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.

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.

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.

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.

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.

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.

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.

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.

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 U^k’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.

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.

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 δ³⁴S_cas 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.

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.

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.

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.

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 △¹⁴C_org (–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., N_org/TOC ratio and δ¹³C_org) in the Arctic realm. Thus, we applied a three-endmember model based on △¹⁴C_org 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.

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.