SSP2.1 | Integrated Stratigraphy - Reconstructing environmental change across the Earth System
EDI

Earth history is marked by significant disruptions in global climate, changes in geochemical cycling, and faunal turnover events. The investigation of these events across Earth history is based on accurate and integrated stratigraphy, utilizing a broad range of geological and geophysical techniques, unique stratigraphic morphologies, and established and novel paleoclimate and paleoenvironmental proxies. This session will bring together specialists in all branches of stratigraphy, paleoclimatology, paleontology, and paleoceanography, spanning from the Archean to the Holocene. The aim is to introduce new techniques and methods that help improve the stratigraphic and paleoenvironmental toolbox.

This session will emphasize sedimentary records that are particularly sensitive to climate variability and those that play a key role in global climate and environmental conditions through various feedback mechanisms. These records include sedimentary basins across latitudes, ice cores, mid- to high-latitude fjords that are global hot spots for the burial of organic carbon due to their unique morphology and processes that make them highly effective at trapping and preserving sediment, and sedimentary deposits that are actively affected by ocean circulation.

This session is organized by the International Subcommission on Stratigraphic Classification (ISSC) of the International Commission on Stratigraphy (ICS) and is open to the Earth science community at large.

Public information:

Professor Shu Gao

School of Geographic and Oceanographic Sciences

Nanjing University

shugao@nju.edu.cn

Convener: David De VleeschouwerECSECS | Co-conveners: Shu Gao, Kasia K. Sliwinska, Greer GilmerECSECS, Michele Rebesco, Jennifer M. Galloway, Andrew Gorman
Orals
| Thu, 27 Apr, 08:30–12:25 (CEST)
 
Room G1
Posters on site
| Attendance Thu, 27 Apr, 14:00–15:45 (CEST)
 
Hall X3
Posters virtual
| Attendance Thu, 27 Apr, 14:00–15:45 (CEST)
 
vHall SSP/GM
Orals |
Thu, 08:30
Thu, 14:00
Thu, 14:00

Professor Shu Gao

School of Geographic and Oceanographic Sciences

Nanjing University

shugao@nju.edu.cn

Orals: Thu, 27 Apr | Room G1

Chairpersons: David De Vleeschouwer, Kasia K. Sliwinska, Andrew Gorman
08:30–08:35
New stratigraphic approaches
08:35–08:45
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EGU23-1287
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SSP2.1
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ECS
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On-site presentation
Sébastien Wouters, Michiel Arts, Antonio Cicone, Michel Crucifix, Anne-Christine Da Silva, Niklas Hohmann, Matthias Sinnesael, and Christian Zeeden

Transparent data reporting is a crucial aspect of an integrated and reproducible stratigraphic approach. However, there is currently no set standard for doing so. Typically, lithological information can still be found as simple images in publications, rather than as importable vector graphics, or better yet, tabulated data. Another problem is that there is often confusion on stratigraphic depth, composite depth and interpreted age: there is no standard format for these parameters, and the way they are obtained is often difficult to replicate. This all impedes the compilation of published data into reliable stratigraphic databases. We suggest that standardised stratigraphic data formats and associated automated tests can solve this issue. We explore this in [1] the case of the quantified data contained in lithological logs, and in [2] age-depth conversion models, or depth-depth models for correlation between sections or for splicing.

We define three types of numerical data in lithological logs:

  • Bed nature and thickness (including thickness variations)
  • Bed profile (to convey hardness, weathering, grain-size, facies, etc.)
  • Discrete feature occurrences (e.g. fossils, minerals, sedimentary patterns)

These data types are not defined based on geological arguments, but on the way they are digitised. Respectively, these are interval data, continuous time-series, and discrete data. Therefore, three data sub-formats can be rigorously defined, and serve as building blocks for a larger single data format that would be comprehensive of all numerical data found in lithologs. Based on this, the existing StratigrapheR package has been updated (version 1.3): it now offers a formalised way of documenting these types of information for lithological logs in a quantified way. StratigrapheR is freely available for R at https://CRAN.R-project.org/package=StratigrapheR.

In StratigrapheR, discrete feature occurrences can be attributed to collections of symbols. Bed profiles can be formatted as time series, and “welded” to the side of lithologs. Layer content can be set as data tables for each bed, and can be illustrated by the colours or patterns of the beds in the litholog. Variations of thickness at the boundary of beds can also be “welded” to these beds in lithologs, as long as the variation does not interfere with the profile’s time series. Using a minimal set of formal rules, all these quantified data types can thus be standardised. We suggest that these concepts can be the basis for universal formats of numerical lithologs.

For age-depth and depth-depth conversion models, we explore the reversibility aspect, i.e., the ability to retrieve the initial signal from one that has been transformed, e.g., correlated, spliced, or tuned. This involves taking the precision in depth and age into account, as well as formalizing hiatuses, and preserving relevant features of the original data/signals in all subsequent data files, such as parts of the signal commonly removed for processing (e.g., turbidites).

How to cite: Wouters, S., Arts, M., Cicone, A., Crucifix, M., Da Silva, A.-C., Hohmann, N., Sinnesael, M., and Zeeden, C.: Set in stone ? Improvements in stratigraphic data processing and storage, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1287, https://doi.org/10.5194/egusphere-egu23-1287, 2023.

08:45–08:55
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EGU23-9637
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SSP2.1
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ECS
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Virtual presentation
Niklas Hohmann, Peter Burgess, and Emilia Jarochowska

The stratigraphic record preserves key information on past climate and evolutionary dynamics in the form of fossils and proxies. However, not all information can be recovered due to gaps in the stratigraphic record. It is challenging to assess (1) how strong the stratigraphic overprint of geohistorical data is (2) how it changes along an onshore-offshore gradient, and (3) how it is linked to external drivers of basin formation such as variation in sea level. Stratigraphic paleobiology has demonstrated how gaps distort reconstructed rates of evolutionary events and positions of stratigraphic markers in a non-random pattern. Yet a systematic evaluation of their effects on information reconstructed from strata is lacking.

We present DarwinCAT and ProxyCAT, two interactive web-based applications that visualize how stratigraphic architectures systematically change the expression of evolutionary history and proxy records. They combine simulations of a carbonate platform generated in CarboCAT with geohistorical records simulated in the R software into a Shiny app. They can be used in any web browser and require no installation or coding knowledge. In addition to simulations of trait evolution and proxy records, users can upload their own proxy data and examine its preservation in different parts of the carbonate platform.

Due to their strong visual component and interactive interface, the apps are an intuitive and easy to use tool for teaching, self study, and science communication. To facilitate their use for teaching, we provide predefined teaching units for undergraduate and graduate students of the geobiosciences. The teaching units allow exploring the preservation of geohistorical records within a stratigraphic framework, as well as hypothesis-driven research.

How to cite: Hohmann, N., Burgess, P., and Jarochowska, E.: Effects of gaps on proxy records and evolutionary history in carbonate platforms: interactive visualizations and teaching tools via R Shiny apps and CarboCAT, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9637, https://doi.org/10.5194/egusphere-egu23-9637, 2023.

08:55–09:05
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EGU23-16506
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SSP2.1
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ECS
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On-site presentation
A new approach to geochronology in very fine-grained sediments
(withdrawn)
Isabel C. Zutterkirch, Christopher L. Kirkland, Milo Barham, and Chris Elders
Quaternary
09:05–09:15
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EGU23-16352
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SSP2.1
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On-site presentation
William Austin, John Howe, Alix Cage, and Craig Smeaton

Rapid climate change (RCC) during the Holocene, particularly post-dating the demise of large Northern Hemisphere ice sheets after 8000 cal. yr BP, is a global phenomenon and is almost certainly driven by long-term changes in insolation, upon which solar variability, although a weak direct forcing mechanism, is superimposed. At least five significant intervals are identified in numerous palaeoclimate records since the major 9000-8000 cal. yr RCC, within which the intensively studied 8200 cal. yr ‘event’ is embedded; these are: 6000-5000, 4200-3800, 3500-2500, 1200-1000 and 600-150 cal. yr BP. Most of the Holocene RCCs are associated with bipolar cooling, an expansion-intensification of high latitude circulation systems and drying-aridity at low latitudes.

Here, we present proxy-records from a fjord basin located on the Atlantic margins of NW Europe which contain evidence for these combined forcing mechanisms. Giant piston core (MD04-2832) from the main basin of Loch Sunart, Argyll, NW Scotland, is 22 m long and appears to contain a record of continuous sedimentation back to nearly 8000 cal. yr BP. Based upon the age-depth model for core MD04-2832, isotopic shifts recorded in the benthic foraminifera Ammonia beccarii coincide with both the rate and magnitude of the Holocene RCCs. We show that the renewal history of bottom waters in the fjord basins appear to be driven by large-scale atmospheric circulation changes that may have characterised the entire mid-latitude NE Atlantic region.

How to cite: Austin, W., Howe, J., Cage, A., and Smeaton, C.: Holocene Rapid Climate Change: Pervasive Millennial-Scale Climate Variability across the North Atlantic, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16352, https://doi.org/10.5194/egusphere-egu23-16352, 2023.

09:15–09:25
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EGU23-7222
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SSP2.1
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ECS
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Virtual presentation
Changxun Yu, Mats Åström, Susan Nehzati, and Richard Gyllencreutz

Late Quaternary marine sediments in the central parts of the Arctic Ocean are characterized by recurrent brownish Mn-rich layers that are often strongly bioturbated and rich in micro- and nanno-fossils, and are thus believed to be deposited during interstadial/interglacial periods[1]. Since the brownish Mn-rich layers are widespread and easy to identify, they have been used as stratigraphic tools to correlate past climate events recorded by existing sediment cores across the central Arctic Ocean. Although these Mn-rich layers were assumed to contain abundant Mn oxyhydroxide phases[1,2] and reported to undergo slow but increasing diagenetic processes with depths[2], the geochemical nature of these Mn phases and their responses to long-term diagenesis have not been examined on a molecular level. Here, we sampled a large number of thin sediment layers (representing different stratigraphic levels with varying Mn XRF counts) of six cores from different parts of the central Arctic Ocean, and investigated the speciation and average oxidation state (AOS) of Mn in these layers by synchrotron-based Mn K-edge XANES and EXAFS spectroscopy. By linking to the sedimentological/geochemical features (e.g., bulk density, abundances of benthic and planktic communities, micro-XRF profiles) of the same cores, the synchrotron data revealed that (i) Mn pools in nearly all of the sediments (including those deposited recently as well as during the past glacial/interglacial periods) were strongly dominated by phyllomanganate phases, structurally similar to vernadite (a common product of bacterially-mediated Mn oxidation); (ii) the structural alterations of the vernadite-like phases (e.g., the splitting of Mn-O and Mn-Mn inter-atomic distances) in the cores were correlated inversely to the values of Mn AOS, suggesting an active and gentle diagenesis-driven Mn reduction processes; and  (iii) the sediment layers with lowest Mn XRF counts overall had lowest values of Mn AOS, but displayed no sign of other Mn phases. The sediments will be analyzed for total concentrations of Mn and other elements as well as labile and recalcitrant organic matter (via ramped combustion-evolved CO2 gas analysis). By combining with the additional data (e.g., Co/Mo ratios and availability of labile organic matter), this study will provide new insights into the key factors regulating the deposition and diagenetic alterations/redistribution of Mn in the sediment cores. This will, in turn, add important constrains on the geo-stratigraphic occurrence and diagenetic processes of the Mn-rich layers as well as the interpretation of linked Nd isotopes (important tracers for past water mass) and other biogeochemical processes (e.g., carbon and nutrient cycling) in the central Arctic Ocean during the glacial-interglacial climate cycles.

 

References

[1] Löwemark. L., et al. (2014) Quaternary Science Reviews, 92, 97-111.

[2] März. C., et al. (2011) Geochimica et Cosmochimica Acta, 75, (23), 7668-7687.

How to cite: Yu, C., Åström, M., Nehzati, S., and Gyllencreutz, R.: Partial reduction and associated micro-structure alterations of vernadite-like phases in central Arctic sediments: new constrains on Mn stratigraphy and early-diagenesis in the Arctic Ocean, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7222, https://doi.org/10.5194/egusphere-egu23-7222, 2023.

09:25–09:35
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EGU23-2416
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SSP2.1
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ECS
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Virtual presentation
Dmytro Hlavatskyi, Oleksandr Bonchkovskyi, Volodymyr Bakhmutov, Natalia Gerasimenko, Ievgen Poliachenko, Viktor Shpyra, Semen Cherkes, Illia Kravchuk, and Sergii Mychak

The north-western shore of the Black Sea is represented by thick (30-45 m) and stratigraphically complete Quaternary loess-soil sequences. The Sanzhiyka site recorded a continuous sediment accumulation throughout the past 900 ka: each soil unit has a thickness of 2.5 m, whereas loess units are much thinner, with the exception of the 5 m thick Dnipro (S-L2, MIS 6) loess. We present palaeopedological, rock magnetic and palaeomagnetic results of the upper 19 m of the section from the Lower Zavadivka unit (S-S4, MIS 11) to the Holocene.

Each pedocomplex in the section comprises several soils separated by thin loess beds, or by levels from which wedges penetrate downward. According to the soils’ morphogenetic features and micromorphology, the majority can be attributed to those formed under steppe vegetation. However, the Lower Zavadivka (S-S4) soil unit is presumed to have formed in a rather humid climate, as evidenced by occasional clay coatings and indications of strong carbonate leaching. Furthermore, the S-S4 soils are rubified and weakly gleyed. The Upper Zavadivka (S-S3, MIS 9) soil unit comprises four soils (Chernozems and Cambisols), heavily bioturbated in their lower parts. A subangular blocky and crumby microstructure dominate, and gypsum pedofeatures appear. The Bk horizons of each soil are superimposed on the underlying soils; however, thin sections show signs of primary carbonate leaching. The Potyagaylivka (S-S2, MIS 7) soil unit consists of three soils, two upper soils, which are weakly rubified and have pronounced crumby microstructure. Despite the fact that the lower soil was  strongly altered by subsequent pedogenesis (secondary carbonate accumulation), the signs of primary carbonate leaching and chemical weathering are recognisable. The S-S1 (MIS 5) soil unit comprises the lower Chernozem (Kaydaky subunit) and two upper brown soils, similar to Calcisols (Pryluky subunit). The Kaydaky soil is noticeably leached of carbonates, and numerous krotovinas occur in its subsoil. In the Pryluky soils, abundant coprolites and biogenic channels occur. Similar features are characteristic of the soils in the Vytachiv unit (S-L1S1, MIS 3).

Magnetic susceptibility increases significantly in palaeosols, showing initial, 1-2 optimum, and final phases of pedogenesis in each pedocomplex. Variations in the magnetic susceptibility curve are clearly comparable to marine isotope subtages, for instance two peaks in the Upper Zavadivka (S-S3) soil unit and the Potyagaylivka (S-S2) soil unit are correlated with those of the marine substages of MIS 9 (‘a’ and ‘c­-e’) and MIS 7 (‘a-c’ and ‘e’), respectively. Rock magnetic results indicate the presence of magnetite with a contribution of superparamagnetic grains. Palaeomagnetic analyses confirms the deposition of the studied interval during the Brunhes chron. Magnetostratigraphic study of the lower part of the section aiming at the determination of the Matuyama/Brunhes boundary is currently in progress. Issues of the Quaternary stratigraphy and chronology of loess in southern Ukraine are discussed in detail.

The study was supported by the National Research Foundation of Ukraine, grant number 2020.02/0406, and by the National Science Center, Poland, research project no. UMO-2022/01/3/ST10/00033 (V. Bakhmutov).

How to cite: Hlavatskyi, D., Bonchkovskyi, O., Bakhmutov, V., Gerasimenko, N., Poliachenko, I., Shpyra, V., Cherkes, S., Kravchuk, I., and Mychak, S.: Pedo-, magneto- and rock magnetic stratigraphy for the late Middle-Upper Pleistocene interval of the Sanzhiyka loess-palaeosol sequence in southern Ukraine, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2416, https://doi.org/10.5194/egusphere-egu23-2416, 2023.

09:35–09:45
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EGU23-3859
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SSP2.1
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On-site presentation
Christian Huebscher and Dirk Nuernberg

At the beginning of the Mid-Pleistocene Transition (MPT) ~920 ka BP the northern hemisphere ice shields expanded, causing a significant climate change in NW Europe. Previous studies explained the northern hemisphere cooling by cooling of sea-surface temperatures, increased sea-ice cover and/or changes in the Atlantic Meridional Overturning Circulation (AMOC) strength.

In their recent study Hübscher and Nürnberg (2023) discuss very-high resolution parametric echosounder imagery and sediment core analytics from a plastered drift at the eastern Campeche Bank (southern Gulf of Mexico), which was deposited under the influence of the Loop Current (LC). The LC transports warm tropical waters from the Caribbean into the Gulf via the Yucatan Channel. After its outflow into the Atlantic this warm water is a key component of the Gulf Stream system, driving the ocean heat, salinity, and moisture transport towards the N Atlantic. The joint interpretation of reflection patterns, age constraints from color-scanning, foraminiferal stable oxygen isotopes, Sr isotope ratios and core-seismic integration provides a clear line of evidence that LC strength changed across the MPT, thereby modulating the deep base level and the deposition of the plastered drift. The development of offlapping or onlapping plastered drifts is explained by changes in the depth of the relative deep base level due to changes in the flow regime.

The Middle Miocene to Pliocene closure of the Central American Seaway caused the onset and intensification of the LC, a deep base level fall and deposition of offlapping prograding clinoforms similar to forced regression systems tract as usually recognized  from shelf areas. The deep base level fall caused sediment truncation above 500 m present day water depth. Below 500-550 m, the offlapping succession is overlain by sigmoidal and onlapping, transgressive systems tract like clinoforms. The transition from deep base level fall prior to the MPT to deep base level rise documents the weakening of the LC during the early MPT. After the MPT, the LC continued to weaken. The related reduction of heat transport from the Western Atlantic Warm Water Pool into the North Atlantic contributes to the further cooling of the northern hemisphere. Generally, the development of offlapping or onlapping plastered drifts or the transition between the two termination patterns can be explained by changes in the depth of the relative deep base level and interpreted by changes in the flow regime.

 

Hübscher, C., Nürnberg, D., 2023. Loop Current attenuation after the Mid-Pleistocene Transition contributes to Northern hemisphere cooling. Marine Geology 456, https://doi.org/10.1016/j.margeo.2022.106976

How to cite: Huebscher, C. and Nuernberg, D.: Seismic and geologic data from southern Gulf of Mexico imply a weakening of the Loop Current since the Mid Pleistocene Transition   , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3859, https://doi.org/10.5194/egusphere-egu23-3859, 2023.

Neogene
09:45–10:05
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EGU23-5547
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SSP2.1
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ECS
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solicited
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Virtual presentation
Amy I. Hsieh, Romain Vaucher, Ludvig Löwemark, Chorng-Shern Horng, Andrew T. Lin, and Shahin E. Dashtgard

Changes in Earth’s eccentricity, obliquity, and precession can cause quasi-cyclic variations in Earth’s climate that may be preserved in sedimentary archives. Recent research has shown that shallow-marine paleoclimate archives in mid- to low-latitude regions have the potential to preserve changes in hydroclimate driven by precession, given sufficient space for sediment accumulation and a high sedimentation rate. Our integrated stratigraphic study of the Kueichulin Formation in Taiwan’s Western Foreland Basin (WFB) uses magnetostratigraphy, biostratigraphy and astrochronology to constrain time, with the aim to assess how the evolution of a rapidly uplifting mountain range affected the preservation of climate cycles in the shallow-marine record.

Using time-series analysis of two sets of gamma-ray borehole data from the late Miocene to Pliocene Kueichulin Formation (WFB), we found that despite increasing monsoon intensities between 8 and 3 Ma, the preservation of precession-driven East Asian Summer Monsoon variability was low during the early stages of Taiwan orogenesis (before 5.4 Ma). Prior to 5.4 Ma, the Taiwan Strait had not yet formed. Consequently, the southeastern margin of Eurasia was open to the Pacific Ocean, and so the depositional environments in the WFB were susceptible to reworking by large waves. This led to the preservation of low-frequency eccentricity and obliquity, but not higher-frequency precession.

Despite increasing basin subsidence from 5.4 to 4.9 Ma, the preservation of orbital oscillations is low. This is attributed to either low sedimentation rates at deeper water depths, which could obscure variations in sediment input or result in cycles below the resolution of the gamma-ray logging tool, or cycles not being detectible in the gamma-ray proxy record due to a lack of contrasting lithology. After 4.9 Ma and up to 3.2 Ma, the Taiwan orogen became the dominant sediment source for the WFB, and rapid growth of the orogen shielded the WFB from high-energy waves generated in the Pacific Ocean. The increased sediment influx and the formation of a semi-sheltered strait, combined with increased space for sediment accumulation in the WFB, resulted in enhanced preservation of precession-driven East Asian Summer Monsoon variability.

How to cite: Hsieh, A. I., Vaucher, R., Löwemark, L., Horng, C.-S., Lin, A. T., and Dashtgard, S. E.: Using integrated magnetostratigraphy, biostratigraphy, and astrochronology to evaluate the impacts of a rapidly uplifting orogen on the preservation of climate oscillations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5547, https://doi.org/10.5194/egusphere-egu23-5547, 2023.

10:05–10:15
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EGU23-5559
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SSP2.1
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ECS
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On-site presentation
Felix Hofmayer, Beatriz Hadler Boggiani, Stjepan Ćoric, Rohit Soman, Juan David Andrade, and Bettina Reichenbacher

Observed paleoenvironmental fluctuations in the North Alpine Foreland Basin, as one of the largest sedimentary archives of the Oligocene and Miocene are mainly controlled by regional factors. Global climate signals are usually less prominent than local tectonics and sedimentary input, caused by the enclosed paleogeographic setting of the Paratethys. Moreover are stratigraphic concepts still under debate, disabling a precise correlation of observed regional environmental changes to global climate patterns. In this study, a multi-proxy approach is used to achieve an accurate chronostratigraphy of regional formations and to verify whether global signals can be detected in the North Alpine Foreland Basin. Therefore, a detailed paleoenvironmental and biostratigraphic study of an 18 m-thick section of marine Miocene deposits (Neuhofen Formation) was carried out, using micropaleontology, sedimentology and geochemistry. In total 39 samples, yielding 68 foraminifera species and 47 ostracod species were processed together with 32 nannoplankton samples. Additionally, 34 ostracods and 49 benthic foraminifera were used for the analysis Oxygen and Carbon isotopes. Furthermore, 50 samples of six different sites in the Neuhofen Formation were used for statistical analyses of benthic foraminifera to assess supra-regional environmental correlations. Finally, the chronostratigraphic concept of the Neuhofen Formation was revised using magnetostratigraphic data from four sections, nannoplankton biostratigraphy and Sr-Isotope stratigraphy from previous studies as well as 3D-modelling using previous data additionally to 29 drillings. For the hypothesis that regional environmental patterns are correlating with global climate signals, environmental indices of the Neuhofen Formation (Isotopes, Diversity, Infaunalisation, Abundancy) were compared with global isotope values and Milankovic Cycles. The new stratigraphic concept of the Neuhofen Formation yielded an age of 18.1 – 17.6 Ma with a depositional time of 500,000 years. It was shown by a cluster analysis that strong faunal differences exist between the single localities, indicating separate paleoenvironments. These environmental differences are rather caused by regional factors. Occasionally, e.g. at 17.67 Ma, throughout the deposition of shallow marine sediments in the Neuhofen Formation the influence of global climate change can be inferred.

How to cite: Hofmayer, F., Hadler Boggiani, B., Ćoric, S., Soman, R., Andrade, J. D., and Reichenbacher, B.: An integral way to stratigraphy – Are there global climate signals in the North Alpine Foreland Basin?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5559, https://doi.org/10.5194/egusphere-egu23-5559, 2023.

Coffee break
Chairpersons: Kasia K. Sliwinska, David De Vleeschouwer, Jennifer M. Galloway
Paleogene
10:45–11:05
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EGU23-12414
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SSP2.1
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solicited
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Highlight
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On-site presentation
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Maria Ansine Jensen, Mads Jelby, Malte Jochmann, and Chris Marshall

The polar regions are particularly sensitive to modern climate change. Despite the Arctic being home to isolated societies and vulnerable ecosystems, little is known about landscape and ecosystem response to climate change beyond short historical records. The Paleogene - Eocene near-shore to continental record from the Central Tertary Basin (CTB) of the Svalbard archipelago provides a unique laboratory in which to study surface response to temperature and precipitation change during hyperthermals. At the time Svalbard was located in the high Arctic at c.75 degrees north and had a polar night and no night during summers. This time interval was a period of high atmospheric CO2 levels and a warm greenhouse climate and the best existing analogue for projected near future warming.C-isotopes has been obtained from across the PETM (Cui et al., 2011; 2021), and glendonites (Spielhagen & Tripati 2009) and leaf morphologies (Clifton 2012) has provided evidence of cold- and warm spells after the PETM. Ongoing work by the authors and collaborators have shown the possibility to obtain high resolution paleoclimate records (precipitation, atmospheric dust/wind, forest fires) from coal seams, increasing the resolution of palaeoclimate records from the continental part of the succession significantly. Exploration drilling and research activity for decades in the CTB has yielded an extensive amount of lithological, geochemical and biostratigraphical data. More than 500 sedimentological drill cores through the lower part of the Paleogene sedimentary record in Svalbard which provides a unique possibility to construct the palaeo terrain surface. This creates a 3D palaeoclimate laboratory that to our knowledge has no counterparts in the Arctic and rarely onshore in general. Age constraints exists from bentonite ash layers preserved in coal seams (Jones et al. 2017) and orbitally tuned isotope records (Charles et al 2011).  We use the possibilities for combination of a high-resolution 3D reconstruction of physical and vegetation elements of a coastal landscape with high-resolution proxies for vegetation cover, temperature, precipitation, atmospheric dust and forest fires to investigate response and feedback mechanisms in a warm Arctic. 

References

Charles, A.J. et. al.2011. "Constraints on the numerical age of the Paleocene‐Eocene boundary." Geochemistry, Geophysics, Geosystems 12, no. 6.Clifton, A.J., 2012. The Eocene flora of Svalbard and its climatic significance (Doctoral dissertation, University of Leeds).Cui, Y. et al. 2011. "Slow release of fossil carbon during the Palaeocene–Eocene Thermal Maximum." Nature Geoscience 4, no. 7 (2011): 481-485.Cui, Y. et al. 2021. "Synchronous Marine and Terrestrial Carbon Cycle Perturbation in the High Arctic During the PETM." Paleoceanography and Paleoclimatology 36, no. 4 (2021): e2020PA003942.al and geochemical signals." Palaeogeography, Palaeoclimatology, Palaeoecology 302, no. 3-4: 156-169.Spielhagen, R., & Tripati, A.. "Evidence from Svalbard for near-freezing temperatures and climate oscillations in the Arctic during the Paleocene and Eocene." Palaeogeography, Palaeoclimatology, Palaeoecology 278, no. 1-4 (2009): 48-56.Jones, M. Et al., 2017. "Constraining shifts in North Atlantic plate motions during the Palaeocene by U-Pb dating of Svalbard tephra layers." Scientific reports 7, no. 1: 1-9.

How to cite: Jensen, M. A., Jelby, M., Jochmann, M., and Marshall, C.: Palaeo-coastal and vegetation response to warming a high Arctic – using the Paleogene – Eocene in Svalbard, Arctic Norway as a laboratory for future change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12414, https://doi.org/10.5194/egusphere-egu23-12414, 2023.

11:05–11:15
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EGU23-11470
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SSP2.1
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ECS
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Virtual presentation
Frida S. Hoem, Isabel Sauermilch, Suzanna van de Lagemaat, Adam K. Aleksinski, Matthew Huber, Adrián López-Quirós, Karlijn van den Broek, Johan Etourneau, Steve M. Bohaty, Francien Peterse, Henk Brinkhuis, Francesca Sangiorgi, and Peter K. Bijl

In the early-to-mid Cenozoic (66-34 Ma), Southern Ocean circulation was dominated by two subpolar gyres in the Atlantic-Indian and Pacific Oceans. These gyres transported surface water from the subtropics towards Antarctica. The Drake Passage and Tasmanian Gateway opening and widening during the late Cenozoic (34–0 Ma) gradually allowed circumpolar flow of the Antarctic Circumpolar Current (ACC) and the onset of complex oceanic frontal systems, which broke down the earlier subpolar gyres. Questions remain about the precise timing and nature of the onset of the ACC-system and the consequence for climate, ocean circulation and Antarctic ice volume. We hereby provide new insights into the Late Eocene-Miocene (37–5 Ma) oceanographic development by reconstructing surface ocean environment combining remains of organic walled dinoflagellate cysts (dinocysts) and organic biomarker (TEX86and Uk’37) sea surface temperature (SST) estimates from marine sedimentary drill cores from the southwestern South Atlantic (IODP Site U1536, ODP Site 696 and piston cores from Maurice Ewing Bank), southeastern Indian Ocean (ODP Site 1168) and southwestern Pacific (ODP Site 1172). We compare our results, together with available Southern Ocean records, with model experiments and tectonic reconstructions to deconvolve the effects of climate, ice volume and tectonic changes on Southern Ocean oceanography.

Late Eocene – Early Oligocene SSTs (37­–27 Ma) were broadly similar across the Southern Ocean (4–8°C latitudinal temperature difference), which we ascribe to persistent, strong subpolar gyral circulation influencing the sites. In the Late Oligocene (~26 Ma), progressive Antarctic-proximal cooling increased the SST gradient in the Australian-Antarctic gulf (>9°C). The timing of this Antarctic-proximal cooling coincided with sedimentary and kinematic reconstructions of Drake Passage deepening after 26 Ma, thus matching with ocean model experiments demonstrating that Drake Passage deepening weakened gyral circulation, enhanced thermal isolation and cooled Antarctic proximal waters. Throughout the Late Oligocene–Late Miocene (26–5 Ma) we record a continued contraction of the sub-polar gyre and southward migration of the subtropical gyre in the South Atlantic, with strengthening frontal systems and progressive cooling that first started in the southern South Atlantic. Although geographic coverage is sparse, our data shows for the first time the stepwise breakdown of subpolar gyres into the modern-like oceanographic regime with the development of strong frontal systems, latitudinal gradients and deep-water formation. We demonstrate, with modelling and geological data, that while climate and ice volume changes determine the strength of latitudinal SST gradients and position of ocean fronts on orbital time scales, gateway configurations play a large role in long-term trends.

How to cite: Hoem, F. S., Sauermilch, I., van de Lagemaat, S., Aleksinski, A. K., Huber, M., López-Quirós, A., van den Broek, K., Etourneau, J., Bohaty, S. M., Peterse, F., Brinkhuis, H., Sangiorgi, F., and Bijl, P. K.: Stepwise mid-Cenozoic breakdown of sub-polar gyres and strengthening of the Antarctic Circumpolar Current, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11470, https://doi.org/10.5194/egusphere-egu23-11470, 2023.

11:15–11:25
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EGU23-15220
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SSP2.1
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On-site presentation
Luis Valero, Thierry Adatte, Bet Beamud, Miguel Garcés, Miguel López-Blanco, Sharma Nikhil, Emmanuelle Chanvry, Marta Roigé, Sabi Peris, François Guillocheau, Alexander C. Whittaker, Pau Arbués, Cai Puigdefabregas, and Sébastien Castelltort

Past sedimentary archives provide invaluable comparative insights to understand Earth’s surface reaction to climate shifts and perturbations. Foreland basins are particularly interesting settings for investigating the sedimentary record of ancient climate perturbations because their high-accommodation and high-sedimentation rates favour protracted and expanded records that complement more distal oceanic records. In addition, due to their proximity to source areas, they provide direct information on the land surface response to the regional impacts of global climate shifts.

However, besides climate signals, the stratigraphic record of foreland basins is subject to a broad range of other factors that make its interpretation challenging. Indeed, foreland basins are naturally sensitive to the influence of tectonics on sediment production and accommodation, either associated with the long-term tectonic evolution of the orogen-basin system, or with the more local and regional shorter-term structural dynamics and geodynamic perturbations. Moreover, if connected to oceanic domains, eustatic sea-level oscillations can also combine with the above factors in determining final stratigraphic patterns.

Over the last two decades, a large body of paleoclimate work has produced new and crucial data on global climate events that have affected our planet. In particular, a suite of global climate perturbations (warming, cooling) have been identified in the Paleogene, thanks to stable isotope of C and O, with some major global warming events such as the PETM, ETM2&3, the EECO, the MECO and others that have fundamental implications for the current global climate crisis.

This well-established climatic template provides a unique opportunity to test the impact of climate on surface systems in deep time, particularly during the Paleogene hothouse. Therefore, we here present our work on the Isabena section in the South Pyrenean Foreland basin, which is a uniquely continuous and well exposed succession encompassing from the upper Cretaceous to the upper Eocene. We sampled continuously at 1-10 meters intervals over the 4 km-thick succession, from the lower Eocene to the upper Eocene. This sampling results in a new and continuous magnetostratigraphy covering almost 30 Myr of stratigraphic evolution, and a new high-resolution stable isotope record of carbon and oxygen over the Paleogene. These results combined with sedimentological descriptions and stratigraphic analyses reveal the links between important sedimentation changes and global climate events. Preliminary results suggest that hyperthermal events are often associated with enhanced sediment transport and clastic deposition in the basin, while intervals comparatively cooler seem to be more prone to enhanced carbonate accumulation.

How to cite: Valero, L., Adatte, T., Beamud, B., Garcés, M., López-Blanco, M., Nikhil, S., Chanvry, E., Roigé, M., Peris, S., Guillocheau, F., Whittaker, A. C., Arbués, P., Puigdefabregas, C., and Castelltort, S.: Magnetostratigraphy and stable isotopes record of Paleogene global climate events in a 30Myr expanded foreland basin succession, Isabena river, Southern Pyrenees, Spain, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15220, https://doi.org/10.5194/egusphere-egu23-15220, 2023.

pre-Cenozoic
11:25–11:35
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EGU23-13182
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SSP2.1
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On-site presentation
Bas van de Schootbrugge, Martin Schobben, Chloe Morales, Lubos Polerecky, Michiel Kienhuis, Klaas Nierop, Francien Peterse, Nico Janssen, Tianchen He, Rob Newton, Julia van Winden, Johan Weijers, Olaf Podlaha, Appy Sluijs, and Jack Middelburg

Fossil ikaite, preserved as the pseudomorph glendonite, occurs in vast amounts in Jurassic and Cretaceous successions in the high Arctic. Thermodynamics predict that ikaite is only stable at near-freezing temperatures and glendonite is thus widely used as a paleo-indicator of cold climate conditions, conflicting with traditional views of a very warm and equable Mesozoic greenhouse. Here, we show based on a multi-proxy investigation of Jurassic and Cretaceous glendonites from Siberia and Svalbard that this one-dimensional view detracts from their exceedingly complex biogeochemistry. NanoSIMS analyses of a Jurassic glendonite from Siberia produced large C-isotope gradients (> 40‰) over micrometer distances hinting at strong kinetic fractionation that is coupled to the formation of various precipitates, including an inclusion-rich primordial phase with C-isotope values as low as -38‰ that records methane oxidation. In line with previous results from Siberia, all investigated glendonites from the Cretaceous of Svalbard contain methane gas (700 - 2500 ppb/g) with enriched δ13C-CH4 signatures (-44 to -50‰ V-PDB), depleted δ2H--CH4 (-285 to -245‰ V-SMOW), and relatively large proportions of C2-C5 gas. Such values are potentially indicative of thermogenic methane gas sourced from structure II gas hydrates. Organic geochemistry of glendonites from Svalbard shows the presence of abundant hopanes, including bisnorhopanes with a CSIA signature of -41‰, suggesting activity of sulfide oxidizing bacteria possibly also linked to the inclusion of oil droplets. Moreover, exceptionally heavy bulk δ34Scas values of +46.2‰ clearly link marine ikaite formation in deep time to sulfate-driven anaerobic methane oxidation. Marine ikaite formation and preservation is thus a highly complex process, driven by temperature and (bio)chemical processes in the sea floor, complicating its use as a simple paleoclimate proxy. Regardless, glendonite episodically trapped large amounts of greenhouse gases and stored those for hundreds of millions of years, making this authigenic mineral a potential recorder of past carbon cycle perturbations.

How to cite: van de Schootbrugge, B., Schobben, M., Morales, C., Polerecky, L., Kienhuis, M., Nierop, K., Peterse, F., Janssen, N., He, T., Newton, R., van Winden, J., Weijers, J., Podlaha, O., Sluijs, A., and Middelburg, J.: Mineral-trapping of greenhouse gases in Arctic glendonites, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13182, https://doi.org/10.5194/egusphere-egu23-13182, 2023.

11:35–11:45
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EGU23-6958
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SSP2.1
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On-site presentation
Roland Mundil, Neil P. Griffis, Isabel P. Montañez, Lisa S. Oelkers, Bodo C. Ehling, Caroline Hasler, and Paul R. Renne

Recent findings using U-Pb zircon geochronology combined with paleoenvironmental proxies and sedimentological observations have constrained the timing and extent of glacial advances and retreats across southwestern and south-central Gondwana during the Late Paleozoic Ice Age (LPIA). Sedimentary archives deposited during the transition from the latest Carboniferous to the earliest Permian reveal widespread short-term warming as reflected in the loss of subglacial deposits across Gondwana basins, some of which were fully deglaciated by the end of the Carboniferous at 299 Ma. These observations are accompanied by fluctuations in proxies for pCO2 and δ13C across the Carboniferous-Permian transition. These climate oscillations require large scale, short-lived climate forcing mechanisms. One such potential cause may be greenhouse gas emissions related to widespread magmatism across central and northwestern Europe, which has been linked to a deep-seated mantle plume. The effects of igneous activity may be further amplified by the interaction of magma with widely occurring organic-rich sedimentary rocks across this region. The products of this magmatic province predominantly show silicic compositions, but intermediate and basaltic melts also occur in outcrops and cores from the British Isles and southern Sweden (predominantly in the form of dykes and sills), the Oslo and Skagerrak Graben as well as the Northern and Southern Permian Basin, which extends from the North Sea across northern Germany to Poland (predominantly filled with rhyolitic and rhyodacitic volcanics).

Available radioisotopic age constraints for these magmatic products are from different isotopic systems whose comparison requires consideration of systematic errors, and often have large uncertainties (at the several million-year level) rendering them unsuitable for studying potential causal relations to contemporaneous climate fluctuations that operate at much shorter timescales. We review these results and present new high-resolution U-Pb zircon CA-TIMS (Chemical Abrasion-Thermal Ionization Mass Spectrometry) ages from volcanic and intrusive products from the Southern Permian Basin and adjacent areas which show that the duration of magmatic activity was much shorter than previously thought. We suggest that greenhouse gas emissions from the magma, and its interaction with biogenic sedimentary rocks, may have been the cause for the observed short-term climate oscillations across the Carboniferous-Permian transition. These short-term events, and their effects, appear to be superimposed on long-term climate drivers such as continental arc volcanism, tropical silicate weathering, as well as changes in the distribution of continents in high latitudes, the opening and closing of oceanic gateways and tectonically induced variation in the equilibrium-line altitude for ice.

The research presented here is supported by NSF grant 1728705

How to cite: Mundil, R., Griffis, N. P., Montañez, I. P., Oelkers, L. S., Ehling, B. C., Hasler, C., and Renne, P. R.: Timing and potential causes for paleo-environmental change during the Late Paleozoic Ice Age (Carboniferous-Permian transition), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6958, https://doi.org/10.5194/egusphere-egu23-6958, 2023.

11:45–11:55
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EGU23-10414
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SSP2.1
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ECS
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On-site presentation
Lihui Lu, Yigui Han, Guochun Zhao, Zhenfei Wang, Pengcheng Ju, and Xuyang Cao

The formation of Neoproterozoic tillites and overlying cap carbonates is important to understand drastic climatic and paleo-environmental variations during and after the collapse of the Snowball Earth. This rock assemblage has been found at the northwestern margin of the Tarim Craton in China but its depositional processes are still debated. We carried out stratigraphic and carbon isotopic studies on the tillites of the Yuermeinak Formation and overlying cap carbonates in this area. Detailed field observation and stratigraphic comparison demonstrate that these strata formed around the age of Marinoan deglaciation (ca. 635 Ma). Unconformable contacts with bedrocks and the variation of dip directions of the cap carbonates suggest that a mountainous topography developed in northwest Tarim during the Marinoan glaciation. We proposed a four-stage depositional model from glacial to alluvial fan and/or neritic facies systems. The first stage formed the stratified and massive tillites, recording several glacial cycles during the Marinoan deglaciation. The second stage involved the belated transgression at the end of the Marinoan deglaciation, caused the re-cementation of some tillites and the negative δ13C of their matrixes. The third stage included the alternating precipitation of calcareous mudstones and cap carbonates after the Marinoan deglaciation, reflecting frequent sea-level changes. The fourth stage was relevant to a terrestrial environment because of a widespread marine regression. Furthermore, we suggest that the timespan of the intense chemical weathering on exposed continents after the Marinoan deglaciation was comparable to the duration of the transgression, lasting for hundreds of thousands of years. This work was financially supported by NSFC projects (grants 42072264, 41730213, 41902229, 41972237) and Hong Kong RGC GRF (17307918).

How to cite: Lu, L., Han, Y., Zhao, G., Wang, Z., Ju, P., and Cao, X.: Deposition of tillites and cap carbonates in NW Tarim, China: Implications for chemical weathering following the Marinoan deglaciation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10414, https://doi.org/10.5194/egusphere-egu23-10414, 2023.

Fjord sediments
11:55–12:05
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EGU23-1847
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SSP2.1
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ECS
|
On-site presentation
Manuel Ruben, Jens Hefter, Florence Schubotz, Walter Geibert, Martin Butzin, Torben Gentz, Hendrik Grotheer, Matthias Forwick, Witold Szczuciński, and Gesine Mollenhauer

Fjords have been identified as carbon burial hotspots, sequestering about 18 MtC annually, with most recent estimates suggesting 61±16% of sedimentary organic carbon (OC) to be labile. Towards higher latitudes and catchment glaciation the relative contribution of petrogenic OC increases in fjord sediments. Enhanced melting and mass loss due to anthropogenic climate change is expected to increase sedimentary runoff from glaciers and ice-sheets in the coming decades, including previously locked-up petrogenic OC. Since petrogenic OC has an accumulated history of pre-depositional degradation, sequestration, and diagenesis, it has commonly been regarded as non-bioavailable to today’s microbes and is typically not considered a carbon source in climate models. However, over the last two decades, several studies discussed microbial utilization of petrogenic OC. While glacially derived dissolved OC was identified as being highly bio-available in the water column, the bio-availability of its particulate counterpart is virtually unexplored, especially after redeposition. To investigate the bio-availability of sedimentary petrogenic OC and its carbon feedback potential to the atmosphere, we extracted and determined intact polar lipids (indicative of living microbes) and their radiocarbon signature down core in three sediment cores in a proximal-to-distal transect in Hornsund fjord, Svalbard. By applying an isotope mass balance, we were able to show that local subsurface bacteria use between 5 ± 2% and 55 ± 6% (average of 25 ± 16%) of petrogenic OC for their biosynthesis. Thus, providing evidence that particulate petrogenic OC is bio-available after redeposition and is used as an important substrate in the subsurface. This suggests a potential positive feedback of increased petrogenic OC supply to fjord sediments via its bacterial utilization and subsequent carbon release in a warming climate. Further, we observe increased bio-availability of petrogenic OC along both the distal-to-proximal transect and down core. We hypothesize that the spatial and temporal variability of petrogenic carbon utilization is related to the availability of recently synthesized marine OC as well as to the distance to glacial termini, thus to sediment accumulation rate and oxygen availability.

How to cite: Ruben, M., Hefter, J., Schubotz, F., Geibert, W., Butzin, M., Gentz, T., Grotheer, H., Forwick, M., Szczuciński, W., and Mollenhauer, G.: Utilization of petrogenic organic carbon in Arctic Fjord sediments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1847, https://doi.org/10.5194/egusphere-egu23-1847, 2023.

12:05–12:15
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EGU23-10699
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SSP2.1
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On-site presentation
Dahae Kim, Jung-Hyun Kim, Youngkyu Ahn, Kwangchul Jang, Ji Young Jung, and Seung-Il Nam

Svalbard fjords are hotspots of organic carbon (OC) burial because of their high sedimentation rates. To identify sedimentary OC sources in Arctic fjords, we investigated surface sediments collected from eight Svalbard fjords using bulk and molecular geochemical parameters. All fjord surface sediments investigated were depleted in △14Corg (–666.9±240.3‰, n=28), suggesting that more recently fixed terrestrial and marine biomass is not the only contribution to the sedimentary OC. However, the source could not be determined by the most commonly used bulk indicators (i.e., Norg/TOC ratio and δ13Corg) in the Arctic realm. Thus, we applied a three-endmember model based on △14Corg and lignin phenols to disentangle the relative contributions of petrogenic, subglacial, and marine OC to the sedimentary OC pool. The fjord sediments (n=48) comprised on average of 79.3±26.1% petrogenic OC, 17.7±26.2% subglacial OC, and 3.0±2.5% marine OC. This three-end-member approach highlights the substantial contribution of petrogenic and subglacial OC to the present-day sedimentary OC in Svalbard fjords. Accordingly, under predicted warming worldwide, accelerated contributions of petrogenic and subglacial OC to fjords can be expected as a consequence of rapid glacier retreat, which may play an important role in the active carbon cycle as a potential CO2 source to the atmosphere.

How to cite: Kim, D., Kim, J.-H., Ahn, Y., Jang, K., Jung, J. Y., and Nam, S.-I.: Large contributions of aged organic carbon to Arctic fjord sediments in Svalbard, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10699, https://doi.org/10.5194/egusphere-egu23-10699, 2023.

12:15–12:25
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EGU23-2341
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SSP2.1
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On-site presentation
Katharine R Hendry, Hong Chin Ng, Jon Hawkings, Sebastien Bertrand, Brent Summers, Matthew Sieber, Tim Conway, Felipe Sales de Freitas, James Ward, Helena Pryer, Jemma Wadham, and Sandra Arndt

Glacier meltwater supplies a significant amount of silicon (Si) and iron (Fe) sourced from weathered bedrock to downstream ecosystems. However, the extent to which these essential nutrients reach the ocean is regulated by the processes occurring within fjords, which act as conduits from glacial rivers and subglacial discharge and the ocean. One key – but understudied – component of biogeochemistry within fjords is benthic cycling, especially in regions of rapid deposition of reactive particulates at fjord heads. Here, we explore the benthic cycling of Si and Fe at four Patagonian fjord heads through geochemical analyses of sediment pore waters, including stable Si and Fe isotopes (δ30Si and δ56Fe respectively), and novel reaction-transport modelling for Si. A high diffusive flux of dissolved Fe from the fjord sediments compared to open ocean sediments is supported by both reductive and non-reductive dissolution of glacially-sourced reactive Fe phases, as reflected by the range of pore water stable Fe isotopes (δ56Fe from -2.7 to +0.8‰). In contrast, the diffusive flux of dissolved Si from the fjord sediments is relatively low. High pore water δ30Si (up to +3.3‰) observed near the Fe(II)-Fe(III) redox boundary is likely associated with the removal of dissolved Si by Fe(III) mineral phases, which, together with high sedimentation rates, contribute to the low diffusive flux of Si at the sampled sites. Our results suggest that early diagenesis promotes the release of dissolved Fe but suppresses the release of dissolved Si at glaciated fjord heads. The redox sensitive coupling of Si and Fe has significant implications for our understanding of how essential nutrients are transport along fjord systems.

How to cite: Hendry, K. R., Ng, H. C., Hawkings, J., Bertrand, S., Summers, B., Sieber, M., Conway, T., Sales de Freitas, F., Ward, J., Pryer, H., Wadham, J., and Arndt, S.: Benthic dissolved silicon and iron cycling at glaciated Patagonian fjord heads, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2341, https://doi.org/10.5194/egusphere-egu23-2341, 2023.

Posters on site: Thu, 27 Apr, 14:00–15:45 | Hall X3

Chairpersons: Shu Gao, Greer Gilmer, Michele Rebesco
X3.65
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EGU23-2378
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SSP2.1
Leonardo Langone, Stefano Miserocchi, Manuel Bensi, Vedrana Kovacevic, Paolo Mansutti, Francesco De Rovere, and Patrizia Giordano

Water masses in the eastern Fram Strait are strongly influenced by the interaction between Atlantic and Arctic waters, and by atmospheric forcing, thus contributing to drive the global thermohaline circulation. There is considerable variability in the system due to different forcing (e.g., atmospheric, internal, tidal, shelf dynamics) that play an important role especially in the uppermost layer of the ocean. On the contrary, it is not entirely clear which processes are responsible for the inter-annual and seasonal variability of the deep flow in the western Spitsbergen region.

The oceanographic deep-sea mooring S1 has been deployed since 2014 on the continental slope offshore Storfjorden at a water depth of approx. 1000 m. In 2014-2016 and 2017-2018, a twin mooring (ID2) was also placed 140 km north of S1 at approximately the same depth in order to monitor spatial differences of the properties and dynamics of the water along continental slope.

Short-term fluctuations of thermohaline properties and currents at 1000 m depth were repeatedly measured both at S1 and ID2 in different years. Such oscillations were related to the passage of internal waves and/or eddies by the passage of intense atmospheric storms, which in turn trigger intrusions of AW into the deep layer, with tricky effects on ecosystem functioning.

Similarly to thermohaline properties, spatial and temporal fluctuations in total mass fluxes were also recorded. Annual particle fluxes ranged between 67 and 198 g m-2 y-1 at site S1, while  ID2 had approximatively twice the values of S1. Here, we discuss the drivers influencing the particle sources and the downward fluxes in the eastern Fram strait.

Peak values of particle fluxes occurred in late winter-early summer, in the same season of maximum variability of thermohaline properties. But, they were not perfectly synchronous with turbidity peaks. A time lag of a couple of months was detected between max turbidity and particle deposition in the sediment trap, when the currents slowdown. Actually, turbidity does not appear to be related to current speed, but to current direction (SE-NW). We suggest that upslope currents (E-ward), which occur during warm water intrusions, are able to resuspend bottom sediment at the shelf edge. From our dataset it is apparent that often (but not always) the water turbidity increases during the current rotation from eastward to the following NW direction.

How to cite: Langone, L., Miserocchi, S., Bensi, M., Kovacevic, V., Mansutti, P., De Rovere, F., and Giordano, P.: Downward particle fluxes at south-eastern Fram Strait (Svalbard), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2378, https://doi.org/10.5194/egusphere-egu23-2378, 2023.

X3.66
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EGU23-289
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SSP2.1
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ECS
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Giulia Sinnl, Mai Winstrup, Tobias Erhardt, Eliza Cook, Camilla Jensen, Anders Svensson, Bo Vinther, Raimund Muscheler, and Sune Rasmussen

Ice-core timescales are vital for our understanding of the past climate; hence they should be updated whenever significant amounts of new data become available. Here, the Greenland ice-core chronology GICC05 was revised for the last 3835 years by synchronizing six deep ice-cores and three shallow ice-cores from the central Greenland ice sheet. A new method was applied by combining automated counting of annual layers on multiple parallel proxies and manual fine-tuning. A layer-counting bias was found in all ice cores because of site-specific signal disturbances, therefore the manual comparison of all ice cores was deemed necessary to increase timescale accuracy. After examining sources of error and their correlation lengths, the uncertainty rate was quantified to be one year per century.

The new timescale, called GICC21, is younger than GICC05 by about 13 years at 3835 years ago. The most recent 800 years are largely unaffected by the revision. Between 800 and 2000 years ago, the offset between timescales increases steadily, with the steepest offset occurring between 800 and 1100 years ago. Moreover, offset-oscillations of about 5 years around the average are observed between 2500 and 3800 years ago. The non-linear offset behavior is attributed to previous mismatches of volcanic eruptions, to the much more extensive data set available to this study, and to the finer resolution of the new ice-core ammonium matching. By analysis of the common variations of cosmogenic radionuclides, the new ice-core timescale is found to be in alignment with the IntCal20 curve.

How to cite: Sinnl, G., Winstrup, M., Erhardt, T., Cook, E., Jensen, C., Svensson, A., Vinther, B., Muscheler, R., and Rasmussen, S.: A revised Greenland ice-core chronology for the last 3800 years: the GICC21, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-289, https://doi.org/10.5194/egusphere-egu23-289, 2023.

X3.67
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EGU23-6631
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SSP2.1
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ECS
|
Julia Rieke Hagemann, Frank Lamy, Helge W. Arz, Lester Lembke-Jene, Alfredo Martínez-Garcia, Alexandra Auderset, Naomi Harada, Ling Ho, Shinya Iwasaki, Jérôme Kaiser, Carina B. Lange, Murayama Masafumi, Kana Nagashima, Norbert Nowaczyk, and Ralf Tiedemann

Terrestrial glacial records from the Patagonian Andes and New Zealand Alps document quasi-synchronous southern hemisphere-wide glacier advances during the late Quaternary. Although detailed, these records are inherently incomplete. Here, we provide a continuous marine record of Patagonian Ice Sheet (PIS) extent over a complete glacial/interglacial cycle back to the previous glacial (~140 ka). Sediment core MR16-09 PC03, located at 46° S and ~150 km offshore Chile, received high terrestrial sediment input when the PIS advanced westward. We use biomarkers, foraminiferal oxygen isotopes, and major element data for reconstructing terrestrial sediment and freshwater input related to PIS variations. Our sediment record documents four major intervals of general PIS advance, during Marine Isotope Stage (MIS) 6 (135 – 140 ka), late MIS 5 (~85 – 95 ka), MIS 4 (~60 – 70 ka) and late MIS 3 to MIS 2 (~18 – 40 ka). These higher terrigenous input intervals occur during sea-level low stands when the western PIS covered most of the Chilean fjords which today retain glaciofluvial sediments. Superimposed, high amplitude phases of enhanced sediment supply reoccur at millennial time scales and reflect marine-based phases of the PIS with direct sediment discharge to the continental slope. We assign the late MIS 3 to MIS 2 phases and, by inference, also older advances to Antarctic stadials, consistent with the terrestrial record. Concomitantly, we observe enhanced meltwater release and conclude that the temperature-controlled PIS advances during southern hemisphere cold phases were likely reinforced by higher precipitation through enhanced westerly winds at the northwestern margin of the PIS.

How to cite: Hagemann, J. R., Lamy, F., Arz, H. W., Lembke-Jene, L., Martínez-Garcia, A., Auderset, A., Harada, N., Ho, L., Iwasaki, S., Kaiser, J., Lange, C. B., Masafumi, M., Nagashima, K., Nowaczyk, N., and Tiedemann, R.: A marine record of Patagonian ice sheet changes over the past 140 ka, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6631, https://doi.org/10.5194/egusphere-egu23-6631, 2023.

X3.68
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EGU23-9253
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SSP2.1
|
ECS
Fatima Bouhdayad, Tiago Freire, Gerald Auer, Rafael Carballeira, Daniel Herwartz, Stephanie Scheidt, Niklas Leicher, Volker Wennrich, Richard Albert Roper, Axel Gerdes, Jassin Petersen, Sven Nielsen, Marcelo Rivadeneira, and Patrick Grunert

Reduced landward moisture transport due to the cold upwelled surface waters of the Humboldt Current System (HCS) is one of the primary triggers of hyperarid conditions in the Atacama Desert. Marine sediments exposed along the coastline of northern Chile provide a unique archive of land-ocean coupling between coastal upwelling related HCS and paleoclimate in the Atacama Desert during the Neogene. Here we aim to establish a refined stratigraphic framework for the emplacement of diatom-rich deposits of the Bahía Inglesa Formation at Quebrada Tiburón (27°S).

The marine sediments exposed at Quebrada Tiburón lie transgressively above the pre-Cenozoic basement. A c. 9m-thick succession of laminated diatomaceous muds is intercalated with sandy deposits. Benthic foraminiferal assemblages and test morphology reveal a shift from trochospiral and planospiral (predominantly epifaunal) to serial (infaunal) morphotypes between sands and diatomaceous muds, respectively. Together with plankton assemblages dominated by diatoms and Globigerina bulloides, the diatomaceous muds reflect a highly productive coastal upwelling regime and low oxic, eutrophic conditions at the seafloor. However, occasional layers of bioturbation within the diatomaceous succession also imply phases of relaxed upwelling conditions. The new stratigraphic framework will thus allow the assessment of Neogene upwelling behavior and variability off Chile on orbital time scales.

Preliminary results based on calcareous nannoplankton, diatoms and planktonic foraminifera indicate a stratigraphic range from the upper Miocene (Messinian) to the lower Pliocene for the diatomaceous muds. Evidence from the δ18O of the benthic foraminifera Uvigerina peregrina further ties the upper part of the succession to an uppermost Zanclean age < 3.9 Ma. In a next step, the stratigraphic framework will be further improved by new data from magnetostratigraphy, Sr isotopes, and tephrochronology.

This study contributes to CRC 1211 “Earth-Evolution at the dry limit”, funded by the Deutsche Forschungsgemeinschaft (DFG).

How to cite: Bouhdayad, F., Freire, T., Auer, G., Carballeira, R., Herwartz, D., Scheidt, S., Leicher, N., Wennrich, V., Roper, R. A., Gerdes, A., Petersen, J., Nielsen, S., Rivadeneira, M., and Grunert, P.: Stratigraphy and depositional environment of Neogene diatom-rich sediments (Bahía Inglesa Formation) at Quebrada Tiburón, northern-central Chile, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9253, https://doi.org/10.5194/egusphere-egu23-9253, 2023.

X3.69
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EGU23-547
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SSP2.1
|
ECS
Julie Margrethe Fredborg, Ainara Sistiaga, Emil Munck Soltau, Karen Dybkjær, Stefan Piasecki, Erik Skovbjerg Rasmussen, Nicolas Thibault, and Kasia Kamilla Sliwinska

The Miocene Climatic Optimum (~17 to 14 Million years ago) has recently gained attention as a future climate analogue. However, the number of climatic records from the northern high and middle latitudes is very limited, so the global impact across this climatic transition is still poorly understood. The most northernly located site penetrating a nearly complete Miocene succession is located in the eastern North Sea Basin (Sdr. Vium borehole, Denmark). This research provides a multi proxy investigation performed on the Lower Miocene part of the succession. The studied interval corresponds with the time leading up to the onset of the Miocene Climatic Optimum. 

A total of 44 samples have been studied for their relative abundances of major palynological groups (dinocysts, acritarchs, spores, non-saccate pollen, saccate pollen and freshwater algae) and for the dinocyst/pollen ratio. In addition, 11 selected palynological samples were studied for their content of  dinocyst and acritarch taxa (counting a minimum of 200 specimens per sample).

 77 samples constitute the basis of a HH-XRF based chemical analysis. Furthermore, the n-alkanes of 8 samples have been analysed in order to assess their potential within a paleoenvironmental context. 

This study provides an updated age model (derived from dinocysts) and sequence stratigraphy of the Burdigalian (Early Miocene) succession of the Sdr. Vium core. The studied interval belongs to the Sumatradinium hamulatum Zone, the Cordosphaeridium cantharellus Zone and the Exochosphaeridium insigne Zone.  

XRF analysis combined with palynology improved the existing sequence stratigraphical framework of the studied site. Furthermore, the low resolution record of the n-alkanes show a good correlation between high content of the C23-25 and position of sequence boundaries.  

The changes in the relative abundance of warm-water dinocysts as well as alkenone-derived sea surface temperature suggest a brief interval of colder sea surface conditions just prior to the onset of the Miocene Climatic Optimum.  

 

How to cite: Fredborg, J. M., Sistiaga, A., Soltau, E. M., Dybkjær, K., Piasecki, S., Rasmussen, E. S., Thibault, N., and Sliwinska, K. K.: Climatic and environmental changes in the North Sea Basin during the Early Miocene, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-547, https://doi.org/10.5194/egusphere-egu23-547, 2023.

X3.70
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EGU23-15764
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SSP2.1
|
ECS
Jeroen Carmiggelt, Helen King, Mariette Wolthers, Bo Pagh Schulz, and Bas Van de Schootbrugge

Glendonites are calcite pseudomorphs after the mineral ikaite. Because ikaite typically forms at low temperature, glendonite occurrences in deep time have been interpreted as indication for cold environmental conditions, even when found in sediments associated with greenhouse climates (Vickers et al. 2020). However, the exact conditions that control glendonite formation are not well constrained, and their occurrences often contradict other temperature proxies (Price et al. 2013). Ikaite nucleation experiments have shown that the temperature stability range of ikaite can be extended under the influence of certain chemical compounds (e.g. Mg2+, PO43-) and foreign minerals (e.g. Tollefsen et al. 2018; Strohm et al. 2022). Several prominent glendonite intervals worldwide are found in close association with bentonites. Therefore, by using a combination of microscopic and spectroscopic techniques, this study sets out to investigate the ways in which bentonites affect ikaite crystallisation. The investigated bentonite samples were extracted from the early Eocene Fur formation that crops out at the islands Mors and Fur in northern Denmark. This formation is also known to contain some of the largest glendonite crystals recorded to date. 

We followed the method from Tollefsen et al. 2018 to synthesise ikaite and added Fur-formation bentonite and/or solutions that had reacted with this bentonite prior to ikaite synthesis. Laboratory observations combined with ATR-FTIR, Raman spectroscopy and optical microscopy suggest that ikaite precipitation occurred via a dissolution-reprecipitation processes. An ikaite nucleation experiment at high Mg concentrations, reproduced from Tollefsen et al. 2018, yielded 30% ikaite precipitation with 70% co-precipitating nesquehonite. When leachate was used in these experiments, we still observed ikaite precipitation while co-precipitating nesquehonite was almost absent. Crystal agglomeration appeared to occur faster in reactive solution in direct contact with bentonites.

When experimental solutions were reacting with (leaching) bentonite, additional calcium and phosphate release was observed by ICP-OES. Calcium and phosphate contents increased in the solution from about 350 ppm to 700 ppm and about 0.1 ppm to 7.5 ppm, respectively. This fertilisation process is suggested to favour ikaite precipitation over co-precipitating nesquehonite. The effect of element release from the bentonite on the resulting ikaite pseudomorph morphologies appears limited. Natural glendonite morphologies (in the Fur formation) are therefore more likely controlled by the nature of the storage medium and the temperature differential between the crystallisation and transformation process.

 

References

Price, G. D., Twitchett, R. J., Wheeley, J. R., & Buono, G. (2013). Isotopic evidence for long term warmth in the Mesozoic. Scientific reports3(1), 1-5.

Strohm, S. B., Inckemann, S. E., Gao, K., Schweikert, M., Lemloh, M. L., Schmahl, W. W., & Jordan, G. (2022). On the nucleation of ikaite (CaCO3x6H2O)–A comparative study in the presence and absence of mineral surfaces. Chemical Geology611, 121089.

Tollefsen, E., Stockmann, G., Skelton, A., Mörth, C. M., Dupraz, C., & Sturkell, E. (2018). Chemical controls on ikaite formation. Mineralogical Magazine82(5), 1119-1129.

Vickers, M. L., Lengger, S. K., Bernasconi, S. M., Thibault, N., Schultz, B. P., Fernandez, A., ... & Korte, C. (2020). Cold spells in the Nordic Seas during the early Eocene Greenhouse. Nature communications11(1), 1-12.

How to cite: Carmiggelt, J., King, H., Wolthers, M., Schulz, B. P., and Van de Schootbrugge, B.: Promotion of ikaite precipitation by bentonite fertilisation in the Eocene Fur formation, northern Denmark, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15764, https://doi.org/10.5194/egusphere-egu23-15764, 2023.

X3.71
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EGU23-15131
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SSP2.1
Andreas Lückge, Lutz Reinhardt, Werner von Gosen, Martin Blumenberg, and Jennifer Galloway

High-latitude terrestrial records of Paleogene hyperthermal events can help to calibrate global climate models seeking a refined understanding of extreme warming events; however, such high-latitude records are rare. The Margaret Formation at Stenkul Fiord, southern Ellesmere Island, preserves a record of the early Eocene hyperthermal events. This late Paleocene to early Eocene sedimentary archive is composed of fluvially derived clastic sediments and amber-bearing coals. However, as the Eurekan deformation event caused major synsedimentary tectonic movement, resulting in substantial unconformities, the development of a reliable stratigraphic framework for Stenkul Fiord has proved challenging thus far. Field mapping and satellite image interpretation were used to identify unconformities and other tectonic structures in a section at Stenkul Fiord. In combination with a previously dated ash layer (U-Pb zircon age of 53.7 Ma, ID-TIMS) and biostratigraphic association (Graybullian, NALMA) of rare vertebrate fossils, both the PETM and ETM-2 hyperthermal events were identified. In addition, samples for new carbon isotope data of bulk coal, organic-rich sediments and ubiquitous occurring amber were collected. Using this refined stratigraphic framework the average sedimentation rates were calculated, and stratigraphic completeness of the section was evaluated. It was determined that the amount of clastic sediment deposited at Stenkul Fiord increased near the end stages of the PETM and ETM-2 hyperthermal events. This is interpreted as a response of the fluvial depositional system to an intensified hydrological cycle during the hyperthermals. This probably resulted also in discharge events, in which amber was enriched in layers due its lower density and thus their preferential mobilization and re-deposition during water flooding the swamp forest environment. Whereas amber in general shows less depleted isotope values compared to coals, this process may explain the larger offsets between the istopic composition of coals and ambers observed in some layers, respectively. This late Paleocene to early Eocene deposits at Stenkul Fiord offer further possibilities to study the effects of global warming events on terrestrial northern highlatitude depositional systems.

How to cite: Lückge, A., Reinhardt, L., von Gosen, W., Blumenberg, M., and Galloway, J.: Depositional environment of coal and amber during the PETM and ETM-2 hyperthermal events in northern highlatitudes (Canadian Arctic), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15131, https://doi.org/10.5194/egusphere-egu23-15131, 2023.

X3.72
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EGU23-9963
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SSP2.1
|
Paula Granero Ordóñez, Adam Wierzbicki, and Michael Wagreich

The first occurrence of large Aspidolithus parcus parcus (Stradner 1963) Noël 1969 or Broinsonia parca subsp. parca (Stradner, 1963) Bukry, 1969 (of Nannotax3) defines the base of the Campanian. This bioevent is generally near the paleomagnetic reversal from C34n (Long Cretaceous Normal Superchron) to C33r, the primary marker for the base of the Campanian, with a proposed GSSP at Bottachione/Gubbio (Miniati et al., 2021). Changes in coccolith morphometry of the Aspidolithus/Broinsonia group are used to identify subspecies of the group relevant in the Upper Cretaceous. However, there is a taxonomic problem in the generic attribution of Aspidolithus (without central cross) or Broinsonia (with central cross) (see also Nannotax 3 and Miniati et al., 2020).

The present study focuses on the light-microscope morphometric analysis of Broinsonia/Aspidolithus group, around the Santonian–Campanian boundary (UC13-UC14a-UC14b) in the Loibichl section (Austrian Eastern Alps). A total of 1021 specimens with a moderate to good state of preservation of Broinsonia/Aspidolithus spp. have been measured using JMicroVision software. For each specimen, the length (L) and width (W) of the coccolith, the b/a ratio of the width of the outer rim/shield (b) versus the small diameter of the central area (a) (e.g. Gardin et al., 2001), as well as the number of perforations in the central area (e.g. Lauer, 1975) have been measured.

Five morphotypes were distinguished at Loibichl section as well as Wolfgring et al. (2018, Postalm section). Including the number of perforations: (1) Broinsonia enormis subs. 1 (L < 9 µm, b/a ≥ 2 and 8-16 perforations); (2) Broinsonia enormis subs. 2 (L < 9 µm, b/a < 2 and 4-12 perforations); (3) A. parcus expansus (Wise & Watkins in Wise 1983) Perch-Nielsen 1984 (L > 9 µm, b/a ≥ 2 and 8-16 perforations); (4) A. parcus parcus (L > 9 µm, b/a < 2 to ≥ 1 and 4-16 perforations; (5) A. parcus constrictus (Hattner et al., 1980) Perch-Nielsen 1984 (L > 9 µm, b/a <1 and 4-8 perforations). Throughout the section a trend in the distribution of morphospecies is observed, marked by an increase in the abundance of Aspidolithus parcus parcus and a decrease in the abundance of Aspidolithus parcus expansus in the upper part of the section.

Gardin, S., et al. 2001. Developments in Palaeontology and Stratigraphy 19, 745–757.

Lauer, G. 1975. Archives des Sciences de Genève 28, 259–262.

Miniati, F., et al. 2020. Rivista Italiana di Paleontologia e Stratigrafia 126, 783–801.

Wolfgring, E., et al. 2018.. Newsletters on Stratigraphy 51.

Young, J.R., et al. 2017. Nannotax3 website. Accessed 2 May 2021. URL: https://www.mikrotax.org/Nannotax3.

How to cite: Granero Ordóñez, P., Wierzbicki, A., and Wagreich, M.: Morphometrical analysis of the Aspidolithus/Broinsonia group around the Santonian–Campanian boundary in the Loibichl section (Austrian Eastern Alps), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9963, https://doi.org/10.5194/egusphere-egu23-9963, 2023.

X3.73
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EGU23-3143
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SSP2.1
Mark Woods, Laura Burrel, and Andrew Newell

The Kimmeridge Clay Formation is a mudrock-dominated succession deposited during the Upper Jurassic –Kimmeridgian and Lower Tithonian stages– in a shallow shelf environment, below fair- weather wave base. With a maximum thickness of 712m onshore, and 1400m in the northern North Sea, the formation has several intervals of bituminous shales, rich in organic matter, that make it a major oil source rock in the North Sea.

In the Late Jurassic, north-western Europe was part of the Laurasian Seaway, a shallow marine area underlain by a system of interconnected extensional basins. In Britain, sedimentation of the Kimmeridge Clay Formation took place in two main depo-centres; the onshore Wessex and Weald basins and adjacent Channel Basin in southern Britain, and the East Midlands Shelf and adjacent Cleveland Basin in north-eastern Britain, extending offshore into the North Sea. These depo-centres were bounded by normal fault systems. with significant syn-depositional activity associated with  Late Jurassic crustal extension allowing  development of thick sedimentary successions in the hangingwalls of these structures.

The sedimentary patterns of the Kimmeridge Clay formation are rhythmic, with intervals of mudstones, organic-rich mudstones and carbonate-rich stone bands, that give characteristic inflection patterns to wireline logs. These patterns are very similar across the Wessex and Weald basins but differ slightly from those of the East Midlands Shelf and Cleveland Basin; perhaps a consequence of compartmentalisation of accommodation space by the Anglo-Brabant Massif.

We present a new correlation of borehole geophysical logs (gamma & sonic) and associated thickness maps and structural maps for the Kimmeridge Clay Formation. They reveal lateral changes in thickness that reflect the influence of underlying basin structure on patterns of deposition and post-depositional erosion.

How to cite: Woods, M., Burrel, L., and Newell, A.: Thickness variations in the Kimmeridge Clay Formation in southern and eastern Britain: implications for Late Jurassic basin evolution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3143, https://doi.org/10.5194/egusphere-egu23-3143, 2023.

X3.74
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EGU23-11558
|
SSP2.1
Jochen Erbacher, Thomas Mann, and André Bornemann

Aalenian sedimentary deposits in southern Germany have accumulated in a shallow-marine, epicontinental shelf environment. These accumulations are dominated by thick claystones and argillaceous siltstones, with increasing percentages of sandstones towards the top. Aalenian sediments are likely to represent a relatively complete stratigraphic record, however, the sedimentary evolution and paleoclimatic significance of these typically poorly exposed deposits remain largely unexplored. Here we present a suite of high-resolution x-ray fluorescence (XRF) core scanning data from southern Germany to identify Transgressive-Regressive cycles during the Aalenian stage. Results are based on three scientific drill cores of 200 – 250 m length that have been analyzed with an Avaatech XRF Core Scanner at a 10 mm sampling interval (10 keV, 500 µA). Resulting trends in elemental Si/Al ratios, which are indicative for subtle grain-size variations, combined with sedimentological observations on ichnofacies and bedform development were used to reconstruct shoreline trajectories and establish a sequence stratigraphic framework for the thick and largely homogenous lower Aalenian Opalinuston Formation.

How to cite: Erbacher, J., Mann, T., and Bornemann, A.: Sedimentology and sequence stratigraphy of the lower Aalenian Opalinuston Formation from southern Germany, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11558, https://doi.org/10.5194/egusphere-egu23-11558, 2023.

X3.75
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EGU23-3019
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SSP2.1
Gil Young Kim, Kiju Park, Seok-Hwi Hong, Gwang Soo Lee, Dong Geun Yoo, and Seong-Pil Kim

The deep core samples (site name: 21ESDP-203, drilled depth: 200.3m) collected from the southeastern shelf (Korea strait) of Korea were used to characterize physical property with sedimentary depth. Laboratory analysis (i.e., velocity and physical properties) was conducted on core samples. The physical property data were readily classified in good agreement with the lithological units alternating sandy mud and muddy sand with sedimentary depth. Based on compressional wave velocity data, the geoacoustic units are divided by 11 units with sedimentary depth. In particular, the upper sediments above 15 meter are characterized by high compressional wave velocity (greater than 1700 m/s) and high wet bulk density (∼2.2g/cm3 in maximum). Whereas, the porosity is very low (25% in minimum). This is due to the abundance of sandy sediments in this interval. The shear wave velocities of sediments are calculated from the compressional wave velocity and the effect of burial depth (Hamilton, 1980). The range of shear wave velocity is from 267 to 1345 m/s. However, most of data are less than 400 m/s. The velocity ratio (Vp/Vs) and the velocity gradient with sedimentary depth are calculated and estimated. The patterns are slightly different from those of Hamilton (1980). These results suggest that the physical properties are not only controlled by lithology and compaction caused by dewatering with burial depth, but also by different sedimentary environment after deposition. 

How to cite: Kim, G. Y., Park, K., Hong, S.-H., Lee, G. S., Yoo, D. G., and Kim, S.-P.: Physical property characterization of deep core sediments in the southeastern shelf (Korea strait) of Korea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3019, https://doi.org/10.5194/egusphere-egu23-3019, 2023.

X3.76
|
EGU23-8859
|
SSP2.1
Seok-Hwi Hong, Dong-Geun Yoo, Gwang-Soo Lee, Jin Cheul Kim, Sangheon Yi, and Gil-Young Kim

This study focus on the depositional environment of the Hupo Basin shelf. We used sedimentary facies, grain size, textures, sediment color, as well as optically stimulated luminescence (OSL) and accelerator mass spectrometry (AMS) age data.  A long sediment core (19ESDP-101, about 120 m) has been interpreted to be the product of shallow water contourites. The sediments in the core are divided into seven sedimentary facies grouped into four facies associations (FA): FA1) contourite drift, FA2) contourite drift and channel transition, FA3) contourite channel and drift transition, and FA4) contourite channel. FA1 resulted from the interaction between hemipelagic fallout, low-density gravity flow, and sedimentation under low velocity bottom currents. Compared to FA1, both FA 2 and FA3 are indicative of higher velocity bottom currents, owing to their relative increase in grain size and the presence of subtle indicators of bed-load transport. FA 4 portrayed massive to slightly bedded sand,  representing a contourite channel environment with high-energy conditions. The sedimentary facies stacking patterns observed at the study area site suggested that the depositional processes changed at the area where the core was optained. Therefore, the FA stacking pattern suggests the lateral migration of the contourite depositional system and continuous flow of the North Korean Cold Current (NKCC). Fluctuations in the bottom current activity, related to the intensification and deceleration of the NKCC, have caused fluctuations between contouritic and hemipelagic dominated periods. Our findings and interpretations can serve as a much needed reference for shallow-water contourite recognition in modern environments.

How to cite: Hong, S.-H., Yoo, D.-G., Lee, G.-S., Kim, J. C., Yi, S., and Kim, G.-Y.: Facies association and depositional environment of shallow-water contourite deposits in the Hupo Basin, East Sea of Korea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8859, https://doi.org/10.5194/egusphere-egu23-8859, 2023.

X3.77
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EGU23-12457
|
SSP2.1
Andrew Gorman, Gary Wilson, Chris Moy, Christina Riesselman, Jackson Beagley, Greer Gilmer, Bob Dagg, and Hamish Bowman

Fiordland, on the southwest coast of New Zealand’s South Island, hosts 15 distinct fjords that extend up to 40 km inland from the Tasman Sea into mountainous terrain consisting primarily of hard crystalline igneous and metamorphic rocks. All of these fjords have seaward entrance sills, and most have glacially eroded and overdeepened basins that contain sediments deposited following the retreat of the glaciers that carved the valleys out. These sedimentary basins preserve a record of post-glacial environments that can be used to evaluate changes in regional sea level, climate, vegetation and other conditions. For example, in cases where the entrance sills were higher than the last glacial maximum sea level, the present-day fjords would have previously been isolated glacial lakes prior to marine ingression due to post-glacial sea level rise; this lacustrine-marine transition is recorded in the fjord sediments, e.g., as flooded deltas and beaches.

Over the last 10 years, we have collected high-resolution boomer-sourced seismic reflection data in most of the fjords of Fiordland using a 75-m-long 24-channel Geometrics MicroEel array recording signals from an acoustic boomer source (initially a Ferranti system and then, more recently, one from Applied Acoustics). Processing has been undertaken using commercial (GLOBE Claritas) seismic processing software. We present a summary of this work, showing profiles along a number of the fjords including, from north to south, Milford, Nancy, George, Thompson/Bradshaw, Doubtful, Dagg, Dusky and Long sounds. Seismic sections show a wide variety of sediment accumulations in the fjords depending on periglacial conditions, sill depth, catchment size, catchment rock types and vegetation history, etc. Sediment thicknesses are observed to exceed several hundred metres in some of the basins – which supports an interpretation of interbedded strata of muds, silts, and fine sands. The depositional history of the sedimentary units imaged by these data, in conjunction with additional seafloor mapping, direct seafloor sampling and shallow cores, will be confirmed by deep drilling efforts in the fjords.

How to cite: Gorman, A., Wilson, G., Moy, C., Riesselman, C., Beagley, J., Gilmer, G., Dagg, B., and Bowman, H.: High-resolution imaging of sedimentary basins in New Zealand’s fjords using boomer-sourced multi-channel seismic reflection data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12457, https://doi.org/10.5194/egusphere-egu23-12457, 2023.

Posters virtual: Thu, 27 Apr, 14:00–15:45 | vHall SSP/GM

Chairpersons: Shu Gao, Greer Gilmer, Michele Rebesco
vSG.6
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EGU23-1008
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SSP2.1
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ECS
yongwei zhang

AMS14C dating, particle size and clay mineral analysis were carried out on the QZ4 core from the southeastern shelf of Hainan Island in this study. The material source and sedimentary environment evolution of the southeastern shelf of Hainan Island were discussed. Analysis of clay minerals shows that the terrigenous clasts of the southeastern shelf of Hainan Island are mainly from Hainan Island. The particle size endmember simulation identifies two endmembers. The EM1 endmember corresponds to the mixed deposition of near-source and far-source fine materials transported by Marine current systems, while EM2 mainly corresponds to coarse-grained materials imported from the near-source rivers of Hainan Island. The two endmembers represent two different transport mechanisms. The sedimentary environment in the study area can be roughly divided into three stages: 11.2-9.2 ka BP, 9.2-6.6 ka BP and 6.6 ka BP to date correspond to foreshore, near-shore and shallow Marine shelf sedimentary environments respectively. During 11.2-6.6 ka BP period, the sedimentary environment was mainly controlled by sea level changes, but extreme cold events such as "9.4 ka BP cold event" and "8.2 ka BP cold event" still had an important impact on the southeastern shelf of Hainan Island. Up to 6.6 ka BP, the sedimentary record is mainly controlled by climate change, and the increase of fluvial contribution and chemical weathering may be due to the intensification or number of typhoons. It is urgent to carry out follow-up research on high-resolution typhoons and storms in sediments in the eastern shelf area and adjacent areas of Hainan Island.

How to cite: zhang, Y.: Sediment provenance and paleoenvironmental evolution in southeastern shelf of Hainan Island since Holocene, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1008, https://doi.org/10.5194/egusphere-egu23-1008, 2023.