiger Kilian, Marcel Mizera, and Michael Stipp

At the Hikurangi convergent margin the Pacific plate is subducted westward beneath the Australian plate. This margin has been the location of major earthquakes as well as slow slip events related to the ongoing subduction. Drill site U1518 which was drilled during IODP Expedition 375, 73 km offshore Gisborne (New Zealand), targeted the Papaku fault, a splay fault of the major decollement in sediments of the frontal accretionary prism. We selected samples from the mostly hemipelagic, weakly consolidated mudstones in the fault zone, as well as from hangingwall and footwall. In order to investigate localized and distributed deformation in the fault zone, we analysed composition, microstructure and crystallographic preferred orientation (CPO). For that we applied µXRF measurements and optical microscopy, as well as synchrotron texture analysis at DESY in Hamburg.

The samples from hanging- and footwall sediments show a relatively homogeneous microstructure with local compositional layering. While CPO strength in the hangingwall is slightly increasing with depth for all analysed clay mineral phases, the CPO in the footwall samples is in general lower and does not show a clear trend with depth. This might be interpreted as different deformation histories in hangingwall and footwall which is in accordance with previous studies. Fault zone samples show a variety of microstructures, such as mingling of different sedimentary components, locally overprinted by microfaults. CPO strength in the faulted sediments is also variable, with zones showing strong alignment of phyllosilicates and zones showing weak alignment of phyllosilicates. Variations in CPO and variable distribution of sedimentary components indicate a heterogeneous deformation within the fault zone which might be due to local compositional variations.

How to cite: Kühn, R., Greve, A., Kilian, R., Mizera, M., and Stipp, M.: Heterogeneous deformation across the Papaku fault, Hikurangi accretionary prism , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11265, https://doi.org/10.5194/egusphere-egu22-11265, 2022.

EGU22-3793 | Presentations | SSP1.2

Legacy DSDP and ODP data suggest a paradigm shift in methane hydrate stability in the Mediterranean Basin

Cristina Corradin, Angelo Camerlenghi, Michela Giustiniani, Umberta Tinivella, and Claudia Bertoni

The global reservoir of submarine gas hydrates is favored by the cold temperature of oceanic bottom water and the generally low geothermal gradients along passive continental margins. The continental margins of the land-locked Mediterranean basin are a remarkable exception for the lack of evidence of extensive presence of gas hydrates. Using public data of the physics and chemistry of the subsurface available from 44 Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) wells as lithologic logs, downhole temperature measurements, and pore water salinity values, and observed physical characteristics of bottom waters, we model the theoretical methane hydrate stability zone (MHSZ) below the seafloor and in the water column.

We find important positive pore water salinity anomalies in the subsurface indicating the pervasive presence of concentrated brines up to saturation concentration of halite and gypsum (> 300 ‰). The resulting sub-bottom MHSZ is thinner by up to 90-95% with respect to its thickness calculated assuming constant salinity with depth equal to bottom waters salinity. In the Eastern Mediterranean deep basins the thickness of the subsurface MHSZ is largest (up to ~ 350 m) and the anomaly induced by subsurface brines is highest (~ -300 m), while in the Alboran, Western Mediterranean, Tyrrhenian, Sicily Channel, Adriatic and Aegean basins the MHSZ, where present, thins to less than 100 m with mostly negligible anomaly induced by the presence of subsurface brines.

Modelling results suggest that subsurface brines can produce dramatic reductions of the thickness of the MHSZ only where the geothermal gradient is low (Eastern Mediterranean). We have modelled the same brine-induced limiting effect on the thickness of the MHSZ in synthetic cases of high and low heat flow to simulate Western and Eastern Mediterranean subsurface thermo-haline conditions. The salinity effect is attenuated by the thermal effect in the Western Mediterranean that produces the most relevant thinning of the MHSZ.

The distribution of the MHSZ resulting from the modelling coincides well with the distribution of the Late Miocene salt deposits which limit further the possibility of formation of gas hydrates acting as low permeability seal to the up-ward migration of hydrocarbon gases.

This modelling exercise provides a robust explanation for the lack of evidence of widespread gas hydrates on Mediterranean continental margins, with the exception of areas of local methane upward advection such as mud volcanoes, and it outlines a number of local hydrate-limiting factors that make this basin unfavorable to gas hydrate occurrence.

How to cite: Corradin, C., Camerlenghi, A., Giustiniani, M., Tinivella, U., and Bertoni, C.: Legacy DSDP and ODP data suggest a paradigm shift in methane hydrate stability in the Mediterranean Basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3793, https://doi.org/10.5194/egusphere-egu22-3793, 2022.

EGU22-4022 | Presentations | SSP1.2 | Highlight

Half-precession signals in marine an terrestrial records – connecting IODP/ICDP sites from the equatorial Atlantic to Greenland

Arne Ulfers, Christian Zeeden, Silke Voigt, Mehrdad Sardar Abadi, and Thomas Wonik

The characteristics of half-precession (HP) cycles (~9,000 - 12,000 years) is still poorly understood, despite their appearance in numerous records. We analyse HP signals in a variety of different marine and terrestrial proxy records from Europe and the Atlantic Ocean, investigate the temporal evolution of the HP signal from the early/middle Pleistocene to the present, and evaluate the potential of the HP to reflect the connectivity of climate systems over time.

We apply filters on the datasets that remove the classical orbital cycles (eccentricity, obliquity, precession) and high frequency signals, and focus on the bandwidth of HP signals. Wavelet annalysis and correlation techniques are used to study the evolution of specific frequencies through the different records.

In addition to a connection of HP cycles with interglacials, we observe a more pronounced HP signal in the younger part of several proxy records. Besides, we observe a trend of more pronounced HP signals in low latitude records compared to high latitudes. This is in agreement with the assumption that HP is an equatorial signal and can be transmitted northward via various pathways. The appearance of HP signals in mid- and high-latitude records may thus be an indicator for the intensity of the transporting mechanisms. We suggest that the African Monsoon plays a major role in this context, as its magnitude directly influences the climate systems of the Mediterranean and Southern Europe. In order to better understand the African climate variability, both equatorial marine and terrestrial records will be examined with respect to HP.

How to cite: Ulfers, A., Zeeden, C., Voigt, S., Sardar Abadi, M., and Wonik, T.: Half-precession signals in marine an terrestrial records – connecting IODP/ICDP sites from the equatorial Atlantic to Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4022, https://doi.org/10.5194/egusphere-egu22-4022, 2022.

EGU22-10406 | Presentations | SSP1.2

Assessing the well logging data from the Lake Bosumtwi (Ghana)

Christian Zeeden, Mathias Vinnepand, Stefanie Kaboth-Bahr, William Gosling, Jochem Kück, and Thomas Wonik

Insights into the climate variability of western Africa during the Pleistocene epoch have thus far been limited by the lack of well-dated, high-resolution terrestrial climate archives. The missing information on the climate evolution of western African hampers our understanding of the proposed pan-African evolution of our species. The ~294 m lacustrine sedimentary sequence raised from Lake Bosumtwi by the International Continental Drilling program in 2004, encompassing the last ~1.1 Ma, offers the best opportunity provide a climatic benchmark record in western Africa. However, the establishment of a chronology for this record has proven challenging. To try and improve our understanding of the climatic evolution during the last ~1.1 Ma in western Africa, we will use the high-resolution downhole logging data (natural gamma ray, GR) and magnetic susceptibility data from core logging from Site 5, which is situated in the centre of Lake Bosumtwi. To maximise the robustness of this record we will try to correlate data from downhole logs with core data. This approach has help improve interpretation of logging signals and environmental reconstructions for other long lake records, such as e.g. Lake Ohrid.

How to cite: Zeeden, C., Vinnepand, M., Kaboth-Bahr, S., Gosling, W., Kück, J., and Wonik, T.: Assessing the well logging data from the Lake Bosumtwi (Ghana), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10406, https://doi.org/10.5194/egusphere-egu22-10406, 2022.

EGU22-3534 | Presentations | SSP1.2

Reconstructing the moisture availability of Central Mexico over the past 500,000 years using borehole logging data

Mehrdad Abadi, Christian Zeeden, Arne Ulfers, and Thomas Wonik

Assessing the moisture history of Central Mexico reveals the responses of tropical areas to variation in past climate. Central Mexico has several long-lived lakes, which are potentially important paleoclimate archives. Lake Chalco in Central Mexico contains a ~300 m lacustrine sequence, which were deposited over a period of ~500,000 years. We conducted Spectral Gamma Ray (SGR) measurements across the lacustrine deposits of Lake Chalco to reconstruct the moisture availability over the past. The SGR data reflect the presence of naturally occurring radioactive elements including potassium (40K) and the equilibrium decay series of uranium (U) and thorium (Th). Natural sources of gamma radiation in lacustrine deposits of Lake Chalco are from volcanic ash deposition and detrital input of eroded sediments containing radioactive elements. However, redox conditions in the lake water influence the mobility of soluble U through conversion to more stable reduced phases. To extract the primary non-volcanic signals, we detected and removed signals from embedded tephra layers in the lacustrine sediments of Lake Chalco. We developed a moisture proxy by calculating the probability of authigenic U distributed across the lake sediments. We expect that an increasing U content in proportion to the content of K and Th indicate redox conditions in lake bottom water as a result of rising lake level. To evaluate this moisture proxy, we examined differences in the percent of the diatom species that are indicative of a deeper lake from literature. Results suggest that Lake Chalco likely formed prior or within MIS13, and the lake level rose gradually over time until the interglacial period of MIS9. Moisture levels are higher during the interglacial than glacial periods and interglacial periods show higher moisture variability. While glacial periods have less moisture, two periods, MIS6 and MIS4, still have a higher likelihood of authigenic U and more moist conditions. In order to determine potential regulators of moisture, we compared models containing the drivers of Earth’s orbital cycles, carbon dioxide and sea surface temperature. Carbon dioxide, eccentricity, and precession are all key drivers of the moisture content of Lake Chalco over the past 500,000 years. High levels of atmospheric CO2 have a positive effect on the moisture in Mexico while eccentricity and precession consistently have negative effects on lake moisture. Obliquity and δ18O have weaker effects on moisture in Mexico, probably due to the equatorial high-altitude region far away from poles, oceans and ice sheets.

How to cite: Abadi, M., Zeeden, C., Ulfers, A., and Wonik, T.: Reconstructing the moisture availability of Central Mexico over the past 500,000 years using borehole logging data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3534, https://doi.org/10.5194/egusphere-egu22-3534, 2022.

The Izu-Bonin Mariana (IBM) convergent margin is located in the NW Pacific Ocean (12° N to 35° N) and represents, to the best of our knowledge, the only setting where recent episodes of serpentinite mud volcanism took place. The IBM arc-system started to form around 50-52 Ma when the Pacific Plate began to subside below the Philippine Plate and the eastern Eurasian Margin. On the Mariana forearc system, which constitutes the southward region of the IBM, a high number of large serpentinite mud volcanoes formed between the trench and the Mariana volcanic arc. Their origin is linked to episodic extrusion of serpentinite mud and fluids along with materials from the upper mantle, the Philippine plate, and the subducting Pacific plate to the sea floor, through a system of forearc faults. Among them, Fantangisña seamount was drilled during IODP Expedition 366. Cored material comprises serpentinite mud and ultramafic clasts that are underlain by nannofossil-rich forearc deposits and topped by pelagic sediments.

Integrated calcareous nannofossil and planktonic foraminifera biostratigraphy was performed on Sites U1497 and U1498, which are at the top of the serpentinite seamount and on its most stable southern flank, respectively. A total of nine bioevents were recorded in this study, permitting the establishment of a valid age-depth model for Site U1498A which allows for the definition of the latest phase of activity of Fantangisña serpentinite mud volcano. In particular, the emplacement of the mud production was detected between 6.10 (Late Miocene, Messinian) to 4.20 (Early Pliocene, Zanclean). This time interval is defined by nannofossil bioevents LO Reticulofenestra rotaria and FO of Discoaster asymmetricus. Furthermore, our analyses reveal that the latest stage of the serpentinite mud activity occurred 4 Ma later than the age proposed by a previous study (10.77 Ma) and is coeval with the initiation of the rifting in the Mariana Trough recorded at 7-6 Ma.

The age depth model also shows a rapid shift in sedimentation rates (11.80 to 94.71 m/Myr) during the Middle Pleistocene, which corresponds to a change in deposition of distinct serpentinite mud units, likely associated with the regional tectonic activity (different stages of seamount accretion and subduction and/or changes in the forearc extension related to the slab rollback).

How to cite: Del Gaudio, A. V., Piller, W. E., Auer, G., and Kurz, W.: Dating the serpentinite mud production of Fantangisña seamount using calcareous nannofossils and planktonic foraminifera biostratigraphy (IODP Expedition 366)., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1019, https://doi.org/10.5194/egusphere-egu22-1019, 2022.

EGU22-1313 | Presentations | SSP1.2

IODP 302 ACEX: Dating 'Zebra': was the Lomonosov Ridge an Arctic Island in the Oligocene?

Henk Brinkhuis, Francesca Sangiorgi, Evi Wubben, and Matt O'Regan

The Arctic is both a contributor to climate change and a region that is most affected by global warming. Despite this global importance, the Arctic Ocean is the last major region on Earth where the long-term climate history remains poorly known. Major advances in understanding were achieved in 2004 with the successful completion of IODP Expedition 302: Arctic Coring Expedition – ACEX – implemented by ECORD, marking the start of a new era in Arctic climate exploration. Although the ACEX results were unprecedented, key questions related to the Cenozoic Arctic climate history remain unanswered, largely due to a major mid-Cenozoic hiatus (or condensed interval) and partly to the poor recovery of the ACEX record. Building on ACEX and its cutting-edge science, IODP Expedition 377: Arctic Ocean Paleoceanography (ArcOP) has been scheduled for mid-August to mid-October 2022. The overall goal of ArcOP is the recovery of a complete stratigraphic sedimentary record on the southern Lomonosov Ridge to meet the highest priority paleoceanographic objective: the continuous long-term Cenozoic Arctic Ocean climate history with its transition from the early Cenozoic Greenhouse world to the late Cenozoic Icehouse world. Furthermore, sedimentation rates two to four times higher than those of ACEX will permit higher-resolution studies of Arctic climate change in the Neogene and Pleistocene. Key objectives are related to the reconstruction of the history of circum-Arctic ice-sheets, sea-ice cover, Siberian river discharge, and deep-water circulation and ventilation and its significance within the global climate system. Obtaining a geologic record of a 50-60 million year time span will provide opportunities to examine trends, pat­terns, rates, causes, and consequences of climate change that are important and relevant to our future. This goal can be achieved through (i) careful site selection, (ii) the use of appropriate drilling technology and ice management, and (iii) applying multi-proxy approaches to paleoceanographic, paleoclimatic, and age-model reconstructions.

In August 2022, a fleet of three ships, the drilling vessel “Dina Polaris” and the powerful icebreakers “Oden” and “Viktor Chernomyrdin”, will set sail for a location on Lomonosov Ridge in international waters far from shore (81°N, 140°E; 800-900 m of water depth). There, the expedition will complete one primary deep drill site (LR-11B) to 900 meters below seafloor (mbsf) which is twice that of the ACEX drill depth – certainly a challenging approach. Based on detailed site survey data, about 230 m of Plio‐Pleistocene, 460 m of Miocene, and >200 m of Oligocene‐Eocene sedimentary sequences might be recovered at this site. In addition, a short drill site (LR-10B) to 50 mbsf will be supplemented to recover an undisturbed uppermost (Quaternary) sedimentary section to ensure complete recovery for construction of a composite section spanning the full age range through the Cenozoic.

In this talk, background information, scientific objectives and an update of the status of planning and implementation of the ArcOP Expedition will be presented. For further details we refer to the ArcOP Scientific Prospectus (https://doi.org/10.14379/iodp.sp.377.2021).

How to cite: Stein, R., St.John, K., and Everest, J.: The Cenozoic Arctic Climate and Sea Ice History - Scientific objectives, challenges and implementation update of IODP Expedition 377 (ArcOP), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1277, https://doi.org/10.5194/egusphere-egu22-1277, 2022.

EGU22-1917 | Presentations | SSP1.2

Operations and Initial Results from IODP Expedition 396: Mid-Norwegian Continental Margin Magmatism and Paleoclimate

Sverre Planke, Christian Berndt, Ritske Huismans, Stefan Buenz, Carlos A. Alvarez Zarikian, and Expedition Scientists

The NE Atlantic conjugate volcanic rifted margins are characterized by extensive breakup-related magmatism recorded by basalt flows, volcanogenic sediments, magmatic underplates, and intrusive complexes in sedimentary basins and the crust. Onset of this voluminous magmatism is concomitant with the global hot-house climate in the Paleogene, and the injection of magma into organic-rich sedimentary basins is a proposed mechanism for triggering short-term global warming during the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma).

The aims of IODP Exp. 396 (August-September 2021) were to drill three transects on the mid-Norwegian continental margin to sample 1) hydrothermal vent complexes formed by eruption of hot fluids and sediments above sill intrusions (Modgunn Transect), 2) Paleogene sediments, with particular focus on the Paleocene-Eocene transition (Mimir Transect), and 3) basalt and sub-basalt sequences across the volcanic rifted margin and the initial oceanic crust (Basement Transect). A total of 21 boreholes were drilled, successfully coring all nine primary and one alternate sites. A comprehensive suite of wireline logs was collected in eight boreholes. Most of the sites were located on industry-standard 3D seismic reflection data, whereas additional high-resolution 2D and 3D P-Cable site survey data were acquired across six sites which were highly useful during the Mimir and Modgunn transect drilling. In total, more than 2000 m of core were recovered during 48 days of operations, including more than 350 m of basalt, 15 m of granite, and 900 m of late Paleocene to early Eocene sediments. Drilling was done using a combination of RCB, XCB, and APC drill bits, commonly with half-advances (c. 5 m) to optimize core recovery. Particularly high recovery (almost 100%) was obtained by half-length APC coring of Eocene sediments in two holes on the outer Vøring Margin, whereas basaltic basement recovery was above 60% in seven holes.

Expedition 396 probed the key elements of a typical volcanic rifted margin and the associated sedimentary archive. Of particular importance is the Modgunn Transect, where we drilled five holes through the upper part of a hydrothermal vent complex with a very expanded Paleocene-Eocene Thermal Maximum (PETM) interval dominated by biogenic ooze and volcanic ash deposits. The expedition also recovered an unprecedented suite of basalt cores across a volcanic rifted margin, including both subaerial and deep marine sheet flows with inter-lava sediments and spectacular shallow marine pillow basalts and hyaloclastites, as well as high-resolution interstitial water samples to assess sediment diagenesis and fluid migration in the region. Lastly, we recovered the first cores of sub-basalt granitic igneous rocks and upper Paleocene sediments along the mid-Norwegian continental margin. Collectively, this unique sample archive offers unprecedented insight on tectonomagmatic processes in the NE Atlantic, and links to rapid climate evolution across the Cenozoic.

How to cite: Planke, S., Berndt, C., Huismans, R., Buenz, S., Alvarez Zarikian, C. A., and Scientists, E.: Operations and Initial Results from IODP Expedition 396: Mid-Norwegian Continental Margin Magmatism and Paleoclimate, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1917, https://doi.org/10.5194/egusphere-egu22-1917, 2022.

EGU22-3428 | Presentations | SSP1.2

Hipercorig Hallstatt History (H3) reveals a high-resolution Late Pleistocene to Holocene sediment record at Lake Hallstatt (Salzkammergut, Austria)

Marcel Ortler, Achim Brauer, Stefano C. Fabbri, Kerstin Kowarik, Jochem Kueck, and Michael Strasser

The innovative, new drilling technique of the Hipercorig platform (Harms et al., 2020, https://doi.org/10.5194/sd-28-29-2020) enables to recover undisturbed long cores of sediment archives, and hence allows us to study past environmental conditions and changes. Here we present initial results from the Hipercorig Hallstatt History (H3) lake drilling campaign 2021, which succeeded to recover two parallel cores (core A: 41m, core B: 51m) from 122 m water depth providing a high-resolution record, within the UNESCO World Heritage Cultural Landscape Hallstatt-Dachstein/Salzkammergut, Austria. The Hallstatt-Dachstein region has a history of over 7,000 years of human salt mining and is one of the oldest documented cultural landscapes worldwide.

We present physical- and litho-stratigraphy based on borehole logging (of hole B), non-destructive core logging data, visual core and lithofacies description, Core-Log-Seismic-Correlation and initial age modelling using 14C dating. The core logging covers (i) x-ray computed tomography, (ii) multi-sensor-core-logger data with Gamma-Ray attenuated bulk density, magnetic susceptibility and visible light photo spectroscopy. The upper ~15 m of the sediment profile can be unambiguously correlated with previous cores (Lauterbach et al., submitted) thus confirming that the sediments are truly representative for Lake Hallstatt. The entire stratigraphic succession comprises two major lithostratigraphic units: The Holocene unit (0-40 m below lake floor (mblf)) and the Late Pleistocene unit (> 40 m). The Holocene unit consists of variably laminated (sub-mm to 5 mm) dark gray clayey-silty carbonate mud interbedded with up to 5.5 m thick mass-movement deposits and thick turbidites. The Late Pleistocene sedimentary succession comprises very thin bedded (1-3 cm) medium gray silty clayey carbonate mud, with some laminated (<1 cm) intervals and multiple cm-thick light gray turbidites. Within the Late Holocene unit, there is a prominent yellowish gray clastic interval of ~4 m with faintly mm- to cm-scale laminated sediments. Another remarkable characteristic of the Holocene unit is the occurrence of at least four major mass-movement deposits containing pebbles (up to 3 cm in diameter) and six thick turbidite deposits >1 m with different sediment colors and compositions.

Detailed multi-proxy analyzes of the Lake Hallstatt cores will provide new insights into the early history of human settlement and salt mining in this Alpine region and their relation to environmental and climatic conditions and meteorological and geological extreme events.

How to cite: Ortler, M., Brauer, A., Fabbri, S. C., Kowarik, K., Kueck, J., and Strasser, M.: Hipercorig Hallstatt History (H3) reveals a high-resolution Late Pleistocene to Holocene sediment record at Lake Hallstatt (Salzkammergut, Austria), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3428, https://doi.org/10.5194/egusphere-egu22-3428, 2022.

EGU22-3165 | Presentations | SSP1.2 | Highlight

Drilling Overdeepened Alpine Valleys (ICDP-DOVE): Age, extent and environmental impact of Alpine glaciations

Flavio Anselmetti and Marius Buechi and the ICDP-DOVE Team

The sedimentary infill of glacially overdeepened valleys (i.e. eroded structures below the fluvial base level) are, together with glacial geomorphology, the best-preserved (yet underexplored) direct archives of extents and ages of past glaciations in and around mountain ranges. ICDP project DOVE (Drilling Overdeepened Alpine Valleys) Phase-1 investigates five drill cores from glacially overdeepened structures at several complementing locations along the northern front of the Alps and their foreland. Two of these drill sites, both in the former reaches of the Rhine Glacier, have been successfully drilled in 2021 with excellent core recovery of 95 %: i) The borehole in Basadingen in Northern Switzerland reached a depth of 253 m, and ii) The Tannwald site in Southern Germany consists of one cored borehole to 165 m and two nearby flush boreholes; all three sites will allow a series of crosshole geophysical experiments. Three previously drilled legacy cores from the Eastern Alps are included in the DOVE Phase-1: iii) a core from Schäftlarn, located in the Isar-Loisach glacier catchment, was drilled in 2017 down to a depth of 199 m; iv) the Neusillersdorf drill site, located in the southern German Salzach Foreland glacier area, recovered a sequence down to 136 m (incl. 116 m of Quaternary strata); and v) the drill site Bad Aussee in Austria is located in the area of the Traun Glacier at an inneralpine location. It recovered almost 900 m of Quaternary sediments.

All the sites will be investigated with regard to several aspects of environmental dynamics during the Quaternary, with focus on the glaciation, vegetation, and landscape history. For example, the geometry of overdeepened structures will be investigated using different geophysical approaches (e.g. seismic surveys) to better understand the process of overdeepening. Sedimentological analyses in combination with downhole logging, investigation of biological remains and state-of-the-art geochronological methods will allow to reconstruct the filling and erosion history of the troughs. We expect significant and novel data relating to the extent and timing of the past Alpine glaciations during the Middle-to-Late Quaternary glacial-interglacial cycles. Besides these basic scientific goals, this proposal also addresses a number of applied objectives such as groundwater resources, geothermal energy production, and seismic hazard assessment.

A successful DOVE Phase-1 will lay the ground for an upcoming Phase-2 that will complete the panalpine approach. This follow-up phase will investigate paleoglacier lobes from the western and southern Alpine margins through drilling sites in France, Italy and Slovenia.

How to cite: Anselmetti, F. and Buechi, M. and the ICDP-DOVE Team: Drilling Overdeepened Alpine Valleys (ICDP-DOVE): Age, extent and environmental impact of Alpine glaciations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3165, https://doi.org/10.5194/egusphere-egu22-3165, 2022.

SSP1.3 – Mass extinctions and major environmental changes throughout Earth history: Link with volcanism and impacts

EGU22-5403 | Presentations | SSP1.3 | Highlight

The role of Large Igneous Provinces in controlling long-term Phanerozoic climate change

Jack Longman and Benjamin J.W. Mills

Large Igneous Provinces (LIPs) are accumulations of igneous rocks representing periods of intense volcanism in Earth’s history. The timing of the emplacement of many LIPs corresponds with global climatic perturbations and mass extinctions, leading to the hypothesis that their occurrence is implicated in these events. However, detailed investigations into these hypotheses are typically restricted to studies of individual events (e.g. the Siberian Traps emplacement at the Permian-Triassic boundary), and single forcing mechanisms (e.g. carbon emissions). As a result, it is often unclear what the overall impact of LIP emplacement was on climate in Earth’s history.

In this work, we present the results of the first integration of LIP degassing and weathering to a long-term model of global carbon cycling. We use the SCION climate-chemical model, which allows for both the addition of LIP degassing as a CO2 forcing mechanism, and the introduction of LIPs as highly weatherable terranes on the Earth surface. In this way, we can estimate both the warming impact LIPs may have had on climate change in the past, through carbon degassing, but also the cooling effect they would have had, through enhanced silicate weathering. Our work shows the importance of LIP location on weathering rates, with those which are emplaced in the mid-latitudes having the biggest cooling impact.

Comparison of our reconstruction with previous estimates of Phanerozoic climates show that the inclusion of LIPs enhances model-data comparability. This is particularly clear in the late Triassic, and Cretaceous periods, where previous model reconstructions overestimated atmospheric CO2 and global temperature. Our findings suggest LIP weathering is an important factor mitigating global climate change through the Phanerozoic.

How to cite: Longman, J. and Mills, B. J. W.: The role of Large Igneous Provinces in controlling long-term Phanerozoic climate change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5403, https://doi.org/10.5194/egusphere-egu22-5403, 2022.

EGU22-5955 | Presentations | SSP1.3

Degradation of mercury (Hg) signals on incipient weathering refines use of Hg as a volcanic paleoproxy

Junhee Park, Holly Stein, Svetoslav Georgiev, and Judith Hannah

Perceived mercury (Hg) enrichments and elevated ratios of Hg to total organic carbon (Hg/TOC) in sedimentary rocks have often been linked to volcanism from large igneous provinces (LIPs) and mass extinctions, prompting the hypothesis that elevated Hg concentrations are a proxy for intense volcanism from LIPs.  However, primary Hg and TOC contents of sedimentary rocks can be altered by secondary processes, for example, intense weathering [1].  Before endorsing cause-and-effect between volcanic Hg emissions and biotic crises or mass extinctions, the magnitude of measured Hg and Hg/TOC anomalies in weathered outcrop samples must be compared to equivalent units in core samples, where the outcrop sample provides, in effect, a minimum concentration value.  

Here, we investigate the effects of incipient weathering on Hg contents and Hg/TOC ratios.  We quantify the behavior of Hg during incipient weathering by determining Hg concentrations in visually pristine black shales from outcrops of the Upper Permian Ravnefjeld Formation in East Greenland, comparing these data to equivalent intervals acquired from drill core taken from a plateau 7 km from the outcrop.  Directly correlative Upper Permian shales (drill core) from the mid-Norwegian shelf further enhance our comparison.  Using detailed geochemistry and principal component analysis (PCA), we characterize the main host phases of Hg and relate different Hg contents from pristine samples from East Greenland and the mid-Norwegian shelf to different Hg inputs during shale deposition.  Importantly, we show the vulnerability of Hg contents and Hg/TOC ratios to incipient weathering of fresh-appearing outcrops of organic-rich shale.  

Working with drill core rather than outcrop samples is essential to circumvent the problem, and to provide accurate Hg concentration data for primary events in the paleo-record.

[1] Charbonnier, G., Adatte, T., Föllmi, K.B., and Suan, G. (2020) Effect of intense weathering and postdepositional degradation of organic matter on Hg/TOC proxy in organic-rich sediments and its implications for deep-time investigations. Geochemistry, Geophysics, Geosystems, 21(2).

Funding – HS acknowledges the support of ACS-PRF award #59965-ND2 supporting AIRIE PhD student JP.  Drill cores were acquired from GEUS under Petromaks grant (NFR 180015/S30).  Colorado State University-Geosciences provides no funding for the personnel and operation of the AIRIE Program and its Re-Os laboratories. 

How to cite: Park, J., Stein, H., Georgiev, S., and Hannah, J.: Degradation of mercury (Hg) signals on incipient weathering refines use of Hg as a volcanic paleoproxy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5955, https://doi.org/10.5194/egusphere-egu22-5955, 2022.

EGU22-8013 | Presentations | SSP1.3

Mercury isotope evidence for sustained regional volcanism in south China before and after the Permian-Triassic boundary

Oluwaseun Edward, André Navin Paul, Hugo Bucher, Borhan Bagherpour, Aymon Baud, Thierry Adatte, Jeroen Sonke, Urs Schaltegger, and Torsten Vennemann

The Permian-Triassic boundary mass extinction (PTBME) is recognized as the most severe extinction of the Phanerozoic and has been causally linked to the Siberian Traps Large Igneous Province (STLIP) volcanism (e.g., Burgess and Bowring, 2015; Svensen et al, 2009; Sanei et al., 2012). This link is suggested based on the approximate temporal coincidence of STLIP magmatism and sedimentary successions straddling the PTB, which bear evidence of faunal extinction as well as elevated mercury (Hg) concentrations. However, several marine successions spanning the Late Permian to Early Triassic do not have elevated Hg content or are not synchronous in terms of their Hg concentration “anomalies” and the PTB interval (e.g., Sial et al., 2020). Furthermore, Hg sequestered in marine sediments may differ in provenance and its depositional pathways (Yager et al., 2021), complicating the use of Hg anomalies as a direct and reliable proxy for volcanism. This study investigates Hg concentrations and Hg isotopic composition together with total organic carbon (TOC) content, organic carbon δ13C values and element concentrations from two deep-water PTBME sedimentary sections in the Nanpanjiang basin, south China, spanning the Late Permian to Early Triassic. The Hg anomaly in these successions is found to coincide with the nadir of the negative C-isotope excursion close to the PTB. However, based on both the fossil associations as well as precise U-Pb ages for volcanic ash layers within these successions, these anomalies are of Griesbachian age. Hg isotope compositions support a volcanic origin and constant provenance for the Hg across the entire interval studied. These features, together with the common occurrence of volcanic ash beds throughout the investigated successions, are compatible with regional volcanic arc magmatism as a probable source of the Hg. The present results highlight that elevated Hg concentrations in marine successions straddling the PTB in south China cannot be unequivocally linked to STLIP volcanism.

 

 

References

Burgess, S. D., and Bowring, S. A., 2015, High-precision geochronology confirms voluminous magmatism before, during, and after Earth’s most severe extinction: Science Advances, v. 1, no. 7, p. e1500470.

Sanei, H., Grasby, S. E., and Beauchamp, B., 2012, Latest Permian mercury anomalies: Geology, v. 40, no. 1, p. 63-66.

Sial, A., Chen, J., Lacerda, L., Korte, C., Spangenberg, J., Silva-Tamayo, J., Gaucher, C., Ferreira, V., Barbosa, J., and Pereira, N., 2020, Globally enhanced Hg deposition and Hg isotopes in sections straddling the Permian–Triassic boundary: Link to volcanism: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 540, p. 109537.

Svensen, H., Planke, S., Polozov, A. G., Schmidbauer, N., Corfu, F., Podladchikov, Y. Y., and Jamtveit, B., 2009, Siberian gas venting and the end-Permian environmental crisis: Earth and Planetary Science Letters, v. 277, no. 3-4, p. 490-500.

Yager, J. A., West, A. J., Thibodeau, A. M., Corsetti, F. A., Rigo, M., Berelson, W. M., Bottjer, D. J., Greene, S. E., Ibarra, Y., and Jadoul, F., 2021, Mercury contents and isotope ratios from diverse depositional environments across the Triassic–Jurassic Boundary: Towards a more robust mercury proxy for large igneous province magmatism: Earth-Science Reviews, p. 103775.

 

How to cite: Edward, O., Paul, A. N., Bucher, H., Bagherpour, B., Baud, A., Adatte, T., Sonke, J., Schaltegger, U., and Vennemann, T.: Mercury isotope evidence for sustained regional volcanism in south China before and after the Permian-Triassic boundary, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8013, https://doi.org/10.5194/egusphere-egu22-8013, 2022.

EGU22-3986 | Presentations | SSP1.3

The record of the End Triassic Extinction in southern Tethyan carbonate platforms

Francesca Falzoni, Andrea Montanaro, Alessandro Iannace, and Mariano Parente

The End Triassic Extinction (ETE), one of the “big five” of the Phanerozoic, caused a severe loss of biodiversity both in the continental and in the marine realm. The ETE has been linked with enhanced volcanism of the Central Atlantic Magmatic Province (CAMP), which injected a large amount of CO2 in the ocean-atmosphere system, triggering major paleoenvironmental perturbations including climate change, ocean acidification and marine anoxia.

In the marine realm, shallow-water benthic biocalcifiers of subtropical carbonate platforms were severely affected, with reef-building scleractinian corals and calcisponges, large megalodontid bivalves, involutinid benthic foraminifers and dasycladalean algae being among the most famous victims. In the classical localities of the Northern Calcareous Alps and Transdanubian Range, the ETE coincides with the demise of the Dachstein-type carbonate platform, which is generally sharply overlain by relatively deep-water facies of outer ramp to basinal environment. This stratigraphy has been interpreted as recording subaerial exposure of the carbonate platform, associated to a sea-level drop in the late Rhaetian that generated a hiatus of variable and generally poorly constrained duration, followed by drowning during transgression in the Early Jurassic.

A different stratigraphic evolution is recorded in some areas of the southern Tethyan margin (i.e., the southern Apennines and Sicily in southern Italy, Greece, the United Arab Emirates and Oman) where carbonate platform facies persist across the Triassic/Jurassic boundary. Stratigraphic sections in these areas are particularly significant to document the evolution of biodiversity of shallow-water benthic biocalcifiers across the ETE interval.

In this study we present new data on the stratigraphic distribution and changes in abundance of benthic foraminifers in two latest Triassic–earliest Jurassic carbonate platform sections of the southern Apennines (Italy) and Pelagonian domain (Greece). We document a decline in diversity and abundance of involutinid benthic foraminifers predating the extinction of several genera in the latest Rhaetian. Carbon isotope profiles of the studied sections show a complicated pattern of repetitive high-frequency negative excursions, seemingly related to local paleoenvironmental and/or early diagenetic features. However, by integrating bio- and carbon isotope stratigraphy we are able to correlate the studied sections with other persistent carbonate platform sections and with reference sections of the Lombardy Basin and of the Northern Calcareous Alps.

How to cite: Falzoni, F., Montanaro, A., Iannace, A., and Parente, M.: The record of the End Triassic Extinction in southern Tethyan carbonate platforms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3986, https://doi.org/10.5194/egusphere-egu22-3986, 2022.

EGU22-4901 | Presentations | SSP1.3

Mercury anomaly as a proxy for volcanism in an isolated carbonate platform during the end-Triassic mass extinction

Andrea Montanaro, Francesca Falzoni, Alessandro Iannace, Thierry Adatte, and Mariano Parente

Massive release of volcanic gases into the ocean-atmosphere system during geologically short periods of time is often invoked as the main trigger of episodes of global paleoenvironmental perturbations, and a link has been proposed between some mass extinction events, OAEs and the activity of Large Igneous Provinces. However, establishing a precise correlation between sections where the volcanic deposits of LIPs are preserved and marine sections, which hold the key records of global biotic and paleoenvironmental changes, is not a trivial effort.  During the past 15 years, mercury concentration in sedimentary rocks has emerged as a useful proxy for bracketing intervals of LIPs activity, because Hg is primarily introduced into the atmosphere, and from there into the sedimentary record, through volcanic inputs. 
The end-Triassic extinction (ETE), one of the big five mass extinction of the Phanerozoic, has been linked to the volcanic activity of the Central Atlantic Magmatic Province (CAMP). Correlation by radiochronologic dating of CAMP basalts has been further supported in recent years by detection of mercury anomalies in marine deposits of key sections recording the ETE, including the Kuhjoch GSSP in the Northern Calcareous Alps (Austria), St Audrie’s Bay (UK) and the New York Canyon (Nevada, USA). However, as the Hg proxy is investigated in more and more sections, a complicated pattern is emerging, which indicates that depositional and diagenetic processes can produce Hg anomalies unrelated to LIP magmatism. For this reason, it is important to test the proxy across a wide range of depositional environments. 
In this study, we present a high-resolution record of Hg concentration in an uppermost Triassic-Lower Jurassic carbonate platform section of the Pelagonian Domain (Greece). In this section the ETE is marked by the abrupt disappearance of megalodontid bivalves and involutinid benthic foraminifers. By integrating bio- and high-resolution carbon isotope stratigraphy, we correlate the studied section with reference sections for which a record of Hg concentration across the ETE has been published. Furthermore, we use facies analysis and geochemistry to unravel the role of local depositional and diagenetic processes in overprinting the global signal of volcanism on Hg concentration.

How to cite: Montanaro, A., Falzoni, F., Iannace, A., Adatte, T., and Parente, M.: Mercury anomaly as a proxy for volcanism in an isolated carbonate platform during the end-Triassic mass extinction, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4901, https://doi.org/10.5194/egusphere-egu22-4901, 2022.

Direct evidence of intense chemical weathering induced by volcanism is rare in sedimentary successions. Here, we undertake a multiproxy analysis (including organic carbon isotopes, mercury (Hg) concentrations and isotopes, chemical index of alteration (CIA), and clay minerals) of two well-dated Triassic–Jurassic (T–J) boundary sections representing high- and low/middle-paleolatitude sites. Both sections show increasing CIA in association with Hg peaks near the T–J boundary. We interpret these results as reflecting volcanism-induced intensification of continental chemical weathering, which is also supported by negative mass-independent fractionation (MIF) of odd Hg isotopes. The interval of enhanced chemical weathering persisted for ~2 million years, which is consistent with carbon-cycle model results of the time needed to drawdown excess atmospheric CO2 following a carbon release event. Lastly, these data also demonstrate that high-latitude continental settings are more sensitive than low/middle-latitude sites to shifts in weathering intensity during climatic warming events. 

How to cite: shen, J.: Intensified continental chemical weathering and carbon-cycle perturbations linked to volcanism during the Triassic–Jurassic transition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3179, https://doi.org/10.5194/egusphere-egu22-3179, 2022.

EGU22-11901 | Presentations | SSP1.3 | Highlight

Chicxulub Impact’s Real Age & Mass Extinction’s Real Cause

Gerta Keller, Stephen Grasby, Hassan Khozyem, Jahnavi Punekar, Paula Mateo, and Thierry Adatte

After 42 years, the debate over the end-Cretaceous mass extinction still rages with arguments made for Chicxulub impact and Deccan volcanism as the real cause of this catastrophe. We briefly review the evidence for the pre-KPB age of the Chicxulub impact based on the primary impact spherule layer, which we link to Deccan volcanism based on the global mercury (Hg) fallout from Deccan eruptions. Mercury from volcanic eruptions is distributed around the world during its atmospheric residence time of 6 months to one year, after which it rains out over land and oceans. Major pulsed volcanic eruptions yield high Hg concentrations during fallout, which we termed Extreme Events (EE). We identified 20 of these Hg extreme events during the last 550 ky of the late Maastrichtian in sequences from Tunisia, Israel, Egypt and Mexico. At Elles, Tunisia, we dated these events (EE1 to EE20) based on orbital cyclicity and biostratigraphy with precision of one cycle (20 ky) with an error margin of 10-20 ky (Keller et al., 2020). We linked these dates to U-Pb zircon ages of the Deccan Traps with similarly high precision (Schoene et al., 2019). The resulting mercury stratigraphy yielded excellent age control linking Deccan eruption pulses across the globe. Results from two localities in NE Mexico revealed the Chicxulub impact crashed into Yucatan above the base of the Plummerita hantkeninoides zone CF1 and EE6 at about 200 ky prior to the KPB mass extinction. This deposit is unlike any other of the over 100 reworked spherule layers mixed with abundant shallow water debris. This oldest and primary impact spherule layer consists of compressed pure melt rock glass and glass spherules that settled rapidly to the deep seafloor. The environmental effects of this large impact were short-lived and caused no species extinctions. The effects of this 10 km-sized bolide impact had been vastly overrated.

The KPB mass extinction was identified between the longest lava flows across India to the Krishna-Godavari Basin and into the Bay of Bengal. Based on peak Hg fallout, we identified these volcanic eruptions as the largest most rapid sequence of pulsed events in Tunisia, Israel, Egypt and Mexico, all coinciding with the rapid mass extinction observed in India. The mass extinction began with the onset and ramp-up of pulsed Deccan eruptions resulting in toxic and acidic waters that caused 50% species extinctions. Extremely rapid large pulsed eruptions followed and resulted in the longest lave flows and hyperthermal warming that caused the rapid demise of all but one species, the disaster opportunist Guembelitria cretacea. Deccan eruptions quickly diminished after the mass extinction and climate cooled rapidly giving rise to the first new species. Volcanic eruptions remained low and cool temperatures persisted through the early Paleocene interrupted by a smaller eruption phase about 100 ky after the mass extinction.  These data reveal that Deccan volcanism caused the KPB mass extinction without any extraterrestrial aid.

Keywords: Chicxulub, Deccan Volcanism, Mass Extinction, Mercury Stratigraphy, Age control

 

How to cite: Keller, G., Grasby, S., Khozyem, H., Punekar, J., Mateo, P., and Adatte, T.: Chicxulub Impact’s Real Age & Mass Extinction’s Real Cause, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11901, https://doi.org/10.5194/egusphere-egu22-11901, 2022.

EGU22-6736 | Presentations | SSP1.3

Evidence of high effusion Deccan volcanism proceeding the KPg boundary at Elles, Tunisia

Steffanie Sillitoe-Kukas, Munir Humayun, Thierry Adatte, and Gerta Keller

Massive volcanic eruptions of the Deccan coincided with the end-Cretaceous mass extinction. Precisely dating when the most intense eruptions occurred is challenging because the resolution of geochronological techniques does not yet resolve events shorter than 20 kiloannum (ka). Volcanic eruptions outgas volatile metals, e.g., Cd, Te and Hg, along with SO2 and other gases that may have contributed to high-stress environments for planktic foraminifera the 200 ka preceding the end-Cretaceous. Trace metals like Cd accumulate in sediments by deposition of aerosols, where the excess Cd reflects the intensity of volcanic emissions. Models show high frequency, low effusion rate eruptions result in low Cd enrichments, whereas low frequency, high effusion rate eruptions, the type likely to lead to deadly consequences, result in high enrichments of Cd within the sediments. The KPg section at Elles represents a middle neritic depositional environment with an average sedimentation rate of 4.7 cm/1,000 years for the late Maastrichtian. A series of sediment samples (marly limestone to shale) were taken from about 1 meter above the boundary to about 15 meters below the boundary. Elemental compositions of sediments (50 elements) were obtained by solution ICP-MS. Cadmium abundances ranged from values close to upper continental crust (UCC) to values approximately eight times higher. Such high enrichments were found in sediments from the 100 ka period preceding the boundary corresponding to the Poladpur phase of Deccan volcanism. A lack of correlation between Zn, P2O5, and Mo below the boundary suggest the Cd enrichments are not from an influx of biogenic detritus or TOC burial. Above the boundary, there is a 25 ka period of normal shale Cd values interpreted here to represent the period between the Ambenali and Poladpur phases. We have previously shown from the neighbouring El Kef section, representing ~ 10 ka, that Cd and Re are correlated in proportions similar to those from intraplate volcanoes. The Cd data for Elles complement Te and Hg data, all of which demonstrate the presence of volcanogenic trace metals over most of the period of the Poladpur phase of the Deccan eruption. Cadmium as a tracer enables better correlation between foram-based chronology and intense pulses of the Deccan eruption. The data obtained thus far confirm that the period prior to the extinction was dominated by intense volcanism followed by relative quiescence during the earliest Danian recovery with important implications for the cause of the extinction.

How to cite: Sillitoe-Kukas, S., Humayun, M., Adatte, T., and Keller, G.: Evidence of high effusion Deccan volcanism proceeding the KPg boundary at Elles, Tunisia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6736, https://doi.org/10.5194/egusphere-egu22-6736, 2022.

EGU22-7033 | Presentations | SSP1.3

Linking the Deccan lava stratigraphy with the end-Cretaceous extinction and impact – new insights from Rajahmundry

Patrick Hoyer, Marcel Regelous, Thierry Adatte, and Karsten Haase

The Deccan flood basalt province in India was erupted within < 1 Myr and overlaps in age with the Cretaceous-Paleogene boundary (KPB) extinction event, and the Chicxulub impact in Mexico. Consequently, the role of Deccan volcanism in the KPB extinction is debated, and it has also been proposed that the Chicxulub impact triggered the largest Deccan lava formations (Poladpur, Ambenali and Mahabaleshwar (PAM)), which represent approximately 70% by volume of the total Deccan and may have been erupted within 500,000 years. Recent geochronological data studies debate whether the onset of the PAM eruptions began at the KPB as consequence of the Chicxulub impact, or whether the PAM lavas were erupted in several pulses, beginning several tens of thousands of years before the KPB (e.g., Sprain et al. 2019, Schoene et al., 2019).

The Rajahmundry Traps on the eastern side of India are believed to represent either the distal ends of voluminous Ambenali and Mahabaleshwar lava flows (e.g., Baksi et al. 1994), or lavas which were erupted locally through fault-controlled fissures unrelated to Deccan volcanism (Manikyamba et al. 2015). In contrast to lavas of the Main Deccan Province, the three separate lava flow units at Rajahmundry are interbedded with sediments, which constrain their age relative to the KPB (Keller et al. 2008; Fendley et al. 2020).

Here we present new major and trace element data for lavas from Rajahmundry and from the Main Deccan Province, and correlate the lavas from Rajahmundry with the younger formations of the Deccan Traps using machine learning algorithms. We find that flows of the Poladpur (lower flow), Ambenali (middle flow) and Mahabaleshwar (upper flow) formations are all present at Rajahmundry, confirming these as an eastward extension of the Deccan Traps. The geochemical classification is consistent with published paleomagnetic and geochronological data for these lavas. Our study shows that some Poladpur lava flows were of sufficient volume and were erupted rapidly enough to flow approximately 1000 km across the Indian subcontinent. The ages of sediments at Rajahmundry imply that eruption of the Poladpur Formation and thus the onset of voluminous PAM volcanic activity began close to the KPB (and Chicxulub impact), and at least the youngest Poladpur flows were emplaced in the Danian.

How to cite: Hoyer, P., Regelous, M., Adatte, T., and Haase, K.: Linking the Deccan lava stratigraphy with the end-Cretaceous extinction and impact – new insights from Rajahmundry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7033, https://doi.org/10.5194/egusphere-egu22-7033, 2022.

EGU22-11928 | Presentations | SSP1.3

40Ar/39Ar dating of the Malwa Plateau subprovince, Deccan Traps, India

Andrew Tholt, Paul Renne, Loÿc Vanderkluysen, Kanchan Pande, Dhananjay Mohabey, and Anup Dhobale

Our systematic study of the spatial-temporal evolution of magmatism in the Deccan Traps   Large Igneous Province provides new data from the Malwa Plateau(MP) subprovince, which lies north of the comparatively well-studied Western Ghats. 40Ar/39Ar analysis was performed by incremental laser heating of multigrained plagioclase aliquots, in multiple (typically 4) experiments per sample.  Achievable precision is strongly anticorrelated with Ca/K of the plagioclase, reaching ~0.1% (pooled plateau ages, 1 s.d. intralaboratory precision) for some samples with Ca/K< 80. Results have been obtained from samples between ~100-800 m elevation, spanning virtually the entire exposed stratigraphy of the MP. Most of the MP overlaps in age with the older Kalsubai and Lonavala subgroups (~66.3 to 66.0 Ma) of the Western Ghats(WG), but MP basalts do not align with traditional WG chemical stratigraphy suggesting multiple contemporaneous eruptive centers and magma systems. The lowest (134 masl) lava dated is 66.8 ±0.07 Ma, significantly older than anything yet dated in the WG but identical to the result of Schöbel et al. (2014) for a stratigraphically low lava elsewhere in the MP. This is consistent with the consensus that the inception of volcanism progressed generally from North to South. Collectively, our data indicate a much slower mean lava accumulation rate for the basal MP, increasing sharply from 66.4 to 66.2 Ma and slowing by the Cretaceous-Paleogene boundary (KPB). MP lava accumulation rates decrease around the time of the KPB coincident with when eruption rates are inferred to increase in the WG. At similar elevations, our results overlap with the age model presented by Eddy et al. (2020) based on U/Pb dating of zircons from presumed silicic ashes preserved in red boles between lava flows, however our data span about twice their elevation range encompassing the lower portions of the section where we obtained the oldest ages. Our results indicate that the peak lava extrusion in the MP coincided closely with the Late Maastrichtian Warming Event (Barnet et al., 2017).

How to cite: Tholt, A., Renne, P., Vanderkluysen, L., Pande, K., Mohabey, D., and Dhobale, A.: 40Ar/39Ar dating of the Malwa Plateau subprovince, Deccan Traps, India, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11928, https://doi.org/10.5194/egusphere-egu22-11928, 2022.

EGU22-2261 | Presentations | SSP1.3

Timing and Tempo of Deccan volcanism relative to the KPg extinction revealed by Mercury and Tellurium anomalies

Thierry Adatte, Marcel Regelous, Eric Font, Jorge E. Spangenberg, Gerta Keller, Uygar Karabeyoglu, Paula Mateo, Jhanavi Punekar, and Syed Khadri

EGU22-10083 | Presentations | SSP1.3

On Planktic Foraminifera Calcification Crisis in the Deccan Benchmark Interval of Bidart, France

Jahnavi Punekar, Subham Patra, and Gerta Keller

The Late Maastrichtian Deccan volcanic pulses contributed to a cumulative biotic stress that set the stage for the Cretaceous-Palaeogene boundary (KPB) mass extinction. The high-flux emissions of volcanogenic CO2 and SO2 into the atmosphere likely led to ocean acidification. The resultant carbonate crisis has been hypothesized as a key stressor for marine calcifying biota such as planktic foraminifera. The final ~50 ky of the Cretaceous at Bidart (France) record a unique concurrence of anomalous bulk-rock low magnetic susceptibility, high Hg/TOC, and high planktic foraminifera fragmentation index. This study documents new evidence of a biological (calcification) crisis in the geochemical and taphonomic Deccan benchmark interval.

The onset of the hypothesized acidification interval (~0.5 m below KPB) coincides with abrupt changes in the relative abundances of the heavily calcified globotruncanid (~30 to ~17%) and larger biserial tests (~38 to ~55%). The absolute abundances of target groups/species however show a marked decline in both the biserials and globotruncanids. The counts per gram within the benchmark fluctuate considerably. At the KPB, the relative abundances of robust tests are high, partly due to taphonomic overestimation. However, absolute abundances unequivocally show a decline in all analyzed groups e.g., globotruncanids, biserials, racemiguembelinids and Planomalina brazoensis. The benchmark interval also records smaller-than-average test sizes of Globotruncana arca, Globotruncana mariei, Heterohelix globulosa, Pseudoguembelina hariaensis, Pseudotextularia elegans, Pseudoguembelina carsayae, Pseudoguembelina palpebra, Rugoglobigerina rugosa and P. brazoensis, indicating intraspecific dwarfing. This same interval also records a measurable decrease in the test-wall thickness amongst adult (>150 µm) specimens of H. globulosa, R. rugosa, P. elegans, P. brazoensis, further substantiating a carbonate crisis. The interpolation of geochemical, taphonomic and the new biological evidences strongly validate an ocean acidification event spanning ~50 ky preceding the KPB, a duration more consistent with Deccan volcanism as the cause.

How to cite: Punekar, J., Patra, S., and Keller, G.: On Planktic Foraminifera Calcification Crisis in the Deccan Benchmark Interval of Bidart, France, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10083, https://doi.org/10.5194/egusphere-egu22-10083, 2022.

Deep-water agglutinated foraminifera (DWAF) are investigated from the lower Paleocene of the Contessa Highway section in the Umbria-Marche Basin in Italy. In the lowermost meter of the Paleocene, corresponding the P0, Pa, and lowermost P1 planktonic foraminifera zones, a total of 46 species of DWAF are observed. A comparison with the uppermost Maastrichtian DWAF assemblages documented by Cetean (2009) yields a combined total of 94 DWAF species over the Cretaceous/Paleogene boundary interval at Contessa Highway. Of these, 49 species are listed as extinction taxa, nine are survivor taxa, 19 are Lazarus taxa, and 17 taxa display first occurrences in the Paleocene.

The record of DWAF in the Contessa Highway section displays a moderate decrease in diversity across the K/Pg boundary, followed by a gradual recovery in the first meter of the Paleocene. The lower Paleocene record is characterized by blooms of opportunistic species belonging to the genera Reophax, Subreophax, Repmanina, and Spiroplectinella. The K/Pg boundary interval records a major change in the proportions of DWAF morphogroups, from a suspension-feeding community in the Maastrichtian to one dominated by epifaunal detritivores in the lower Paleocene, reflecting a fundamental change in the nature of marine primary productivity following the bollide impact. 

How to cite: Kaminski, M., Hikmahtiar, S., and Cetean, C.: Deep-Water Agglutinated Foraminifera from the Contessa Highway Section, Umbria-Marche Basin, Italy: Assemblage turnover at the Cretaceous/Paleogene Boundary, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9536, https://doi.org/10.5194/egusphere-egu22-9536, 2022.

EGU22-3162 | Presentations | SSP1.3

Lithospheric and Atmospheric Changes Associated with Rapid, Pulsed Assembly of Mafic Upper Crust: Assembly of the Karoo LIP Intrusive Complex

Sean P. Gaynor, Lars Augland, Henrik H. Svensen, and Urs Schaltegger

Large Igneous Provinces (LIPs) are commonly correlated with global climate change, and environmental, as well as biological, crises. These are short-lived igneous events, typically much less than 5 Ma, can erupt more than 1 Mkm3 of volcanic rocks, while potentially emplacing over 500,000 km3 of upper crustal intrusions. As a result, LIPs represent some of the most rapid periods of lithospheric growth, generating enormous volumes of mafic upper crust. Detailing the duration and pace of these high flux magmatic events has, however, is hampered by a lack of high-precision geochronology. We focus on the Karoo LIP in southern Africa as a natural laboratory for testing models on the formation of mafic upper crust through large-volume mafic LIP intrusions. The Karoo LIP is comprised of a suite of basaltic lava flows, sills, dike swarms, and was emplaced during the early Toarcian. Approximately 340,000 km3 of sills are interlaid within Karoo Basin sedimentary rocks. Differential uplift, erosion and availability of drill core material allows for sampling of the entire intrusive succession in the basin.

We report new high-precision U-Pb zircon and baddeleyite ages, Hf isotope compositions and apatite volatile compositions from sills emplaced from base to top of the Karoo Basin. Using these data, we are able to address several fundamental questions of LIP emplacement: (1) what is the total of intrusive LIP magmatism within the Karoo Basin; (2) is there variable magma flux during assembly of the intrusive complex; (3) is there is a relationship between age and structural position of sills within the basin; (4) is it justified to correlate the intrusion of the LIP with global climate change at this level of precision; (5) does the composition and extent of thermogenic degassing vary throughout the basin?

Our new data indicate that the 340,000 km3 of intrusive magmas were emplaced in approximately 500 kyr, solidifying new mafic upper crust through a downward stacking assembly, and that the entirety of intrusive magmas were emplaced within the uncertainty of the early Toarcian oceanic anoxic event. This pulsed assembly is in agreement with atmospheric models that require pulsed degassing of the basin to cause the observed early Toarcian isotope excursions. In addition, these data also indicate that dolerite sills throughout the basin assimilated sedimentary wall rock during crystallization, which helped facilitate zircon crystallization within pegmatitic pods interfingered within the sills. Finally, volatile compositions preserved in apatite indicate that thermogenic wallrock-sill interactions significantly affected the final volatile compositions of the sills, and trace the release of LIP-driven gases from the basin.

How to cite: Gaynor, S. P., Augland, L., Svensen, H. H., and Schaltegger, U.: Lithospheric and Atmospheric Changes Associated with Rapid, Pulsed Assembly of Mafic Upper Crust: Assembly of the Karoo LIP Intrusive Complex, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3162, https://doi.org/10.5194/egusphere-egu22-3162, 2022.

EGU22-779 | Presentations | SSP1.3

Osmium-isotope records of volcanism and weathering before and during the Valanginian Weissert Event

Lawrence Percival, Dave Selby, Stuart Robinson, Steven Goderis, and Philippe Claeys

The Valanginian Weissert Event (~134 Ma) represented the first major carbon-cycle disturbance of the Cretaceous Period, characterized in the sedimentary record by a prolonged positive excursion in carbon-isotope ratios. The event has been widely linked with climate cooling, documented in several geographic regions; however, some areas show minimal evidence of temperature change at that time, or even warming and enhanced humidity around the onset of the event. Moreover, although the carbon-isotope excursion has generally been attributed to enhanced burial of organic matter, there is no evidence of widespread marine anoxia that would have promoted such deposition. Consequently, key questions remain regarding the causes of climate and environmental degradation during the early Valanginian. Understanding changes in volcanic activity and silicate weathering rates through late Berriasian to early Valanginian times is crucial for resolving this debate, as both processes influence atmospheric pCO2 levels and global temperatures. In particular, volcanism associated with formation of the Paraná-Etendeka large igneous province (LIP) during the Valanginian has long been proposed as the ultimate trigger of the Weissert Event via carbon emissions and greenhouse warming,but weathering of juvenile LIP basalts could equally have caused climate cooling.

In this study, we investigated the osmium-isotope composition (187Os/188Os) of deep-marine organic-rich Berriasian–Valanginian sediments from two proto-Atlantic Ocean archives (DSDP sites 534 and 603). Given the palaeoenvironmental setting of the two sites, the recorded 187Os/188Os seawater compositions of the proto-Atlantic should be representative of the global ocean. We find that seawater 187Os/188Os shifted from ~0.6 to ~0.75 during the latest Berriasian, suggestive of an increased flux of radiogenic osmium to the ocean during that time, likely resulting from enhanced weathering of the continental crust. Interestingly, however, there is no evidence of global climate warming during the late Berriasian that would have caused this weathering. Following the late Berriasian radiogenic shift, seawater osmium gradually changed to a more unradiogenic isotopic composition (~0.45) during the early Valanginian; the lowest 187Os/188Os values correlating with both the peak in the Weissert Event carbon-isotope excursion and evidence for climate cooling. This unradiogenic shift could reflect a decline in weathering of radiogenic crustal material; however, it also stratigraphically correlates with geochronological and geochemical evidence for the time of maximum igneous activity on the western (Paraná) part of the Paraná-Etendeka LIP. Therefore, we conclude that the early Valanginian shift to unradiogenic 187Os/188Os seawater compositions resulted from erosion of juvenile primitive basalts, suggesting that combined weathering of the continental crust and the Paraná-Etendeka LIP played a key role in causing the global cooling associated with the Weissert Event.

 

How to cite: Percival, L., Selby, D., Robinson, S., Goderis, S., and Claeys, P.: Osmium-isotope records of volcanism and weathering before and during the Valanginian Weissert Event, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-779, https://doi.org/10.5194/egusphere-egu22-779, 2022.

EGU22-3366 | Presentations | SSP1.3

Deciphering the global onset of Oceanic Anoxic Event 2 (OAE2) in the mid-Cretaceous greenhouse world

Yong-Xiang Li, Xinyu Liu, David Selby, Zhonghui Liu, Isabel Montañez, and Xianghui Li

The mid-Cretaceous (~120 Ma to ~90 Ma) is a well-known greenhouse period in the Earth’s history that was punctuated by multiple dramatic paleoceanographic changes known as oceanic anoxic events (OAEs). Among these OAEs, OAE2 occurred near the Cenomanian-Turonian boundary (CTB, ~93.9 Ma) and represents one of the most pronounced OAEs. OAE2 is widely believed to be triggered by submarine volcanism, primarily based on proxy records from the Northern Hemisphere in which a large osmium isotope excursion indicative of volcanism precedes the carbon isotope excursion (CIE) of OAE2. However, the timing and mechanism of the global initiation of OAE2 remain elusive in part due to the lack of detailed osmium-isotope proxy records across the OAE2 intervals in the Southern Hemisphere. Here we report a high-resolution initial osmium isotope (187Os/188Osi, Osi) and δ13Corg record from a highly expanded OAE2 interval in southern Tibet, China that was deposited in the northern margin of India Plate in eastern Tethys in the Southern Hemisphere. The Osi record documents three distinct Osi shifts toward unradiogenic compositions with increasing amplitudes at ~95.1 Ma, ~94.8 Ma, and ~94.5 Ma, respectively, indicating episodic, intensifying volcanism with the highest intensity episode at ∼94.5 Ma. In addition, the large Osi excursion at ~94.5 Ma is followed by an ∼200 kyr Osi minimum concomitant with a cooling interval as revealed by an overall broad minimum interval of the difference of the paired δ13Ccarb and δ13Corg. This cooling interval is broadly synchronous with the Plenus Cold Event (PCE) recorded in the Northern Hemisphere. Furthermore, the large Osi excursion paradoxically lags the onset of OAE2 by ∼50 kyr at the Tibetan section. Comparison with and re-examination of the expanded OAE2 record of the Yezo Group (Japan) and those from the western interior seaway (WIS) in North America reveal the regional difference in the phasing relationship between the large Osi excursions and the CIEs of OAE2. Intriguingly, the large Osi excursions occurred during a near synchronous global transgression at ~94.5 Ma that led to increased connectivity of global oceans. Taken together, these results suggest that enhanced ocean connectivity was essential in helping trigger the global onset of OAE2 at ~94.5 Ma.

How to cite: Li, Y.-X., Liu, X., Selby, D., Liu, Z., Montañez, I., and Li, X.: Deciphering the global onset of Oceanic Anoxic Event 2 (OAE2) in the mid-Cretaceous greenhouse world, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3366, https://doi.org/10.5194/egusphere-egu22-3366, 2022.

EGU22-377 | Presentations | SSP1.3

Geochemical and mineralogical investigations of the Bonarelli level (Gubbio, Italy): evidence of Hg anomalies

Giulia Marras, Marco Brandano, Laura Tomassetti, Guia Morelli, Valentina Rimondi, Luca Aldega, Marino Domenico Barberio, Nereo Preto, and Vincenzo Stagno

The emissions of volcanic gases over the Earth’s history have played a major role in changing the chemistry of the terrestrial atmosphere with implications for life development and sustainability (Kasting and Catling 2003). Sedimentary rocks record geological processes that occurred at the interface between water and/or surface and atmosphere such as volcanic eruptions and other (extra)terrestrial catastrophic events. In the last decade, anomalous concentrations of mercury (Hg) in the sedimentary record have been used as a global tracer of extensive volcanism, although other sources of Hg must be taken into account as massive wildfires and continental weathering (Grasby et al. 2019). In this ongoing study, we aim at establishing the relation between geochemistry and mineralogy to explain the occurrence of Hg anomalies in sedimentary rocks distributed at regional scale. We investigated the Bonarelli level, a 0.87-m thick layer made of organic-rich shales, that outcrops at Valle della Contessa section in Gubbio (Italy). This layer records the Oceanic Anoxic Event 2 (OAE2; Cenomanian-Turonian, ~93 Ma), an event likely triggered by submarine volcanic emission of High Arctic and Caribbean large igneous provinces (Turgeon and Creaser 2008).

We collected rock samples from ~1 m below up to ~1 m above the Bonarelli level every 5 to 10 cm including the confining limestones. Measurements of absolute Hg concentrations were performed using the Direct Mercury Analyzer (DMA-80 Tricell) and combined with the mineralogical abundance at each layer determined by X-ray diffraction (XRD). Additional measurements were carried out to determine the concentrations of trace elements using the inductively coupled plasma-mass spectrometry (ICP-MS). Analyses of δ13C and total organic carbon (TOC) were also performed on the collected samples.

Preliminary results show low Hg concentrations measured in the limestones less than 20 μg/kg, but anomalous high contents up to ~1600 μg/kg within the Bonarelli level. These high Hg concentrations correlate positively with chalcophile elements such as Cu, Ni and Fe. XRD semi-quantitative analysis show that oxidized (barite, jarosite) and reduced (pyrite) S-bearing minerals are among the minerals occurring in the Bonarelli level that, along with the organic matter, are good candidates to host the Hg released to the atmosphere by extensive volcanic eruptions.

Kasting, J. F., & Catling, D. 2003. Annual Review of Astronomy and Astrophysics, 41(1), 429-463.

Grasby, S. E et al. 2019. Earth-Science Reviews, 196, 102880.

Turgeon, S. C., & Creaser, R. A. 2008. Nature, 454(7202), 323-326.

How to cite: Marras, G., Brandano, M., Tomassetti, L., Morelli, G., Rimondi, V., Aldega, L., Barberio, M. D., Preto, N., and Stagno, V.: Geochemical and mineralogical investigations of the Bonarelli level (Gubbio, Italy): evidence of Hg anomalies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-377, https://doi.org/10.5194/egusphere-egu22-377, 2022.

EGU22-12380 | Presentations | SSP1.3

Project PORO-CLIM initial results: Towards a new oceanic crustal record of magma productivity throughout initiation of the North Atlantic Igneous Province 

Hazel Knight, Stephen M Jones, John R Hopper, Brian M O'Reilly, and Thomas Funck

In May 2021 project PORO-CLIM acquired a new geophysical dataset across the little studied Porcupine and Rockall Plateau passive margins in the Northeastern Atlantic. The project aims to study the initiation of the North Atlantic Igneous Province (NAIP) and test its relationship with the Palaeocene-Eocene Thermal Maximum (PETM) global climate change event. Profile 1, a 400 km long deep seismic (MCS and OBS) profile, contains a continuous latest-Cretaceous to early-Eocene oceanic crustal thickness record that spans the entire emplacement of the NAIP. Oceanic crustal thickness can be directly interpreted as a record of magma productivity and hence mantle temperature. As such Profile 1 encodes the first continuous, sub-million year record of the entire waxing and waning cycle of mantle temperature during the initiation of any of the world’s Large Igneous Provinces.

Thermogenic methane produced by shallow igneous sills within the NAIP sill province and released to the atmosphere through hydrothermal vent systems, together with the carbon dioxide released from the magma itself, are the most likely carbon sources for the PETM [1]. Profile 1 is the first whole crustal seismic record across Eriador Ridge, thought to be the thick oceanic crustal trace of the pulse of anomalously hot mantle which drove the pulse of melting which led to NAIP sill province emplacement. Thus the magma productivity record derived from Profile 1 will ultimately help constrain the rate of NAIP thermogenic carbon emissions, further testing the link between NAIP sills and the PETM. This presentation will outline the initial findings from seismic data analysis, including a preliminary magma production record spanning NAIP initiation and the relationship between magma productivity and the PETM. Initial analysis of relative changes in crustal thickness across the record suggest that long-term (>5 My) magma productivity increased from late Cretaceous to early Eocene time, whilst short term (<5 My) magma productivity became more pulsed. The new dataset also shows Eriador Ridge contains a previously unknown double peak in magma productivity. These peaks may potentially be the result of two distinct pulses of anomalously hot mantle, separated by c. 1 Myr, which could imply multiple bursts of gas release from the NAIP around the Palaeocene-Eocene boundary.

[1] Jones, S.M., Hoggett, M., Greene, S.E. and Jones, T.D. Large Igneous Province thermogenic greenhouse gas flux could have initiated Paleocene-Eocene Thermal Maximum climate change. Nat. Commun. 10, 5547 (2019).

How to cite: Knight, H., Jones, S. M., Hopper, J. R., O'Reilly, B. M., and Funck, T.: Project PORO-CLIM initial results: Towards a new oceanic crustal record of magma productivity throughout initiation of the North Atlantic Igneous Province , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12380, https://doi.org/10.5194/egusphere-egu22-12380, 2022.

EGU22-4194 | Presentations | SSP1.3

Paleocene stage boundaries and hyperthermal events (Wadi Nukhul and Gebel El Beida, Egypt): a possible link to global volcanism

Hassan Khozyem, Abdullah Mahmoud, Thierry Adatte, Gerta Keller, and Jorge Spangenberg

SSP2.1 – Phanerozoic stratigraphy, paleoceanography, and paleoclimate

EGU22-9361 | Presentations | SSP2.1 | Highlight

“climatearchive.org”: 540 million years of climate data at your fingertips

Sebastian Steinig, Tessa Alexander, Dan Lunt, Paul Valdes, Zak Duggan, Patrick Lee, Jakub Navratil, Ikenna Offokansi, and Matthew Swann

We can only fully understand the past, present and future climate changes by bringing together data and process understanding from a broad range of environmental sciences. In theory, climate modelling provides a wealth of data of great interest to a wide variety of disciplines (e.g., chemistry, geology, hydrology), but in practice, the large volume and complexity of these datasets often prevent direct access and therefore limit their benefits for large parts of our community.

We present the new online platform “climatearchive.org” to break down these barriers and provide intuitive and informative access to paleoclimate model data to our community. The current release enables interactive access to a recently published compilation of 109 HadCM3BL climate model simulations. Key climate variables (temperature, precipitation, vegetation and circulation) are displayed on a virtual globe in an intuitive three-dimensional environment and on a continuous time axis throughout the Phanerozoic. The software runs in any web browser — including smartphones — and promotes data exploration, appeals to students and generates public interest.

We also show current work on the next phase of the platform, which aims to develop new tools for integration into a more quantitative research workflow. These include easy online generation and download of maps and time series plots of the underlying monthly model data. The data can also be exported as global fields or CSV files for any user-selected location for further offline analysis, such as use in spreadsheets. Finally, we will discuss and outline future integration of new sources of model and geochemical proxy data to simplify and advance interdisciplinary paleoclimate research.

How to cite: Steinig, S., Alexander, T., Lunt, D., Valdes, P., Duggan, Z., Lee, P., Navratil, J., Offokansi, I., and Swann, M.: “climatearchive.org”: 540 million years of climate data at your fingertips, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9361, https://doi.org/10.5194/egusphere-egu22-9361, 2022.

EGU22-6334 | Presentations | SSP2.1

CycloNet: European Cyclostratigraphy Network

Philippe Claeys, Matthias Sinnesael, David De Vleeschouwer, and Christian Zeeden

The study of astronomical climate forcing and the application of cyclostratigraphy experienced a spectacular growth over the last decades. In 2018, the first Cyclostratigraphy Intercomparison Project (CIP) workshop constituted the first attempt to compare different methodological approaches and unite the global community around standard, uniform and reliable procedures. Two major conclusions were: [1] There is a need for further organization of the cyclostratigraphic community (e.g. to streamline different methodologies); [2] Cyclostratigraphy is a trainable skill, but currently many universities lack specific resources for training and education. Today, a regular newsletter, a dedicated free open-access journal “Cyclostratigraphy and Rhythmic Climate Change (CRCC)”, a scientific podcast titled CycloPod, and an educational website “www.cyclostratigraphy.org” connect the cyclostratigraphy community. The newly created CycloNet (Research Foundation Flanders FWO Funding) expands this effort into a real and sustainable scientific research network with partners from all around Europe, and open to the global community. At the same time, CycloNet creates a platform for streamlining and integrating new multi-disciplinary approaches. The main scientific targets for CycloNet in the next five years are: [1] Set up a diverse and sustainable community structure, relying on exchange, interaction and training, [2] Boost research by novel methodological approaches applying advanced signal processing techniques, [3] Organize a second Cyclostratigraphic Intercomparison Project. With this poster, we reach out to the broader community to exchange ideas on concepts and activities that CycloNet can help to develop further towards the future.

How to cite: Claeys, P., Sinnesael, M., De Vleeschouwer, D., and Zeeden, C.: CycloNet: European Cyclostratigraphy Network, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6334, https://doi.org/10.5194/egusphere-egu22-6334, 2022.

The Cambrian Explosion is a fundamental turning point in the evolution of life that occurred during the Cambrian Period (~541 to ~485 million years ago), which involved the origination and explosive radiation of all major animal phyla. The bursts of evolution characterizing this period appear concurrently with major modifications to the physico-chemical conditions of the world’s oceans, and are recorded in critical fossil localities where soft-tissues are exceptionally well preserved, including Lagerstätten such as the Burgess Shale and Chengjiang Biota. As a result of the severe lack of biostratigraphically-correlatable fossils (due to widespread endemism during the Cambrian) and sparse high-precision radioisotopic dates, the Cambrian time scale remains among the least defined stage of all the Phanerozoic Eon, with a minimum uncertainty of ±2 million years at its stage boundaries. The absence of a high-resolution geological time scale for the Cambrian Explosion hampers our ability to robustly address widely debated questions concerning the origins and rates of the evolutionary and ecological events, their relationship with paleoceanographic conditions, their responses to astronomically-forced climate change, including from Milankovitch “grand” cycles, and whether these events were globally synchronous.

Using an integrated set of geophysical/chemical proxies with advanced time series techniques on selected stratigraphic sections, this project aims at (1) Generate sets of high- resolution geophysical and geochemical stratigraphic proxies enabling to capture Milankovitch forcing within the selected sedimentary records, (2) Building a high-resolution time scale to improve our knowledges on the timing of major Cambrian evolutionary milestones and geochemical changes and (3) Determine the relationships between Cambrian evolutionary and ecological events with the paleoceanographic changes and Milankovitch cycles.

How to cite: Pas, D., Jamart, V., and Daley, A.: Generating a highly resolved astronomical time scale for the evolutionary and ecological events during the Cambrian Explosion, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12868, https://doi.org/10.5194/egusphere-egu22-12868, 2022.

EGU22-3197 | Presentations | SSP2.1

Synchronizing Rock Clocks in the Late Cambrian

Zhengfu Zhao, Nicolas Thibault, Tais W. Dahl, Niels H. Schovsbo, Aske L. Sørensen, Christian M.Ø. Rasmussen, and Arne T. Nielsen

The Cambrian is the most poorly dated period of the past 541 million years of Earth history. This hampers analysis of profound environmental and biological changes that took place during this period. Astronomically forced climate cycle recognized in sediments and anchored to radioisotopic ages provides a powerful geochronometer that has fundamentally refined Mesozoic–Cenozoic time scales but not yet the Palaeozoic. Here we report a continuous astronomical signal detected as geochemical variations (1 mm resolution) in the late Cambrian Alum Shale Formation that is used to establish a 16 Myr-long astronomical time scale, anchored by radioisotopic dates. The resulting time scale is biostratigraphically well-constrained, allowing correlation of the late Cambrian global stage boundaries with a 405-kyr astrochronological framework. This enables a first assessment, in numerical time, of the evolution of major biotic and abiotic changes, including the end-Marjuman extinction and the Steptoean Positive Carbon Isotope Excursion, that characterized the late Cambrian Earth.

How to cite: Zhao, Z., Thibault, N., W. Dahl, T., H. Schovsbo, N., L. Sørensen, A., M.Ø. Rasmussen, C., and T. Nielsen, A.: Synchronizing Rock Clocks in the Late Cambrian, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3197, https://doi.org/10.5194/egusphere-egu22-3197, 2022.

EGU22-8721 | Presentations | SSP2.1

Semi-3D stratigraphic architecture of a siliciclastic shallow-marine platform: Insights from the Ktawa Group (Late Ordovician) in Morocco

Déborah Harlet, Guilhem Amin Douillet, Jean-François Ghienne, Pierre Dietrich, Chloé Bouscary, Philippe Razin, and Fritz Schlunegger

A semi-3D stratigraphic architecture of the Lower Ktawa Group, deposited during the early Late Ordovician on the northern Gondwana platform in a shallow marine environment, was investigated in the Anti-Atlas. The logging of 42 sections reveals that the Lower Ktawa is dominated by shales, punctuated by fine to coarse sandstones forming successive cuestas. Here, focus is put on three main sand cuestas recording major sea-level drops.

The lowermost cuesta (Foum-Zguid Member) outcrops along >85 km, and dips southward. Three facies associations albeit with complex lateral relationships were distinguished: 1. In the West, coarse-grained cross-bedded sandstones. 2. In the central part, sandstones dominated by Hummocky-Cross-Stratifications (HCS), in amalgamated beds towards the West but isolated within shales towards the East. 3. In the East, dominance of highly bioturbated sandstones. A second cuesta (“Tissint Member”) outcrops exclusively on the western part of the transect, approximately 25-50 m above the Foum-Zguid cuesta, and also dips South-southwestward. This 40 m-thick sandstone complex has a sharp base and is composed of fine to coarse cross-bedded sandstones. At its northeastern limit, the 40 m-thick succession disappears within 3.5 km. The upper cuesta (Bou-Hajaj Member, 5-40 m thick) is found ca.160 m above the base of the Ktawa Group and outcrops in the eastern zone of the study area. Its southern part is characterized by the thickest stack of sandstones, organized in a shallowing upward trend, and comprises HCS-beds and channelized structures a few meters in width. The eastern part is dominated by coarse, bioturbated, cross-bedded sandstones lacking shallowing upward stacking patterns. Its dip is northward, in the opposite direction to the underlying two members. Moreover, from satellite images, a clinothem dipping towards the Northeast is identified, together with the dissociation of the cuesta in two sets pinching out northwestward.

On a regional scale, the directly underlying First Bani Group was reconstructed as a shallow shelf having a northward oriented proximal-to-distal trend (Marante, 2008). A study of the Ktawa Group ca. 200 km Northeast of our study zone evidenced a southwestward proximal-to-distal trend (Meddour, 2016). Furthermore, a regional depocenter of the Ktawa Group is generally thought to occur eastward from our study.

Three interpretation lines are considered to reconcile these apparently contradictory observations: 1. A locally eastward oriented proximal-to-distal trend within a complex sequence stratigraphic framework including superimposed high-frequency cycles. 2. A range of source feeders that may be successively active along an irregular coastline, thereby forming lobes with opposite dispersal patterns. 3. An interplay of reactivation of Panafrican faults (Anti-Atlas/Ougarta) cannot be excluded and may have locally changed the place(s) of maximum accommodation space during deposition. It may also have induced the formation of shoals that would have been partially eroded and recycled. Thus, these apparently contradictory proximal-to-distal trends may actually depict a turning point in the re-organization of the basin predating the end-Ordovician glacial advance.

How to cite: Harlet, D., Douillet, G. A., Ghienne, J.-F., Dietrich, P., Bouscary, C., Razin, P., and Schlunegger, F.: Semi-3D stratigraphic architecture of a siliciclastic shallow-marine platform: Insights from the Ktawa Group (Late Ordovician) in Morocco, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8721, https://doi.org/10.5194/egusphere-egu22-8721, 2022.

EGU22-2950 | Presentations | SSP2.1

Preliminary report on δ13Ccarb isotope excursion through the Silurian of Kurtuvėnai - 161 borehole, Northwest Lithuania

Tomas Želvys, Andrej Spiridonov, Anna Cichon-Pupienis, Andrius Garbaras, and Sigitas Radzevicius

Lithuania is located in the eastern part of the Silurian Baltic Basin which was located near the equator during the Silurian. Kurtuvėnai -161 borehole is located in the Northwest Lithuania. The Silurian geological section of investigated interval is composed of siliciclastic and carbonate deposits and represents deep marine environments.

Samples for stable carbon isotope analysis were collected from 1441 – 1316 m depth interval. The sampling intervals range from 0.2 up to 1m. The stable carbon isotope values from carbonates were measured using Thermo Gasbench II coupled with a Thermo Delta V isotope ratio mass spectrometer.

In the investigated interval 10 graptolites biozones were distinguished: Lapworthi Biozone is distinguished in the lowest part of the section and linked to the Adavere Regional Stage (uppermost Telychian); the centrifugus - belophorus biozones mark the Jaani Regional Stage; perneri - lundgreni biozones correspond to the Jaagarahu; and parvus - nassa biozones marks the Gėluva Regional Stage of the Wenlock.

According to the δ13Ccarb isotope analysis results, a positive excursion was detected in the lower part of the studied interval from 1422.8 m up to 1390.8 m depth. There, the δ13Ccarb maximum value is 3.87 ‰. This positive δ13Ccarb anomaly can be linked to the Ireveken positive stable carbon isotopes excursion and the centrifugus – belophorus biozones interval of the lower Wenlock. We can also observe a positive δ13Ccarb excusion in the upper part of Homerian (from 1327 m depth) which potentially can be the lower part of the Mulde positive stable carbon isotopic event.

In summary, the δ13Ccarb values varied from -1.35 ‰ up to 3.92 ‰ in studied interval of Kurtuvėnai-161 borehole. A more detailed biostratigraphic and lithological study is needed for a better understanding of the integrated stratigraphy of the Silurian geological section in the Kurtuvėnai-161 borehole in the future.

How to cite: Želvys, T., Spiridonov, A., Cichon-Pupienis, A., Garbaras, A., and Radzevicius, S.: Preliminary report on δ13Ccarb isotope excursion through the Silurian of Kurtuvėnai - 161 borehole, Northwest Lithuania, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2950, https://doi.org/10.5194/egusphere-egu22-2950, 2022.

EGU22-9471 | Presentations | SSP2.1

Timing and pacing of the Hangenberg Crisis (Devonian-Carboniferous Boundary) in the Chanxhe sections, Belgium 

Anne-Christine Da Silva, Léonard Franck, Michiel Arts, and Julien Denayer

The Hangenberg Crisis, at the Devonian-Carboniferous Boundary, severely affected the marine realm. The crisis is characterised by several events associated with change in the sedimentation and biotic extinctions and turnovers. The Hangenberg Black Shale event that recorded the extinction peak in the pelagic realm corresponds to a widespread development of oceanic anoxia and/or dysoxia. The Hangenberg Sandstone event is associated with an extinction of neritic fauna in shallow-water settings, including the final demise of several classical Devonian faunas (stromatoporoids, quasiendothyrid foraminifers, placoderms, etc.). The succession of these events is nowadays explained by a combination of sea level fluctuations (third order transgressive sequence, out-of-sequence regression) and global climatic changes. Through the identification of Milankovitch cycles in the Chanxhe record, we aim at getting a better understanding of the timing and orbital forcing of the different events of the Hangenberg Crisis in shallow-water settings.

The sedimentary record of the interval of interest at Chanxhe is composed of 16 m of alternating decimetre-thick carbonate beds with shaly siltstones, which displays a clear cyclicity. The carbonate-siliciclastic alternations (~0.8 m) are bundled into larger cycles (~5 m) which are separated by intervals dominated by the shaly facies. This is followed by 11 m of carbonate dominated lithology with thin shale layers displaying a less clear cyclicity with ~3 m thick cycles. Then the equivalent of the Hangenberg dark shales is recorded as two dark shaly intervals separated by a carbonate bed. After the Hangenberg dark shales, the section displays carbonates, with the Devonian Carboniferous boundary in massive carbonates 7 m above the top of the black shales.

Samples have been collected along the record every 10 cm which were measured by the portable X-Ray Fluorescence device (Tracer 5, Bruker), allowing to provide elemental data throughout the record. Spectral analysis is applied on Ca and Al, to identify the main cyclicity in the record. The 0.8 meter-thick limestone/shale alternations is clearly recorded in the Ca and Al records and are associated with precession cycles (18 kyr), while the 5 m-cycles are associated with short eccentricity (100 kyr). Prior to the Hangenberg anoxic events, the 100-kyr cycles became less clear and shorter (~ 3 m) which is interpreted as a minimum eccentricity. During the Hangenberg, the cyclicity returns. However, after the Hangenberg and near the Devonian Carboniferous boundary, the facies become very homogeneous, consisting of massively bedded carbonates with no observable cyclicity,  which is also  other contemporaneous sedimentary successions (e.g. China, Poland).   

 

How to cite: Da Silva, A.-C., Franck, L., Arts, M., and Denayer, J.: Timing and pacing of the Hangenberg Crisis (Devonian-Carboniferous Boundary) in the Chanxhe sections, Belgium , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9471, https://doi.org/10.5194/egusphere-egu22-9471, 2022.

The Nordkapp Basin is located in the southwest Barents Sea. It was formed by rifting in the late Palaeozoic. As the area containing the basin moved north from the equator the climate changed from warm and arid to temperate and humid. Initially a large carbonate platform developed in the Barents Sea in the Carboniferous and Permian. The change in climate due to northward drift caused the platform to shift from a carbonate to clastic platform at the end of the Permian. The sea level changed several times during the Mesozoic due to a combination of eustatic changes and salt diapirism. The depositional environment in the area had been interpreted from multiple cores to vary from onshore coastal plain and delta plain to shelf environment due to the large scale sea level changes. In this work, the cores have been revisited to study smaller scale changes within the environments that had been recognised but not described extensively. The nature of small scale changes is different in different environments and can be seen in different aspects like the bioturbation intensity and clay and sand content. This work will compare the smaller scale sea level changes across the different environments encountered in the cores.

 

How to cite: Sandvold, M. and Felix, M.: Small scale changes superimposed on larger scale sea level-induced changes in cores from the Nordkapp Basin. , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2502, https://doi.org/10.5194/egusphere-egu22-2502, 2022.

The Permian time is characterized by various geodynamic and biotic events. The rifting of Gondwana and the formation of the super-continent Pangea are the most important events. The cessation of major Gondwana rifting and thermal cooling has subsequently resulted in the development of marine Tethyan settings at the margin of the northwestern Indian Plate. Based on detailed outcrop-based lithostratigraphical investigations, a total of three formations have been distinguished. The presence of diagnostic foraminifer’s species able to assign Wordian, Capitanian-Wuchiapingian, and Late Wuchiapingian to Changhsingian ages to these rock units respectively. The detailed biostratigraphic and sedimentological analyses of the upper Permian units of northern Pakistan divulged three phases of the carbonate platform development. Initially, the early Permian pure clastic Gondwana deposits were replaced by the Tethyan setting during the middle Permian (Wordian) time whereby the wave-dominated delta was established as the sea-level rises. However, such deltaic deposits were gradually evolved into a pure carbonate system during the Capitanian time in response to gradual transgression. The Capitanian and Wuchiapingian times show the development of a diverse shallow carbonate platform along the northwestern Indian Plate. The late Permian global regression has significantly disturbed the carbonate factory and subsequently developed river-dominated deltaic deposits of carbonate and clastic mixed system. Such a mixed system was again evolved in a carbonate platform during the Early Triassic.

How to cite: Wadood, B., Li, H., and Khan, S.: Evolution of the Permian carbonate platform on Gondwana shelf, Pakistan: sedimentological and biostratigraphic approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-227, https://doi.org/10.5194/egusphere-egu22-227, 2022.

EGU22-10150 | Presentations | SSP2.1

Phanerozoic scale modulation of brachiopod longitudinal expansion fitness forced by plate tectonics

Andrej Spiridonov, Lauras Balaukauskas, and Shaun Lovejoy

Brachiopods are a phylum of Animalia which are characterized by a rich fossil record. But this record shows drastic decrease in brachiopod diversity and environmental occupancy through time. One set of explanations says that the decline is related to the state shifts in dominance after mass extinction events (usually P-Tr). Another explanatory set suggests that the dominant cause of brachiopod decline is competition with other functionally similar clades. The competition hypothesis predicts that there should be a monotonic decrease in some fitness metric at organismal or species level. Often overlooked is the influence of long-term tectonic processes which control size, geometry and topology of environments on the changes in dominance of brachiopods. Here we tested this hypothesis by analyzing the dynamics of longitudinal and latitudinal ranges of brachiopod genera in the post-Cambrian Phanerozoic using the Paleobiology Database global paleogeographic occurrence data. The major pattern revealed in the study is that while latitudinal ranges were approximately constant through the eon, the longitudinal ranges experienced long-term trend-like decline. In the beginning of the Phanerozoic and also during the Cretaceous-Cenozoic, average ranges of brachiopod genera were much more elliptic in the west-east direction, while in the middle of the Phanerozoic they become almost circular in their shape. The latitudinal ranges reflect average temperature tolerance of a genus, while the longitudinal ranges reflect capacity of a genus to expand in similar climatic conditions, thus reflecting its potential of expansion fitness. The scale by scale analysis of range shapes and continental fragmentation index found consistent scale independent positive correlation of ellipticity (in W-E direction) with higher fragmentation of continents. Therefore the analyses revealed statistically significant patterns that support the hypothesis of a strong tectonic control on the shapes and sizes of average geographic ranges of brachiopod genera. Smallest ranges with lowest ellipticity occurred in Triassic-Jurassic. Therefore, the loss of genus level expansion fitness due to tectonic amalgamation of Pangaea should have been an important factor which contributed to the failure of brachiopods to fully recover after P-Tr extinction event.

This study was supported by the project S-MIP-21-9 “The role of spatial structuring in major transitions in macroevolution”.

How to cite: Spiridonov, A., Balaukauskas, L., and Lovejoy, S.: Phanerozoic scale modulation of brachiopod longitudinal expansion fitness forced by plate tectonics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10150, https://doi.org/10.5194/egusphere-egu22-10150, 2022.

EGU22-11752 | Presentations | SSP2.1

Size and abundance variations of Schizosphaerella across the Toarcian Oceanic Anoxic Event 

Giulia Faucher, Stefano Visentin, Gabriele Gambacorta, and Elisabetta Erba

The Toarcian oceanic anoxic event (T-OAE), dated as early Toarcian is considered one of the most extreme paleoenvironmental perturbations in Earth’s history. It is characterized by global warming, accelerated weathering, sea level rise, oceanic anoxia and acidification and extensive accumulation of organic matter. In Jurassic times, calcareous nannoplankton was already a most efficient rock-forming group and therefore pelagic sedimentary successions preserve invaluable data to track changes across the T-OAE. In this work, we focus on Schizosphaerella across the T-OAE recovered in the uppermost Pliensbachian–lower Toarcian Sogno Core that consists of a fully pelagic, continuous, well-dated record from a deep plateau (~1500 m water depth) in the Lombardy Basin (northern Italy). The objective of this investigation is the quantification of changes in size and abundance of the micrite-forming schizosphaerellids to derive their biocalcification tempo and mode in response to the T-OAE perturbations, to assess the implications of Schizosphaerella biocalcification changes, in terms of abundance and size, for the pelagic carbonate sedimentation. Absolute abundances and morphometric changes obtained for small Schizosphaerella punctulata” (valve width < 7 μm),  S. punctulata (valve width > 7 μm) and “encrusted S. punctulata” (all specimens characterized by a crust surrounding the valve) revealed large fluctuations in the investigated interval. We identify an abundance fall caused by the failure of S. punctulata and “encrusted S. punctulata” during the core of the T-OAE, that along with the increased abundance of small specimens produced the reduction of average dimensions. Thus, the average size decline is not the result of a general valve reduction, but rather derives from the increase in abundance of small specimens (< 7 μm). This is substantiated by absolute abundances of individual S. punctulata morphogroups that unambiguously demonstrate that such a pattern is not an artefact of relative abundances (closed sum problem).

We hypothesize that the concomitant drop in abundance and shrinkage of valve size is related to hyperthermal conditions associated with excess CO2 and ocean acidification.

Finally, the co-occurrence in the same samples of S. punctulata specimens (> 7 mm) with and without a crust, is indicative of species-specific diagenetic effects. Based on the S. punctulata ultrastructure we conclude that specimens without diagenetic crusts belongs to S. astrea while encrusted specimens are attributable to S. punctulata and we infer that the presence of the diagenetic crust could be taxonomically diagnostic to distinguish S. punctulata from S. astrea.

How to cite: Faucher, G., Visentin, S., Gambacorta, G., and Erba, E.: Size and abundance variations of Schizosphaerella across the Toarcian Oceanic Anoxic Event , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11752, https://doi.org/10.5194/egusphere-egu22-11752, 2022.

Lower and Middle Jurassic sedimentary deposits in southern Germany have accumulated in a shallow-marine shelf environment and are typically dominated by clayey lithologies with minor occurrences of sandstones and limestones. The sedimentary evolution and paleoclimatic significance of these poorly exposed deposits often remain largely unexplored. Here we present a suite of high-resolution x-ray fluorescence (XRF) core scanning data from southern Germany covering the Upper Toarcian and Aalenian stages. The overall objective of this study is to identify Transgressive-Regressive cycles based on the analysis of three cores obtained during scientific drilling campaigns in 2019-2021. Cores have been analyzed with an Avaatech XRF Core Scanner at a 10 mm sampling interval, an energy of 10 keV and a current of 500 µA to measure element intensities ranging from aluminium through iron. Resulting trends in elemental ratios indicative for subtle grain-size variations such as Si/Al are used to reconstruct shoreline trajectories and establish a sequence stratigraphic framework (see Thöle et al. 2020). Particularly the thick and largely homogenous Opalinuston Formation appears suitable in that respect, likely resulting from extraordinarily high sedimentation rates during the lower Aalenian in southern Germany, thus providing a complete but unexplored archive of paleoclimatic signals.

 

References:

Thöle, H., Bornemann, A., Heimhofer, U., Luppold, F. W., Blumenberg, M., Dohrmann, R., & Erbacher, J. (2020). Using high‐resolution XRF analyses as a sequence stratigraphic tool in a mudstone‐dominated succession (Early Cretaceous, Lower Saxony Basin, Northern Germany). The Depositional Record, 6(1), 236-258.

How to cite: Mann, T., Bornemann, A., and Erbacher, J.: A sequence-stratigraphic framework for the Toarcian – Aalenian from southern Germany based on x-ray fluorescence core scanning data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4877, https://doi.org/10.5194/egusphere-egu22-4877, 2022.

EGU22-8150 | Presentations | SSP2.1

Litho- and cyclostratigraphy of the Aalenian Opalinusclay Formation in the Swabian Alb deduced from downhole logging data

Katharina Leu, Christian Zeeden, Thomas Wonik, Thomas Mann, Jochen Erbacher, and André Bornemann

From 2019 to 2021, three cores were drilled at different locations in the southern German Swabian Alb as part of the SEPIA project (Sequence Stratigraphy of the Aalenian in Southern Germany). They comprise sediments of 200 to 250 m length and are penetrating Lower and Middle Jurassic strata from the Pliensbachian to Bathonian stages (~ 190-166 Ma). The aim of this project is the development of a sequence stratigraphic model of the South German Basin at the transition from the Lower to Middle Jurassic time. Conclusions should be drawn towards the source area of the sediments as well as on the influence of sea level fluctuations on sedimentation.

Today, the Swabian Alb is a SW-NE trending mountain chain consisting of mainly carbonate rocks, and is one of the most distinctive regions in Germany where Jurassic strata is cropping out. During the middle Jurassic, Europe was almost completely covered by a shallow epi-continental sea including several small emerging areas or islands, located at latitudes about 15° lower than today. Southern Germany experienced predominant deposition of fine clastic sediments in a tropical climate. The most common sediments of this period are dark clays and oolithic ironstones, whereas condensation and discontinuity surfaces occur in many instances. Accommodation space for these sediments was not only generated by changes in sea level, but also by continuing subsidence of the area, explaining the inhomogeneous thickness and changes in facies of the sediments.

The geophysical downhole logging data of the stratigraphic record is used to develop a lithological classification and correlation of the boreholes sediments by the application of a cluster analysis to the data. Furthermore, the downhole logging data is used to perform cyclostratigraphy in selected intervals. The focus of the intervals chosen for cyclostratigraphy lies on the Aalenian stage, as this stage holds the most continuous and extended record in all three boreholes. Predicted timespans of these intervals yield similar results of ~800-1100 ka for all three boreholes and might provide a new benchmark for progressive improvement, especially for cyclostratigraphic analyses of the Lower Aalenian Opalinusclay Formation.

How to cite: Leu, K., Zeeden, C., Wonik, T., Mann, T., Erbacher, J., and Bornemann, A.: Litho- and cyclostratigraphy of the Aalenian Opalinusclay Formation in the Swabian Alb deduced from downhole logging data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8150, https://doi.org/10.5194/egusphere-egu22-8150, 2022.