SSP2.1

SSP2 EDI
Phanerozoic stratigraphy, paleoceanography, and paleoclimate 

This session aims to showcase an exciting diversity of state-of-the-art advances in all aspects of Phanerozoic (Cambrian to Quaternary) stratigraphy, paleoceanography, and paleoclimatology. We invite case studies of organic and inorganic geochemistry, sedimentology, and paleontology from marine and terrestrial environments, as well as multidisciplinary and modeling studies. An emphasis is placed upon the use of a variety of tools for deciphering sedimentary records and their stratigraphy across intervals of major environmental change. We further invite contributions that provide insight into the evolution of the Earth on short and long timescales, including climate perturbations and their consequences.

Co-organized by CL1.1, co-sponsored by ICS and ISSC
Convener: David BajnaiECSECS | Co-conveners: Jens O. Herrle, Sietske Batenburg, David De Vleeschouwer
Presentations
| Wed, 25 May, 08:30–11:50 (CEST), 13:20–16:40 (CEST)
 
Room G2

Session assets

Session materials

Presentations: Wed, 25 May | Room G2

Chairperson: David Bajnai
08:30–08:35
08:35–08:45
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EGU22-9361
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ECS
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solicited
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Highlight
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On-site presentation
Sebastian Steinig, Tessa Alexander, Dan Lunt, Paul Valdes, Zak Duggan, Patrick Lee, Jakub Navratil, Ikenna Offokansi, and Matthew Swann

We can only fully understand the past, present and future climate changes by bringing together data and process understanding from a broad range of environmental sciences. In theory, climate modelling provides a wealth of data of great interest to a wide variety of disciplines (e.g., chemistry, geology, hydrology), but in practice, the large volume and complexity of these datasets often prevent direct access and therefore limit their benefits for large parts of our community.

We present the new online platform “climatearchive.org” to break down these barriers and provide intuitive and informative access to paleoclimate model data to our community. The current release enables interactive access to a recently published compilation of 109 HadCM3BL climate model simulations. Key climate variables (temperature, precipitation, vegetation and circulation) are displayed on a virtual globe in an intuitive three-dimensional environment and on a continuous time axis throughout the Phanerozoic. The software runs in any web browser — including smartphones — and promotes data exploration, appeals to students and generates public interest.

We also show current work on the next phase of the platform, which aims to develop new tools for integration into a more quantitative research workflow. These include easy online generation and download of maps and time series plots of the underlying monthly model data. The data can also be exported as global fields or CSV files for any user-selected location for further offline analysis, such as use in spreadsheets. Finally, we will discuss and outline future integration of new sources of model and geochemical proxy data to simplify and advance interdisciplinary paleoclimate research.

How to cite: Steinig, S., Alexander, T., Lunt, D., Valdes, P., Duggan, Z., Lee, P., Navratil, J., Offokansi, I., and Swann, M.: “climatearchive.org”: 540 million years of climate data at your fingertips, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9361, https://doi.org/10.5194/egusphere-egu22-9361, 2022.

08:45–08:52
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EGU22-6334
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Virtual presentation
Philippe Claeys, Matthias Sinnesael, David De Vleeschouwer, and Christian Zeeden

The study of astronomical climate forcing and the application of cyclostratigraphy experienced a spectacular growth over the last decades. In 2018, the first Cyclostratigraphy Intercomparison Project (CIP) workshop constituted the first attempt to compare different methodological approaches and unite the global community around standard, uniform and reliable procedures. Two major conclusions were: [1] There is a need for further organization of the cyclostratigraphic community (e.g. to streamline different methodologies); [2] Cyclostratigraphy is a trainable skill, but currently many universities lack specific resources for training and education. Today, a regular newsletter, a dedicated free open-access journal “Cyclostratigraphy and Rhythmic Climate Change (CRCC)”, a scientific podcast titled CycloPod, and an educational website “www.cyclostratigraphy.org” connect the cyclostratigraphy community. The newly created CycloNet (Research Foundation Flanders FWO Funding) expands this effort into a real and sustainable scientific research network with partners from all around Europe, and open to the global community. At the same time, CycloNet creates a platform for streamlining and integrating new multi-disciplinary approaches. The main scientific targets for CycloNet in the next five years are: [1] Set up a diverse and sustainable community structure, relying on exchange, interaction and training, [2] Boost research by novel methodological approaches applying advanced signal processing techniques, [3] Organize a second Cyclostratigraphic Intercomparison Project. With this poster, we reach out to the broader community to exchange ideas on concepts and activities that CycloNet can help to develop further towards the future.

How to cite: Claeys, P., Sinnesael, M., De Vleeschouwer, D., and Zeeden, C.: CycloNet: European Cyclostratigraphy Network, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6334, https://doi.org/10.5194/egusphere-egu22-6334, 2022.

08:52–08:54
08:54–09:01
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EGU22-12868
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ECS
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On-site presentation
Damien Pas, Valentin Jamart, and Allison Daley

The Cambrian Explosion is a fundamental turning point in the evolution of life that occurred during the Cambrian Period (~541 to ~485 million years ago), which involved the origination and explosive radiation of all major animal phyla. The bursts of evolution characterizing this period appear concurrently with major modifications to the physico-chemical conditions of the world’s oceans, and are recorded in critical fossil localities where soft-tissues are exceptionally well preserved, including Lagerstätten such as the Burgess Shale and Chengjiang Biota. As a result of the severe lack of biostratigraphically-correlatable fossils (due to widespread endemism during the Cambrian) and sparse high-precision radioisotopic dates, the Cambrian time scale remains among the least defined stage of all the Phanerozoic Eon, with a minimum uncertainty of ±2 million years at its stage boundaries. The absence of a high-resolution geological time scale for the Cambrian Explosion hampers our ability to robustly address widely debated questions concerning the origins and rates of the evolutionary and ecological events, their relationship with paleoceanographic conditions, their responses to astronomically-forced climate change, including from Milankovitch “grand” cycles, and whether these events were globally synchronous.

Using an integrated set of geophysical/chemical proxies with advanced time series techniques on selected stratigraphic sections, this project aims at (1) Generate sets of high- resolution geophysical and geochemical stratigraphic proxies enabling to capture Milankovitch forcing within the selected sedimentary records, (2) Building a high-resolution time scale to improve our knowledges on the timing of major Cambrian evolutionary milestones and geochemical changes and (3) Determine the relationships between Cambrian evolutionary and ecological events with the paleoceanographic changes and Milankovitch cycles.

How to cite: Pas, D., Jamart, V., and Daley, A.: Generating a highly resolved astronomical time scale for the evolutionary and ecological events during the Cambrian Explosion, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12868, https://doi.org/10.5194/egusphere-egu22-12868, 2022.

09:01–09:08
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EGU22-3197
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ECS
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Virtual presentation
Zhengfu Zhao, Nicolas Thibault, Tais W. Dahl, Niels H. Schovsbo, Aske L. Sørensen, Christian M.Ø. Rasmussen, and Arne T. Nielsen

The Cambrian is the most poorly dated period of the past 541 million years of Earth history. This hampers analysis of profound environmental and biological changes that took place during this period. Astronomically forced climate cycle recognized in sediments and anchored to radioisotopic ages provides a powerful geochronometer that has fundamentally refined Mesozoic–Cenozoic time scales but not yet the Palaeozoic. Here we report a continuous astronomical signal detected as geochemical variations (1 mm resolution) in the late Cambrian Alum Shale Formation that is used to establish a 16 Myr-long astronomical time scale, anchored by radioisotopic dates. The resulting time scale is biostratigraphically well-constrained, allowing correlation of the late Cambrian global stage boundaries with a 405-kyr astrochronological framework. This enables a first assessment, in numerical time, of the evolution of major biotic and abiotic changes, including the end-Marjuman extinction and the Steptoean Positive Carbon Isotope Excursion, that characterized the late Cambrian Earth.

How to cite: Zhao, Z., Thibault, N., W. Dahl, T., H. Schovsbo, N., L. Sørensen, A., M.Ø. Rasmussen, C., and T. Nielsen, A.: Synchronizing Rock Clocks in the Late Cambrian, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3197, https://doi.org/10.5194/egusphere-egu22-3197, 2022.

09:08–09:15
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EGU22-8721
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ECS
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On-site presentation
Déborah Harlet, Guilhem Amin Douillet, Jean-François Ghienne, Pierre Dietrich, Chloé Bouscary, Philippe Razin, and Fritz Schlunegger

A semi-3D stratigraphic architecture of the Lower Ktawa Group, deposited during the early Late Ordovician on the northern Gondwana platform in a shallow marine environment, was investigated in the Anti-Atlas. The logging of 42 sections reveals that the Lower Ktawa is dominated by shales, punctuated by fine to coarse sandstones forming successive cuestas. Here, focus is put on three main sand cuestas recording major sea-level drops.

The lowermost cuesta (Foum-Zguid Member) outcrops along >85 km, and dips southward. Three facies associations albeit with complex lateral relationships were distinguished: 1. In the West, coarse-grained cross-bedded sandstones. 2. In the central part, sandstones dominated by Hummocky-Cross-Stratifications (HCS), in amalgamated beds towards the West but isolated within shales towards the East. 3. In the East, dominance of highly bioturbated sandstones. A second cuesta (“Tissint Member”) outcrops exclusively on the western part of the transect, approximately 25-50 m above the Foum-Zguid cuesta, and also dips South-southwestward. This 40 m-thick sandstone complex has a sharp base and is composed of fine to coarse cross-bedded sandstones. At its northeastern limit, the 40 m-thick succession disappears within 3.5 km. The upper cuesta (Bou-Hajaj Member, 5-40 m thick) is found ca.160 m above the base of the Ktawa Group and outcrops in the eastern zone of the study area. Its southern part is characterized by the thickest stack of sandstones, organized in a shallowing upward trend, and comprises HCS-beds and channelized structures a few meters in width. The eastern part is dominated by coarse, bioturbated, cross-bedded sandstones lacking shallowing upward stacking patterns. Its dip is northward, in the opposite direction to the underlying two members. Moreover, from satellite images, a clinothem dipping towards the Northeast is identified, together with the dissociation of the cuesta in two sets pinching out northwestward.

On a regional scale, the directly underlying First Bani Group was reconstructed as a shallow shelf having a northward oriented proximal-to-distal trend (Marante, 2008). A study of the Ktawa Group ca. 200 km Northeast of our study zone evidenced a southwestward proximal-to-distal trend (Meddour, 2016). Furthermore, a regional depocenter of the Ktawa Group is generally thought to occur eastward from our study.

Three interpretation lines are considered to reconcile these apparently contradictory observations: 1. A locally eastward oriented proximal-to-distal trend within a complex sequence stratigraphic framework including superimposed high-frequency cycles. 2. A range of source feeders that may be successively active along an irregular coastline, thereby forming lobes with opposite dispersal patterns. 3. An interplay of reactivation of Panafrican faults (Anti-Atlas/Ougarta) cannot be excluded and may have locally changed the place(s) of maximum accommodation space during deposition. It may also have induced the formation of shoals that would have been partially eroded and recycled. Thus, these apparently contradictory proximal-to-distal trends may actually depict a turning point in the re-organization of the basin predating the end-Ordovician glacial advance.

How to cite: Harlet, D., Douillet, G. A., Ghienne, J.-F., Dietrich, P., Bouscary, C., Razin, P., and Schlunegger, F.: Semi-3D stratigraphic architecture of a siliciclastic shallow-marine platform: Insights from the Ktawa Group (Late Ordovician) in Morocco, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8721, https://doi.org/10.5194/egusphere-egu22-8721, 2022.

09:15–09:22
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EGU22-2950
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ECS
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Virtual presentation
Tomas Želvys, Andrej Spiridonov, Anna Cichon-Pupienis, Andrius Garbaras, and Sigitas Radzevicius

Lithuania is located in the eastern part of the Silurian Baltic Basin which was located near the equator during the Silurian. Kurtuvėnai -161 borehole is located in the Northwest Lithuania. The Silurian geological section of investigated interval is composed of siliciclastic and carbonate deposits and represents deep marine environments.

Samples for stable carbon isotope analysis were collected from 1441 – 1316 m depth interval. The sampling intervals range from 0.2 up to 1m. The stable carbon isotope values from carbonates were measured using Thermo Gasbench II coupled with a Thermo Delta V isotope ratio mass spectrometer.

In the investigated interval 10 graptolites biozones were distinguished: Lapworthi Biozone is distinguished in the lowest part of the section and linked to the Adavere Regional Stage (uppermost Telychian); the centrifugus - belophorus biozones mark the Jaani Regional Stage; perneri - lundgreni biozones correspond to the Jaagarahu; and parvus - nassa biozones marks the Gėluva Regional Stage of the Wenlock.

According to the δ13Ccarb isotope analysis results, a positive excursion was detected in the lower part of the studied interval from 1422.8 m up to 1390.8 m depth. There, the δ13Ccarb maximum value is 3.87 ‰. This positive δ13Ccarb anomaly can be linked to the Ireveken positive stable carbon isotopes excursion and the centrifugus – belophorus biozones interval of the lower Wenlock. We can also observe a positive δ13Ccarb excusion in the upper part of Homerian (from 1327 m depth) which potentially can be the lower part of the Mulde positive stable carbon isotopic event.

In summary, the δ13Ccarb values varied from -1.35 ‰ up to 3.92 ‰ in studied interval of Kurtuvėnai-161 borehole. A more detailed biostratigraphic and lithological study is needed for a better understanding of the integrated stratigraphy of the Silurian geological section in the Kurtuvėnai-161 borehole in the future.

How to cite: Želvys, T., Spiridonov, A., Cichon-Pupienis, A., Garbaras, A., and Radzevicius, S.: Preliminary report on δ13Ccarb isotope excursion through the Silurian of Kurtuvėnai - 161 borehole, Northwest Lithuania, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2950, https://doi.org/10.5194/egusphere-egu22-2950, 2022.

09:22–09:29
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EGU22-9471
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Virtual presentation
Anne-Christine Da Silva, Léonard Franck, Michiel Arts, and Julien Denayer

The Hangenberg Crisis, at the Devonian-Carboniferous Boundary, severely affected the marine realm. The crisis is characterised by several events associated with change in the sedimentation and biotic extinctions and turnovers. The Hangenberg Black Shale event that recorded the extinction peak in the pelagic realm corresponds to a widespread development of oceanic anoxia and/or dysoxia. The Hangenberg Sandstone event is associated with an extinction of neritic fauna in shallow-water settings, including the final demise of several classical Devonian faunas (stromatoporoids, quasiendothyrid foraminifers, placoderms, etc.). The succession of these events is nowadays explained by a combination of sea level fluctuations (third order transgressive sequence, out-of-sequence regression) and global climatic changes. Through the identification of Milankovitch cycles in the Chanxhe record, we aim at getting a better understanding of the timing and orbital forcing of the different events of the Hangenberg Crisis in shallow-water settings.

The sedimentary record of the interval of interest at Chanxhe is composed of 16 m of alternating decimetre-thick carbonate beds with shaly siltstones, which displays a clear cyclicity. The carbonate-siliciclastic alternations (~0.8 m) are bundled into larger cycles (~5 m) which are separated by intervals dominated by the shaly facies. This is followed by 11 m of carbonate dominated lithology with thin shale layers displaying a less clear cyclicity with ~3 m thick cycles. Then the equivalent of the Hangenberg dark shales is recorded as two dark shaly intervals separated by a carbonate bed. After the Hangenberg dark shales, the section displays carbonates, with the Devonian Carboniferous boundary in massive carbonates 7 m above the top of the black shales.

Samples have been collected along the record every 10 cm which were measured by the portable X-Ray Fluorescence device (Tracer 5, Bruker), allowing to provide elemental data throughout the record. Spectral analysis is applied on Ca and Al, to identify the main cyclicity in the record. The 0.8 meter-thick limestone/shale alternations is clearly recorded in the Ca and Al records and are associated with precession cycles (18 kyr), while the 5 m-cycles are associated with short eccentricity (100 kyr). Prior to the Hangenberg anoxic events, the 100-kyr cycles became less clear and shorter (~ 3 m) which is interpreted as a minimum eccentricity. During the Hangenberg, the cyclicity returns. However, after the Hangenberg and near the Devonian Carboniferous boundary, the facies become very homogeneous, consisting of massively bedded carbonates with no observable cyclicity,  which is also  other contemporaneous sedimentary successions (e.g. China, Poland).   

 

How to cite: Da Silva, A.-C., Franck, L., Arts, M., and Denayer, J.: Timing and pacing of the Hangenberg Crisis (Devonian-Carboniferous Boundary) in the Chanxhe sections, Belgium , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9471, https://doi.org/10.5194/egusphere-egu22-9471, 2022.

09:29–09:36
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EGU22-2502
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ECS
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Virtual presentation
Maren Sandvold and Maarten Felix

The Nordkapp Basin is located in the southwest Barents Sea. It was formed by rifting in the late Palaeozoic. As the area containing the basin moved north from the equator the climate changed from warm and arid to temperate and humid. Initially a large carbonate platform developed in the Barents Sea in the Carboniferous and Permian. The change in climate due to northward drift caused the platform to shift from a carbonate to clastic platform at the end of the Permian. The sea level changed several times during the Mesozoic due to a combination of eustatic changes and salt diapirism. The depositional environment in the area had been interpreted from multiple cores to vary from onshore coastal plain and delta plain to shelf environment due to the large scale sea level changes. In this work, the cores have been revisited to study smaller scale changes within the environments that had been recognised but not described extensively. The nature of small scale changes is different in different environments and can be seen in different aspects like the bioturbation intensity and clay and sand content. This work will compare the smaller scale sea level changes across the different environments encountered in the cores.

 

How to cite: Sandvold, M. and Felix, M.: Small scale changes superimposed on larger scale sea level-induced changes in cores from the Nordkapp Basin. , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2502, https://doi.org/10.5194/egusphere-egu22-2502, 2022.

09:36–09:43
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EGU22-227
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ECS
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Virtual presentation
Bilal Wadood, Hong Li, and Suleman Khan

The Permian time is characterized by various geodynamic and biotic events. The rifting of Gondwana and the formation of the super-continent Pangea are the most important events. The cessation of major Gondwana rifting and thermal cooling has subsequently resulted in the development of marine Tethyan settings at the margin of the northwestern Indian Plate. Based on detailed outcrop-based lithostratigraphical investigations, a total of three formations have been distinguished. The presence of diagnostic foraminifer’s species able to assign Wordian, Capitanian-Wuchiapingian, and Late Wuchiapingian to Changhsingian ages to these rock units respectively. The detailed biostratigraphic and sedimentological analyses of the upper Permian units of northern Pakistan divulged three phases of the carbonate platform development. Initially, the early Permian pure clastic Gondwana deposits were replaced by the Tethyan setting during the middle Permian (Wordian) time whereby the wave-dominated delta was established as the sea-level rises. However, such deltaic deposits were gradually evolved into a pure carbonate system during the Capitanian time in response to gradual transgression. The Capitanian and Wuchiapingian times show the development of a diverse shallow carbonate platform along the northwestern Indian Plate. The late Permian global regression has significantly disturbed the carbonate factory and subsequently developed river-dominated deltaic deposits of carbonate and clastic mixed system. Such a mixed system was again evolved in a carbonate platform during the Early Triassic.

How to cite: Wadood, B., Li, H., and Khan, S.: Evolution of the Permian carbonate platform on Gondwana shelf, Pakistan: sedimentological and biostratigraphic approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-227, https://doi.org/10.5194/egusphere-egu22-227, 2022.

09:43–09:50
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EGU22-10150
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On-site presentation
Andrej Spiridonov, Lauras Balaukauskas, and Shaun Lovejoy

Brachiopods are a phylum of Animalia which are characterized by a rich fossil record. But this record shows drastic decrease in brachiopod diversity and environmental occupancy through time. One set of explanations says that the decline is related to the state shifts in dominance after mass extinction events (usually P-Tr). Another explanatory set suggests that the dominant cause of brachiopod decline is competition with other functionally similar clades. The competition hypothesis predicts that there should be a monotonic decrease in some fitness metric at organismal or species level. Often overlooked is the influence of long-term tectonic processes which control size, geometry and topology of environments on the changes in dominance of brachiopods. Here we tested this hypothesis by analyzing the dynamics of longitudinal and latitudinal ranges of brachiopod genera in the post-Cambrian Phanerozoic using the Paleobiology Database global paleogeographic occurrence data. The major pattern revealed in the study is that while latitudinal ranges were approximately constant through the eon, the longitudinal ranges experienced long-term trend-like decline. In the beginning of the Phanerozoic and also during the Cretaceous-Cenozoic, average ranges of brachiopod genera were much more elliptic in the west-east direction, while in the middle of the Phanerozoic they become almost circular in their shape. The latitudinal ranges reflect average temperature tolerance of a genus, while the longitudinal ranges reflect capacity of a genus to expand in similar climatic conditions, thus reflecting its potential of expansion fitness. The scale by scale analysis of range shapes and continental fragmentation index found consistent scale independent positive correlation of ellipticity (in W-E direction) with higher fragmentation of continents. Therefore the analyses revealed statistically significant patterns that support the hypothesis of a strong tectonic control on the shapes and sizes of average geographic ranges of brachiopod genera. Smallest ranges with lowest ellipticity occurred in Triassic-Jurassic. Therefore, the loss of genus level expansion fitness due to tectonic amalgamation of Pangaea should have been an important factor which contributed to the failure of brachiopods to fully recover after P-Tr extinction event.

This study was supported by the project S-MIP-21-9 “The role of spatial structuring in major transitions in macroevolution”.

How to cite: Spiridonov, A., Balaukauskas, L., and Lovejoy, S.: Phanerozoic scale modulation of brachiopod longitudinal expansion fitness forced by plate tectonics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10150, https://doi.org/10.5194/egusphere-egu22-10150, 2022.

09:50–10:00
Coffee break
Chairperson: David De Vleeschouwer
10:20–10:22
10:22–10:29
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EGU22-11752
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ECS
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On-site presentation
Giulia Faucher, Stefano Visentin, Gabriele Gambacorta, and Elisabetta Erba

The Toarcian oceanic anoxic event (T-OAE), dated as early Toarcian is considered one of the most extreme paleoenvironmental perturbations in Earth’s history. It is characterized by global warming, accelerated weathering, sea level rise, oceanic anoxia and acidification and extensive accumulation of organic matter. In Jurassic times, calcareous nannoplankton was already a most efficient rock-forming group and therefore pelagic sedimentary successions preserve invaluable data to track changes across the T-OAE. In this work, we focus on Schizosphaerella across the T-OAE recovered in the uppermost Pliensbachian–lower Toarcian Sogno Core that consists of a fully pelagic, continuous, well-dated record from a deep plateau (~1500 m water depth) in the Lombardy Basin (northern Italy). The objective of this investigation is the quantification of changes in size and abundance of the micrite-forming schizosphaerellids to derive their biocalcification tempo and mode in response to the T-OAE perturbations, to assess the implications of Schizosphaerella biocalcification changes, in terms of abundance and size, for the pelagic carbonate sedimentation. Absolute abundances and morphometric changes obtained for small Schizosphaerella punctulata” (valve width < 7 μm),  S. punctulata (valve width > 7 μm) and “encrusted S. punctulata” (all specimens characterized by a crust surrounding the valve) revealed large fluctuations in the investigated interval. We identify an abundance fall caused by the failure of S. punctulata and “encrusted S. punctulata” during the core of the T-OAE, that along with the increased abundance of small specimens produced the reduction of average dimensions. Thus, the average size decline is not the result of a general valve reduction, but rather derives from the increase in abundance of small specimens (< 7 μm). This is substantiated by absolute abundances of individual S. punctulata morphogroups that unambiguously demonstrate that such a pattern is not an artefact of relative abundances (closed sum problem).

We hypothesize that the concomitant drop in abundance and shrinkage of valve size is related to hyperthermal conditions associated with excess CO2 and ocean acidification.

Finally, the co-occurrence in the same samples of S. punctulata specimens (> 7 mm) with and without a crust, is indicative of species-specific diagenetic effects. Based on the S. punctulata ultrastructure we conclude that specimens without diagenetic crusts belongs to S. astrea while encrusted specimens are attributable to S. punctulata and we infer that the presence of the diagenetic crust could be taxonomically diagnostic to distinguish S. punctulata from S. astrea.

How to cite: Faucher, G., Visentin, S., Gambacorta, G., and Erba, E.: Size and abundance variations of Schizosphaerella across the Toarcian Oceanic Anoxic Event , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11752, https://doi.org/10.5194/egusphere-egu22-11752, 2022.

10:29–10:36
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EGU22-4877
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ECS
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Virtual presentation
Thomas Mann, André Bornemann, and Jochen Erbacher

Lower and Middle Jurassic sedimentary deposits in southern Germany have accumulated in a shallow-marine shelf environment and are typically dominated by clayey lithologies with minor occurrences of sandstones and limestones. The sedimentary evolution and paleoclimatic significance of these poorly exposed deposits often remain largely unexplored. Here we present a suite of high-resolution x-ray fluorescence (XRF) core scanning data from southern Germany covering the Upper Toarcian and Aalenian stages. The overall objective of this study is to identify Transgressive-Regressive cycles based on the analysis of three cores obtained during scientific drilling campaigns in 2019-2021. Cores have been analyzed with an Avaatech XRF Core Scanner at a 10 mm sampling interval, an energy of 10 keV and a current of 500 µA to measure element intensities ranging from aluminium through iron. Resulting trends in elemental ratios indicative for subtle grain-size variations such as Si/Al are used to reconstruct shoreline trajectories and establish a sequence stratigraphic framework (see Thöle et al. 2020). Particularly the thick and largely homogenous Opalinuston Formation appears suitable in that respect, likely resulting from extraordinarily high sedimentation rates during the lower Aalenian in southern Germany, thus providing a complete but unexplored archive of paleoclimatic signals.

 

References:

Thöle, H., Bornemann, A., Heimhofer, U., Luppold, F. W., Blumenberg, M., Dohrmann, R., & Erbacher, J. (2020). Using high‐resolution XRF analyses as a sequence stratigraphic tool in a mudstone‐dominated succession (Early Cretaceous, Lower Saxony Basin, Northern Germany). The Depositional Record, 6(1), 236-258.

How to cite: Mann, T., Bornemann, A., and Erbacher, J.: A sequence-stratigraphic framework for the Toarcian – Aalenian from southern Germany based on x-ray fluorescence core scanning data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4877, https://doi.org/10.5194/egusphere-egu22-4877, 2022.

10:36–10:43
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EGU22-8150
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ECS
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Virtual presentation
Katharina Leu, Christian Zeeden, Thomas Wonik, Thomas Mann, Jochen Erbacher, and André Bornemann

From 2019 to 2021, three cores were drilled at different locations in the southern German Swabian Alb as part of the SEPIA project (Sequence Stratigraphy of the Aalenian in Southern Germany). They comprise sediments of 200 to 250 m length and are penetrating Lower and Middle Jurassic strata from the Pliensbachian to Bathonian stages (~ 190-166 Ma). The aim of this project is the development of a sequence stratigraphic model of the South German Basin at the transition from the Lower to Middle Jurassic time. Conclusions should be drawn towards the source area of the sediments as well as on the influence of sea level fluctuations on sedimentation.

Today, the Swabian Alb is a SW-NE trending mountain chain consisting of mainly carbonate rocks, and is one of the most distinctive regions in Germany where Jurassic strata is cropping out. During the middle Jurassic, Europe was almost completely covered by a shallow epi-continental sea including several small emerging areas or islands, located at latitudes about 15° lower than today. Southern Germany experienced predominant deposition of fine clastic sediments in a tropical climate. The most common sediments of this period are dark clays and oolithic ironstones, whereas condensation and discontinuity surfaces occur in many instances. Accommodation space for these sediments was not only generated by changes in sea level, but also by continuing subsidence of the area, explaining the inhomogeneous thickness and changes in facies of the sediments.

The geophysical downhole logging data of the stratigraphic record is used to develop a lithological classification and correlation of the boreholes sediments by the application of a cluster analysis to the data. Furthermore, the downhole logging data is used to perform cyclostratigraphy in selected intervals. The focus of the intervals chosen for cyclostratigraphy lies on the Aalenian stage, as this stage holds the most continuous and extended record in all three boreholes. Predicted timespans of these intervals yield similar results of ~800-1100 ka for all three boreholes and might provide a new benchmark for progressive improvement, especially for cyclostratigraphic analyses of the Lower Aalenian Opalinusclay Formation.

How to cite: Leu, K., Zeeden, C., Wonik, T., Mann, T., Erbacher, J., and Bornemann, A.: Litho- and cyclostratigraphy of the Aalenian Opalinusclay Formation in the Swabian Alb deduced from downhole logging data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8150, https://doi.org/10.5194/egusphere-egu22-8150, 2022.

10:43–10:50
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EGU22-4119
|
Virtual presentation
Cristian Victor Mircescu, Ioan I Bucur, and George Pleș

Carbonate deposits from the easternmost part of the Getic Carbonate Platform form good quality outcrops in the Postăvaru and Piatra Mare Massifs (Patrulius 1976). The average thickness of the carbonate succession reaches 400 m in these areas (Patrulius 1976). In the Postăvaru Massif, the Mesozoic succession consists of Upper Jurassic−Lower Cretaceous carbonate deposits which are covered by upper Albian−Cenomanian Conglomerates (Săndulescu 1964). In the Piatra Mare Massif, the carbonate succession comprises Callovian−Berriasian olistoliths which are embedded in the general mass of the upper Aptian Conglomerates (Săndulescu et al. 1972).

  We collected approximately 600 limestone samples from various sections, in the Postăvaru and Piatra Mare Massifs.

The following sections are located in the Postăvaru Massif: Valea Dragă, Drumul Albastru, Larga Mare, Vârful Postăvaru, Muchia Cheii-Trei Fetițe, Trei Fetițe-Poiana Secuilor, Trei Fetițe-Cabana Postăvaru.

Detailed sampling was performed in the Piatra Mare Massif, in the following sections: Bunloc Est, Bunloc Vest, Cariera Bunloc, Cheile Baciului, Cabana Piatra Mare, Valea Gârcinului, Șura de Piatră, Șura de Piatră-Vârful Piatra Mare, Piatra Scrisă, Coada Pietrei Mari, Șirul Stâncilor, Peștera de Gheață, Prăpastia Ursului and Tamina.

The following facies associations were identified: bioclastic intraclastic grainstone/rudstone, coral-microbial boundstone, packstone to floatstone with pelagic microfossils, bioclastic packstone-grainstone, peloidal oncoidic packstone-grainstone, bioclastic grainstone with black pebbles, wackestone with cyanobacteria nodules, fenestral wackestone, non-fossiliferous mudstone.

 

The micropaleontological association contains dasycladalean algae [Salpingoporella pygmea (Gümbel), Petrascula bursiformis Etallon, Aloisalthella sulcata (Alth), encrusting organisms [Bacinella type structures, Crescentiella morronensis (Crescenti), Koskinobulina socialis Cherchi & Schröder, Radiomura cautica Senowbari-Daryan & Schäfer, Perturbatacrusta leini Schlagintweit & Gawlick, Taumathoporella parvovesiculifera (Raineri)], foraminifera [Bramkampella arabica Redmond, Coscinoconus alpinus (Leupold), Coscinoconus delphinensis (Arnaud-Vanneau et al.), Coscinoconus sagittarius (Arnaud-Vanneau et al.), Frentzenella involuta (Mantsurova), Protopeneroplis striata Weynschenk, Protopeneroplis ultragranulata Gorbatchik] and pelagic microorganisms (Calpionella alpina Lorenz).

The identified microfacies types indicate that carbonate material was deposited in two distinct depositional settings. The first one includes slope to basin areas while the second one comprises inner platform depositional environments. The presence of abundant C. alpina and various representatives of the genus Coscinoconus (C. delphinensis, C. sagittarius) indicates that deposition continued in the area at least until the lower Berriasian.  

Acknowledgements

This work was supported by a grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P1-1.1-PD-2019-0456, within PNCDI III

 References  

Patrulius D (1976) Upper Jurassic−Lower Cretaceous carbonate rocks in the eastern part of the Getic Carbonate Platform and the adjacent flysch troughs. In: Patrulius D, Drăgănescu A, Baltreș A, Popescu B, Rădan S (eds) Carbonate Rocks and Evaporites-Guidebook. International Colloquium on Carbonate Rocks and Evaporites, Guidebook Series 15, Institute of Geology and Geophysics, Bucharest, pp 71-82

Săndulescu, M., 1964. Geological structure of the Postăvarul-Runcu Massif (Brașov Mountains) (in Romanian). Anuarul Comitetului Geologic, 34 (2): 382–422.

Săndulescu M, Patrulius D, Ștefănescu M (1972 a) Geological Map of Romania, scale 1:50 000, Brașov Sheet, 111 a (in Romanian). Institutul Geologic, București

How to cite: Mircescu, C. V., Bucur, I. I., and Pleș, G.: Upper Jurassic – Lower Cretaceous limestones from the easternmost Getic Carbonate Platform (Southern Carpathians, Romania). Microfacies, microfossils and depositional environments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4119, https://doi.org/10.5194/egusphere-egu22-4119, 2022.

10:50–10:57
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EGU22-8915
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ECS
|
Virtual presentation
Angana Chaudhuri, István Dunkl, Jan Schönig, Hilmar von Eynatten, and Kaushik Das

Sedimentary successions capture the history of geological features and events observable on present-day earth surface as well as those exposed earlier but currently buried or lost to erosion. The Mesozoic rocks in the Kutch Basin (western India) deposited between Middle Jurassic and Early Cretaceous reveal interesting provenance information on lost orogens and buried basins. The southwesterly sediment transport direction indicates north and northwest of the Indian subcontinent as the source area. Detrital zircon and monazite U-Th-Pb geochronology identify dominant sediment input from source rocks equivalent to the late Neoproterozoic Pan-African orogeny (500–650 Ma) along with substantial input from those equivalent to the Cambro-Ordovician Bhimphedian (aka Kurgiakh) (400–500 Ma) orogeny. All other contributing source rocks (ranging from 700 Ma to 3300 Ma) are traceable to the source area following the sediment transport direction. However, outcrops of crystalline rocks with zircon and monazite ages corresponding to the dominant age components are virtually lacking. Rocks equivalent to the Pan-African orogeny are found only as sparse isolated outcrops in the source area. In contrast, this orogeny is well reported from the southern granulite terrain (India), Madagascar, Seychelles and Eastern Africa. Therefore, considering the position of continents during the Mesozoic and the predominance of a 500–650 Ma sediment source in the Kutch Basin, the Pan-African orogenic belt possibly extends to north and north-western India. The current dearth of these outcrops suggests extensive erosion during the Mesozoic greenhouse climate and/or burial under the Deccan Flood Basalts. The other dominant source (400–500 Ma), equivalent to the Bhimphedian orogeny, currently reported as isolated outcrops in the Himalayan-fold-thrust belt (northern India) might have been disturbed and buried by thrusting during the Cenozoic Himalayan orogeny. This study also reveals a large gap of nearly 280 Ma between the youngest detrital zircon (458 Ma) and the depositional age (~170 Ma). This gap may be explained by (i) input of recycled sediment from an older basin, and/or (ii) absence of younger metamorphic events in the source area. The evidences of sediment recycling from thin-section petrography and ultra-stable heavy mineral assemblages (dominated by zircon, rutile and tourmaline) suggest the possibility of a so far unknown (buried or completely eroded) sedimentary basin older than the Kutch Basin. The on-going study of detrital rutile grains in these sediments may provide an alternative explanation for the 280 Ma gap by revealing lower temperature metamorphic events that are not recorded by U-Th-Pb ages of zircon and monazite.

How to cite: Chaudhuri, A., Dunkl, I., Schönig, J., von Eynatten, H., and Das, K.: Geochronology of sediments as a tool to identify lost geological features - a case study from the Mesozoic sedimentary succession of the Kutch Basin, western India, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8915, https://doi.org/10.5194/egusphere-egu22-8915, 2022.

10:57–11:04
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EGU22-12195
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Presentation form not yet defined
Pierre-Henri Blard, Baptiste Suchéras-Marx, Guillaume Suan, and Taous Mezine

Introduction

Marl-limestone alternations are well known rhythmical inter-bedded deposits that commonly occur in many hemipelagic to pelagic deposits of the Phanerozoic. It is quite well established that the origin of these lithological variations are astronomically-driven climatic variations (22, 41, 100 and 405 ka being the main periods) e.g. [1]. However, the exact sedimentological control is not clear: several models attribute these alternations to cyclic changes in the carbonate flux, whereas the terrigenous silicoclastic flux remained relatively constant. On the opposite, some models suggest that the carbonate flux was constant while the silicoclastic flux changed cyclically.

Material and methods

To disentangle these different scenarios, we collected marlstone and limestone samples from two sedimentary successions of Bajocian, Middle Jurassic (3 marl-limestone- couplets over 3.5 m) and Valanginian, Lower Cretaceous (1 marl-limestone couplet over 1 m) age from the Southern French Alps (Barles). We measured their carbonate contents, the nannofossil proportion, as well as their extraterrestrial 3He (3HeET) concentrations in ~200 mg decarbonated aliquots.

Results and discussion

The carbonate content ranges from 45% in marls to 86% in limestones. Importantly, for all samples, measured 3HeET concentrations are constant in the silicoclastic fractions, within uncertainties. Hence, our results indicate that sedimentation rates at the astronomical timescale in the examined examples were mainly controlled by large changes in the CaCO3 net fluxes, leading to variable dilution of the terrigenous and 3HeET fractions. Nannofossil counting shows that pelagic CaCO3 fluxes of coccolithophores are inversely correlated to the total CaCO3 along the marl-limestone alternations and represent less than 4% of the total carbonate content. Hence, in this setting, these marl-limestone alternations were more probably driven by variations in the CaCO3 supply from the nearby carbonate platform. Finally, assuming a constant 3HeET flux of 0.1 pcc/cm2/ka [2], and the whole thickness of Bajocian and Valanginian strata in this region, the measured 3HeET concentrations imply sedimentation rates that are broadly compatible with current duration estimates of these two stages.

 

References:

[1] Eldrett J. S. et al. (2015) Earth. Plan. Sci. Let., 423, 98-113.

[2] Farley K.A. et al. (2012) GCA, 84, 314-328.

How to cite: Blard, P.-H., Suchéras-Marx, B., Suan, G., and Mezine, T.: Extraterrestrial 3He shows that Mesozoic marl-limestone alternations are mainly driven by CaCO3 variations at the astronomical timescale, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12195, https://doi.org/10.5194/egusphere-egu22-12195, 2022.

11:04–11:11
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EGU22-2200
|
On-site presentation
André Bornemann, Jochen Erbacher, Martin Blumenberg, and Silke Voigt

High-amplitude shifts in sedimentary δ13C characterize the Cretaceous system and have been proven to be of great use for supraregional chemostratigraphic correlation. Here we present an upper Berriasian to lower Coniacian (c. 142 – 88 Ma) composite carbon isotope record based on 14 drill cores, two outcrops and almost 5000 samples. The total record comprises a composite thickness of about 1500 m. All cores and successions are located in the larger Hanover area, which represents the depocenter of the North German Lower Saxony Basin (LSB) in early to mid-Cretaceous times.

Boreal Lower Cretaceous sediments are predominantly represented by CaCO3-poor mud- and siltstones of up to 2000 m thickness in northern Germany, which become more carbonate-rich during the Albian-Cenomanian transition and even chalkier in the upper Cenomanian to Coniacian interval. A number of global carbon isotope key events including the Valanginian Weissert Event, the OAEs 1a, b and d (Aptian-Albian) as well as for the early Late Cretaceous the Mid-Cenomanian Event (MCE), the OAE 2 (Cenomanian-Turonian Boundary Event) and the Navigation Event, among others, have been identified allowing for a detailed comparison with Tethyan and other Boreal records. Thus, this new detailed chemostratigraphy provides a unique opportunity to potentially overcome many still existing Boreal–Tethyan correlation issues. The presented record can be considered to be almost complete, albeit a small gap in the early Albian cannot be ruled.

How to cite: Bornemann, A., Erbacher, J., Blumenberg, M., and Voigt, S.: A new Berriasian to Coniacian composite carbon isotope record from the Boreal Realm , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2200, https://doi.org/10.5194/egusphere-egu22-2200, 2022.

11:11–11:18
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EGU22-7766
|
Virtual presentation
Khaled Trabelsi, Anna Tamara Mai, Benjamin Sames, Jens O. Herrle, and Frank Wiese

A 55 meters thick section at Cuchia, Basque-Cantabrian Chain, North Spain, mainly formed by Lower Cretaceous Wealden facies, has been intensively investigated from the micropalaeontological viewpoint. The carbonate beds intercalated within this series yield a rich and diverse charophyte assemblages of high biostratigraphic interest, which could be studied for the first time after successful preparation following the acetolysis method.

Twenty-two charophyte taxa were identified forming two distinct charophyte assemblages belonging to two successive charophyte biozones. The first charophyte assemblage, from the lower part of the studied section, is composed of Echinochara lazarii, Atopochara trivolvis var. triquetra, Globator mallardii var. trochiliscoides, Clavator grovesii var. gautieri, Clavator harrisii var. dongjingensis, C. harrisii var. harrisii, C. calcitrapus var. jiangluoensis, C. calcitrapus var. calcitrapus, Ascidiella stellata var. stellata, A. triquetra, Hemiclavator neimongolensis var. neimongolensis, H. neimongolensis var. posticecaptus, Mesochara voluta gr. voluta and Favargella sp. According to Pérez-Cano et al. (2021), such a charophyte assemblage belongs to the new Eurasian “Hemiclavator neimongolensis var. neimongolensis” biozone, late early Barremian–early late Barremian in age as calibrated by Sr isotope stratigraphy and by correlation with marine biostratigraphy.

The second charophyte assemblage, which occurs in the upper part of the studied section is composed of the species E. lazarii, A. trivolvis var. triquetra, A. trivolvis var. trivolvis, C. grovesii var. jiuquanensis, C. harrisii var. dongjingensis, C. harrisii var. harrisii, C. harrisii var. reyi, Ascidiella cruciata, H. neimongolensis var. neimongolensis, H. neimongolensis var. posticecaptus, Mesochara voluta gr. voluta, Munieria grambastii, Clavatoraxis sp., Charaxis sp.  and Tolypella sp. vel. Mesochara sp. According to Pérez-Cano et al. (2021), such a charophyte assemblage belongs to the new Eurasian “Clavator grovesii var. jiuquanensis” biozone, late Barremian–early Aptian in age as calibrated by Sr isotope stratigraphy and by correlation with marine biostratigraphy.

As the overlaying succeeding limestones is early Aptian in age, our results allow constraining the chronostratigraphy of the Wealden series at Cuchia section to the late early Barremian– late Barremian, instead of Hauterivian–Barremian (Najarro et al., 2011) as previously thought, leading for a more detailed stratigraphic correlation of the Cuchia section to equivalent units of the Iberian plate, especially from the Iberian Chain and the Pyrenees.

References.

Najarro, M., Rosales, I., Martin-Chivelet, J. (2011). Major palaeoenvironmental perturbation in an Early Aptian carbonate platform: Prelude of the Oceanic Anoxic Event 1a. Sedimentary Geology 235, 50–71. https://doi.org/10.1016/j.cretres.2021.104934

Pérez-Cano, J., Bover-Arnal, T., Martín-Closas, C. (2021). Barremian–early Aptian charophyte biostratigraphy revisited. Newsletters on Stratigraphy (in press). DOI: 10.1127/nos/2021/0662

How to cite: Trabelsi, K., Mai, A. T., Sames, B., Herrle, J. O., and Wiese, F.: Charophyte biostratigraphy of the Lower Cretaceous (Wealden) Cuchia section, Basque-Cantabrian Chain, North Spain: Interest for regional stratigraphic correlation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7766, https://doi.org/10.5194/egusphere-egu22-7766, 2022.

11:18–11:25
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EGU22-10544
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ECS
|
Virtual presentation
Thomas Munier, Laurent Riquier, François Baudin, Armand Metgalchi, Sidonie Revillon, and Omar Boudouma

The Albian-Santonian interval (113-83 Ma) is considered as a transitional period between the Early Cretaceous times, marked by a succession of short climatic variations associated with volcanism episodes and the Late Cretaceous times, marked by a progressive decrease of temperatures. This 30 Myr-longed interval is characterized by a gradual increase of temperature in oceanic domain, which culminates during the Cretaceous thermal Maximum, at the end of the Turonian (~ 90 Ma). Although the evolutions of continental weathering and climatic conditions are well documented in oceanic domain of low to middle latitudes, especially in Atlantic and Tethyan oceans, their record are less well known in high latitudes, especially in the proto-Indian Ocean. Thanks to the Exp IODP 369, two new boreholes, U1512 and U1513, drilled respectively in the Bight Basin (Southern Australia) and in the Mentelle Basin (Southwestern Australia), provide the opportunity to study the Albian to Santonian deposits at high latitudes (~60°S). Cores of the site U1513 recovered a sedimentary sequence from Albian to Santonian whereas the site U1512 record a continuous sequence from Turonian to Santonian. An integrated study, coupling mineralogical determination (XRD analyse and SEM observation) and isotopic analyses of neodymium on clay fraction was done on both sites in order to determine climatic and weathering conditions in these southern high latitude zone.

Our study reveals that the clay fraction are dominated by smectites (>85% in average) with lower proportions of kaolinites (< 25%) and traces of illites (<5%) associated with opal-CT and clinoptilolites. SEM observations have demonstrated a negligible impact of both burial diagenesis and authigenesis on clay assemblage. They are thus interpreted as the products of the alteration of rocks and pedogenic blankets from adjacent landmasses. At Site U1513, the Albian clay fraction contains noticeable proportions of kaolinites (5 to 25%), which progressively decrease during the Cenomanian and disappear at the Cenomanian-Turonian boundary (~94 Ma). Turonian to Coniacian deposits are almost exclusively composed of smectites. The decrease in kaolinite proportions is coeval with a decrease in εNd values, which indicates a probable diminution in the erosion of Australian Archean rocks. At Site U1512, clay mineral assemblages, show slight variations along the borehole, which reflects stable weathering conditions during the 10 Myr of the Turonian-Santonian interval.

The dominance of smectites and to a lesser extent of kaolinites seem to indicate a warm to temperate and humid climate for high latitude zone during the Albian-Santonian interval. The decrease in kaolinite proportions from Albian to early Turonian in U1513 reflect probably a decrease of hydrolysis conditions associated with increasing temperatures and sea-level rise in southwestern Australian margins. The absence of noticeable variations from the Turonian to the Santonian in both sites would be the result of a stable continental climate for several million years after the Cretaceous thermal maximum (~ 90 Ma). The persistent presence of kaolinites in U1512 (southern Australia) could be due to the proximity of the Bight Basin with Australian Western Highlands.

How to cite: Munier, T., Riquier, L., Baudin, F., Metgalchi, A., Revillon, S., and Boudouma, O.: Continental weathering and climate conditions in southern high latitudes during the Albian-Santonian interval (U1512 and U1513 sites, Exp IODP 369, SW Australia), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10544, https://doi.org/10.5194/egusphere-egu22-10544, 2022.

11:25–11:32
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EGU22-11890
|
ECS
|
Virtual presentation
Michela Simonato, Silvia Gardin, Luca Giusberti, Valeria Luciani, Nereo Preto, Guido Roghi, Simone Barbieri, Federico Xausa, and Eliana Fornaciari

The late Cenomanian-Turonian interval is characterized by major changes in the global carbon cycle, identified by stable carbon isotope excursions with associated climatic variations (e.g., OAE2, Late Turonian Events). These changes are linked to significant paleoceanographic modifications that impacted the biota, especially primary producers (e.g., calcareous plankton), forcing extinctions and evolutionary radiations. A reliable biostratigraphy is an essential tool to correlate both environmental and biotic changes worldwide.

Calcareous nannofossils and planktic foraminifera are well recognized as useful markers for biostratigraphy and paleoecological studies. However, the Cenomanian-Turonian calcareous nannofossil biohorizons are still poorly constrained because the nannofossil assemblages suffer from marked provincialism and taxonomic uncertainty that can blur their biochronological potential.

In order to improve the calcareous nannofossil biostratigraphic scheme of the late Cenomanian-Turonian interval, we present new data from the Breonio section (northeastern Italy), in the southwestern part of the Trento Plateau, and from the Quero section (northeastern Italy), located in the western Belluno Basin (central-western Tethys).

The analyses of calcareous nannofossil and planktic foraminiferal assemblages were integrated with the δ13C, δ18O and CaCO3 curves. The δ13C values highlight several positive, global, stable carbon isotope shifts in both sections. The CaCO3 signal of the Quero section suggests that the isotopic signal is pristine because the CaCO3 values are not coupled with δ13C isotope shifts. On the contrary CaCO3 curve seems generally to reflect the lithological signal. On the basis of biostratigraphic data the detected positive shifts have been correlated with the late Cenomanian-Turonian events, specifically, the Oceanic Anoxic Event 2, Holywell, Round down, Pewsey, and Late Turonian Events 1, 2, 3. The stratigraphic position of biohorizons with respect to the globally recognized δ13C excursions can provide a valuable mean to evaluate their potential synchronism/diachronism.

Our preliminary data show a good correspondence with the recent calcareous nannofossil-planktic foraminiferal integrated scheme (Geologic Time scale 2020; Gale et al. 2020) for the late Cenomanian-Turonian interval, although some calcareous nannofossil markers were not recorded. Interestingly, some «standard» and additional calcareous nannofossil events are promising proxies for the Late Turonian Events 1 and 2.

 

References

Gale A.S., Mutterlose J. & Batenburg S. (2020). The Cretaceous Period, in Gradstein F.M. et al., eds., Geologic Time Scale 2020: Boston, Elsevier, pp. 1023-1086.

How to cite: Simonato, M., Gardin, S., Giusberti, L., Luciani, V., Preto, N., Roghi, G., Barbieri, S., Xausa, F., and Fornaciari, E.: Integrated calcareous plankton biostratigraphy and stable isotopes stratigraphy of Cenomanian-Turonian interval of Breonio and Quero sections (central-western Tethys), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11890, https://doi.org/10.5194/egusphere-egu22-11890, 2022.

11:32–11:42
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EGU22-4796
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solicited
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Virtual presentation
Nina M. Papadomanolaki, Niels A.G.M. van Helmond, Heiko Paelike, Appy Sluijs, and Caroline P. Slomp

Oceanic Anoxic Event 2 (ca. 94 Ma; OAE2) was one of the largest Mesozoic carbon cycle perturbations, but associated carbon emissions, primarily from the Caribbean large igneous province (LIP) and marine burial fluxes, are poorly constrained. Here, we use the carbon cycle box model LOSCAR-P to quantify the role of LIP volcanism and enhanced marine organic carbon (Corg) burial as constrained by the magnitude and shape of the positive stable carbon isotope (δ13C) excursion (CIE) in the exogenic carbon pool and atmospheric pCO2 reconstructions. In our best fit scenario, two pulses of volcanic carbon input—0.065 Pg C yr–1 over 170 k.y. and 0.075 Pg C yr–1 over 40 k.y., separated by an 80 k.y. interval with an input of 0.02 Pg C yr–1—are required to simulate observed changes in δ13C and pCO2. Reduced LIP activity and Corg burial lead to pronounced pCO2 reductions at the termination of both volcanic pulses, consistent with widespread evidence for cooling and a temporal negative trend in the global exogenic δ13C record. Finally, we show that observed leads and lags between such features in the records and simulations are explained by differences in the response time of components of the carbon cycle to volcanic forcing. 


How to cite: Papadomanolaki, N. M., van Helmond, N. A. G. M., Paelike, H., Sluijs, A., and Slomp, C. P.: Quantifying volcanism and organic carbon burial across Oceanic Anoxic Event 2 , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4796, https://doi.org/10.5194/egusphere-egu22-4796, 2022.

11:42–11:50
Lunch break
Chairperson: David Bajnai
13:20–13:27
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EGU22-11382
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Virtual presentation
Michael Wagreich and Ahmed Mansour

The Coniacian-Santonian was a time of strong differentiation in marine sedimentation, characterized by organic carbon-rich black shales and dark carbonates interpreted as the last oceanic anoxic event, OAE3, versus organic carbon-poor white/reddish limestones, chalk and claystones known as Cretaceous Oceanic Red Beds (CORBs). Based on compiled geochemical and isotope proxy data, two high-resolution global carbon isotope curves for carbonate and organic matter were reconstructed based on statistical analysis. Three main levels of short amplitude (around 0.5‰) carbon isotope excursions were identified. These excursions, each some 0.4 to 0.7 Ma in duration, were characterized by regionally restricted benthic anoxia and sea-level highstands that controlled regional organic matter accumulation during the OAE3 subevents defined herein as OAE3a (late mid-Coniacian, ca. 86.9 Ma, Kingsdown Event), OAE3b (late mid-Santonian, ca. 85.0 Ma, Horseshoe Bay Event), and OAE3c (late Santonian to Santonian-Campanian Boundary Event, ca. 83.5 Ma). Based on a compilation oxygen isotope temperature data and reconstructed pCO2 trends, the Coniacian-Santonian was characterized by: 1) a steady state phase of warm greenhouse climate during the Coniacian, followed by (2) a hot greenhouse during the early Santonian that might be consistent with activation of the Central Kerguelen large igneous province, and (3) a longer-term cooling of the warm greenhouse climate from the mid-Santonian onwards. Organic matter-rich deposition is largely restricted to the low-latitude Atlantic and adjacent epeiric and shelf seas. Areas of enhanced oceanic circulation systems with a westwards directed Tethyan current and regional eddies of water mass flow had a negative feedback resulted in well-developed water column oxygen content within the Tethys.

How to cite: Wagreich, M. and Mansour, A.: The Coniacian-Santonian Oceanic Anoxic Event OAE3 - global correlation of subevents, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11382, https://doi.org/10.5194/egusphere-egu22-11382, 2022.

13:27–13:34
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EGU22-7086
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ECS
|
Presentation form not yet defined
Iron speciation in southern Israel  phosphates: paleoenvironmental implications
(withdrawn)
Irina Zweig, Alexey Kamyshny, Nadya Teutsch, and Aya Schneider-Mor
13:34–13:44
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EGU22-5761
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ECS
|
solicited
|
On-site presentation
Sandra J. Huber, Vanessa Schlidt, Linus Lenk, H.-Michael Seitz, Jacek Raddatz, and Silke Voigt

The late Cretaceous climate is represented by an 8-10 °C decline of global mean temperatures that terminated global warmth of mid-Cretaceous times. Causal mechanisms of the cooling are still not well constrained and discussed in the interplay of reduced volcanic greenhouse gas emission and intensified silicate weathering as a global carbon cycle feedback. The lithium isotopic composition (δ7Li) of marine carbonates is a proxy for the chemical weathering intensity of silicate rocks, and thus provides information about the role of silicate weathering as thermostat and sink for atmospheric CO2.

Here, we present the first detailed chalk-derived Late Cretaceous δ7Li record (91-66 Ma) of the boreal white chalk in Northern Germany (Lägerdorf-Kronsmoor-Hemmoor) and from sections in southern England as archive for the seawater lithium isotopic composition. In the course of this study, we will also analyze the archives of skeletal calcite from brachiopods, belemnites and rudists, which should enable us to identify systematic offsets among different calcifiers related to vital effects by the direct comparison of fossilized shells and their surrounding sediments.

To handle the potential impact of clay contamination in bulk carbonates, we applied a pre-leaching and leaching procedure with 1 M ammonium acetate and 0.05 M nitric acid. The method was tested for a 1.85 Ma old sample of coccolith ooze from the Manihiki Plateau (equatorial West Pacific Ocean), which has consistent δ7Li values and shows a systematic negative 3-4 ‰ offset to modern seawater. In addition, the degree of potentially leached silicates is monitored by the analysis of E/Ca ratios, like Al/Ca.

In total, our late Cretaceous lithium isotope record shows a trend of rising δ7Li values between +16 and +25 ‰. Superimposed, the curve displays a rise in the Santonian, a local maximum in the early Campanian followed by a drop to a local minimum in the late Campanian. Subsequently, the δ7Li values rise again towards elevated values in the Maastrichtian. Overall, the shape of the δ7Li curve strongly resembles the evolution of deep-sea temperatures based on benthic oxygen isotopes suggesting a close link between climate and weathering. Thereby, more positive δ7Li values correspond to cooling periods and the late Campanian lowering of δ7Li values parallels the intermittent deep-sea warming. Such a pattern points towards a strong relationship between the congruency of silicate weathering and climate on a multi-million year time scale.

How to cite: Huber, S. J., Schlidt, V., Lenk, L., Seitz, H.-M., Raddatz, J., and Voigt, S.: Insights from the first detailed record of Late Cretaceous seawater lithium isotopic composition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5761, https://doi.org/10.5194/egusphere-egu22-5761, 2022.

13:44–13:51
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EGU22-465
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ECS
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Virtual presentation
Sangbaran Ghoshmaulik, Sourendra Kumar Bhattacharya, Manoshi Hazra, Pallab Roy, Mahasin Ali Khan, Mao-Chang Liang, and Anindya Sarkar

The intertrappean sediments and the bole beds of the Deccan volcanic province hold clues to the climatic condition in India during the Cretaceous/Paleocene transition. Earlier isotopic studies of the bulk clays from the ‘bole beds’ showed that the rainwater composition was lighter (δ18O  -8‰) relative to the present-day (δ18O ~ -5‰). This was ascribed to an increase in the rainfall (amount effect). However, later reconstruction of the mean annual precipitation (MAP) from the intertrappean paleosol carbonates suggested that the amount was no different than the modern-day precipitation. One possible reason for this disagreement can be due to the low preservation potential of proxies used in these studies. The present study was carried out by analysing authigenic silica which is resistant to post-depositional modifications. Such silica deposits are abundant throughout the Deccan intertrappean sediments occurring as cherts, chertified limestone and silicified fossils. They form during the interaction of silica-rich water with the existing sediments or fossils, the silica being derived by leaching of the volcanic ash by surface run-off and/or from siliceous hydrothermal waters. Silicified woods were analyzed for their triple oxygen isotope ratios (expressed as δ17O and δ18O) to determine the silicification temperature and the isotopic composition of the silicifying fluid. The distribution of the obtained silicification temperature and water composition of diverse samples indicates a widely variable silicification environment. The silicification took place at temperatures from 25°C  (near surface temperature)  to 90°C (at relatively shallower levels of 50-100 m). In addition, the δ18O (VSMOW) values of silicification fluid varied from -14‰ to near 0‰. The geological, floral and faunal evidence suggest deposition of these woods in a continental fluvio-lacustrine environment. Isotope modelling of the data suggest a two-component fluid mixing between hydrothermal water and a lake water. Assuming this fluid to be derived from a mixture of meteoric water and volcanic hydrothermal water, the δ18O value of the local meteoric water is estimated to be -14‰ to -12‰. These values are lower by about 9‰ to 7‰ compared to today (mean annual δ18O over central India being ~-5‰). We ascribe this to an increase in the mean annual rainfall by about 400 mm. It is possible that the late cretaceous precipitation increased due to the warming caused by a high CO2 environment.

How to cite: Ghoshmaulik, S., Bhattacharya, S. K., Hazra, M., Roy, P., Khan, M. A., Liang, M.-C., and Sarkar, A.: Evidence of high rainfall in India during Deccan eruptions based on triple oxygen isotope composition of petrified woods, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-465, https://doi.org/10.5194/egusphere-egu22-465, 2022.

13:51–13:58
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EGU22-4298
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ECS
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On-site presentation
Xinxuan Xiang, Michael Wagreich, and Erich Draganits

Climate-controlled sea-level rise and fall have important effects on the depositional processes of strata. During periods of widespread glaciation, climate cycles influence sea-level rise and fall by controlling ice sheet growth and melting. The Late Cretaceous period was characterized by a typical greenhouse climate, and evidence for the presence of ice is strongly debated. However, the sedimentary record shows short-term larger sea-level fluctuations, and there is growing evidence for aquifer-eustasy (Sames et al. 2020) as an additional mechanism controlling sea-level rise and fall during this period. Field observations, microscopic observations, and analytical studies on upper Santonian to lower Campanian coal-bearing strata of the Gosau Group in the Northern Calcareous Alps (Hofer et al. 2011) have led to the identification of marginal marine mixed carbonate-siliciclastic cycles. Coal layers and lacustrine fine-grained sediments are present and attest to continental sedimentation with raised groundwater table, whereas intermittent marine strata with foraminifera and calcareous nannoplankton give evidence for marine incursions and high sea-level intervals. In a frame of a University of Vienna project, such Upper Cretaceous coal-bearing cycles in European basins will be investigated in detail to infer regional and Tethyan-wide controlling processes on sea-level and groundwater-table.

How to cite: Xiang, X., Wagreich, M., and Draganits, E.: Investigating Greenhouse climate control on coal-bearing cycles in the Tethyan Upper Cretaceous Gosau Group (Northern Calcareous Alps, Austria), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4298, https://doi.org/10.5194/egusphere-egu22-4298, 2022.

13:58–13:59
13:59–14:06
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EGU22-4589
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ECS
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Virtual presentation
Veronika Koukal and Michael Wagreich

This study investigates the Paleogene deep-water depositional system of the Gosau Group at Gams, Styria (Austria). The examined sections of Danian to Ypresian age (NP1-NP12) comprise sediments of the Nierental and Zwieselalm formations. Four deep-water clastics facies assemblages were encountered, (1) carbonate-poor turbidites, (2) carbonate-rich turbidites, (3) marl-bearing turbidites and (4) a marl-dominated facies. Slump beds and mass flow deposits are common in all facies.

The examined sections predominantly consist of sandy and silty graded beds, including fine breccia layers at the base, to silty shales or claystones on top. Normal grading, lamination, amalgamation of sandy beds and bioturbation are characteristic for all sections. The thickness of sandstone beds varies strongly from only centimeters to several meters, but in general, sandy beds get thicker at sections dated at late Selandian age or younger. Within thinner beds Bouma Tbcd intervals are present. Thus, most sections contain sequences of thin to medium-bedded, fine-grained turbidites.

Based on heavy mineral, thin section, microprobe, and paleoflow analyses, provenance was from the surrounding Northern Calcareous Alps (NCA) rocks and exhuming metamorphic Upper Austroalpine units to the south. Provenance indexes based on heavy mineral assemblages indicate the dominance of an upper greenschist to lower amphibolite facies source of the investigated sediments. In addition, biogenic-calcareous material was delivered by adjacent contemporaneous shelf zones.

The sedimentary depocenter was situated at the slope of the incipient Alpine orogenic wedge, in frontal parts of the NCA, facing the subducting Penninic Ocean/Alpine Tethys. The evolution of the Gams Basin was connected to the eoalpine and mesoalpine orogeny, and the adjunctive transpressional setting. The Gams slope basin provided a fairly small depositional area and accommodation space on the incipient alpine orogenic wedge, and the pervasive tectonic deformation of the NCA destroyed and obscured important features of the formerly confined source-to-sink system. However, the Gams deep-water depositional system is interpreted as an aggrading or prograding submarine fan, deposited into a small confined slope basin, positioned along an active continental margin, bound and influenced by (strike-slip) faults, related to crustal shortening. The development of the Gams slope basin and its infilling sequences was mainly dominated by tectonism and sediment supply, rather than by eustatic sea-level fluctuations. General greenhouse conditions, with enhanced chemical weathering under seasonal conditions are assumed for the entire Gosau Group of Gams (Upper Cretaceous to Eocene), which enhanced erosion and facilitated a greater terrestrial sediment supply. Particularly an increased input of siliciclastics around the PETM is noticeable, including significant numbers of sandy turbidites. The basin was cut off during the Eocene due to renewed orogeny. A Quaternary analogue for the Paleogene basin setting of the Gams area is represented by the Santa Monica Basin in the California Continental Borderland.

How to cite: Koukal, V. and Wagreich, M.: The Paleogene Gosau Group of Gams slope basin of the incipient Eastern Alpine orogenic wedge (Austria), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4589, https://doi.org/10.5194/egusphere-egu22-4589, 2022.

14:06–14:13
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EGU22-4815
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ECS
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On-site presentation
Jorit F. Kniest, Amelia Davies, Jonathan A. Todd, Julia D. Sigwart, David Evans, Jens Fiebig, Silke Voigt, and Jacek Raddatz

The Eocene, as the warmest epoch during the Cenozoic, has received much attention as it can inform us about the features of global warmth, highly relevant to a “high-CO2” future. However, there is still a lack of knowledge regarding some key features of global warm climates, such as how higher global temperatures might have affected the duration and intensity of seasonality.  Furthermore, recognizing seasonal cycles is essential when interpreting proxy data and reconstructing paleo climate, e.g. in order to understand inter-annual bias between proxies. 

In the current study the seasonal variations in sea surface temperature (SST) and fresh water input into the Anglo-Paris Basin (subjacent areas of the Paleo-North Sea) was investigated. Marginal seas, like the Paleo North Sea, are an important intersection between the continental and marine realm, and are especially sensitive to short-term climate variations.

In order to resolve seasonal and perennial changes in SST and freshwater balance, we measured Ba/Ca, δ18O, and the clumped isotopic composition (∆47) of exceptionally well-preserved fossil molluscs. Although δ18O is commonly used for the reconstruction of temperature, its calculation often assumes a constant δ18O value of seawater, which might not be true on seasonal scales and/or within swallow marine basins. In this context, ∆47 was employed to determine the average temperature amplitude, due to its independence from δ18Oseawater. Additionally, Ba/Ca was used to account for periods with enhanced fresh water input, because barium mostly enters the oceans via fluvial systems and could therefor indicate seasonally enhanced and isotopic lighter fresh water input.            

The bivalve species Venericor planicosta was employed as proxy archive, due to its long life span (10-20 years) and its wide distribution in the Anglo-Paris Basin during the Eocene. The pristinely preserved, aragonitic bivalve shells were sampled by micro-milling (δ18O, ∆47), as well as, laser ablation (Ba/Ca), to generate proxy records with high temporal resolution.

The isotopic data reveal well pronounced seasonal oscillation with a sinusoidal shape and a maximum difference of 2‰, from -3,5‰ to -5,5‰. On average, the inter-annual variation of the δ18O record is around 1‰. The Ba/Ca record, on the other hand, shows a flat background with recurring large and sharp peaks. While the baseline Ba/Ca values are around 20 µmol/mol, the peaks can reach up to 300 µmol/mol. The peaks largely fall together with periods of depleted δ18O values. These results hint to a possible seasonal bias of temperature records in the Anglo-Paris basin based purely on δ18O, due to variable δ18O of seawater. This is further implied by the back-calculation of δ18Oseawater from ∆47 measurements, revealing a range from 2‰ to -4‰. 

How to cite: Kniest, J. F., Davies, A., Todd, J. A., Sigwart, J. D., Evans, D., Fiebig, J., Voigt, S., and Raddatz, J.: Eocene seasonality resolved by coupled Ba/Ca and stable oxygen isotope ratios in bivalve shells, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4815, https://doi.org/10.5194/egusphere-egu22-4815, 2022.

14:13–14:20
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EGU22-9745
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ECS
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On-site presentation
Heather Jones, Bryan Niederbockstruck, and Ursula Röhl and the IODP Expedition 378 Scientists

Carbon dioxide (CO2) emissions are rapidly rising leading to warmer oceans, surface ocean acidification, and complex changes in marine biogeochemical cycling. Calcareous nannoplankton: single-celled marine haptophytes, are likely particularly susceptible to such environmental changes, because they form microscopic plates made out of calcium carbonate (calcite). As these organisms lie at the base of the marine food web, it is critical that we understand how they respond to climate change over longer (millennial) timescales so that we can better predict the long-term effects of current and future environmental change on marine communities.

The high CO2 world of the early Eocene (~56 to 48 Ma) is characterized by multiple transient warming events (‘hyperthermals’), and is generally considered to be one of the best geologic analogues for future climate change. Here, we present preliminary, low-resolution calcareous nannoplankton assemblage data from the early Eocene of recently-drilled IODP Site U1553 (Campbell Plateau) in the South Pacific Ocean. Sediment cores recovered from Holes C and D at Site U1553 provide arguably one of the most complete and expanded early Eocene records yet from this relatively understudied region, including many of the previously recognized hyperthermals. This coupled with the high calcium carbonate content of the sediments, makes it an ideal case study for exploring millennial-scale changes in calcareous nannoplankton community composition and morphometry during transient warming events.

Within this presentation, we predominantly focus on the Paleocene-Eocene Thermal Maximum (PETM): the largest and best-studied of the early Eocene hyperthermals. Our results suggest that the turnover in nannoplankton species during this warming event was very similar to that observed at other southern high latitude sites such as Maud Rise. More minor ecological ‘jostling’ appears to have occurred prior to the onset of the PETM and following the event; however, the significance of these smaller changes in community composition have yet to be statistically analyzed at the time of writing. It is our aim to combine our assemblage counts with morphometric data to determine whether calcareous nannoplankton acted as a source or sink of carbon dioxide during the early Eocene hyperthermal events. We will also extend our dataset to include several of the smaller hyperthermals that succeeded the PETM, to elucidate whether calcareous nannoplankton exhibit a scaled or threshold response to warming.

How to cite: Jones, H., Niederbockstruck, B., and Röhl, U. and the IODP Expedition 378 Scientists: Calcareous nannoplankton community composition across multiple early Eocene hyperthermal events at International Ocean Discovery Program (IODP) Site U1553 (Campbell Plateau, SW Pacific), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9745, https://doi.org/10.5194/egusphere-egu22-9745, 2022.

14:20–14:27
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EGU22-6583
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ECS
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Virtual presentation
Loïc Marlot, Damien Huyghe, Justine Briais, Laurent Emmanuel, Mathieu Daëron, Christine Flehoc, Didier Merle, and Olivier Aguerre

During the Middle-Late Eocene, the Earth transitioned from a greenhouse to icehouse period. Within this period, a warming phase of 500 kyr called MECO (Middle Eocene Climatic Optimum) took place at the beginning of the Bartonian (from 40.5 Ma to 40 Ma - C18n). This event is characterized by a negative shift in the δ18O profile of benthic foraminifera associated with an increase of 4 to 6 °C in surface and deep ocean waters. The peak of the MECO is also characterized by a short δ13C negative excursion at 40.0 Myr during an overall increasing trend of δ13C. This positive trend of the δ13C curve appears to be related to an atmospheric increase in the pCO2, but the causes remains unclear.

Unlike the oceanic domain, few datas exist for the characterization of the MECO in coastal areas. Additionally, important component of the climatic context, such as the seasonal gradient of temperature, remain unknown. To unravel these uncertainties, this work focuses on the nearshore Eocene sedimentary records of the Paris Basin, which presents an important and remarkably well preserved paleobiodiversity of marine mollusk shells. Previous studies have confirmed that the MECO event is well recorded in Bartonian sediments, but due to several uncertainties, its stratigraphic position remains to be specified. Here we present a composite section that spans a stratigraphic interval covering the middle Lutetian (falunière de Grignon outcrop) and the Bartonian (Horizon de Mont-Saint Martin Formation, le Guépelle section and the Sables de Cresnes Formation). Thus, we combine different proxies provided by 18O, 13C and ∆47 analyses of marine mollusk shells sampled in these sections in order to clarify the stratigraphic position of the MECO in the sedimentary succession of the Paris Basin and to constrain the climatic expression of this hyperthermal event in shallow marine environment. 

Isotopic analyses were performed on the shells of 3 Bartonian mollusks species: 2 bivalves represented by Bicorbula gallica and Crassostrea cucullaris and 1 gastropod represented by Torquesia sulcifera. Stable isotope (δ18O and δ13C) results both show a characteristic negative excursion at the end of the Sables du Guépelle formation, in the lower part of the Bartonian. Clumped isotope analyses were performed on some specimens of B. gallica and T. sulcifera in order to better constrain the composition of δ18Ow throughout the stratigraphic interval studied. These results indicate significant decreases in local δ18Ow over the lifetime of most individuals, interpreted as large infra-annual variations in salinity. Paleotemperatures calculated from the previously constrained δ18Ocarbonate increase by 4 to 10 °C during the MECO event , while the seasonal temperature variation decreases from 11-13 °C to 8 °C during the negative isotopic excursion of the end of the Sables du Guépelle formation.

Based on these new results, we propose that the MECO is recorded in the top of the Sables du Guépelle formation marked by a warming period and a lower seasonal temperature gradient. These results lead to a better chimio-chronostratigraphic calibration of the Bartonian deposits of the Paris Basin.

How to cite: Marlot, L., Huyghe, D., Briais, J., Emmanuel, L., Daëron, M., Flehoc, C., Merle, D., and Aguerre, O.: Marine mollusk shells record the seasonal variations of temperature during the Mid Eocene Climatic Optimum in the Paris Basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6583, https://doi.org/10.5194/egusphere-egu22-6583, 2022.

14:27–14:34
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EGU22-4237
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On-site presentation
Joanna Pszonka and Marek Wendorff

The culmination of climate cooling at the Eocene-Oligocene boundary, known as the Terminal Eocene Event (TEE), forced the eustatic sea level fall crucial for isolation of the Paratethys from the Tethys Ocean. The isolated, northern marginal region contained starved Carpathian Flysch basins characterised by reduced circulation, dysaerobic bottom conditions and increased influx of riverine freshwater. The Cergowa Beds (Lower Oligocene) serve as an example of the icehouse period-related deposition of sandstones and subordinate sandstones-mudstones emplaced by sediment gravity flows in a predominantly anoxic depository dominated by dark shales and associated fine-grained facies of the Menilite Beds. Autochthonous calcareous nannoplankton species indicative of brackish water conditions reflect the Cergowa basin isolation and strong influence by freshwater influx during the zone NP23. This stage was dominated by high volume, high-density sediment gravity flows, occasionally triggered by hyperpycnal effluents. Coalified terrestrial organic matter, especially abundant in the proximal sector and including tree trunk fragments up to 2 m in length, suggests direct connection existed between the fluvial supply and redeposition by sediment gravity flows, probably via a shelf-edge delta supplying the Cergowa basin. The marginal character of the Cergowa basin enables to detect even subtle episodes as: (i) the CCD fluctuations, reflecting coccolithophorid-rich productivity, which is recorded as the laminated pelagic Tylawa Limestones, or (ii) local slope disequilibria reflected by hybrid flows interpreted as resulting from synsedimentary tectonic deformations of the basin floor. Generally, the Alpine orogenic movements enhanced the basin isolation and shoaling by tectonic uplift of the source area. However, the late stage of the Cergowa basin development, dated by the nannoplankton zone NP24, represents an open sea realm supplied by turbidity currents of decreasing density, with time suppressed and finally replaced by the anoxic sediments of the Menilite Beds type. Therefore, the deepening of the marine environment progressed against the prevailing global cooling and continuing eustatic sea-level fall. This apparent discrepancy emphasises the importance of the regional tectonic deformations of the basin that superseded the global climatic influence.

How to cite: Pszonka, J. and Wendorff, M.: Interplay of global climatic and regional tectonic controls in marginal basins, with an example of the Cergowa Beds deposition (Outer Carpathians) during the Oligocene icehouse, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4237, https://doi.org/10.5194/egusphere-egu22-4237, 2022.

14:34–14:41
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EGU22-11783
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ECS
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On-site presentation
Alessio Fabbrini, Ilaria Zaminiga, Thomas Ezard, and Bridget Wade

The taxonomy and phylogeny of the Miocene to Recent genus Sphaeroidinellopsis have been documented in previous studies, but the evolution of this lineage remains unclear. Some authors debated this genus in the past, choosing a variety of parameters to discriminate between morphospecies. Here we present new high detail analyses of specimens from Ocean Drilling Program (ODP) Site 925 (Ceara Rise, western equatorial Atlantic) and ODP Site 959 (Deep Ivorian Basin, eastern equatorial Atlantic). We present transitional individuals Sphaeroidinellopsis disjuncta–Sphaeroidinellopsis kochi, a speciation event never described before. These transitional specimens are characterized by extreme morphological features such as elongated and sac-like final chambers, requiring amendments to the current classification and taxonomy of these morphospecies. An alternative hypothesis is presented to assess these new observations within the evolutionary mosaic of Sphaeroidinellopsis.

How to cite: Fabbrini, A., Zaminiga, I., Ezard, T., and Wade, B.: A way-out from the maze of middle Miocene Sphaeroidinellopsis (planktonic foraminifera), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11783, https://doi.org/10.5194/egusphere-egu22-11783, 2022.

14:41–14:48
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EGU22-2260
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ECS
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Virtual presentation
Maria Elena Gastaldello, Claudia Agnini, Thomas Westerhold, Edoardo Dallanave, and Laia Alegret

The late Miocene-early Pliocene Biogenic Bloom was a significant event defined by the anomalously high marine biological productivity documented in the Indian, Pacific, and Atlantic Oceans; but its causes and consequences at different paleogeographical settings are not yet fully understood. Previous records from Ocean Drilling Program (ODP) Site 1085 (Cape Basin, Southeast Atlantic Ocean) indicate enhanced biological productivity between 7 and 4 Ma, as supported by increased linear sedimentation rates, benthic foraminiferal accumulation rates, and increased total organic carbon mass accumulation rates (Diester-Haass et al., 2002; 2004). To look into the paleoenvironmental consequences of the Biogenic Bloom, we investigated the benthic foraminiferal turnover at this site. Results were integrated with an age model based on a bio-astrocyclostratigraphic tuning and low-resolution carbon and oxygen stable isotope records on benthic foraminifera (i.e. Cibicidoides mundulus) across an interval spanning from the Tortonian (late Miocene) to the Zanclean (early Pliocene). Quantitative analyses of the assemblages and statistical analyses point to increased food supply to the seafloor. The proliferation of phytodetritus exploiting taxa such as Alabamina weddellensis and Epistominella exigua point to an episodic nutrient supply related to seasonal phytoplankton blooms during the Biogenic Bloom.

Reference

Diester-Haass, L., Meyers, P. A., & Vidal, L. (2002). The late Miocene onset of high productivity in the Benguela Current upwelling system as part of a global pattern. Marine Geology, 180(1-4), 87-103.

Diester-Haass, L., Meyers, P. A., & Bickert, T. (2004). Carbonate crash and biogenic bloom in the late Miocene: Evidence from ODP Sites 1085, 1086, and 1087 in the Cape Basin, southeast Atlantic Ocean. Paleoceanography, 19(1).

Acknowledgements

University of Padova DOR grant, CARIPARO Foundation Ph.D. scholarship.

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

How to cite: Gastaldello, M. E., Agnini, C., Westerhold, T., Dallanave, E., and Alegret, L.: The response of benthic foraminifera to the late Miocene-early Pliocene Biogenic Bloom: the record from Southeast Atlantic Ocean (ODP Site 1085), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2260, https://doi.org/10.5194/egusphere-egu22-2260, 2022.

14:48–14:50
Coffee break
Chairperson: David De Vleeschouwer
15:10–15:17
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EGU22-1042
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ECS
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Virtual presentation
Mark Baum

During the Messinian Salinity Crisis (5.97-5.33 Ma), evaporite deposition throughout the Mediterranean basin records a
series of dramatic environmental changes as flow through the Strait of Gibraltar was restricted. In the first stage of
evaporite deposition, cycles of gypsum appear in shallow basins on the margins of the Mediterranean. The complex
environmental history giving rise to these cycles has been investigated for decades but remains somewhat mysterious.
Notably, whether the evaporites are connected to significant changes in Mediterranean sea level is an open question.
In one proposed model, competition between tectonic uplift and erosion at the Strait of Gibraltar gives rise to self-sustaining
sea-level oscillations, or limit cycles, which trigger evaporite deposition. I show that limit cycles
are not a robust result of the proposed model and discuss how any oscillations produced by this model depend on
an unrealistic formulation of a key model equation. A more realistic formulation would render sea-level limit cycles improbable,
if not impossible, in the proposed model.

How to cite: Baum, M.: Limit Cycle Model of Messinian Salinity Crisis Incorrect and Irreproducible, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1042, https://doi.org/10.5194/egusphere-egu22-1042, 2022.

15:17–15:24
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EGU22-2053
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ECS
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On-site presentation
Francesco Pilade, Francesco Dela Pierre, Marcello Natalicchio, Iuliana Vasiliev, Daniel Birgel, Alan Mancini, Francesca Lozar, and Rocco Gennari

The Miocene-Pliocene transition (MPT) in the Mediterranean area represents one of the unresolved geological riddles of the Neogene. The MPT coincides with the end of the Messinian salinity crisis (MSC, Hsü et al., 1977), an event that led to the deposition of massive volume of evaporite on the Mediterranean seafloor. The final stage of the MSC started at ~5.53 Ma and its uppermost part corresponds to the “Lago-Mare” phase, characterized by the occurrence of brackish shallow water ostracods of Parathethyan origin. The “Lago-Mare” deposits are sharply overlain by Zanclean (earliest Pliocene) marine sediments, astrocronologically dated to start at 5.33 Ma (Van Couvering et al. 2000).

The interpretation of this abrupt environmental change is strongly debated. One scenario assumes a catastrophic flooding of all Mediterranean sub-basins that were previously disconnected from the Atlantic Ocean and from each other (Caruso et al., 2020). An alternative scenario invokes a gradual refilling started during the Lago-Mare phase and continued during the basal Pliocene (early Zanclean) (Roveri et al., 2008; Stoica et al., 2016; Merzeraud et al., 2018).

To investigate the paleoenvironmental conditions across the MP transition, we investigated six sections along a west to east transect of the Apennines foredeep, using an integrated approach that merge the traditional stratigraphic, palaeontological, geochemical, and petrographic data with the analysis of molecular fossils (lipid biomarkers).

The top of the Messinian sediments is marked by a bioturbated dark layer in all six studied sections. The presence of glauconite at the top of the dark layer and of firm ground burrows of the Glossifungites icnofacies filled with Zanclean sediments suggest starved sedimentary conditions and the partial lithification of the sea floor during the earliest Zanclean. In addition, the benthic foraminifera indicate an increase of bottom oxygen content and a deepening of the basin across the MPT. Preliminary results of over 40 samples indicate excellently preserved molecular fossils both in the “Lago-Mare” sediments and in the Zanclean open marine deposits with a predominance of terrestrially-derived higher-plants long chain n-alkanes (LCalk) and of glycerol dialkyl glycerol tetraethers (GDGTs) of both marine and terrestrial origin. Future analyses will focus on the compound specific carbon and hydrogen isotopes of LCalk to further constrain precipitation and vegetation changes associated to the MPT. Changes in seawater (via isoprenoidal GDGTs) and land temperatures (via branched GDGTs) will be also reconstructed.

How to cite: Pilade, F., Dela Pierre, F., Natalicchio, M., Vasiliev, I., Birgel, D., Mancini, A., Lozar, F., and Gennari, R.: THE END OF THE MESSINIAN SALINITY CRISIS IN THE MEDITERRANEAN: new data on the Miocene-Pliocene boundary., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2053, https://doi.org/10.5194/egusphere-egu22-2053, 2022.

15:24–15:31
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EGU22-9593
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ECS
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Virtual presentation
Udara Amarathunga, Andrew Hogg, Eelco Rohling, Andrew Roberts, Katharine Grant, David Heslop, Pengxiang Hu, Diederik Liebrand, Thomas Westerhold, Xiang Zhao, and Stewart Gilmore

5.33 Million years ago, a mile-high marine cascade terminated the Messinian Salinity Crisis due to partial collapse of the Gibraltar arc/sill that isolated a largely desiccated Mediterranean from the Atlantic Ocean. Atlantic waters may have refilled the basin within 2 years. Prevailing hypotheses suggest that normal marine conditions were established across the Mediterranean immediately after the catastrophic flooding. Here we use new proxy data and modelling to show that normal conditions were likely for the western Mediterranean (wMed), but that flooding caused massive wMed salt transfer to the eastern Mediterranean (eMed), which became a hyper-salinity-stratified basin. Hyper-stratification inhibited deep-water ventilation, causing anomalously long-lasting organic-rich (sapropel) sediment deposition. Model:data agreement indicates that hyper-stratification breakdown required 26,000 years. Testing an alternative hypothesis—reconnection of a largely refilled Mediterranean—reveals hyper-stratification in both the wMed and eMed, which would have left sapropels in both basins, in disagreement with observations. Our findings offer novel insight into the processes involved in re-establishing normal marine conditions following abrupt refilling of a previously desiccated ocean basin.

How to cite: Amarathunga, U., Hogg, A., Rohling, E., Roberts, A., Grant, K., Heslop, D., Hu, P., Liebrand, D., Westerhold, T., Zhao, X., and Gilmore, S.: Aftermath of catastrophic flooding of a desiccated ocean basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9593, https://doi.org/10.5194/egusphere-egu22-9593, 2022.

15:31–15:38
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EGU22-9934
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Virtual presentation
Mehrdad Sardar Abadi, Christian Zeeden, Arne Ulfers, and Thomas Wonik

Understanding the evolution of lower latitude climate from the most recent glacial periods of the latest Pleistocene to post glacial warmth in the continental tropical regions has been obstructed by a lack of long and continuous time series. Here we examine sediments from Lake Chalco, located in the Valley of Mexico, central Mexico (19°30’N, 99°W). The basin represents a hydrological closed system surrounded by the Trans-Mexican Volcanic Belt aging from the Oligocene to the present. We use borehole logging to conduct a cyclostratigraphic analysis of the Lake Chalco sediments, and incorporate other available dating information. More than 400 m of sediments are logged for several geophysical properties including magnetic susceptibility and spectral gamma radiation.

Gamma radiation can be used to identify elemental isotopes in the geological record, which is used for stratigraphic correlation and paleoclimatic investigations. Among the lake deposit of Chalco sub-basin, 388 total tephra layers (≥1 mm in thickness) were reported from the core description. Tephra layers with specific gamma ray signatures, presenting a challenge for extracting the primary signals caused by environmental and climatic agents. Here, we apply a tailored protocol to identify tephra layers embedded in other sediments using high-resolution gamma ray spectroscopy. This facilitates dividing the overall sediment column into representative horizons of tephra and non-tephra.

After extracting the non-volcanic primary signal, we apply a suite of evolutive cyclostratigraphic methods to the Lake Chalco logging data, with a focus on gamma ray data. The high-resolution results suggest that the Lake Chalco sediments contain several rhythmic alterations with a quasi-cyclic pattern comparable with the Pleistocene benthic stack. This allow us to calculate a ~500-kyr time span for the sediment deposition in Lake Chalco. By using cyclostratigraphic analysis on data captured by geophysical downhole logging, we demonstrate the potentially broad applicability of this method for downhole logging data and provide further insight into the sedimentation history of Lake Chalco.

 

 

How to cite: Sardar Abadi, M., Zeeden, C., Ulfers, A., and Wonik, T.: Downhole gamma ray data to reconstruct an age-depth model of the terrestrial record at Lake Chalco, Central Mexico, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9934, https://doi.org/10.5194/egusphere-egu22-9934, 2022.

15:38–15:45
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EGU22-7244
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Virtual presentation
Ruth Plets, Marc De Batist, Tine Missiaen, Maikel De Clercq, David Garcia, Thomas Mestdagh, Wim Versteeg, Simon Fitch, Rachel Harding, Vince Gaffney, Freek Busschers, and Sytze van Heteren

New high-resolution seismic data (Sparker) and very-high-resolution parametric echosounder (PES) data acquired in an area of the southern North Sea (the Flemish Bight) reveal its Quaternary seismic stratigraphy in unprecedented detail. The identified seismo-stratigraphic units and geomorphological features have been examined with the view to better understand the Quaternary evolution of the southern North Sea.

Seven acoustic units were recognised, including Lower Pleistocene deltaic sediments, Eemian to lower Weichselian shallow marine to coastal (lagoonal) clay-silt-sands, and Holocene coastal peat layers overlain by intertidal and marine sediments. Four erosional events were identified, two of which can be traced as regionally occurring surfaces, and two occurring as localised incisions. Mapping of geomorphological features revealed potential Elsterian moraines in the UK sector, an Elsterian ice-pushed ridge in the Dutch sector and possible permafrost-related structures (probably dating to MIS3).  Seven newly dated peat samples, acquired near a tidal sand ridge known as the Brown Bank from depths between 31 m and 34 m below sea level and dating to between 9.5 and 10.9 cal ka BP, indicate that this area was terrestrial during the early Holocene.

The results form the basis to further improve the regional Quaternary stratigraphic framework of the area, to better understand the region’s (de)glacial history, to enhance sea-level reconstructions and to examine the area’s geographical importance for human occupation during Prehistory.

How to cite: Plets, R., De Batist, M., Missiaen, T., De Clercq, M., Garcia, D., Mestdagh, T., Versteeg, W., Fitch, S., Harding, R., Gaffney, V., Busschers, F., and van Heteren, S.: Quaternary seismic stratigraphy of the Flemish Bight (southern North Sea): a re-evaluation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7244, https://doi.org/10.5194/egusphere-egu22-7244, 2022.

15:45–15:52
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EGU22-12
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ECS
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Presentation form not yet defined
Vikram Singh, Ashutosh Singh, and Devesh Sinha

The Western Pacific Warm Pool (WPWP) significantly affects the heat budget and associated climate over the Indian Ocean region. The reduction in the WPWP is manifested in the form of reduced Indonesian Throughflow (ITF) and may be well represented by the census count and oxygen isotope records of planktic foraminifera.

The present study is an attempt to reconstruct the episodes of reduction in the WPWP during the Quaternary, on the basis of extremely low relative abundance of planktic foraminifera Pulleniatina (Pu.) obliquiloculata from the ODP Hole 769B in the Sulu Sea. This species is a thermocline dweller, that thrives in tropical to warm subtropical latitudes. It is considered to be an indicator of Kuroshio Current and shows a direct correlation with the expansion of the WPWP.

In the ODP Hole 769B, Pu. obliquiloculata shows a low relative abundance during the Quaternary, except a few instances of significant increase, so much so that it comprises almost 50% of the entire faunal assemblage. The rising trend is characteristic of high SST and an expansion in WPWP. We have identified seven distinct events of sharp decline in the relative abundance of Pu. obliquiloculata (<5%) and named these events as Pulleniatina Minimum Events (PMEs). These events are: PME-1- (2.21-2.08 Ma); PME- 2 (1.8-1.36 Ma); PME- 3 (0.9-0.87 Ma); PME-4 (0.79-0.65 Ma), PME-5 (0.48-0.44 Ma), PME-6 (0.16-0.13 Ma) and PME-7 (0.04-0.02 Ma) in descending stratigraphic order. We interpret these events to mark be the result of the reduction in the WPWP. We have also found the occurrence of temperate fauna during the stratigraphically younger last five PMEs (PME7 to PME3), which indicate reduction in the Western Pacific Warm Pool (WPWP) probably caused by glaciations. The glacial events probably enhanced the Oyashio Current, which caused the influx of cool fertile waters in the Sulu Sea. The evidence of the increased fertility in the Sulu Sea is marked by the increased relative abundance of Neogloboquadrina dutertrei, a fertility indicator species, during the PME7 to PME3. The PME2 and PME1 show no presence of temperate fauna. These events of reduction in the WPWP may be attributed to the development of El Niño like conditions.

The PMEs were also correlated with the five PL events recorded by Sinha et al (2006) from ODP Hole 763A in the Eastern Indian Ocean. These PL events: PL-1- (2.22 Ma); PL-2 (1.83 Ma); PL-3 (0.68 Ma), PL-4 (0.45 Ma) and PL-5 (0.04 Ma), represented reduced strength of ITF either due to the glacial events (PL-3 to PL-5 events) or due to ENSO induced changes (reduction) in the WPWP (PL-1-and PL-2 events).

The PMEs show striking correlation with the PL events, giving testimony to episodes of reduction in the WPWP during Quaternary.

 

 

How to cite: Singh, V., Singh, A., and Sinha, D.: Pulleniatina Minimum Events from the Sulu Sea as evidence for Reduction in the Western Pacific Warm Pool during Quaternary, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12, https://doi.org/10.5194/egusphere-egu22-12, 2022.

15:52–15:59
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EGU22-10018
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ECS
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On-site presentation
Jasmin M. Link and Norbert Frank

The deep water formation in the Labrador and Nordic Seas is crucial for the global thermohaline circulation nowadays and it remains debated whether changing boundary conditions in terms of global warming may influence the deep convecting activity. Deep convection leads to the formation of Iceland Scotland Overflow Water (ISOW), which is an essential part of the lower limb of the Atlantic Meridional Overturning Circulation (AMOC). However, surface conditions in the Nordic Seas were unlikely always favorable for the formation of deep water in the past.

During Marine Isotope Stage (MIS) 11, a strong and active AMOC [e.g. 1] was reconstructed, which also contributed to the mass loss of the Greenland Ice Sheet [2]. However, cold and fresh surface conditions prevailed in the central Nordic Seas [3], which have been ascribed to freshwater input from the higher latitudes [4]. Thus, the question arises, whether and where deep water formation took place in the Nordic Seas.

Here, we reconstruct authigenic neodymium isotopes extracted from deep sea sediment from the Gardar Drift from 470 to 374 ka. IODP Site U1304 is located directly in the modern flow path of ISOW and should therefore sensitively track changes of this water mass in the past. Today, it is characterized by a strongly radiogenic neodymium isotopic composition, which markedly differs from other North Atlantic water masses.

Starting right at the onset and for the full length of the interglacial MIS 11c, a radiogenic Nd isotopic composition is switched on and prevailed indicating the presence of ISOW at the core site. More unradiogenic conditions indicate the return to glacial like conditions during a short event in MIS 11b. However, during MIS 11a the radiogenic values point again to a persistent presence of ISOW.

Thus, although the boundary conditions in terms of freshwater fluxes and sea level were significantly differing in the central Nordic Seas, the deep water formation presumably happened in the southern part of the Nordic Seas. This led to the active formation of ISOW, which in turn helped drive the active and strong AMOC during MIS 11.

 

[1] Dickson et al. (2009), Nat. Geosci. 2: 428-433.

[2] Rachmayani et al. (2017), Paleoceanography 32: 1089-1101.

[3] Kandiano et al. (2016), GRL 43: 10929-10937.

[4] Doherty and Thibodeau (2018), Front. Mar. Sci. 5: 251.

How to cite: Link, J. M. and Frank, N.: Persistent ISOW formation during MIS 11, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10018, https://doi.org/10.5194/egusphere-egu22-10018, 2022.

15:59–16:09
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EGU22-9308
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ECS
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solicited
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On-site presentation
Marleen Lausecker, Freya Hemsing, Thomas Krengel, Julius Förstel, Andrea Schröder-Ritzrau, Evan Cooper Border, Covadonga Orejas, Jürgen Titschak, Claudia Wienberg, Dierk Hebbeln, Anne-Marie Wefing, Paolo Montagna, Eric Douville, Lelia Matos, Jacek Raddatz, and Norbert Frank

The mean cooling of the global ocean during the Last Glacial Maximum (LGM) was recently estimated to 2.6°C using noble gases trapped in ice cores (1). The ocean, however, is highly heterogeneous with respect to its internal temperature varying both in latitude and water depth. While temperature changes in the deep ocean are small at about 2 - 3 °C (1,2), the upper ocean is more dynamic. Regional temperature anomalies of up to 7°C are predicted during the LGM compared to modern interior ocean temperature by global ocean circulation models (3). Due to the temperature drop to near freezing conditions and the global increase in salinity from ice sheet growth, the oceans’ deep interior became strongly haline stratified (2). Temperatures of the glacial ocean thermocline are, however, less well constrained.

Here, thermocline temperature reconstructions since the last glacial based on the Li/Mg ratio in cold-water coral skeletons are presented. The coral samples, collected from 300 - 1200 m water depths from different sites in the Atlantic (43°N to 25°S), reveal synchronous 5 - 7°C cooling during the last glacial period compared to today, as well as a dramatic shoaling of the thermocline. At the end of the LGM, warming of the upper thermocline ocean occurred early in the southern hemisphere followed by a fluctuating warming and thermocline deepening in the northern Hemisphere. This supports the oceanic climate seesaw proposed by Stocker and Johnson in 2003 (4). We thus propose dramatic changes in the export of polar waters towards the Equator and an enhanced subsurface ocean stratification leading to a mostly polar Atlantic with a shallow permanent thermocline during the glacial.

 

References:

1) Bereiter et al., Nature 553, 39-44 (2018).
2) Adkins et al., Science 298, 1769-1773 (2002).
3) Ballarotta et al., Clim. Past 9, 2669-2686 (2013).
4) Stocker and Johnsen, Paleoceanography 18, 1087 (2003).

How to cite: Lausecker, M., Hemsing, F., Krengel, T., Förstel, J., Schröder-Ritzrau, A., Border, E. C., Orejas, C., Titschak, J., Wienberg, C., Hebbeln, D., Wefing, A.-M., Montagna, P., Douville, E., Matos, L., Raddatz, J., and Frank, N.: Severe cooling of the Atlantic thermocline during the last glacial, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9308, https://doi.org/10.5194/egusphere-egu22-9308, 2022.

16:09–16:16
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EGU22-5602
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ECS
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Virtual presentation
Moritz Hallmaier, Eva M. Rückert, Jasmin M. Link, Laura Lütkes, and Norbert Frank

The deep Southern Ocean (SO) circulation is of major significance for the understanding of the ocean´s impact on Earth’s climate as uptake and release of CO­­­2 depend strongly on the redistribution of well and poorly ventilated water masses.

Neodymium isotopes preserved in deep sea sediment have proven useful to study the deep ocean circulation and water mass provenance thanks to basin scale isotope gradients between the Pacific and the North Atlantic. Here we present novel neodymium isotope data (εNd) of three sediment cores in 2.8, 3.3 and 3.6 km depth in the Atlantic sector of the SO to assess the presence of old and poorly ventilated Pacific sourced Deep Water (PDW) during the past 150 ka.

The sediment cores indicate dramatic temporal changes of εNd spanning a range of 7.7 ε-units from -1.0 to -8.3. While the εNd variability of the two deeper cores is driven by changes in ocean circulation, the shallowest drilling site is likely influenced by a local source of radiogenic Nd, such as weathering of volcanic material.

During peak glacial periods with maximum ice extent and a shoaled AMOC we observe radiogenic εNd values of ~-2.5 to -3.5. This confirms a predominance of glacial PDW at depths of >3 km with proportions close to 100% and thus increasing the water volume portion with enhanced respired carbon. We further advocate for the persistent presence of PDW even during interglacials although with a much smaller proportion.

Hence, our results enforce the leading role of the SO in storing and reinjecting respired CO2 into the deep Atlantic Ocean and the Atmosphere during glacial-interglacial terminations.

How to cite: Hallmaier, M., Rückert, E. M., Link, J. M., Lütkes, L., and Frank, N.: Dominance of Pacific Sourced Deep Water in the Atlantic sector of the Southern Ocean during the last glacials, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5602, https://doi.org/10.5194/egusphere-egu22-5602, 2022.

16:16–16:23
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EGU22-6605
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ECS
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On-site presentation
Arnau Blasco, Miguel Angel Calero, Valentí Rull, Núria Cañellas-Boltà, Sandra Garcés, Encarnación Montoya, and Teresa Vegas-Vilarrúbia

Over the last decades, significant increases in temperature and in the incidence of extreme climatic events have been registered in the Iberian Peninsula. Environmental changes  are easily recorded in high mountain lakes, due to their sensitivity and isolated location. Since paleolimnological information can be very useful for planning and modelling future climate change scenarios, it is necessary to find suitable lakes and test their sensitivity to current and past climatic shifts in order to adequately fulfill these tasks.

In order to test the suitability of the Bassa Nera pond as an indicator of global climatic change, this study aims to examine the variations of different  paleoindicators over the last 15,000 years. The variations of paleoenvironmental data can be then compared with the changes of different biological indicators (chironomids, diatoms, pollen), to find likely correlations that can be used to figure out future climatic scenarios and to provide information for environmental management.

For this study, a core of approximately 1,100 cm was extracted (PATAM 12-A-14) and dated with radiometric techniques. Sedimentological analysis was performed by applying conventional stratigraphic techniques and X-ray fluorescence methods. The variability of the sedimentary sequence allowed us to reconstruct the different climatic events. The pond recorded a long sedimentary sequence encompassing the last 15,000 years. The sedimentological analysis allowed us to establish 5 different stratigraphic units which we have separated in two principal sections. The first section is formed by organic rich facies while the remains of the core is composed mainly of clays and silts facies with some sand layers.

These data will be very useful to establish which and how past climatic events have affected this high mountain basin, when reconstructing the evolution of main paleolimnological indicators of environmental change. And in conjunction with subsequent studies, it will establish whether or not the suitability of the Bassa Nera as a sentinel of climatic global change. This in turn will allow the  establishment of a network of sentinel lakes in the Iberian Peninsula.

How to cite: Blasco, A., Calero, M. A., Rull, V., Cañellas-Boltà, N., Garcés, S., Montoya, E., and Vegas-Vilarrúbia, T.: The Bassa Nera pond (Central Pyrenees), a potential sentinel of climatic changes over the last 15,000 years., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6605, https://doi.org/10.5194/egusphere-egu22-6605, 2022.

16:23–16:30
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EGU22-3547
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Virtual presentation
Patrizia Macrì, Chiara Caricchi, Francesca D’Ajello Caracciolo, Alessio Di Roberto, Biagio Giaccio, Liliana Minelli, Iacopo Nicolosi, Bianca Scateni, Gaia Siravo, and Alessandra Smedile

The current “global warming” has been widely attributed to a human-induced greenhouse effect however, until the natural variability of climate is totally understood, it is extremely difficult disentangle the natural and human-induced climatic signal and the resulting effects in a short and long period. In order to understand the role that each component plays in the climate processes it becomes essential to acquire considerably longer records than the time it takes for them to undergo significant changes. The wealth of paleoclimatic information, and the improvement of our knowledge, relies on high-quality and high-resolution data availability, provided that these are anchored to accurate age models.

AMUSED (https://progetti.ingv.it/index.php/it/amused) is a project funded by the Istituto Nazionale di Geofisica e Vulcanologia aimed at reconstruct the climate variability in the central Mediterranean region during the middle-late Quaternary, with focus to the Holocene, by integrating paleoclimate multi-proxies data acquired from different paleoenvironmental settings. In detail, the project investigates lacustrine, speleothem and marine successions in central Italy at different temporal scales and resolution (i.e., from orbital to sub-millennial scale). Additionally, the project aims at the evaluation and reduction of the natural CO2 emission trough plantation of CO2-absorbing flora in the Colli Albani volcanic district.

The lacustrine sedimentary succession of the Castiglione maar (Colli Albani Volcano) that based on low-resolution previous studies should account for the last 280 kyr, has been selected as main continental target of the project. Intense Quaternary peri-Tyrrhenian volcanism, produced a large number of tephra that emplaced in the adjacent continental sedimentary basins, making this area suitable for the application of tephrochronology, useful for correlation and synchronization of geological records. Preliminary geophysical exploration surveys (electrical resistivity tomography and ground magnetic) were conducted across the Castiglione maar to reconstruct the subsurface structure and geometry of the basin and identify the best drilling site. Two parallel borehole (C1 and C2) were drilled in order to maximize the amount of recover and avoid large stratigraphic gaps. We retrieved 116 and 126,5 m of alternating sands, clay and silt sediments for drills C1 and C2, respectively. An additional core C3 has been afterwards located between the two boreholes, to increase the recovery of the upper 15 m of succession, strongly disturbed in the two former drills. Several tephra layers were already identified and sampled.

The sediment cores will be sampled for high-resolution multi-proxies analyses: stratigraphic, micropaleontological, palynological, geochemical (stable isotopic composition), and paleomagnetic. Moreover, a robust chronology for Castiglione records will be produced by combining 40Ar/39Ar dating of the tephra layers back to 280 kyr, and 14C dating within the last 45 kyr. In addition, a paleomagnetic chronostratigraphy will be derived, providing original target curves and an environmental magnetic investigation will be carried out, by using rock magnetic properties variations in sediments as environmental/climatic proxies.

How to cite: Macrì, P., Caricchi, C., D’Ajello Caracciolo, F., Di Roberto, A., Giaccio, B., Minelli, L., Nicolosi, I., Scateni, B., Siravo, G., and Smedile, A.: AMUSED: A MUltidisciplinary Study of past global climatE changes from continental and marine archives in the MeDiterranean region. The Castiglione maar drilling (central Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3547, https://doi.org/10.5194/egusphere-egu22-3547, 2022.

16:30–16:40