As an inherently multi-disciplinary subject, we aspire to better understand the complex coupling of biogeochemical cycles and life, the links between mass extinctions and their causal geological events, how fossil records shed light on ecosystem drivers over deep time, and how tectono-geomorphic processes impact biodiversity patterns at global or local scales. We further encourage submissions that use new approaches to unravel the interplay between paleogeography, paleoclimate, and biological evolution across Earth’s history. We aim to understand our planet and its biosphere and climate through both observation- and modelling-based studies.
Orals: Thu, 7 May, 10:45–15:40 | Room N1
Accurately distinguishing between biotic and abiotic microstructures is crucial for understanding the evolution of early life and the search for extraterrestrial life. The oldest putative fossils reported occur in the form of hematite filaments and tubes in the jasper-carbonate BIF from the Nuvvuagittuq Supracrustal Belt (NSB), Québec, possibly as old as 4.3 Ga. Although these twisted and branched hematite filaments and tubes are very similar to the Fe-oxyhydroxide filaments produced by Fe-oxidizing bacteria in modern hydrothermal deposits, they are still being questioned because morphologically and compositionally similar abiotic filamentous biomorphs can be produced in “chemical gardens”. Additionally, the origin of ubiquitous circularly concentric rosettes that occur with the filaments and tubes remains unclear. Systematic mineralogical and morphological characterization of these microstructures using a variety of correlated in-situ micro-analytical techniques such as polarizing microscopy, Raman spectroscopy, SEM-EDS, and XPS now yield a new understanding of these ancient microscopic objects.
Firstly, new observations of hematite filaments and tubes preserved in apatite crystals indicate phosphatization as another taphonomic mode of preservation. These apatites with filaments that are several hundred micrometers in size, and usually distributed in discontinuous bands between the silicon-rich and iron-rich microbands. The diameter of these hematite filaments and tubes is 4 to 8 μm, while their lengths are 10 to 200 μm. They are thinner than those previously reported preserved in quartz and their diameter is closer to that of modern iron-oxidizing bacteria. As for co-occurring hematite tubes, their interior is usually filled with apatite. The walls of tubes are often straight, and even crossing crystal boundaries between apatite and microcrystalline quartz. Furthermore, new Raman spectra show the occasional presence of organic matter in these filaments preserved in apatite, independently supporting a biological origin.
Secondly, rosettes widely present in the quartz have circularly concentric layers, radially geometric crystals of acicular hematite, and circular double or triple twins. These microstructures are akin to patterns seen in botryoidal minerals and likely produced by abiotic chemically oscillating reactions (COR). In addition, the walls of the tubes preserved in quartz are also sometimes wavy, curved, or botryoidal-like, along with concentric layers, which is comparable to botryoidal coatings on modern hollow filaments of ferrihydrite in deep-sea hydrothermal ecosystems, indicating the interaction between iron-containing minerals and decaying organic matter from biomass during diagenesis.
The latest observations suggest that in the early Earth's submarine hydrothermal environments rich in phosphate and organic acids, the widespread phosphatisation enables the oldest life preserved in the apatite in the form of hematite filaments and tubes. The new observations also emphasize the potential role of abiotic COR in the formation of rosettes, as well as the modifications of the surface features of microfossils during diagenesis. These biological and abiotic “biosignatures” provide a valuable reference to search for life signals in extraterrestrial environments such as Mars and icy moons.
How to cite: Ge, Y., Papineau, D., Guo, Z., She, Z., O'Neil, J., and Garçon, M.: Widespread chemically oscillating reactions and the phosphatization of hematite filaments and tubes in the oldest BIF from the Nuvvuagittuq Supracrustal Belt , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1919, https://doi.org/10.5194/egusphere-egu26-1919, 2026.
Large Igneous Province (LIP) volcanism is commonly considered to have driven ocean deoxygenation and associated mass extinctions during the Phanerozoic. However, the impacts and feedback mechanisms associated with LIP emplacement in the prevailingly low-oxygen Precambrian environment remain poorly understood. Here, we present mercury isotope, iron speciation and phosphorus phase partitioning data for mid-Mesoproterozoic marine sediments of the Shennongjia Group, South China, to reconstruct the response of the phosphorus cycle to LIP volcanism. Our data indicate that LIP volcanism triggered an expansion in marine euxinia, which enhanced phosphorus recycling and stimulated surface ocean primary production, thereby promoting increased burial of organic carbon and pyrite. This facilitated net marine oxygenation, with repeated volcanic pulses ultimately resulting in enhanced ventilation of the mid-Proterozoic ocean. We propose that while mid-Proterozoic LIP volcanism may have caused short-term ecological crises, the ensuing redox-nutrient feedbacks ultimately stimulated progressive oxygenation of Earth’s surface environment.
How to cite: Sun, L., Sonke, J. E., Poulton, S. W., Tang*, D., Shi, X., Wang, X., Zhou, X., Meng, L., Xie, B., Xu, L., Yang, S., and Guilbaud, R.: Volcanic forcing of oxygenation dynamics in the mid-Proterozoic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1434, https://doi.org/10.5194/egusphere-egu26-1434, 2026.
The shift from the climate of the “boring billion” without evidence for major glaciations to the globally ice-covered “Snowball Earth” events of the Cryogenian (720–635 million years ago, Ma) remains enigmatic. Various factors have been suggested to drive the cooling in the early Neoproterozoic (1000–539 Ma), most prominently decreasing carbon-dioxide levels due to enhanced weathering of tropical continents or fresh volcanic material. However, these processes should have operated during the boring billion as well, triggering the quest for alternative explanations. It has been suggested, for example, that the increase in both the diversity and the biomass of eukaryotic algae around 800 Ma could have contributed to the cooling via the emission of dimethyl sulfide (DMS), a source of cloud condensation nuclei instrumental in forming bright clouds over dark ocean surfaces. Here, we investigate this hypothesis with a coupled climate–ocean biogeochemistry model, allowing for the first time the quantification of the relevant marine carbon cycle feedbacks. We confirm that the increase in cloud condensation nuclei cools the Neoproterozoic climate and can lead to global glaciation at low atmospheric carbon-dioxide concentrations. Our analysis sheds light on the positive and negative feedback loops associated with the rise of algae and demonstrates that changes in cloud cover remain a plausible contribution to Neoproterozoic cooling.
How to cite: Feulner, G., Hofmann, M., Eberhard, J., and Petri, S.: Ocean biogeochemistry amplifies cooling caused by increase in cloud condensation nuclei from algae prior to Cryogenian Snowball Earth events, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6828, https://doi.org/10.5194/egusphere-egu26-6828, 2026.
The degree to which Earth’s climate retained seasonality and ocean-atmospheric coupling during the two Cryogenian snowball Earth glaciations, the Sturtian (~717-658 Ma) and Marinoan (~654-635 Ma), is unknown. The classic hypothesis envisions ice at equatorial latitudes with a largely quiescent hydrological cycle. However, other observations imply the persistence of open water in the tropics, permitting ocean-atmospheric coupling and reconciling photosynthetic survival with low-latitude glacial activity. Consequently, open questions remain as to whether internal climate cycles could operate during snowball Earth, and if so, what their expression reveals about the extent of open ocean and the dynamics of the Cryogenian climate system; important climate questions that carry key biological implications. Varve-like laminites provide high resolution records of climatic variability as far back as the Proterozoic. However, varved sediments that retain climatic information are rare in the Cryogenian. Here, we analyse field data from rhythmic laminites from the Port Askaig Formation (Scotland). Petrographic and spectral analysis indicates that the laminites represent glacio-lacustrine annual varves, which reveal statistically significant centennial to interannual periodicities strongly similar to solar phenomena and modern ocean-atmospheric climate patterns. We interpret these signals with fully coupled Cryogenian climate simulations using the Community Earth System Model (CESM) under varying degrees of ice coverage to reconstruct climate variability during this interval of the Sturtian glaciation. These simulations suggest that open water is present to some degree in the tropics. Our study reveals a wider range of climatic variability than previously envisaged under snowball Earth conditions, and hints at the possibility of unfrozen tropical waters during this discrete interval of the Sturtian glaciation, or yet unexplored mechanisms of interannual variability on icy worlds.
How to cite: Griffin, C., Gernon, T., Fu, M., Rugen, E., Spencer, A., Warrington, G., and Hincks, T.: Distinguishing Snowball Earth climate modes using field data and climate simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6597, https://doi.org/10.5194/egusphere-egu26-6597, 2026.
The Ediacaran-Cambrian Transition (approx. 550-539 mya) was one of the planet’s most revolutionary events, marking the emergence of diverse and abundant animals. Changing environmental conditions – such as oxygen availability, carbon cycling and nutrient levels – are likely to have been both constricting and galvanising, resulting in the rapid radiation of diverse body plans alongside a permanently altered ocean-atmosphere system. For my PhD research, as part of the UK’s first Doctoral Training Programme in Extinction Studies, I took a biocultural approach, seeking to acknowledge both the catastrophic and creative aspects of ecological regime shifts, whilst offering an artistic response to the complex processes that occur at key chronostratigraphic boundaries, from mass extinctions and evolutionary radiations to global oxidation events. Combining palaeontological study and creative practice, I established a novel methodology conducting ‘lyric fieldwork’ at Global Stratotypes and Section Points, writing a radically ‘indisciplined’ thesis and accompanying long poem spanning deep time, from the Precambrian through to the Phanerozoic. In this presentation – a performative reading – I will share an excerpt of my poem, focusing on the closing moments of the Proterozoic Eon and the start of the Phanerozoic Era, where the Ediacaran Period moves into the Cambrian Period, and where major geochemical perturbations correspond with an ‘explosion’ of biological innovations, from biomineralisation and the evolution of hard body parts to the rise of predator-prey dynamics and increased locomotive strategies.
How to cite: Simpson, K.: Ending the Proterozoic: A Poetic Reimagining , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10751, https://doi.org/10.5194/egusphere-egu26-10751, 2026.
The evolution of plant diversity through Phanerozoic time is often understood as a succession of dominating evolutionary floras. Following the onset of land plant expansion and diversification in the Silurian to Middle Devonian, these include the successive dominance of plant ecosystems by spore-bearing plants (Paleophytic flora), gymnosperms (Mesophytic flora), and angiosperms (Cenophytic flora). The succession of these floras is associated with major evolutionary innovations in plant growth forms, physiology and reproductive systems, allowing for new strategies to utilize resources and diversify. In concert with biological innovation, environmental conditions over the Phanerozoic have strongly varied due to plate tectonic rearrangements of continents and topography, together with variation in atmospheric CO2 and climate. However, our understanding of how biological innovation and environmental changes interacted to shape the diversity of land plants through deep time is limited by a fragmentary geologic record of both plant diversity and environmental conditions.
Here, we reconstruct high-resolution climatologies (0.5° in longitude and latitude) over the last 470 million years using the fully coupled atmosphere-ocean general circulation model HadCM3 [1], the landscape evolution model goSPL [2], and the mechanistic climate downscaling algorithm CHELSA [3]. Applying the trait-based plant diversity model TREED [4] we then investigate how paleogeographic changes, variation in atmospheric CO2, and climate conditions shaped the Phanerozoic plant diversification. Combining the model-based diversity reconstruction with an analysis of 140,000 plant fossil occurrences from the Paleobiology Database, we show that Phanerozoic plant genus originations were strongly associated with variation in atmospheric CO2 and the tectonic supercontinent cycle, both limiting terrestrial resource and niche availability, and modulating the efficiency of environmental heterogeneity to generate diversity. We further show that the angiosperm terrestrial revolution is unique not only due to the intrinsic diversification potential of flowering plants, but also because of the exceptional environmental opportunities following the Pangea supercontinent breakup.
[1] P. J. Valdes, et al., The BRIDGE HadCM3 family of climate models: HadCM3@Bristol v1.0. Geoscientific Model Development 10 (10), 3715–3743 (2017), doi:10.5194/gmd-10-3715-2017, https://gmd.copernicus.org/articles/10/3715/2017/
[2] T. Salles, et al., Landscape dynamics and the Phanerozoic diversification of the biosphere. Nature 624 (7990), 115–121 (2023), doi: 10.1038/s41586-023-06777-z, https://www.nature.com/articles/s41586-023-06777-z
[3] D. N. Karger, et al., Climatologies at high resolution for the earth’s land surface areas. Scientific Data 4 (1), 170122 (2017), doi:10.1038/sdata.2017.122, https://www.nature.com/articles/sdata2017122
[4] J. Rogger, et al., TREED (v1.0): a trait- and optimality-based eco-evolutionary vegetation model for the deep past and the present (2025), doi:10.5194/egusphere-2025-6002, https://egusphere.copernicus.org/preprints/2025/egusphere-2025-6002/
How to cite: Rogger, J., Allen, B., Donoghue, P., Karger, D., Salles, T., Skeels, A., and Lunt, D.: Timing and magnitude of Phanerozoic plant diversification are linked to paleogeography and atmospheric CO2, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7891, https://doi.org/10.5194/egusphere-egu26-7891, 2026.
Metazoan reefs have experienced repeated crises throughout the Phanerozoic, marked by geologically rapid declines in reef carbonate production. While some of these crises coincided with major biotic turnovers, others left reef-building communities largely intact, and no simple relationship exists between crisis magnitude and ecological change. Consequently, the extent to which reef crises reshaped reef community composition and whether they triggered cascading extinctions among reef-dependent organisms remains unresolved.
Here, we use a global compilation of reef-related fossil occurrences over the Phanerozoic to test whether reef crises affected not only reef builders but also the wider marine biota. We distinguish three cohorts of reef affinity: (i) metazoan reef builders (i.e. colonial corals and sponges), (ii) reef dwellers, and (iii) non-reef organisms. By integrating these data with stage-level changes in reef volume, we evaluate extinction dynamics across four major Phanerozoic reef crises.
We find that reef builders and reef dwellers were tightly coupled over the last 500 million years. Although their background extinction patterns do not indicate simple, one-to-one cascading extinctions, extinction rates in both groups increased significantly during intervals of major reef loss. In contrast, non-reef organisms show no comparable response to reef crises. Our findings highlight the fundamental ecological interdependence between reef-building organisms and the diverse communities they support, and they underscore that the collapse of reef frameworks likely entails the loss of far more biodiversity than reef-building organisms alone.
How to cite: Dimitrijevic, D. and Kiessling, W.: Reef crises as an Earth-system driver of marine biodiversity loss, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19221, https://doi.org/10.5194/egusphere-egu26-19221, 2026.
The Great Ordovician Biodiversification Event (GOBE) marks one of the most profound radiations of marine life in Earth history. Numerous hypotheses have been proposed for the drivers of the increase in richness during this interval. Distinguishing among these factors requires biodiversity to be evaluated at both local and regional scales across different environments. Here, we compiled a high-resolution, assemblage-level dataset comprising 557 stratigraphic sections and 12,898 fossil occurrences from South China. We integrated these records using a quantitative stratigraphic approach, to examine changes in local (assemblage-level) and regional marine species richness from the Furongian (late Cambrian) to the Middle Ordovician across four depositional environments: littoral, platform, slope, and deep-shelf. We additionally assessed faunal differences across environments and geographic space. Our results suggest regional richness increased four-fold during the GOBE, closely paralleling the spatial expansion of fossil-bearing environments, especially the platform and slope. In contrast, local (assemblage-level) richness remained relatively stable and low through the study interval, despite fluctuations within the slope environment. The taxonomic composition of the platform and slope environments diverged during the GOBE, and spatial turnover increased from the early to late stages of the GOBE. Our findings suggest the expansion of shallow-marine environments tied to increasing sea levels may have been one of the primary drivers of the Ordovician marine biodiversification in South China, with increased faunal differentiation across both environment and space.
How to cite: Huang, H., Chu, T., Deng, Y., Zhang, L., Fan, J., and Saupe, E. E.: Local diversity remained relatively stable across the Great Ordovician Biodiversification Event (GOBE) in South China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15332, https://doi.org/10.5194/egusphere-egu26-15332, 2026.
Organisms whose activities impact the availability of resources in their environments, known as ecosystem engineers, are known to have profound controls on ecological and evolutionary dynamics throughout Earth history. Bioturbators – animals that mix seafloor sediments – are especially powerful ecosystem engineers due to their direct impacts on key benthic biogeochemical cycles. The emergence or loss of bioturbators throughout Earth history is associated with unique and profound shifts in benthic ecology and biogeochemistry. The end-Permian mass extinction (EPME), regarded as the most devastating climate-driven mass extinction in Earth history, saw devastating losses in marine benthic biodiversity and bioturbators, with the bioturbation-driven sedimentary mixed layer completely collapsing in some regions. The loss of bioturbating ecosystem engineers during the EPME has long been implicated in the rates of benthic recovery in the Early Triassic, although the precise impacts of bioturbator responses have remain unconstrained. Here, we test the hypothesis that loss of bioturbating ecosystem engineers during the EPME led to unique ecological and biogeochemical consequences in Early Triassic communities. Combining trace fossil data from literature and body fossil data from the Paleobiology Database for continuous stratigraphic sections across the EPME, we construct multiple comparative local time series of ecological responses of bioturbators and local benthic communities. We use the Earth system model cGENIE to reconstruct marine environmental conditions across the EPME, which also serve as boundary conditions for local biogeochemical models. For each region represented by continuous stratigraphic sections, we then use the fossil record to parameterise pre-EPME and post-EPME bioturbation in biogeochemical reactive-transport models and compare the impacts of the complete loss, reduction, or persistence of bioturbation on benthic biogeochemistry. Finally, we run local sensitivity analyses to constrain the impacts of bioturbation responses on biogeochemical change, and effect size analyses to quantify the relative roles of bioturbators and climate change on ecological responses across the EPME. These results address long-standing assumptions about the role of bioturbation in benthic ecosystem recovery through the Early Triassic and underscore the importance of local environments and community ecology for contextualising recovery in the aftermath of mass extinctions.
How to cite: Cribb, A., Sartin, A., Allen, B., Stokey, R., Monarrez, P., and Hulse, D.: Ecological and biogeochemical consequences of benthic ecosystem engineer responses to the end-Permian mass extinction , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22916, https://doi.org/10.5194/egusphere-egu26-22916, 2026.
Plate tectonic reconstructions are different from palæogeographic reconstructions. The latter can be derived from the former, but not the opposite.
Many end-users (palæontologists, palæoclimate or mantle dynamics modellers) use a map (often without citing the source) of the palæogeography for a given time. However, there are various reconstructions of palæogeographies, based upon numerous plate tectonic models.
Aimed primarily at end-users, the presentation will focus on what are the main similarities and differences when creating a plate tectonic model. Then, different ways (mainly two) of proposing palæogeographies will also be discussed.
This information is crucial when using such maps and can have a significant impact on interpretations drawn from climate simulations or studies of the evolution of life through Earth history.
How to cite: Vérard, C. and Franziskakis, F.: The different approaches for reconstructing palæogeography at the global scale in deep time, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7347, https://doi.org/10.5194/egusphere-egu26-7347, 2026.
Paleogeography is a key boundary condition for reconstructing Earth’s climatic evolution and habitability. On geological timescales, paleogeographic changes control the latitudinal positioning of environments, governing received and reflected solar radiation and climatic zonation. The distribution and morphology of continents and oceans further control ocean–atmosphere circulation and influence the evolution and dispersal of marine and terrestrial biota.
Here we present a new effort to construct a continuous (1 Myr resolution) global paleogeographic digital elevation model for the entire Phanerozoic (540–0 Ma). The reconstructions integrate new and previously published plate models, and global and regional paleo-elevation datasets. Building on and extending methodologies previously applied to the Cenozoic (66–0 Ma), our approach incorporates dynamic topography from mantle circulation (100–0 Ma), oceanic lithospheric ages, sediment thickness, detailed continental margin evolution, parameterized subduction zones, and spatiotemporal interpolation between topographic datasets of different time intervals. The reconstructions focus in detail on key paleogeographic features relevant for ocean circulation, climate, and biogeography, including oceanic gateways, land bridges, and large-scale orogenies.
Finally, we present results from a variety of fully coupled Earth system model experiments, mainly with Cenozoic paleogeographic boundary conditions (e.g., present, Eocene–Oligocene, Late Eocene, and the DeepMIP Early Eocene ensemble), to demonstrate how paleogeographic changes influences planetary energy budgets, ocean circulation, and climate sensitivity. These results highlight systematic relationships that offer potential for extrapolation throughout the Phanerozoic.
How to cite: Straume, E., Torsvik, T., Domeier, M., and Nummelin, A.: Phanerozoic paleogeography and its impact on long-term climatic change and habitability, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13853, https://doi.org/10.5194/egusphere-egu26-13853, 2026.
The concept of a warm, sluggish ocean recurs in the palaeoceanographic literature, yet over the last few years, both observation and model studies have challenged this concept repeatedly. Nevertheless, observations in the modern do link the ongoing anthropogenic warming to the slowing down of oceanic circulation. This mismatch between the different scales of observations presents a critical problem to our understanding of the past ocean. Here, we present a critical evaluation of this concept through an extensive series of intermediate complexity Earth system model experiments. Multiple paleogeographic scenarios across the Phanerozoic, CO2 concentration, and orbital configuration have been simulated to evaluate the relations between planetary surface temperatures and deep-water rejuvenation rate. Combined, the results of these simulations present a very limited contribution of warm climates to the global ocean circulation slowdown. For most experiments, warmer conditions enhanced overall oceanic turnover due to an increase in vertical density gradient, supporting more efficient downwelling. However, this state is only achieved in the long term, with some slowdown after the initial warming. The overall range of turnover time, even during the slowest period of deep-water rejuvenation, remains within the same order of magnitude as the modern. In light of these findings, it is unlikely that at any point through the Phanerozoic did oceanic turnover rate changed in a magnitude that would impact the mixing state of most marine dissolved chemical elements, at least at current flux state.
How to cite: Bialik, O. M., Sarr, A.-C., Donnadieu, Y., and Pohl, A.: Phanerozoic trends in deep water rejuvenation: Is there a relation between global temperature and ocean mixing? , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2111, https://doi.org/10.5194/egusphere-egu26-2111, 2026.
Over geological timescales climate is regulated by the long carbon cycle, in which a balance is struck between CO2 degassing from the solid Earth and CO2 consumption by continental silicate weathering stabilizing atmospheric CO2 levels and maintain habitable conditions. Geodynamic processes regulate both CO2 degassing rates as well as the distribution and elevation of continents, thereby controlling continental weatherability and, ultimately, atmospheric CO2 and long-term climate.
However, long-term carbon cycle models are often limited by their definition of degassing independently of geodynamics evolution and their inevitable attribution of continental weatherability as the primary driver of long-term climate. Furthermore, the sparsity of the geological record means that models often rely on observations of present-day Earth to simulate past Earth states. All these constrains provide limited insight into how geodynamics interacts with climate, and surface processes to regulate atmospheric CO2 over geological timescales.
To address these limitations, we use fully integrated "digital siblings” of the Earth: 3D fully virtual planets designed to simulate internally consistent evolution of habitable planets over a several 100~Myr timescales, not necessarily aiming to replicate Earth. We integrate three numerical models in a dynamically interdependent framework: the geodynamic model StagYY (Coltice et al., 2019), the climate model PLASIM-GENIE (Holden et al., 2016), and the surface processes model goSPL (Salles et al., 2023).
From these simulations, we compute time-dependent CO2 degassing rates, using geodynamic outputs, and weathering fluxes, using the formulation of West (2012). Our results reveal fluctuations in degassing rate over a factor of about three, consistent with reconstruction of Earth (Müller et al., 2024) and correlated with seafloor production rate. Weatherability strongly depends on True Polar Wander during supercontinent aggregation, and on sea level fluctuations controlled by seafloor production. Together, these results highlight how geodynamic evolution may regulate the long-term carbon cycle through its interdependent effects on degassing and continental weatherability.
How to cite: Martin, M., Coltice, N., Donnadieu, Y., Maffre, P., Salles, T., Rogger, J., Arnould, M., Husson, L., Leonard, J., Zahirovic, S., and Pellissier, L.: Geodynamic controls on long-term carbon cycle: insights from fully integrated virtual planets, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9305, https://doi.org/10.5194/egusphere-egu26-9305, 2026.
Marine biodiversity hotspots are regions characterized by exceptionally high species richness compared to surrounding areas. Fossil and molecular evidence indicate that these hotspots have shifted across space and time throughout the Cenozoic; yet the mechanisms driving their emergence and relocation remain inadequately understood. Here, we examine these dynamics—and their links to environmental change—using genus-level fossil data for molluscs, cnidarians, and foraminifera compiled from the Paleobiology Database and published sources.
Because publicly available fossil occurrence data exhibit strong geographic and temporal sampling inhomogeneities, sampling standardization is essential for robust interpretation of diversity patterns. To reduce sampling biases, we applied Shareholder Quorum Subsampling (SQS) and identified paleo-hotspots as regions where sampling-standardized richness exceeded global confidence intervals. We detected 40 paleo-hotspots exhibiting distinct clade-specific macro-evolutionary signatures. Using models based on Hierarchical Bayesian structural equations reveal that environmental conditions (sea surface temperature, shelf area, sea level) influence hotspot development formation predominantly by modulating macro-evolutionary processes (origination, extinction, immigration), though the strength and direction of these pathways differ among groups. Cnidarian hotspots arise from high evolutionary turnover, where elevated origination rates and expansive shelf area strongly increase hotspot probability. In contrast, for both benthic and planktic foraminifera, no single environmental or macro-evolutionary factor exerts a dominant direct influence; rather, interconnected processes indirectly shape diversity and, ultimately, hotspot formation. Together, these results show that marine biodiversity hotspots arise through distinct, clade-specific macro-evolutionary mechanisms influenced by the environment.
How to cite: Kella, V. G. and Chattopadhyay, D.: Interacting environmental and evolutionary controls on shifting marine biodiversity hotspots through Cenozoic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1165, https://doi.org/10.5194/egusphere-egu26-1165, 2026.
The African continent has undergone major Cenozoic transformations, including the formation of the East African Rift System and the opening of the Red Sea and the Gulf of Aden. The impact of these transformations on the various components of the Earth system over time—climate, hydrographic networks, and the dispersal and evolution of biological species—raises multiple questions.
In this context, we aim to reconstruct the paleogeographic evolution of continental Africa over the past 30 million years using a multi-layered modelling approach. First, the integration of several geodynamic components (including mantle-driven dynamic topography, the history of crustal tectonics, plate tectonic motions, and volcanic eruptive dynamics) allows us to produce an elevation model for Africa since 30 Ma that is continuous in space and time. This elevation model is then used as a boundary condition for climate simulations, followed by physiographic simulations, generating a more comprehensive and coherent representation of past environments.
The simulation outputs reveal the sensitivity of climate reconstructions to topographic boundary conditions, as well as temporal variations in hydrographic networks. These new topographic, climatic, and physiographic constraints provide improved calibration for future eco-evolutionary studies (e.g., geographic barriers, water availability, resource distribution, and environmental stability) on the African continent.
We then evaluate the spatial and temporal accuracy of these reconstructions by confronting them with field-based evidence. This assessment identifies the scales at which the models are most robust, informing which interrogation can be explored with confidence. It also highlights where the reconstructions are consistent with geological, paleoenvironmental, and paleontological data, and where their precision may require further refinement.
Looking ahead, the objective is to continuously update these maps and simulations, which will also be used to investigate the dispersal and evolutionary changes of Cenozoic faunal communities in Africa, notably early hominids. This whole study offers a coherent spatio-temporal context for evaluating links between the different components of the Earthsystem.
How to cite: Tournier, R., Husson, L., Prat, S., Boisserie, J.-R., Barboni, D., Bellahsen, N., Doubre, C., Pik, R., Salles, T., Sepulchre, P., and Tiberi, C.: African paleogeography since 30Ma : setting boundary conditions for climatic, physiographic and biodiversity models., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7017, https://doi.org/10.5194/egusphere-egu26-7017, 2026.
Biogeodynamics research seeks to link lithospheric scale processes with surface ecosystem evolution. Western Anatolia-Aegean region provides a critical testing ground for this coupling, where mantle dynamics have driven dramatic topographic reversals. Tectonostratigraphic and geomorphic insights indicate that Western Anatolia maintained elevated landscapes prior to and through Early Miocene extension. These observations are inconsistent with simple rift-related thinning but support dynamic uplift driven by removal of dense lithospheric mantle. Here, we integrate geodynamic modeling with geological observations to reconstruct the region's paleoelevation and its control on intercontinental faunal connectivity. Our results indicate that lithospheric delamination (slab peel-back) was the primary driver of Early Miocene topography. Numerical models show that slab peeling from beneath the crust and subsequent asthenospheric upwelling triggered a transient surface uplift of > 1 km and southward younging volcanism from İzmir-Ankara suture to the western Taurides. Supported by metamorphic constraints indicating crustal thickness consistent with elevations of 2–3 km, these results are in good agreement with the existence of a paleo-"Anatolian Highland" at ~20 Ma. Crucially, this geodynamically sustained topography acted as a significant biogeographic barrier. Synthesizing our models with recent fossil record analyses, we suggest that high elevations delayed faunal migration between Eurasia and Afro-Arabia, severing connectivity despite the closure of the Neo-Tethys. The timing of increased biotic interchange in the Middle–Late Miocene coincides with evidence for topographic lowering linked to post-delamination driven by crustal stretching. We conclude that the thermal and mechanical evolution of the Anatolian lithosphere exerted a first-order control on the timing of biotic exchange, highlighting the direct link between lithosphere dynamics and vertebrate evolution.
How to cite: Göğüş, O. H., Saylor, J., Biltekin, D., Sundell, K., Mackaman-Lofland, C., Guan, X., Özyalçın, C., and Bodur, Ö.: Biogeodynamic Barrier: Lithospheric Delamination and Delayed Miocene Faunal Migration in the Anatolian Highland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16889, https://doi.org/10.5194/egusphere-egu26-16889, 2026.
During the last million years, the growth and retreat of massive ice sheets in North America and Eurasia defined the alternating climate conditions of the glacial-interglacial cycle. The main driver of these climatic oscillations is the combined effect of precession, eccentricity, and obliquity frequency modes (Milankovitch cycles) [1]. However, the climate expected from the Milankovitch cycles does not always align with the records from the Marine Isotope Stages [2].
To address this discrepancy, we test the hypothesis that multiple climatic steady states (attractors) exist for a given CO2 concentration and can be destabilized by different combinations of Milankovitch forcing. We developed a biogeodynamical coupled setup, biogeodyn-MITgcmIS [3], which has the MIT general circulation model as its dynamical core, and asynchronously couples hydrology, ice sheets, and vegetation. The results of this new coupled model show that including the long-term dynamics of vegetation and ice sheets is crucial to evaluate past and future climate trajectories.
First, we construct the bifurcation diagram by varying the CO2 concentration between 180 ppm and 320 ppm (i.e., within the observed range over the last 1 Myr). We analyze the stability range of the cold (glacial) and warm (interglacial) attractors, and identify their tipping points at the global scale. Second, we repeat selected simulations with different Milankovitch configurations to evaluate the robustness of the bifurcation structure. Finally, to detect signatures of climate multistability, we compare the simulation outputs with global mean sea level and temperature reconstructions [4], and we discuss preliminary results.
[1] Barker et al. Science 387, eadp3491 (2025)
[2] Past Interglacials Working Group of PAGES, Rev. Geophys. 54, 162–219 (2016)
[3] Moinat et al. EGUsphere [preprint], https://doi.org/10.5194/egusphere-2025-2946 (2025).
[4] Clark et al. Science 390, eadv8389 (2025)
How to cite: Moinat, L., Vérard, C., Goldberg, D. N., Kasparian, J., Gerya, T., Marshall, J., and Brunetti, M.: Effect of the Milankovitch cycles on climate multistability for the last 1 Myr, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7612, https://doi.org/10.5194/egusphere-egu26-7612, 2026.
Prevailing interpretations of large underground cavities in carbonate terrains are predominantly based on karst-related genetic models, in which dissolution-driven hydrological processes are assumed to be the primary mechanism of formation. While effective for explaining certain cave types, these models commonly rely on an implicit assumption: that underground cavities should be analyzed as isolated natural features. This assumption has limited the recognition of broader spatial patterns and system-level organization.
This study proposes a geoarchaeological, system-based approach to the interpretation of underground spaces, using the Zagros Mountains as a key case study. Given the extensive carbonate lithology of the region, classical karst theory would predict cave development closely associated with active or fossil drainage networks. However, field observations reveal a contrasting pattern, with numerous underground openings located at elevated positions, often on cliff faces or near ridgelines, lacking any evidence of hydrological concentration or outlet channels.
A focal example is provided by the Deh Sheikh area (central Zagros), where multiple underground entrances occur at the same elevation level and are separated by relatively regular horizontal distances. Such repeated and level-aligned configurations are difficult to reconcile with stochastic karstic dissolution processes and instead suggest a coherent spatial logic that becomes visible only when these features are considered collectively rather than individually.
Additional evidence includes stable arched geometries and persistent cavities that contrast with the irregular, downward-oriented erosion expected from water-dominated processes. These observations indicate that natural processes observed today are largely secondary modifications, overprinting earlier phases of space formation.
Rather than rejecting natural cave formation mechanisms, this study argues that, in the Zagros region, a system-based geoarchaeological framework provides a more coherent and parsimonious interpretive model. The results highlight the importance of analytical scale and interdisciplinary perspectives in re-evaluating underground spaces.
How to cite: Baghbani, F. and Baghbani, H.: From Isolated Caves to Spatial Systems: A Geoarchaeological Re-reading of Underground Spaces in the Zagros Mountains, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5975, https://doi.org/10.5194/egusphere-egu26-5975, 2026.
The progressive restriction of seaways between the Caribbean and Pacific during the formation of the Isthmus of Panama fundamentally reorganized ocean circulation, biogeochemical cycling, and marine ecosystem structure across the tropical Americas. This tectonically driven reorganization provides a natural experiment for examining how long-term Earth system processes influence the structure, stability, and resilience of biological communities. The Bocas del Toro region of Caribbean Panama preserves a rich fossil record that captures ecological responses to these coupled physical and environmental changes.
This study examines temporal variation in marine community composition and functional trait structure using fossil assemblages from four marine formations: Cayo Agua, Escudo de Veraguas, Old Bank, and Isla Colón, spanning approximately 6.0 to 0.43 Ma. The analyses integrate multiple taxonomic groups, including bivalves, gastropods, bryozoans, corals, and fishes, enabling comparison of ecological responses among organisms that differ in life habit, mobility, feeding strategy, tiering, and ecological function. By incorporating multiple clades with contrasting ecologies, this approach allows assessment of whether community change reflects reorganization within broadly conserved functional roles or more fundamental shifts in ecosystem structure.
Community dynamics are quantified using a combination of model-based ordination, taxon-specific response analyses, and functional diversity metrics applied within a stratigraphic framework. These methods explicitly account for variation in sampling intensity and taxonomic richness, allowing ecological patterns to be distinguished from sampling effects. Biological patterns are evaluated alongside sedimentological and geochemical records to place community dynamics within their environmental context. Environmental–trait and environmental–taxon relationships are evaluated within a generalized linear latent variable modeling (GLLVM) framework to assess how changes in physical conditions, sedimentary processes, and geochemical variability influence community reorganization before, during, and after the formation of the Isthmus of Panama. Comparisons among contemporaneous formations allow local ecological responses to be distinguished from regionally coherent environmental signals.
Overall, this study aims to clarify how long-term tectonic and oceanographic reorganization shapes marine ecosystem structure and stability, providing a stratigraphically grounded perspective on the links between Earth system processes and ecological dynamics over geological timescales.
How to cite: Godbold, A., O’Dea, A., Grossman, E. L., de Gracia, B., Pardo Díaz, J., Pallacks, S., Todd, J., Johnson, K., and Connolly, S. R.: Biogeodynamic controls on Caribbean community structure during the formation of the Isthmus of Panama , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15410, https://doi.org/10.5194/egusphere-egu26-15410, 2026.
Long-term sustainability of human civilization depends on secure supplies of metals and critical minerals that underpin energy systems, infrastructure, and technology (IEA, 2021; UNEP, 2024). By 2040, total mineral demand from clean energy technologies is expected to double or quadruple (IEA, 2021), raising concerns about long-term supply sustainability as anthropogenic extraction operates on timescales and magnitudes unconstrained by geological ore-forming rates. Although recycling and substitution can mitigate pressure, widely adopted outlooks still require substantial expansion of primary supply and are commonly framed around reserves, production, and announced project pipelines (IEA, 2024; USGS, 2025).
We present a plate-kinematic framework to forecast ore deposit formation over the next 10 Myr by coupling tectonic setting–specific deposit-generation functions to a forward plate-motion model. Unlike reserve- or discovery-trend extrapolations, this approach explicitly links plate tectonics to mineralization rates, providing a first-order estimate of Earth’s natural “mineral renewal” capacity (IEA, 2024; USGS, 2025). We apply the method to two deposit types: (1) porphyry–epithermal systems in continental arcs, parameterized by plate convergence rates and lithospheric factors (crustal thickness, slab composition, and proxies for slab oxidation state), reflecting how rapid convergence and thick crust favor porphyry formation, while explicitly accounting for melt–fluid–driven mass transfer of copper and oxidized species within subduction zones; and (2) mid-ocean ridge seafloor massive sulfides (SMS), linked to spreading rate, ridge depth, and detachment fault occurrence at slow-spreading centers. These parameterizations are integrated into a global 1°-resolution plate model extrapolated 10 Myr into the future to produce spatially explicit, time-dependent maps of ore-forming potential. Because most new oceanic crust is not subducted within a 10 Myr horizon, our model estimates gross SMS formation within a limited accessibility window (controlled by sediment burial), while acknowledging subduction recycling as a longer-term sink.
The resulting formation- and accessibility-weighted metrics provide benchmarks for Earth’s natural mineral replenishment rate, against which scenario-based demand projections can be compared, thereby strengthening sustainability discussions with geodynamically grounded constraints.
References:
International Energy Agency (IEA): The Role of Critical Minerals in Clean Energy Transitions, IEA, Paris, 2021.
International Energy Agency (IEA): Global Critical Minerals Outlook 2024, IEA, Paris, 2024.
United Nations Environment Programme (UNEP) and International Resource Panel (IRP): Global Resources Outlook 2024 – Bend the trend: Pathways to a Liveable Planet as Resource Use Spikes, UNEP, 2024, doi:20.500.11822/44901.
U.S. Geological Survey (USGS): Mineral Commodity Summaries 2025 (ver. 1.2, March 2025), U.S. Geological Survey, 212 pp., doi:10.3133/mcs2025, 2025.
How to cite: Ciazela, J., Gerya, T., Verard, C., Stern, R., Leybourne, M., and Duan, W.: A Plate-Tectonic Framework for Predicting Ore Deposit Formation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4337, https://doi.org/10.5194/egusphere-egu26-4337, 2026.
The Phanerozoic Eon is characterized by profound variability in global climate and biogeochemical cycles, driven by some combination of the formation and break up of supercontinents, changes to tectonic degassing, the emplacement of Large Igneous Provinces and by biosphere evolution. Understanding the key drivers of these environmental transitions is an ongoing challenge in deep-time Earth system science.
The Spatially Continuous IntegratiON (SCION) climate-biogeochemical model is often used for the analysis these processes, and has successfully reproduced a number of first-order global trends through the Phanerozoic (1) and Neoproterozoic (2), including reconstructions of atmospheric CO₂, atmospheric O₂, and surface temperature. But many notable mismatches still occur, e.g. during the late Paleozoic icehouse interval and in the underestimation of warmth during the Cretaceous greenhouse period. Furthermore, many novel or revised proxy records have not yet been compared to the model outputs (e.g. global erosion rates (3), or new records for Phanerozoic temperature evolution (4) and atmospheric CO₂ (5)).
Here, we present a new integration of multiple environmental proxy record compilations with the SCION model outputs. We determine the key periods of model-data mismatch and explore possible solutions within the current model formulation, or possible model extensions. We then suggest critical intervals where proxy development or sampling work may be best directed.
(1) Merdith et al., 2025, Science Advances
(2) Mills et al., 2025, Global and Planetary Change
(3) Hay et al., 2006, Palaeo3
(4) Judd et al., 2024, Paleoclimate
(5) Steinthorsdottir et al., 2024, Treatise on Geochemistry
How to cite: Krewer, C. and Mills, B. J. W.: Modelling the Phanerozoic: Discrepancies and conformity with the geological record, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11212, https://doi.org/10.5194/egusphere-egu26-11212, 2026.
Despite evidence for generally elevated atmospheric CO₂ concentrations, the climate of the early Phanerozoic appears to have been neither uniformly warm nor stable. Proxy records, climate simulations, and paleogeographic reconstructions all carry large uncertainties, yet taken together they suggest that greenhouse forcing alone may not fully explain observed climatic variability, including intervals of pronounced cooling, such as the Hirnatian Glaciation. Understanding how early Phanerozoic climate responded to high CO₂ therefore requires explicit consideration of the boundary conditions under which greenhouse forcing operated.
Here, we examine the combined roles of paleogeography, land-surface properties, and reduced solar luminosity in shaping early Phanerozoic climate states. Using an intermediate-complexity Earth system model, we systematically explore climate sensitivity across a wide range of atmospheric CO₂ concentrations under pre-vegetation boundary conditions and early Paleozoic paleogeographic configurations. The experimental design focuses on how land–sea distribution, continental arrangement, and surface characteristics influence large-scale heat transport, cryospheric feedbacks, and the CO₂ levels required to maintain ice-free conditions.
Our working hypothesis is that early Phanerozoic climates were intrinsically biased toward cooler states relative to later, vegetated periods, due to higher surface albedo, altered hydrological cycling, and reduced incoming solar radiation. In such a climate system, maintaining temperate conditions may have required persistently high CO₂ concentrations, while gradual CO₂ drawdown could have positioned the system close to critical thresholds. Under these circumstances, comparatively small paleogeographic changes—such as shifts in continental connectivity or topographic relief—may have been sufficient to trigger short-lived glacial episodes, without invoking abrupt or extreme changes in greenhouse forcing.
By framing early Phanerozoic climate evolution as a problem of threshold behavior under uncertain boundary conditions, this work aims to clarify why high CO₂ and cooling are not necessarily incompatible. The results will help constrain which combinations of forcing and boundary conditions are physically plausible and guide more robust interpretations of proxy records and future paleoclimate modeling efforts.
How to cite: Werner, N., Franziskakis, F., Merdith, A., Vérard, C., Brunetti, M., Gerya, T., and Tackley, P.: Climate Sensitivity in a Pre-Plant World: Why High CO₂ May Not Have Been Sufficient to Maintain a Paleozoic Hothouse, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7546, https://doi.org/10.5194/egusphere-egu26-7546, 2026.
Cenozoic greenhouse climates offer important insights into Earth’s climate system and carbon cycle under elevated CO2 conditions. A major challenge in simulating these warm intervals lies in the accurate reconstruction of the paleogeography, yet its impact on modeled climates and their agreement with proxy data remains poorly quantified. In this study, we systematically assess the sensitivity of fully coupled climate simulations to alternative paleogeographic reconstructions for the Paleocene, early Eocene, and middle-late Eocene. Using the IPSL-CM5A2 Earth System Model, we find that regional climates are particularly sensitive to the paleolatitudinal position of landmasses and ocean basins. Latitudinal shifts of more than 5°, arising from the choice of mantle versus paleomagnetic reference frame, significantly alter modeled regional temperature and precipitation patterns, as well as ocean circulation patterns. Moreover, we demonstrate that reconciling simulated climates with temperature proxy data depends strongly on the reconstructed paleolatitude of the proxy sites. In regions such as the southwest Pacific, correcting for paleolatitude bias induced by a mantle frame reduces model-data temperature misfits by up to 5°C. Our results further show that the regional climatic impact of paleogeography can equal or even exceed that of a doubling of atmospheric CO2, particularly at mid-latitudes. These findings highlight the importance of using accurate paleogeographic reconstructions and an appropriate reference frame for improving paleoclimate simulations and their integration with proxy data.
How to cite: Vaes, B., Donnadieu, Y., Licht, A., Pineau, E., Maffre, P., Chalk, T., and Sternai, P.: Paleolatitude bias in reconstructions of Cenozoic greenhouse climates, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11558, https://doi.org/10.5194/egusphere-egu26-11558, 2026.
Insects are the most diverse groups on earth and preserved with plenty of fossils. Disentangling their ecological roles are crucial for understanding the evolution of terrestrial ecosystems, however, reconstructing the adaptive evolution of extinct insects has been proven to be highly challenging. Here, we conduct integrated approaches to reveal the macroevolution of two insect clades, katydids (Hagloidea) and giant cicadas (Palaeontinidae), on the basis of newly compiled morphological datasets. Our results provide novel information for coevolution of insects and vertebrates in the Mesozoic, and highlight the significance of fossil morphologies. 1) Acoustic evolution of katydids. We present a database of the stridulatory apparatus and wing morphology of Mesozoic katydids and analyze the evolution of their acoustic communication. Our results demonstrate that katydids evolved complex acoustic communication including mating signals, intermale communication, and directional hearing, by the Middle Jurassic; evolved high-frequency musical calls by the Late Triassic. The Early—Middle Jurassic katydid transition coincided with the diversification of mammalian clades, supporting the hypothesis of the acoustic coevolution of mammals and katydids. 2) Flight evolution of giant cicadas. We reveal the flight evolution of the Mesozoic arboreal insect clade Palaeontinidae. Our analyses unveil a faunal turnover from early to late Palaeontinidae during the Jurassic–Cretaceous, accompanied by a morphological adaptive shift and improvement in flight abilities including increased speed and enhanced maneuverability. The adaptive aerodynamic evolution of Palaeontinidae may have been stimulated by the rise of early birds, supporting the hypothesis of an aerial evolutionary arms race between Palaeontinidae and birds.
How to cite: Xu, C.: Coevolution of Insects and vertebrates in the Mesozoic: examples from katydids and giant cicadas, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15628, https://doi.org/10.5194/egusphere-egu26-15628, 2026.
Geodynamic redistribution of continents fundamentally reshapes Earth’s climate, ocean circulation, and nutrient cycles, thereby exerting a first-order control on biological evolution. A possible example of this coupling is the Cambrian explosion, a rapid diversification of animal life that followed profound tectonic, climatic, and oceanographic reorganization during the late Neoproterozoic. However, identifying the causal drivers of the Cambrian explosion remains challenging due to the fragmentary geological record. To circumvent these limitations, we implement an integrated, mechanistic simulation framework that integrates the key Earth system processes governing climate, circulation, surface evolution, and marine biogeochemistry, allowing their interactions to be explored consistently in space and time. These components provide time-evolving boundary conditions for biological productivity, oxygen availability, and nutrient supply, which are then used to study how changing environmental states shape the range of biologically feasible organismal strategies. Rather than simulating realized biodiversity or reconstructing a specific episode of Earth history, the model explores the full dynamical evolution of an Earth-like system across a supercontinent cycle, from continental assembly to breakup. In this framework, changing Earth system states expand or restrict the range of biologically feasible organismal strategies, providing a quantitative link between paleogeographic restructuring and the environmental opening of functional trait space relevant to the Cambrian explosion.
How to cite: Lewkowicz, A., Affholder, A., Coltice, N., Martin, M., Salles, T., Werner, N., Leonard, J., and Pellissier, L.: Linking paleogeography and Earth system dynamics to evolutionary innovation during the Cambrian Explosion , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16603, https://doi.org/10.5194/egusphere-egu26-16603, 2026.
Emerging geochemical evidence suggests highly heterogeneous ocean redox conditions in the mid-Proterozoic. Quantitative estimates of the extent of different modes of anoxia, however, remain poorly constrained. Considering the complementary redox-related behaviour, uranium and molybdenum isotopes can be combined to reconstruct ancient marine redox landscapes, which has not been applied to the mid-Proterozoic. In this study, we present new δ238U and δ98Mo data for shales from the ~1.4 Ga Xiamaling Formation, North China Craton, together with independent redox proxies, including Fe speciation and redox-sensitive trace metals. We find that most oxic and dysoxic samples retain low U and Mo concentrations, with δ238U and δ98Mo values indistinguishable from continental crust. While euxinic samples record the highest authigenic δ238U and δ98Mo, consistent with efficient reduction of U and Mo. Samples deposited under ferruginous conditions exhibit a wider range of δ238U and δ98Mo values that generally fall between the (dys)oxic and euxinic end-members. Using a coupled U-Mo isotope mass balance model, we infer limited euxinia but extensive low productivity, ferruginous conditions in mid-Proterozoic oceans.
How to cite: Song, Y., Mills, B., Bowyer, F., Andersen, M., Ossa Ossa, F., Dickson, A., Harvey, J., Zhang, S., Wang, X., Wang, H., Canfield, D., Shield, G., and Poulton, S.: Tracking the spatial extent of redox variability in the mid-Proterozoic ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5361, https://doi.org/10.5194/egusphere-egu26-5361, 2026.
Paleogeographic reconstructions of the deep past are affected by large uncertainties due to limitations in dating, the scarcity of sedimentary sequences, and imperfect constraints on the positions of tectonic plates. These uncertainties in the boundary conditions propagate into climate simulations, affecting their accuracy.
In this study, we compare two paleogeographic reconstructions, Panalesis [1] and PaleoMap [2], to assess how differences in the paleogeographic reconstructions influence the climate response at the Permian-Triassic Boundary. Climate simulations are performed using biogeodyn-MITgcmIS [3], a recently developed modelling tool in which the dynamical core of both the atmosphere and the ocean is provided by the MIT general circulation model, while offline coupling ensures the consistent evolution of vegetation and ice sheets (when present).
Beyond the direct comparison of paleogeographic reconstructions, aquaplanet and simplified configurations are employed under the same paleoclimate conditions to isolate feedbacks arising from land distribution. The resulting steady-state climates are systematically compared with those obtained using Pangea configurations derived from Panalesis and PaleoMap. The impact on terrestrial vegetation is also estimated and discussed. Overall, the results provide a framework for systematically assessing how paleogeographic reconstructions affect coupled climate-biosphere dynamics.
References
[1] Vérard, Geological Magazine 156, 320 (2019)
[2] Scotese, Atlas of Earth History, PALEOMAP Project (2001)
[3] Moinat et al., EGUsphere [preprint], https://doi.org/10.5194/egusphere-2025-2946 (2025).
How to cite: Kang, B., Moinat, L., Ragon, C., Vérard, C., and Brunetti, M.: How palaeogeographic reconstructions influence climate: the Permian-Triassic Boundary case study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7068, https://doi.org/10.5194/egusphere-egu26-7068, 2026.
During the Cambrian explosion, animals underwent profound ecological and evolutionary configuration. Small shelly fossils (SSFs), micrometre- to millimetre-scale skeletal elements representing multiple animal phyla, are particularly valuable for early Cambrian biostratigraphy and intercontinental correlation because of their widespread distribution. SSFs from North Greenland provide a high-resolution record of biotic and environmental change along the eastern margin of Laurentia. Here, we document a SSF assemblage that includes molluscs, hyoliths, brachiopods, ecdysozoans, echinoderms, and several problematic taxa from the Aftenstjernesø Formation in North Greenland. This integrated dataset enables detailed correlation with other Cambrian Series 2, Stage 4 successions on several palaeocontinents, including Gondwana, Siberia, and peri-Gondwana, based on shared taxa. During this period, many regions record a major faunal collapse associated with the first widely recognized Phanerozoic extinction event, the so-called Sinsk event, which has been linked to marine anoxia, decrease of diversity, and body-size reduction. In contrast, the Laurentian margin records pronounced taxonomic turnover dominated by faunal replacement rather than a net loss of diversity. This difference underscores the importance of palaeogeography and local geodynamic conditions in modulating how early Cambrian environmental crises were expressed biologically, and it demonstrates the utility of SSFs for reconstructing the biotic response to early Cambrian environmental crises.
How to cite: Oh, Y., Park, T.-Y. S., and Peel, J. S.: Global correlation of small shelly fossils from North Greenland and their importance for early Cambrian ecosystem change, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8575, https://doi.org/10.5194/egusphere-egu26-8575, 2026.
The supercontinent cycle is often accompanied by True Polar Wander (TPW) events (Evans, 2003) — reorientation of the silicate Earth relative to its spin axis in response to internal mass redistribution. During TPW events, the maximum inertia axis (Imax) aligns with the spin axis to conserve the angular momentum (Gold, 1955). While an assembled supercontinent typically reside near the equator once it has developed its own degree-2 mantle structure driven by a circum-supercontinent subduction girdle with two antipodal superplumes (Li et al., 2023), this configuration is not always instantaneous with the assembly of a supercontinent. Supercontinent is in fact believed by some to assembly over a degree-1 mantle structure: a cold downwelling beneath the supercontinent and a hemispheric superplume on the opposite hemisphere (Zhong et al., 2007; Zhong and Liu, 2016). The resulting TPW behavior during such processes remains poorly constrained. Here we report a novel computational framework that couples 3D spherical mantle convection (CitcomS) with Earth’s rotational dynamics to simulate TPW driven by both convective mass anomalies and rotational bulge readjustment. We particularly examined the effect of varying upper/lower mantle viscosity ratios (ηum/ηlm).
Our results reveal a critical dependence of TPW behavior on viscosity stratification. For high ηum/ηlm (1:30), supercontinents assemble near the pole over a degree-1 mantle structure. Subsequent formation of a subduction girdle triggers TPW, transporting the supercontinent to the equator. In contrast, low ηum/ηlm (1:100) with a mean lower-mantle viscosity of 3×1022 Pa·s promotes equatorial assembly. Here, girdle development induces TPW that transports the supercontinent toward the pole, where it stabilizes for a considerable period. However, reducing lower-mantle viscosity destabilizes this polar position, causing rapid return to the equator. These dynamics arise because viscosity stratification determines the structure of the geoid kernel, which governs the geoid’s response to mass anomalies and thereby modulates TPW pathways. Our models demonstrate that before a stable degree-2 structure (e.g., modern LLSVPs) is developed, TPW can drive complex supercontinent trajectories—including equator-to-pole-to-equator round-trip migrations. Future work integrating plate reconstruction with viscosity constraints will refine predictions for specific supercontinents.
Evans, D. True Polar Wander and Supercontinents. Tectonophysics 362, 303-320 (2003).
Gold, T. Instability of the Earth’s axis of rotation. Nature 175, 526–529 (1955).
Li, Z.-X., Liu, Y. & Ernst, R. A dynamic 2000–540 Ma Earth history: From cratonic amalgamation to the age of supercontinent cycle. Earth-Science Reviews 238, 104336(2023).
Zhong, S., Zhang, N., Li, Z.-X. & Roberts, J. H. Supercontinent cycles, true polar wander, and very long-wavelength mantle convection. Earth and Planetary Science Letters 261, 551–564 (2007).
Zhong, S. & Liu, X. The Long-Wavelength Mantle Structure and Dynamics and Implications for Large-Scale Tectonics and Volcanism in the Phanerozoic. Gondwana Research 29: 83-104 (2016).
How to cite: Liu, Y., Li, Z.-X., and Liu, X.: Numerical Simulation of True Polar Wander during Supercontinent Assembly, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10596, https://doi.org/10.5194/egusphere-egu26-10596, 2026.
During the Neoproterozoic, early land biota consisted of cyanobacteria, microalgae and various fungi or fungi-like communities. Although called micro-organisms, their role in stabilising environments, and driving and controlling nutrient cycles [1], creates a macro-scale impact. Photosynthetic microbial mats are predicted to have been present ~3 billion years ago, creating microcosms of oxygen-rich environments that contribute towards global net primary productivity, weathering and nitrogen fixation [2]. However due to the lack of fossil evidence and understanding of their role in a non-vegetated environment, it is unclear what their impact is on biogeochemical cycling and thus the shaping of Neoproterozoic climate. Building on the new process based spatial vegetation model [3], we try to understand the role of expanding microbial communities on events such as the Neoproterozic Oxygenation Event and Snowball Earth.
[1] Taylor, T.N., Krings, M. (2005) Fossil microorganisms and land plants: Associations and interactions. Symbiosis 40:119-135
[2] Lenton, T.M., Daines, S.J. (2016) Matworld- the biogeochemical effects of early life on land. New Phytologist 215: 505-507
[3] Gurung, K., Field, K.J, et al. (2024) Geographic range of plants drives long-term climate change. Nature Comms 15: 1805
How to cite: Gurung, K. and Mills, B. J. W.: Influence of terrestrial productivity by photosynthetic microbial mats on biogeochemical cycles over the Neoproterozoic landscape, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11296, https://doi.org/10.5194/egusphere-egu26-11296, 2026.
The mass extinction occurred at the Cretaceous/Paleogene (K/Pg) boundary event, approximately 66 million years ago, which resulted in global-scale biotic turnover that was ecologically diverse but selective. This extinction coincides with both the activities of Deccan Traps volcanism spanning approximately one million years and a large asteroid impact which formed the Chicxulub crater on the Yucatan Peninsula, Mexico. These two events and their environmental and biological consequences left a global imprint in the deep-sea sediments. Deep-sea sediment records indicate the collapse of the oceanic bottom-to-surface gradient of carbon isotope ratio and the carbonate compensation depth (CCD) deepening for several hundred thousand years after the K/Pg boundary. The collapse of the carbon isotope gradient has been variously interpreted as changes in biological production, including a global shutdown of primary production, reduced export production, and enhanced spatial heterogeneity. However, these interpretations remain insufficiently tested for consistency with the geological records. The pronounced long-term decline of carbonate mass accumulation rates (MAR) after the K/Pg boundary is also indicated from deep-sea records. This suggests the necessity of a prolonged reduction in biological carbonate productivity. However, existing boron isotope-based ocean surface pH reconstructions do not support prolonged and severe ocean acidification, making it difficult to explain the long-term decrease of carbonate MAR.
Here, we first investigate changes in marine biological productivity and particulate organic matter (POM) decomposition rate using a vertical one-dimensional ocean carbon cycle model to interpret the collapse of the vertical carbon isotope gradient. We find that, provided POM production and burial persist in coastal regions, the collapse can be explained by either reduced export productivity in the open ocean or reduced POM sinking rates, but cannot discriminate them from the modeling of this study with existing data. These results support the discussion of Kump (1991) and the Living Ocean hypothesis (e.g., D’Hondt et al., 1998). In this model, the CCD deepened, but carbonate production rate was comparable to previous modelling studies, and we were unable to reproduce the pronounced long-term decline of carbonate MAR after the K/Pg boundary event.
Next, we explore an alternative explanation for the long-term decline in carbonate MAR based on changes in the structure of primary producers. At the K/Pg boundary, calcareous nannoplankton, such as coccolithophores, experienced catastrophic extinction, whereas non-calcifying phytoplankton, such as diatoms, were relatively resilient. In addition, enhanced diatom productivity has been suggested for several hundred thousand years following the K/Pg boundary in the South Pacific. Therefore, climate change and ocean eutrophication following the K/Pg boundary may have favored diatom primary production at the expense of carbonate production by calcareous nannoplankton, but its quantitative contribution remains poorly constrained. We will distinguish calcareous nannoplankton and diatoms by their physiological characteristics and explore how background environmental changes sustain enhanced diatom abundance and reduced carbonate production.
How to cite: Takeda, T. and Tajika, E.: Modelling the changes in marine ecosystem and carbon cycle after the K/Pg boundary event, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11517, https://doi.org/10.5194/egusphere-egu26-11517, 2026.
How to cite: Franziskakis, F., Werner, N., Vérard, C., Castelltort, S., and Giuliani, G.: Assessing Sediment Flux Evolution for the entire Phanerozoic with Palaeogeography and Palaeoclimate simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17018, https://doi.org/10.5194/egusphere-egu26-17018, 2026.
Volcanic ash is known to influence a range of biogeochemical processes once deposited in the oceans, with explosive volcanism inputting large amounts of highly reactive and nutrient-rich material to the oceans every year. This material can stimulate increases in primary productivity, with ash alleviating nutrient limitations. This may eventually lead to enhanced carbon burial at the seafloor, with evidence from deep time suggesting this process may play a role in episodes of global cooling. As a result, reconstructing the amount of volcanic ash entering the oceans is important for understanding the role explosive volcanic activity has on global climates. However, extant records of changing volcanic intensity are either limited to regional studies of small numbers of volcanoes or are based on imperfect methods such as visible tephra layer counting.
In this work, we use the output of a model-derived dataset of sediment provenance from the Pacific Ocean, which provides estimates of changing volcanic material input for 67 sites. We use these data, and an inverse weighting approach, to reconstruct changing levels of volcanic ash input for the Cenozoic Period (66 million years ago to present). With around 75% of all active volcanoes located in the Pacific Ring of Fire, this record likely represents the majority of all volcanic ash through the Cenozoic, and so we compare it to known climate change through the period. We see increases in volcanic ash input around 35 million years ago and 10 million years ago, which can be linked to eruptions from the Sierra Madre Occidental, and Izu Bonin Arc, respectively. The first uptick occurs at the same time as the Eocene-Oligocene transition, an episode of global climate cooling, whilst the second covers the descent into the Pleistocene glaciations. These findings hint at the climatic impact of ash input, one which has major implications for the development of the Earth system.
How to cite: Longman, J., Dunlea, A. G., and Merdith, A. S.: Reconstructing volcanic ash input to the Pacific Ocean: how does it link to Cenozoic climate?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14220, https://doi.org/10.5194/egusphere-egu26-14220, 2026.
Sediment-hosted copper–cobalt and base metal deposits are critical to the global energy transition, yet the environmental conditions that favour their formation and preservation through Earth history remain poorly understood. Evaporites are considered crucial for the formation of sediment-hosted ore deposits as they generate saline brines that circulate metals and sulphur. These tend to form in desert belts at particular latitudes where evaporation outpaces rainfall. The world’s largest sediment-hosted Cu-Co deposits – located in the Central African Copperbelt – are hosted by Neoproterozoic rocks that formed during one of Earth’s most chaotic climatic periods. Whether this is a coincidence, or whether extreme climate plays a role in mineralisation remains to be tested. The relative roles of tectonic setting, climate and latitude remain poorly constrained but have important implications for predicting where sediment-hosted ore deposits formed in deep time.
We integrate a global database of sediment-hosted ore deposits with full-plate tectonic reconstructions spanning the last billion years to explore the relationship between deposits, paleolatitude and tectonic setting. Plate reconstructions and fossil rift margin datasets are used to assess the spatial association between ore deposits and long-lived extensional settings, with a focus on Neoproterozoic basins.
Preliminary results indicate a spatial correlation between sediment-hosted ore deposits and rifted continental margins. Paleolatitude reconstructions suggest that many deposits formed at low to mid latitudes; however, their distribution varies through time, which may be driven by major climatic fluctuations, including global-scale glaciations. Ongoing work integrating depositional age constraints from key regions and paleoclimate model outputs aims to further quantify these relationships and refine predictive frameworks for underexplored sedimentary basins.
How to cite: Armistead, S. and Williams, S.: Tectonic and climatic influence on sediment-hosted ore deposits in deep time , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16017, https://doi.org/10.5194/egusphere-egu26-16017, 2026.
The Pannonian Basin in Central and Southeastern Europe is a huge landlocked basin delineated by Alpine-Carpathian-Dinarides chain. This extensional backarc basin originating by tectonic rifting in the Early Miocene, was successively flooded by the Central Paratethys Sea. Slovenian Corridor along the Alpine-Dinarides junction enabled its communication with the Mediterranean Sea. Marine flooding of the southern part of the Pannonian Basin - between the Styrian Basin in Austria and Velika Morava Basin in Serbia - is still poorly understood. While the conflicting biostratigraphic interpretations contribute to ongoing discussion on timing and mode of this major environmental turnover, independent radiometric data are still rare. The present study contributes three new U-Pb zircon ages which are the very first such data on the Miocene marine transgression in northern Bosnia and Herzegovina. Dating from autochthonous tephra airfalls prove uniformly the middle Badenian age for marine transgression, with a 0.5 Ma eastwards-younging trend of its onset. This trend stays in line with the literature data suggesting a steady eastwards propagation of extension along the Pannonian Basin southern margin. Towards a better understanding of interplay between tectonic and glacioeustatic forcing of the regional marine progression, a review of published stratigraphic data has been conducted, depicted correspondingly in four paleogeographic maps of one-million-year resolution. Building on these data, we bracket the initial gradual flooding interval to the late Burdigalian–early Serravallian time interval, respectively, attaining up to 3.5 Myr overall duration in a step-wise manner. Although the tectonic phases were main drivers in the creation of accommodation space, along the NE Dinarides, glacioeustasy driven by the global climate suspended landward propagation of the coastline during sea-level low-stands at long obliquity nodes. This result enables a more precise reconstruction of the interplay between landward sea ingression, regional climate change and effects to endemic evolution of biota inhabiting long-lived paleolakes in adjoining intramountainous basins.
This research was funded by the Austrian Science Fund (FWF) grant DOI 10.55776/I6504 and by the Deutsche Forschungsgemeinschaft (DFG) grant no. TO 1364/3-1.
How to cite: Mandic, O., Andrić-Tomašević, N., Šamarija, R., Ćorić, S., Rundić, L., Zeh, A., Pavelić, D., Vrabac, S., and Grunert, P.: Timing and mode of initial marine flooding in the southern Pannonian Basin: new U-Pb age constraints from the Prnjavor and Tuzla basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17538, https://doi.org/10.5194/egusphere-egu26-17538, 2026.
The strontium isotope ratio of 87Sr/86Sr is one of the best-defined tracers of Earth’s evolving surface environment over the Eon of macroscopic life, due to the long residence time of Sr in the ocean. If offers tantalising clues about past CO2 emissions and the rate of continental weathering, which are vital considerations for understanding Earth’s changing surface temperature, climate, and atmospheric oxygen abundance. However, the Sr isotope ratio has strong regional lithological control, with mafic and felsic rocks having dramatically different isotopic compositions, which limits any simple analysis of Sr ratios over Phanerozoic timescales. We present an update to the SCION Earth Evolution Model, which allows it to track the spatial distribution of lithologies and Sr compositions over deep time, enabling regional-scale Sr isotope inputs to be assessed in the context of wider Earth system evolution. We use this to explore to what degree we currently understand the Phanerozoic Sr record, and how it can be used as a proxy to validate or falsify theories about long-term climate change and oxygen levels.
How to cite: Mills, B., Longman, J., and Merdith, A.: Understanding the drivers of the Phanerozoic strontium isotope record, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18914, https://doi.org/10.5194/egusphere-egu26-18914, 2026.
Environmental variables like temperature, land availability and food availability constrain the ecological niches of terrestrial animals and, along with atmospheric oxygen levels, likely had a direct effect on their evolution and distribution over geological time. In this study we develop an agent-based terrestrial palaeoecological model, which we couple to an Earth system model to reconstruct how Earth’s habitability for terrestrial mammals has changed over the Mesozoic to Cenozoic eras. This allows us to investigate whether there was an environmental component to the early Cenozoic mammal radiation. Our findings indicate that Earth’s habitability for terrestrial mammals was maximised during the Cretaceous–Paleogene interval, due to the combination of elevated plant Net Primary Productivity (NPP), expansion of continental land areas, minimal glaciation, and elevated atmospheric oxygen levels. We propose that the rapid diversification of mammals during this period, while clearly enabled by the extinction of non-avian dinosaurs, was also influenced by the enhanced habitability of Earth’s surface during this time. Similar environmentally-driven changes in terrestrial habitability likely also play a significant role for other palaeobiological events.
How to cite: Hadjigavriel, N.: Early Cenozoic mammal radiation coincides with increased terrestrial habitability, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3338, https://doi.org/10.5194/egusphere-egu26-3338, 2026.
The reconstruction of paleogeography, that is, the reconstruction of Earth’s surface elevation within a plate tectonic context, is crucial for understanding changes in past climate, sea level, as well as variations in biodiversity through deep time. Although often presented as picturesque maps in publications or even museums, paleogeography reconstructions can provide important geoscientific context and serve as a key boundary condition in many aspects of Earth science including, but not limited to, the simulation of past climates and landscape evolution modelling. However, despite the potential influence and impact of paleogeography on many aspects of Earth’s history, there are very few published global reconstructions of paleogeography, and available reconstructions are often constrained to a single time slice (e.g., Middle Miocene, ~15 Ma), or are available in and represent longer (~5–10 Myr) increments. Additionally, there are major uncertainties in reconstructions of paleogeography, in part due to the poor temporal and/or spatial coverage of proxy data, but also uncertainties within the underlying workflows used to derive its key components. Here, I examine published paleogeography reconstructions throughout the Cenozoic, focusing on key time intervals. I compare the similarities and differences in reconstructions, including aspects of their workflows and sources of uncertainties within them. Finally, I present new approaches for generating paleogeography and quantified uncertainties in a more open and reproducible framework, allowing for future advances in proxy data and other constraints to be incorporated.
How to cite: Wright, N.: Current state and future directions in paleogeography reconstructions throughout the Cenozoic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15492, https://doi.org/10.5194/egusphere-egu26-15492, 2026.
Dichotomous thinking also known as “black-and-white” and “all-or-nothing” thinking is a common cognitive distortion in which one sees things in absolute extremes without any middle ground. Not only does this bias distort reality and lead to interpersonal conflicts, but it also hinders problem solving. In the Geosciences, this bias is the source of a > 100 years old divide between tectonicists, i.e., early supporters of Continental Drift Theory (e.g., Alfred Wegener, Alexander du Toit), and paleontologists, who argued for (now sunken) land bridges between the continents based on similar fossil records (e.g., Charles Schuchert, John Gregory, Hermann von Ihering, Bailey Willis). Despite explaining the similar fossil record on continents now separated by oceans, Land Bridge Theory implied continental fixity. It was therefore completely abandoned in the 60–70s with the growing body of evidence supporting continent motion. Continental Drift Theory was then fully accepted without any middle ground despite the fossil record suggesting prolonged connection between the continents at specific localities. Possible causes for the black-or-white approach of the Geoscience community include (1) simplicity: easier to envision one hypothesis being right rather than a compromise of both, (2) guilt: Alfred Wegener had died in Greenland in 1931 only to be proven right 30 years later upon acceptance of continent motion, and (3) a feeling of inferiority amongst paleontologists and feeling of superiority (i.e., feeling of inferiority in disguise) amongst tectonicists upon demonstrating continental motion.
Since then, paleontologists have explored new hypotheses to explain the migration of species at times when oceans are believed to have fully separated the continents, e.g., migration of primates from western Africa to South America and of lizards the other way around in the Oligocene. A hypothesis under testing involves floating vegetation islands rafting the species as small groups of individuals across the ocean. This hypothesis implies that enough individuals survived the crossing, i.e., enough food and/or quick journey, and found one another upon landing.
Neither the new hypotheses nor the old ones take into account all the evidence, e.g., microcontinents along major transform faults (e.g., Romanche and St Paul fault zones) and correlation of all former land bridges with major transform faults and rift-oblique orogens on the adjacent margins (e.g., Central African Orogen in western Africa and Sergipano Belt in northeastern Brazil). Orogenic Bridge Theory reconciles these with both continent motion and the fossil record. Orogenic bridges are ribbons of continental crust transected by orogenic structures highly oblique to the active rift. These structures are unsuitably oriented to thin the crust and thus hinder rifting, delay breakup, and control the formation of major transform faults and elongated microcontinents. Orogenic bridges have the potential to form prolonged land connections between the continents while oceanic crustal domains form on either side, thus further allowing the spreading of terrestrial species while hindering that of marine species. This illustrates the need for more multidisciplinary collaboration across the geosciences. Creating a more flexible community that is both inclusive and mindful of diversity is key to enhance collaboration.
How to cite: Koehl, J.-B. and Foulger, G.: Black and white: the bias that shaped plate tectonics and the ongoing > 100 years old divide of the geoscience community, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-507, https://doi.org/10.5194/egusphere-egu26-507, 2026.
Posters virtual: Thu, 7 May, 14:00–18:00 | vPoster spot 2
EGU26-7342 | ECS | Posters virtual | VPS6
Can CO2 outgassing explain Lomagundi Excursion?Thu, 07 May, 14:57–15:00 (CEST) vPoster spot 2
The Lomagundi-Jatuli event (2.3-2.0 Ga) is one of the grandest carbon isotopic (δ13Ccarbonate) excursion events in the Earth’s history, marked by anomalous δ13Ccarbonate reaching up to + 30 ‰. Several hypotheses have been proposed to explain this excursion; however, they remain inadequate due to associated drawbacks. The conventional explanation is organic carbon burial due to enhanced productivity. But, the lack of organic rich stratas synchronous with the excursion demands the reconsideration of alternative biogeochemical processes to explain this isotopic anomaly. Moreover, the excursion is observed only in the evaporitic and nearshore carbonates, with no evidence from open ocean; demanding facies based biogeochemical explanation. Here, we explore the possibility of CO2 outgassing and calcite precipitation as potential drivers responsible for this excursion as these two processes remain the least explored among the proposed hypotheses. Through sedimentological evidences from previous studies and Rayleigh fractionation calculations, we argue that dominant loss of DIC through CO2 outgassing in the evaporitic facies and calcite precipitation in the nearshore facies along with a well-mixed DIC reservoir in the open ocean led to observed Lomagundi Excursion.
How to cite: Janaarthanan, P. A. and Kumar, S.: Can CO2 outgassing explain Lomagundi Excursion?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7342, https://doi.org/10.5194/egusphere-egu26-7342, 2026.
