BG5.4 | Co-evolution of life and the Earth over deep time, and major transitions in Earth's biosphere and environment
EDI

This session aims to bring together a diverse group of scientists who are interested in how life and the planet have co-evolved over geological time. This includes studies of how paleoenvironments have contributed to biological evolution, and also those which focus on the way in which life has altered or regulated Earth’s biogeochemical cycles and climate. As an inherently multi-disciplinary subject, we welcome submissions that explore any period of Earth history and which present new paleoenvironmental, paleobiological or geochemical data or aim to understand our planet and its biosphere through numerical modelling. Part of this session will specifically explore the Ediacaran-Cambrian transition which saw the appearance and diversificaiton of early animals.

Co-organized by SSP4
Convener: Benjamin Mills | Co-conveners: Marjorie Cantine, Fred BowyerECSECS, Khushboo GurungECSECS, Patricia Sanchez-Baracaldo, Alexandre Pohl, Michael Henehan
Orals
| Wed, 26 Apr, 14:00–18:00 (CEST)
 
Room 2.95
Posters on site
| Attendance Wed, 26 Apr, 08:30–10:15 (CEST)
 
Hall A
Posters virtual
| Attendance Wed, 26 Apr, 08:30–10:15 (CEST)
 
vHall BG
Orals |
Wed, 14:00
Wed, 08:30
Wed, 08:30

Orals: Wed, 26 Apr | Room 2.95

Chairperson: Benjamin Mills
Co-evolution of life and the Earth over deep time
5-minute convener introduction
14:00–14:10
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EGU23-9535
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BG5.4
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ECS
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On-site presentation
Jack Longman, Ann Dunlea, Chloe Anderson, and Rachel Scudder

Volcanic ash is known to influence a range of biogeochemical processes once deposited in the oceans. These processes include the fertilisation of phytoplankton, and the enhancement of organic carbon burial, and the impact typically scales with the volume of ash. It has been shown that during periods of intense volcanic ash deposition, the impact on the ocean carbon cycle can be significant enough to cause global cooling. As a result, knowing the volume of ash entering the world’s oceans through time is vital to understanding the role explosive volcanism plays in setting global climate states. However, records of ash deposition consist of a small number of individual archives of ash input estimated via either layer counting or from multivariate statistical partitioning. Here, we compile the discontinuous and patchy records of volcanic ash deposition in the Pacific Ocean over the past 70 million years and synthesise all available data to produce a coherent record of ash accumulation rates. We show how the development of certain provinces, such as the Izu-Bonin Arc led to considerable upticks in ash input, and discuss how changing levels of ash deposition may have impacted Cenozoic climate change. Using a global biogeochemical model, we demonstrate mechanistically the role changing ash supply has in controlling global climate.

How to cite: Longman, J., Dunlea, A., Anderson, C., and Scudder, R.: Reconstructing the input of volcanic ash to the Pacific Ocean over the Cenozoic era, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9535, https://doi.org/10.5194/egusphere-egu23-9535, 2023.

14:10–14:20
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EGU23-8230
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BG5.4
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ECS
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On-site presentation
Die Wen, Junxuan Fan, Norman MacLeod, and Yukun Shi

The pattern of taxonomic richness peaking at the equator and dwindling off towards the Earth’s poles is known as the latitudinal diversity gradient (LDG). It was among the first global biodiversity pattern to be discovered, but is also one that, to date, has resisted comprehensive explanation. The Paleozoic provides a unique perspective to study how the LDG has variated and its form regulated is in the deep time. Here a summary of genus-level global marine invertebrates fossil data was obtained from the Paleobiology Database and used to evaluate LDG patterns for each Paleozoic stage. After data cleaning, this dataset included 485,129 occurrences of 18,234 genera distributed across 85,259 fossil localities. Bias in the observed fossil record, as recorded by these data, was addressed via rarefaction, shareholder quorum subsampling and bootstrap approaches. Pattern analyses of LDG form across Paleozoic stages reveal seven main patterns. Location of latitudinal peak diversity relative to the paleoequator and the steepness of the LDG slopes across latitudes, represent the features that distinguish these seven LDG patterns across Paleozoic time. Although all observed LDG patterns are characterized by a low-latitude richness peak from 30°N to 30°S, they are not symmetrical about the paleoequator in most stages. Comparison of variation in LDG geometries with time-series variation in a suite of environmental proxies suggests that variation in tectonic plate configurations and aspects of global climate change are associated closely with the time-series of LDG variation. These associations suggest that the form of the LDG at different points in earth history was structured by secular changes in global climate states since tectonic configurations would be expected to affect organismal populations primarily through variation in environmental state. Moreover, our results suggest that the current LDG represents a form that is exceptionally balanced – and so somewhat atypical – when compared with LDG forms that existed over much of the Paleozoic.

How to cite: Wen, D., Fan, J., MacLeod, N., and Shi, Y.: Forms and Regulation of the Paleozoic Marine Latitudinal Diversity Gradient, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8230, https://doi.org/10.5194/egusphere-egu23-8230, 2023.

14:20–14:40
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EGU23-9759
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BG5.4
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solicited
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Highlight
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On-site presentation
Carmen García-Comas and Pedro Cermeño

Life originated in the sea about 4 billion years ago and, for the first 3.5 billion years, it was exclusively microscopic. Something happened early in the Cambrian period that made multicellular life to thrive, giving rise to the spectacular biodiversity that has been this planet's hallmark for the past 500 million years. This staggering increase in diversity has raised a fundamental question among evolutionary ecologists: are there limits to the diversity of life? Some scientists say that global diversity increases to an equilibrium point or saturation level that is determined by the system’s carrying capacity. Alternatively, others claim that biodiversity is well below the saturation level and thus we can ignore the existence of any limit. These contrasting views have been fueled by interpretations of the fossil record which is severely biased in space and time. To theoretically test these contrasting views, we have developed a regional diversification model. In the model, we let 1 genus to diversify everywhere in the global ocean from 500 million years ago until present according to a model of paleogeography that constrains the diversification time and a paleo Earth System model that constrains the diversification rate as a function of seawater temperature and food supply. By externally imposing mass extinctions, we explore how the oceans filled with life. The regional model fits surprisingly well global fossil diversity curves and modern biodiversity distributions. According to the model, the ocean is far from saturation except for in the biodiversity hotspots, regions of extraordinarily high levels of diversity, which evolved under prolonged conditions of Earth system stability and maximum continental fragmentation. The model allows us to recreate many things, such as the history of biodiversity hotspots and the dynamics of the latitudinal biodiversity gradient. 

How to cite: García-Comas, C. and Cermeño, P.: INDITEK: A model to understand the emergence of marine biodiversity hotspots in the last 500 million years, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9759, https://doi.org/10.5194/egusphere-egu23-9759, 2023.

14:40–14:50
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EGU23-17419
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BG5.4
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On-site presentation
Christos Chondrogiannis, Richard Nair, William Matthaeus, Kamila Kwasniewska, Katie O’Dea, Catarina Barbosa, Antonietta Knettge, Bea Jackson, and Jennifer McElwain

Plants respond to environmental change but also impact the Earth system by altering biogeochemical fluxes. Plants and their distribution have also changed profoundly across deep time as major evolutionary groups have evolved, prospered or declined. However, the current representation of this change in models is simplistic. For example, a simple succession of biogeochemical impacts along with evolution of major plant groups (i.e.,sporophytes, gymnosperm, and angiosperms) is assumed through eras of deep time, whereas major plant innovations are known to have evolved through appearance of novel combinations of traits that show variation within these lineages.

In the TERRAFORM project we are integrating trait ecology of extinct plants, state-of-the-art weathering experiments, and multi-scale modeling to study the terrestrial biosphere’s impact on the carbon, nutrient and hydrological cycles in deep-time. We focus on the effects of evolution of plant traits on chemical weathering and the global silicate cycle and how it varies over time, we hope to track how plants have impacted major episodes of biosphere upheaval. Pursuant to that focus, we perform palaeo-Earth weathering and decomposition experiments to understand the difference in effect of plant evolutionary groups and their traits on  biogeochemical fluxes. We apply these empirical insights to plant fossils spanning episodes of major environmental change (Pennsylvanian-Permian glacial interglacial cycles; the Triassic-Jurassic mass extinction; Cretaceous OAEs) to evaluate the impact of environmental change on extinct plants and their traits. This knowledge will improve the chemical weathering and terrestrial ecosystem parameterization and performance of biogeochemical models, to evaluate the plant feedback on other components of the earth system. Ultimately we aim to understand how plants TERRAFORMed the Earth, and how plant functional traits and function evolved over the past 300 million years.

How to cite: Chondrogiannis, C., Nair, R., Matthaeus, W., Kwasniewska, K., O’Dea, K., Barbosa, C., Knettge, A., Jackson, B., and McElwain, J.: TERRAFORM: Trait Ecology and Biogeochemical Cycles in Deep Time, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17419, https://doi.org/10.5194/egusphere-egu23-17419, 2023.

14:50–15:00
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EGU23-13901
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BG5.4
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On-site presentation
Georg Feulner, Tais W. Dahl, Magnus A.R. Harding, Julia Brugger, Kion Norrman, Barry H. Lomax, and Christopher K. Junium

Traditionally, the evolution of trees and the establishment of the first forests during the Devonian (419–359 Ma) have been linked to an enhancement of terrestrial weathering processes and a subsequent reduction of atmospheric carbon dioxide (CO2) levels by one order of magnitude. However, empirical estimates of early-Devonian CO2 concentrations are sparse and carry large error bars. Here we use leaf carbon isotopes, stomata density, and stomata pore length from fossilized lycophytes to estimate atmospheric CO2 levels 410–380Ma based on a mechanistic model for gas exchange calibrated using their closest modern lycophyte relatives. We find that Earth's atmosphere contained about 525–715 ppm of CO2 before the emergence of forested ecosystems, much less than previously thought. Using a coupled climate model, we show that Earth was partially glaciated at these moderate CO2 levels and that this cool climate state is in principle agreement with available climate proxies and fossil evidence for the distribution terrestrial vegetation. Finally, we use a process-based biogeochemical model to demonstrate that our results are consistent with a scenario in which enhanced weathering, climate cooling, and atmospheric oxygenation are associated with the earlier emergence of shallow-rooted vascular ecosystems rather than the appearance of the first forests.

How to cite: Feulner, G., Dahl, T. W., Harding, M. A. R., Brugger, J., Norrman, K., Lomax, B. H., and Junium, C. K.: New proxy estimates reveal low atmospheric CO2 levels before the emergence of forested ecosystems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13901, https://doi.org/10.5194/egusphere-egu23-13901, 2023.

15:00–15:10
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EGU23-14439
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BG5.4
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ECS
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On-site presentation
Elizabeth Dowding, Nikolay Akulov, and Irina Mashchuk

Devonian plants in Siberia present protracted pioneer succession. During the Devonian Angarida was a large and semi-isolated continent within warm, arid zones of the northern hemisphere. Early plants in the Devonian did not originate upon Angarida, instead they are known to migrate to Angarida allowing a unique opportunity to study their changing biogeography and their influence upon the virgin landmass. In the Late Devonian, the Viluy-Yakutsk Large Igneous Province had two active phases and dramatically altered the physical and chemical environment of both the early plants and the marine systems. Our research into the survivourship dynamics of early plant communities upon the palaeocontinent Angarida have demonstrated that transgression and volcanogenic nutrient influx were key to the survival of colonising plants. Taxic proportions show that migrating taxa entered Angarida from the southwest, Kuznetsk and Minusinsk basins, dispersing across the continent in waves through central areas northwards. The patterns of dispersal are consistent throughout the Devonian and into the Early Carboniferous. Increased nutrient load from the active pulses of the Viluy-Yakutsk Large Igneous Province, biogeomorphic ecosystem engineering, and the increased biomass of Angaridan plants are assisted by Late Devonian transgression. These cumulative factors can be linked to the Late Devonian marine extinctions observed in Siberia.

How to cite: Dowding, E., Akulov, N., and Mashchuk, I.: Early Plant responses to Large Igneous Province Activity: the Devonian of Angarida, Siberia., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14439, https://doi.org/10.5194/egusphere-egu23-14439, 2023.

15:10–15:20
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EGU23-7156
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BG5.4
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ECS
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On-site presentation
Valters Alksnitis

The Upper Devonian deposits of Latvia are rich in fossil vertebrate remains that have been studied for several decades. Attention to pathologies in these remains has been given only recently.

The paleontological record of parasitic behaviour is quite incomplete, particularly regarding the parasites of vertebrates. Although fossil remains of parasitic organisms are very rare, traces of their action and parasite-induced pathologies can be found more often even though these are hard to identify and it is even more complicated to determine what was the organism that left the traces. Various skeletal pathologies from Middle (Givetian) to Upper Devonian (Frasnian, Famennian) fishes from Latvia, Estonia and Western Russia were attributed to attacks of parasites (Lukševičs et al. 2009) and predators (Lebedev et al. 2009). The pathologies caused by parasite action described by Lukševičs et al. 2009 include round and oval fossulae, swellings, variously shaped attachment buttresses, openings on various skeletal elements of fishes, and porous spongy formations found on the non-overlapped surface of the scales of porolepiform sarcopterygians. These pathologies were explained as caused by cestode and trematode infestations, attacks of parasites similar to copepod crustaceans, by activity of pathogenic fungi, bacteria, protozoans or algae. Bite marks on skeletal parts of placoderm antiarchs and arthrodires, sarcopterygian porolepiforms and osteolepiforms, and agnathan pteraspidiforms and psammosteiforms were also reported (Lebedev et al. 2009).

Subsequent excavations from 2018-2020 have provided new paleontological material. The paleontological material from the field work and collection of the Museum of University of Latvia has been studied. Pathologies have been found in porolepiform holoptichiid Holoptychius sp. and Ventalepis ketleriensis scales, osteolepiform Cryptolepis grossi scales from the Upper Devonian Tērvete and Ketleri Formations, antiarch bothriolepid Bothriolepis ciecere from the Ketleri Formation and B. ornata armour plates from the Tērvete Formation. Most common pathologies are regular pits on the overlapped and non-overlapped sarcopterygian scale surface similar to those described earlier. Thin sections and CT scans  that have been carried out for the first time confirm that they were formed during animal life. Shallow pits have also been found on the surface of the placoderm armour plates usually close to plate boundaries. Small drill holes on the placoderm armour plates and sarcopterygian scales, in one case connected with a swelling within the scale, might indicate endoparasite activity. Predator bite marks have also been found on the bones both as lifetime damage traces, in some cases accompanied by pathological regrowth of the bone element, as well as post-mortem scratches and marks. Some of the scales and the armour plates also exhibit lesions of unspecific shape on the bone surface, exact cause of these is currently unclear. Difficulties in interpreting the exact cause of the pathologies still should not disencourage further research.

How to cite: Alksnitis, V.: Pathologies in the fish fossils from the Upper Devonian, Famennian deposits of Latvia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7156, https://doi.org/10.5194/egusphere-egu23-7156, 2023.

15:20–15:30
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EGU23-5323
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BG5.4
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On-site presentation
Laurent Husson, Tristan Salles, Manon Lorcery, and Beatriz Hadler Boggiani
 

The contrasted diversification of marine and terrestrial life remains enigmatic. The monotonic expansion of species on continents started later in the early Phanerozoic than in the marine realm, where instead the number of genera waxed and waned. Only a comprehensive evaluation of the changes in the physical environment can provide a unified theory for the long-term pattern of evolution of life on Earth. We developed a numerical model to reconstruct the evolution of the physiography at global scale and high resolution over the entire Phanerozoic eon, accounting for plate tectonics and climatic forcings.

Our results point at landscape dynamics as a limiting factor both in lands and oceans, mostly by erosion and sediment transport. Marine diversity was strongly limited by the oscillating bulk riverine sedimentary fluxes that provide nutrients, while the expansion of land plants was hampered until widespread endorheic basins resurfaced continents with a sedimentary cover that facilitated the development of soil-dependent rooted plants. In both realms, landscape dynamics determine the carrying capacity of the environment.

How to cite: Husson, L., Salles, T., Lorcery, M., and Hadler Boggiani, B.: Global physiography dynamics controled the Phanerozoic diversification of the biosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5323, https://doi.org/10.5194/egusphere-egu23-5323, 2023.

15:30–15:40
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EGU23-14217
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BG5.4
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On-site presentation
Axel Gerdes, Marjorie Cantine, and Sören Eitel

Aim: Using geochemical proxies to record changes in environmental conditions during the Ediacaran-Cambrian time

Methods: Thin section petrography combined with high-resolution analyses of trace elements and U-Pb, Sr, B and Li isotopes by LA-ICPMS (single and multi-collector)

Problem: Identification of pristine early diagenetic carbonate phases and their distinction from late diagenetic and altered carbonates. 

In this study, we use high spatial resolution multi-element and isotope analyses to identify pristine carbonate phases in samples from recent drill cores from Namibia, drilled by International Continental Scientific Drilling Program project GRIND-ECT. GRIND-ECT aims to capture, in drill core, the Ediacaran-Cambrian transition in key successions worldwide.

The method applied allows for relatively high sample throughput (>200) and precise detection of heterogeneous altered domains. Exclusion criteria are the presence or increased concentration of various trace elements (Al, Rb, LREE ...), heterogeneity of the 87Sr/86Sr isotope ratio, a lack of discernible populations in U/Pb isotope space, resulting in non-correlated scattering, and too young U-Pb dates.

To date, about 10-15% of the samples analyzed yielded a U-Pb date consistent with depositional age or an early post-depositional age. Geochronologic control of ancient sedimentary sequences is critical for evaluating cause and effect and rates of change in ancient environments. However, precision of LA-ICPMS ages (ca. 1-2%, e.g., 6-11 Ma) is insufficient to resolve changes in the Ediacaran-Cambrian oceans on timescales relevant for biological and environmental change. Therefore, the ages of these pre-characterized samples need to be refined using high-precision methods (Cantine et al., EGU 2023).

Analyses of Li and B isotopes are in progress on the pre-characterized, potentially pristine carbonate areas. We expect to see a change in the Li, B and Sr isotope records through Ediacaran-Cambrian time hopefully with significant anomalies. The correlation of the three isotope systems would be a confirmation for us that we are targeting pristine, early diagenetic carbonates.

How to cite: Gerdes, A., Cantine, M., and Eitel, S.: Ancient carbonates as archives for global environmental changes during Ediacaran-Cambrian time: a geochemical perspective, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14217, https://doi.org/10.5194/egusphere-egu23-14217, 2023.

15:40–15:45
Coffee break
Chairperson: Fred Bowyer
Integrating Ediacaran to Cambrian Environments across outcrop and drill core
16:15–16:20
16:20–16:30
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EGU23-4776
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BG5.4
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On-site presentation
Zekun Meng, Xiqiang Zhou, Zhenfei Wang, Pengcheng Ju, and Kangjun Huang

The Marinoan Snowball Earth event marks a critical time in Earth’s history, with significant climate change characterized by low-latitude glaciation. The ocean is hypothesized to be anoxic during the Marinoan glaciation (ca. 649 to 635 Ma). However, this hypothesis is contradicted with global marine red beds (MRB) deposited in the Marinoan glaciation and diversification of complex eukaryotes after the termination of the Marinoan. To better comprehend the redox conditions of the late Cryogenian seawater, we present systematic sedimentological, mineralogical (SEM), and Fe geochemical analyses (Fe isotope and Fe speciation) of the MRB from the Nantuo Formation in South China.

Two continuous ice advance-retreat cycles in the Nantuo Formation are separated by a MRB sequence, indicating an interglacial period with limited influence from glaciation. The results of Fe speciation show that the predominant phase of FeHR (highly reactive Fe) is Fe-oxide with extremely low content of Fe-pyrite and Fe-carbonate of the Nantuo Formation. Furthermore, well-preserved and nanometer-sized hematite (Fe-oxide) particles randomly dispersed in the matrix, suggesting that Fe(II) oxidation occurred in the water column rather than in the sediments. High FeHR/FeT ratios and near-zero δ56FeHR values of the MRB suggest scavenging of dissolved Fe(II) by quantitative oxidation at the basal of the Nantuo Formation. A positive δ56FeHR shift above the MRB further reflects the partial oxidation of Fe(II) to Fe(III) in the water column. These suggest sufficient oxygen derived from meltwater and/or atmosphere during the inter-glacial episode, facilitating the deposition of MRB. The oceanic redox conditions switch to anoxic in response to the re-appearance of the second glacial episode. Our findings suggest that the dynamic redox state of seawater was likely controlled by ice-sheet advancing-retreating cycles and provide new insight into redox conditions during the end-Cryogenian Marinoan glaciation.

How to cite: Meng, Z., Zhou, X., Wang, Z., Ju, P., and Huang, K.: Marine redox fluctuation during the Marinoan Snowball Earth: evidence from red beds of the Nantuo Formation in South China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4776, https://doi.org/10.5194/egusphere-egu23-4776, 2023.

16:30–16:40
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EGU23-3852
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BG5.4
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ECS
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Virtual presentation
Zhi-Ping Zhong, Yueh-Fen Li, Mary Davis, James Van Etten, Ellen Mosley-Thompson, Matthew Sullivan, Virginia Rich, and Lonnie Thompson

Glacier-archived records are powerful windows into past climates and ecosystems, but variation in co-preserved microbiota is rarely characterized over long time periods or connected to changing climates. In a 310-meter ice core from the Guliya ice cap, Tibetan Plateau, we linked microbial communities to concomitant climatic conditions across 33 depths, spanning at least the last 150,000 years. Communities differed significantly between cold and warm periods, and among the three major climate epochs Holocene, Last Glacial Stage (LGS), and Pre-LGS. Although source inputs varied during these periods, the microbial changes appeared independently impacted by climate as well. Co-occurrence network analyses suggested the importance of glacial surface-growing communities, and their phototrophs, to the preserved microbial record. The inferred microbial growth (by cell densities, diversity, and potential doubling times pre-compaction into solid ice) on Guliya’s surfaces was higher during cold periods than warm periods, likely associated with deeper snow and firn layers under colder conditions. Three Cyanobacteria “blooms” were captured in the record, and were significantly correlated to overall microbial concentration and diversity, as well as the abundance of two heterotrophic photosynthetic clades (the genus Geodermatophilus and the class Chloroflexia). Taxonomically, 6 genera were historically persistent and dominant throughout the record (Polaromonas, Flavobacterium, Massilia, Aquaspirillum, Pedobacter, and Cryobacterium), one of which (Cryobacterium) exhibited a shift in dominant strains from the Pre-LGS to the LGS, indicating a possible speciation event. Collectively, these findings advance our understanding of ancient glacier-archived microbial communities and the ecological forces they experienced, provide evidence for microbiological responses to the prevailing climate regime, and may shed new light on the microbial evolution across a long-term history over at least the last >150,000 years.

How to cite: Zhong, Z.-P., Li, Y.-F., Davis, M., Van Etten, J., Mosley-Thompson, E., Sullivan, M., Rich, V., and Thompson, L.: Microbial communities differ in warm and cold periods over >150,000 years, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3852, https://doi.org/10.5194/egusphere-egu23-3852, 2023.

16:40–16:50
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EGU23-9234
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BG5.4
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On-site presentation
Maria Ovtcharova, Andrey Ivantsov, Aleksey Nagovitsyn, Maria Zakrevskaya, Ulf Linnemann, Anna Ivleva, and Viktoria Ershova

Establishing an absolute timeline for the evolution of Ediacaran (latest Neoproterozoic) biota is an outstanding challenge for the geochronology community. Ediacaran biota (“Vendian” in Russian literature; 580-539 Ma) is traditionally divided into three assemblages: Avalon, White Sea and Nama, considered as a partially overlapping evolutionary and temporal successions. The geochronological record of the White Sea assemblage is hampered by the lack of datable volcanic beds, with very few exceptions like in Onega peninsula and along the Winter coast in northwestern Russia. There, we find examples of the most complete and diversified White Sea assemblage of the entire East European Patform (EEP).

We report here results from a field study and U-Pb geochronology on the Lyamtsa and Verkhovka formations from Onega peninsula (Lyamtsa and Agma rivers) and Zimnie Gori formation along the Winter coast. The studied sedimentary successions consist mainly of fine-grained sandstone, mudstone and claystone, reflecting shallow marine conditions, influenced by a large river delta. The base of the White Sea Ediacaran deposits starts with sandstones and conglomerates, overlain by the brown clay with volcanic tuff (only in drillcore) in the base of the Lyamtsa formation, which contain  first simple horizontal trace fossils, worm tubes Calyprtina and cyanobacterial colonies Beltanelloides, predating the onset of the rich Ediacaran fossil assemblage. In the middle part of the Lyamtsa formation (accessible in outcrops) the first Dickinsonia, Parvancorina and Aspidella fossils are found, as well as the oldest trace fossils of arthropods Cruzianа, vertical burrows Altichnus and traces of polychaete-like worms, previously known only from the uppermost Edicaran and Cambrian. The full range of diverse Ediacaran fossils (e.g., various dickinsoniids, trilobozoans, Kimberella, Charnia, Rangea, Pteridinium, etc.) is reached further up in the section (Verkhovka, Zimnie Gori and Erga formations).

We have sampled two ash layers from the base of Verkhovka formation (Agma river) and one from the base of Zimnie Gori formation (along the Winter coast). Our high precision U-Pb zircon CA-ID-TIMS age determinations yielded weighted mean 206Pb/238U dates of 555.7 ± 0.6 Ma and 555.1 ± 0.7 Ma for the two ash layers of the Verkhovka formation and 552.6 ± 0.6 Ma for the base of Zimnie Gori formation. Applying age depth model calculations we can estimate that the onset of the Ediacaran White Sea assemblage in Lyamtsa formation must be older than 561 Ma. These results, combined with the age of the top of Zimnie Gori formation (550 ± 5 Ma, Llianos et al., 2005) have important implications for: i) estimate of the evolutionary trend of Ediacaran White Sea assemblage or at least for some Ediacaran organisms, which are showing philogenetic evolution (for examle Dickinsonia); ii) better correlations between distribution of Ediacaran macrofossils in the sedimentary sequences of the Eastern and Northeastern part of the EEP.

 

 

REFERENCES

 

Llanos, M.P.I., Tait J.A., Popov, V. & A. Abalmassova (2005) Palaeomagnetic data from Ediacaran (Vendian) sediments of the Arkhangelsk region, NW Russia: An alternative apparent polar wander path of Baltica for the Late Proterozoic–Early Palaeozoic. Earth and Planetary Science Letters 240, 732–747.

How to cite: Ovtcharova, M., Ivantsov, A., Nagovitsyn, A., Zakrevskaya, M., Linnemann, U., Ivleva, A., and Ershova, V.: U-Pb zircon ID-TIMS geochronology of the Ediacaran White Sea assemblage from Onega peninsula, NW Russia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9234, https://doi.org/10.5194/egusphere-egu23-9234, 2023.

16:50–17:00
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EGU23-11907
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BG5.4
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ECS
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On-site presentation
Gustavo Paula-Santos, Simone Kasemann, Fred Bowyer, Ricardo Trindade, Marly Babinski, Rachel Wood, and Juliana Leme

The Kuibis Subgroup (~551- <547.36 Ma) in the Nama Basin records an important fauna assemblage change during the Ediacaran. Current models support a transition from a more diverse ‘White Sea’ biotic assemblage to a less diverse ‘Nama’ biotic assemblage, for which the drivers remain unresolved. In spite of this decrease in diversity, the Nama assemblage hosts the first appearance of metazoan biomineralization in the geologic record. High resolution chemostratigraphic data are required to globally anchor the timeline of Earth System changes leading to this innovation of life. In order to track these changes at high-resolution, we performed a sampling campaign of Namibian cores from the ICDP project ‘Geological Research through Integrated Neoproterozoic Drilling: The Ediacaran-Cambrian Transition’ (GRIND-ECT), which focuses on terminal Ediacaran stratigraphy of the Witputs and Vioolsdrif sub-basins of southern Namibia. Here we present new Carbon and Oxygen isotope data for carbonate rocks of the Kuibis Subgroup retrieved from drill core 1G. This core records an approximately 200 m-thick succession of mixed carbonate-siliciclastic sedimentary rocks of that unit. Both dolostones and limestones within the lowermost 100 m display negative δ13C values between -5 and 0 ‰, consistent with laterally-correlative outcrop data that record the Basal Nama Excursion (BANE). The oxygen isotope profile recorded in core 1G is also very distinctive throughout the BANE. It starts with a negative shift of the δ18O values from -5 to -15 ‰, which then progressively increase to values around -12 ‰. The uppermost 100 m of core 1G display a gradual increase in δ13C values that reach +5 ‰ and are accompanied by increasing δ18O values that approach -10 ‰. The 0 ‰ crossing point (carbon isotope value) occurs at ~90 m depth, below strata that confidently record the first appearance of fossils of biomineralizing animals. Magnesium isotopic and paleontological data added to our high-resolution carbon isotope profile have the potential to refine the knowledge about the biological and environmental changes of this time period. 

How to cite: Paula-Santos, G., Kasemann, S., Bowyer, F., Trindade, R., Babinski, M., Wood, R., and Leme, J.: High-resolution carbon, oxygen and magnesium isotope chemostratigraphy of the Kuibis Subgroup, Nama Basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11907, https://doi.org/10.5194/egusphere-egu23-11907, 2023.

17:00–17:10
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EGU23-12181
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BG5.4
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ECS
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On-site presentation
Late Ediacaran macrofossils in storm and debris flow deposits reveal the allochthonous nature of many Ediacaran palaeocommunities from the Nama Group, Namibia
(withdrawn)
Brennan O'Connell, William McMahon, and Alex Liu
17:10–17:20
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EGU23-15489
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BG5.4
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ECS
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On-site presentation
Mariana Yilales, Fred Bowyer, Rachel Wood, and Simon Poulton

The marine carbon isotope record (δ13C) used for chemostratigraphy and reconstruction of carbon cycle dynamics is constructed using carbonate rocks, but there is evidence that carbonate cements hosted within fine-grained clastics (shales and mudstones) in some settings may also express δ13C trends that covary with the record from carbonates. We present new carbon and oxygen isotopic data from shale-hosted carbonate cements (δ13Ccarb-sh and δ18Ocarb-sh, n = 107, <16 wt% CaCO3) of the terminal Ediacaran Nama Group, Namibia (≥550.5 to <539.6 Million years ago; Ma). These data are compared with the published carbon and oxygen isotopic record from coeval carbonates (δ13Ccarb and δ18Ocarb, n = 1611) and total organic carbon (TOC) concentrations. We show that δ13Ccarb-sh compositions in samples of intermediate to high CaCO3/TOC can approximate contemporaneous δ13Ccarb in open marine mixed carbonate-clastic settings. By contrast, δ13Ccarb-sh values in samples with low CaCO3/TOC that were deposited in clastic settings distant from the locus of carbonate deposition are more negative than contemporaneous δ13Ccarb. These data suggest that δ13Ccarb-sh may approach seawater composition in samples of low TOC when deposited in high dissolved inorganic carbon (DIC) settings, where carbonate can rapidly precipitate from seawater during early diagenesis. However, the use of δ13Ccarb-sh to infill gaps in the existing δ13Ccarb record remains uncertain, even when these criteria are fulfilled. Intervals of δ13C-δ18O co-variability in the Nama Group succession appear to correlate with units where seawater mixing with meteoric fluids was more likely during early diagenesis, such as clastic-dominated settings, which also show significant decreasing δ18O through time with gradual sub-basin infill.We further consider uncertainties in lithostratigraphic correlation of the upper Urusis Formation of the Nama Group that enable three new possible correlations to be proposed for δ13Ccarb-sh data within the terminal Ediacaran to lower Cambrian (<542.65 Ma to >535 Ma) regional and global δ13Ccarb records.

How to cite: Yilales, M., Bowyer, F., Wood, R., and Poulton, S.: Insights into the terminal Ediacaran marine carbonate record from shale-hosted carbonate carbon isotopes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15489, https://doi.org/10.5194/egusphere-egu23-15489, 2023.

17:20–17:30
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EGU23-16040
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BG5.4
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ECS
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On-site presentation
Heda Agic, Martin Smith, and Alex Kovalick

The early evolution of macroscopic life, including the Cambrian ‘explosion’ of animals, took place over more than 100 million years against the backdrop of dynamic environmental changes like unstable redox conditions and nutrient supply. The terminal Ediacaran to early Cambrian transition is marked by the appearance of macroscopic biomineralizers, but also a seeming decline in diversity, in contrast to rich communities of macroscopic Ediacara-type biota preserved in older units worldwide. Our understanding of this biotic change as well as its environmental divers suffers from stratigraphic incompleteness, as continuous mid and upper Ediacaran, and Cambrian strata are rarely exposed in a continuous sequence in the same area, or represent different depositional settings.

The Mackenzie Mountains in the Northwest Territories, Canada are a home to a nearly continuous sedimentary succession from the Cryogenian to the Cambrian and as such, provide a great target to analyse biotic and environmental changes through time. We have investigated the interval of carbonates and siliciclastics through the Blueflower, Risky, Ingta, Backbone, and Vampire formations and present integrated palaeontological and geochemical data to produce a high resolution biostratigraphic and chemostratigraphic profile for the Ediacaran-Cambrian boundary interval.

The Ediacaran-Cambrian boundary occurs in the Ingta Formation, marked by sporadic trace fossils Treptichnus and Harlaniella. Simple surficial traces Planolites occur throughout the formation. Also common are well-preserved bacterial filamentous organic-walled microfossils in mudrocks, but the boundary interval lacks complex acritarchs or cuticular animal remains. Macroscopic carbonaceous fossil problematica were also recovered. Complex trace fossils occur in the overlying Backbone Ranges Formation and become more common in the Vampire Formation, but are absent from the lowermost Cambrian strata in the Mackenzie Mountains. The primary producer dominated environment and the absence of organically preserved animal remains in a setting conducive to organic preservation imply a true decline in diversity through the boundary interval – possibly a result of either phylogeny or ecology.

How to cite: Agic, H., Smith, M., and Kovalick, A.: Primary producer dominated environments of the Ediacaran-Cambrian transition: palaeontological insights from the Mackenzie Mountains, Canada, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16040, https://doi.org/10.5194/egusphere-egu23-16040, 2023.

17:30–17:40
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EGU23-5782
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BG5.4
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solicited
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On-site presentation
Timothy Topper, Marissa Betts, Dorj Dorjnamjaaa, Guoxiang Li, Luoyang Li, Gundsambuu Altanshagai, Baktuyag Enhkbaatar, and Christian Skovsted

Global Boundary Stratotype Section and Points (GSSP’s) are often regarded as immutable points, that once ratified should “remain fixed in spite of discoveries stratigraphically above and/or below” (Cowie, 1986, p. 79). The Precambrian–Cambrian boundary, defined at Fortune Head by the FAD of the trace fossil Treptichnus pedum, has been a source of controversy and debate since its ratification. Treptichnus pedum has proven to be a difficult marker to apply to global correlation, and lack of other markers at Fortune Head (skeletal fossils, chemostratigraphic, magnetostratigraphic or radiometric data) has prompted the use of other “unofficial” indicators of the Precambrian–Cambrian boundary in many sections around the world. δ13C chemostratigraphy has become a standard global correlation tool, and the integration of δ13C isotopes with other “multi-proxy” data is an approach that is becoming increasingly adopted. Discoveries and advances in such methods and techniques demonstrate that new data can (and should) enable the fine-tuning of stratigraphic boundaries. Recent work in southwestern Mongolia through the Precambrian–Cambrian boundary section at Bayan Gol demonstrates the utility of multi-proxy stratigraphic data to defining and correlating the base of the Cambrian. Here, two proxies are used in concert to identify the Precambrian–Cambrian boundary; the first occurrence of the small shelly fossil Protohertzina anabarica and the nadir of the BACE (δ13C excursion). This section demonstrates 1) the value of carbonates in their capacity to preserve a wider variety of stratigraphic proxies than siliciclastics, 2) the importance of systematically measured and sampled stratigraphic sections (rather than composite sections) for regional and global correlation and 3) the need for a redefined Cambrian GSSP, with a supporting ASSP as a pathway toward global correlation of the base of the Cambrian.

How to cite: Topper, T., Betts, M., Dorjnamjaaa, D., Li, G., Li, L., Altanshagai, G., Enhkbaatar, B., and Skovsted, C.: Two out of three ain’t bad: Dealing with proxy paucity when correlating the base of the Cambrian, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5782, https://doi.org/10.5194/egusphere-egu23-5782, 2023.

17:40–17:50
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EGU23-16572
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BG5.4
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ECS
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On-site presentation
Kilian Eichenseer, Matthias Sinnesael, Martin R. Smith, and Andrew R. Millard

Trilobites are the most diverse animal phylum in the Cambrian, and are critical stratigraphic markers. Despite their significance, the exact sequence of trilobite appearances across the globe, and their respective ages, are difficult to reconstruct due to a scarcity of radiometric dates. Using visual correlation of carbon isotope (δ13C) excursions and integration of available U-Pb age constraints, Landing et al. (2021) have estimated the age of the first Siberian trilobites at roughly 521 million years ago (Ma), which would make them the world’s oldest trilobites. Here, we aim to provide a more precise date, with uncertainty, using a Bayesian stratigraphic age model that takes the global signature of δ13C excursions to correlate proxy records from multiple locations. Our model integrates radiometric dates across sections, using ages from well-dated sections to inform age estimates in sections with little or no age information. The model works by evaluating the fit of Bayesian splines to different alignments of the sections, using Markov chain Monte Carlo methods to obtain the posterior distributions. This approach provides an objective evaluation of different possible alignments, generating a probabilistic age-depth model. We apply this model to the lower Cambrian sections of the Anti-Atlas mountains in Morocco, and to the Sukharikha River section of the northwestern Siberian platform. The Moroccan sections provide a uniquely detailed δ13C record and multiple radiometric dates, and this age information is transferred to the Siberian section and the emergence of trilobites in the fossil record. Preliminary results indicate that the first appearance of Siberian trilobites is younger than previously estimated, and consequently closer in time to the first trilobites in Morocco and elsewhere.

Landing, E., Schmitz, M., Geyer, G., Trayler, R., & Bowring, S. (2021). Precise early Cambrian U–Pb zircon dates bracket the oldest trilobites and archaeocyaths in Moroccan West Gondwana. Geological Magazine, 158(2), 219-238.

How to cite: Eichenseer, K., Sinnesael, M., Smith, M. R., and Millard, A. R.: Dating the first Siberian trilobites with a Bayesian, stratigraphic age model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16572, https://doi.org/10.5194/egusphere-egu23-16572, 2023.

17:50–18:00
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EGU23-6317
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BG5.4
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Highlight
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On-site presentation
Rachel Wood, Andrey Zhuravlev, Emily Mitchell, Frederick Bowyer, and Amelia Penny

Oxygenation during the Cambrian Radiation progressed via a series of short-lived pulses. However, the metazoan biotic response to this episodic oxygenation (and potentially productivity changes) has not been quantified, nor have the causal evolutionary processes been constrained. Here we present analyses of the dynamics of early Cambrian metazoan body size changes, habitat distribution, and ecological complexity on the Siberian Platform (525–510 Ma).

First, we quantify high-resolution changes in species body size in archaeocyath sponges, hyolith lophophorates, and helcionelloid molluscs, and brachiopods. Archaeocyath, hyoliths, and helcionelloids, show dynamic and synchronous trends over million-year timescales, with peaks in body size during the latest Tommotian/early Atdabanian (~521–519 Ma) and late Atdabanian/early Botoman (~519–516.5 Ma), and notably small body sizes in the middle Atdabanian and after the Sinsk anoxic extinction event, starting ca. 513 Ma. These intervals of body size changes are also mirrored in individual species and correlate positively with increased rates of origination and broadly with total species diversity. Calcitic brachiopods (rhynchonelliformeans), however, show a general increase in body size following the increase in species diversity through this interval; phosphatic brachiopods (linguliformeans) show a body size decrease that negatively correlates with diversity. Both brachiopod groups show a rapid recovery at the Sinsk Event. The synchronous changes in these metrics in archaeocyaths, hyoliths and helcionelloids suggest the operation of external drivers through the early Cambrian, coincident with two oxic or productivity pulses. But the trends shown by brachiopods suggests a differing physiological response. Together, these dynamics created both the distinct evolutionary record of metazoan groups during the Cambrian Explosion and determined the nature of its termination.

Second, during the oxic pulse at ~521–519 Ma, we quantify the expansion of archaeocyath sponge reef habitat coupled to an increase in reef size and metacommunity complexity, from individual within-community reactions to their local environment, to ecologically complex synchronous community-wide response, accompanied by an increase in rates of origination. Subsequently, reef and archaeocyath body size are reduced in association with increased rates of extinction due to inferred expanded marine anoxia (~519–516.5 Ma). The later oxic pulse at ~515 Ma shows further reef habitat expansion, increased archaeocyath body size and diversity, but weaker community-wide environmental responses.

These metrics confirm that oxygenation events created temporary pulses of evolutionary diversification and enhanced ecosystem complexity, potentially via the expansion of habitable space, and increased archaeocyath individual and reef longevity in turn leading to niche differentiation. Most notably, we show that progression towards increasing biodiversity and ecosystem complexity was episodic and discontinuous, rather than linear, during the Cambrian Radiation.

 

How to cite: Wood, R., Zhuravlev, A., Mitchell, E., Bowyer, F., and Penny, A.: Biotic responses to oxygenation pulses during the Cambrian Radiation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6317, https://doi.org/10.5194/egusphere-egu23-6317, 2023.

Posters on site: Wed, 26 Apr, 08:30–10:15 | Hall A

Chairperson: Benjamin Mills
A.270
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EGU23-15364
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BG5.4
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ECS
Fred Bowyer, Alexander Krause, Yafang Song, Kang-Jun Huang, Yong Fu, Bing Shen, Jin Li, Xiang-Kun Zhu, Michael Kipp, Lennart van Maldegem, Jochen Brocks, Graham Shields, Guillaume Le Hir, Benjamin Mills, and Simon Poulton

     The Cryogenian Period (720–635 Million years ago, Ma) hosts sedimentary and geochronological evidence for two long-lived global-scale glaciations during the Sturtian (ca. 717–660 Ma) and Marinoan (ca. 650–635 Ma) cryochrons. Radiometric and chemostratigraphic data, in addition to climate modelling, support an approximately synchronous global deglaciation from the Sturtian cryochron, followed by a non-glacial interval (ca. 660–650 Ma) with abundant globally-distributed marine sedimentary successions. The palaeontological record of Cryogenian non-glacial successions is dominated by microfossils and problematic macrofossils, some of which have been interpreted as possible sponge-grade organisms. Biomarker analyses also hint at the rise to dominance of green algae and the possible first appearance of demospongiae during this interval. Oxygen and nutrient availability can fuel biotic complexity, however Cryogenian non-glacial palaeoredox and palaeonutrient (e.g. phosphorus, P) dynamics are poorly understood. Furthermore, while regional lithostratigraphic and chemostratigraphic correlations of carbonate-dominated Cryogenian non-glacial sedimentary successions are well documented, the temporal calibration of globally distributed carbonate and siliciclastic successions has not been attempted. Without a global chronostratigraphic age framework, the regional versus global nature of geochemical responses to Earth System perturbations and the sequence of biotic events throughout this interval remain obscured.

     Here we present new high resolution palaeoredox and P phase association data from five globally distributed Cryogenian non-glacial drill core successions. The combination of Fe speciation and trace element palaeoredox reconstructions with P speciation data clearly show dynamic changes to bioavailable P recycling in response to local and global scale nutrient-driven palaeomarine redox conditions. We also present a new global Cryogenian non-glacial chronostratigraphic framework for the calibration, in relative time, of geochemical and palaeontological data from carbonate and siliciclastic-dominated successions. This enables our new data to be interpreted in the context of the highly dynamic global C and S cycles and biotic record throughout this interval. This approach, in combination with new insights from climate models that constrain changes to atmospheric CO2 and temperature, sheds new light on the mechanisms for global changes to ocean redox and nutrients, and possible drivers for a possible increase in biotic diversity throughout this interval.

How to cite: Bowyer, F., Krause, A., Song, Y., Huang, K.-J., Fu, Y., Shen, B., Li, J., Zhu, X.-K., Kipp, M., van Maldegem, L., Brocks, J., Shields, G., Le Hir, G., Mills, B., and Poulton, S.: Environmental stabilisation and biological diversification in the aftermath of the Sturtian Snowball glaciation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15364, https://doi.org/10.5194/egusphere-egu23-15364, 2023.

A.271
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EGU23-12883
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BG5.4
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ECS
Silvia Sigismondi, Valeria Luciani, and Laia Alegret

Understanding the resilience of the ecosystems within the context of the ongoing global climate change is a
pressing challenge for humankind. The combination of the huge archive available in the geological record
with studies on modern biota is essential to formulate realistic predictions, and the Paleogene is one of the
most climatically dynamic periods in Earth´s history, offering this crucial opportunity. Here we focus on the
Middle Eocene Climatic Optimum (MECO), a global warming event during which marine bulk and benthic
carbonate δ 18 O values steadily declined by roughly 1‰ in over ~400 kyr, usually interpreted as a 3–6 °C
increase in global temperature followed by a rapid return to pre‐event conditions. This event record
temperatures and pCO2 that Earth will reach whether anthropogenic emissions will not stop (RCP8.5). A
number of characteristics, including greater‐than‐expected deep‐sea carbonate dissolution, a lack of globally
coherent negative δ 13 C excursion in marine carbonates, a duration longer than the characteristic timescale of
carbon cycle recovery, and the absence of a clear trigger mechanism, make the MECO one of the most
enigmatic events in the Cenozoic, dubbed a middle Eocene “carbon cycle conundrum”.
The paleoenvironmental and biotic consequences of the MECO are still poorly constrained, however, and
here we focus on the response of planktic foraminifera, which are extremely sensitive to the physical and
chemical state of the oceans. Quantitative studies of planktic foraminiferal assemblages from South Atlantic
ODP Site 702 allowed us to characterize the MECO at this key southern high-latitude setting. The magneto
and stable isotope stratigraphy are well constrained at this site, together with the calcareous nannofossils and
benthic foraminiferal response (Rivero-Cuesta et al., 2019, Paleoceanography and Paleoclimatology).
Our results indicate a pronounced southern migration of the warm index Acarinina coupled by a marked
decline in the abundance of the cold index Subbotina. Additionally, the low-latitude species Orbulinoides
beckmanni occurs only at the MECO peak. The post-MECO assemblages show a recovery of the pre-event
abundances, with the exception of the genus Chiloguembelina, which shows a striking increase in abundance
and suggests an intensification of the Oxygen Minimum Zone. A further result of our study is the greater
sensitivity of planktic foraminifera to the MECO with respect to calcareous nannofossils, as changes in
planktic foraminiferal assemblages started ~2 kyr before the calcareous nannofossil turnover.

How to cite: Sigismondi, S., Luciani, V., and Alegret, L.: The Middle Eocene Climatic Optimum (MECO) impact on Southern Atlantic planktic foraminifera (Site 702), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12883, https://doi.org/10.5194/egusphere-egu23-12883, 2023.

A.272
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EGU23-14992
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BG5.4
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ECS
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Rajendra Prasad Sahu, Sunanada Mandal, Swatilekha Sarkar, Debarshi Mukherjee, Sufia K Kazy, and Pinaki Sar

Life that inhabits deep within the continental crust remained enigmatic, and scientifically less explored. Recent scientific drilling of 3000-meter-deep scientific borehole at the Koyna seismogenic zone of the Deccan Traps, India provided an unprecedented opportunity to investigate the nature of life that evolved and existed within the extreme environment of Archean granitic basement. Rock core samples recovered from deep (up to ~2910 meter below surface), progressively hot (up to 74 °C), high pressure, alkaline, oligotrophic biosphere were analyzed through amplicon sequencing, metagenomics, and cultivation-based approaches. 16S rRNA gene amplicon sequencing showed considerable bacterial diversity. A significant proportion (50-63 %) of the microbial community, represented by the members of Actinobacteria, Gammaproteobacteria, Alphaproteobacteria, Bacilli and Clostridia was identified as endemic or core microbiome of this extreme realm. Relative abundance of different taxa of the core microbiome varied with depth in response to prevailing lithology and geochemistry. Ecological modeling depicted a major role dispersal limitation in explaining community variability suggesting the greater impact of stochasticity on the community assembly. Co-occurrence network analysis elucidated close interactions among autotrophic and organotrophic bacteria. Shotgun metagenomics revealed a major role of autotrophic carbon fixation via the Wood-Ljungdahl pathway and Rnf complex for energy and carbon metabolism. Presence of other mechanisms of energy generation such as ATPase, H2, CO, CH4 or sulfur oxidation system and the possibility of coupling of electron donors to NO3/SO42− reduction illustrated the metabolic versatility of these organisms in terms of utilizing diverse resources. Deeper analysis suggested the existence of an ‘acetate switch’, coordinating biosynthesis and cellular homeostasis. Reactivation of the rock-hosted microbiome using different nutrients (carbon source, e- donor and acceptor) and at elevated temperatures (up to 70-degree C) and anaerobic conditions showed patterns of differential taxa recruitment for utilizing different substrate regimes. Enrichment of strict anaerobic members of taxa Peptococcaceae, Clostridiaceae Family XIV, Clostridiaceae 2 and Moraxellaceae in H2+CO2 condition corroborated well with their ability for acetogenesis. Universal enrichment of Burkholderiaceae, Bacillaceae and Sphingomonadaceae suggested their abilities to use diverse substrates. Our data provided deeper insights into microbial life and its mechanisms of carbon and energy metabolism within the nutrient- and energy-limiting deep granitic crust.

How to cite: Sahu, R. P., Mandal, S., Sarkar, S., Mukherjee, D., Kazy, S. K., and Sar, P.: Unlocking the mystery of deep biosphere hosted by the Archaean granitic crust underneath the Deccan Traps, Koyna, India, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14992, https://doi.org/10.5194/egusphere-egu23-14992, 2023.

A.273
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EGU23-722
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BG5.4
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ECS
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Dushica Zaova, Elena Jovanovska, Aleksandra Cvetkoska, Bernd Wagner, Bánk Beszteri, and Zlatko Levkov

Climate has strongly influenced species composition and evolution over geological and contemporary timescales. While most attention has been paid to the relationship between macroevolutionary processes and climate along latitudinal gradients, very little is known about how climate changes affect the microevolutionary mechanisms of macroevolutionary processes through time due to the lack of fossils. Here, we use the morphologically variable endemic diatom species, Cyclotella cavitata, and paleoenvironmental data from a sedimentary succession of Lake Ohrid between 1050 ka and 815 ka to investigate the effects of climate on microevolutionary dynamics in diversification processes during the Late Calabrian period. By analyzing morphotype-environment relationships, we found a progressive replacement of morphologies and their abundance in C. cavitata that was mainly related to local environmental changes associated with nutrient availability, lake depth, water column, mixis, and local temperatures. Surprisingly, climate change did not have as great an influence as anticipated, but this cannot be ruled out since this period overlaps with the beginning of the Mid-Pleistocene Transition. This suggests that although the local environment had a greater influence on microevolutionary processes, climate remains an important driver and will also be critical for studies of evolutionary change under future climate change scenarios.

How to cite: Zaova, D., Jovanovska, E., Cvetkoska, A., Wagner, B., Beszteri, B., and Levkov, Z.: The contribution of climate in shaping microevolutionary patterns of diatoms in Lake Ohrid during the Late Calabrian stage, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-722, https://doi.org/10.5194/egusphere-egu23-722, 2023.

A.274
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EGU23-17420
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BG5.4
William Matthaeus, Joseph White, Sophia Macarewich, Jennifer McElwain, and Jonathan Wilson

Environmental restriction of forest distribution may be specific to the eco-physiological limits of era-appropriate plants. Accounting for major limiting factors in deep time will improve understanding of ecosystems dominated by extinct plants, surface processes, and Earth System function. Major plant taxa associated with Earth’s penultimate icehouse (the late Paleozoic ice age [LPIA]) are thought to have been limited by moisture seasonality based on evidence from fossil and geological records. We apply recently described methodologies­—climate modeling and ecosystem-process modeling—to simulate global arboreal vegetation in the late Paleozoic ice age. We will compare the intensity of modeled moisture seasonality with plant performance of major late Paleozoic plant taxa. Using National Center for Atmospheric Research’s Community Earth System Model version 1.2 (CESM) simulations, varying pCO2, pO2, and ice extent for the Pennsylvanian, and fossil-derived leaf C:N, maximum stomatal conductance, specific conductivity, and stem physiological limitations for several major Carboniferous plant groups, we will simulate global ecosystem processes at a 2-degree resolution with Paleo-BGC. We hypothesize that moisture seasonality patterns across Pangea will interact with modeled era-appropriate taxa—based on stem hydraulic hysteresis and leaf water limitations—to impact arboreal plant growth and forest cover. The simulated function of era-appropriate stem and leaf trait combinations may provide a mechanistic link to drought-tolerance evolution in lineages like the coniferophytes that persist across global ecological upheavals.

How to cite: Matthaeus, W., White, J., Macarewich, S., McElwain, J., and Wilson, J.: Moisture Seasonality as a Differential Driver of Modeled Forest Distribution during the Pennsylvanian, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17420, https://doi.org/10.5194/egusphere-egu23-17420, 2023.

A.275
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EGU23-11473
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BG5.4
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ECS
Marjorie Cantine, Axel Gerdes, Sören Eitel, Maria Ovtcharova, and Inigo Müller

Establishing geochronological controls on ancient sedimentary successions is critical for evaluating cause and effect, as well as rates of change, in ancient environments. Towards this goal, U-Pb dating of carbonate phases by in situ LA-ICP-MS offers a rapid and reasonably precise method for evaluating not only depositional ages but also the ages of post-depositional processes affecting carbonate rock. However, this technique is still in its first decade of application to carbonate rocks. Determining the best practices for applying this technique and evaluating the meaning, reliability, and robustness of the data it produces remain areas of interest.

 

In this study, we present the first results from U-Pb dating and geochemical characterization of samples from recent drillcores from Namibia, drilled by International Continental Scientific Drilling Program project GRIND-ECT. GRIND-ECT aims to capture, in drillcore, the Ediacaran-Cambrian transition in key successions worldwide. The Namibian portion of GRIND-ECT targets the Nama Group of southern Namibia, well-known for its abundant fossils and detailed geochemical and geochronological records from outcrop, with the goal of elucidating changes in the Earth system during the diversification of early animals. With both abundant interbedded ashes amenable to U-Pb zircon dating and abundant carbonate, these drillcores offer a natural experiment for comparing results from LA-ICP-MS carbonate dating and other geochronological techniques.

 

Our results show that a significant fraction of samples yield geologically meaningful ages when dated using LA-ICP-MS. These ages are consistent with depositional or early post-depositional ages. Microbially-influenced facies are often the most successful. Theses ages can be further refined using higher-precision techniques. Efforts to date vein calcites, which are often very low in U, have not yet yielded robust ages. Integration of Sr and trace and rare earth element data indicate the promise and the limitations of using these proxies as tests for “datability.”

How to cite: Cantine, M., Gerdes, A., Eitel, S., Ovtcharova, M., and Müller, I.: Preliminary results from U-Pb dating and geochemical characterization of GRIND-ECT carbonate samples from Namibia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11473, https://doi.org/10.5194/egusphere-egu23-11473, 2023.

A.276
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EGU23-12004
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BG5.4
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ECS
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Julian Rogger, Benjamin Mills, Taras Gerya, and Loïc Pellissier

Sustained habitable conditions and the evolution of complex life on Earth depend on efficient climate regulation mechanisms that keep carbon fluxes between geologic reservoirs and the atmosphere-ocean system in balance. The terrestrial biosphere plays an important role in regulating the long-term climate by controlling burial rates of photosynthetically fixed CO2 as well as by mediating CO2 consumption through silicate mineral weathering during plant nutrient acquisition. These long-term carbon sinks balance out carbon inputs to the atmosphere-ocean system by processes including volcanism or the oxidative weathering of buried organic carbon. Current biogeochemical models of the Phanerozoic Earth neglect that the strength of the impact of the terrestrial biosphere on global carbon fluxes is subject to evolutionary dynamics and that it depends on how well the biosphere is adapted to prevailing environmental conditions [1]. Here, we develop a theoretical model to reconstruct global organic and inorganic carbon fluxes over the last 390 Myrs. The model includes eco-evolutionary processes underlying the thermal adaptation, such as the dispersal of terrestrial biomes in response to climatic changes and the in situ adaptive evolution towards the local environment. We show that the speed of evolutionary adaptation of the terrestrial biosphere to climatic shifts strongly affects the long-term atmosphere-ocean carbon mass balance. When considering a slow rate of thermal adaptation of the biosphere, resulting in reduced organic carbon burial and silicate weathering rates following temperature shifts, a closer balance of reconstructed Phanerozoic carbon inputs and outputs to and from the atmosphere-ocean system is obtained. Such a balance is a prerequisite to maintain habitable conditions on Earth’s surface on a multi-million-year timescale. We argue that the climate evolution of the Phanerozoic Earth is strongly defined by biological and evolutionary processes. Understanding these biological dynamics and how they shape the interactions between Earth’s biosphere, geosphere and the climate system may help to understand large shifts in Phanerozoic temperatures and the development of the atmospheric composition of the planet.

[1] Mills, B.J. et al. Modelling the long-term carbon cycle, atmospheric CO2, and Earth surface temperature from the late Neoproterozoic to present day. Gondwana Research 67, 172-186. DOI: 10.1016/j.gr.2018.12.001

How to cite: Rogger, J., Mills, B., Gerya, T., and Pellissier, L.: Thermal adaptation evolution and dispersal of the terrestrial biosphere regulates Earth’s long-term climate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12004, https://doi.org/10.5194/egusphere-egu23-12004, 2023.

Posters virtual: Wed, 26 Apr, 08:30–10:15 | vHall BG

Chairperson: Benjamin Mills
vBG.6
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EGU23-3841
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BG5.4
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ECS
Collen-Issia Uahengo and Fred Bowyer

The oldest Nama Group exposed: Insights from the Tsaus Mountains

(Tsau Khaeb National Park)

C.-I. Uahengo*1, F.T.Bowyer2, K.Kaputuaza1, J.Ndeunyema1, M.Yilales2, R.Alexander2, A.Curtis2, R.Wood2

1Department of Geosciences, University of Namibia, Namibia.

iuahengo@yahoo.com

2School of GeoSciences, University of Edinburgh, UK.

 

     The late Ediacaran Nama Group of southern Namibia and northwest South Africa preserves a richly fossiliferous mixed carbonate-siliclcastic shallow marine succession, subdivided into the Kuibis and overlying Schwarzrand subgroups. Whilst the termination of Schwarzrand Subgroup deposition (ca. 538 million years ago, Ma) is temporally well-constrained by numerous dated volcanic ash interbeds, the age of the base of the Kuibis Subgroup (>547.36 Ma) remains uncertain. Carbonates of the lower Kuibis Subgroup record recovery from a negative carbonate carbon isotope (δ13Ccarb) excursion (Basal Nama Excursion, BANE) that has long been thought to represent the regional expression of the Shuram δ13Ccarb excursion, which itself has recently been re-dated on multiple cratons to ~575–565 Ma. However, siliciclastic rocks of the Kuibis Subgroup preserve soft-bodied fossils of the Nama assemblage, but lack fossils diagnostic of the preceding White Sea assemblage which, along with inferred depositional rates, is commonly used to inform an age for the base of the Nama Group of ~551–550 Ma. The apparent decline in global soft-bodied fossil diversity between the White Sea and Nama assemblages has been suggested by some to reflect an extinction event that may therefore be recorded within the lowermost Kuibis Subgroup, approximately coincident with the BANE. Carbonate rocks of the Kuibis Subgroup also host the first appearances of the biomineralising Cloudina and Namacalathus, but the precise stratigraphic position of their first appearances relative to the soft-bodied fossil record and regional δ13Ccarb profile remain poorly constrained.

     Here we present new stratigraphic, palaeontological, and geochemical (δ13Ccarb and δ18Ocarb) information from the oldest strata of the Kuibis Subgroup. These new insights were gathered during a recent expedition to the westernmost exposures of the Nama Group that outcrop in the Tsaus Mountains, within the Tsau Khaeb National Park (formerly Sperrgebiet). We present the first detailed tectonic and lithostratigraphic assessment of the Tsaus Mountains, including a revised regional geological map, in addition to a high resolution δ13Ccarb chemostratigraphic profile. We use these data to provide a holistic litho- and chemostratigraphic correlation framework for the Kuibis Subgroup of the southern (Witputs) Sub-basin. All published palaeontological information, in addition to important new soft-bodied and skeletal fossil occurrences from the Tsaus Mountains succession, are correlated within this framework and discussed.

How to cite: Uahengo, C.-I. and Bowyer, F.: The oldest Nama Group exposed: Insights from the Tsaus Mountains(Tsau Khaeb National Park), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3841, https://doi.org/10.5194/egusphere-egu23-3841, 2023.

vBG.7
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EGU23-964
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BG5.4
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Jinzhou Luo, Hong Hua, and Qiaokun Dai

The late Ediacaran witnessed rapid turnover of organisms. As one of the earliest biomineralizing animal fossils,Cloudina has greatimplication on the evolution of complex macroscopic organisms . With a relatively stable and wide distribution, Cloudina has become one of the most important indicator fossils of the late Ediacaran. Located in the northwestern margin of the Yangtze Platform, the Gaojiashan Lagerstätte only contains a large number of well-preserved phosphatized Cloudina in the upper part of the Gaojiashan Member of the Dengying Formation, but also consists of many excellent 3-D preserved pyritized Conotubus in its lower part. Conotubus and Cloudina are believed to have some close affinities according to their conotubular forms and funnel-in-funnel structures. However, the relationship between them is still in doubt due to the great distinction in individual sizes and preservation modes. With the help of industrial computerized tomography (CT) technique, the internal structure and integrated feature of the pyritized Conotubus can be well distinguished and isolated from the home rock, which made it possible for the geometric morphological analysis like the isolated phosphatized Cloudina. The result is hopeful as it proved that there are no significant morphological difference between Conotubus and Cloudina in their embryonic tube indicating that the pyritized Conotubus may be the precursor of the biomineralized Cloudina. Given its near-completed sedimentary accumulation and abundant and continuous faunal records for the final interval of Ediacaran, the Gaojiashan section and wjthin which the faunal turnover from Conotubus to Cloudina is consequently a strong candidate for the Global Stratigraphic Section and Point (GSSP). 

How to cite: Luo, J., Hua, H., and Dai, Q.: A Reconsideration of the Relationship between the Terminal Ediacaran Conotubus and Cloudina in southern Shaanxi: New Evidence from Geometric Morphometrical Analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-964, https://doi.org/10.5194/egusphere-egu23-964, 2023.

vBG.8
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EGU23-16599
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BG5.4
Michael Henehan

Oxygen levels in Earth’s oceans are dropping fast due to anthropogenic nutrient input and CO2 release, and the consequences of this for marine ecosystems are difficult to predict. The Cretaceous Period (66- 145 million years ago) witnessed numerous extreme ocean anoxic events (OAEs) – some regional, some global in scale – that are thought to have been caused by pulses of volcanism and CO2 release. If we knew the exact mechanisms by which volcanism triggered these Cretaceous OAEs, and the role of feedbacks and boundary conditions, they could provide vital information as to where potential future tipping points in the Earth system lie. Presently, however, our estimates of climate, atmospheric CO2 and carbon cycling in the Cretaceous are qualitative at best, preventing OAEs from being useful analogues. In this poster, I will introduce the planned PETRARCH project, funded through UKRI matching of an ERC Consolidator Grant, that will aim to fill that gap. PETRARCH will combine new and proven geochemical proxy archives with cutting-edge Earth system modelling to look at how marine life and changes in marine pelagic ecosystems may have interacted with environmental changes to drive pervasive global anoxia. To do this, we will calibrate boron isotopes in the silica shells of radiolarians as a new proxy archive for ocean pH and atmospheric CO2, combine this new radiolarian data with new measurements of carbonate microfossils to reconstruct Cretaceous marine carbon cycling, and use Earth System modelling, tuned to these data, to test what exact biogeochemical feedbacks and climate forcings tipped the Cretaceous Earth into profound, and sometimes global, ocean anoxia.

How to cite: Henehan, M.: PETRARCH: Pinpointing Earth-System Thresholds for Anoxia with new Reconstructions of the Cretaceous Hothouse, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16599, https://doi.org/10.5194/egusphere-egu23-16599, 2023.

vBG.9
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EGU23-963
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BG5.4
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ECS
Qiaokun Dai, Hong Hua, and Jinzhou Luo

Sinotubulites is a kind of late Neoproterozoic straight or slightly curved cylindrical tubular fossils with multiple sets of wall structure and both ends open. It has now been found worldwide, and regarded as one of the representatives of the tubular animal radiation before the Cambrian explosion. In this paper, morphological data about Sinotubulites in the Ediacaran Gaojiashan Biota at the Lijiagou section of Ningqiang, Shaanxi province were analyzed to explore the possible relationship between the characteristics of each part of Sinotubulites in ontogenetic process. A total of 378 well preserved fossil samples were selected for measurement, among which 150 apertural and 134 side view samples were examined under scanning electron microscopy (SEM), and 94 samples were examined under micro-scope, of them, the latter was only used as supplementary data for more accuracy analysis. Through the data processing, it was found that a positive linear relationship exists between the maximum diameter and the diameter of the inner circle (Linear regression R2=0.7), and the linear relationship between the maximum diameter (both five radiant and six radiant tubes) and unilateral length is the most robust (Linear regression, R2=0.8903) in Sinotubulites tubes. In general, there is no significant correlation between the tube length and the wall thickness, either bet ween the tube length and the maximum diameter. The results showed that Sinotubulites may simply discarded its old tube, and secreted a new one to construct a home at different stages of the growth. At the same time, under turbulent hydrodynamic conditions, Sinotubulites, may rely on the variable longitudinal ridges to stabilize the tubes, instead of the secretion of thicker shell walls.

How to cite: Dai, Q., Hua, H., and Luo, J.: Morphometric Study of The Ediacaran Tubular Fossils Sinotubulites, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-963, https://doi.org/10.5194/egusphere-egu23-963, 2023.

vBG.10
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EGU23-6194
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BG5.4
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ECS
Zhen Xu, Jianxin Yu, Hongfu Yin, Andrew Merdith, Jason Hilton, Bethany Allen, Khushboo Gurung, Paul Wignall, Alexander Dunhill, Jun Shen, David Schwartzman, Yves Goddéris, Yannick Donnadieu, Yuxuan Wang, Yinggang Zhang, Simon Poulton, and Benjamin Mills

The Permian–Triassic Mass Extinction (PTME), life’s most severe crisis1, has been attributed to intense global warming triggered by CO2 emissions from Large Igneous Province volcanism28. It remains unclear, however, why super-greenhouse conditions persisted for around five million years after the volcanic episode, when Earth system feedbacks should have returned temperatures to pre-extinction levels within a few hundred thousand years8. Here we reconstruct spatio-temporal maps of plant productivity through the Permian–Triassic and undertake climate-biogeochemical modelling to investigate the unusual longevity and intensity of warming. Our reconstructions show that terrestrial vegetation collapse during the PTME, especially in tropical regions, resulted in an Earth system with low levels of organic carbon sequestration and chemical weathering, leading to limited drawdown of greenhouse gases and protracted period of extremely high surface temperatures.

How to cite: Xu, Z., Yu, J., Yin, H., Merdith, A., Hilton, J., Allen, B., Gurung, K., Wignall, P., Dunhill, A., Shen, J., Schwartzman, D., Goddéris, Y., Donnadieu, Y., Wang, Y., Zhang, Y., Poulton, S., and Mills, B.: Early Triassic super-greenhouse climate driven by vegetation collapse, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6194, https://doi.org/10.5194/egusphere-egu23-6194, 2023.

vBG.11
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EGU23-8459
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BG5.4
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ECS
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Thales Pescarini, Henrique Fernandes, Luiz Gustavo Pereira, Carolina Bedoya Rueda, Marly Babinski, Juliana Leme, Paulo Cesar Boggiani, and Ricardo Trindade

The Neoproterozoic-Paleozoic transition was marked by profound modifications in the Earth-Life system, as evidenced by intense perturbations in biogechemical cycles and the appearance of complex macroscopic life. Many questions remain regarding the relationship and feedback between the biotic and abiotic processes that operated in that period, particularly the interconnections between changes in paleoclimate, tectonics, and the biological evolution. Here we present new geochemical data for the Nama Group, South Namíbia, sampled as part of the ICDP GRIND (Geological Research through Integrated Neoproterozoic Drilling) project, a global scientific collaboration that aims to study, in an integrated and multidisciplinary way, different sedimentary sequences in Namibia, China and Brazil, which encompass the terminal Ediacaran and the base of the Cambrian. Our sampling was carried out in the entire stratigraphic interval of the Nama Group in a 5 m resolution, always respecting the variations in facies and fossiliferous content and avoiding highly disturbed strata. X-ray fluorescence analyses were conducted 745 samples through a portable XRF device. The preliminary results of major elements, such as Si, Al, Ti, Sr and Ca, show major environmental shifts in the stratigraphic column, usually reflecting facies variations. The preliminary data presented herein is of key importance for the subsequent studies in the drill cores of the GRIND project, comprising geochronology, isotope analyses and paleontology.

How to cite: Pescarini, T., Fernandes, H., Pereira, L. G., Bedoya Rueda, C., Babinski, M., Leme, J., Boggiani, P. C., and Trindade, R.: Elemental chemostratigraphy in the Ediacaran-Cambrian Nama Group, Namibia: preliminary results., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8459, https://doi.org/10.5194/egusphere-egu23-8459, 2023.