SSP1.3 | Mass extinctions and environmental changes throughout the geological time: Causes and consequences
EDI

Mass extinctions and severe environmental changes in the Phanerozoic are temporarily associated with large volcanic eruptions and meteorite impacts, suggesting causal relationships. This session invites contributions presenting new data and results from the end-Ordovician, Late and end-Devonian, end-Permian, end-Triassic, end-Cretaceous, and other paleoenvironmental crises, such as the Paleocene-Eocene Thermal Maximum and Oceanic Anoxic Events in the Mesozoic. The goal of the session is to bring together researchers from geological, geophysical, and biological disciplines to improve our knowledge of the cause-effect scenario of these major environmental changes.

Co-organized by GMPV8
Convener: Alicia FantasiaECSECS | Co-conveners: Thierry Adatte, Sverre Planke, David Bond, Eric Font
Orals
| Fri, 28 Apr, 08:30–12:25 (CEST)
 
Room -2.31
Posters on site
| Attendance Thu, 27 Apr, 10:45–12:30 (CEST)
 
Hall X3
Posters virtual
| Attendance Thu, 27 Apr, 10:45–12:30 (CEST)
 
vHall SSP/GM
Orals |
Fri, 08:30
Thu, 10:45
Thu, 10:45

Orals: Fri, 28 Apr | Room -2.31

Chairpersons: Alicia Fantasia, Thierry Adatte, Eric Font
08:30–08:35
08:35–08:45
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EGU23-5978
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SSP1.3
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On-site presentation
Phillip Jardine, Huiping Peng, John Marshall, Barry Lomax, Benjamin Bomfleur, Matthew Kent, Wesley Fraser, and Feng Lui

The end-Permian mass extinction (EPME) is the largest extinction event of the Phanerozoic, but the specific causal pathways, especially in the terrestrial realm, are unresolved. Malformed pollen and spores recovered from the EPME interval have been taken as indicators of extreme environmental stress in terrestrial ecosystems. However, whether they relate to volcanism-driven ozone-layer deterioration and enhanced ultraviolet-B (UV-B) flux, or volcanogenic toxic pollutants including mercury and acid rain, or some combination of the two, remains unclear. Here, we take advantage of a novel palynological proxy, which utilises the ability of land plants to adjust the concentration of protective UV-B-absorbing compounds (UACs) in the outer wall of their reproductive propagules in response to changes in ambient UV-B flux. We analysed UAC abundances in ca. 800 pollen grains from an independently-dated Permian-Triassic boundary section in southern Tibet, in order to infer changes in UV-B-radiation flux at the Earth’s surface during the EPME. Our data reveal an excursion in UACs that coincides with a spike in mercury concentration and a negative carbon-isotope excursion in the latest Permian deposits, suggesting a close temporal link between large-scale volcanic eruptions, global carbon- and mercury-cycle perturbations, and ozone-layer disruption. Because enhanced UV-B radiation can exacerbate the environmental deterioration induced by massive magmatism, ozone depletion is considered a compelling ecological driver for the terrestrial mass extinction.

How to cite: Jardine, P., Peng, H., Marshall, J., Lomax, B., Bomfleur, B., Kent, M., Fraser, W., and Lui, F.: Direct evidence for elevated UV-B radiation and ozone layer disruption during the end-Permian mass extinction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5978, https://doi.org/10.5194/egusphere-egu23-5978, 2023.

08:45–08:55
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EGU23-9228
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SSP1.3
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ECS
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On-site presentation
André Navin Paul, Jahandar Ramezani, and Urs Schaltegger

A large volume of intrusive sills of the Siberian Traps Large Igneous Province (STLIP) is found in the Tunguska Basin, Siberia. These rocks intrude evaporite, carbonate and siliciclastic lithologies, which are sometimes rich in organic material and bear massive coal layers. The interaction of hot basaltic magma with the cold country rocks is considered to have released large volumes of thermogenic volatiles that altered atmosphere composition and had a serious impact on climate and biodiversity (e.g., Svensen et al. 2019). Previous high precision isotope dilution thermal ionisation mass spectrometry (ID–TIMS) U-Pb dates obtained on zircon, baddeleyite and perovskite suggest that the intrusive activity lasted from ca. 251.9 Ma until 251.0 Ma (Burgess et al., 2017). However, the total duration of the intrusive magmatic history, as well as its spatial extent, are not well explored in terms of high precision geochronology, since zircon from a mere 17 sills have been dated at highest precision by ID-TIMS so far.

To enhance the temporal control on the STLIP intrusive history, we extracted accessory minerals from sill samples of 5 borehole sites that have been characterised geochemically (low-Ti basalt, Callegaro et al., 2021), to perform U-Pb ID-TIMS dating. These boreholes are situated between Bratsk and Tura, in an area for which no ID-TIMS geochronology is available so far. These boreholes will help to fill the gap on the western part of the STLIP dataset presented by Burgess et al. (2017). For three boreholes, we were able to extract baddeleyite and/or zircon from three/four stratigraphic levels. First U-Pb data of baddeleyite indicate predominantly young U-Pb dates, in the range of 251.5 Ma down to 250.0 Ma, with a tendency to minor discordance and a range in dates that exceeds expectation for a single growth population. Curiously, the geochemical characteristics of samples analysed from the same boreholes (Callegaro et al., 2021) are interpreted as potentially earliest stage of the STLIP, a mismatch with our preliminary U-Pb dating results. Given the doubts about the robustness of baddeleyite against Pb-loss during secondary processes, we hope to directly compare baddeleyite and zircon U-Pb dates in selected samples. Should the accuracy of baddeleyite U-Pb dates be confirmed through similarly young zircon U-Pb, this would mean that STLIP intrusive activity and related volatile injection (including Hg) into the atmosphere significantly post-dated the Permo-Triassic Boundary and extended into the Lower Triassic (Griesbachian-Dienerian). This fact would question the assumption that Hg spikes in the sedimentary record of South China are necessarily synchronous and can be used as time markers for the biological crisis at around the PTB.

References:

Burgess, S.D., et al. Initial pulse of Siberian Traps sills as the trigger of the end-Permian mass extinction. Nat Commun 8, 164 (2017). https://doi.org/10.1038/s41467-017-00083-9

Callegaro, S., et al. Geochemistry of deep Tunguska Basin sills, Siberian Traps: correlations and potential implications for the end-Permian environmental crisis. Contrib Mineral Petrol 176, 49 (2021). https://doi.org/10.1007/s00410-021-01807-3

Svensen H.H., et al. Sills and gas generation in the Siberian Traps. Phil. Trans. R. Soc. A. 376 (2018). http://doi.org/10.1098/rsta.2017.0080

How to cite: Paul, A. N., Ramezani, J., and Schaltegger, U.: Extending the geochronological record of intrusive rocks of the Siberian Traps Large Igneous Province, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9228, https://doi.org/10.5194/egusphere-egu23-9228, 2023.

08:55–09:05
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EGU23-9038
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SSP1.3
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Highlight
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On-site presentation
Michael Joachimski, Johann Müller, Timothy Gallagher, Gregor Matthes, Daoliang Chu, Fedor Mouraviev, Vladimir Silantiev, Yadong Sun, and Jinnan Tong

The end-Permian mass extinction, the largest biological crisis in Earth history, is currently understood in the context of Siberian Traps volcanism introducing large quantities of greenhouse gases to the atmosphere. We reconstructed the late Permian to Middle Triassic atmospheric CO2 record by applying the carbonate paleosol pCO2 barometer to soil carbonates from sections in northwest China (Xinjiang Province), north China (Henan and Shanxi Provinces), Russia (South Ural foreland basin), South Africa (Karoo Basin), and the United Kingdom (Dorset). Atmospheric pCO2 shows an approximate 4-fold increase from mean concentrations of 412–919 ppmv in the late Permian (Changhsingian) to maximum levels between 2181 and 2610 ppmv in the Early Triassic (late Griesbachian). Mean CO2 estimates for the later Early Triassic are between 1261–1936 ppmv (Dienerian) and 1063–1757 ppmv (Spathian). Significantly lower concentrations ranging from 343 to 634 ppmv are reconstructed for the latest Early to Middle Triassic (Anisian). In parallel to the reconstructed rise in greenhouse gas levels, low-latitude sea surface temperatures (SST) increased by 7–10 °C, from 25–28 °C to >35 °C (Joachimski et al., 2020). With the decrease in pCO2 in the late Spathian to Anisian, SSTs decreased as well (Sun et al., 2012). Thus, pCO2 as well as SSTs persisted at high levels for almost 5 m.y.

In contrast, pCO2 reconstructed using the photosynthetic carbon isotope fractionation suggest much lower atmospheric pCO2 (e.g. Shen et a. 2022), inconsistent with significant warming, while modeling studies suggest up to a 13-fold increase in pCO2 (e.g. Cui et al. 2021). Most important, the 5 m.y. long episode of elevated pCO2 suggests that negative feedback mechanisms such as silicate weathering, the most effective mechanism by which to extract CO2 from the atmosphere and to buffer Earth’s climate, were not effective enough to reduce atmospheric pCO2 to pre-crisis levels. Instead, marine authigenic clay formation (i.e., reverse weathering) may have been an important component of the global carbon cycle keeping atmospheric pCO2 at elevated levels during this critical time interval.

References: Cui et al. 2021, PNAS, V. 118, No.37, e201470118; Joachimski et al. 2020, GSA Bull., 132, 427-443; Shen et al. 2022, Nat. Geosc., 15, 839-844; Sun et al. 2012, Science, 338, 366-370.

How to cite: Joachimski, M., Müller, J., Gallagher, T., Matthes, G., Chu, D., Mouraviev, F., Silantiev, V., Sun, Y., and Tong, J.: Atmospheric CO2 history of the late Permian and Early Triassic, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9038, https://doi.org/10.5194/egusphere-egu23-9038, 2023.

09:05–09:15
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EGU23-5285
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SSP1.3
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On-site presentation
Sara Callegaro, Henrik H. Svensen, Thea H. Heimdal, Frances M. Deegan, Dougal A. Jerram, Alexander G. Polozov, and Sverre Planke

The Tunguska Basin in East Siberia (Russia) hosts an extensive network of thick sills, part of the Siberian Traps Large Igneous Province. High-precision geochronology links the initial phase of sill emplacement to the end-Permian cascade of environmental catastrophes that almost expunged life on Earth (Dal Corso et al., 2022). The end-Permian atmosphere was impacted by a voluminous cocktail of gases, from CO2 and SO2 to halocarbons. Multiple lines of evidence suggest that sills emplaced within the evaporitic and coal-rich series of the Tunguska Basin acted as major contributors to this outgassing. Basin-scale observations and thermal modelling provide evidence of thermogenic gas production and release (Svensen et al., 2018). For the Tunguska sills, whole-rock geochemistry (Callegaro et al., 2021) and micro-analyses track multiple processes of magma host-rock interaction occurring at different levels across the plumbing system and the volcanic basin. Whole-rock trace elements and radiogenic isotopes reveal assimilation of variable crustal lithologies, from the crystalline basement to evaporites and carbonates in the Tunguska Basin. Assimilation of anhydrite-dominated evaporites is confirmed by whole-rocks sulfur isotopes. Assimilation of halogen-dominated evaporites is tracked by detailed mineral analyses of dolerite sills. We found widespread evolved late-stage pockets among the larger plagioclase and clinopyroxene crystals in the Tunguska dolerites. These pockets filled with an evolved, volatile-rich minerals, dominated by biotite and quartz, with minor K-feldspar, chloro-apatite, Cl-rich amphibole, sulfides and occasional baddeleyite and zircon. Biotite in the pockets is extremely enriched in Cl, especially at the rims. Plagioclase surrounding the pockets shows highly albitic rims. These compositions are widespread across the Tunguska Basin, where sills intruded halite- and anhydrite-rich evaporites, and suggest extensive mobilization of crustal halogens and sulfur associated with the emplacement of the sills, along with previously demonstrated thermogenic carbon production. Notably, most investigated sills are geochemically correlated with the phase of Siberian Traps magmatism coeval with the main extinction horizon (Callegaro et al., 2021).

 

Callegaro S., Svensen H.H., Neumann E.R., Polozov A.G., Jerram D.A., Deegan F.M. Planke S., Shiganova O.V., Ivanova N.A. & Melnikov N.V., 2021. Geochemistry of deep Tunguska Basin sills, Siberian Traps: correlations and potential implications for the end-Permian environmental crisis. Contrib. Mineral. Petrol., 176, 49.

Dal Corso J., Song H., Callegaro S., Chu D., Sun Y., Hilton J., Grasby S.E., Joachimski M.M. & Wignall P.B. 2022. Environmental crises at the Permian–Triassic mass extinction. Nat. Rev. Earth Environ., 3(3), 197–214.

Svensen H.H., Frolov S., Akhmanov G.G., Polozov A.G., Jerram D.A., Shiganova O.V., Melnikov N.V., Iyer K. & Planke S. 2018. Sills and gas generation in the Siberian Traps. Phil. Trans. R. Soc. A., 376:20170080.

How to cite: Callegaro, S., H. Svensen, H., H. Heimdal, T., Deegan, F. M., Jerram, D. A., Polozov, A. G., and Planke, S.: Magma-evaporite interaction in doleritic sills from the Siberian Traps: insights from whole-rock and mineral data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5285, https://doi.org/10.5194/egusphere-egu23-5285, 2023.

09:15–09:25
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EGU23-14142
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SSP1.3
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Highlight
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On-site presentation
Henrik H. Svensen, Timm John, Alexander G. Polozov, Sara Callegaro, Morgan T. Jones, Robert J. Newton, Kirsten E. Fristad, and Sverre Planke

In the Siberian Traps Large igneous province (LIP), the emplacement of magma in sedimentary strata led to explosive release of volatiles and the formation of large pipe structures with explosion craters. Of the hundreds of pipes present, several still have preserved crater lake sediments, representing the only known end-Permian sedimentary archive proximal to the Siberian Traps. Here we present new data from a core from the best studied crater lake section, the October pipe/crater located west of Bratsk in East Siberia. The S26 core contains 505 meters of sediments and in order to investigate the geochemical processes in the lake and the possible role of brine influx from the breccia pipe below, we have analysed carbon isotopes, the mercury content, δ34S and δ56Fe in pyrite and δ56Fe in magnetite, from the breccia pipe and crater sediments. In addition, reference samples from two other breccia pipes and relevant sedimentary strata from the Tunguska Basin were analysed for comparison. Our previous work has shown that the lake was saline, stratified and anoxic/euxinic, with up to 4 wt.% TOC, and abundant framboidal pyrite. The sediments are dominated by sandstone and siltstone, sourced from the material ejected during the pipe formation, and have not experienced heating above ca. 50 °C. The basal deposits are coarse and contain reworked magnetite-apatite ore that originally precipitated from hydrothermal fluids within the upper parts of the pipe. The sediments are calcite-cemented and the volcanic minerals altered to clays and zeolites, with occasional oxidized zones showing that the water level fluctuated, in accordance with rapid subsidence resulting from dissolution of deeper-seated Cambrian evaporites. New results show a marked shift in the isotope systems from the breccia pipe and into the basal lake deposits. The δ34S shifts from background sedimentary values (+20-30‰) in the pipe breccia, to -7-0‰ in the lower half of the lake sediments followed by an increase to +20 ‰ towards the top of the lake. The trend is evident in the δ56Fe in magnetite as well, with a 0.4 ‰ negative shift from the breccia and into the lake sediments, followed by an upward increase in the stratigraphy. We suggest that basinal brines rich in iron and sulphate were partly reduced in the stratified lake, leading to pyrite precipitation and isotope fractionation. The data shows the interplay between lake processes and fluid seepage from a hydrothermal system, making these deposits unique for understanding the consequences of LIP formation.  

How to cite: Svensen, H. H., John, T., Polozov, A. G., Callegaro, S., Jones, M. T., Newton, R. J., Fristad, K. E., and Planke, S.: Carbon, sulphur, and mercury geochemistry in a crater lake in the Siberian Traps, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14142, https://doi.org/10.5194/egusphere-egu23-14142, 2023.

09:25–09:35
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EGU23-11420
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SSP1.3
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ECS
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Virtual presentation
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Oluwaseun Edward, André N. Paul, Hugo Bucher, Thierry Adatte, Urs Schaltegger, and Torsten Vennemann

Mercury concentration anomalies in sedimentary successions are widely considered as proxies for volcanism and together with negative carbon isotope (δ13C) excursions, are a common feature of many Permian-Triassic boundary (PTB) sections 1,2. On the basis of a temporal overlap of these geochemical excursions with the Permian-Triassic mass extinction (PTME) interval and PTB at the stratigraphically condensed Meishan PTB Global Stratotype Section and Point (GSSP), Hg and/or C- isotope excursions occurring stratigraphically close to the PTB are often used as chemostratigraphic markers for the extinction interval 2. However, several studies indicate that near-PTB Hg anomalies vary in their stratigraphic occurrence and expression 3; a point also noted for PTB δ13C records 4. Permian – Triassic sedimentary successions are also frequently characterized by an unconformity straddling the PTB and/or by stratigraphic condensation, questioning the robustness of PTME correlations based on these geochemical markers. This study investigates the terminal Permian to earliest Triassic Hg and δ13C record, coupled with U-Pb zircon geochronology, for two stratigraphically continuous deep-water marine sections in the Nanpanjiang Basin, South China. The results show an interval of significant Hg enrichment stratigraphically close to the PTB, which is coeval with the nadir of a negative δ13C excursion spanning the Changhsingian to Induan. U-Pb zircon geochronology of volcanic ash beds interbedded with sediments in the studied sections indicate that the onset of this Hg anomaly postdates 251.82 ± 0.060 Ma, and that the peak of the Hg anomaly (and nadir of the negative δ13C excursion) is of Griesbachian age (between 251.59 ± 0.052 Ma and 251.67 ± 0.079 Ma). The peak of the Hg anomaly and nadir of the δ13C excursion in these stratigraphically continuous marine successions post-date both the PTB (251.90 ± 0.024 Ma) and mass extinction interval (251.94 ± 0.037 Ma – 251.88 ± 0.031 Ma) as determined from the Meishan GSSP 5. Our results indicate that stratigraphical correlation of the extinction interval based on Hg anomalies and/or δ13C excursions occurring stratigraphically close to the litho- or bio-stratigraphically determined PTB should be interpreted with caution. Furthermore, this study emphasizes the importance of precise and accurate U-Pb zircon ages for stratigraphic correlation between spatially disparate localities, especially during periods of notable environmental perturbations and biotic turnover such as the Permian-Triassic transition.

References

1             Korte, C. & Kozur, H. W. Carbon-isotope stratigraphy across the Permian-Triassic boundary: A review. J Asian Earth Sci 39, 215-235 (2010). https://doi.org:10.1016/j.jseaes.2010.01.005

2             Shen, J. et al. Evidence for a prolonged Permian-Triassic extinction interval from global marine mercury records. Nat Commun 10, 1563 (2019). https://doi.org:10.1038/s41467-019-09620-0

3             Sial, A. N. et al. Globally enhanced Hg deposition and Hg isotopes in sections straddling the Permian-Triassic boundary: Link to volcanism. Palaeogeogr Palaeocl 540, 109537 (2020). https://doi.org:10.1016/j.palaeo.2019.109537

4             Shen, S.-Z. et al. A sudden end-Permian mass extinction in South China. GSA Bulletin 131, 205-223 (2019). https://doi.org:10.1130/B31909.1

5             Burgess, S. D., Bowring, S. & Shen, S. Z. High-precision timeline for Earth's most severe extinction. Proc Natl Acad Sci U S A 111, 3316-3321 (2014). https://doi.org:10.1073/pnas.1317692111

How to cite: Edward, O., Paul, A. N., Bucher, H., Adatte, T., Schaltegger, U., and Vennemann, T.: Mercury (Hg) anomalies and carbon isotope excursions as a stratigraphic marker for the Permian – Triassic mass extinction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11420, https://doi.org/10.5194/egusphere-egu23-11420, 2023.

09:35–09:45
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EGU23-13316
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SSP1.3
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ECS
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On-site presentation
Johann Müller, Yadong Sun, Fen Yang, Marcel Regelous, Alicia Fantasia, and Michael Joachimski

The end-Permian mass extinction occurred during an interval of extreme global warming caused by enormous greenhouse gas emissions from Siberian Traps volcanism. A common concomitant effect of global warming is ocean deoxygenation which can be observed in geological and modern times. In the case of the end-Permian mass extinction, marine anoxia has long been postulated as one of the key killing mechanisms. However, causes for the Permian-Triassic (P-T) deoxygenation are under debate. Two frequently invoked scenarios are eutrophication and ocean stagnation.

We present geochemical data from two P-T carbonate sections across the Paleotethys Ocean. Productivity-related proxies (reactive P, TOC and trace elements) indicate high organic matter and P export to the sediments during the late Permian. A decrease in all these proxies during the C. yini conodont Zone suggests a decline of marine primary productivity at the study sites, approximately 30 kyr prior to the main marine extinction interval. Moreover, C/P ratios document a switch from intense P-recycling to efficient P-burial. Above the C. yini conodont Zone, Ce-anomalies (measured on the carbonate fraction of our samples) shift from negative to positive revealing deoxygenation of the local water columns.

Our proxy data imply that low productivity coincided with anoxic conditions at the study sites, hence not supporting a eutrophication scenario as a cause for the intensification of anoxia. Instead, we argue that ocean stagnation caused a stably stratified water column with reduced mixing, upwelling, overturning and ventilation. Regenerated P was trapped in the deeper, aphotic zones of the stagnant Paleotethys Ocean and was not available for photosynthesis.

We suggest that those settings of the Paleotethys Ocean represented by our study sections (deep slope and distal carbonate ramp) were characterized by high productivity and well-ventilated conditions during the relatively cool late Permian. Prior to the marine extinction interval, conditions switched to a low-productivity-anoxic state which persisted into the Early Triassic. This productivity collapse likely resulted in food shortage for higher trophic levels further stressing heterotrophic organisms before and during the extinction event.

How to cite: Müller, J., Sun, Y., Yang, F., Regelous, M., Fantasia, A., and Joachimski, M.: Marine primary productivity and redox conditions during the Permian-Triassic transition, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13316, https://doi.org/10.5194/egusphere-egu23-13316, 2023.

09:45–09:55
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EGU23-14371
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SSP1.3
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ECS
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Virtual presentation
Fen Yang, Yadong Sun, Patrick Frings, Lin Luo, Jingwen Eh, Lina Wang, Yafei Huang, Tan Wang, Johann Müller, and Shucheng Xie

The Permian witnessed the extensive development of cherts from the palaeoequator to the northern high latitudes. However, large-scale chert deposition was abruptly terminated in the latest Permian, resulting in the Early Triassic "chert gap". Deepwater sedimentary successions in South China across the Permian-Triassic transition recorded the shift from radiolarian- and spicule-bearing siliceous units to carbonate/siliciclastic facies in the equatorial Tethys. In order to constrain the onset time of the chert production crisis and understand its nature, we carried out sedimentological, palaeontological, and geochemical analyses on two deepwater sections along the northern margin of the South China Block. Our results suggest that chert production in equatorial latitudes was already weakened in the Clarkina changxingensis conodont zone. The final collapse of the chert factory occurred in the Clarkina yini - Hindeodus praeparvus/Clarkina zhangi Zone and was accompanied by a significant decrease in SiO2 content, which predated the negative carbonate carbon isotope excursion and climate warming but coincided with a sharp decline in primary productivity. Combined with Si box model results, our study suggests that global warming cannot maintain a multi-million-year chert gap. Instead, the loss of siliceous skeleton producers was the primary cause of the Early Triassic chert demise.

How to cite: Yang, F., Sun, Y., Frings, P., Luo, L., Eh, J., Wang, L., Huang, Y., Wang, T., Müller, J., and Xie, S.: Collapse of Late Permian chert factories in the equatorial Tethys and the nature of the Early Triassic chert gap, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14371, https://doi.org/10.5194/egusphere-egu23-14371, 2023.

09:55–10:05
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EGU23-12194
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SSP1.3
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Highlight
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On-site presentation
Sofie Lindström, Jennifer M Galloway, Christian Tegner, Remco Bos, and Bas van der Schootbrugge

Large-scale volcanic activity during the formation of large igneous provinces (LIPs) were contemporaneous with almost every mass extinction event in Earth’s history, and LIP activity is believed to have caused or contributed to at least three, if not all, Big Five mass extinctions. However, compared to the marine fossil record, the effects of the volcanism on the terrestrial plant record is still poorly understood. Extinctions in the animal record during major biotic crises in Earth history are not mirrored by comparable major changes in land plants. Despite being sedentary organisms land plants have evolved adaptations to cope with adverse changes in the environment which may provide autecological advantages compared to animals. Despite their remarkable resilience, land plant communities were still affected in multiple ways during LIP-induced extinction events. During the end-Triassic mass extinction (201.56–201.36 million years ago) emissions of greenhouse gases, sulfur dioxide and aerosols, halocarbons, polycyclic aromatic hydrocarbons, Hg and heavy metals from magmatic activity, as well as sea-level changes, during the emplacement of the Central Atlantic Magmatic Province (CAMP) are considered to have severely stressed land plants. This is exemplified by major changes in ecosystem structure in palynological records, a rise in microscopic charcoal abundance indicating increased wildfire activity, enhanced reworking of palynomorphs indicating increased soil erosion, acid rain damages on macroplant leaves, and increased abundances of abnormal spores and pollen indicating mutagenesis from Hg-toxicity and/or ozone layer depletion. Several of these land plant responses have also been observed during other extinction events contemporaneous to LIP activity. Here, we compare and discuss some of the changes in common between different biotic crises to evaluate whether there is a common pattern or not.

How to cite: Lindström, S., Galloway, J. M., Tegner, C., Bos, R., and van der Schootbrugge, B.: Land plant responses during extinction events linked to large volcanic eruptions – is there a common pattern?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12194, https://doi.org/10.5194/egusphere-egu23-12194, 2023.

10:05–10:15
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EGU23-12914
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SSP1.3
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ECS
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On-site presentation
Remco Bos, Wang Zheng, Sofie Lindström, Hamed Sanei, Irene Waajen, Isabel Fendley, Tamsin Mather, Appy Sluijs, and Bas van de Schootbrugge

The Central Atlantic Magmatic Province (CAMP) eruptions are generally regarded as the main driver of major environmental change and mass-extinction across the Triassic-Jurassic (T-J) boundary (~201.3 Ma). CAMP emissions have been invoked as the main trigger for the formation of abnormal pollen and spores during the end-Triassic crisis that may have led to forest dieback and proliferation of pioneer species. Proposed scenarios include extensive climate change leading to wildfire activity, acid rain, and increased UV-B radiation due to ozone depletion. More recently, volcanogenic mercury (Hg) has been implicated in the occurrence of mutations in fern spores. However, Hg-dynamics in deep-time remain poorly understood and require further examination. Here, we explore a new long-term (Rhaetian to Sinemurian) bulk Hg-concentration record combined with Hg-isotope data to understand the link between floral turnovers and the Hg-cycle.

Shallow marine sediments sampled from the Schandelah-1 core in northern Germany contain a record of cyclical shifts in malformed fern spores coinciding with fluctuations in carbon isotopes, increased levels of weathering, and Hg-enrichments. Similarly, increased mutagenic spore abundances with accompanying Hg-isotope records confirm the volcanogenic origin of Hg at the T-J boundary, showing a sharp positive excursion in mass-independent fractionation (MIF) of odd-numbered Hg-isotopes. Hettangian cyclicity is clearly reflected in the Hg-isotopic signals, showing positive excursions in mass-dependent/independent fractionation records (d202Hg and D199Hg) during periods of sedimentary Hg-enrichment. In addition, the Hettangian Hg-isotopic signature clearly deviates from Rhaetian signatures, which hints at climate-controlled mechanisms being responsible. Atmospheric Hg-loading via volcanism can explain the synchronous enrichments of Hg concentrations at the T-J boundary interval in multiple sites across the globe. In contrast, the origin of this periodic Hg-loading is more difficult to pinpoint, but it becomes clear that Hg is showing shifts in speciation and closely tied to terrestrial vegetation development. Orbitally induced changes to the regional hydrological regime, resulting in increased wildfire activity, monsoonal intensity, and soil erosion, potentially redistributed Hg stored in soil and/or bedrock reservoirs causing a shift to more mobile Hg-species. Overall, this shows a more dominant role of climate-induced Hg-remobilisation, rather than direct volcanic emissions, to disturbance in terrestrial vegetation.

How to cite: Bos, R., Zheng, W., Lindström, S., Sanei, H., Waajen, I., Fendley, I., Mather, T., Sluijs, A., and van de Schootbrugge, B.: Climate-driven Hg-remobilisation triggering long-term disturbance in vegetation following the end-Triassic mass-extinction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12914, https://doi.org/10.5194/egusphere-egu23-12914, 2023.

Coffee break
Chairpersons: David Bond, Sverre Planke, Alicia Fantasia
10:45–10:55
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EGU23-6742
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SSP1.3
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ECS
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On-site presentation
Natascha Kuhlmann, Bas van de Schootbrugge, Jean Thein, Sven-Oliver Franz, and Robert Colbach

The Triassic-Jurassic transition, from the Norian to the Hettangian (corresponding to the Rhaetian), was a critical timespan marked by a series of global environmental perturbations, most notably the end-Triassic mass extinction event (201.6 Ma). Here, we present palynological, mineralogical, geochemical, and sedimentological data obtained from new core material spanning the Upper Triassic to Lower Jurassic in the northeastern Paris Basin. Together, these data give new insights into the link between terrestrial and marine extinctions, and their respective driving mechanism. The Boust core (Lorraine, France) provides a complete succession of marginal marine sedimentation. The δ13Corg record from Boust reveals two major C-isotope excursions that, based on the available biostratigraphy, correspond to the Negative-1 (Marshi) and Negative-2 (Spelae) negative isotope excursions. While the Marshi excursion is marked by high abundances of dinoflagellate cysts, the Spelae excursion is marked by an influx of acritarch species. The two excursions bracket an interval of strongly diminished tree pollen abundances and proliferation of fern spore taxa, marking the extinction interval associated with the ETME and forming an equivalent to the Triletes Beds in Germany. This subdivision is confirmed by sedimentological and geochemical results as well as by lithological changes, which are reflecting the development of the depositional environment during the Rhaetian.

How to cite: Kuhlmann, N., van de Schootbrugge, B., Thein, J., Franz, S.-O., and Colbach, R.: Geochemical and palynological evidence for a two-phased end-Triassic mass extinction in the Paris Basin (Lorraine, France), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6742, https://doi.org/10.5194/egusphere-egu23-6742, 2023.

10:55–11:15
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EGU23-17314
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SSP1.3
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solicited
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Highlight
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On-site presentation
Aisha Al Suwaidi, Calum P. Fox, Wahyuningrum A. Lestari, Indodeep Ghosal, and Manuel Rigo

Tasmania was located at 62-74° S in the Triassic, a position today occupied by the frozen rocky Antarctic continent. Sedimentary archives of the Triassic from Tasmania present a unique opportunity to examine a high latitude archive of a world that was in a significant state of climatic and environmental flux from the end-Permian mass extinction (~252 Ma) to the Late Triassic, Norian Manicouagen bollide impact, ~214 Ma . Here we present new sedimentological and geochemical data spanning these major events from two core records (~300m each) located in Bicheno, Eastern Tasmania. These cores represent deposition of organic rich sediments in a coastal environment, that spans the Permo–Triassic boundary through the Norian. This data includes new carbon isotopes, charcoalfied wood abundances, sedimentological evaluation and pXRF data. The Permo-Triassic Event (PTE) is marked by a -6‰ excursion in δ13CTOC  with a change from Upper Parmeener Marine sequence limestones to more organic rich Upper Parmeener Freshwater sequences which includes mudstones, volcanic sandstones and tuffs. The Earliest Triassic is relatively condensed suggesting a relatively cold interval, with low sedimentation following on from the PTE. Other notable events include the Carnian Pluvial Event (CPE), with a marked increase in the abundance of charcoalified fossil wood, a -4‰ δ13CTOC excursion and increased weathering suggesting significant changes to the hydrological cycle and the climate during this interval. There is also evidence of the Middle Norian Event with a -4‰ δ13CTOC  excursion. This sedimentological and chemostratigraphic record from Tasmania represents a unique high latitude Southern Hemisphere record of climate change through the Triassic with evidence of significant paleoclimatic and environmental change near the South Pole.

How to cite: Al Suwaidi, A., Fox, C. P., Lestari, W. A., Ghosal, I., and Rigo, M.: Wildfires, Weathering and Warming: A High Latitude Southern Hemisphere paleoclimate record of the Triassic from Tasmania, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17314, https://doi.org/10.5194/egusphere-egu23-17314, 2023.

11:15–11:25
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EGU23-2881
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SSP1.3
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On-site presentation
Stephen Grasby, Jeanne Percival, Rod Smith, Jennifer Galloway, and Manuel Bringué

The Smoking Hills Formation of Arctic Canada represents a Cretaceous metalliferous black shale named after auto-combusting exposures in Ingniryuat, Northwest Territories. This area was also named The Smoking Hills by the Franklin Expedition after the ever-present clouds of sulphuric acid smoke produced. Similar burning Cretaceous mudstones occur in Yukon, and northern Alberta, as well as western Greenland (as recorded in the Viking Sagas). These burning shales reflect deposition during OAE 2 and 3 events across the Arctic region. Metal in the Smoking Hills Formation are enriched over 1000x average shale values. The metal concentrations strongly correlate with heulandite content, an alteration product of volcanic glass, suggesting an origin related to volcanic loading. Abundant bentonite beds in the Smoking Hills Formation support deposition during active volcanism. This is further consistent with the eruption history of the High Arctic Large Igneous Province to the north, or Cretaceous arc related volcanics to the west. These metals are now being recycled into the otherwise modern pristine Arctic environment, generating hyper acidic waters (recording negative pH values) with extremely high metal concentrations orders of magnitude higher than safe drinking levels. Cretaceous eruptions are still driving widespread deleterious environmental impact today.

How to cite: Grasby, S., Percival, J., Smith, R., Galloway, J., and Bringué, M.: Volcanos – the gift that keeps on giving, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2881, https://doi.org/10.5194/egusphere-egu23-2881, 2023.

11:25–11:35
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EGU23-16993
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SSP1.3
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ECS
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Virtual presentation
Steffanie Sillitoe-Kukas, Munir Humayun, Thierry Adatte, and Gerta Keller

Major volcanic eruptions like the Deccan have long been invoked as causes of global mass extinctions. Deccan volcanism erupted ~ 600,000 km3 over the span of ~ 700 ka contemporaneously with the end-Cretaceous mass extinction. It has been difficult to establish a correlation between eruption size and extinction intensity because the frequency of eruptions and extent of degassing of individual flows is not well constrained. For example, the eruption of the same amount of lava by high frequency, low effusion flows is less likely to result in a mass extinction than by eruption of low frequency, high effusion flows. This is due to volcanic eruptions outgassing climate perturbing gases SO2 and CO2. When in the atmosphere, SO2 and CO2 could lead to a global climatic catastrophe capable of driving the extinction observed in planktic foraminifera that preceded the end-Cretaceous mass extinction by 200 ka. To determine the role Deccan volcanism played on the extinction it is critical to constrain the eruptive and effusive rates of Deccan eruptions. In addition to SO2 and CO2, volcanoes also emit volatile metals, e.g., Cd, Re, Hg, that form aerosols preserved in contemporaneous sediments. Trace metals, such as Cd, accumulate in sediments, where the excess Cd reflects the intensity of volcanic emissions. In such instances, high frequency, low effusion rate eruptions result in low Cd enrichments, whereas low frequency, high effusion rate eruptions result in high Cd enrichments in sediments. To constrain the eruption tempo of the Deccan, we have performed measurements of elemental abundances on the stratigraphically well-preserved KPg section at Elles, Tunisia. In this report, we conducted a high-resolution study of ~ 90 samples covering ~ 20 ka above the KPg boundary to ~ 350 ka below the KPg boundary. Elemental compositions for ~ 50 elements of Elles sediments were obtained by solution ICP-MS. In some samples, particularly sediments from 100 ka period preceding the boundary, Cd enrichments were eight times that of the upper continental crust (UCC). A lack of correlation between Cd and TOC, Zn, P2O5, and Mo below the boundary suggest the Cd enrichments are not from an influx of biogenic detritus nor from organic burial. Above the boundary, normal shale Cd values representing 25 ka are interpreted here to represent the period between the Ambenali and Poladpur phases. Cadmium as a tracer relates foram-based chronology with the intensity of the Deccan eruption.

How to cite: Sillitoe-Kukas, S., Humayun, M., Adatte, T., and Keller, G.: Cadmium as a tracer of volcanism at the Cretaceous-Paleogene boundary, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16993, https://doi.org/10.5194/egusphere-egu23-16993, 2023.

11:35–11:45
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EGU23-9769
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SSP1.3
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ECS
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On-site presentation
Subham Patra, Kebenle Kesen, and Jahnavi Punekar

The final ~0.5m interval of the Cretaceous-Paleogene (K-Pg) boundary at Bidart (France) constitutes the “Deccan benchmark” interval characterized by taphonomic and geochemical proxies of ocean acidification linked with Deccan volcanism. Planktic foraminifera census and morphometric data reveal a concurrence of dwarfed species, thinner test walls, high test fragmentation of planktic foraminifera and increased relative abundance of Guembelitria spp. Together, these evidences point toward severe biotic stress and a likely calcification crisis in planktic foraminifera in the final ~0.5m (~58 ky) of the late Maastrichtian at Bidart.

In the sediment-water interface, the benthic foraminiferal assemblage increase to a dramatic >100,000 tests/gram, indicating a sediment-starved horizon at the KPB. Interestingly, a sharp increase in the relative proportion of heavily calcified genera like Cibicidoides spp. (~51%), Steinsioeina spp. (~10%) and Coryphostoma spp. (~9%) is also recorded at the KPB. The taphonomic angle to such a record is rejected as the benthic foraminifera fragmentation index does not record the ‘acidification’ event as significantly. Similarly, morphometric analysis reveals average sizes of thick-walled genera like Cibicidoides spp., Steinsioeina spp., Gyroidinoides spp., Praebulimina and Coryphostoma spp. increasing at the KPB and ~0.3m below it. A possible explanation for such a biotic advantage for the individuals building heavily calcified tests could be a carbonate super-saturation led by the extinction of pelagic calcifiers at the KPB. In the benchmark, rare occasions of dwarfing and reduced absolute abundances of calcareous benthic foraminifera imply a lower degree of environmental stress. Similarly, census analysis of agglutinated benthic foraminifera records an increased population within the benchmark, indicating a change in community structure.  Whether such a change is a response to acidification or an artifact of preservation is currently under investigation. Our results support an acidification that was restricted to the surface ocean and resulted in severe (planktic) crisis, with limited effect on benthic foraminifera. This is consistent with a lack of benthic foraminifera extinctions across the K-Pg boundary.

How to cite: Patra, S., Kesen, K., and Punekar, J.: The late Maastrichtian calcification crisis in Bidart (France): a benthic environment perspective, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9769, https://doi.org/10.5194/egusphere-egu23-9769, 2023.

11:45–11:55
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EGU23-5465
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SSP1.3
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ECS
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On-site presentation
Madeleine L. Vickers, Stefano M. Bernasconi, Francien Peterse, Appy Sluijs, Clemens V. Ullmann, Jack Longman, Ella Wulfsberg Stokke, Joost Frieling, David Bajnai, Vincent J. Clementi, Dustin Harper, Mei Nelissen, Henk Brinkhuis, Sverre Planke, Morgan T. Jones, and IODP Expedition Science Party

Sediment cores from the Mid-Norwegian Margin, IODP Expedition 396 recovered several glendonite (calcite) pseudomorphs after cold-water ikaite, CaCO3•6H2O, within sediments deposited during the Paleocene-Eocene Thermal Maximum hyperthermal and the early Eocene greenhouse. This presents an apparent climate paradox, since during this time interval, deep sea bottom water temperatures are not believed to have been lower than c. 10 °C anywhere on Earth, mostly much warmer (Meckler et al., 2022 and references therein), far above temperatures typical for natural ikaite formation (Vickers et al., 2022 and references therein). The glendonites are found in close association with ash horizons from the nearby North Atlantic large igneous province (NAIP), with some actually in the infill of a hydrothermal. This, coupled with the presence of glendonites in sediments of the same age from Svalbard and Denmark (Spielhagen and Tripati, 2009; Vickers et al., 2020), may point to volcanically-driven climate and environmental changes in this region, perhaps on temporal and spatial scales hitherto unresolved by global-scale datasets.

 

Here, we present reconstructed ikaite crystallisation temperatures from clumped isotope palaeothermometry and biomarker sea surface and air temperature reconstructions from glendonite-bearing horizons in ash-rich sediments at four IODP Expedition 396 sites. We find that the glendonites indicate bottom water temperatures considerably lower than the majority of other localities so far studied for this time interval (0 – 10 °C). The biomarker signals are harder to interpret, but may indicate sea surface and air temperatures significantly lower than many other studies across this time interval. We discuss possible causes and mechanisms for this cooling, and the conditions driving ikaite growth, focussing on whether these both may be linked to NAIP volcanism.

How to cite: Vickers, M. L., Bernasconi, S. M., Peterse, F., Sluijs, A., Ullmann, C. V., Longman, J., Stokke, E. W., Frieling, J., Bajnai, D., Clementi, V. J., Harper, D., Nelissen, M., Brinkhuis, H., Planke, S., Jones, M. T., and Science Party, I. E.: Volcanically driven short-term, regional-scale cooling during the early Paleogene Greenhouse?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5465, https://doi.org/10.5194/egusphere-egu23-5465, 2023.

11:55–12:05
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EGU23-5127
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SSP1.3
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ECS
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On-site presentation
Nils Björn Baumann, Marcel Regelous, Anette Regelous, Thierry Adatte, Nicolas Rudolph Thibault, Bo Pagh Schultz, and Karsten Haase

The Paleocene – Eocene Thermal Maximum (PETM) was a global hyperthermal event during which temperatures increased by 6 - 8° C within a few thousand years at the Paleocene - Eocene boundary, and lasted about 250 ka resulting in ocean acidification, anoxia, and marine extinctions. The PETM coincided with the opening of the North Atlantic and the emplacement of the North Atlantic Igneous Province (NAIP). However, because of the short duration of the PETM compared to NAIP volcanism (several Ma), the contribution of NAIP volcanism to these environmental changes is unclear.

Previous studies have used mercury (Hg) enrichments in Paleocene - Eocene sediments as a proxy to link the timing and intensity of NAIP volcanism to the environmental changes at the PETM. However, published Hg and Hg/TOC profiles across the PETM from various locations are different, indicating that Hg is affected by processes other than volcanism. Here we use tellurium (Te), a volatile trace element that is highly enriched in volcanic gas relative to crustal rocks, as an alternative proxy for NAIP volcanism. Te and other trace element concentrations were measured by ICP-MS in sediments from the Fur Formation in Denmark and DSDP Site 550 in the North Atlantic, which span the PETM. Sediments of both study sites are enriched in Te with averages between 200 to 300 ppb and thus exceeding estimated average crustal concentrations of 1 – 5 ppb drastically. In both locations, Te and Te/Nb ratios increase abruptly at the level of the carbon isotope excursion (CIE) onset, remain high during the PETM ‘body’, and decrease towards the end of the main North Atlantic ash phase. The Te variations are not correlated with trace element proxies for anoxia or productivity. The Te data support recent Hg isotope data indicating a brief intense phase of NAIP volcanism initiating at the onset of the δ13C excursion and lasting for a few 100 ka. The coincidence of the main volcanic pulse and the CIE onset suggests that the source of the light carbon may be volcanic, rather than metamorphic.

How to cite: Baumann, N. B., Regelous, M., Regelous, A., Adatte, T., Thibault, N. R., Schultz, B. P., and Haase, K.: PETM onset triggered by intense volcanism in the North Atlantic: evidence from tellurium, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5127, https://doi.org/10.5194/egusphere-egu23-5127, 2023.

12:05–12:15
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EGU23-17367
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SSP1.3
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On-site presentation
Morgan Jones, Christian Berndt, Sverre Planke, Carlos Alvarez Zarikian, Joost Frieling, John M. Millett, Mei Nelissen, and Henk Brinkhuis

The Paleocene-Eocene Thermal Maximum (PETM) around 56 Ma was associated with 5-6 °C global warming, resulting from massive carbon release into the ocean–atmosphere system. One potential driver of hyperthermal conditions was the North Atlantic Igneous Province (NAIP), as both volcanic degassing and thermogenic volatile release during contact metamorphism during its emplacement were large potential emitters of carbon. Despite a broad temporal correlation between NAIP activity and the PETM, the exact relationship is obscured by multiple climate forcings, imprecise geochronological data, uncertainties in the timing and magnitude of volatile fluxes from volcanic and thermogenic sources, and limited availability from crucial NAIP localities that could constrain these unknowns. Here we present new seismic and borehole data for the Modgunn hydrothermal vent complex in the Northeast Atlantic (IODP Sites U1567-U1568). Stable carbon isotope stratigraphy and dinoflagellate cyst biostratigraphy reveal a negative carbon isotope excursion coincident with the appearance of Apectodinium augustum in the vent crater infill. Modern examples of submarine explosion craters suggest they have filled in within decades to centuries, so the preservation of the PETM onset within the Modgunn vent suggests an extremely close temporal correlation between the crate formation and the onset of hyperthermal conditions. Furthermore, the majority of the craters across the entire NAIP are likely to have vented in very shallow water, implying that the vast majority of emitted CO2 and CH4 gases directly entered the atmosphere during eruptions. These findings add considerable weight to the hypothesis that thermogenic degassing aided the initiation of the PETM.

 

How to cite: Jones, M., Berndt, C., Planke, S., Zarikian, C. A., Frieling, J., Millett, J. M., Nelissen, M., and Brinkhuis, H.: Shallow-water hydrothermal venting at the Paleocene-Eocene Thermal Maximum onset, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17367, https://doi.org/10.5194/egusphere-egu23-17367, 2023.

12:15–12:25
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EGU23-17344
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SSP1.3
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Highlight
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On-site presentation
Gerta Keller, Stephen Grasby, and Thierry Adatte

Discovery of impact glass in deep water at El Penon, NE Mexico, revealed a 2m thick impact spherule deposit during excavation of an 8m thick late Maastrichtian sequence [1]. The impact spherules are pristine and undisturbed in the late Maastrichtian. Marly sediments prevailed at the base followed mainly by small rip-up clasts overlain by a 10cm thick layer, which consists only of amorphous molten glass containing occasional planktic foraminifera. Large impact glass spherules 3-5mm in size followed and gradually reduced in size. Up-section the impact spherule size gradually reduced (2mm) but remained abundant and devoid of sediments. Near the top, spherules reduced in size and abundance mixed with marls, ending the impact deposit quietly. Marls and marly limestones followed. Preliminary age determinations identified the impact based on various indicators. 1) Biostratigraphy: First appearance of planktic foraminifer Plummerita hantkeninoides zone CF1 age ~200-kyr pre-KPB. 2) U-Pb dating of Deccan volcanism ~230-kyr pre-KPB. 3) Mercury anomalies of Deccan volcanism EE6 ~215-kyr pre-KPB. 4) Cyclostratigraphy ~230-kyr pre-KPB[2]. Impact glass spherules are ubiquitous in the late Maastrichtian of NE Mexico and the impact is believed to be the source. But these spherules are almost always reworked from older into younger sediments, which eliminates age control. Nevertheless, the reworked Chicxulub impact spherules were always believed the source – but this is no longer tenable. The discovery of pristine impact spherules in NE Mexico at the much older age of 200-kyr to 230-kyr places the Chicxulub impact outside the realm of the KPB mass extinction. However, we know since 2003 the Chicxulub crater predates the KPB, although this fact was always neglected. New mercury data from a dozen localities in NE Mexico reveals further evidence that the Chicxulub impact is linked to the older impact crater. Our data supports Deccan volcanism as primary cause for the KPB mass extinction.

 

 

References:

[1] Keller et al., 2009, Journal of the Geological Society, London

[2] Keller et al., 2020, Global Planetary Change

 

How to cite: Keller, G., Grasby, S., and Adatte, T.: Chicxulub Impact Predates the KPB Mass Extinction by 200-230 kyr;Deccan Volcanism, Mercury and Climate change are main causes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17344, https://doi.org/10.5194/egusphere-egu23-17344, 2023.

Posters on site: Thu, 27 Apr, 10:45–12:30 | Hall X3

Chairpersons: Alicia Fantasia, Thierry Adatte, Eric Font
X3.54
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EGU23-8959
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SSP1.3
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ECS
Lawrence Percival, Niels van Helmond, Guy Plint, Nina Papadomanolaki, Yue Gao, Steven Goderis, and Philippe Claeys

The Cenomanian–Turonian Oceanic Anoxic Event (OAE 2: 94 Ma) marked one of the most severe episodes of climate and environmental change during the Cretaceous Period. The primary feature of this interval was widespread marine anoxia/euxinia, leading to deposition of organic-rich, thinly-bedded, mudstones across the world’s oceans, which in turn caused a pronounced positive shift in δ13C of seawater that is recorded (and characterizes) OAE 2 strata worldwide. The event was also marked by climate warming (with superimposed cooling pulses), biotic stress, and terrestrial perturbations such as increased continental weathering. However, the majority of studied records of OAE 2 were deposited in deep-marine Atlantic and Tethyan settings or European epicontinental basins. Thus, the record of environmental change in other locations or environments is less clear.

 

The Western Interior Seaway (WIS) represented a marine corridor across North America that connected the Arctic and Atlantic marine realms. Thus, understanding the environmental and oceanographic changes in the WIS during OAE 2 is crucial to resolving the wider impact of the event across the global marine realm. Several previous works have focused on sites towards the southern end of the WIS (e.g., Pueblo, Iona Core). In this study, we present a new multi-proxy geochemical dataset from a site in the central–northern part of the Western Interior Seaway: Pratts Landing (western Alberta, Canada). Previous palynological studies have highlighted a southward migration of boreal dinoflagellates during the Plenus Cold Event midway through OAE 2, as well as increased input of terrestrial organic matter. Here, we correlate these data with information from redox, nutrient, and volcanic proxies, and compare the Pratts Landing record with other deep- and shallow-marine records of OAE 2 to gain a wider perspective over the environmental changes that operated in different settings during that time interval. This viewpoint is key for understanding the differences and complexities in how surface phenomena were disturbed during OAE 2, and interpreting geochemical records of different settings during that time interval.

How to cite: Percival, L., van Helmond, N., Plint, G., Papadomanolaki, N., Gao, Y., Goderis, S., and Claeys, P.: Geochemical records of environmental change in the central Western Interior Seaway during the Cenomanian–Turonian Oceanic Anoxic Event (OAE 2), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8959, https://doi.org/10.5194/egusphere-egu23-8959, 2023.

X3.55
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EGU23-11171
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SSP1.3
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ECS
Heiðrikur Mortensen, Rasmus Andreasen, Stéphane Bodin, Hamed Sanei, Thomas Ulrich, Sylvain Richoz, Sofie Lindström, Ambre Luguet, Lawrence Tanner, and Christian Tegner

The end-Triassic mass extinction (ETME; c. 201.6 Ma), one of the so-called “big-five” mass extinctions in the Phanerozoic era, is associated with widespread marine anoxia, ocean acidification, global warming, carbon cycle perturbations (δ13C) and an extinction of diverse marine and terrestrial groups. This extinction is frequently linked to the volcanic activity in the Central Atlantic Magmatic Province (CAMP) which is often cited to explain e.g., the correlative negative carbon excursions across many sections, mutagenesis of land plants by Hg-toxicity, and enrichment of Hg/TOC. Despite this, the exact identification of a volcanic signal in many of these sections is not well constrained. In this study we present high-precision platinum group element (PGE: Ir, Ru, Pt, Pd) and Re data for the Triassic-Jurassic boundary succession at the Kuhjoch section (Austria). These are the first results from our new analytical setup using high-pressure asher digestion, isotope dilution and multi-collector inductively-coupled plasma mass spectrometry for precise determination in low concentration (e.g. ppt) samples such as sediments. The PGE and Re concentrations and patterns vary significantly with stratigraphy. The c. 13 m of clayey sediments above the onset of the extinction (marked by the c. 16 cm thick T-bed) show pronounced enrichment in Pt, Pd and Ir concentrations relative to the under- and overlying carbonate dominated stratigraphy. Their PGE patterns are non-chondritic with Pd/Ir and Pt/Ir similar to CAMP basalts. Normalised for lithology (Al2O3), however, there are no significant variations in Pt, Pd and Ir values below, within and above the clayey sediments. Re and Ru are, however, depleted compared to the other PGEs in the clayey interval, something also observed in some CAMP basalts. One possibility is therefore to interpret the PGE-rich, clayey sediments, including the main extinction interval in the basal portion, as recording increased weathering of CAMP basalts. As the PGE enrichment increases up through the T-bed, this could show that the onset of CAMP weathering and mass extinction would have therefore coincided. However, further work is needed to identify the relative role of CAMP volatile emission during volcanic activity versus post-eruption weathering of basalts.

How to cite: Mortensen, H., Andreasen, R., Bodin, S., Sanei, H., Ulrich, T., Richoz, S., Lindström, S., Luguet, A., Tanner, L., and Tegner, C.: Platinum-group elements of the Kuhjoch section (Austria) link the onsets of weathering of the Central Atlantic Magmatic Province and the end-Triassic mass extinction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11171, https://doi.org/10.5194/egusphere-egu23-11171, 2023.

X3.56
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EGU23-1070
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SSP1.3
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ECS
Baran Karapunar and Alexander Nützel

During the transition from the Paleozoic to the Mesozoic, marine communities went through major changes in clade composition and proportions. A significant shift happened in the proportion between the Paleozoic Evolutionary Fauna and the Modern Evolutionary Fauna. The Permian-Triassic transition also marks the establishment of molluscs as the most diverse and dominant group in marine benthic environments. At the end-Permian, gastropods experienced a mass extinction as all other marine clades, but they showed a remarkable proliferation in the Triassic. As a result, the global species and genus diversity exceeded their maximum diversity during the Permian. However, not all gastropod clades contributed to the remarkable Triassic diversification. Similar to the shift in clade proportions between the Paleozoic and Modern Evolutionary Fauna, the clade proportions within Gastropoda changed at the Permian-Triassic transition as a result of differential diversification and selective extinction. The change in the proportional diversity of individual gastropod clades is most evident in the dwindling of the order Pleurotomariida (Vetigastropoda). Although Pleurotomariida was one of the most diverse and abundant Late Paleozoic gastropod groups, they diversified poorly during the Triassic recovery period compared to other groups. Gastropod diversity peaked in the Carnian (Late Triassic), but many newly evolved Carnian taxa could not pass the upper Carnian boundary, indicating an extinction event in the Carnian. A previous analysis of occurrence data in the Paleobiology Database (PBDB) indicates that among the marine clades, gastropods suffered most from the Carnian biotic crisis. Here, we analyze the generic range through data from the most comprehensive global Triassic gastropod list (2177 species, 429 genera) and the PBDB. The range-through data suggest high extinction rates in the Carnian (45%) compared to extinction rates during previous Triassic ages (5%). The Carnian extinction rates were higher than in the Rhaetian (35%). If singletons are excluded from the analysis, the Carnian still shows the highest extinction rate (16%) when compared with the Early and Middle Triassic ages (1–3%), but lower than in the Rhaetian (33%). Origination rates continuously decrease throughout the Triassic. Shareholder quorum subsampling analysis of the PBDB data indicates that generic extinction rates rose in the Carnian, peaked in the Norian and remained high in the Rhaetian. The analyses of both, range through and occurrence data show persistently high extinction rates throughout the Late Triassic. Altogether the Late Triassic biotic crises seem to impact gastropod diversity as much as the end-Permian mass extinction event.

How to cite: Karapunar, B. and Nützel, A.: Gastropod diversity dynamics at the Paleozoic–Mesozoic transition and the impact of the Carnian biotic crisis on gastropod diversity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1070, https://doi.org/10.5194/egusphere-egu23-1070, 2023.

X3.57
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EGU23-2567
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SSP1.3
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ECS
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Paul Aubier, Stéphane Jouve, Johann Schnyder, and Jorge Cubo

The 24 species of crocodylians, including crocodiles, alligators, caimans, and the gharial, represent the extant diversity of Crocodyliformes. These species poorly reflect the past diversity of this group. Indeed, extinct crocodyliforms include hundreds of species adapted to semi-aquatic but also to terrestrial and marine environments. Characterization of the factors driving the macroevolutionary history of Crocodyliformes has been difficult partially because of this ecological disparity. Indeed, studies working at a global scale (i.e. at the scale of the Crocodyliformes or more inclusive) have yielded ambiguous or even contradictory results. This highlighted the need for smaller-scaled studies, both from a phylogenetic and stratigraphic point of view.

The work presented here is part of this new framework. It focuses on an extinct group of crocodyliforms, the Notosuchia, at a specific time interval, the Cretaceous-Palaeogene (K-Pg) crisis. This group was chosen because of three characteristics that made it relevant for deciphering the factors explaining extinction/diversification events: (1) it is homogeneous regarding the living environments: almost all notosuchians were fully terrestrial; (2) it exhibits a high degree of ecological diversity with diets ranging from strict herbivory to specialized carnivory, including omnivory; and (3) it crosses a major crisis event, the K-Pg crisis. We tested the impact of body size, using skull length as a proxy, and local palaeotemperature, on the survival/extinction, coded as a binary response variable, at the K-Pg crisis using the phylogenetic logistic regression (PLR). We also investigated the evolution of body size throughout notosuchian evolutionary history and its relationship with diet. The analyses were performed on several sets of dated supertrees of Notosuchia: two different node dating methods were used on two different topologies. Furthermore, each species was dated by randomly picking an age included in its stratigraphic interval and 100 supertrees were produced for each sets (400 in total). This allowed to account for the effect of the stratigraphic and phylogenetic uncertainties. Finally, to assess the effect of the Adamantina Formation, of uncertain age and from which a high number of specimens come from, we performed the PLR analyses on all 4 sets of supertrees, including or not all the species belonging to this formation.

We found that local palaeotemperature does not explain the survival/extinction while body size do when all the species from the Adamantina Fm are considered to have faced the crisis: the larger notosuchians were, the higher their probability of survival was. Furthermore, Notosuchia showed a trend towards larger body sizes during the Cretaceous. This trend is driven by the apparition of specialized carnivorous species having significantly larger body sizes than omnivorous ones. Thus, diet rather than just body size might explain the survival/extinction of notosuchians at the K-Pg crisis. Because the relationship between survival and body size is only significant when all the species belonging to the Adamantina Fm are considered to have faced this crisis, we corroborates previous studies which found this formation to have a Laggerstätten effect.

How to cite: Aubier, P., Jouve, S., Schnyder, J., and Cubo, J.: Diet diversity might explain the differencial survival of Notosuchia (Crocodyliformes) at the Cretaceous-Palaeogene crisis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2567, https://doi.org/10.5194/egusphere-egu23-2567, 2023.

X3.58
|
EGU23-11099
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SSP1.3
|
ECS
Dipima Borgohain, Sarat Phukan, and Santanu Banerjee

This study explores sedimentological and stratigraphical implications of glauconites within the upper Cretaceous Mahadek Formation exposed at the Umsohryngkew River section in Meghalaya, India. The succession is overall fining upward, with sandstone dominating the lower part and calcareous shales and limestone bands constituting the upper part of the Mahadek Formation. Glauconite occurs within the impure limestone and shale beds of the upper part of the sequence. The glauconitic section gradationally passes upward to K/Pg boundary above the Mahadek Formation. Textural, mineralogical and chemical analyses were carried out to understand the origin of the glauconite. Petrographic investigation reveals three main types of glauconites, a) pellet b) vermiform c) infilling within bioclasts. The glauconite appears dark green and the long dimension of the glauconite grain averages 200 µm. Occasionally, the glauconite grains may be as long as 500 µm. The glauconite pellets show sharp boundaries and exhibit internal cracks. The content of glauconite grain  is nearly 15-20 % of the rock volume. These are sub-rounded to rounded in shape without showing evidence of transportation. X-Ray Diffraction on air-dried samples reveals very prominent (001) basal reflection at 10.23 Å, with reflections of (020), , , (003) and (060) planes at 4.52 Å, 4.23 Å, 3.66 Å, 3.27 Å, 5.51 Å respectively. On glycolation, the (001) peak shifts from 10.23 Å to 9.95 Å, while  and (003) reflections collapse into one single peak. The peaks get narrower, more symmetrical and sharper after heating the samples at 400oC. Also, the  and (003) reflections show separations into 3.33 Å and 3.30 Å reflections respectively. The X-Ray diffraction characteristics confirm the pure nature of glauconite devoid of any interstratification. FEG-SEM imaging of glauconite grains shows a perfect lamellar structure and corroborates the X-Ray diffraction patterns of glauconites.  Further, the electron microprobe analyses data show average K2O content of the glauconite is 6.5 %, suggesting an evolved variety. The Fe2O3(total) content varies from 2.9 % to 16.8 %, with an average of 9.9 %. While the average content of Al2O3 is 20.3%. The K2O vs Fe2O3 plot (r2= 0.7) shows a strong positive correlation. The inverse correlation (r2 = 0.8) between Fe2O3 and Al2O3 suggests the replacement of Al by Fe at octahedral sites. The averages of MgO, SiO2 are 3.5% and 52.6% respectively. The evolved glauconite within the shelfal Mahadek Formation demarcates the stratigraphic condensation at the top of the transgressive deposits. The formation of glauconite in the late Cretaceous Mahadek Formation is significant because of its stratigraphic preference close to the K/Pg boundary.

How to cite: Borgohain, D., Phukan, S., and Banerjee, S.: Glauconitization within the late Cretaceous Mahadek Formation and its stratigraphic implications., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11099, https://doi.org/10.5194/egusphere-egu23-11099, 2023.

X3.59
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EGU23-17396
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SSP1.3
Nina Lebedeva-Ivanova, Sverre Planke, John M. Millett, Stefan Bünz, Cornelia M. Binde, Ben Manton, Dmitry Zastrozhnov, Christian Berndt, David W. Jolley, and Henk Brinkhuis

Extensive magmatism during the NE Atlantic break-up generated about 6-10 million cubic kilometers of magma in the Paleogene. Magmatic degassing and explosive discharge of thermogenic gases by contact metamorphism is implicated in triggering the Paleocene-Eocene Thermal Maximum (PETM; 56 Ma). In 2022, the CAGE22-5 research cruise collected high-resolution seismic, sub-bottom profiler, and multibeam data across the central and northern Vøring Plateau to tie IODP Expedition 396 Sites U1571 to U1574. One high-resolution P-Cable 3D seismic cube (10.3 by 1.8 km) was collected on the Skoll High, covering both sites U1571 and U1572. The data were fast-track processed with a bin size of 6.1 x 6.1 m. Four Cenozoic sedimentary horizons and the Top Basalt horizon were subsequently interpreted, followed by horizon attribute analyses. The Top Basalt horizon reveals unprecedented details of the nature of the volcanic paleosurface. A faulted and eroded lava horizon characterizes the southeastern part of the cube at 150-250 m below sea floor (bsf) around the U1571 site location. In contrast, in the northwestern part of the cube, the Top Basalt attribute maps reveal a pitted surface and lobate structures with linear ridges with characteristic inter-ridge spacings of a few tens of meters. The pitted basalt surface is mapped in an area of about 5.5 km2 at depths of 250-350 m bsf and drilled by Site U1572. About 270 individual pits have been mapped with radius ranging from about six meters, within the horizontal resolution of the data, to about 50 meters with a mean radius of c. 16 meters. The holes are interpreted as rootless cones, which comprise volcanic craters resulting from the explosive reaction between lava flows which flow over water-saturated sediments. The dimensions of the rootless cones in the Skoll 3D survey are comparable with the field analogue of rootless cones mapped in the Myvatn lake area of NE Iceland. Unlike at Myvatn and at other field analogues, the Skoll3D data allow unique 3D imaging of the rootless cones revealing internal structures and geometries including the base of the cone structures. The cone depths vary from meters to a few tens of meters. The lobate structures are interpreted as separate subaerial lava flows with compressional ridges. These lava flows are similar to outcrop analogue lava flows and compressional ridges imaged by elevation model ISN2016 with a 2x2 m resolution near the Myvatn lake. In conclusion, the interpreted patterns of the basaltic pitted surface within the Skoll3D suggest a wet terrestrial paleoenvironment during effusive volcanism. Unlike in the eastern faulted area of the survey, the extremely well imaged pitted basalt surface of the Skoll3D area did not experience significant erosion, suggesting rapid subsidence and drowning of the paleo-land surface in a low-energy coastal environment. This study demonstrates the unprecedented detail that is possible when high resolution 3D seismic data acquisition is applied to buried volcanic landscapes and opens the potential for unique associated insights in the Northeast Atlantic and further afield.

How to cite: Lebedeva-Ivanova, N., Planke, S., Millett, J. M., Bünz, S., Binde, C. M., Manton, B., Zastrozhnov, D., Berndt, C., Jolley, D. W., and Brinkhuis, H.: Terrestrial Early Eocene Volcanic Paleoenvironment of the Skoll High, Mid-Norwegian Margin, Based on New High-Resolution 3D Seismic Geomorphology, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17396, https://doi.org/10.5194/egusphere-egu23-17396, 2023.

X3.60
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EGU23-11057
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SSP1.3
Thierry Adatte, Marcel Regelous, Hassan Khozyem, Jorge E. Spangenberg, Gerta Keller, Uygar Karabeyoglu, Blair Schoene, and Syed F.R. Khadri

Mercury (Hg) and more recently tellurium (Te) are indicator of large-scale volcanism in marine sediments and provide new insights into relative timing between biological and environmental changes, mass extinctions and delayed recovery. Several studies evaluated the relationship between Hg anomalies in sediments and LIP activity across mass extinction horizons. The bulk (80%) of Deccan Trap eruptions occurred over a relatively short time interval in magnetic polarity C29r. U-Pb zircon geochronology reveals the onset of this main eruption phase 350 ky before the Cretaceous-Tertiary (KT) mass extinction. Maximum eruption rates occurred before and after the K-Pg extinction, with one such pulse initiating tens of thousands of years prior to both the bolide impact and extinction, suggesting a cause-and-effect relationship.

We present a comprehensive high-resolution analysis of Deccan Traps Hg-Te loading, climate change and end-Cretaceous (KPB) mass extinction from a transect, which includes 30 sections deposited in both shallow and deep environments. In all sections, results show that Hg concentrations are more than 2 orders of magnitude greater during the last 100ky of the Maastrichtian up to the early Danian P1a zone (first 380 Ky of the Paleocene). Hg anomalies generally show no correlation with clay or total organic carbon contents, suggesting that the mercury enrichments resulted from higher input of atmospheric Hg species into the marine realm, rather than organic matter scavenging and/or increased run-off. Significant and coeval Hg enrichments are observed in multiples basins characterized by proximal and distal, as well as shallow and deep-water settings, supporting a direct direct fallout from volcanic aerosols. Hg isotope data from Bidart confirm a direct Hg fallout from volcanic aerosols. Te/Th ratios measured in the Goniuk (Turkey), Elles (Tunisia), Gubbio (Italy) and Wadi Nukhul (Egypt) sections show the same trend as Hg/TOC and are consistent with a volcanic origin, albeit a minor extraterrestrial contribution of Hg to the boundary cannot be excluded. Te and Hg are however not correlated with iridium contents in the KPg interval and are consequently not related with impact and maximum eruption rates occurred before and after the K-Pg extinction, with one such pulse initiating tens of thousands of years prior to both the bolide impact and extinction

How to cite: Adatte, T., Regelous, M., Khozyem, H., Spangenberg, J. E., Keller, G., Karabeyoglu, U., Schoene, B., and Khadri, S. F. R.: Timing and Tempo of Deccan volcanism relative to the KPg extinction revealed by Mercury and Tellurium anomalies, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11057, https://doi.org/10.5194/egusphere-egu23-11057, 2023.

X3.61
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EGU23-14272
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SSP1.3
|
ECS
Amy Shipley, Tracy Aze, Catalina Pimiento, Andrew Beckerman, Jennifer Dunne, Jack Shaw, and Alexander Dunhill

The end of the Pliocene (~2.5-3 Mya) saw a period of biotic turnover in marine ecosystems with significant losses in marine megafauna (36% of genera globally) including the giant apex predator, Otodus megalodon. This recently identified extinction event coincided with a period of notable climatic change, with glaciation of the Northern Hemisphere causing a drop in global sea level. A positive correlation has been found between extinction probability and those genera that had high energy requirements and were associated with coastal, shelf habitats. As such, it has been hypothesised that these extinctions may have been driven by sea level drop resulting in loss of shelf area and a reduction in the neritic zone, a highly productive feeding habitat.

Megafauna, and particularly apex predators, are known to play important trophic roles in extant communities yet the ecological consequences of losing these large taxa from marine ecosystems in currently not well understood. Using a trait-based inference model, we reconstructed food webs to assess the impact of this Pliocene extinction event on North Atlantic trophic community structure and dynamics. The model distributes trophic links using rules based on optimal foraging theory and functional traits assigned to every trophic species (e.g., body size, depth distribution and feeding habit). Through analysing the differences in food web topology pre- and post- megafaunal extinction event, we identify consistency in structure and connectedness between taxa within the webs. However, diversity changes within trophic levels and a decrease in competition in the Pleistocene indicates this turnover event did result in changes to the marine ecosystem makeup. Furthermore, our results show that the trophic role held by O. megalodon in the Pliocene appears to have been lost in the Pleistocene, with no other taxa taking its place.

In addition to these findings, we also consider alternate hypotheses that may have impacted megafaunal extinction other than shelf loss. As the North Atlantic possesses areas of long continental shelf, neritic zone habitats may have only been shifted, not lost. Consequently, other factors may have played a more significant role.

How to cite: Shipley, A., Aze, T., Pimiento, C., Beckerman, A., Dunne, J., Shaw, J., and Dunhill, A.: Ecosystem structure changes following a marine megafaunal Pliocene extinction and the role of continental shelf habitat loss, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14272, https://doi.org/10.5194/egusphere-egu23-14272, 2023.

X3.62
|
EGU23-13260
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SSP1.3
Sverre Planke, Christian Berndt, Carlos A A Zarikian, Ritske S Huismans, Stefan Bünz, Jan Inge Faleide, Nina Lebedeva-Ivanova, Dmitry Zastrozhnov, and Expedition Scientists

Continental breakup in the NE Atlantic was associated with mafic magmatism recorded by basalt flows, volcanogenic sediments, magmatic underplates, and intrusive sheet complexes in the nearby sedimentary basins and continental crust. The 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). IODP Expedition 396 drilled 21 holes along three transects on the mid-Norwegian continental margin to sample 1) Paleogene sediments along the Vøring Transform Margin and in hydrothermal vent complexes, and 2) basalt deposits from the Vøring Marginal High into the oceanic Lofoten Basin. A total of 2 km of core were recovered, including more than 350 m of basalt, 15 m of granite, and 900 m of late Paleocene to early Eocene sediments. Wireline logging data were recorded in eight holes. All the sites were located on industry-standard 2D and 3D seismic data. In addition, high-resolution seismic data were acquired in 2020 and 2022 over all the 21 Expedition 396 boreholes and 5 legacy ODP/DSDP sites using R/V Helmer Hansen. The seismic surveys included three P-Cable 3D cubes covering the 14 boreholes on the Modgunn (5), Mimir (5), and Skoll (4) transects. A comprehensive core-log-seismic integration program is ongoing for each site, based on an integration of high-resolution biostratigraphy, core and log based petrophysical data, and seismic modelling. The expedition recovered the first sub-basalt cores on the mid-Norwegian continental margin, recovering 15 m of granite. It furthermore collected the first samples from an Outer High at Site U1574, recovering both pillow basalts and hyaloclastites. These cores documented a shallow marine depositional environment of the emergent Eldhø volcano located near the foot of the Vøring Plateau. Finally, 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, documenting the temporal correlation of intrusive breakup magmatism in the Vøring Basin and a major hypothermal event. Collectively, the Expedition 396 sample archive offers unprecedented insight into tectonomagmatic processes in the NE Atlantic, including links to both rapid and long-term climate variation in the Paleogene.

How to cite: Planke, S., Berndt, C., Zarikian, C. A. A., Huismans, R. S., Bünz, S., Faleide, J. I., Lebedeva-Ivanova, N., Zastrozhnov, D., and Scientists, E.: Breakup Magmatism and Paleogene Paleoenvironment: Initial Results from IODP Expedition 396 on the Mid-Norwegian Continental Margin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13260, https://doi.org/10.5194/egusphere-egu23-13260, 2023.

Posters virtual: Thu, 27 Apr, 10:45–12:30 | vHall SSP/GM

Chairpersons: David Bond, Sverre Planke, Alicia Fantasia
vSG.1
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EGU23-7978
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SSP1.3
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ECS
|
Anna Somlyay, László Palcsu, Gabriella Ilona Kiss, Matthew O. Clarkson, Emma Blanka Kovács, Zsolt Vallner, Norbert Zajzon, and József Pálfy

The end-Triassic mass extinction (ETE) ranks as one of the ’Big Five’ biotic crises in Earth history. The processes that led to the ecosystem collapse are thought to have been triggered by the volcanism of the Central Atlantic Magmatic Province (CAMP). However, there is an ongoing debate about which environmental effect was the main trigger for the extinction. Our research aimed to produce a new uranium isotope dataset from the Triassic-Jurassic boundary section of Csővár and to carry out Earth system modelling to understand the role of anoxia in driving the extinction and/or delaying the subsequent biotic recovery.

The uranium isotope ratio (δ238U) is a novel paleoredox proxy as its application dates back only a few years. The main advantage of the method is that δ238U measured in limestone is a global proxy, i.e. it provides information on the redox conditions of the whole ocean rather than that of the local basin. It can be used to reconstruct the proportion of the global seafloor that was under anoxic conditions during the deposition of the studied sediment. Our δ238U measurements were performed on the NEPTUNE Plus™ MC-ICP-MS instrument at the Institute for Nuclear Research (ATOMKI) in Debrecen. The obtained data represent only the second δ238U dataset from the Triassic-Jurassic boundary worldwide.

The studied Csővár section is suitable for uranium isotopic analyses as the deposition took place in an oxic environment and was continuous across the boundary interval, as proven by biostratigraphy of multiple fossil groups and cyclostratigraphy. The section is of international importance as it was among the first sections in the world where the TJB event was recognized in the carbon isotope record.

We detected a major negative uranium isotope anomaly immediately below the Triassic-Jurassic boundary, which is a global signal and indicates widespread marine anoxia. This anomaly coincides with the previously detected carbon isotope anomaly and Hg peaks, which are associated with the volcanism of the CAMP and mark the extinction horizon. Our results support the hypothesis that volcanism indirectly induced anoxia in the ocean, which may have played a role in triggering the marine ETE.

Using the geochemical data (δ13C, Hg, δ238U) and the astrochronological age constraints of the section, we modelled the coupled behaviour of carbon, phosphorus and uranium cycles after volcanic carbon emissions. The model allowed us to estimate when the anoxic conditions were the most severe in the ocean. Our results suggest that anoxia did not reach its maximum extent during the extinction but only about 200-250 kyr later, when approximately 13% of the global ocean floor may have been depleted in oxygen. This delayed peak of anoxia is probably the result of the later, extrusive phase of the CAMP marked by the prominent Hg peak of the section. Our geochemical and modelling results suggest that marine anoxia played a key role in hindering the biotic recovery after the end-Triassic extinction.

 

This research was supported by the National Research, Development and Innovation Fund (Project No. K135309).

How to cite: Somlyay, A., Palcsu, L., Kiss, G. I., Clarkson, M. O., Kovács, E. B., Vallner, Z., Zajzon, N., and Pálfy, J.: Extensive anoxia after the end-Triassic mass extinction: uranium isotope evidence from the Triassic-Jurassic boundary section at Csővár, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7978, https://doi.org/10.5194/egusphere-egu23-7978, 2023.

vSG.2
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EGU23-710
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SSP1.3
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ECS
|
Pragya Singh, Santanu Banerjee, and Kanchan Pande

The Deccan volcanic province is extensively studied for the occurrence of the K–Pg boundary, Cretaceous mass extinction, associated climate change and biotic crises. The Late Cretaceous volcaniclastic sediments occurring in between the lava flow, known as bole beds, are often overlooked. These bole beds, however, are useful to understand the paleoenvironmental conditions during non-eruptive phases of Deccan volcanism. A comprehensive study involving field, petrography and mineralogical investigations focuses on a few cm to a few m-thick bole beds of variable lateral continuity.

Field observations of bole beds reveal red to green colour and variable geometry i.e., massive, bedded, lensoid etc. Petrographic study reveals differences in textural and mineralogical characteristics of red and green boles. Red boles show an incipient to moderate degree of pedogenesis. The incipiently pedogenised red boles show the dominance of volcanic lithic fragments (lathwork, microlitic and vitric), scoria, plagioclase, and pyroxene. The moderately pedogenised red boles, show dominance of altered basaltic clasts (100 μm to 5 mm), iron glaebules, alteromorph and oxidized fragments set in the fine-grained clayey groundmass. The green bole, however, shows poor pedogenesis, with predominance of volcaniclastic fragments, plagioclase, pyroxene and opaques. The volcanic glasses and minerals in green boles are thoroughly replaced by green clay. X-ray diffraction study shows presence of hematite and 14 Å smectite in red bole. The green bole, however, contains 10 Å celadonite and 14 Å smectite as major clay minerals. FTIR and VNIR spectroscopy further confirm the slight difference in composition of smectite associated with bole beds, i.e., Fe, Al-rich smectite in red boles and Fe, Mg-rich smectite in green boles. Although the original material for forming red and green boles is basalt-derived, the distribution pattern of green boles is not as extensive as red boles. This indicates difference in the paleoenvironment of formation of the two bole beds. The study of red bole suggests its formation in oxic, subaerial conditions. The relatively thick red bole units (up to a few m), showing gradational contact with lower basalt and distinct pedogenic features, mark prominent breaks in Deccan eruptions. However, the cm-scaled red bole units, showing uneven boundary with lower basalt, and containing abundant volcaniclastic fragments, indicate minor breaks in volcanism. Green boles, on the contrary, indicate confined suboxic conditions in local depressions on the Deccan lava flow.

How to cite: Singh, P., Banerjee, S., and Pande, K.: Paleoenvironmental implications of interbasaltic volcaniclastic sediments within Late Cretaceous Deccan volcanics, India, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-710, https://doi.org/10.5194/egusphere-egu23-710, 2023.

vSG.3
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EGU23-11589
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SSP1.3
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ECS
Kebenle Kesen and Jahnavi Punekar

The Cretaceous-Palaeogene (K-Pg) boundary interval is marked by the mass extinction of more than 50% of the larger more specialized Cretaceous planktic foraminifera, followed by the extinction of ~33% generalist species (short-term survivors) (Keller and Abramovich, 2009 Punekar et al., 2014). Adaptation strategies identified in Cretaceous planktic foraminifera assemblages within this biotic-stress interval include changes in the community structure through shifts in abundance of species and diversity decline. Changes on a species level are reported as inter- and intra- specific dwarfing, malformation and test-wall thinning. Guembelitria cretacea is typically small sized triserial species identified as the only long-term survivor of this event. Through this study, we test the ocean acidification hypothesis of the late Maastrichtian planktic stress by understanding the link between species carbonate demand and their survivorship at the K-Pg boundary.

Four-dimensional X-ray microscopy (FDXRM) scans of pristine Cretaceous planktic morphogroups (the globotruncanids, the rugoglobigerinids and the planoheterohelicids) from pristine late Maastrichtian zone CF4 of DSDP 525A (South Atlantic) yield the most accurate estimation of their respective test calcite volume. The average test weights and the FDXRM reference estimates together suggest that the scaling of calcium carbonate for globotruncanids, planoheterohelicids, rugoglobigerinids, w.r.t. the guembelitrids is 10-269ug, 6-28ug and 9-60ug respectively. This scaling is significant in context of the observed survivorship of these morphogroups across the K-Pg boundary interval. The new results establish a preliminary link between the carbonate demand, ocean acidification related carbonate crisis (especially in the late Maastrichtian biozone CF1) and the survivorship of these morphogroups. However, other detrimental environmental factors in this critical stress interval cannot be ignored.

How to cite: Kesen, K. and Punekar, J.: Survivorship of Planktonic Foraminifera in the Cretaceous-Palaeogene Transition: A Carbonate Demand Perspective, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11589, https://doi.org/10.5194/egusphere-egu23-11589, 2023.

vSG.4
|
EGU23-11120
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SSP1.3
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ECS
Sooraj Charthamkudam Prakasan, Jahnavi Punekar, and Brijesh Singh

The Cenomanian–Turonian boundary (CTB; ~94 Ma) marks a period of extreme climate warming, the highest sea-levels of the Phanerozoic, and a turnover in marine microfossils and macroinvertebrates. This boundary interval is marked by black shales that mark a global carbon cycle perturbation and the Oceanic Anoxic Event-2. However, the identification of OAE-2 is complicated by the frequent absence of black shales and/or age diagnostic fossil species, and diagenetic overprinting of δ13C data. This warrants a systematic investigation of other biostratigraphic indicators of the OAE-2 crisis. This study investigates the stratigraphic utility of a microgastropod-dominated shell bed as a key marker within the OAE-2 interval.

A regional lensoidal microgastropod-dominated shell bed (2 to 10 cm thick) is observed in the shallow marine carbonate sequence the of Bagh group of sediments (Narmada basin) in the Karondia, Soyla, Jeerabad, and Rampura outcrops near Manawar, India. Previous reports suggest a Turonian age based on ammonite biostratigraphy. We test the hypothesis that the microgastropods indicate biotic stress in shallow marine environments due to OAE-2. The age diagnostic planktic foraminifera are absent. However, low-diversity benthic and planktic foraminifera assemblages with low oxygen-tolerant species confirm biotic stress in Nodular Limestone Formation. Microfacies studies indicate a low-energy supratidal to upper intertidal environment of deposition for the Nodular Limestone Formation, which bears the microgastropod shell bed. The occurrence of microgastropods in association with opportunist planktic foraminifera (e.g., Muricohedbergella, Planoheterohelix) indicate a pioneering palaeocommunity of generalists that colonized new ecospace on the shelf created by the late Cenomanian-early Turonian transgression in the Eastern Narmada Basin. Similar and coeval microgastropod shell beds have been reported from the Tethyan marginal sites of the Western Saharan Atlas of Algeria (Whiteinella archeocretacea zone, CTB interval), Eastern Desert of Egypt (Vascoceras proprium zones, lowermost Turonian) and Upper Benue Trough, Northeastern Nigeria (Turonian). The diachronous occurrence of microgastropod shell beds at various Tethyan marginal sites may be due to a regional offset in the timing of marine incursion. 

How to cite: Charthamkudam Prakasan, S., Punekar, J., and Singh, B.: Eustatic and environmental implications of a microgastropod shell bed in the Cenomanian–Turonian boundary interval in the Narmada Basin (India), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11120, https://doi.org/10.5194/egusphere-egu23-11120, 2023.

vSG.5
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EGU23-14240
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SSP1.3
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ECS
Brijesh Singh, Jahnavi Punekar, Jorge Spangenberg, and Gerta Keller

The extensively studied Cretaceous-Palaeogene (K-Pg) boundary mass extinction of planktic foraminifera (~66 Ma) has been linked with two catastrophic triggers: the Chicxulub impact (Gulf of Mexico) and Deccan volcanism (India). All the studies of the past three decades have focused on the climate shifts and faunal stress at the K-Pg boundary, and in the final ~200 ky preceding it. However, it is critical to study the events that precede the age and influence of Deccan volcanism to gain perspective on the true magnitude of the biotic crisis at the boundary. This study presents a new high-resolution (at 20-cm intervals) climate and faunal dataset of the entire late Maastrichtian record at the DSDP Site 525A (Walvis ridge, South Atlantic). The DSDP Site 525A offers a relatively continuous sediment record of the late Maastrichtian with near-pristine planktic foraminifera for faunal and stable isotopic analyses, excellent magnetostratigraphy and potential for cyclostratigraphy.

            Our results reveal sediments spanning biozones CF1 through CF7 of the Maastrichtian, a duration of ~6 myr. The updated biozone boundaries have been used to infer the relative ages of the observed faunal and climate shifts. The seven important late Maastrichtian climatic events (E1-7) are clearly identified in stable isotopic (δ13C and δ18O) records of planktic (Rugoglobigerina rugosa) and benthic foraminifera (Cibicidoides cf.). Of these, events E-2, E-4 and E-6 represent relatively warmer climate, whereas events E-1, E-3, E-5 and E-7 are colder climate. Events E-2, E-4 and E-7 correspond to the globally recognized Deccan warming event, mid-Maastrichtian event (MME) and Campanian-Maastrichtian Boundary Event (CMBE), respectively. Based on isotope records, the late Maastrichtian corresponds with four climate shifts. Faunal analysis reveals these events are bracketed within four biozones (CF1-4) and have a species richness of ~50 planktic foraminifera. The census analysis reveals a slightly decreasing diversity in E-4 followed by a uniform diversity in E-3. Further, E-2 witnessed a sharp fall in the diversity trend that reduced to an all-time low of ~20%. Most planktic species (globotruncanids) get extinct in E-2 following the diversity drop. However, Hedbergella spp., Pseudoguenbelina costulata, P.  hariaensis, Heterohelix globulosa, H. rajagopalani, Globigerinella aspera, and Globotruncana arca manage to survive through E-2 and were present in high abundance (~10%). Our long-term study suggests an overall stress built up in the background that must have aided in the K-Pg boundary mass extinction.

How to cite: Singh, B., Punekar, J., Spangenberg, J., and Keller, G.: Late Maastrichtian climatic shifts and faunal upheavals at DSDP Site 525A (South Atlantic): Understand the K-Pg boundary crisis in the long-term perspective, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14240, https://doi.org/10.5194/egusphere-egu23-14240, 2023.