The Ludfordian (~424 Ma) “Lau Event” was the last of three Silurian mass extinctions. It is characterized by one of the largest carbon isotope excursions of the Phanerozoic with bulk rock δ13C increasing to ~8‰ in less than 1.5 million years [1]. Possible explanations include enhanced burial of organic matter driven by marine anoxia, changes to weathering rates, and/or increased nutrient flux to the ocean [2]. However, the underlying driving mechanism remains debated. To better inform on the environmental and climatic conditions during the Lau Event, we investigated the boron, strontium, carbon and oxygen isotopic composition of well-preserved brachiopod specimens recovered from four drill cores in the Baltic Basin of central Lithuania: Vidukle-61, Bebirva-111, Bebirva-108 and Bebirva-110, which define a deeper to shallow shelf transect in the palaeo-tropics of the Rheic Ocean. All cores yielded abundant specimens which were screened by optical microscope inspection to identify pristine clean shell parts for sampling. Trace element analyses confirmed excellent preservation and no clay contamination as evident by Mn/Ca and Al/Ca analyses both <300 µmol/mol for most samples (n=65). Preliminary brachiopod carbon isotope data reveal a δ13C increase by approximately 8‰, corroborating the bulk rock pattern, with brachiopod δ18O values ranging from approximately –7‰ to –2.5‰. Boron isotope analyses are ongoing and will be used to assess changes in seawater pH and atmospheric CO2 levels. Further constraints on seawater chemistry and the age of the samples will be provided from paired 87Sr/86Sr analyses. Our multi-proxy records will provide new knowledge to enhance understanding of this enigmatic event and in assessing the effects of climate changes on past ecosystems.
References
[1] Cramer B.D. & Jarvis I. (2020) Chapter 11 – Carbon Isotope Stratigraphy. Geologic Time Scale 2020, 309-343, https://doi.org/10.1016/B978-0-12-824360-2.00011-5.
[2] Zhang, F, Frýda, J., Fakhraee, M., et al. (2022) Marine anoxia as a trigger for the largest Phanerozoic positive carbon isotope excursion: Evidence from carbonate barium isotope record. Earth and Planetary Science Letters, 584, https://doi.org/10.1016/j.epsl.2022.117421.
[3] Jurikova, H., Garbelli, C., Whiteford, R. et al. (2025) Rapid rise in atmospheric CO2 marked the end of the Late Palaeozoic Ice Age. Nat. Geosci., https://doi.org/10.1038/s41561-024-01610-2.
How to cite: Harbour, B., Jurikova, H., Rae, J., Raddatz, J., Radzevicius, S., Ainsaar, L., Lepland, A., and Prave, T.: New climate reconstruction of the Lau Extinction Event (Late Silurian) from boron isotopes in brachiopods, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16711, https://doi.org/10.5194/egusphere-egu25-16711, 2025.
The impact of the Siberian Traps emplacement led to the extinction of 90% of marine species and 75% of terrestrial species. Due to the 3-5 Mkm³ of magma emitted over about 1Myr as determined by U-Pb dating. The extensive volcanic activity released massive quantities of gases into the atmosphere, particularly carbon dioxide (CO2) and sulfur dioxide (SO2). These emissions came from two main sources: magmatic emissions resulting directly from volcanic activity and thermogenic emissions produced by the intrusion of magmas into carbonate-rich, evaporite-rich, or organic matter-rich sediments within the Tunguska basin. The cumulative carbon emissions from the Siberian Traps are estimated to range between 21 000 and 105 600 Gt.
In the present study we considered the amplitude and timing from CO2 and SO2 degassing on the temperature, pH, δ¹³C and their implications for environmental perturbations during the Siberian Traps and the end-Permian mass extinction. We tested various scenarios and their consequences exploring the role of the volcanic sequence duration, mean size of lava flows, metamorphism and the biosphere.
We reconstructed the large igneous province (LIP) volcanic sequence in which we account for both magmatic and thermogenic emissions throughout the entire duration of the LIP emplacement. The SILLi 1.0 model (Iyer et al. 2018) was employed for the thermogenic emission. Parameters considered in the reconstructed sequence include, the duration of emplacement, the volume of lava flows and sills, the characteristics and age of the sediments intruded by sills, and the isotopic (δ13C) signature of sediments, organic matter and magma.
The environmental consequences of the reconstructed emission sequences were simulated using the biogeochemical model GEOCLIM. This model considers for both the short-term and long-term processes related to volatile emissions allowing for the calculation of changes in ocean temperature and pH, as well as disruptions in the carbon, oxygen, phosphorus, and alkalinity cycles.
We highlight the prevailing role of thermogenic gases to observe any significative changes in pCO2, temperature, pH and HCO32- δ¹³C these changes are specifically enhanced when coal bearing sediment are intruded. When intruded coal bearing sediment can cause the pCO2 and HCO32- δ¹³C to peak up to more than 100ppm and 0.4‰ respectively, over the span of a few centuries.
We demonstrate that the size distribution of flows has very limited impact on the long term tendencies but has a visible one on the short term and that the overall duration of the magmatic sequence has a significant effect. We also show that the collapse of primary productivity amplifies the environmental changes (3 Pal in PCO2, 2°C in temperature and a decrease of more than 1.5‰ in HCO32- δ¹³C) and that the combination of both volcanic processes (magmatic degassing and contact metamorphism degassing) and the biosphere are needed to partly explain the data.
How to cite: Pierron, A., Le Hir, G., Fluteau, F., Ganino, C., Maffre, P., and Goddéris, Y.: Modeling the Consequences of the Siberian Traps, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11056, https://doi.org/10.5194/egusphere-egu25-11056, 2025.
Ostracods are among the most abundant microfossils recorded across the Permian/Triassic boundary (252 million years ago). Their fossil record provides an opportunity to assess the impact of environmental changes on the ecosystem and to understand the main drivers behind the biggest mass extinction event in Earth's history. Previous studies have suggested that rapid temperature increase, widespread anoxia, and ocean acidification were the environmental changes driving the extinction. This study uses secondary ion mass spectrometry (SIMS) to measure the geochemical signal of Changhsingian (late Permian) ostracods from the Southern Alps in Italy. We measured the oxygen isotope ratio (δ18Oostracod) as a proxy for temperature and the carbon isotope ratio (δ13Costracod) to assess carbon cycle perturbations. We compared isotopic signals from ostracods found in two shallow-water sections with corresponding sediment data (δ13Ccarb). Our results show that the δ18Oostracod and δ13Costracod values are similar in the two examined species, and these values parallel the δ13Ccarb recorded in the host sediments. Our findings highlight the value of ostracods as indicators of temperature change, providing insights into the environmental changes preceding the extinction event and its potential drivers. Further analyses of these microfossils will enhance our understanding of the marine ecosystems' response to dramatic climate warming during the Permian-Triassic mass extinction.
How to cite: Gómez Correa, M. A., Frank, A., Wiedenbeck, M., Gliwa, J., Korn, D., Prinoth, H., Kustatscher, E., and Foster, W. J.: Insights into thermal stress during the Permian-Triassic mass extinction using ostracods from the Southern Alps (Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13354, https://doi.org/10.5194/egusphere-egu25-13354, 2025.
The Permian–Triassic mass extinction led to the loss of 80-90% of marine species making it the most catastrophic extinction of the Phanerozoic. The Permian-Triassic transition is characterized by a major clime warming event, major environmental upheaval and a high magnitude mass extinction event. The associated expansion of oxygen minimum zones, even into shallow waters, is commonly considered as a global driver of this extinction. However, while the intensification of deep-water anoxia has been demonstrated utilising U isotopes at multiple sites globally, recent studies have shown increasing evidence for spatial and temporal variability in shallow marine redox conditions across the Permian–Triassic transition. This highlights the need to constrain local redox conditions for shallow marine basins to determine if they were affected by anoxia and to link local redox changes, if any, back to the timing of the extinction event. Here, we present redox sensitive element (Re, V, U and Mo) and rare earth elements and yttrium (REY) data from three shallow marine basins, located in the western Paleotethys (Dolomites, Italy), Neotethys (Antalya, Türkiye), and the Barents Sea (Svalbard, Norway) to understand the role of oxygen availability as an extinction driver in different environmental and latitudinal settings. At all three sites, redox sensitive metal enrichments were observed before the onset of the extinction, suggesting deoxygenation, potentially creating anoxic conditions. However, these enrichments appear to be lithology- rather than redox-driven in the Svalbard section and are not persistent within the Dolomites sections, suggesting only episodic deoxygenation. Furthermore, the Dolomites and Antalya sections generally display lower metal enrichments starting at the extinction onset, suggesting lower oxygenation before the extinction than during it. Seawater-like REY patterns were not preserved at all sections, however, all three localities included sections characterized by negative Ce anomalies typical for oxic seawater conditions during the extinction. This suggests that anoxia was not a driving extinction factor in these shallow marine ecosystems, indicating other extinction mechanisms should be considered.
How to cite: Frank, A., Grasby, S., Buchwald, S., Gomez Correa, M. A., Karapunar, B., Kustatscher, E., Prinoth, H., and Foster, W.: Assessing the role of anoxia as an extinction driver in shallow marine basins during the Permian–Triassic mass extinction., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16641, https://doi.org/10.5194/egusphere-egu25-16641, 2025.
The Early Triassic is a key interval to understand biotic and environmental recovery after the major disturbance of the planetary system at the Permo-Triassic Boundary (PTB). The collapse of biodiversity and the dramatic change of the global carbon cycle are thought to be the result of intrusions of mafic melts of the Siberian Large Igneous Province (S-LIP) into sediments rich in organic matter and evaporites. However, the Early Triassic is marked by a long record of global carbon cycle perturbations, suggesting that severe climatic instability and delayed biotic recovery may go beyond S-LIP volcanism.
To further explore this question, we compiled and constructed a continuous stratigraphic record in the platform-slope sequences of the Nanpanjiang Basin, South China, where bio- and chemostratigraphic control is supported by precise geochronology. We present here a U-Pb zircon-based Bayesian age model integrated with δ¹³C isotope data, providing precise temporal calibration of the carbon cycle fluctuations and of lithostratigraphic and biostratigraphic boundaries over 5.5 million years. This record is calibrated to absolute age via the Bayesian age model relying on 20 published and 6 new high-precision ID-TIMS U-Pb ages of volcanic zircon in interbedded ashes.
Our compilation covers six major δ¹³C excursions, three negative (termed N1 to N3) and three positive ones (termed P1 to P3): The initial sharp negative excursion N1 at the PTB (~252.02 Ma) reflects rapid input of volcanogenic CO₂ from the Siberian Large Igneous Province (S-LIP) activity. An early Griesbachian positive peak P1 (~251.88 Ma) is associated with transient recovery of organic carbon burial in microbial-rich environments. A negative δ¹³C shift (N2) in the Dienerian (~251.40 Ma) coincides with ecological stress and enhanced weathering. A sharp positive excursion P2 at the Dienerian-Smithian transition (~250.39 Ma) reflects carbon sequestration in a dynamic climate regime. The largest negative excursion N3 is found during the middle Smithian thermal maximum (~249.56 Ma) and correlates with the climax of global warming and marine anoxia. The Smithian-Spathian boundary positive excursion P3 (~249.33 Ma) marks a cooling phase and coincides with significant biotic turnover, particularly affecting nektonic faunas. The Spathian interval features a stepwise decrease in δ¹³C (N4; ~248.14 Ma), followed by a broad positive excursion near the Spathian-Anisian boundary (P4; ~246.88 Ma), reflecting stabilization of carbon cycling as ecosystems began recovering. The positive excursions P1 to P4 coincide with 100ky-long gaps in the sedimentary record, related to low sea-level and possibly to presence of continental ice.
Published and new U-Pb zircon and baddeleyite dates put the minimum estimate for intrusive as well as extrusive S-LIP activity into the Dienerian (ca. 251.0-250.0 Ma), pointing to a non-volcanic trigger of the P2, P3, P4, N3, N4 isotope excursions. In summary, the robust U-Pb calibrated early Triassic carbon isotope record is interpreted to reflect the interplay of volcanic influence, intrinsic carbon cycle feedback, and other extrinsic factors, which appear to have paced the alternation between extreme warming and transient cooling phases during the Early Triassic post-extinction recovery, and post-recovery period.
How to cite: Schaltegger, U., Leu, M., Paul, A. N., Widmann, P., Vennemann, T., and Bucher, H.: A high-resolution age model for Early Triassic Carbon isotope fluctuations , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3121, https://doi.org/10.5194/egusphere-egu25-3121, 2025.
The end-Permian event (EPE, c. 252.3–251.9 Ma) resulted in the catastrophic collapse of continental ecosystems, including the extinction of peat-forming Glossopteridales in southern Gondwana. The Sydney Basin, positioned at high southern latitudes (c. 70°S), preserves a detailed Early Triassic continental succession, offering unique insights into past ecosystem destabilisation and recovery dynamics in the wake of the EPE. Here, we present a high-resolution, age-controlled analysis of floral and environmental trends in the region, integrating palynology, geochemistry, and sedimentology.
Palynological data, aided by non-metric multidimensional analysis, revealed distinct floral shifts linked to key climatic events, including the late Smithian thermal maximum (LSTM, c. 250.3–249.6 Ma) and the Smithian-Spathian cooling event (SSE, c. 249.6–249.2 Ma). Carbon isotopic compositions of bulk organic matter (δ13Corg) were used to correlate these shifts with global carbon cycle perturbations. Visible and infrared spectroscopy (HyLogger), combined with sedimentological analysis, determined sediment composition and provenance, while X-ray fluorescence (XRF) provided weathering proxies such as the chemical index of alteration.
The palynological record reveals the ebb and flow of several distinct floristic communities during the first five million years following the EPE. Initial post-collapse ecosystems were dominated by peltasperm seed ferns for c. 200,000 years. This ecosystem was supplanted by voltzialean conifers, which thrived for c. 1.5 million years until their decline during the hyperthermal LSTM. The LSTM interval is demarcated in the Sydney Basin as occurring near the end of a major global negative δ13Corg excursion c. 250.2 Ma. Weathering indices and sedimentology of this interval evidenced drier conditions were at play, likely connected with the co-occurrent global rise in temperature. Furthermore, stress-tolerant isoëtalean lycophytes, such as Pleuromeia, became dominant, reflected by a prolonged acme of associated spores (e.g., Densoisporites nejburgii). Intriguingly, while pleuromeians proliferated at low latitudes soon after the EPE, their dominance in the Sydney Basin is recorded only during the LSTM c. 1.7 million years later, perhaps signalling another phase of gymnosperm ecosystem decline and a delayed upsurge of stress-tolerant floras at south polar latitudes.
The SSE, recognised by a major global positive δ13Corg excursion c. 249.4 Ma, saw the expansion of umkomasialean seed ferns dominated by the iconic Triassic Gondwanan plant Dicroidium. However, the landscape also saw the intermittent emergence of other pleuromeian spores (i.e., Aratrisporites), in addition to fluctuating floristic diversity following the SSE for c. 1.5 million years. Sedimentological data from this interval show widespread Fe-rich mudrocks ("red beds"), likely reflecting better-drained floodplains. HyLogger and XRF data suggest humid, seasonal environments punctuated by drought periods. Although gymnosperm pollen gradually became the most abundant plant microfossil—denoting the long-term reestablishment of gymnospermous forests—the Sydney Basin apparently still lacked the necessary environmental conditions required for coal formation until well into the Middle Triassic.
These findings reveal a staggered, non-linear recovery of high-latitude ecosystems, with alternating dominance of gymnosperm and lycophyte floras persisting until the Early–Middle Triassic boundary (c. 247.2 Ma).
How to cite: Amores, M., Frank, T., Fielding, C., Hren, M., and Mays, C.: The late Smithian thermal maximum and the Smithian-Spathian event were the two primary drivers of Early Triassic floristic changes at high southern latitudes , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-488, https://doi.org/10.5194/egusphere-egu25-488, 2025.
The Late Triassic “megamonsoon” circulation was profoundly perturbed by large igneous province (LIP) volcanism during the so-called Carnian Pluvial Episode (CPE). C-isotope excursions in sedimentary records indicate large CO2 emissions into the exogenic reservoirs of the C-cycle during the CPE. The consequent global warming would have strongly intensified the “megamonsoon”, enhancing the hydrological cycle and perturbing global environment for a relatively long time (1.2–2.5 Myr). However, the pattern of the climate change during the rapid (maximum 110 Kyr) initial Negative C-isotope excursion (NCIE1) of the CPE remains poorly understood. Here, we performed high-resolution C-isotope analyses, major (XRF) and trace (ICP-MS) element analyses, clay mineralogy (XRD) and palynology across CIE-1 in a marine succession from the Dolomites (Italy). We show that in the northwestern Tethys the transition to more persistent wet conditions was interrupted by episodic intervals with “megadroughts” linked to discrete rapid emissions of CO2 in the atmosphere–ocean system. These rapid (<50 Kyr) climate swings severely stressed the floral communities and triggered major changes in silicate chemical weathering, resulted in changes in nutrient delivery and redox conditions in the basin.
How to cite: Alverà, G., Dal Corso, J., Chu, D., Cruciani, G., Roghi, G., Caggiati, M., Song, H., Song, H., Tian, L., Du, Y., Haserbek, T., and Gianolla, P.: Strong climate seasonality at the onset of the Carnian Pluvial Episode in Northwestern Tethys (Late Triassic), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6018, https://doi.org/10.5194/egusphere-egu25-6018, 2025.
Late Triassic Norian records from high-latitude localities and the Paleo-Antarctic circle are extremely limited and relatively understudied. Here, we present new geochemical proxy data measured on samples representing fluvial-lacustrine sediments of the Parmeener Supergroup, Unit 4 from Tasmania, Australia, of Early-Mid Norian age (~216-223 Ma). These records offer a unique opportunity to reconstruct the Norian climate and environmental conditions close to the paleo-South Pole and during an interval of major global climatic and ecological condition transitions following the arid conditions of the Early–Middle Triassic and Carnian Pluvial Episode. The TOC values for these Norian age sediments were found to be generally low (0.1-4%). However, steep increases in the TOC values of up to 30-40% were observed, corresponding to the deposition of several coal seams. XRF and Hylogging data from this part of the core show a rapid increase in kaolinite, smectite, and other clay minerals, suggesting an elevated weathering pattern. Preliminary stable isotope results from this study show δ13Corg values varying from -27.5‰ to -23‰ (vs. VPDB). One steep negative δ13Corg excursion, with values reaching as low as -27.5‰, was observed in the upper part of the core. This negative excursion also coincides with the occurrence of two volcanic tuff layers, likely from the proto-Pacific convergent margin along the Antarctic Peninsula. Previous studies of cores from nearby localities have dated stratigraphically equivalent tuffs to 217.84±0.19 Ma (Calver et al. 2021; DOI: 10.1080/08120099.2021.1888804). Hg/TOC values also show a relative increase associated with the volcanics. δ13Corg data from the core is comparable to other global records (e.g. Sakahogi, Japan; Pignola-Abriola, Italy; and Kennecott Point, British Columbia), which show similar trends of δ13Corg profile, though somewhat lighter values for the Norian.
This multiproxy analysis from Tasmania provides a distinctive and continuous record of climate change in the high-latitude Southern Hemisphere during the Norian, shedding light on the significant climatic and environmental changes that occurred during this time.
How to cite: Al Suwaidi, A., Ghoshal, I., Fox, C., Ohkouchi, N., Ogawa, N., Suga, H., Painkal, M., and Ruhl, M.: The Norian Record of Climatic and Environmental Change in the Paleo-Antarctic , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15797, https://doi.org/10.5194/egusphere-egu25-15797, 2025.
Two-hundred-million years ago, the emission of an estimated 100,000 Gt of CO2 during pulsed eruptions in the Central Atlantic Magmatic Province had dire consequences for the biosphere and resulted in the end-Triassic extinction. The exact causes for the extinction of organisms remain enigmatic, but a complex and drawn-out scenario is emerging that is in line with the pulsed activity in the CAMP. Palynological assemblages obtained from the immediate extinction interval from multiple locations exhibit a remarkable darkening of pollen and spores that is at odds with simple thermal maturation during burial. Here, we investigate this latest Triassic “dark zone”, using the Palynomorph Darkening Index (PDI) obtained from trilete fern spores in the Schandelah-1 core (North Germany) and Classopollis pollen in drill cores from Denmark (Stenlille-4), the United Kingdom (ICDP Prees-2), and Luxemburg (Elvange). Coinciding with a collapse of forest vegetation and the spread of a pioneer fern vegetation, the fern spores’ PDI reaches peak darkness in the uppermost Triletes Beds from Germany and equivalents elsewhere. This darkening event is mimicked in highest PDI values in Classopollis from the upper Lilstock Formation in the Prees-2 core and equivalent beds in the Elvange and Stenlille-4 cores. Controlled heating experiments of Lycopodium spores followed by PDI analyses suggest that latest Triassic darkening of palynomorphs is consistent with frequent surface fires carried in fern savannahs. The ensuing extreme soil erosion during wetter intervals resulted in mass removal of charred organic material in coastal sediments. The impact of continental-scale wildfires during the height of the end-Triassic mass-extinction suggests intense climate change exerting heat stress on vegetation as a major factor in the collapse of terrestrial ecosystems.
How to cite: van de Schootbrugge, B., Hollaar, T., Kent, M., Lomax, B., Meredith, W., Lindström, S., Bos, R., Looy, C., Benca, J., Duijnstee, I., Hesselbo, S., Richoz, S., Vandenbroucke, T., Vermeer, J., Kuhlmann, N., Belcher, C., Waajen, I., Peterse, F., and Nierop, K.: Continental-scale wildfires during end-Triassic greenhouse warming, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17654, https://doi.org/10.5194/egusphere-egu25-17654, 2025.
Eruptions of the Central Atlantic Magmatic Province (CAMP) at 201.6 Ma are linked to the end-Triassic extinction (ETE) on land via competing radiative forcings, which caused extreme alternations in warming and cooling and humidity and aridity (climatic whiplash) [c.f., (1)]. Although ETE effects on land-plant diversity are often described as minor, tropical flora exhibit significant changes in plant physiognomy, paralleling pCO2 and hydrological variations recorded from the same strata.
Most dramatic is the extirpation of the vesicate pollen group exemplified by Patinasporites and Enzonalosporites, known to have low latitudinal preferences. In the Late Triassic Pangean tropics, this likely voltzialian conifer group remained a major component of the palynoflora up to the ETE and the time of the earliest known CAMP lavas, whereas it is progressively rarer or absent in older, more northerly Late Triassic strata, and virtually absent in the paleoarctic. This trend is consistent with the northward drift of central Pangea, but the diachronous last appearances have resulted in some biostratigraphic mischief, if other markers are ignored. Also dramatic is the tropical expansion of the dipteridaceous fern Clathropteris meniscoides. This tough-leaved fern is abundant at mid- to high-latitudes in Late Triassic and Early Jurassic continental units of Pangea but absent from tropical Late Triassic-Early Jurassic assemblages except during the earliest to peak CAMP eruptive interval, where it becomes common or even dominant. In fact, its spores (Granulatisporites and Converrucosisporites) comprise the "fern spike" in the Newark Basin at the ETE (2, 3).
Both of these floral phenomena are inconsistent with warming as an extinction driver during the CAMP episode and instead are consistent with CAMP-driven mega-volcanic winters. A similar pattern is seen among continental tetrapods, where insulated forms (e.g., pterosaurs, dinosaurs, mammals) preferentially survive while all large non-insulated pseudosuchians perish (4).
Cheirolepidaceous conifer leaf and stomatal morphology from deposits show trends related to CAMP events (5). These include short, scale-like leaves with thickened cuticle and sunken stomata that are traditionally interpreted as adaptations to heat and evaporative stress, but are also seen in cold-adapted conifers, suggesting these traits are "poly-tolerance" (6) adaptations. In fact, tropical conifer assemblages directly associated with the ETE have the thickest and shortest leaves of all tropical forms, suggesting adaptations to freezing.
Further, hydrological conditions based on hydrogen isotope data captured in n-alkanes suggest amplified precession and obliquity pacing (7). This observation is consistent with both amplification of the hydrological system during times of CAMP-driven high pCO2 seen in pedogenic carbonates, molecular proxies from chlorophyll degradation products, and volcanic winters reflected in the floral disruption patterns. From these collective observations, we suggest that "climatic whiplash" at seasonal- and Milankovitch-timescales was a critical driver of the continental ETE and associated floral responses, and that such processes may have panned out elsewhere in Earth history.
References:
1, Swain+ 2025 Nature Rev Earth Env 6:35-50. 2, Olsen+ 2002 Science 296:1305. 3, Fowell+ 1994 GSA Spec Pap 288:197. 4, Olsen+ 2022 Sci Adv 8:eabo6342. 5, Cornet 1977 PhD thesis, PA State. 6, McCulloh+ 2022Tree Phys 43:1-15. 7, Landwehrs+ 2022 PNAS 119:e2203818119.
How to cite: Whiteside, J., Olsen, P., and Schaller, M.: Multiple geochemical and paleobiological parameters define a “climatic whiplash” during CAMP volcanism, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16763, https://doi.org/10.5194/egusphere-egu25-16763, 2025.
The emplacement of large igneous provinces (LIPs) is known to be a driver of climate change in Earth’s past. However, the balance of climate warming through CO2 emission and cooling through weathering is poorly understood.
Our study is focussed on the period between 300 and 150 million years ago (Ma), when the supercontinent Pangaea began to rift and break apart, a process which initiated many of the Earth system and evolutionary upheavals that led to the planet’s current configuration. During this time some of the largest LIPs in Earth history were emplaced, sometimes coinciding with mass extinctions. For example, the Siberian Traps (252 Ma), which is the largest continental LIP by volume, and widely thought to be the driver of the End-Permian Mass Extinction7,16–18. Later in the Mesozoic, the Central Atlantic Magmatic Province (CAMP; 201 Ma), the largest continental LIP by area, has been linked to the end-Triassic. Further, the Karoo and Ferrar LIPs (183 Ma) have been implicated in the end-Pliensbachian extinction, and Toarcian anoxic event respectively. To determine if major LIPs could have led to cooling on multimillion year timescales, and to investigate the cumulative impact of numerous LIP emplacements, we use a long-term climate-biogeochemical model (SCION) integrated with the record of LIP emplacement between 300 and 150 Ma. SCION uses a 3D emulated climate, which allows us to move beyond simple consideration of latitude bands to consider intersections of LIPs with local temperature, relief and hydrology, which is essential for estimating weathering—especially considering the prevalence of extensive aridity in Pangaea.
Of the seven LIPs during the breakup phase of Pangea, only the Central Atlantic Magmatic Province (CAMP) drives noticeable long-term cooling in the model, a minor effect (around 1°C) despite emplacement of a very large surface area in the humid tropics. Similarly, only the CAMP imparts a significant change in the long-term Sr isotope record whereas the other LIPs of this period do not. Due to limited areal extents, and emplacement outside tropical weathering zones, we conclude most LIPs have no significant global cooling effect on multimillion year timescales.
How to cite: Longman, J., Mills, B., and Merdith, A.: Flood basalt weathering has a limited role in driving global cooling during the Mesozoic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10786, https://doi.org/10.5194/egusphere-egu25-10786, 2025.
The highest trophic niches in Mesozoic oceans were occupied by multiple, loosely related clades of marine reptiles, which evolved a series of craniodental and postcranial morphologies. The Jurassic and Early Cretaceous are characterized by relative stability of higher taxonomic levels, with three main clades dominated trophic chains: ichthyosaurians, plesiosaurians, and thalattosuchian crocodyliformes. This macroevolutionary picture changes drastically during the ‘middle’ Cretaceous: ichthyosaurians, thalattosuchians, and pliosaurid plesiosaurians disappear, whereas mosasaurids and peculiar xenopsarian plesiosaurians diversify, alongside acanthomorph teleosts, neoselachian sharks, marine turtles, and marine birds. This shift created the unique and somewhat short-lived oceanic trophic webs of the Late Cretaceous. Many of these clade turnovers (although not all) are concentrated during the Cenomanian-Turonian interval, a time known for its climatic volatility.
Project SEASCAPE explores the long-term impact of environmental changes on extinct oceanic top predators. To do so, we combine two main datasets and approaches. Firstly, we carry out phylogeny-informed analyses of extinction selectivity, using a new informal supertree sampling 370 marine reptile lineages. Secondly, we compute macroevolutionary functional landscapes before and after the event(s), based on (to our knowledge) the largest sample of 2D and 3D data on marine reptiles ever assembled. We found that lineages’ extinctions are both elevated and selective during the ‘middle Cretaceous’, targeting different clades at each boundary. Our macroevolutionary functional landscapes show that the weak morphological and functional convergence between Early and Late Cretaceous marine reptiles resulted in assemblages that are clearly dissimilar not only in terms of phenotypes, but also exhibiting biomechanical and functional divergences. This highlights the importance of past extinction events in reshaping the highest tiers of marine trophic webs.
How to cite: Fischer, V., Della Giustina, F., Bennion, R., and MacLaren, J.: How mid-Cretaceous events affected marine top predators, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3100, https://doi.org/10.5194/egusphere-egu25-3100, 2025.
The Mesozoic was punctuated by several Oceanic Anoxic Events (OAE) characterised by widespread black shale deposition and global carbon cycle perturbations. Among them, the OAE2 spanning the Cenomanian-Turonian boundary (~ 94 Ma), has been identified as one of the most severe OAE of the Mesozoic. The OAE2 is characterised by a global > 2‰ positive carbon isotope excursion (CIE) recorded in both inorganic and organic sedimentary material. This CIE is interpreted as a massive burial of 13C-depeleted organic carbon driven by a global decrease in seafloor oxygenation. Previous models suggested that volcanism related to Large Igneous Provinces (LIPs) increased atmospheric CO2 concentrations, thereby increasing, through enhanced continental weathering, oceanic nutrient and primary production in superficial waters, ultimately leading to higher oxygen consumption at depth. However, the role of enhanced weathering and accelerated continental fluxes on marine primary productivity and organic carbon burial during OAE2 remains highly debated, largely due to the difficulty of reconstructing highly resolved changes in terrigenous and organic fluxes from sedimentary records. In this study, we use new extra-terrestrial 3He (3HeET) measurements from hemipelagic marine samples from Pont d’Issole (Vocontian Basin) and Cuba (Western Interior Basin) sections to reconstruct carbonate, organic carbon and terrigenous sedimentation rates and fluxes across the OAE2.
Our results from Pont d’Issole reveal that over 70 % of the 3He in the analysed samples is extra-terrestrial in origin. Assuming a constant flux of 3HeET-bearing Interplanetary Dust Particles, we used 3HeET concentrationsto reconstruct relative changes in sedimentation rates at an unprecedented high resolution (every 15 cm/ 5 ka). Our preliminary results indicate constant terrigenous fluxes (ca 1.6 g/cm²/ka) across different carbonate-rich and carbonate-poor lithologies prior to and across the OAE2 onset. On the contrary, carbonate fluxes plummet (from 26 to 1 g/cm²/ka) prior the CIE. This decrease occurs exactly at the level recording a marked shift towards more radiogenic osmium isotope values, pointing to a possible volcanically triggered collapse of carbonate productivity. Sediments from the Plenus Cold Event (colder and more oxygenated period within the OAE) interval and Cenomanian-Turonian boundary show more modest but significant changes in both terrigenous and carbonate fluxes (from 0.4 to 3 g/cm²/ka and from 0.8 to 11 g/cm²/ka, respectively). Our data also show that organic matter accumulation occurred mostly as short orbitally paced pulses across the entire OAE2 interval with varying responses to changes in terrigenous fluxes. Ongoing 3HeET analyses from Cuba will provide comparative data from a different setting that will be pivotal to determine whether the reconstructed fluxes have a local or geographically widespread significance. The implication of 3HeET data from both locations will be discussed in the context of the debated role of increased detrital input on marine primary productivity and organic carbon burial during the OAE2.
How to cite: Godet, B., Blard, P.-H., Suan, G., Suchéras-Marx, B., Riquier, L., Tibari, B., and Martinez, M.: Using extra-terrestrial 3He to reconstruct terrigenous fluxes and their impacts on marine primary productivity and carbon burial during OAE2, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3672, https://doi.org/10.5194/egusphere-egu25-3672, 2025.
The primary source of Cadmium (Cd) to the environment is volcanic emissions, emitted to the atmosphere in a wide range of particle size and chemical compounds that are easily dispersed by wind. Higher temperature emission sources also release elemental gaseous Cd that then cools and becomes bound to ash particles. Atmospheric transport of volcanic Cd emissions is a function of particle size as well as plume height, with transport of thousands of km possible. In the modern, Cd anomalies in Antarctic ice records are shown to be sourced from long-range transport of volcanic emissions, and Cd anomalies found in Greenland ice cores are shown to be generated by the Laki and Hekla eruptions.
When deposited into oceans Cd is highly soluble and has vertical concentration profiles strongly similar to those of nutrients (e.g. P), suggesting that despite its toxicity to higher life Cd acts as a nutrient for phytoplankton by replacing the Zn cofactor in the enzyme carbonic anhydrase under Zn limited conditions. Cd is exported to sediment as organic matter (OM) bound metal and is subsequently buried or fixed as insoluble Cd sulfide.
Studies of Cd in the geologic record are limited and tend to be focused on use of Cd as an indicator of nutrient levels or paleo-environmental conditions. Enhanced Cd concentrations have also been related to increased drawdown during ocean anoxic events (OAEs) related to enhanced OM preservation and the strong affinity of Cd for sulfide as well as an indicator of basin restriction. Examination of use as a proxy for volcanism has been limited.
Records of Cd levels in sediments deposited during Oceanic Anoxic Event 3 in Arctic Canada, show that at low concentrations (< 10 ppm) Cd has a negative correlation with Zn, consistent with Zn replacement. In contrast, at Cd concentrations above 10 ppm there is strong positive correlation with Zn, suggests a common source enriching both metals. Above 10 ppm, Cd concentrations also show a strong correlation with heulandite, a low temperature alteration product of volcanic glass, suggesting a volcanic origin. This is consistent with abundant bentonite beds with geochemical markers consistent with arc volcanism. This may explain the anomalous high Cd concentrations in late Cretaceous mudstones of northern Canada, and suggest that Cd could be another geochemical marker for enhanced volcanism. However, use of Cd may be more nuanced than other geochemical makers, such as Hg or Te, given its nutrient like properties.
These high Cd levels in OAE3 sediments contaminate surface and groundwaters in the modern, with linkage to human health issues, showing long term impact of volcanism on the environment.
How to cite: Grasby, S.: Can cadmium be used as another proxy for volcanism?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11910, https://doi.org/10.5194/egusphere-egu25-11910, 2025.
The Cretaceous-Paleogene (K/Pg) boundary marks a pivotal moment in Earth's history, defined by one of the five major mass extinction events and significant disruptions in global biogeochemical cycles, including shifts in carbon cycling and ocean chemistry. The Um Sohryngkew River section in Meghalaya, India, represents the most complete K/Pg sequence in the region and is comparable to global shallow marine sites. Its proximity to the Deccan volcanic province makes it a critical location for investigating the environmental stressors associated with Large Igneous Province (LIP) volcanism and their role in mass extinction and biotic recovery.
Late Maastrichtian planktic foraminiferal assemblages at Meghalaya reveal persistent stress, with species richness ranging from 6 to 13 taxa and consistently low absolute abundances (~14 individuals/g). A significant increase in abundance is observed 2.5 meters below the K/Pg boundary, from ~14/g to ~250/g. However, this interval is characterized by a population dominated by opportunistic taxa, particularly Guembelitria spp., which account for over 90% of individuals. While similar patterns are reported at coeval sites like Egypt, the prolonged dominance of Guembelitria spp. at Um Sohryngkew highlights the intense and sustained environmental stress, likely exacerbated by its proximity to the Deccan volcanic province. Assemblages are further characterized by small test sizes (<120 µm), with genera such as Planoheterohelix (8-12k µm2) and Rugoglobigerina (10-20k µm2) being 2–4 times smaller than counterparts at sites like Bidart. Test sizes of Guembelitria, Planoheterohelix, and Rugoglobigerina show further reductions of 10.6%, 10.2%, and 29.2%, respectively, around 60 cm below the K/Pg boundary. This decline aligns with increased test fragmentation, leaching, and elevated mercury levels, strongly indicating intensified volcanic activity and associated calcification stress. The absolute abundance of planktic foraminifera collapses at the K/Pg boundary, marked by a one cm-thick red clay layer enriched in Platinum Group Elements and a pronounced negative carbon isotope excursion. A brief recovery episode occurs ~2.75 meters above the boundary, with a significant increase in species richness and a rise in absolute abundance from ~2 to ~70 individuals/g. However, recovery can be tracked at 13 meters above the boundary, based on greater species richness, higher abundance (~2500 individuals/g), improved test preservation, and larger foraminiferal test sizes. Future studies, including detailed biostratigraphy, chemostratigraphy, and age modeling, will be crucial in refining the timing of extinction triggers, environmental changes, and the pace of recovery.
How to cite: Patra, S., Srivastava, P., Punekar, J., Rawat, S., Martini, A. P. D., Catanzariti, R., Bhadran, A., Girishbai, D., Iangrai, B., and Jovane, L.: Um Sohryngkew River Section, Meghalaya: Re-evaluating stress and recovery in the Cretaceous-Paleogene interval, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10220, https://doi.org/10.5194/egusphere-egu25-10220, 2025.
The relationship between Large Igneous Provinces (LIPs) and major mass extinctions has long been recognized. The K/Pg boundary (KPB) extinction is particularly notable due to the near-simultaneous occurrence of two major catastrophic events: the Deccan volcanism and the Chicxulub impact. To gain a clearer understanding of how volcanic activity drives environmental stress, this study investigates the influence of the Deccan volcanism on ecosystems. Our approach includes detailed species counts alongside isotopic and geochemical analyses of two well-preserved sections from the Mudurnu-Göynük and Haymana basins in Central Anatolia (Turkey).
In the Haymana Basin, δ¹³C measurements from the late Maastrichtian display cyclical fluctuations, reflecting precession-driven climate changes. Each cycle ends with a rapid cooling event, indicated by a positive shift in δ¹⁸O values. Spectral analyses of high-resolution δ¹³C and δ¹⁸O isotopic records from planktonic and benthic foraminifera further confirm the influence of orbital forcing, particularly precession cycles, on Late Cretaceous climate variability. The precession-driven cycles reveal climate variations that influenced primary productivity and ocean stratification. During precessional highs, both planktonic and benthic δ¹³C values increase, accompanied by a decrease in Δ¹³Cplanktonic-benthic values and a shift towards more positive δ¹⁸O values, suggesting enhanced water column mixing. Notably, benthic δ¹³C values are consistently heavier than their planktonic counterparts, which may reflect local upwelling conditions. However, the decreasing trend in productivity marker trace elements such as nickel (Ni) and copper (Cu) raises questions about the persistence and extent of upwelling in the Haymana Basin during this period.
Concurrently, a quantitative analysis of planktic foraminifera reveals a progressive decline in species diversity throughout the late Maastrichtian, with an accelerated decline just before the K/Pg boundary. In the Göynük and Okçular sections, this decline in biodiversity coincides with intervals of low magnetic susceptibility, suggesting a possible link to ocean acidification during the late Maastrichtian. The K/Pg boundary is marked by a distinct reddish oxidized layer, 2-3 mm thick, which signals a sequence of critical events: the abrupt disappearance of large, specialized foraminiferal taxa (e.g., globotruncanids, racemiguembelinids, planoglobulinids), an increase in mercury (Hg) levels, and elevated concentrations of trace elements such as iridium (Ir), tellurium (Te), nickel (Ni), chromium (Cr), and cobalt (Co).
In terms of the faunal response, we observe peaks in Thoracosphaera and Guembelitria cretacea, indicating a collapsed ecosystem following the K/Pg boundary event. In conclusion, our comprehensive analysis of paleontological, isotopic, and geochemical data demonstrates that the detrimental effects of Deccan volcanism began prior to the Chicxulub impact, predisposing marine ecosystems to the K/Pg mass extinction event.
How to cite: Karabeyoglu, U., Adatte, T., Thibault, N., Spangenberg, J., and Regelous, M.: Deccan Volcanism, Precession-Driven Climate Variability, and the Chicxulub Impact, Drivers of Ecosystem Stress and Mass Extinction at the K/Pg Boundary: Insights from the Eastern Tethys Region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18650, https://doi.org/10.5194/egusphere-egu25-18650, 2025.
Posters on site: Thu, 1 May, 16:15–18:00 | Hall X2
The Latest Devonian Hangenberg Event (ca.359 Ma) was one of the largest crises of the biosphere. It was directly responsible for the extinction of about 50 % of marine genera mainly from the pelagic realm such as ammonoids, conodonts and placoderm fish. This extinction is linked to worldwide anoxia caused by global climate changes, but its direct cause remains unidentified and still a topic of many scientific studies. Recently discovered mercury spikes, detected at the the D/C boundary in many parts of the world, present convincing evidence of increased volcanic and hydrothermal activity. Newly, tellurium, along Hg anomalies, has been successfully used to confirm Siberian volcanism at the end of the Permian. Today, the global volcanic tellurium flux often shows greater enrichment in Te compared to other volatile elements like mercury, thallium, or bismuth. Therefore tellurium may prove to be a much more promising indicator of volcanism. There is a lot of data on the Hg chemostratigraphy at the crucial intervals during Phanerozoic. In contrast, our knowledge of tellurium cycles during critical intervals of mass extinctions, LIPs emplacements and biotic crises, is entirely lacking. To investigate this issue, we have examined a succession of deep-water, pelagic sedimentary rocks, encompassing the Devonian–Carboniferous boundary interval in the Novchomok section (southern Uzbekistan) using tellurium chemostratigraphy. Previous studies of this section at the Devonian-Carboniferous boundary, had detected the Hg and Hg/TOC anomalies in marly shales, marls, and carbonates, occurring independently of the facies changes, which imply a volcanic origins of those anomalies. Additionally, the presence of negative δ13Corg excursions reflects a massive release of isotopically light carbon from volcanogenic and thermogenic devolatilization. Our preliminary results of Te contents and Te/Th ratios at the Devonian–Carboniferous boundary in the Tian-Shan are promising. Here we report for the first time large anomalous Te spikes (with maximum values reaching 930 ppb) and an increase in Te/Th ratios, which closely correspond with Hg spikes and a negative shift in ẟ13Corg, and indicate that Te could be promising volcanic activity proxy in deep time intervals.
How to cite: Książak, D. and Rakociński, M.: Tellurium anomalies as signs of intensive volcanic activity around the Devonian-Carboniferous boundary in The South Tian-Shan (southern Uzbekistan), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-236, https://doi.org/10.5194/egusphere-egu25-236, 2025.
The Cretaceous-Paleogene boundary (K-Pg boundary) at 66 million years ago marks one of the most severe mass extinctions through Phanerozoic. A clear peak in abundances of platinum group elements (PGEs) such as iridium (Ir) and osmium (Os) has been observed in clay beds at the K-Pg boundary around the world and is one of the most important pieces of evidence of a massive meteorite impact that could have triggered the mass extinction. A sharp decline in osmium isotope ratio (187Os/188Os) can also be used to detect an extraterrestrial impact. Even though the northwest Pacific is considered to have suffered almost no direct tsunami-like damage, a complete K-Pg boundary has not yet been discovered. Therefore, the discovery of the K-Pg boundary in this region is essential for understanding the environmental changes and ecosystems of the time in distal sites from the impact site, the Yucatan Peninsula in the Gulf of Mexico.
We conducted detailed field surveys and sampling in the Shiranuka Hills, Hokkaido, Japan. Our primary study area was a tributary of the Kawaruppu River, where analysis of magnetostratigraphy, biostratigraphy (foraminifera and calcareous nannofossils), zircon U-Pb dating have identified sedimentary layers from the Upper Cretaceous to the lowermost Paleogene (Takashima et al., 2024). In this study, we measured PGE concentrations and 187Os/188Os ratios to constrain the stratigraphic position of the K-Pg boundary. The 187Os/188Os ratio in the stratigraphic interval of the Upper Cretaceous was approximately 0.6, while that in the interval of the lower Paleogene was approximately 0.4. These values are consistent with those of seawater recorded in pelagic sedimentary rocks (Ravizza and Peucker-Ehrenbrink, 2003; Robinson et al., 2009). Notably, a distinct decrease in the 187Os/188Os ratio was observed in the stratigraphic level between the two intervals, reaching approximately 0.235. High Os concentration has also been confirmed at the same level. These results allow us to identify the K-Pg boundary at that level.
This section was deposited in a tectonically active continental margin, resulting in extremely high sedimentation rates. Our magnetostratigraphic and Os isotope stratigraphic data revealed that the sedimentation rate in this section was at least 40 cm/kyr during the Upper Cretaceous and 24 cm/kyr during the lowermost Paleogene. Consequently, it is expected to provide the highest-resolution record in the world of both terrestrial and marine paleoenvironmental changes across the K-Pg boundary.
[References]
Ravizza, G., & Peucker-Ehrenbrink, B., 2003, Chemostratigraphic evidence of Deccan volcanism from the marine osmium isotope record: Science, 302(5649), p. 1392-1395.
Robinson, N., Ravizza, G., Coccioni, R., Peucker-Ehrenbrink, B., and Norris, R., 2009, A high-resolution marine 187Os/188Os record for the late Maastrichtian: Distinguishing the chemical fingerprints of Deccan volcanism and the KP impact event: Earth and Planetary Science Letters, v. 281, p. 159-168.
Takashima, R., Ota, H., Kuroda, J., Schmitz, M., Hayashi, K., et al., 2024, Integrated stratigraphy and radiometric ages across the K-Pg boundary in Shiranuka Hill, Hokkaido, Japan: Abstract T16-O-12 presented at 131st Annual Meeting of the Geological Society of Japan, Yamagata University, 8-10 September.
How to cite: Ota, H., Kuroda, J., Hayashi, K., Hoshi, H., Sawada, K., Nishi, H., Ishikawa, A., and Takashima, R.: Discovery of evidence of the Chicxulub impact in East Asia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5002, https://doi.org/10.5194/egusphere-egu25-5002, 2025.
The Chicxulub impact in Mexico and Deccan volcanism in India are both associated with the end-Cretaceous mass extinction, but the precise timing of the impact, volcanic eruptions, and environmental changes remains debated, hindering a comprehensive understanding of their respective roles. Geochronological data from Malwa Plateau basalts, located on the northern margin of the Deccan Large Igneous Province (LIP), show that the first pulse of Deccan volcanism coincided with a ∼200 kyr warming event in the Late Maastrichtian, recorded globally in contemporaneous stratigraphic sections. This warming, estimated at 2.5–8°C, has been inferred from δ18O studies on benthic foraminifera, pedogenic carbonate, bivalve shells, and leaf morphology. The timing of this excursion corresponds to the early decline in oceanic 187Os/188Os ratios and rising mercury (Hg) concentrations. The first phase of Deccan volcanism erupted through organic-rich Permian sediments in the Narmada-Tapti rift basin. Direct CO2 emissions from basalt are unlikely to account for the scale of warming observed, unless the eruption rates were extremely high, which conflicts with evidence suggesting lower eruption rates and a longer eruption duration. It is likely that thermal contact metamorphism of the sedimentary rocks was a significant source of CO2 that contributed to the Late Maastrichtian warming event. This study aims to investigate the fate of carbon (C), mercury (Hg), tellurium (Te), and sulfur (S) during the contact metamorphism associated with the first pulse of Deccan volcanism and to assess the role of this process in the global cycles of C, Hg, and S.Our data were derived from measurements of contact aureoles around dikes and sills intruding into organic-rich Permian coal deposits in the Narmada-Tapti rift basin. We focused on total organic carbon (TOC), Hg, Te, and S concentrations. While sediments farther from the intrusions show high TOC (>20%) and notable levels of Hg, Te, and S, samples from the aureoles (5-10 m thick) exhibit a near-total loss of these elements. Vitrinite reflectance values >5% indicate temperatures above 300°C in the aureoles. We present strong evidence for thermal alteration of coals and shales due to dike-sediment interactions, leading to the production of CH4 and CO2 gases. Furthermore, all analyzed sections show significant depletion of TOC, with a distinct zone of negligible Hg levels near the contact areas. Scaling these findings with data from Mittal et al. (2021) and Kubo Hutchison et al. (2023), assuming 50% TOC loss in the contact aureoles, a median dike width of 10 m, a median dike length of 1000 m, and a coal density of 1500 kg/m³, we estimate that approximately 900 Gt of carbon may have been emitted—comparable to the total extrusive outgassing from the Deccan Traps. Our preliminary results suggest that large igneous province (LIP)-scale sill and dike emplacement in organic-rich sedimentary rocks can significantly perturb global C, S, Te, and Hg cycles. Deccan volcanism likely contributed to climate instability during the Late Cretaceous and may have amplified the environmental impacts of the Chicxulub impact.
How to cite: Nils, B., Adatte, T., McKeegan, R., Schoene, B., Keller, G., Eddy, M. P., Regelous, M., and Khadri, S.: Thermal Impact of Deccan Volcanism on Organic Sediments: A Key Factor in Late Cretaceous Climate Instability, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10654, https://doi.org/10.5194/egusphere-egu25-10654, 2025.
The Carnian Pluvial Episode (CPE) is marked by major changes in the climate to significantly more wet and humid conditions, followed by a return to an arid state. This episode is recorded in several stratigraphic sections around the world. The climatic shift is thought to have been driven by perturbation of the global carbon cycle, associated with the emplacement of the Wrangellian Terrain Large Igneous Province (WT-LIP) in the Northern Panthalssic ocean (~231-225 Ma). The event is often linked to the rise and diversification of dinosaurs, major biotic shifts on land along with the establishment of modern ecosystems making it a critical event in Earth's history. Detailed studies of the CPE that examine geochemical evidence of the link to the emplacement of Wrangellia are limited. Here, we present new high-resolution geochemical data, combined with lithological description, of the Carnian in the Knocksoghey Formation sampled throughout the Mercia Mudstone from the Carnduff-2 core, Northern Ireland. The Knocksoghey Formation represents continental sediments, marked by an abrupt shift to increased coarse-grained siliciclastics at the presumed onset of the CPE. These sandy sections are followed by an abundance of anhydrite nodules, with reddish brown mudstones displaying green reduction spots. Multiple proxies, including changes in carbon isotope and elemental compositions, weathering proxies, Hg/TOC variations, and astrochronology, are utilized to assess the temporal link between the emplacement of the WT-LIP and the onset and pulses of the CPE and to determine the potential mechanisms driving the event. The lithological change to increase coarse-grained siliciclastics is preceded by higher Hg concentrations, as well as a negative carbon isotopic excursion in the range of ~3-4 ‰, which points to an increased volcanic activity. This interval, which appears to represent wetter conditions, is followed by sedimentological evidence of more arid conditions marked by increased gypsum followed by a second increase in Hg/TOC. Altogether, further evidence of wetter conditions close to the Carnian–Norian Boundary suggests that volcanism was closely linked to the alternations between an arid and humid climate during the CPE.
How to cite: Mohamed Shahid, M., Al Suwaidi, A., Ossa Ossa, F., and Ruhl, M.: The Carnian Pluvial Episode: Timing and Mechanism, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15284, https://doi.org/10.5194/egusphere-egu25-15284, 2025.
Studies on extant spores belonging to the family of clubmosses (e.g., Lycopodium) have shown that micro-FTIR spectroscopic analyses can reveal the quantity of UV-absorbing compounds (UACs) in the organic walls of the spores and thus be used to reconstruct UV-B radiation and the ozone layer degradation rates at the time of formation of the spore. Here, we present new data from Toarcian age sporomorphs from marine organic-rich marls to shales, deposited in the offshore to shoreface environments from a core from the Paris Basin, France, to evaluate the applicability of this method in the geological record. Our results are integrated with existing high-resolution geochemical and geodynamic data from the core to provide a comprehensive understanding of the system. Understanding the fluctuations in UV-B radiation during the Early Toarcian would allow us to understand whether Karoo and Ferrar Large Igneous Province activity resulted in the release of halides that triggered a depletion of the ozone column in the atmosphere, leading to increased UV-B exposure on Earth’s surface, potentially contributing to environmental and ecological perturbations on land and in the oceans. A quantitative palynofacies analysis performed on 32 samples from the core revealed the presence of anoxic conditions during the deposition of the deeper portion of the core, reflected in the abundance of AOM and lack of sporomorphs and marine elements in the palynological record. On the other hand, the palynological record shows a decrease in AOM and an increase in sporomorphs and marine elements at the passage from the Bifrons Zone to the Variabilis Zone, marking a shift to a shallower marine depositional environment characterised by enhanced continental inputs and decreased oxygen depletion. Previous studies of the early Toarcian Carbon Isotope Interval have revealed teratological pollen and spores from localities in the northern hemisphere, linking these mutations to prolonged exposure to enhanced UV-B radiation. Using micro-FTIR, sporomorph morphology analysis (via SEM), palynofacies models and integrating this with existing data we are able to better link changes in vegetation with LIP activity. Understanding the impact of volcanic activity on atmospheric chemistry and ozone thickness, which increases UV-B rays reaching Earth, would help us grasp their effects on life and how UV-B changes influence mutagenesis in organisms and eventually have a role in extinction events.
How to cite: De Luca, R., Al-Suwaidi, A., Ceriani, A., Spina, A., Gasparrini, M., and Lasseur, E.: Impact of elevated UV-B radiation on Toarcian spores and pollen mutagenesis., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18808, https://doi.org/10.5194/egusphere-egu25-18808, 2025.
