SSP1.1
Open session on stratigraphy, sedimentology and palaeontology

SSP1.1

EDI
Open session on stratigraphy, sedimentology and palaeontology
Convener: Stephen Lokier | Co-conveners: Madeleine Vickers, Alicia FantasiaECSECS, Guilhem Amin Douillet
Presentations
| Wed, 25 May, 13:20–18:30 (CEST)
 
Room -2.32/33

Presentations: Wed, 25 May | Room -2.32/33

Chairpersons: Stephen Lokier, Madeleine Vickers
13:20–13:22
Palaeontology
13:22–13:29
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EGU22-6816
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ECS
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On-site presentation
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.

13:29–13:36
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EGU22-3774
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Virtual presentation
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.

13:36–13:43
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EGU22-9898
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ECS
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On-site presentation
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Valentin Jamart and Julien Denayer

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.

13:43–13:50
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EGU22-9154
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ECS
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On-site presentation
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.

13:50–13:57
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EGU22-8957
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ECS
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Highlight
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Virtual presentation
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.

13:57–14:04
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EGU22-12752
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ECS
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Virtual presentation
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.

14:04–14:11
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EGU22-8602
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On-site presentation
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.

14:11–14:18
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EGU22-1086
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ECS
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On-site presentation
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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.

14:18–14:25
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EGU22-9230
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Virtual presentation
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.

14:25–14:32
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EGU22-9591
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ECS
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Virtual presentation
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.

14:32–14:39
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EGU22-2039
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Virtual presentation
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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.

14:39–14:50
Coffee break
Chairpersons: Stephen Lokier, Alicia Fantasia
Stratigraphy
15:10–15:17
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EGU22-117
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ECS
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Virtual presentation
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.

15:17–15:24
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EGU22-3751
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Virtual presentation
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.

15:24–15:31
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EGU22-535
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ECS
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Virtual presentation
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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.

15:31–15:38
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EGU22-2958
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On-site presentation
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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.

15:38–15:45
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EGU22-9404
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ECS
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Virtual presentation
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.

15:45–15:52
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EGU22-6008
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Virtual presentation
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.

15:52–15:59
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EGU22-3697
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Virtual presentation
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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.

15:59–16:06
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EGU22-2422
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ECS
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Virtual presentation
A flashback to changes across the Cretaceous-Paleogene boundary (K/Pg) in Turkey:  a faunal and environmental portray
(withdrawn)
A. Uygar Karabeyoglu, Jorge Spangenberg, and Thierry Adatte
16:06–16:13
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EGU22-8704
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ECS
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Virtual presentation
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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.

16:13–16:21
Sedimentology
16:21–16:28
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EGU22-3993
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Virtual presentation
Yufeng Chen, Bing Deng, Weiguo Zhang, and Shu Gao

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.

16:28–16:35
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EGU22-9355
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ECS
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On-site presentation
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.

Coffee break
Chairpersons: Stephen Lokier, Guilhem Amin Douillet
17:00–17:07
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EGU22-6404
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ECS
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Virtual presentation
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.

17:07–17:14
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EGU22-1519
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ECS
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Presentation form not yet defined
Chawisa Phujareanchaiwon, Piyaphong Chenrai, and Kasira Laitrakull

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.

17:14–17:21
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EGU22-4605
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ECS
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On-site presentation
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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.

17:21–17:28
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EGU22-9638
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Virtual presentation
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.

17:28–17:35
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EGU22-4941
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Virtual presentation
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sheng liu

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.

17:35–17:42
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EGU22-3705
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ECS
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Virtual presentation
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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.

17:42–17:49
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EGU22-1780
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ECS
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Virtual presentation
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fulin meng

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.

17:49–17:56
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EGU22-6299
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ECS
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Virtual presentation
Tara Edwards and Robyn Pickering

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.

17:56–18:03
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EGU22-6973
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ECS
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Virtual presentation
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.

18:03–18:11
18:11–18:30