Climate change is increasingly being recognized as a driver of modern ecological changes including local extinctions. However, global species extinctions are still rarely attributed to climate change. In contrast, the fossil record offers a rich suite of examples of climate-driven extinctions including mass extinctions. Temperature, oxygen and pH were the dominant climate-related extinction drivers in the marine realm.

Over the last six years, the Germany-based TERSANE research unit with nine collaborating research teams has explored the role of climate changes over timescales ranging from hours to millions of years and genealogical scales from individual organisms to ecosystems. We focused empirically on physiological responses of bivalves, the abiotic and biotic changes across the end-Permian and Pliensbachian-Toarcian hyperthermals, and Phanerozoic-scale patterns focusing on extinction selectivity, body size changes, the role of climate history, and the vulnerability of reef systems across ancient warming events. This talk will summarize TERSANE’s accomplishments focusing on the relevance of results for current climate warming with special reference to different time scales.

How to cite: Kiessling, W. and the TERSANE consortium: Temperature-related stresses as a unifying principle in ancient extinctions (TERSANE), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15404, https://doi.org/10.5194/egusphere-egu23-15404, 2023.

The magnitude of future climate change depends on how Earth's natural carbon reservoirs respond to the changing climate via carbon cycle feedbacks. Yet many of these feedbacks are poorly constrained and are widely acknowledged as a major source of uncertainty in climate projections, particularly into the long-term future. Whilst we can measure carbon cycle feedbacks over the historical period, the future pacing and strength of carbon cycle feedbacks remains uncertain. We do not yet know whether they will collectively amplify or dampen anthropogenic climate change in future or whether carbon cycle tipping point events will be triggered, releasing geologically sequestered carbon to the ocean-atmosphere. Hyperthermal events can serve as partial analogues to anthropogenic climate change and allow us to better constrain carbon cycle behaviour in response to global warming. However, most sedimentary proxy records of hyperthermals at the Earth’s surface record the net environmental change caused by both an initial ‘forcing’ and all subsequent ‘feedbacks’ to that forcing. Disentangling forcing and feedbacks signals across hyperthermals requires further independent constraints on some aspect of the system. The geological record is peppered with examples of past carbon emissions events from large igneous province (LIP) activity, many of which coincide with mass extinction and/or hyperthermal events. Here we show how carbon emissions from a large igneous province (the North Atlantic Igneous Province or NAIP) can be constrained at high resolution entirely independently from environmental proxy records. We further show how an Earth system modelling approach comparing NAIP carbon emissions predictions with proxy records of the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma) can be employed to constrain net global carbon cycle feedbacks to NAIP carbon emissions. Lastly, we show how the addition of carbon and trace metal isotope systems in this Earth system modelling framework has the potential to allow us to disentangle individual global carbon cycle feedbacks across events like the PETM, ‘fingerprinting’ the carbon reservoirs and quantifying their response to a known exogenic carbon input.

How to cite: Greene, S., Jones, S., Adloff, M., Doherty, D., and Ridgwell, A.: Quantifying carbon cycle feedbacks to past hyperthermal events, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14942, https://doi.org/10.5194/egusphere-egu23-14942, 2023.

The Phanerozoic Eon is littered with high temperature perturbations which relate to large igneous province (LIP) volcanism. Each of these events occurred against a different climatic and biogeochemical backdrop, and had biotic effects ranging from negligible to extreme. In this talk I will cover the progress we have made with the climate-biogeochemical model SCION, which aims to reconstruct the long-term Phanerozoic climate state as well as these individual hyperthermal events. I will investigate the differences in the amount of carbon that is required to drive the events in the model, versus what is known from the geology of the LIPs themselves. I will then try to suggest solutions to these problems, which may lie in the biotic or biogeochemical responses to climate warming.

How to cite: Mills, B.: How well do we understand Phanerozoic hyperthermals? Investigations with a climate-biogeochemical model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9922, https://doi.org/10.5194/egusphere-egu23-9922, 2023.

Biotic interactions and community structure are seldom examined in mass extinction studies but must be considered if we are to truly understand extinction and recovery dynamics at the ecosystem scale. Here, we model shallow marine food web structure across a Mesozoic hyperthermal event, the Toarcian extinction, in the Cleveland Basin, UK using a trait-based inferential modelling framework. We subjected our pre-extinction community to extinction cascade simulations in order to identify the nature of extinction selectivity and dynamics. We then tracked the pattern and duration of the recovery of ecosystem structure and function following the extinction event. In agreement with postulated scenarios, we found that primary extinctions targeted towards infaunal and epifaunal benthic guilds reproduced the empirical post-extinction community. These results are consistent with geochemical and lithological evidence of an anoxia/dysoxia kill mechanism for this extinction event. Structural and functional metrics show that the extinction event caused a switch from a diverse, stable community with high levels of functional redundancy to a less diverse, more densely connected, and less stable community of generalists. Ecological recovery appears to have lagged behind the recovery of biodiversity, with most metrics only beginning to return to pre-extinction levels ~7 million years after the extinction event. This protracted pattern supports the theory of delayed benthic ecosystem recovery following mass extinctions even in the face of seemingly recovering taxonomic diversity and gives stark warnings for present day marine ecosystems affected by warming temperatures and dysoxia.

How to cite: Dunhill, A., Shaw, J., Zarzyczny, K., Atkinson, J., Little, C., and Beckerman, A.: Extinction cascades, community collapse, and recovery across a Mesozoic hyperthermal event, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6037, https://doi.org/10.5194/egusphere-egu23-6037, 2023.

Global warming has been implicated as a trigger of mass extinctions in the past. Although species track their thermal niches as isotherms move poleward, systematic changes in the area of habitable space (i.e., their thermal habitat) are expected to influence their extinction risk. Quantifying thermal habitat changes is difficult in the geological past, where information about geography and the distributions of species are highly incomplete. We therefore present a formalized model of thermal habitat change, resulting from the interaction of spherical geometry, thermal niche preference, latitudinal temperature profile, and global temperature change. Our results suggest an overall decrease in available thermal habitat during global warming. Thermal habitat is lost primarily from lower latitude and polar areas, whereas temperate areas are less affected. Although patterns of extinction are ultimately dependent on the geography of available habitat space, the extent to which species occupy their thermal niches, additional abiotic parameters, and biotic interactions, our simple theoretical model provides the basic expectation for spatial patterns of habitat loss, and therefore potentially species loss, during global warming.

How to cite: Kocsis, A. T., Reddin, C. J., Saupe, E. E., and Feulner, G.: A biogeographic model of thermal habitat loss during global temperature change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8192, https://doi.org/10.5194/egusphere-egu23-8192, 2023.

Wetlands and lakes represent the largest natural source of methane to Earth’s atmosphere, where this powerful greenhouse gas influences Earth’s radiative budget. The flux of methane from wetlands and lakes to the atmosphere ultimately depends on the balance between methanogens that produce methane and methanotrophs that consume methane. However, the balance of these biological processes and hence the operation of the terrestrial methane cycle in the geological past are poorly constrained. 

To address this problem, I will present novel biomarker data that record the relative contribution of methanotrophs to the bacterial pool in ancient wetlands and lakes. I will use a unique dataset that consist of >400 samples from across the world and which span most of the Cenozoic, including key hyperthermals like the PETM and ETMs, as well as Toarcian OAE hyperthermal. The aim is to explore the operation of the terrestrial methane cycle during different climate state, including hyperthermals that are characterized by rapid environmental change. 

The data show that the contribution of methanotrophs to the terrestrial bacterial pool has been remarkably stable through time, including across major climatic events like the K/Pg boundary, the Eocene – Oligocene transition, and the mid-Miocene climatic optimum. These results indicate that the terrestrial methane cycle is robust to long-term climatic perturbations and does not operate fundamentally different during greenhouse periods. However, during hyperthermals such as the PETM and the T-OAE, etc, the data indicate a significant perturbation of the terrestrial methane cycle. This means that transient warming events have the potential to destabilize this key biogeochemical cycle, which suggests that the terrestrial methane cycle will be impacted by anthropogenic climate change.

How to cite: Naafs, D.: Intensification of the terrestrial methane cycle during hyperthermal intervals of the Meso- and Cenozoic, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2375, https://doi.org/10.5194/egusphere-egu23-2375, 2023.

The Early Triassic represents a period of prolonged recovery following the most severe extinction of the Phanerozoic. Records show this to be a period of extremely high global temperatures, likely driven by Siberian Traps eruption induced global warming. How this hothouse impacted marine ecosystems and prolonged the recovery process remains uncertain. Across northwestern Pangea, Early Triassic marine sediments are characterized by low organic matter content, despite recurrent anoxia which would create conditions more suitable for preservation, and being located on the western continental margins were the majority of primary productivity in the Panthalassa Ocean would occur. Geochemical proxies suggest the paucity of organic matter reflects a productivity collapse rather than changes in preservation. Nitrogen isotopes show a progressive negative shift starting at the Permian/Triassic extinction and continuing through to the Smithian, indicating progressively growing nutrient limitation. High ocean temperatures likely deepened the thermocline, limiting nutrient recycling and upwelling into the photic zone driving nutrient stress. Finally ocean cooling in the Anisian is marked by widespread deposition of organic rich black shales and return of N isotopes to values consistent with active nutrient upwelling. A hyperthermal driven nutrient-limited Early Triassic ocean was likely a key inhibiter of marine recovery.

How to cite: Grasby, S.: Early Triassic hothouse conditions limited marine productivity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2862, https://doi.org/10.5194/egusphere-egu23-2862, 2023.

The hothouse climate in the Early Triassic has been recognised for a decade. Yet it remains the most recently discovered hothouse and is poorly understood in many aspects. Initially triggered by the Siberian Traps in the latest Permian, the Early Triassic represents one of the most extreme and long-lasting greenhouses in the Phanerozoic. Although the outgassing of the Siberian Traps probably already decreased in the late Griesbachian, the Equatorial SSTs peaked at ~40 ℃ later in the late Smithian. The late Smithian thermal maximum coincided with resumed volcanic activities of a smaller scale. However, why lesser volcanism triggered Phanerozoic’s warmest hyperthermal is puzzling. The extreme warmth ameliorated in the latest Spathians, marking the termination of a ~5 Myr hothouse.

Many key questions about the Early Triassic climate remain unanswered. These include how warm the poles were, how flat the latitudinal SST gradient was, and how climate interacted with the global ocean circulation. However, the most fundamental question is how to maintain such an extreme hothouse climate for such a long time.

As most shelly fossils died out during the end-Permian mass extinction and the Early Triassic oceans were dominated by aragonite-shelled mollusks, reconstruction of Early Triassic seawater temperatures relies almost solely on oxygen isotope thermometer in conodont bioapatite. One of the key challenges is that Early Triassic conodonts are rare, small, and cannot be found everywhere due to the subduction of old ocean floors. These hinder the acquisition of proxy data in a broader palaeogeographic context. Future work combining proxy data with state-of-the-art Earth system modelling would be an ideal solution to better understand the hottest time in the Phanerozoic.

How to cite: Sun, Y.: The Early Triassic hothouse: what we know and what we don’t, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12795, https://doi.org/10.5194/egusphere-egu23-12795, 2023.

The latest Permian mass extinction (LPME) was triggered bymagmatism of the Siberian Traps Large Igneous Province (STLIP), which left an extensive record of sedimentary Hg anomalies at Northern Hemisphere and tropical sites. Here, we present Hg records from terrestrial sites in southern Pangea, nearly antipodal to contemporaneous STLIP activity, providing insights into the global distribution of volcanogenic Hg during this event and its environmental processing. These profiles (two from Karoo Basin, South Africa; two from Sydney Basin, Australia) exhibit significant Hg enrichments within the uppermost Permian extinction interval as well as positive Δ199Hg excursions (to ~0.3‰), providing evidence of long-distance atmospheric transfer of volcanogenic Hg. These results demonstrate the far-reaching effects of the Siberian Traps as well as refine stratigraphic placement of the LPME interval in the Karoo Basin at a temporal resolution of ~105 years based on global isochronism of volcanogenic Hg anomalies.

How to cite: Shen, J.: Mercury evidence  global volcanic effects during the Permian-Triassic transition, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2487, https://doi.org/10.5194/egusphere-egu23-2487, 2023.

Climatic effects on erosion is usually covered up by tectonics and not well understood in active mountains. The Dabie Mountains in central China evolved from a collisional orogen between North China and South China with development of Triassic ultrahigh pressure metamorphic (UHPM) rocks. In the Late Triassic these UHPM rocks experienced a rapid cooling after peak metamorphism and has been linked to compressional uplift during the collisional orogenesis. During this period, the climate changed from arid-semi arid to humid in the northern South China. This climate change is clearly recorded in the Late Triassic successions of upper Puqi and Jigongshan formations in the Huangshi Basin to the south of the Dabie Mountains. Combining tuff zircon U-Pb dating and magneto-stratigraphy, the upper Puqi Formation with arid climate was constrained in the early Norian (~228−221 Ma) with the overlying Jigonghsan Formation with humid climate in the late Rhaetian according to youngest detrital zircon ages. Detrital zircon and rutile U-Pb ages were combined with paleocurrents and sandstone petrography to determine the sedimentary provenance. For the upper Puqi Formation the deposited sediments were likely recycled from the Paleozoic sedimentary rocks in the Dabie Mountains. However, the Jiligang Formation has sediment mainly derived from the middle Neoproterozoic and late Paleoproterozoic basement rocks in the northern South China and Dabie Mountains. This rapid shift in provenance is associated with and plausibly resulted from the Late Triassic climate change, which may force rapid erosion in the southern Dabie Mountains. The deposition of the upper Puqi Formation was temporally overlapping with the rapid cooling and tectonic uplift of the Dabie Mountains, but there were no large changes in sedimentary provenance. This observation suggests low erosion rates in active mountains under a under an arid-semi arid climate.

How to cite: Yang, J., Li, H., Zhou, Y., Liu, A., and Cheng, L.: Climate controlled erosion during the Late Triassic rapid exhumation of the ultrahigh pressure metamorphic rocks in the Dabie Mountains, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7970, https://doi.org/10.5194/egusphere-egu23-7970, 2023.

The largest mass extinction on Earth with an estimated 90% loss of species occurred at the Permian-Triassic Boundary (~252 Ma). The end-Permian mass extinction coincides with extreme temperature increases and changes in ocean circulation and biogeochemistry. These climate perturbations are associated with carbon emissions linked to Siberian Trap volcanism. Fully-coupled Earth System Models can be applied to investigate the feedbacks and sensitivities of the background latest Permian climate to such carbon emissions. Past studies have focussed on constraining the magnitude of these carbon emissions without examining the sensitivity of palaeo-configured Earth System models designed for modern simulations. We modified a version of the Max Planck Earth System Model v1.2, similar to that used in the 6^th-phase of the Coupled Model Intercomparison Project, to simulate the latest Permian climate-carbon system and use geochemical and palaeobiological proxy data to constrain the boundary conditions of the modelled climate state.
We first characterise the latest Permian climate state before presenting first results on a sensitivity study of the latest Permian climate-carbon state to CO₂ emission pulses. A 100 year global mean 2 m surface air temperature of 17.5°C is simulated, rising up to 34.7°C in the low-latitude continental interior. The continental interior is also largely arid from ~50°N to ~50°S with a total precipitation maximum of 11.1 mm day^-1 at the equatorial boundary of the Tethys and Panthalassic Oceans. The prevailing hydrological regime drives woody single-stemmed evergreens and soft-stemmed plant functional groups to dominate in the dynamic vegetation model. The 100 year global mean surface ocean of the latest Permian illustrates a warm-pool across the equatorial boundary between the Tethys and Panthalassic Oceans with a maximum temperature of 30.2°C decreasing to temperatures as low as -1.9°C near the poles. Surface salinities vary broadly across the global oceans with 100 year global mean values ranging from 22.9, in well-flushed regions of strong freshwater flux, to 48.6, in low-latitude regions of restricted exchange. Large-scale seasonal mixing below 60°S in the Panthalassic Ocean dominates the global meridional overturning circulation. These model data fit within the bounds represented by the available proxy data for the Late Permian. The widespread shallow ocean mixed-layer also restricts recirculation of nutrients, driving a high gross primary production with weak seasonality. Furthermore, regions of seasonal deep mixing correlate with seasonal pCO₂ patterns at high latitudes. I will also present further analyses of the simulated ocean biogeochemical cycles in the Hamburg Ocean Carbon Cycle model with a focus on the novel extended Nitrogen-cycle processes.

How to cite: Burt, D. and Ilyina, T.: The sensitivity of the latest Permian climate-carbon state to CO2 emissions in an Earth System Model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13712, https://doi.org/10.5194/egusphere-egu23-13712, 2023.

Following the most severe mass extinction event during the Phanerozoic, the Permian-Triassic mass extinction (PTME, ~251.9 Ma), Early Triassic marine fossil communities were thought to be depauperate, poorly diversified, and dominated by abundant and cosmopolitan disaster or opportunistic taxa. Full re-establishment of complex marine ecosystems was thought to have not occurred until, ~8 million years after the PTME, being represented by the Luoping Biota. The highly suppressed Early Triassic marine ecosystem has been thought to be a consequence of recurrent environmental stresses, including high sea surface temperature, episodes of oceanic acidification, and anoxic/euxinic events mainly occurring during the Permian-Triassic transition, the late Dienerian and late Smithian. Alternatively, it can also result from preservation and sampling biases, which are often neglected in many previous works. Here, we report an exceptionally preserved Early Triassic fossil assemblage, the Guiyang Biota, from the Daye Formation near Guiyang, South China. The Guiyang Biota comprises at least 12 classes and 19 orders, including diverse fish fauna and malacostracans, revealing a trophically-complex marine ecosystem. High-precision U-Pb dating shows that the age of the Guiyang Biota is 250.83 +0.07/-0.06 million years ago. This is only 1.08 ± 0.08 million years after the severe Permian-Triassic mass extinction, and this assemblage therefore represents the oldest known Mesozoic lagerstätte so far. The Guiyang Biota indicates the rapid rise of modern-type marine ecosystems after the Permian-Triassic mass extinction.

How to cite: Dai, X., Davies, J. H. F. L., Brayard, A., and Song, H. and the Guiyang Biota research team: An unexpected fossil lagerstätte under the Early Triassic hyperthermal event showing a modern-type marine ecosystem, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17096, https://doi.org/10.5194/egusphere-egu23-17096, 2023.

Anthropogenic carbon emission rate has exceeded 10 Pg C yr^-1 in 2020 (1), which is likely unprecedented in the last 252 million years. Studying ancient hyperthermal events may help us better understand the natural processes of carbon emission and sequestration, informing policy and decision-making to cope with climate change. Two ancient hyperthermals that occurred at the end of the Permian period and the end of the Paleocene Epoch have been studied extensively, but a key question remains: why is the end-Permian hyperthermal related to the largest mass extinction and a much-delayed recovery, yet the PETM is associated with only extinction of benthic foraminifera and a rapid recovery? I hypothesize that the life extinction and recovery patterns across these two hyperthermals are regulated by the carbon emission and sequestration rates, and the cumulative quantities of CO₂ released. Emission rate is dependent on CO₂ source (e.g., methane hydrate, thermogenic methane, marine or terrestrial organic matter, or volcanic CO₂), and sequestration rate is dependent on the location (marine vs. terrestrial) and processes (silicate weathering vs. organic carbon burial) of carbon sequestration, which are largely uncertain. These uncertainties pose difficulties in unraveling the underlying mechanisms of the different extinction patterns. Here, I quantitatively compare the carbon emission and sequestration rates of the two hyperthermals, which allows for hypothesis regarding carbon sources and sinks to be tested.

How to cite: Cui, Y.: Comparing carbon emission and sequestration during two ancient hyperthermal events: the PETM and the end-Permian mass extinction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2127, https://doi.org/10.5194/egusphere-egu23-2127, 2023.

During the archetypal supergreenhouse Cretaceous Earth, an active cryosphere with permafrost existed in Chinese plateau deserts (astrochonological age ca. 132.49–132.17 Ma). Permafrost wedges have been identified in three different outcrops of the Luohe Fm.  Most of the wedges are concentrated in two discrete horizons bounding three draa successions representing composite-wedge pseudomorphs. A late Pleistocene analogue for the Cretaceous aeolian–permafrost system of the Luohe Fm is provided by the composite wedges and sand wedges within aeolian dune deposits of the Kittigazuit Fm., Hadwen Island, NT, Canada. A modern analogue for these Cretaceous plateau cryospheric conditions is the aeolian–permafrost system we report from the Qiongkuai Lebashi Lake area, Xinjiang Uygur Autonomous Region, China. Significantly, Cretaceous plateau permafrost was coeval with marine cryospheric indicators in the Arctic and Australia, indicating a strong coupling of the ocean–atmosphere system. The Cretaceous permafrost contained a rich microbiome at subtropical palaeolatitude and 3–4 km palaeoaltitude, analogous to recent permafrost in the western Himalayas. Global permafrost thaw during the Cretaceous released significant volumes of greenhouse gases to the atmosphere as well as dissolved organic carbon (DOC) and other nutrients into watersheds, and marine waters affecting aquatic systems through carbon and nutrient additions. The contribution of permafrost thaw to the Cretaceous global C balance, including during oceanic anoxic events (OAE) will have to be determined in future research dealing with ocean–continental cryosphere coupling associated with events of cryosphere degradation in the aftermaths of supergreenhouse cold snaps. A mindset of persistent ice-free greenhouse conditions during the Cretaceous has stifled consideration of permafrost thaw as a contributor of C and nutrients to the palaeo-oceans and palaeo-atmosphere.

How to cite: Rodríguez López, D. J. P., Wu, C., Vishnivetskaya, T. A., Murton, J. B., Tang, W., and Ma, C.: Permafrost in the Cretaceous supergreenhouse, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17503, https://doi.org/10.5194/egusphere-egu23-17503, 2023.

The Paleocene–Eocene Thermal Maximum (PETM, ~56 Ma) is a large negative carbon isotope excursion that testifies to a massive perturbation of the global carbon cycle and has been considered to be the best deep-time analogue for present and future climate change. However, most studies of the response of shallow-water carbonates to climate change during PETM have focused on individual sites and sections. To get a broader perspective we compiled published records of carbonate-platform environments across the Paleocene-Eocene transition in Tethys ocean. The shallow-marine benthic ecosystems during PETM were largely distinct in composition from those in the latest Paleocene or/and early Eocene. No obvious impact on biota and specifically on larger benthic foraminifera is observed at PETM onset, whereas the major biotic change occurs later on at PETM recovery, suggesting that biotic changes lag behind climate warming and carbon cycle perturbations in shallow-water ecosystem. We also inferred sedimentary responses at each site from direct or indirect indicators of sedimentological and relative sea-level change at the PETM. A transgressive trend that began at PETM onset, and continued through the CIE core, followed by a relative sea-level fall around the PETM recovery, implying the response of the relative sea-level to climate warming is characterized by a gradual rise, and a rapid fall. The demise of carbonate platform, increased terrestrial inputs and tropical storms has been widely observed in carbonate-platform environments across the PETM, suggesting enhanced erosion/chemical weathering and hydrological changes during the climate warming.

How to cite: Hu, X., Li, J., Jiang, J., Garzanti, E., and BouDagher-Fadel, M.: Carbonate-platform changes response to the Paleocene-Eocene Thermal maximum, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6337, https://doi.org/10.5194/egusphere-egu23-6337, 2023.

Marine assemblages are expected to undergo substantial reorganization under anthropogenic climate change but some species may be better situated to track their preferred conditions. Assemblage vulnerability can thus be indicated by the thermal niches of its component species. However, the link between this vulnerability and extinction risk of its species is unclear and cannot yet be tested with modern species since widespread climate-driven extinctions are not yet manifest. To address this gap, we inferred fossil species’ thermal niches based on observed distributions on paleoclimate maps over the hyperthermal pulses of the Late Pliensbachian to Early Toarcian. We tested whether species extirpated from fossil invertebrate assemblages after warming, alongside those species that went extinct, were most likely from the pool of species that could not maintain upper thermal safety margins, in contrast to assemblage immigrants. The fossil record has the potential to reveal unique information about natural system responses to climate change. We discuss how much can it tell us about marine ectotherm vulnerability to extinction under climate change.

How to cite: Reddin, C., Landwehrs, J., Mathes, G., Saupe, E., Ullmann, C., Feulner, G., and Aberhan, M.: Thermal niche determines marine assemblage change during Early Jurassic warming pulses, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1631, https://doi.org/10.5194/egusphere-egu23-1631, 2023.

The Toarcian Oceanic Anoxic Event (T-OAE, ~183 Ma) was a profound short-term environmental perturbation associated with the large-scale release of ¹³C-depleted carbon into the global ocean-atmosphere system, which resulted in a significant negative carbon-isotope excursion (CIE). The general lack of characteristic T-OAE records outside of the northern hemisphere means that the precise environmental effects and significance of this event are uncertain. Many biotic carbonate platforms of northern hemisphere from the western Tethys drowned or shifted to comparatively unfossiliferous oolitic platforms during the early Toarcian. However, southern hemisphere records of Toarcian carbonate platforms are rare, and thus the extent and significance of biotic platform demise during the T-OAE is unclear. Here we present high-resolution biostratigraphical, sedimentological, and geochemical data across two Pliensbachian–Toarcian shallow-water carbonate-platform sections exposed in the Tethys Himalaya. These sections were located paleogeographically on the open southeastern tropical Tethyan margin in the southern hemisphere. The T-OAE in the Tethys Himalaya is marked by a negative CIE in organic matter. Our sedimentological analysis of the two sections reveals an abundance of storm deposits within the T-OAE interval, which emphasizes a close link between warming and tropical storms during the T-OAE, in line with evidence recently provided from western Tethyan sections of the northern hemisphere. In addition, our analysis also reveals extensive biotic carbonate-platform crisis by drowning or changing to unfossiliferous carbonates coincident with the onset of the CIE where the proxies of continental weathering (e.g. Ti, Sc, Th) and redox (e.g. Mn, Ce and Ce) show obviously increase. Taken together, the drastically enhanced terrigenous flux and deoxygenation likely played a pivotal role in the more severe crisis for benthic carbonate producers during the negative phase of the CIE.

How to cite: Han, Z.: Carbonate-platform response to the Toarcian Oceanic Anoxic Event in the Tethys Himalaya, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4571, https://doi.org/10.5194/egusphere-egu23-4571, 2023.

Abrupt changes in seawater temperature during the late Pliensbachian and early Toarcian significantly influenced not only species and functional diversity of marine benthic ecosystems, but also affected body size at intraspecific and community levels. Although community-level trends in body size driven by selectivity in species extinctions are well-documented, intraspecific trends in size and life-history strategies remain poorly explored. Harpax spinosus is an Early Jurassic plicatulid, bimineralic bivalve that was abundant during the Pliensbachian but went extinct at the onset of the Toarcian oceanic anoxic event. Here, we evaluate temporal changes in size-frequency distributions of this species at high stratigraphic resolution at Peniche and Fonte Coberta sections in the Lusitanian Basin. Analyses of H. spinosus at these sections document that this bivalve typically achieved 10-15 mm in length during the deposition of the margaritatus and spinatum zones, with left-skewed or bimodal size distributions. However, its median size significantly declines to < 10 mm within the spinatum Zone (in the upper part of the apyrenum Subzone), coinciding with the appearance of small koninckinid brachiopods. This size reduction is followed by a return to larger sizes in the upper part of the spinatum Zone. A second decline in size occurs in the lowermost Toarcian where Harpax co-occurs with small-sized Koninckella-Nannirhynchia assemblage (Koninckella fauna), immediately above the mirabile Subzone. Although this abrupt decline in size can be accentuated by condensation, the size distribution at bedding plane is strongly left-skewed (with infrequent small-sized individuals), in contrast to the size distribution in the overlying marl. Harpax assemblages in the lowermost Toarcian semicelatum Subzone are characterized by right-skewed or symmetric size-frequency distributions, with median size < 10 mm. Sclerochronological analyses of growth rings and stable isotopes indicate that the decline in size was not associated with any decline in lifespan and was rather associated with a decline in the von Bertalanffy growth coefficient.

How to cite: Tomašových, A., Duarte, L. V., Müller, T., and Schlögl, J.: Intraspecific decline in shell size of the bivalve Harpax spinosus across the Pliensbachian/Toarcian transition, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9692, https://doi.org/10.5194/egusphere-egu23-9692, 2023.

Cadmium (Cd) displays nutrient-type patterns in the modern ocean and has potential as a tracer of the efficiency of the ‘biological pump’ and its ability to transport CO₂ from the atmosphere to the deep ocean during intervals of extreme environmental change. This potential arises because phytoplankton preferentially incorporate lighter Cd isotopes under many oceanic conditions, leaving surface waters relatively enriched in heavier isotopes. As a consequence of this fractionation, Cd-isotope ratios have been shown to reflect nutrient availability and the intensity of primary productivity in the modern ocean. However, the ability of the Cd stable-isotope system to serve as a robust palaeo-productivity tracer is not yet well established.

Oceanic Anoxic Event 2 (OAE 2; ~94 Ma) represents a period of widespread environmental degradation and oceanic de-oxygenation, likely the result of increased volcanic activity, intensified marine and continental silicate weathering, augmented nutrient input to the ocean and elevated primary productivity. However, direct evidence for the availability of bio-limiting nutrients in the oceans and the role of primary productivity as a feedback mechanism to eventually re-stabilise climate is limited. Here we present the first Cd-isotope record for OAE 2, from the well-preserved and biostratigraphically well-constrained organic-lean pelagic carbonate section through the English Chalk at Eastbourne (UK). Contrary to expectations, Cd isotopes at Eastbourne do not seem to be controlled by surface ocean productivity, but likely reflect global sub-surface signatures. The isotopic record suggests an active biological pump during OAE 2 coupled with changes in ocean circulation on a global scale. Our new record proposes that the Cd-isotope proxy is powerful and potentially very important for unravelling environmental changes during deep time events.

How to cite: Gangl, S., Stirling, C., Druce, M., Clarkson, M., and Jenkyns, H.: Cd isotopes in carbonates deposited during ‘OAE 2’: Assessment of a novel palaeo-productivity tracer, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15648, https://doi.org/10.5194/egusphere-egu23-15648, 2023.

Providing empirical evidence about the response of tropical shallow-water organisms to past warming and hyperthermal events is particularly important considering that they are severely threatened by current global warming. Stratigraphic resolution in shallow-water sections cannot be as precise as in pelagic environments and the empirical evidence is usually limited to a “before-and-after” comparison to assess the biological effects of events.

During the early Paleogene, the Neothetyan circum-Mediterranean region was the global center of reef coral diversity. Our compilation of Paleocene to Eocene reef coral occurrences allows for an analysis of reef coral responses to the major climatic changes of this time interval in unprecedented temporal detail, including the Paleocene-Eocene Thermal Maximum (PETM), when global mean temperatures reached more than 5°C above pre-industrial levels.

Reef corals were negatively affected by the PETM as we document a small decrease in diversity at both species and genus level and an increase of extinction rate across the hyperthermal event. During the onset of the Early Eocene Climate Optimum (EECO), diversity gradually increased as also documented by a peak of origination rate. The EECO diversity high is mainly related to the rich coral fauna recently described from NE Italy where the EECO and post-EECO phases are characterized by an accurate specimen-based systematic revision of museum collections associated to a detailed biostratigraphic calibration.

The Late Eocene cooling was accompanied by an increase in diversity, with the origination of several Oligocene coral taxa and the extinction of Eocene ones. The Late Eocene is also the time when coral reefs started to flourish again after the crisis of Late Paleocene-Early Eocene.

^{This study was funded by the Italian Ministry of Education and Research (MIUR), funds PRIN 2017: project “Biota resilience to global change: biomineralization of planktic and benthic calcifiers in the past, present and future” (prot. 2017RX9XXY).}

How to cite: Bosellini, F., Benedetti, A., and Kiessling, W.: The Neothetyan circum-Mediterannean record as a suitable archive to understand the response of reef corals to the warming events of the Early Paleogene, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6441, https://doi.org/10.5194/egusphere-egu23-6441, 2023.

The Paleocene encompasses a series of hyperthamls including the Paleocene–Eocene Thermal Maximum (PETM) and the ETM2 which represent severe disturbances of global carbon cycling and the Earth system. Responses of marine organisms included extinction, migration and evolutionary turnover, but the role of ocean acidification on deep-sea foraminiferal calcification has not yet been quantified. Using computed tomography (CT) we investigate morphological (surface area, test volume, calcite volume, chamber number) and hence calcification response in two benthic foraminiferal species, at central Pacific Site 1210 (PaleoDepth 2100m), and Southern Ocean Maud Rise Site 690 (PD 1900m), Walvis Ridge Site 1264,  and Kerguelen Plateau Site 1135 (PD ~800m) for the PETM and ETM2.

The relative warming during the event was the same at all sites, suggesting that biotic differences are not likely related to differential warming. The environmental change led to reduction of test volume of both species, negatively impacting their potential ability to generate gametes. Epifaunal Nuttallides truempyi increased its surface area relative to volume in the Southern Ocean, potentially increasing its ability to forage and take up oxygen. In contrast, there is no clear pattern of change in shallow infaunal Oridorsalis umbonatus which, given sufficient food, can thrive at lower oxygen conditions. Calcite volume/test volume ratio decreased in both species during the PETM in the Southern Ocean, with the lack of response at upper abyssal depth in the Pacific possibly driven by severe oligotrophy even before the excursion. Therefore, changes in food supply during hyperthermals might have been less pronounced at upper abyssal depths in the Pacific than at the other two sites. These results contrast with published results from Walvis Ridge which showed an increase in calcification in small specimens of O. umbonatus. Food availability at the Southern Ocean sites may have supported growth as indicated by test volumes, but did not supply enough energy for calcification to mitigate against lower carbonate ion saturation during the PETM CIE.

How to cite: Schmidt, D. N., Adebowale, M., Thomas, E., Ridgewell, A., and Cotton, L.: Life in a dark environment – what was the physiological and calcification response of benthic foraminifera to the environmental changes of the Paleogene hyperthermals, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7633, https://doi.org/10.5194/egusphere-egu23-7633, 2023.