SSP2.1

EDI
Phanerozoic Stratigraphy, Paleoenvironments, and Paleoclimate

This session aims to showcase an interesting diversity of state-of-art advances in all aspects of Phanerozoic stratigraphy, paleoceanography, paleoclimatology, and orogeny on long- and short timescales in marine and terrestrial environments. Within this broad topic, contributions include but are not limited to case studies of organic and inorganic geochemistry, sedimentology, paleontology, and modelling, alongside integrated approaches to understand evolving earth processes, particularly climate transitions and their consequences.

Convener: Jens O. Herrle | Co-conveners: David BajnaiECSECS, Sietske Batenburg
vPICO presentations
| Wed, 28 Apr, 09:00–10:30 (CEST)

Session assets

Session materials

vPICO presentations: Wed, 28 Apr

Chairpersons: Jens O. Herrle, David Bajnai, Sietske Batenburg
Phanerozoic Sediments and Biodiversity
09:00–09:02
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EGU21-4555
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Highlight
Jean-Christophe Wrobel-Daveau, David Ray, Gareth Carroll, Michael G. Tetley, Graham Baines, Mike Simmons, and Frans van Buchem

The Phanerozoic sedimentary record documents a diverse series of cyclic patterns of sedimentation that reflect multiple drivers of change (e.g. climate, eustasy, tectonics, biotic evolution) operating over a range of time scales (days to hundreds of million years). While short-term cycles can be easily identified within the rock record and have frequently been related to the Milankovitch cycles, medium-term (a few tens of million years) and long-term (hundreds of million years) cycles are less-well-resolved. Notably the identification of medium- and long-term cycles are reliant upon global scale studies, which are typically hampered by low stratigraphic resolution or address sedimentary changes indirectly through proxies (e.g. sea-level models, geochemical trends). Moreover, such difficulties have resulted in uncertainties as to the drivers and durations of medium- and long-term cycles.

To adequately address this challenge, an integrated approach is required, combining 1) large sedimentary and global events datasets, 2) a high-resolution sequence stratigraphic model, and 3) plate tectonic and digital palaeo-elevation modelling.

We present the preliminary results of an industry-led study of medium- to long-term Phanerozoic cycles in global sedimentation and an assessment of the drivers of these cycles. Our study is based upon a spatially- and temporally-enabled global dataset of sedimentary records, obtained from over 8,500 wells. The sedimentary data contained within the wells have been standardised using a hierarchical classification of sediment types and divided into time slices based upon sequence stratigraphic interpretations, and the identification of age calibrated maximum flooding surfaces derived from the Neftex Global Sequence Stratigraphic Model. This approach allows the Phanerozoic sedimentary record to be subdivided into 132 time slices and the proportion of different sedimentary compositions preserved for each time slice can be reported as a percentage. The resultant analysis identifies medium- to long-term cycles in the proportions of siliciclastics, carbonates and evaporites.

There are two long-terms trends apparent from our data, and these have been analysed by a palinspastic reconstruction of each time slice using our digital palaeo-elevation and tectonic models. The first trend is a progressive decrease in the proportion of carbonates relative to siliciclastics, such that carbonates represent ~50% of Cambrian sediments and ~30% of Neogene sediments. This appears linked to early Palaeozoic low latitude continental configurations favouring carbonate sedimentation. The second trend is a notable increase in evaporites from the Late Permian to Late Jurassic (5% to 10%, from a Phanerozoic average of <2%) this appears linked to the Pangea super-continent configuration and persists until its breakup. In addition, other lesser breakup events appear linked to increases in evaporites.

Medium-term cycles are identifiable as significant shifts in the global proportions of siliciclastics relative to carbonates. There is a hierarchical arrangement to these cycles, both in terms of duration and severity of change, suggestive of multiple drivers. An initial comparison with known glaciations, major biotic events impacting carbonate producers and orogenies appears to explain many of these cycles.

How to cite: Wrobel-Daveau, J.-C., Ray, D., Carroll, G., Tetley, M. G., Baines, G., Simmons, M., and van Buchem, F.: Long-term sedimentary cycles of the Phanerozoic; insights from the integration of global stratigraphic datasets and tectonic modelling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4555, https://doi.org/10.5194/egusphere-egu21-4555, 2021.

09:02–09:04
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EGU21-11148
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ECS
Andrej Spiridonov and Shaun Lovejoy

The fundamental question of the biodiversity dynamics field is whether global diversity of organisms is driven by multiple random forces resulting in unsteady pattern or is it constrained by sufficiently strong biotic interactions. The first set of hypotheses is combined under the umbrella of the “Court Jester”, reflecting non-steady nature of the process. The latter set of hypotheses is sometimes combined under the header of the “Red Queen”, an epitomization of perpetual change at constant equilibrium diversity level. Based on the Haar fluctuation analyses of the classical Sepkoski database and Paleobiology Database occurrence based biodiversity data, it was revealed that both datasets show that marine animal genus level diversity is characterized by the two regimes.  The first, up to time scales of 30 to 40 Myrs, has a positive scaling exponent implying that fluctuations diverging with time scale i.e. behaviour like the Court Jester that is apparently unstable. The second regime, at longer time scales has a negative fluctuation exponent so that on average anomalies converge, the system is appears stable: a biodiversity regulating Red Queen regime. The smaller scale diverging regime (unstable) is characterized by nearly the same scaling exponent as megaclimate paleotemperatures, suggests a causal connection with diversity.

To investigate this further, we use a new multi-scale Haar fluctuation correlation analysis to quantify the scale by scale correlations.   We found a persistent trend of increasing correlation of macroevolutionary rates with the surface water temperatures with increasing time scales. At the same time, the diversity shows increasingly negative correlations with the temperatures at longer time scales, which suggest that positive largest scale temperature fluctuations although increased biotic turnover had a regulating effect on the global marine animal diversity levels.

Based on the consideration of dominant processes at the longest time scales we propose that the equilibration of biota is a result of continuous geodispersal and consequently mixing and competition of regional biotas, which becomes increasingly more likely on the deca-million-year time scales.

We conclude that the Earth system processes play a significant role in driving both diverging and equilibrating global biodiversity regimes: both Court Jester and Red Queen regimes may operate, with the former dominant up to ≈ 40 Myrs, and the latter at longer time scales.

How to cite: Spiridonov, A. and Lovejoy, S.: Macroevolution and megaclimate: revealing the domains of the Court Jester and biotic equilibration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11148, https://doi.org/10.5194/egusphere-egu21-11148, 2021.

Paleozoic Paleoenvironments
09:04–09:06
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EGU21-10132
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ECS
Man Lu, YueHan Lu, Takehitio Ikejiri, and Richard Carroll

The Frasnian–Famennian (F–F) boundary is characterized by worldwide depositions of organic-rich strata, a series of marine anoxia events and one of the biggest five mass extinction events of the Phanerozoic. Due to the enhanced burial of organic matter, a coeval positive carbon isotope (δ13C) excursion occurred around the F–F boundary, raising questions about carbon cycle feedbacks during the mass extinction. In this study, we test the hypothesis that enhanced burial organic carbon during the F–F mass extinction led to the rise of paleo-wildfire occurrences. Here, we reconstructed paleo-wildfire changes across the F–F boundary via analyzing fossil charcoal (inertinites) and pyrogenic polycyclic aromatic hydrocarbons (PAHs) from an Upper Devonian Chattanooga Shale in the southern Appalachian Basin. Our data show low abundances of inertinites and pyrogenic PAHs before the F–F transition and an increasing trend during the F–F transition, followed by a sustained enhancement through the entire Famennian interval. The changes in paleo-wildfire proxies suggest a rise of wildfires starting from the F–F transition. Furthermore, we quantified the amount of organic carbon burial required to drive the observed δ13C excursion using a forward box model. The modeling results show an increased carbon burial rate after the onset of the F–F transition and peaking during its termination. The comparison of the carbon burial rate and wildfire proxies indicates that widespread organic carbon burial during the F–F transition might cause elevated atmospheric oxygen levels and hence increased occurrences of wildfires. In addition, chemical index alteration index and plant biomarkers suggest a drying climate initiated during the F–F transition, implying that the enhanced carbon burial probably result in the climate change and amplify the wildfire occurrences.

How to cite: Lu, M., Lu, Y., Ikejiri, T., and Carroll, R.: Enhanced paleo-wildfire occurrences caused by marine organic carbon burial during the Late Devonian Frasnian–Famennian mass extinction, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10132, https://doi.org/10.5194/egusphere-egu21-10132, 2021.

09:06–09:08
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EGU21-1128
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ECS
Gilda Lopes, Zélia Pereira, Paulo Fernandes, Márcia Mendes, João Marques, and Raul C.G.S. Jorge

The Muarádzi Sub-basin is part of the Moatize-Minjova Basin (MMB), an important Karoo aged coalfield in Tete Province, Mozambique. It is a WNW-ESE trending, elongated sedimentary basin located in the eastern part of the MMB, whilst during the late Permian was situated in the southern-central part of Gondwana. In this study, we undertook a multidisciplinary approach involving the lithological, palynofacies, and palynological analysis of samples collected from 3 coal exploration boreholes (DW11, DW21, and DW141) collected from this sub-basin. A total of 99 core samples were collected and studied, allowing for the characterisation of depositional environments and existing palaeofloras for this sub-basin.

The palynological data indicates that all the successions have a Lopingian age, and a vast lowland fluvial setting existed in an area controlled by tectonic movements associated with a continental rifting phase. Correlation between the three sections enabled the recognition of an initial meandering fluvial system affected by repeated flooding events that changed to a braided river. The palynofacies corroborate the interpreted fluvial model and the palynological record obtained.

The existence of a humid and warm climate during the Lopingian led to the development of vast floodplains and diversified wetland types, typical of lowland settings recorded in the analysed samples. The palynofacies analysis also indicate that the thick coal beds’ development is associated with deposition in anoxic to dysoxic environments. Furthermore, the Glossopteris Province vegetation, responsible for the coal development in the Muarádzi Sub-basin, is documented in the palynological assemblages, allowing for the characterization of a flora dominated by glossopterids (Protohaploxypinus and Striatopodocarpites) and gymnosperm pollen (Alisporites). The palaeofloral analysis based on palynological data also shows that associated ferns (e.g., Osmundidacites senectus, Thymospora pseudothiessenii), sphenophytes (e.g., Calamospora) and lycophytes (e.g., Lundbladispora, Kraeuselisporites) were common in this area. Additionally, upland vegetation indicators in the palynological assemblages, as monosaccate pollen grains, are rare, indicating that upland regions were distant from the studied sections.

 

Acknowledgements

This research was fully supported by the project PALEOCLIMOZ (PTDC/CTA-GEO/30082/2017), funded by Fundação para a Ciência e Tecnologia, Portugal. The authors would also like to acknowledge the financial support of the Portuguese Foundation of Science and Technology (FCT) to CIMA through UIDP/00350/2020.

 

How to cite: Lopes, G., Pereira, Z., Fernandes, P., Mendes, M., Marques, J., and Jorge, R. C. G. S.: Multidisciplinary palaeoenvironmental characterisation of the late Permian Matinde Formation, Mozambique , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1128, https://doi.org/10.5194/egusphere-egu21-1128, 2021.

Mesozoic Stratigraphy, Paleoclimate, and Carbon Cycle
09:08–09:10
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EGU21-1346
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ECS
Margarida Vilas-Boas, Niall W. Paterson, Zélia Pereira, Paulo Fernandes, and Simonetta Cirilli

The Algarve Basin is a Mesozoic sedimentary basin located in southern Portugal. The basin was initiated by rifting associated with the opening of the North and Central Atlantic Ocean during the initial breakup of Pangea. Sedimentation commenced with continental red beds, which unconformably overlie folded and faulted late Carboniferous strata. The red bed succession (Silves Sandstones) consists mainly of sandstones and conglomerates at the base, overlain by variegated mudstones interbedded with siltstones and dolomites (Silves Mudstones, Siltstones and Dolomites). The sandstones were deposited in alluvial environments, and the mudstones in alluvial to shallow lacustrine environments. Upper Triassic (Carnian to Norian) macrofossils are scarce in the red bed succession, occurring predominantly in the upper beds of the succession above the Silves Sandstones, and do not accurately constrain the age of the beginning of the Algarve Basin.

A palynological study of a new road cut outcrop of Silves Sandstones, located in central Algarve, was undertaken in order to ascertain its age. A 3 m thick bed of grey siltstones located ca. 2.5 m above the unconformity yielded age-diagnostic palynomorphs, which date the onset of sedimentation in the basin. Samples from the latter bed yielded a moderately well preserved, low diversity palynomorph assemblage, which is dominated by Aulisporites astigmosus, Converrucosisporites sp. and Tulesporites briscoensis. Other taxa present in the assemblage include Alisporites sp., Calamospora sp., Cycadopites sp., Deltoidospora sp., Ovalipollis cf. ovalis, Triadispora sp., and Vallasporites ignacii.

The dominance of A. astigmosus together with V. ignacii is indicative of an early Carnian age based on comparison with independently dated sections described elsewhere in Europe. This new dating evidence thus constrains the beginning of sedimentation in the Algarve Basin to the earliest Late Triassic. The co-occurrence of T. briscoensis and A. astigmosus suggests a mixing of palynofloral elements typical of North American and central European Carnian assemblages respectively, which is consistent with the intermediate position of Portugal between those regions. The dominance of phytoclasts and the absence of marine palynomorphs confirms a continental depositional environment as also suggested by sedimentary lithofacies.

Acknowledgements

The authors would like to acknowledge the financial support of the Portuguese Foundation of Science and Technology (FCT) with the scholarship with the reference SFRH/BD/144125/2019 and would also like to acknowledge the financial support of the FCT to CIMA through UIDP/00350/2020.

How to cite: Vilas-Boas, M., W. Paterson, N., Pereira, Z., Fernandes, P., and Cirilli, S.: Constraining the age of the first pulse of continental rifting associated with the breakup of Pangea in Southwest Iberia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1346, https://doi.org/10.5194/egusphere-egu21-1346, 2021.

09:10–09:12
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EGU21-14318
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ECS
Thomas Letulle, Guillaume Suan, Mikhail Rogov, Mathieu Daëron, Arnauld Vinçon-Laugier, Bruno Reynard, Gilles Montagnac, and Christophe Lécuyer

Greenhouse climates are periods characterized by high atmospheric CO2 levels and the absence of large continental icecaps, conditions that define most of the Phanerozoic eon. Fossil record and proxy data from the Cretaceous-Early Paleogene (145-33 My) greenhouse interval suggest increased polar warmth and reduced latitudinal gradient. Such features are challenging for most climate models. They imply either misinterpretation of paleoenvironmental data or an underestimation of climate sensitivity under greenhouse climate. Here we present a new record from polar (>80°) paleolatitudes of the Early Jurassic (~180My) global warming episode known as the Toarcian Oceanic Anoxic Event. Carbonate clumped isotope (Δ47) thermometry and stable isotope analyses (δ18Oc, δ13C) were performed on pristine aragonite bivalve shells from the Polovinnaya River succession (N Siberia) recording exceptionally low burial. Reconstructed growing season temperatures of 9.7±5.2 to 19.0±3.4 °C and water δ18Ow values of −4.6±1.2 to −2.2±0.8‰VSMOW imply increased warmth and significant freshwater contribution in the Toarcian Arctic seas, in line with coeval Siberian paleobotanical data. The unusually low δ18Ow values confirm the incorrectness of assuming a spatially uniform δ18Osw value for calculation of δ18O-derived paleotemperatures. The inferred Early Jurassic polar sea surface temperatures are in good agreement with independent high latitude proxy data from Cretaceous and Eocene warming events. Together with coeval sea surface temperatures data from the western Tethys Ocean, our new data suggest a strong reduction of latitudinal temperature gradients during the Toarcian relative to modern gradients. The reconstructed polar warmth and reduction in latitudinal temperature gradient are substantially higher than those simulated by most climate models of the Jurassic to Eocene greenhouse periods, and support the increasing amount of data and models indicating an increase of climate sensitivity with CO2 levels. Our results bring critical new constraints for model simulations of Jurassic temperatures and δ18Osw values and suggest that high climate sensitivity is the hallmark of greenhouse climates since at least 180 My.

How to cite: Letulle, T., Suan, G., Rogov, M., Daëron, M., Vinçon-Laugier, A., Reynard, B., Montagnac, G., and Lécuyer, C.: Clumped isotope evidence for polar warmth and reduced salinity during the Early Jurassic, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14318, https://doi.org/10.5194/egusphere-egu21-14318, 2021.

09:12–09:14
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EGU21-8206
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ECS
Alicia Fantasia, Thierry Adatte, Jorge E. Spangenberg, Emanuela Mattioli, Enrique Bernárdez, Nicolas Thibault, François-Nicolas Krencker, and Stéphane Bodin

The Jurassic was punctuated by several episodes of abrupt environmental changes associated with climatic instabilities, severe biotic crisis, and perturbations of the global carbon cycle. Over the last decades, the Toarcian Oceanic Anoxic Event (Early Jurassic, ~183 Ma) and the early Bajocian Event (Middle Jurassic, ~170–168 Ma) have attracted much attention because they represent such episodes of global and severe environmental change. Bracketed in between the Toarcian and the Bajocian, the Aalenian stage (Middle Jurassic, ~174-170 Ma) has received less attention, although there is some evidence from Tethyan and Boreal records that it was a time of environmental changes marked by marine biotic turnovers. The lack of knowledge about the Aalenian palaeoenvironments leaves a gap in our understanding of the wider context of the Toarcian and Bajocian events and hence of environmental feedback mechanisms surrounding Mesozoic carbon cycle perturbations. In this study, we provide a high-resolution, biostratigraphically well-defined carbon isotope records (δ13Corg and δ13Ccarb) combined to Rock-Eval data for the upper Toarcian–lower Bajocian interval from two expanded marl/limestone alternation successions from France (French Subalpine Basin) and Chile (Andean Basin). The comparison with available records from the Tethyan and Boreal domains highlights that medium-term δ13C fluctuations are reproducible across different palaeoceanographic settings from both hemispheres and between different carbon substrates. The new high-resolution dataset highlights the complexity of the Aalenian δ13C record, including previously identified δ13C shifts and hitherto undescribed fluctuations. This study provides one of the most expanded high-resolution chemostratigraphic reference records for the entire Aalenian stage, and shows compelling evidence from both hemispheres that it was a time marked by recurrent perturbations to the global carbon cycle and environmental changes.

 

How to cite: Fantasia, A., Adatte, T., Spangenberg, J. E., Mattioli, E., Bernárdez, E., Thibault, N., Krencker, F.-N., and Bodin, S.: Recurrent global carbon cycle disturbances during the Aalenian: Evidence from France and Chile, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8206, https://doi.org/10.5194/egusphere-egu21-8206, 2021.

09:14–09:16
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EGU21-11871
Mathieu Martinez, Beatriz Aguirre-Urreta, Marina Lescano, Guillaume Dera, Julieta Omarini, Maisa Tunik, Tomas Frederichs, Heiko Pälike, Luis O'Dogherty, Roque Aguado, Miguel Company, and Jose Sandoval

The interval from the Valanginian to the Barremian stages (137–121 Ma; Early Cretaceous) is punctuated by several episodes of environmental changes, accompanied by shifts in weathering intensity on the continents and changes in the Tethyan neritic carbonate production. We synthetize here the astrochronology of two recent studies performed in the Neuquén basin, Vocontian Basin and Subbetic Domain (Aguirre-Urreta et al., 2019; Martinez et al., 2020), anchored to CA-ID-TIMS U-Pb ages, which conclusions have been included in the Geologic Time Scale 2020 (Gale et al, in press). We applied this time scale to a compilation of carbon-isotope ratio from belemnites and proxies of detrital supply in the Tethyan area (Vocontian Basin and Subbetic Domain). From this compilation, we show that the episodes of environmental changes are paced by a 2.4-Myr cycle and, with a lower amplitude, a 1.2-Myr cycle. In addition, the new time scale shows the synchronicity between the Weissert Event and the Parana-Etendeka Large Igneous Province. In the series of carbon-isotope ratios measured on belemnite rostra, the amplitude of the 2.4-Myr cycle is twice higher during the Valanginian than in the Late Barremian and three times higher than in the Hauterivian and Early Barremian, suggesting that the activity of the Parana-Etendeka Large Igneous Province amplified the initial orbital forcing to trigger the environmental changes observed during the Mid-Valanginian.

Reference:

Aguirre-Urreta, B., Martinez, M., Schmitz, M., Lescano, M., Omarini, J., Tunik, M., Kuhnert, H., Concheyro, A., Rawson, P.F., Ramos, V.A., Reboulet, S., Noclin, N., Frederichs, T., Nickl, A.-L., Pälike, H., 2019. Interhemispheric radio-astrochronological calibration of the time scales from the Andean and the Tethyan areas in the Valanginian–Hauterivian (Early Cretaceous). Gondwana Research 70, 104-132. https://doi.org/10.1016/j.gr.2019.01.006.

Gale, A.S., Mutterlose, J., Batenburg, S., in press. Chapter 27: The Cretaceous Period, in: Gradstein, F.M., Ogg, J.G., Schmitz, M.D., Ogg, G.M. (Eds.) Geologic Time Scale 2020. Elsevier BV, Amsterdam, The Netherlands, pp. 1023–1086.

Martinez, M., Aguado, R., Company, M., Sandoval, J., O’Dogherty, L., 2020. Integrated astrochronology of the Barremian Stage (Early Cretaceous) and its biostratigraphic subdivisions. Global and Planetary Change 195, 103368. https://doi.org/10.1016/j.gloplacha.2020.103368.

How to cite: Martinez, M., Aguirre-Urreta, B., Lescano, M., Dera, G., Omarini, J., Tunik, M., Frederichs, T., Pälike, H., O'Dogherty, L., Aguado, R., Company, M., and Sandoval, J.: Assessing orbital vs. volcanic control on carbon cycle during the Early Cretaceous, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11871, https://doi.org/10.5194/egusphere-egu21-11871, 2021.

09:16–09:18
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EGU21-1279
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ECS
Madeleine L. Vickers, Mads E. Jelby, Jennifer M. Galloway, Lawrence Percival, Feiyue Wang, Hamed Sanei, Kasia K. Śliwińska, Gregory D. Price, Clemens V. Ullmann, Iben W. Hougård, Ivar Midtkandal, Tamsin Mather, and Christoph Korte

Arctic carbon cycling and its regional climate have been observed to deviate from global trends in the Late Jurassic and across the Jurassic–Cretaceous boundary interval, but appear to recouple with global trends in the Early Cretaceous (Galloway et al., 2019; Jelby et al., 2020). We investigate the possible link between these observed trends and volcanism by examining the mercury (Hg) and other element records from Arctic sites in Svalbard (Norway) and the Queen Elizabeth Islands, Canada. We assess whether pulsed phases of the High Arctic Large Igneous Province, or the globally significant emplacement of Paraná-Etendeka or Greater Ontong-Java Plateau, are expressed by stratigraphic Hg trends recorded in the studied sites of Arctic Canada and Svalbard, and how any signals correlate with the regional stable carbon-isotope (δ13C) record. We compare these new data to Hg and δ13C records from other globally distributed sites, focusing on the carbon isotope excursion (CIE) intervals: the Arctic-wide Volgian CIE (“VOICE”), the global Valanginian positive CIE (“Weissert Event”), and the global early Aptian CIE associated with Ocean Anoxic Event 1a (OAE1a).

How to cite: Vickers, M. L., Jelby, M. E., Galloway, J. M., Percival, L., Wang, F., Sanei, H., Śliwińska, K. K., Price, G. D., Ullmann, C. V., Hougård, I. W., Midtkandal, I., Mather, T., and Korte, C.: Volcanism and carbon cycling in the High Arctic during the Late Jurassic – Early Cretaceous, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1279, https://doi.org/10.5194/egusphere-egu21-1279, 2021.

09:18–09:20
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EGU21-10135
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ECS
Max J. Bouwmeester, Lydian Boschman, Nienke Berends, Jeremy D. Owens, Ben C. Gill, and João P. Trabucho Alexandre

Although anoxia is rare in modern oceans, the marine stratigraphic record is punctuated by sedimentary and geochemical evidence for episodes of widespread oceanic anoxia. The last time in Earth history that a large volume of the ocean became anoxic was in the middle Cretaceous: black organic-carbon-rich muds were repeatedly preserved on the deep seafloor during oceanic anoxic events (OAEs).

Sedimentary and geochemical evidence for oceanic anoxia during OAEs comes mainly from the Atlantic and Tethys Oceans. Data from the Pacific Ocean, which was the largest ocean basin in the middle Cretaceous, is scarce and equivocal. Based on black shales deposited at depths of about 500–1500 m on seamounts, Monteiro et al. (2012) have suggested that at least 50 vol% of the ocean was anoxic at the climax of Cretaceous oceanic anoxia during the late Cenomanian. They also included a single black shale at DSDP Site 585 in the Mariana Basin as evidence for anoxia in the deep Pacific. We will show, however, that this is a mud turbidite reworked from shallower water.

For this study, we reviewed all available data and publications from scientific drilling that recovered Cretaceous sediments in the Pacific Ocean. The little available Cretaceous record from the Pacific consists mainly of well-oxidized sediments. The exceptions are black shales that occur at depths of about 500–1500 m on seamounts. Takashima et al. (2011) have shown that the Asian and North American continental margins of the Pacific were indeed oxic for most of the late Cenomanian OAE. 

We used a new paleomagnetic reconstruction of the Pacific plate back to 150 Ma to show that all investigated Cretaceous organic-carbon-rich sediments in the Pacific Ocean were deposited while the site was located in the Equatorial Divergence Zone (10°S to 10°N). We therefore argue that organic matter deposition in the Pacific Ocean might not have been directly related to OAEs, but rather be associated with the passage of seamounts beneath the equatorial belt of high productivity.

Several authors have challenged suggestions that OAEs were characterized by globally pervasive anoxic deep water and pointed to the difficulty in sustaining whole-ocean anoxia, even in warm oceans. We agree and our results show that oceanic anoxia in the Pacific is a local phenomenon superposed on a global trend of expanded oxygen minima in the ocean.

How to cite: Bouwmeester, M. J., Boschman, L., Berends, N., Owens, J. D., Gill, B. C., and Trabucho Alexandre, J. P.: Cretaceous Black Shales in the Pacific: The Equatorial Position Hypothesis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10135, https://doi.org/10.5194/egusphere-egu21-10135, 2021.

09:20–09:22
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EGU21-8630
Docho Dochev, Michael Wagreich, and Polina Pavlishina

The Central Srednogorie Zone of Bulgaria represents a chain of strike-slip and pull-apart basins, part of the of the peri-Tethyan arc/back-arc basin system. The Upper Cretaceous volcano-sedimentary sequence in the western part of the Central Srednogorie Zone, forms two strips, spanning the Turonian-Maastrichtian interval. This succession is represented by basal siliciclastic sediments, an interval with magmatic rocks followed by volcanoclastic and epiclastic deposits, covered by white, red, grey limestones, with fast transition to sandy low-density turbidites. One of the most representative and continuous sedimentary record in the Panagyurishte strip is exposed east of the Petrich village (Petrich section).  

The base of the Petrich section is composed of the rocks from the so-called lower epiclastic unit (Coniacian-Santonian), followed by grey, pink to variegated limestones of the Mirkovo Formation (Santonian-Campanian). The middle and upper part of the section consists of muddy-sandy turbidites of the Chugovitsa Formation (Campanian-Maastrichtian). The lower part of this formation, the Voden Member, composed of grey thin bedded marls with rare sandstones beds, has yielded a comparatively rich macro- and microfossil record. Upwards, thin to medium bedded sandstones and marls are in alternation, with documented mudstone dominated intervals.  

The present study of the Petrich section is focused on integrated biostratigraphical analysis, based on three important fossil groups for the Campanian – inoceramid bivalves, nannofossils and dinoflagellate cysts. The study in progress creates a comprehensive calibrated dataset, in which the nannofossil and dinoflagellate cyst ranges and inoceramid occurrences, provide valuable markers for age assessment and stratigraphic subdivision of the Campanian. The presence of the nannofossil Ceratolithus aculeus marks a middle to late Campanian age, followed by a typical late Campanian assemblage including Broinsonia parca parca, Reinhardtites levis and rare Eiffellithus eximius. A high diversity dinocyst association is identified and ranges of key Campanian species as Corradinisphaeridium horridum, Raetiaedinium truncigerum, Palaeohystrichophora infusorioides and Cannosphaeropsis utinensis provided valuable markers for the stratigraphic subdivision of the Campanian. Typical middle Campanian “Inoceramusellipticus and “Inoceramusagdjakendsis were documented from the Voden Member. The paleoenvironmental analysis, based on dinocyst assemblages and palynofacies data, suggests stable open-marine depositional environment and oligotrophic conditions, with normal marine productivity and nutrient availability during the Campanian in the basin.

Acknowledgements. The study is part of the Bilateral Bulgarian-Austrian collaboration within project KP-06-Austria/9.

How to cite: Dochev, D., Wagreich, M., and Pavlishina, P.: Campanian biostratigraphy and paleoenvironments, a case study from the Central Srednogorie Zone, Central Bulgaria, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8630, https://doi.org/10.5194/egusphere-egu21-8630, 2021.

09:22–09:24
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EGU21-12656
Michael Wagreich, Erik Wolfgring, Johann Hohenegger, Jaume Dinarès-Turell, Christoph Spötl, and Benjamin Sames

The Postalm section in the Gosau Group (Northern Calcareous Alps) exposes pelagic deposits of northwestern Tethyan origin. We present a magneto-, bio- and chemostratigraphic assessment of this Santonian to uppermost Campanian record, as well as a cyclostratigraphic model for the Tethyan Campanian based on three independently assessed proxies; the δ13C signature, the elemental ratio of Fe and the thickness of limestone/marl couplets (Wolfgring et al., 2021).

The Santonian/Campanian transition is characterised by condensed greyish packstones, the Campanian strata exhibit a succession of limestone-marl couplets that represent orbital precession of an approximate duration of 20ka. A magneto- and biostratigraphic (based on planktonic foraminifera and calcareous nannofossils) framework is supported by carbon isotope and strontium stratigraphy.

The Sr isotope record matches the data for the Upper Cretaceous and suggests no major gaps in the Postalm succession. A robust cyclostratigraphic assessment of three independently assessed data series (L/M couplets, Fe and δ13C) resulted in the identification of eighteen 405 ka eccentricity cycles spanning the middle to upper Campanian (Contusotruncana plummerae to Gansserina gansseri Zones or CC17/UC15 to CC23/UC16 nannofossil zones).

Carbon isotope stratigraphy identifies the LCE (Late Campanian Event) and possibly the SCBE (Santonian Campanian Boundary Event). Magneto- and biostratigraphic data, in particular the position of the top of the R. calcarata planktonic foraminifera Zone, the position of the LCE and the top of Chron C32r.1r served as primary tie points and constraints to match the floating cyclostratigraphic model to the Laskar solution and to compare it to other cyclostratigraphic solutions and reference sections for the upper Campanian.

References: Wolfgring, E., Wagreich, M., Hohenegger, J., Böhm, K., Dinarès Turell, J., Gier, S., Sames, B., Spötl, C., Jin, S., 2021. An integrated multi-proxy study of cyclic pelagic deposits from the north-western Tethys: The Campanian of the Postalm section (Gosau Group, Austria), Cretaceous Research, 120, 104704, doi.org/10.1016/j.cretres.2020.104704.

How to cite: Wagreich, M., Wolfgring, E., Hohenegger, J., Dinarès-Turell, J., Spötl, C., and Sames, B.: A multistratigraphic study of the Campanian Postalm section (Northern Calcareous Alps, Austria), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12656, https://doi.org/10.5194/egusphere-egu21-12656, 2021.

09:24–09:26
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EGU21-2182
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ECS
Iris Vancoppenolle, Johan Vellekoop, Monika Doubrawa, Pim Kaskes, Matthias Sinnesael, John Jagt, Philippe Claeys, and Robert P. Speijer

The mid-Maastrichtian event (MME), ~69 Ma, represents a global negative δ13C excursion which is linked to the extinction of inoceramid bivalves and latitudinal migration of planktonic foraminifera. While the actual extinction of inoceramids was diachronous across the globe, the decline of this important fossil group is generally linked to environmental changes across the mid-Maastrichtian interval. The MME is potentially related to changes in oceanic circulation. While the MME, and associated decline of inoceramids, has been recorded from a variety of deep-sea sites, little is known about the MME signature in shallow epicontinental environments.

Recently, the MME has been recorded for the first time from the type-Maastrichtian, in the Maastricht-Liège region (The Netherlands and Belgium), in newly generated bulk carbonate carbon isotope records from the Hallembaye quarry (NE Belgium) and former ENCI quarry (SE Netherlands). These quarries are approximately 8 km apart. The type-Maastrichtian succession was deposited in a shallow subtropical sea during the Late Cretaceous. As the stratigraphic position of the MME is now constrained in the type-Maastrichtian record, this succession presents an interesting opportunity for studying the signature of this event in a relatively shallow epicontinental basin. Therefore, we are generating high-resolution benthic foraminiferal assemblage data and species-specific carbon and oxygen stable isotope records across the MME interval at these two quarries, in order to unravel biotic and environmental expressions of the MME in the Maastrichtian type area. This is done using the high-resolution sample set acquired in the context of the Maastrichtian Geoheritage Project. Our preliminary data show a distinctive acme of the benthic foraminifer Cuneus trigona in the interval that roughly that corresponds to the MME, potentially caused by a change in quality of the organic matter that reached the sea bottom, highlighting local environmental and oceanographic perturbations across this event.

How to cite: Vancoppenolle, I., Vellekoop, J., Doubrawa, M., Kaskes, P., Sinnesael, M., Jagt, J., Claeys, P., and Speijer, R. P.: The benthic foraminiferal response to the mid-Maastrichtian event in the Maastrichtian-type area, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2182, https://doi.org/10.5194/egusphere-egu21-2182, 2021.

09:26–09:28
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EGU21-12647
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Highlight
Gregory Price, Emily Dearing Crampton-Flood, Rhodri Jerrett, Sabine Lengger, Bart van Dongen, David Naafs, Richard Pancost, Aris Lempotesis-Davies, and Paul McCormack

The Cretaceous-Paleogene (K-Pg) boundary marks one of the five major mass extinctions of the Phanerozoic. A bolide impact and flood basalt volcanism compete as triggers for the extinction, but their relative roles remain contentious. This is in part related to a paucity of robust measurements of temperature change at millennial time scales across the K-Pg boundary. Using the distribution of branched tetraether lipids in samples collected from coals (fossil peats), we present the initial findings of an ongoing study attempting to reconstruct temperatures across North America in the latest Cretaceous to earliest Paleogene. The glycerol dialkyl glycerol tetraether (brGDGTs) palaeotemperature proxy – which has been successfully applied to temperature reconstructions in the Pleistocene and Holocene – is being applied to a succession of fossil peats (lignites) that span the K-Pg boundary at ten sites from Colorado in the south to the North West Territories in the north. The Iridium anomaly that is synonymous with bolide impact at the K-Pg boundary can be used as a datum to correlate the coals. Data derived from coals deposited at a latitude of ~55 °N in Saskatchewan (Canada), are interpreted to reveal millennial-scale records of terrestrial mean annual air temperature (MAAT) for an interval spanning the latest Maastrichtian and earliest Paleogene. The MAAT record peaks at 28 °C ~1 ka (+ 4 ka/- 0.3 ka) after the K-Pg boundary, and subsequently recovers to pre-event values in the subsequent ~ 5 ka (+30 ka/-2 ka). Our unique record is consistent with an abrupt increase in atmospheric CO2 that has been widely documented at this time. 

How to cite: Price, G., Dearing Crampton-Flood, E., Jerrett, R., Lengger, S., van Dongen, B., Naafs, D., Pancost, R., Lempotesis-Davies, A., and McCormack, P.: A terrestrial temperature peak in the first millennia after the Cretaceous-Paleogene Boundary , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12647, https://doi.org/10.5194/egusphere-egu21-12647, 2021.

Cenozoic Paleoenvironments, Paleoclimate, and Cyclostratigraphy
09:28–09:30
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EGU21-8008
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ECS
Vicente Gilabert, Sietske J. Batenburg, Ignacio Arenillas, and José A. Arz

The main trigger for the Cretaceous/Paleogene boundary (KPB) mass extinction is still subject of intense debate. The co-occurrence of the Chicxulub impact (Yucatan, Mexico) and massive Deccan Traps volcanism (India) during Chron C29r hinders disentangling their climatic and environmental effects. Unravelling the influence of Deccan volcanism on the KPB extinction and other Maastrichtian and Danian perturbations requires more accurate age calibrations and duration estimates of biotic and climatic events. Here we integrate existing astrochronologies of the Zumaia section, allowing us to produce a refined cyclostratigraphic calibration of the main planktic foraminiferal and paleoclimatic events recorded across the KPB in the well-know Zumaia section (NW, Spain).

At Zumaia, the KPB is marked by a ~8 cm-thick dark clay bed, with low values of %CaCO3 and δ13C. The Chicxulub ejecta-rich airfall layer has been identified at the base of the dark clay bed, but it is partially masked within a 1–2 cm-thick diagenetic calcitic layer. At Zumaia, the KPB has been astronomically calibrated at 66 Ma (compatible with radioisotopic ages), and the duration of dark clay bed is estimated at ~10 kyr. The first appearances (FA) of the Danian planktic foraminiferal index-species Parvularugoglobigerina longiapertura, Parvularugoglobigerina eugubina, Eoglobigerina simplicissima, Parasubbotina pseudobulloides, Subbotina triloculinoides and Globanomalina compressa have been orbitally tuned at Zumaia, to have occurred at 8, 30, 45, 70, 210, and 475 kyr after the KPB. Specimens of Plummerita hantkeninoides have been identified for the first time in the Maastrichtian of Zumaia, and its first occurrence is dated at ~100 kyr before the KPB. Based on d13C data, we have identified the late Maastrichtian Warming Event (LMWE), the early Danian Dan-C2 and the Lower-C29N events. Additionally, a bloom of the eutrophic/opportunist genus Chiloguembelitria, interpreted as a period of environmental stress, has also been recognized above and separate from the KPB clay bed. Besides the KPB, the main paleoclimatic/paleoenvironmental events have been astronomically calibrated at Zumaia as follows: the LMWE between 270 and 120 kyr before the KPB, the Dan-C2 event between 205 and 305 kyr after the KPB, the Lower-C29N event between 520 and 595 kyr after the KPB, and the Chiloguembelitria bloom between 100 and 305 kyr after the KPB. According to this chronology, we conclude that the LMWE and early Danian Chiloguembelitria bloom seems to coincide in time with major volcanic pulses of the Deccan Traps, unlike the Dan-C2 and Lower-C29N events, which appear to have been driven by orbital forcing. Regardless of the cause of climatic and environmental events, all these perturbations appear unrelated to the KPB mass extinction event. It supports the hypothesis that the influence of Deccan volcanism on planktic foraminiferal assemblages during the Maastrichtian and Danian was limited.

How to cite: Gilabert, V., Batenburg, S. J., Arenillas, I., and Arz, J. A.: Astronomical calibration of paleoclimatic and planktic foraminiferal events of the Cretaceous-Paleogene transition at Zumaia, Spain, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8008, https://doi.org/10.5194/egusphere-egu21-8008, 2021.

09:30–09:32
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EGU21-1662
Malcolm Hart, Pritpal Mangat, and Meriel Fitzpatrick

The Paleogene section of Whitecliff Bay (Isle of Wight) is one of the most complete onshore successions in North West Europe (see Curry, 1965, 1966). The microfossil assemblages have been investigated by many micropaleontologists and the succession of foraminifera, ostracods, calcareous nannofossils, pteropods, diatoms, charophytes and dinocysts have been described in varying levels of detail. The planktic foraminiferal datum (Wright, 1972; Murray et al., 1989) in the Lower Eocene and the occurrence of larger foraminifera in the mid-Eocene provide evidence of incursions of warm water taxa that may be recording the presence of the Early Eocene Climatic Optimum (EECO) and the Middle Eocene Climatic Optimum (MECO) although these occurrences could equally be caused by changes in palaeogeography, glacio-eustasy and the general depositional environment.

Over a period of over 40 years samples have been collected from both the cliff succession and, at times of lowered sediment levels, on the foreshore which can often provide 100% exposure of the succession. Preservation of microfossil assemblages in samples is always better when collected from the foreshore while the cliff succession often records no calcareous (e.g., foraminifera) or siliceous microfossils (e.g., diatoms).

Both EECO and MECO are recorded as being brief, transient events while the palaeontological variations look to be of an altogether longer duration. Stable isotope data are limited (Dawber et al., 2011) and, at the present time, do not provide precise confirmation of isotope excursions precisely synchronous with the palaeontological distributions. Nevertheless, the evidence of northward migration by warm-water taxa is quite distinctive and worthy of still further investigation. In the case of MECO, the presence of Nummulites spp., Alveolina fusiformis and corals is certainly suggestive of warm-water migration into the northern confines of the Anglo-Paris-Belgian Basin.

Curry, D., 1965. The Palaeogene Beds of South-East England. Proceedings of the Geologists’ Association, 76(2), 151‒173.

Curry, D., 1966. Problems of correlation in the Anglo-Paris-Basin. Proceedings of the Geologists’ Association, 77(4), 437‒467.

Dawber, C.F., Tripati, A.K., Gale, A.S., MacNiocaill, C., Hesselbo, S.P., 2011. Glacioeustasy during the middle Eocene? Insights from the stratigraphy of the Hampshire Basin, UK. Palaeogeography, Palaeoclimatology, Palaeoecology, 300, 84–100.

Wright, C.A., 1972.  The recognition of a planktonic foraminiferid datum in the London Clay of the Hampshire Basin. Proceedings of the Geologists’ Association, 83, 413‒419.

Murray, J.W., Curry, D., Haynes, J.R., King, C.,1989. Palaeogene. In: Jenkins, D.G., Murray, J.W. (eds), Stratigraphical Atlas of Fossil Foraminifera [2nd Edition] (eds), British Micropalaeontological Series, Ellis Horwood Ltd, Chichester, 490‒536.

How to cite: Hart, M., Mangat, P., and Fitzpatrick, M.: Microfossil evidence for the EECO and MECO events in the Eocene sediments of the Isle of Wight, UK., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1662, https://doi.org/10.5194/egusphere-egu21-1662, 2021.

09:32–09:34
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EGU21-12976
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ECS
Khaled Trabelsi, Benjamin Sames, Michael Wagreich, Miklós Kázmér, Andrea Mindszenty, and Carles Martín-Closas Martín-Closas

The Eocene ‘‘blue hole” freshwater limestones from the bauxite cover-sequence at the Gánt karst system (Vértes Hills), Transdanubian Central Range, north-western Hungary, have yielded rich charophyte assemblages of higher taxonomic and biostratigraphic interest. The taxonomic study of this flora allows revision and emendation of the species Raskyella peckii and facilitates the definition of a new evolutionary anagenetic lineage based on three successive anagenetic varieties of this species which were formerly considered as separate species or subspecies: Raskyella peckii var. peckii (early Lutetian–early Bartonian), Raskyella peckii var. caliciformis (early Bartonian), and Raskyella peckii var. vadaszii (late Bartonian). Based on these, we propose a new local charophyte biozonation with the new Raskyella peckii Superzone (Lutetian–Bartonian), subdivided into three successive charophyte partial range zones: The ‘Raskyella peckii peckii Zone’ (Lutetian–lowermost Bartonian) is locally characterized by an assemblage of R. peckii peckii, Gyrogona caelata forma caelata, G. caelata forma monolifera and Nitellopsis (Tectochara) palaeohungarica. The ‘Raskyella peckii caliciformis Zone’ (lower Bartonian) includes the local assemblage of R. peckii var. caliciformis, G. caelata forma caelata, G. caelata forma monolifera, G. caelata forma baccata, Nitellopsis (Tectochara) palaeohungarica and Chara media. The ‘Raskyella peckii vadaszii Zone’ (upper Bartonian) is composed of the local assemblage of R. peckii var. vadaszii, G. caelata forma bicincta, G. caelata forma baccata, G. caelata forma fasciata, G. tuberosa, Psilochara polita, Psilochara sp., Chara media and Chara subcylindrica. Future research may show the new local biozonation as applicable to whole Europe and complementing the current European charophyte biozonation. Our results show that the sequences from Gánt previously regarded as upper mid-Eocene (upper Lutetian–lower Bartonian) appear to comprise a longer chronostratigraphic interval, i.e. lower Lutetian till upper Bartonian, with also has implications on the understanding of the regional stratigraphy of the Transdanubian Central Range during the Eocene.

How to cite: Trabelsi, K., Sames, B., Wagreich, M., Kázmér, M., Mindszenty, A., and Martín-Closas, C. M.-C.: Charophyte biostratigraphy of continental deposits in a filled-karst system: A case study from the Eocene bauxite cover-sequence at Gánt (Vértes Hills, Hungary), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12976, https://doi.org/10.5194/egusphere-egu21-12976, 2021.

09:34–09:36
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EGU21-10985
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ECS
Allyson Viganò, Edoardo Dallanave, Laia Alegret, Thomas Westerhold, Rupert Sutherland, Gerald R. Dickens, and Claudia Agnini

About 34 Ma, the Warmhouse climate state switched into the Coolhouse state, when a rapid drop in temperature and the establishment of permanent continental ice-sheet on the Antarctic continent occurred (1).

This event, which is referred to as the Eocene-Oligocene transition (EOT; lasted ~500 ka) represents one of the most prominent transitions of the entire Cenozoic. During the EOT, calcareous nannoplankton experienced significant changes in the assemblage coinciding with the long-term cooling and modifications in the sea-surface water conditions (2, 3), suggesting a cause-effect relationship between the onset of the first sustained Antarctic glaciation and the response of phytoplanktonic communities.

We generated a high-resolution calcareous nannofossil and geochemical datasets (δ18O, δ13C and % CaCO3) from IODP Site U1509 (New Caledonia Trough) (4) with the final aim to provide an overview of the paleoclimatic and paleoceanographic evolution of the study area across the EOT. Our bio-magnetostratigraphic results, consistent with shipboard data (5), were compared along with other existing records recovered from Indian Ocean, Equatorial Pacific and Atlantic Ocean in order to critically evaluate the reliability, reproducibility and synchroneity of all the biohorizons taken into consideration and to obtain a clearer global perspective. 

According to major trends and shifts in the assemblage, the ~5 Myr study interval was subdivided into 4 distinct phases, which were also identified based on changes observed in 1) a number of diversity indices (i.e., species richness, dominance, H-index and evenness), 2) the warm-oligotrophic taxa abundance (Discoaster saipanensis, D. barbadiensis and Ericsonia formosa), 3) the principal component (PC1 and PC2) scores, and 4) bulk stable isotopes and carbonate content. The observed changes are interpreted as an overall decline of warm-oligotrophic communities and, conversely, the incoming of genera better adapted to cooler and more eutrophic conditions.

The most prominent shift in the assemblage occurred during a time window of ~520 kyr, the precursor phase, with relatively high bulk δ18O and % CaCO3 values, that predated the phase of maximum glacial expansion (Earliest Oligocene Glacial Maximum – EOGM) (6) and documented the permanent loss of the late Eocene k-selected community, characterized by warm and oligotrophic taxa.

References

1. T. Westerhold et al., Science. 369, 1383–1388 (2020).

2. T. Dunkley Jones, P. R. Bown, P. N. Pearson, J. Syst. Palaeontol. 7, 359–411 (2009).

3. H. K. Coxall, P. N. Pearson, in Deep-Time Perspectives on Climate Change: Marrying the Signal from Computer Models and Biological Proxies, Micropaleontology Society Special Publication, M. Williams, A. M. Haywood, J. Gregory, D. N. Schmidt, Eds. (Geological Society, London, 2007), pp. 351–387.

4. R. Sutherland, G. R. Dickens, P. Blum, the Expedition 371, Int. Ocean Discov. Progr. (2017), doi:10.14379/iodp.pr.371.2018.

5. R. Sutherland et al., Tasman Front. Subduction Initiat. Paleogene Clim. Proc. Int. Ocean Discov. Program, 371 Coll. Station. TX (International Oce. 371, 1–35 (2019).

6. Z. Liu, S. Tuo, Q. Zhao, X. Cheng, W. Huang, Chinese Sci. Bull. 49, 2190–2197 (2004).

How to cite: Viganò, A., Dallanave, E., Alegret, L., Westerhold, T., Sutherland, R., Dickens, G. R., and Agnini, C.: Calcareous nannofossils from the Tasman Sea (IODP Site U1509): biochronology, paleoclimatic evolution and bulk stable isotopes across the Eocene-Oligocene Transition, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10985, https://doi.org/10.5194/egusphere-egu21-10985, 2021.

09:36–09:38
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EGU21-10907
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ECS
Maria Elena Gastaldello, Claudia Agnini, Edoardo Dallanave, Thomas Westerhold, Adriane R. Lam, Michelle K. Drake, Gerald R. Dickens, Rupert Sutherland, and Laia Alegret

The latest Miocene-early Pliocene biogenic bloom is a poorly understood paleoceanographic event that has been traditionally related to increased primary productivity; and associated changes in the marine carbon cycle. In order to identify this event in the Tasman Sea, we carried out an integrated study at IODP Site U1506. First, we have constructed an age model based on an integrated approach (i.e. biostratigraphy, astrocyclostratigraphic tuning). This permits the identification of the precise position as well as the duration of the biogenic bloom in the Tasman Sea but also the calculation of sedimentation rates across the study interval. In this framework, we generated quantitative micropaleontological records (benthic and planktic foraminifera and calcareous nannofossils) and a low-resolution carbon and oxygen stable isotope records on Cibicidoides mundulus and Trilobatus sacculifer across an interval spanning from 233.50 to 81.75 m CSF-A (Tortonian, late Miocene to Zanclean, early Pliocene). Quantitative assemblage work and statistical analyses on the resulting dataset point to increased export productivity in the lower part of the interval (between CNM15 and CNM18, Backman et al., 2012), as inferred from benthic foraminiferal assemblages dominated by taxa (e.g. Uvigerina and Ehrenbergina) that have been reported to be common across the biogenic bloom in the Indian Ocean (Dickens and Owen, 1999). The paleoecological analysis of these assemblages suggests eutrophic conditions at the seafloor and low oxygen concentration of bottom waters.

Reference

Backman, J., Raffi, I., Rio, D., Fornaciari, E., & Pälike, H., 2012. Biozonation and biochronology of Miocene through Pleistocene calcareous nannofossils from low and middle latitudes. Newsletters on Stratigraphy, 45(3), 221–244.

Dickens, G.R. and Owen, R.M., 1999. The latest Miocene-early Pliocene biogenic bloom: A revised Indian Ocean perspective. Marine Geology, 161: 75-91.

Acknowledgments

University of Padova DOR grant, CARIPARO Foundation Phd scholarship.

Spanish Ministry of Economy and Competitiveness and FEDER funds (PID2019-105537RB-I00).

How to cite: Gastaldello, M. E., Agnini, C., Dallanave, E., Westerhold, T., Lam, A. R., Drake, M. K., Dickens, G. R., Sutherland, R., and Alegret, L.: Hunting down the late Miocene-early Pliocene biogenic bloom in the Tasman Sea: an integrated study at IODP Site U1506, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10907, https://doi.org/10.5194/egusphere-egu21-10907, 2021.

09:38–09:40
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EGU21-6900
Martin J. Head, Jan Zalasiewicz, Adele Bertini, and Liping Zhou

The Middle Pleistocene Subseries and Chibanian Stage were officially defined in 2020 through ratification of the Global Boundary Stratotype Section and Point (GSSP) at Chiba, Japan (Suganuma et al., in press).  Their shared base at 774.1 ka represents the approximate midpoint of the Early–Middle Pleistocene transition, a 1.4–0.4 ka interval marked by a progressive increase in the amplitude of climate oscillations and shift towards a quasi-100 ky frequency.  They currently both extend to the base of the Upper Pleistocene Subseries dated provisionally at ~129 ka (Head et al., in press).  Global stages have not traditionally been employed for the Quaternary owing to the long use of global subseries and regional stages.  Global stages are nonetheless required for formal subdivision of the International Chronostratigraphic Chart, and their acceptance in subdividing both the Holocene and Pleistocene Series has become increasingly evident.  The Middle Pleistocene Subseries and Chibanian Stage are currently identical in extent.  With this in mind, we consider the possibility of subdividing the Middle Pleistocene by introducing a second stage, which would shorten the duration of the Chibanian and increase its utility.  There has been increasing recognition of the ‘Mid-Brunhes Event’ (Jansen et al., 1986) more recently termed the ‘mid- Brunhes Transition’ (Yin, 2013; Barth et al., 2018), an abrupt step-change to increased amplitude of the quasi-100 kyr cycles and warmer interglacials from MIS 11 onwards. The base of this new stage would reasonably be placed around the MIS 12–MIS 11 transition (Termination V, ~420 ka), a level clearly recognised in the marine record. This level appears to approximate the bases of the Holsteinian, Hoxnian, Likhvinian, and Zavadivian regional stages across northwestern and central Europe, the Russian Plain, and the Ukrainian Loess Plain; and can be traced across the Chinese Loess Plateau (Cohen and Gibbard, 2020).  The possibility of a second stage will initially be explored by publication of a position paper. If this attracts sufficient support, a Working Group of the International Subcommission on Quaternary Stratigraphy will be established to analyse the case more formally.

Barth, A.M., Clark, P.U., Bill, N.S., He, F., Pisias, N.G., 2018.  Climate evolution across the Mid-Brunhes Transition. Climate of the Past 14, 2071–2087.

Cohen, K., Gibbard, P., 2020. Global chronostratigraphical correlation table for the last 2.7 million years v.2019 (Poster version), Mendeley Data, V3, doi: 10.17632/dtsn3xn3n6.3

Head, M.J., Pillans, B., Zalasiewicz, J.A., in press. Formal ratification of subseries/subepochs for the Pleistocene Series/Epoch of the Quaternary System/Period. Episodes.

Jansen, J.H.F., Kuijpers, A., Troelstra, S.R., 1986. A mid-Brunhes climatic event: Long-term changes in global atmosphere and ocean circulation. Science 232, 619–622.

Suganuma, Y., Okada, M., Head, M.J. et al., in press. Formal ratification of the Global Boundary Stratotype Section and Point (GSSP) for the Chibanian Stage and Middle Pleistocene Subseries of the Quaternary System: the Chiba Section, Japan.  Episodes.

Yin, Q., 2013. Insolation-induced mid-Brunhes transition in Southern Ocean ventilation and deep-ocean temperature. Nature 494: 222–225.

How to cite: Head, M. J., Zalasiewicz, J., Bertini, A., and Zhou, L.: The Mid-Brunhes Event: a second stage for the Middle Pleistocene Subseries?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6900, https://doi.org/10.5194/egusphere-egu21-6900, 2021.

09:40–09:42
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EGU21-12664
Ekaterina Ershova, Svetlana Sycheva, Svetlana Kuzmina, Inna Zuganova, Pavel Panin, and Margarita Meteleva

The poster presents preliminary results of multidisciplinary studies of a 5-m section of Middle and Late Pleistocene deposits found in a quarry near the town of Dmitrov, Moscow region. The section includes Moscow fluvioglacial sands, alluvium, lake sapropels, and a layered lens of peat overlain by Valdai cover loams with large cryogenic deformations. The sediments were described and analyzed for pollen, plant macrofossils, and insect remains. The results of pollen analysis suggest that the deposits were formed during the second half of the Mikulino (Eemian) interglacial and during the transition to the Valdai (Weichselian) Glaciation (MIS 5e to MIS 5d). The pollen diagram reflects the replacement of deciduous forests by coniferous forests and the subsequent replacement of closed dark coniferous forests by open communities dominated by birch, shrubs, light-demanding grasses, and Artemisia. Seeds and fruits of wetland and aquatic plants, including endocarps of the extinct species Potamogeton sukaczevii, were found in samples from peat and underlying lake sediments. This may indicate the Mikulino or Early Valdai age of the studied deposits. The entomological fauna indicates the predominance of coastal and marsh species. Environmental conditions were relatively cool, rather characteristic of the late Interglacial. It is expected to obtain micromorphological, physicochemical characteristics of the sediments, as well as OSL dates to clarify the age of the sediments. This work was supported by RFBR, grant N19-29-05024 mk.

How to cite: Ershova, E., Sycheva, S., Kuzmina, S., Zuganova, I., Panin, P., and Meteleva, M.: Preliminary results of a multidisciplinary study of the buried peatland and host sediments of the Moscow-Valdai age (Dmitrov, Moscow region, Russia), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12664, https://doi.org/10.5194/egusphere-egu21-12664, 2021.

09:42–10:30