Orals: Wed, 6 May, 08:30–10:15 | Room -2.93
The Cambrian Period (~539 to 487 Ma) was a pivotal time for biotic innovation. Extinction events played an important role in shaping evolutionary patterns throughout this interval, yet first order questions remain regarding the extent, severity, and mechanisms behind Cambrian extinctions. To address this we present a new global database of bradoriids, microscopic bivalved arthropods, spanning the Cambrian to early Ordovician, which we analyse in terms of biotic response to environmental change.
Our analyses reveal that most bradoriid fossils come from well-oxygenated shallow marine facies deposited above storm wave base. Therefore, sea surface temperature, oxygen concentration, and mode of dispersal likely exerted strong controls on distribution of these taxa. A smaller proportion of bradoriid occurrences are from deeper water oxic and dysoxic facies, with the relative proportions of deep water oxic and dysoxic varying throughout the Cambrian. The occurrences of some bradoriid fossils in dysoxic facies suggests that these were either benthic taxa, more resilient to marginal oxygen conditions, or pelagic taxa, that lived in overlying better-oxygenated waters.
From Cambrian Age 3 (~521 to ~514.5 Ma) to Age 4 (~514.5 to 506.5 Ma) there was a poleward shift in bradoriid occurrences, away from equatorial latitudes, coupled with a sharp decrease in the proportion of dysoxic deeper water occurrences and increase in well-oxygenated shallow water occurrences. From Cambrian Age 4 to the Wuliuan Age (~506.5 to 504.5 Ma) there was a further decrease in the proportion of low latitude occurrences but an increase in dysoxic deeper water occurrences, returning to proportions similar to Age 3.
Hyperthermal events have been proposed as the driver for the early Age 4 Sinsk extinction and terminal Age 4 extinction of redlichiid and olenellid trilobites. The apparent stepwise poleward shifts in bradoriid occurrences are consistent with hyperthermal temperature rise exceeding thermal tolerance limits in lower latitudes. From Age 3 to Age 4, the decrease in occurrences from deeper dysoxic facies and proportional increase in shallow oxygenated water facies occurrences is consistent with shoaling of anoxic waters forcing benthic taxa, perhaps already close to their minimum oxygen tolerance, to migrate to shallower waters or perish. Shoaling of dysoxic waters is well evidenced as a kill mechanism during the Sinsk event on the Siberian Platform. Coming out of Age 4 into the Wuliuan, the increased proportion of occurrences in deeper waters suggests that these settings may have become more tolerable again, with a lower risk of exposure to lethally low oxygen concentrations. The similar proportional depth distributions of Age 3 and the Wuliuan contrasts with the distribution observed in intervening Age 4, an interval with known extinction events. The combination of palaeolatitude, depth, and seafloor oxygen concentration influence on bradoriid occurrences suggest that Cambrian Age 4 may have been an interval of profound biotic crisis caused by multiple hyperthermal events.
How to cite: Yanagihara, A., Vandyk, T., Wong-Hearing, T., Harvey, T., Jones, C., Zammit, A., and Williams, M.: Tracking Cambrian environmental perturbation using a new bradoriid arthropod database, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21297, https://doi.org/10.5194/egusphere-egu26-21297, 2026.
The Frasnian-Famennian Kellwasser Crisis (~372 Ma) is one of the most severe marine biocrises of the Phanerozoic Eon. The ecological impact of the Kellwasser Crisis was global in nature and sedimentary sections that record the Kellwasser Crisis commonly contain two organic-rich layers, the Lower Kellwasser (LKW) and Upper Kellwasser (UKW) horizons. This canonical two-step pattern, however, is far from globally uniform and differences in thickness, completeness and lithology are pronounced among depositional settings. Cyclostratigraphic analyses converge in total crisis duration estimates, while high resolution studies reveal substantial differences in the duration and internal structure of the LKW and UKW depending on depositional environment. These differences challenge the assumption that the Kellwasser horizons are isochronous at fine timescales and highlight the need for high-resolution analyses across multiple depositional environments.
To address these uncertainties, we present a cyclostratigraphic and paleoclimatic analysis of a combined sediment core and hand sample dataset of the siliciclastic Walnut Creek section (western New York State, USA). Walnut Creek exhibits a pronounced meter-scale rhythmicity between thicker grey shales and thinner black shale beds that is suggestive of astronomical forcing.
Cyclostratigraphic reconstruction based on XRF analysis indicates a total crisis duration of ~880 kyr, which is consistent with independent estimates from other localities. However, reconstructed durations of ~25 kyr for the LKW and ~8 kyr for the UKW are notably shorter than observed elsewhere. Throughout the crisis interval, black shale deposition in the Appalachian Basin is indicated to be driven by top-down eutrophication linked to precession-paced variations in monsoon strength. The new geochemical and cyclostratigraphic evidence from Walnut Creek demonstrates that the onset of organic-rich LKW and UKW deposition was likely isochronous in the Appalachian Basin and the deeper Rheic Ocean margin, and that astronomical forcing controlled the pacing of the crisis. Notably, the thick organic-rich crisis beds commonly found in deposits from the Rheic Ocean correspond to several, respectively shorter, precession-paced black shale beds at Walnut Creek.
From these findings we identify three first-order factors that locally determine whether LKW and UKW organic-rich horizons formed, how thick they would become, and how long they persisted: (1) the capacity of the hinterland to generate nutrient-rich soils; (2) the sensitivity of the depositional environment to precessional forcing; and (3) the dissipation timescales of oxygen-depleted water masses. Together, these factors explain the global spatial heterogeneity of the geologic expression of the Kellwasser Crisis.
How to cite: Quabeck, J., Klisiewicz, J., Wichern, N., Bialik, O., Over, J., Hinnov, L., Tuskes, K., and De Vleeschouwer, D.: Short Local Expression, Long Global Crisis: Astronomical Constraints on Devonian Kellwasser Event Durations from Walnut Creek (New York State, USA), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11451, https://doi.org/10.5194/egusphere-egu26-11451, 2026.
The end-Permian mass extinction is the most severe ecosystem crisis in the Phanerozoic, profoundly reshaping Earth’s ecosystems on a global scale. How the terrestrial ecosystem was impacted during the crisis remains poorly constrained due to limited fossil records. Especially, there is the lack of a global view of terrestrial ecosystem changes during the mass extinction. Here we combine Earth system simulations with plant fossil records to reconstruct the global distributions of terrestrial biomes across the Permian-Triassic transition. The results show that terrestrial plant extinction initiated in polar regions and gradually extended to lower latitudes. Plants between 50 ºN and 75 ºS were nearly completely extinct, with survival limited to local areas. Concurrently, flora from lower latitudes migrated into polar habitats. Our results provide quantitative global and regional views of terrestrial plant extinction during Earth’s most severe ecosystem collapse, enhancing our understanding of terrestrial biotic responses to extreme environmental change.
How to cite: Liu, Y., Guo, J., and Hu, Y.: Terrestrial plant extinction during the Permian–Triassic ecosystem crisis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11955, https://doi.org/10.5194/egusphere-egu26-11955, 2026.
The Late Triassic Carnian Pluvial Episode (CPE, ~232 Ma) is characterized by significant changes in climate globally, with conditions shifting from arid to humid and wet, followed by a return to arid conditions. The climatic shift, recorded in multiple stratigraphic sections worldwide, is thought to have been driven by a perturbation of the global carbon cycle, associated with the emplacement of the Wrangellian Terrain Large Igneous Province (WT-LIP, ~231-225 Ma). The event is often linked to profound environmental and biotic change, including the rise and diversification of dinosaurs and the establishment of modern ecosystems. Here we present new high-resolution geochemical and sedimentological data from two Carnian successions from Laurasia: the Knocksoghey Formation of the Mercia Mudstone Group in the Carnduff-2 core, Northern Ireland, representing playa-lake and aeolian deposits, and the De Geerdalen Formation, Kapp Toscana Group in the DH-4 core, Longyearbyen, representing deltaic to shallow-marine settings. Together, these sites provide complementary mid- and high-latitude records of environmental change across the Carnian Pluvial Episode (CPE). We integrate carbon isotopes, elemental compositions, weathering indices, clay mineralogy, and Hg/TOC variations to assess the temporal link between the emplacement of the WT-LIP and the onset of the CPE. In the Knocksoghey Formation, the abrupt emplacement of coarser siliciclastic deposits, known as ‘Skerries’, disrupts otherwise monotonous fine-grained red paleosols, interpreted as evidence of enhanced weathering due to the CPE. These deposits are preceded by elevated Hg concentrations, a negative carbon isotope excursion of ~6‰, and concurrent increases in geochemical weathering proxies. Comparisons of Hg/TOC and δ13C data from our records with other localities show a marked increase in the Hg/TOC concurrently with the onset of a stepped negative carbon isotope excursion, similar to other well-characterized LIP-driven climate perturbations (e.g., Toarcian CIE), further supporting the WT-LIP volcanism as the driving mechanism of the CPE.
How to cite: Mohamed Shahid, M., Al Suwaidi, A., Ossa Ossa, F., Ruhl, M., Senger, K., Raine, R., and He, T.: Multiproxy Geochemical Records of the Carnian Pluvial Episode in Laurasia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16830, https://doi.org/10.5194/egusphere-egu26-16830, 2026.
The episodic emplacement of the Central Atlantic Magmatic Province (CAMP) triggered profound perturbations to the global carbon cycle, marked by abrupt pCO2 elevations and climatic/environmental disturbance that led to the end-Triassic mass extinction (∼201.5 Ma). While volcanogenic degassing is recognized as the primary trigger of this environmental crisis, the subsequent Earth system feedbacks, particularly the role of silicate weathering in sequestering excess carbon, remain poorly understood. Resolving the temporal interplay between pulsed magmatic degassing and the weathering of fresh basaltic rock and associated carbon drawdown, is essential for understanding the stability of the global climate systems during extreme greenhouse forcing as well as the drivers of Early Jurassic Earth system recovery. In this study, we utilize the osmium (Os) isotope proxy to disentangle the intricacies of couplings between the global carbon cycle, magmatism and continental weathering.
Seawater 187Os/188Os ratios are highly sensitive to the balance between radiogenic continental runoff and unradiogenic mantle-derived inputs. Given the short residence time of Os (~10–50 kyr), this system can provide a detailed archive of rapid shifts in global weathering fluxes. We present a high-resolution initial seawater Os isotope ratio (187Os/188Osi) record from the Prees Borehole (Cheshire Basin, UK), drilled by the International Continental Drilling Program (ICDP) Early Jurassic Earth System and Timescale (JET) project that offers an exceptionally complete stratigraphic succession across the Triassic–Jurassic transition. Our data, integrated with well constrained carbon-isotopic and biostratigraphic frameworks, reveal stratigraphic fluctuations in sedimentary Os-isotopic compositions that suggest temporal changes in global seawater 187Os/188Osi, and by inference allow tracking of CAMP magmatism and changes in global weathering. By placing these findings in a global context, we demonstrate how the competition between volcanic carbon degassing and new weathering sinks governed the evolution of the global carbon cycle and, consequently, the ocean–atmosphere climatic system, providing a mechanistic framework for the environmental recovery following one of Earth’s most severe biotic crises.
How to cite: Xu, W., Ballabio, G., Hnatyshin, D., Ruhl, M., van Acken, D., Dickson, A. J., and Hesselbo, S. P.: Magmatism and continental weathering linked to carbon cycle change and climatic disturbance across the Triassic–Jurassic transition, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10627, https://doi.org/10.5194/egusphere-egu26-10627, 2026.
The Triassic–Jurassic boundary (TJB) is globally marked by profound environmental change, including disruption of the carbon cycle, global warming, reorganization of sea level, and substantial turnover in marine and terrestrial ecosystems. A characteristic stratigraphic signal of this interval is a negative carbon isotope excursion (NCIE), which is widely correlated and commonly linked to volcanism associated with the Central Atlantic Magmatic Province (CAMP). However, in shallow epicontinental basins, the magnitude and continuity of this signal can be strongly influenced by depositional setting, complicating the distinction between global environmental forcing and local sedimentary overprints. To assess how nearshore environments modulate TJB proxy records, we examine three stratigraphically correlated Upper Triassic–Lower Jurassic nearshore successions spanning a proximal–distal transect across the northeastern Central European Epicontinental Sea (CEES; North German Basin). These archives comprise the delta-influenced Barth 10/65 core (proximal), the shallow-marine Schandelah core (intermediate), and the outer shallow-shelf Moseberg outcrop (distal). We integrate TOC and Rock-Eval data, δ¹³Corg values, and major and trace element geochemistry to reconstruct carbon-cycle perturbations and depositional and redox conditions across the boundary.
All three successions record a NCIE that starts in the latest Rhaetian and reaches minimum values near the Triassic–Jurassic transition. This excursion coincides with a regressive–transgressive reversal and culminates in the earliest Hettangian flooding, linking the North German Basin records to the global end-Triassic carbon-cycle perturbation. Nevertheless, the expression of the NCIE varies systematically along the proximal–distal transect. The Barth 10/65 core exhibits strong siliciclastic dilution, dominantly oxidized Type III–IV kerogen, and a comparatively muted the NCIE (δ¹³Corg ~3.6‰), consistent with high-energy deltaic settings and limited accommodation space. In contrast, the Schandelah and Moseberg sections preserve more pronounced excursions of approximately 5‰ in δ¹³Corg. At Schandelah, the maximum isotope shift occurs during early transgression, whereas Moseberg retains a clearly developed NCIE despite minor stratigraphic truncation across the boundary interval. Moseberg is further distinguished by higher proportions of hydrogen-rich organic matter and enhanced organic-matter preservation associated with short-lived dysoxic conditions. Enrichment factors of redox-sensitive trace elements (Mo, U, Cu, V) indicate predominantly oxic to weakly suboxic conditions at all sites, ruling out sustained anoxia. Collectively, these results demonstrate that depositional position and sea-level–controlled accommodation exert a strong influence on the apparent magnitude and completeness of TJB carbon-cycle signals in nearshore epicontinental settings, underscoring the importance of paleoenvironmental context when comparing boundary records.
How to cite: Mazaheri-Johari, M., Ruebsam, W., Franz, M., Wiesenberg, G., Kaboth-Bahr, S., and Schwark, L.: Spatial Variability in Triassic–Jurassic Boundary Proxy Records Across Nearshore Settings in the Northeast German Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18766, https://doi.org/10.5194/egusphere-egu26-18766, 2026.
The Cretaceous-Paleogene (~66 Ma) boundary marks one of the ‘Big Five’ mass extinctions of the Phanerozoic. The event continues to spark discussion, and stimulating increasing focus on the study of geological records of that boundary, including the development of robust stratigraphic frameworks and new proxies. Some of the most-studied Cretaceous-Paleogene sections are those near the town of Gubbio, located in the Umbria-Marche Basin in Italy. The construction of cyclostratigraphic age models allows for the refined understanding of the timing and pacing of paleoenvironmental effects of Deccan volcanism and the Chicxulub impact. High-resolution X-ray fluorescence derived elemental profiles allow for detailed stratigraphic correlation and paleoenvironmental interpretations that can be checked across stratigraphically equivalent sections across the basin. New integrated proxy records (e.g. platinum group element and mercury concentrations, osmium isotope ratios) featuring both extraterrestrial impact and large-scale volcanism signatures can now be put on a common timeline to allow the decomposition of its relative contributions. This contribution gives an overview of such progress made for these sections over the last decade of research, and to what new insights it leads.
How to cite: Sinnesael, M., Montanari, A., Percival, L. M. E., Schulz, T., de Winter, N. J., Vellekoop, J., De Vleeschouwer, D., Coccioni, R., Koeberl, C., Goderis, S., and Claeys, P.: The Cretaceous-Paleogene boundary at Gubbio: an overview of recent stratigraphic and proxy record updates , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9703, https://doi.org/10.5194/egusphere-egu26-9703, 2026.
The response of deep-sea ecosystems to the Cretaceous–Paleogene (K/Pg) mass extinction is crucial for understanding post-impact carbon-cycle disruptions and benthic ecological resilience. Our research presents a new unbiased quantitative record of deep-water agglutinated foraminifera (DWAF) with high resolution, coupled with calcareous nannoplankton and stable carbon and oxygen isotopes from Gubbio (Umbria-Marche Basin, Italy) ranging from 6.4 m below to 6.4 m above the K/Pg boundary clay. The dataset is based on highly standardized sampling intervals and weights, consistent sample preparation, in an attempt to minimize the Signor–Lipps bias, accurate taxonomic treatment and statistical analysis.
DWAF abundance and benthic foraminifera accumulation rates (BFAR) show an abrupt decline and reduction across the boundary, reaching a minimum point in the earliest Danian and followed by a slow recovery over a few hundred thousand years. The case of productivity collapse parallels with a negative excursion in δ¹³C and shifts in δ¹⁸O, suggesting marine carbon cycle disruption. Shannon H and Dominance D diversity indices, supported by diversity curves, display a sharp reduction in species richness and evenness below and above the boundary. The early Paleocene assemblages are described by low diversity, high dominance, and blooms of opportunistic taxa (Reophax, Spiroplectinella). Lazarus taxa were detected higher in the Danian, along with a gradual increase in BFAR and isotopic values.
Benthic foraminifera and isotopic signals point out a temporary reduction in food supply to the deep water, reflecting an unsteady and short-term Strangelove-like response rather than a true Strangelove Ocean as postulated by previous authors. Additionally, the evidence for the survival of benthic foraminifera, the absence of extensive-scale extinction, and the rapid recovery of BFAR and diversity values, does not fully support the Strangelove Ocean scenario. Instead, our unbiased record shows a short-lived decline in marine productivity, followed by a gradual recovery and ecological reorganization. Our results suggest that deep-sea ecological communities at the Cretaceous–Paleogene boundary were able to withstand the disturbance, and experienced a reduced food supply rather than a complete shutdown of biological productivity.
How to cite: Hikmahtiar, S., Kaminski, M., and Korin, A.: Is There Evidence of A “Strangelove Ocean” After The K/Pg Boundary? A New Unbiased Benthic Foraminiferal Record, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8888, https://doi.org/10.5194/egusphere-egu26-8888, 2026.
The Mississippian constituted a time of important global changes in marine environments. The mid-Tournaisian Event, also called the Lower Alum Shale Event (LASE), was a global anoxic event that occurred ca. 355 Ma ago. This event is related to global transgression connected with increased productivity, sedimentary starvation, collapsed carbonate production, and drastic facies changes from pelagic carbonate sedimentation to the widespread onset of organic-rich black shales, often with phosphate nodules, followed by black siliceous cherts and lydites in pelagic settings in many parts of the world. In contrast to the younger lower-Mississippian event, the Tournaisian Isotope Carbon Excursion (TICE), the LASE was connected with greenhouse climatic conditions associated with increased volcanic activity. The trigger for the mid-Tournaisian event is still a matter of debate, but intense volcanism (including submarine arc and explosive type) and related climate change seems to be a good causes of these environmental perturbation. The LASE interval was previously investigated in terms of high-resolution inorganic geochemistry and framboidal pyrite analyses in the Carnic Alps (Austria), Montagne Noire (France), Rhenish Massif (Germany) and Holy Cross Mountains (Poland), as well as in terms of organic geochemistry in the last area. Paleoenvironmental and paleooceanographic changes during the LASE event must have influenced the global carbon cycle. However, in contrast to inorganic geochemistry, the data on changes in Corg and Ccarb isotope signatures were sparse and of low resolution. The aim of our study was to fill this gap. Positive carbon anomalies were often associated with oceanic water eutrophication, however some of recent studies provide new perspectives for decipher changes in δ13Corg record, and several negative isotope anomalies have been reinterpreted as a primary signal associated with large-scale thermogenic degassing of light isotopically carbon (12C isotope), due to increased volcanic activity. Our isotopic data reveal negative shifts in the Carnic Alps, Montagne Noire, at the beginning of the LASE interval, reflecting a volcanic impact on the global carbon cycle. The record of stable carbon isotopes presents an extremely similar trend in the isotopic curve in the studied sections (except for France), with a negative shift in the lower part of the LASE horizon, and a positive shift in the upper part. The previous results show that on a regional scale, the LASE in the pelagic setting was not uniform, both in terms of redox changes and intensities of volcanism and styles of magmatism. Several regional magmatic centers are considered as potentially responsible for the drastic depositional changes on a local scale and for the bioproductivity increase on a global scale. Their total contribution led to a maximum of climatic warming after the D-C boundary glacial episode, resultant global transgression, and to the development of anoxia in many parts of the world during the mid-Tournaisian, causing extinctions and faunal turnovers in fossil groups that had just recovered from the global Hangenberg Crisis.
This project was financially supported by the grants of the National Science Centre in Poland no. 2023/49/N/ST10/00857.
How to cite: Kucharczyk, J. and Rakociński, M.: Carbon cycle perturbation and paleoenvironmental changes during the Lower Alum Shale Event (mid-Tournaisian, Mississippian) in southern Euramerican shelf and Palaeotethys Ocean , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16352, https://doi.org/10.5194/egusphere-egu26-16352, 2026.
Paleosols preserve critical evidence of past surface conditions and provide key insights into Earth’s environmental evolution. Pedogenetic processes, controlled by parent material, climate, topography, biological activity, and exposure time, record both the duration and intensity of weathering. Micromorphological features in paleosols are particularly valuable for establishing relationships between soil-forming processes and sedimentary structures, supporting robust paleoenvironmental and paleoclimatic interpretations. Permian paleosols from the Paraná Basin, southern Brazil, occur within the Rio do Rasto Formation, which is composed of lacustrine deposits of the Serrinha Member, overlain by aeolian systems, fluvial channels, and overbank successions of the Morro Pelado Member. This study integrates macro- and micromorphological observations with geochemical data (Chemical Index of Alteration – CIA) and mineralogical analyses (X-ray Diffraction – XRD) to reconstruct paleoclimate conditions during paleosol development. Microscale analyses show that variations in clay mineral assemblages and carbonate precipitates strongly control sample coloration, producing whitish, greenish, and grayish tones proportional to carbonate content. The results indicate a predominantly semiarid to arid paleoclimate, characterized by intense wetting–drying cycles, repeated waterlogging, and high evaporation rates. The clay fraction is dominated by expansive clay minerals, particularly smectite, reflecting reduced chemical leaching under seasonal drainage conditions. In contrast, subordinate kaolinite and illite suggest episodic phases of improved drainage and longer subaerial exposure. Pedogenic features such as desiccation cracks, slickensides, bioturbation structures (root traces and burrows), and redoximorphic mottling provide further evidence for soil development under a highly seasonal water regime. Carbonate nodules and evaporitic phases become increasingly abundant toward the top of the stratigraphic succession, indicating a progressive aridification trend associated with the continentalization of Gondwana during the Middle to Late Permian. CIA values demonstrate a regional climatic gradient within the basin, from semiarid conditions in intermediate areas to fully arid, locally evaporitic settings in more distal zones. These results reinforce the value of paleosols as reliable terrestrial paleoclimate proxies and provide new insights into the paleohydrological and climatic evolution of southern Gondwana during the Late Paleozoic. This study contributes to a better understanding of environmental dynamics prior to the Permo–Triassic transition.
How to cite: Paz, C., Bállico, M., Belitzki, L., Manna, M., and Goldberg, K.: Paleoclimate reconstruction from Permian paleosols of the Rio do Rasto Formation, Paraná Basin, Brazil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1262, https://doi.org/10.5194/egusphere-egu26-1262, 2026.
Mutated pteridophyte spores occur abundantly in conjunction with the end-Triassic mass-extinction (ETME), ~201.6 million years ago, one of the ‘Big Five’ mass-extinction events of the past 500 million years. Based on high concentrations of sedimentary mercury (Hg) in beds that contain abundant mutated fern spore fossils, it has been hypothesized that volcanogenic Hg-emission from large-scale volcanism in the Central Atlantic Magmatic Province exerted stress on standing and pioneering vegetation, causing malfunctions in meiosis and the production of malformed pteridophyte spores. Here, we provide the first clear in vivo evidence for anomalously high Hg among the plants that survived and proliferated through the ETME using synchrotron X-ray fluorescence (XRF). Our analysis reveals highly enriched values of Hg within the fronds of the earliest Jurassic fern Phlebopteris angustiloba from southern Germany. Intriguingly, P. angustiloba, a member of the Matoniaceae, is recognized as the parent plant which produced malformed spores within the Deltoidospora-Concavisporites complex that are common in the same beds that contain the fossil fern leaves. Using XRF and X-ray absorption near edge structure (XANES) analyses, we made comparisons between the fossil fern leaves and those of extant ferns growing in high-mercury environments in Slovenia, Slovakia, and the Czech Republic. These comparisons suggest that ferns can tolerate elevated Hg-levels and bind it in their placentas with sulfurous compounds. Our combined analysis of extant and extinct ferns suggests that these traits may have evolved in response to past environments with high concentrations of toxic metals—like those caused by magmatically-triggered mass extinctions—during which metal-tolerant strategies would have greatly enhanced survivorship.
How to cite: van de Schootbrugge, B., Mays, C., Navratil, T., Rohovec, J., Lomax, B., Vogel-Mikus, K., van Konijnenburg-van Cittert, H., Brückner, D., Maas, G., Arkesteijn, M., Lindström, S., and van der Ent, A.: Mercury accumulation and mutagenesis in ferns surviving mass-extinction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5652, https://doi.org/10.5194/egusphere-egu26-5652, 2026.
The critical timespan during the Rhaetian (Norian to Hettangian), and in particular the Triassic–Jurassic transition, is known for the catastrophic end-Triassic mass extinction event (201.6 Ma). This occurred in the context of the breakup of the supercontinent Pangaea, and was accompanied by strong earthquakes and widespread volcanism.
In Luxembourg, the Rhaetian is exceptionally well preserved as a complete stratigraphic sequence in several drill cores (Elvange, Geyershaff, Grouft, and Heedhaff) and has been studied intensively in detail by the authors. It is subdivided in Luxembourg into a lower part, the Mortinsart Formation (Grès de Mortinsart), and an upper part, the Levallois Formation (Argiles de Levallois). The Mortinsart Formation is built up by alternating greyish-green sand-, and black claystones with rare thin black conglomerates and coaly horizons. They are overlain by the Levallois Formation, a very uniform sequence of reddish-brown claystones with thin silt streaks. Furthermore, the Levallois Formation shows numerous horizons with microfold structures in Luxembourg.
These soft-sediment deformation structures (SSDS) are usually interpreted as seismites because they are earthquake-induced and can be observed in the end-Triassic mass extinction interval across Europe. The origin of these is the intense seismic activity, linked to the formation of the Central Atlantic magmatic province (CAMP) caused by the breakup of Pangea.
The Levallois Formation is separated from the underlying Mortinsart Formation by an extremely chaotic, intensively deformed and completely unsorted horizon, which shows flame structures, and vertebrate remains are enriched, including dinosaur bones. The regional distribution and geochemical fingerprints indicate that this could be a tsunamite generated by a potential asteroid impact. However, other causes may also have led to the formation of this horizon. Actually, detailed studies are ongoing.
How to cite: Thein, J., Kuhlmann, N., and Colbach, R.: Sediment deformation structures in the Rhaetian of Luxembourg , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11783, https://doi.org/10.5194/egusphere-egu26-11783, 2026.
The Late Devonian and the Middle Cretaceous are crucial periods in Earth's history and especially interesting in terms of macroevolutionary changes in marine vertebrates’ faunas at this time. The Late Devonian (Kellwasser and Hangenberg events) and mid-Cretaceous (OAE 2) events are linked to climate-controlled marine and oceanic anoxic events and biotic turnovers. These intervals are distinguished by unexpected losses in top predators represented by very characterised placoderm fishes and fish-shaped marine reptiles that were lost during these catastrophic events, respectively. During the Hangenberg crisis, they totally extincted all top predatory placoderm fishes, with the largest known predators of the time, such as Dunkleosteus. The Cenomanian-Turonian Mass Extinction is the second-order event of marine extinction and is among the best studied of any mass extinctions. This event is clearly connected with submarine volcanic-controlled climatic warming and the development of anoxic conditions in the oceans. However, one of the more important changes at this time is the total extinction of the fish-shaped or dolphin-shaped marine reptiles, ichthyosaurs, which were nektonic, very mobile, and adapted to cruising long distances, and their physiological adaptation to air breathers makes them more tolerant to oxygenation of the water column. Therefore, it remains a mystery why ichthyosaurs became extinct roughly 28 million years before the end-Cretaceous mass extinction. Both placoderms, as well as ichthyosaurs, were long-lived predators occupying the highest trophic level. Therefore, they could be more sensitive and exposed to toxic metals (such as mercury) bioaccumulation and their biomagnification in the trophic pyramid. Extensive volcanic activity during these periods should deliver huge amounts of highly toxic Hg to aquatic environments. However, the organic form of Hg with one methyl group called methylmercury (MeHg) is more toxic and dangerous to living organisms because it is almost entirely absorbed by the body and flows into the blood, and methylmercury (besides dimethylmercury) is the most toxic form of Hg. The end-Devonian and OAE 2 were characterised by the expansion of anoxic zones in marine environments. In aquatic settings, the main source of methylmercury is biomethylation of Hg by anaerobic microorganisms, such as sulfate-reducing bacteria (SRB). Consequently, the conditions during these periods might have been conducive to the biomethylation of Hg. Methylmercury has received global attention since the poisoning of thousands of people in southern Japan (Minamata) in the mid-1950s. Our aim is to address the lack of knowledge surrounding the occurrence and impact of MeHg on past ecosystems, especially in the context of macroevolutionary drastic changes in aquatic vertebrates during total extinctions, such as the placoderm at the end-Devonian and the ichthyosaurs at the end-Cenomanian. Until now, we have found MeHg in sediments representing the Kellwasser event (Germany, Thuringia) and the Hangenberg event (Poland, Uzbekistan, Austria, and Oklahoma). While in the Cretaceous, we found large mercury spikes (> 1500 ppb) in the Apennines (Italy), which are promising for the search for methylmercury. We collected more samples from these crucial intervals, which are being analysed.
This project was financially supported by the grant of the National Science Centre in Poland (2023/49/B/ST10/00505).
How to cite: Rakocinski, M., Marynowski, L., Palarz, M., Książak, D., Dubicka, Z., Kucharczyk, J., Staneczek, D., and Krawczyński, W.: The role of mercury biomethylation during end-Devonian and OAE 2 (Cretaceous) biotic perturbations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14681, https://doi.org/10.5194/egusphere-egu26-14681, 2026.
66 million years ago, an asteroid killed the non-avian dinosaurs. It also triggered the extinction of the ammonoids, an iconic and diverse group of shelled cephalopods. Curiously, a far less diverse group of shelled cephalopods survived, the nautiloids. Why did the nautiloids survive, but the ammonoids go extinct? This question is subject to a lively and ongoing debate. Many (not mutually exclusive) hypotheses have been raised, often with some degree of empirical support. For example, nautiloids had larger hatching sizes, which might have allowed them to survive periods of low food availability. Nautiloids also had larger geographic distributions, possibly indicating greater flexibility in response to varying environmental conditions, or a higher chance to end up in refugia post-impact. Drawing on PaleoDB and other published datasets, we collected the largest dataset so far on Maastrichtian shelled cephalopods, combining fossil occurrences, hatching sizes, and body sizes. We present some preliminary findings based on this data.
How to cite: Schmutzer, M., Saupe, E., Klug, C., Tajika, A., Wiese, F., and Witts, J.: Why did ammonoids go extinct but nautiloids survive the end-Cretaceous mass extinction?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5239, https://doi.org/10.5194/egusphere-egu26-5239, 2026.
The Göynük section emerges as a particularly valuable archive, preserving a continuous ~800 kyr stratigraphy from the CF4 to CF1 planktonic foraminiferal zones (~66.8–66.016 Ma), thus capturing the full trajectory of environmental perturbations leading to the KPg boundary. Notably, the progressive rise in planktonic δ¹³C values, peaks in Hg and Te concentrations between ~66.3–66.01 Ma and shifts in both planktonic and benthic δ¹⁸O point to intensified volcanic activity, most likely linked to the Poladpur pulse of the Deccan Traps. These signals—along with enhanced weathering, increased detrital input, and declining magnetic susceptibility—mark a phase of sustained environmental stress well before the Chicxulub impact. The correlation of benthic δ¹³C variability with Te enrichment suggests SO₂-induced ocean acidification and intermittent collapses/reductions of the export production as major ecosystem stress mechanisms during mid-CF2. In the Göynük and Okçular sections, the abrupt extinction of planktonic foraminifera, the sharp negative shift in δ¹³Cbulk, and the suite of impact proxies including trace element enrichments, such as an Ir anomaly at the KPg boundary in Göynük, reflect a robust signal of the Chicxulub event. The juxtaposition of both impact- and volcanism-related markers thus speaks for a compound scenario in which Deccan-driven perturbations fragilized marine ecosystems, while the Chicxulub impact delivered the final blow.
How to cite: Adatte, T., Karabeyoğlu, U., Thibault, N., Joachimski, M., and Regelous, M.: Decoding Late Maastrichtian Events: Volcanism, Ocean Changes, and the Chicxulub Impact in Central Anatolia, Turkey, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7975, https://doi.org/10.5194/egusphere-egu26-7975, 2026.
Tellurium is a highly volatile, chalcophile and moderately siderophile trace element that is strongly enriched in volcanic gases relative to crustal rocks. Like mercury, tellurium concentrations in sediments can therefore represent a proxy for past volcanic activity, allowing the timing of LIP volcanism relative to environmental and biotic change during mass extinction events to be determined. Previous studies reported high Te contents in sedimentary rocks at the Permian-Triassic, Cretaceous-Paleogene and Paleocene-Eocene boundaries, which may be linked to eruption of the Siberian, Deccan, and North Atlantic flood basalts, respectively.
Due to the low abundance of Te in most geological materials, and the relatively high ionization energy of Te, this element is rarely analyzed and its geochemical behavior is poorly understood. We have developed methods for analysis of nanogram amounts of Te (and other trace elements) using desolvating nebulizer ICP-MS. Addition of a single-step cationic exchange preconcentration allows analysis of samples containing ppt levels of Te. Using these methods, we carried out analyses of different geological materials, in order to advance our understanding of the behavior of Te in volcanic and sedimentary systems and assess its potential as a proxy for volcanic activity.
Glacial diamictite composites, previously used to estimate the average composition of the Upper Continental Crust (UCC), yield an average Te concentration of 36.7 ± 0.5 ng/g. Assuming this is representative of average UCC, this enrichment in Te relative to estimates of the primitive mantle (silicate Earth) of about 12 ng/g, despite tellurium’s moderately compatible behavior during mantle melting, may indicate that Te has been concentrated in the UCC due to volcanic and hydrothermal processes.
Deccan flood basalts that have not fractionated sulfide, have low Te concentrations (average 0.94 ppb, n=12) relative to MORB (3 – 5 ppb), suggesting that Te was largely degassed during emplacement of the subaerial Deccan lavas at 66.5 – 65.5 Ma. By contrast, the red boles (fossil soil horizons) interbedded with Deccan lavas, have high Te concentrations of up to 2200 ppb, indicating that significant amounts of Te were released during volcanism, some of which was deposited close to the site of volcanism. This observation agrees with data of several thousand sedimentary rocks from profiles across the K-Pg boundary in Italy, Egypt, Morocco, Turkey and Spain, thus supporting the use of Te as a geochemical proxy for LIP volcanism.
How to cite: Regelous, M., Baumann, N. B., Adatte, T., Rudnick, R. L., Schoene, B., Keller, G., Sharma, N., and Haase, K. M.: From Volcanic Source to Sedimentary Sink - Tellurium as a proxy for LIP volcanism, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10613, https://doi.org/10.5194/egusphere-egu26-10613, 2026.
The Cretaceous/Paleogene (K/Pg) boundary (~66 Ma), at which the mass extinction induced by the Chicxulub impact occurred, is preceded by the onset of Deccan Traps volcanism. According to high-precision radiometric dating, the emplacement of this large igneous province occurred from ~300 kyr prior to ~400 kyr after the boundary, potentially affecting Earth’s global climate before, during, and after the extinction event. Nonetheless, despite refined studies published over the last decade, uncertainties persist regarding the rates of volcanic eruption and outgassing, and whether volcanism played a role in the main climatic events across this interval.
In this study, we generated new high-resolution mercury (Hg) concentration data from the internationally recognized K-Pg sites of Zumaia and Caravaca (Spain) and Walvis Ridge Site 1267 (South Atlantic). Our goal is to establish reliable stratigraphic correlations and develop robust, independent age models to infer the temporal relationship between Deccan volcanism and the paleoclimatic changes recorded in the sedimentary record. We calculate Hg mass accumulation rates (MARs) to investigate the nature of the observed Hg anomalies over time. Measured Hg values and calculated Hg MARs display considerable variability between sections; in some cases, higher Hg anomalies were recorded well before the main phase of Deccan volcanism began. This finding raises questions about the utility of Hg as a standalone proxy. Consequently, we argue that for Hg to be considered a reliable geochemical marker for tracking Deccan volcanism, anomalies must be temporally consistent across distant localities and align strictly with the known eruptive history. Our results point out that the greater fit for the Hg anomalies between the studied sections occurred between ~230 kyr prior and 50 kyr after the boundary. These high Hg values are temporally compatible with the emplacement of the bigger eruptive pulses, i.e. the oldest eruptive pulse which includes Kalsubai-Lonavala subgroups formations, and the Poladpur and Ambenali formations respectively, while not showing any clear track of the fourth eruptive pulse related to Mahabaleshwar formation.
According to the extensive climatic proxies generated over the past decades, the only recognizable global climatic event beyond the K/Pg boundary during this interval is the Late Maastrichtian Warming Event (LMWE). Our Hg and MARs anomalies suggest that during the LMWE, Deccan volcanism was involved to some extent. However, the LMWE onset can be dated to ~60 kyr prior to the onset of the temporally consistent Hg and MARs anomalies, suggesting that Deccan volcanism was not the sole trigger of the LMWE. The temperature increase of the LMWE appears to track the last long eccentricity maximum of the Maastrichtian, as originally proposed by Gilabert et al. (2022), reinforcing the hypothesis that orbital forcing played a significant role in the development of this hyperthermal event. Further studies and age refinement of sedimentary proxies are still required for a better understanding of this episode of Earth’s climatic history.
Gilabert, V., Batenburg, S.J., Arenillas, I., Arz, J.A., 2022. Contribution of orbital forcing and Deccan volcanism to global climatic and biotic changes across the KPB at Zumaia, Spain. Geology 50, 21–25. https://doi.org/10.1130/G49214.1
How to cite: Gilabert, V., Batenburg, S. J., Arz, J. A., Regelous, M., Baumann, N., Ferrer, D., Aparicio, I., and Arenillas, I.: High-resolution mercury (Hg) records across the K/Pg boundary: Assessing Deccan volcanism as a global climatic driver, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13529, https://doi.org/10.5194/egusphere-egu26-13529, 2026.
The Bonarelli event (OAE 2; ~94 Ma) is the second-order extinction event with ~ 26% of marine genera loss, starting from single-celled foraminifera, numerous marine invertebrates, and ending with marine reptiles top predators - ichthyosaurs. Increased submarine volcanic activity is believed to have been the main cause for global climate warming and palaeoceanographic change. Many magmatic centres were active during this period, such as the Caribbean-Columbian Large Igneous Province (LIP), the High Arctic LIP, the Madagascar LIP, the Kerguelen LIP and the Ontong-Java LIP. The close age correspondence between LIPs and biotic overturn suggests that large-scale volcanism could be the main driver of mass extinction. The aim of our research was classic outcrop of the Bonarelli level lying in the Bottaccione Gorge, near Gubbio (Apennines, Italy). To deciphering redox changes at Umbria-Marche basin the U/Th and V/Cr ratios as well as concentration of redox sensitive elements were used (e.g. Mo, U, V, Ni, Cu, Pb, Zn, Se). The values of U/Th ratios in the Bonarelli level (OAE 2) varying from 0.42 to 4.23, while the V/Cr range from 0,59 to 12.48, which is indicative for variable redox conditions ranging from oxic to anoxic-euxinic conditions. More restricted redox conditions in the OAE 2 interval are confirm by enrichments in U (avg. U(EF) = 19.92, Mo (avg. Mo(EF) = 568.45) V (avg. V(EF) = 22.26), Ni (avg. Ni(EF) = 21.04), Zn (avg. Zn(EF) = 53,44) and Cu (avg. Cu(EF) = 47,21. While in the sedimentary background (Scaglia Bianca) values of redox-sensitive trace elements are low e.g. Mo ranging from 0.04to 0.82 ppm, V ranging from 1 to 5 ppb and U often below detection limit (< 0.1 ppm). Volcanic eruptions and submarine hydrothermal activity are the main natural sources of mercury in recent and ancient environments, and are reflected by Hg spikes in sedimentary rocks. We found huge Hg spikes (maximum values >1500 ppb) in the OAE 2 interval with 5 ppb values of sedimentary background of Scaglia Bianca in the classical Bottaccione Gorge. Recently, Hg anomalies were found in the Mentelle Basin, which suggests a regional influence of the Kerguelen LIP located in the Southern Hemisphere. However, our findings of Hg spikes in the Tethys area indicate that the volcanic scenario may be more complex and that the event may be associated with the activity of several, rather than a single, magmatic province. These results are a starting point for research on potential bacterial biomethylation during OAE 2 and the influence of toxic methylmercury on aquatic life, especially top predatory marine reptiles.
This project was financially supported by the grant of the National Science Centre in Poland (2023/49/B/ST10/00505).
How to cite: Palarz, M. and Rakociński, M.: The record of the redox changes and submarine volcanic activity during the OAE 2 event (Cenomanian-Turonian boundary) in the Gubbio area (Apennines, Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19425, https://doi.org/10.5194/egusphere-egu26-19425, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot 3
EGU26-10713 | ECS | Posters virtual | VPS26
Delayed carbon-cycle stabilization and ecological recovery across the K/Pg boundary: evidence from the Um Sohryngkew River section, Meghalaya (India)Tue, 05 May, 14:39–14:42 (CEST) vPoster spot 3
The Cretaceous–Paleogene (K/Pg) mass extinction represents one of the most severe crises in Earth history, with marked regional variations in the tempo of pre- and post-extinction environmental stress and ecological recovery. The Um Sohryngkew River (USR) section of Meghalaya (NE India) provides a unique perspective on stress and recovery dynamics in a marine setting proximal to the Deccan Traps. This study integrates planktonic foraminiferal assemblage data with sedimentological observations and bulk-carbonate δ13C measurements to reconstruct the nature and duration of marine stress and to constrain the timing of ecological and carbon-cycle recovery in the eastern Tethyan realm. This integrated, high-resolution multi-proxy approach was previously lacking for this Deccan-proximal archive, and provides a critical constraint on how volcanogenic forcing modulated K/Pg stress and recovery at regional to global scales.
The late Maastrichtian record at USR indicates highly stressed surface-ocean conditions. Planktonic assemblages are dominated by small opportunistic taxa, particularly Guembelitria cretacea (>80%), with strong dwarfing, dominance of thin-walled morphotypes, poor preservation, and a near absence of heavily calcified taxa (e.g., Pseudotextularia spp., Globotruncana spp.). These assemblage and preservation features point to sustained calcification stress and unfavourable conditions for carbonate production in surface waters, consistent with enhanced nutrient input and surface-water acidification under intensified continental weathering/runoff and volcanogenic CO2 emissions. Following the K/Pg boundary, planktonic foraminiferal abundance (4 tests/g) and diversity remained markedly suppressed through the early Danian. The post-boundary interval is similarly characterised by persistent dominance of small opportunistic taxa (>30%; e.g., Guembelitria spp. and Chiloguembelina spp.) and continued dwarfing, indicating sustained calcification stress and hindered ecosystem rebuilding. Bulk-carbonate δ13C indicates delayed carbon-cycle recovery, beginning only after ~750 kyr at USR compared to ~200–300 kyr at many distal sites. Ecological recovery lagged further, with low diversity and small test sizes persisting for ~2 Myr until biozone P1c, indicating decoupling between carbon-cycle recovery and biological reorganization under continued environmental forcing.
The first robust evidence for ecological improvement appears in planktonic foraminiferal biozone P1c, where assemblages become more diverse and better preserved, test sizes increase, and morphogroup proportions stabilise. These changes suggest improved conditions for calcification, progressive strengthening of the pelagic carbonate system, and a more efficient biological pump. By biozones P1c–P2, community structure indicates that ecological balance was largely restored, and carbonate production increased steadily towards a better-developed carbonate-factory environment. Comparison with global K/Pg records suggests that recovery mechanisms in the USR section broadly mirror global ecological and biogeochemical feedbacks, but their timing is substantially delayed relative to distal sections. Importantly, similar evidence for prolonged stress and delayed recovery has also been documented from the Krishna–Godavari Basin of southern India, supporting a coherent regional pattern in marine environments proximal to the Deccan Traps. Together, these Deccan-proximal records highlight strong spatial heterogeneity in post-K/Pg recovery trajectories, including a delayed return to stable carbon cycling, carbonate production, and ecosystem structure.
How to cite: Patra, S., Punekar, J., Srivastava, P., Rawat, S., Bhadran, A., and Girishbai, D.: Delayed carbon-cycle stabilization and ecological recovery across the K/Pg boundary: evidence from the Um Sohryngkew River section, Meghalaya (India), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10713, https://doi.org/10.5194/egusphere-egu26-10713, 2026.
