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.

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.

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.

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.

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.

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.

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.

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.

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.

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 δ¹³C_org 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.

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 δ¹³C_TOC  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‰ δ¹³C_TOC 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‰ δ¹³C_TOC  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.

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.

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.

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.

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.

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.

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.

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.