GM4.3 | Source-to-Sink: A Multi-Proxy Approach to Disentangle Forcings throughout the Sedimentary Record

GM4.3

Source-to-Sink: A Multi-Proxy Approach to Disentangle Forcings throughout the Sedimentary Record
Co-organized by SSP2
Convener: Rocio Jaimes-GutierrezECSECS | Co-conveners: Iwan SetiawanECSECS, Marine PrieurECSECS, Camilo Esteban GaitanECSECS, Philémon JuvanyECSECS
Orals
| Thu, 27 Apr, 14:00–17:53 (CEST)
 
Room -2.31
Posters on site
| Attendance Fri, 28 Apr, 08:30–10:15 (CEST)
 
Hall X3
Posters virtual
| Attendance Fri, 28 Apr, 08:30–10:15 (CEST)
 
vHall SSP/GM
Orals |
Thu, 14:00
Fri, 08:30
Fri, 08:30
A source-to-sink approach represents a quantitative and integrated characterization of the processes involved in the production, transport, and deposition of sediments along a sediment routing system (SRS). This approach conceptualizes the SRS as an interconnected system in which external forcings (such as tectonics and climate) generate and propagate signals that might be recorded in the sedimentary record. Such studies aim at re-creating the spatio-temporal framework of the nature and intensity of the perturbations induced along a sedimentary system due to an external forcing. This has important implications for understanding the sensitivity of the Earth’s surface to tectono-environmental changes, for the reconstruction of paleoclimates, and for modeling the future dynamics of sedimentary systems on the planet. In addition, a sediment routing system approach is a vital tool for the effective identification and management of mineral, hydrocarbon, and water resources.

In this session, we invite scientists who study the signal generation and propagation in source to sink systems from a wide range of backgrounds (e.g., sedimentology, geomorphology, geochemistry, remote sensing, and geomodelling), and we encourage studies focusing on provenance, sedimentary budgets, and response timescales. Further, we welcome contributions focusing on environmental changes and disentangling the role between climate and tectonics, including paleoclimatic response, feedback mechanisms, and applied studies, for instance, raw material production and risk analysis associated with sediment generation and transport.

Orals: Thu, 27 Apr | Room -2.31

Chairpersons: Rocio Jaimes-Gutierrez, Iwan Setiawan, Philémon Juvany
14:00–14:05
14:05–14:15
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EGU23-5980
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GM4.3
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ECS
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Virtual presentation
Amando P. E. Lasabuda, Domenico Chiarella, Tor Sømme, Sten-Andreas Grundvåg, Tom Arne Rydningen, Henry Patton, Jan Sverre Laberg, and Alfred Hanssen

Reconstructing sedimentation derived from multiple source areas is complex in terms of timing and lateral variability. Moreover, untangling sediment transport and deposition in a relatively mobile plate margin is even more challenging. Here, we present results from a forward stratigraphic modelling technique that has been used to simulate basin filling of the Cenozoic succession in the Barents Sea, a tectonically active area that may have received sediments from mainland Norway, the Barents Sea shelf, and NE Greenland. We have included parameters related to tectonics and climate, and the results have been calibrated with seismic and well data. Sensitivity analyses have been performed to test different paleobathymetric reconstructions, as the study area comprises both a moving plate boundary and variable sediment source directions and fluxes.

The Cenozoic evolution of the Barents Sea shelf is strongly linked to the breakup between the Greenland and the Eurasian plates at c. 55 Ma, which led to the development of local highs and basins along the margins of the Barents Sea. This configuration resulted in the deposition of progradational wedges and submarine fans (c. 40 Ma) in the basins including the Sørvestsnaget Basin. Subsequent plate reorganization caused a renewed shelf uplift (c. 33 Ma) and opening of the Fram Strait gateway (c. 17 Ma) affected the sedimentary processes and deposits (including the introduction of contourites) in the sink, observable in seismic and borehole data. A major increase in sediment supply resulting from glacial erosion in the past 3 Myr is reflected in the deposition of several >3 km-thick trough mouth fans along the continental margin. We present ongoing work and discuss the importance of different factors controlling stratigraphic variability in basins filled by multiple source areas.

How to cite: Lasabuda, A. P. E., Chiarella, D., Sømme, T., Grundvåg, S.-A., Rydningen, T. A., Patton, H., Laberg, J. S., and Hanssen, A.: A forward stratigraphic model of the Cenozoic multi-source-to-sink system in the Barents Sea, Norwegian Arctic, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5980, https://doi.org/10.5194/egusphere-egu23-5980, 2023.

14:15–14:17
14:17–14:27
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EGU23-13086
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GM4.3
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ECS
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On-site presentation
Melanie Kling, Hallgeir Sirevaag, Emmanuelle Pucéat, and Christian Haug Eide

The eruption of the Siberian Traps at the Permian-Triassic transition significantly affected depositional environments world-wide. Known consequences are (I) extreme global warming, (II) increased soil-erosion, decreasing chemical weathering and aridification on the continents, (III) oceanic stagnation and acidification, and (IV) the most severe mass extinction on Earth. In the Southwestern Barents Sea, the record across the Permian transition is continuous at a cored site located close to the basin margin, making it possible to study the response of a relatively proximal source-to-sink system in terms of petrography, provenance, and sedimentary environments. The record consists of Upper Permian carbonates developed as an oxygenated carbonate platform, overlain by transitional dys- or anoxic, organic-rich shales and a Lower Triassic prograding siliciclastic turbidite-prodelta-delta system.

In this project we use these deposits to reconstruct the sediment source area and changes within the catchment area across the Permian-Triassic transition. From a dataset of >50 2D seismic lines and sampled sandstones from ~160 m stratigraphic cores, we have already found that the sediment supply rate increased by more than 100-fold, which vastly exceeds the world-wide trend of sediment supply increase across the Permian-Triassic transition (6–7-fold). This has led to several models that may explain the observed evolution, but in order to distinguish between these models, mudstone provenance and weathering proxies must also be investigated. Herein we focus on the Neodymium and Hafnium isotopic composition in the mudstones, and thus present insights into weathering processes. This will allow us to investigate the climatic component in the catchment across the transition. Our preliminary results show that the catchment in the Late Permian supplied mudstones with extreme (much more than observed in modern deposits) chemical weathering and a stable provenance from a small, nearshore catchment. Broadly coincident with the Permian Triassic Transition, mudstones show a provenance change consistent with increase in catchment area and a strong decrease in chemical weathering. This indicates that the increase in sediment supply from at the Permian-Triassic transition was not caused by sudden flushing of onshore weathered material stored in catchments during the Permian, nor can it be caused by increase in chemical weathering because of climate change. It appears that the observed changes are mainly a result of tectonic uplift and tilting of Northern Fennoscandia possibly due to onset of a new rifting episode in the Norwegian-Greenland Sea. The coincidence of this strong response to the Permian-Triassic transition could perhaps indicate that adjustments of the catchment to the new topographic setting was helped by the climate change.

How to cite: Kling, M., Sirevaag, H., Pucéat, E., and Eide, C. H.: Weathering response of a clastic source-to-sink system to extreme environmental perturbations: the Permian-Triassic transition on Finnmark Platform, Barents Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13086, https://doi.org/10.5194/egusphere-egu23-13086, 2023.

14:27–14:29
14:29–14:39
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EGU23-16363
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GM4.3
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ECS
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On-site presentation
Lucas Valore, Tor Sømme, Stefano Patruno, and Christian Eide

In several basins across the world, dynamic topography, which is created by internal mantle dynamics distinct from plate-boundary tectonics, has been shown to exert significant control on source-to-sink sediment distribution. In the Paleocene North Sea, peaks in sediment flux and transient uplift have  been previously associated with perturbations in dynamic topography created by a precursor to the modern-day Icelandic Plume. However, previous studies have had a limited understanding of the regional paleogeographic context of the area, due in part to data constraints. Here, we will investigate the Paleocene - Early Eocene paleogeographic and stratigraphic evolution of the East Shetland Platform in terms of the extent and timing of erosion versus deposition and how these can be used to reconstruct the behavior of an associated dynamic topography anomaly.

The stratigraphic record of the East Shetland Platform and the adjacent Viking Graben were interpreted using >60 000 km² of 3D seismic data, revised biostratigraphic picks and c. 300 previously interpreted well-logs. This allowed the construction of multiple chronostratigraphic “Wheeler” diagrams, relative sea-level (RSL) curves and high temporal resolution paleogeographic maps. Using the resultant seismic surfaces and well data, sediment volumes and masses were calculated for multiple Cenozoic units, which were then used to constrain sediment fluxes deriving from Shetland.

Multiple episodes of RSL fall and basinward offlap advance are recorded throughout the Paleocene, and from Late Thanetian to Ypresian, at least five well-preserved unconformity-bounded sequences are marked by prograding, alternating normal and forced regressive clinoforms of the Dornoch Formation. Temporal and spatial variations in the distribution of depocenters and individual subaerial unconformities indicate significant variability in patterns of shelf accommodation/erosion and fan deposition in the basinal Viking Graben. All of these are interpreted as a result of the complex interplay between laterally-uneven RSL fall, time-varied sediment entry point distribution, along-shore sediment transport/supply (evidenced by linear clinoform morphologies) and control by inherited topography/bathymetry. Most importantly, we infer a first-order control on erosion and sediment distribution promoted by the transiently and differentially uplifted topography of the ESP, as showcased by unconformities and paleogeographic maps.

Preliminary results indicate that peak sediment fluxes may predate the Dornoch progradation and correspond to the deeper water Lista formation of Selandian to Early Thanetian age. This peak matches published well-based sedimentation rates for the Cenozoic North Sea and predates uplift curves reconstructed from drainage networks in Shetland and Faroe, but fits the peak modelled dynamic topography of the Icelandic Plume. However, sediment fluxes and knickpoint-derived uplift rates are both extremely sensitive to the ages assigned to individual units/surfaces and the temporal resolution of analysis, and the uncertainty related to these is sufficient to drastically change the ages or even presence of individual peaks.

Ultimately, the area must have been influenced by shorter-wavelength spatial variations in uplift than what is assumed in typical models of dynamic topography, perhaps as a result of additional modulation of dynamic uplift by lithospheric structures of the North Sea or by some other mechanism that has not been resolved in current mantle imaging and modelling attempts.

How to cite: Valore, L., Sømme, T., Patruno, S., and Eide, C.: Control of dynamic uplift on paleogeography and sediment volumes: insights from the East Shetland Platform in the Paleocene, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16363, https://doi.org/10.5194/egusphere-egu23-16363, 2023.

14:39–14:41
14:41–15:01
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EGU23-12761
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GM4.3
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solicited
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On-site presentation
Eric Lasseur, Alexandre Ortiz, Charlotte Fillon, Justine Briais, Francois Guillocheau, Jessica Uzel, Gianlucca Frasca, Jocelyn barbarand, Nicolas Loget, Sebastien Castellort, and Sylvain Calassou

The knowledge acquired on the exhumation of the Pyrenean chain and the evolution of the adjacent foreland basins makes this Alpine-type domain a good laboratory to better constrain a full sediment routing system in a compressive context and to apprehend the driving processes controlling the sediment routing in space and time. This integrated approach aims at enhancing our basin mastering approach as well as improving our predictions of reservoir properties.

This Source-to-Sink study seeks to understand the evolution of sedimentary routing from the Source (orogenic relief, craton, basin recycling) through the transfer zone (peripheral or internal to the basin) to the final sink (flexural basin, deep turbiditic margin). Within this new cartography, we propose to compile the data over the entire peri-Pyrenean domain. We produced large scale quantitative and qualitative maps to better observe and interpret the tectonic, climatic and surface processes impacts of the SRS behavior.

These maps include kinematic reconstructions of the Iberian-European-Mediterranean system, restored sequential cross-sections, history/magnitude of exhumation by thermochronology, source tracking, characterization of weathering and erosion surfaces, synthesis of the major structures activity, paleogeographic reconstructions, analysis of sedimentary geometries and transport directions as well as the quantification of volumes preserved in the basins. Their interpretation is combined with a time representation along the routing system, linking classical basin wheeler diagram representation to source erosion and lithologies to obtain a continuous view on the sediment journey.

The time steps chosen for these 5 maps account for the different stages of tectono-sedimentary evolution of the peri-Pyrenean system at the early-, syn- and post-orogenic stages. The compilations carried out compare exhumed domains and sedimentation zones in terms of fluxes and volumes and make it possible to map the routing systems and point out the main drivers for the surface evolution during the construction/destruction cycle of an orogen.

Research work financed and carried out as part of the BRGM-TOTAL Source-to-Sink program

How to cite: Lasseur, E., Ortiz, A., Fillon, C., Briais, J., Guillocheau, F., Uzel, J., Frasca, G., barbarand, J., Loget, N., Castellort, S., and Calassou, S.: Integrated Source to Sink palaeogeological maps at pluri-basins-scale, understandings and predictions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12761, https://doi.org/10.5194/egusphere-egu23-12761, 2023.

15:01–15:06
15:06–15:16
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EGU23-8739
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GM4.3
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On-site presentation
Miguel Garcés, Miguel López-Blanco, Roi Silva, Philemon Juvany, Pau Arbués, Emilio Pueyo, and Elisabet Beamud

The Middle Eocene Climate Optimum (MECO) was a 0.5 Myr warming interval that punctuated the long-term cooling trend of the middle to late Eocene. It has been identified worldwide by a gradual negative shift of the dO18 followed by a sharp return to the cooling trend. The peak warming at about 40 Ma coincides in some records with a sharp negative excursion of the d13C, which suggested a relation of the warming event with a transient increase of pCO2. Results from various records also point to increased seasonality and chemical weathering of the source area in coincidence with the MECO.

The interval of the MECO is stratigraphically well constrained in the south-central Pyrenees, from the Graus-Trempto the Aínsa and Jaca basins thanks to previous biostratigraphic and magnetostratigraphic investigations. During this period, the south-Pyrenean foreland formed a narrow and shallow elongated basin connected to the west to the Atlantic Ocean. Here we present a record of the MECO in the carbonate platform succession (the Santo Domingo Member of the Arguis Fm.), that accumulated on the Iberian foreland margin, currently outcropping along the External Sierras (the frontal thrust sheet of the southern Pyrenees). Polished samples were micro-drilled to analyse the d18O and d13C isotopes ratios separately from the mud fraction and shells of different species of larger benthic foraminifera. The results show trends of the d18O from the mud fraction that parallel the global ocean isotope signature but with values that are offset towards more negative values (-4‰). There, the influence of the continental waters in the isotopic signal was possibly amplified by the restricted marine paleogeographic context.  Results from fossil shells gave values significantly different from the mud fraction: d18O from Nummulites shells were consistently offset towards more positive values compared to mud, which could indicate a different fractionation pathway or, alternatively, a preferred diagenetic alteration of fossil fragments. A sharp negative excursion of the d13C was identified in coincidence with the negative d18O peak, marking the location of the MECO. Noticeably, a short-lived entry of siliciclastics that replaced carbonate deposition is recorded at the time of the MECO peak, a feature comparable to what is documented in other sections of the eastern Jaca Basin, where a rapid pulse of deltaic sediments (Sabiñánigo sandstone) are embedded within a thick marine marl succession. Our observations agree with a scenario of perturbation of the hydrological cycle and transient increase of sediment discharge from the continent in coincidence with the MECO.

How to cite: Garcés, M., López-Blanco, M., Silva, R., Juvany, P., Arbués, P., Pueyo, E., and Beamud, E.: The record of the Middle Eocene Climate Optimum in the carbonate platforms of the South Pyrenean Basin (Santo Domingo, External Sierras), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8739, https://doi.org/10.5194/egusphere-egu23-8739, 2023.

15:16–15:18
15:18–15:28
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EGU23-2349
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GM4.3
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On-site presentation
Sebastien Castelltort, Lucas Vimpere, Jorge Spangenberg, Marta Roige, Thierry Adatte, Eric De Kaenel, Andrea Fildani, Julian Clark, Swapan Sahoo, Andrew Bowman, and Pietro Sternai

We present evidence of a ca 200 m-thick Paleocene–Eocene Thermal Maximum (PETM) sedimentary section within a 543 m-thick deep-marine core in the Gulf of Mexico (GoM). The negative carbon isotope excursion (CIE) characteristic of the PETM is identified thanks to organic carbon stable isotopes and tightly linked to the Paleocene-Eocene boundary thanks to high-resolution biostratigraphic constraints provided by nannofossil and palynomorph assemblages. The unusual thickness of the CIE suggests that the PETM climate perturbation in the upstream North American catchments induced a substantial response in the downstream sectors of the Gulf Coastal Plain, and ultimately in the GoM. This relationship is illustrated in the deep-water basin by 1) the deposition of a shale interval when coarse-grained terrigenous material was trapped upstream at the onset of the PETM, and 2) considerable sediment supply in response to increased sediment transport upstream. These results are particularly relevant for paleoclimate and source-to-sink reconstructions because they link deep water sedimentation with a continental-scale paleo-drainage.

How to cite: Castelltort, S., Vimpere, L., Spangenberg, J., Roige, M., Adatte, T., De Kaenel, E., Fildani, A., Clark, J., Sahoo, S., Bowman, A., and Sternai, P.: Carbon isotope and biostratigraphic evidence for an expanded PETM section in the deep Gulf of Mexico: implications for landscape response to climate change from source to sink, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2349, https://doi.org/10.5194/egusphere-egu23-2349, 2023.

15:28–15:30
15:30–15:40
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EGU23-8937
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GM4.3
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On-site presentation
Adar Glazer, Dov Avigad, Navot Morag, and Axel Gerdes

The Levant Basin in the Eastern Mediterranean contains a ~3 km-thick, predominantly siliciclastic section of Oligocene-Miocene age, which hosts large hydrocarbon reservoirs (“Tamar Sands Play”). A fundamental question raised with respect to this siliciclastic section concerns its origin and the sedimentary pathways into the deep basin. Here we present an advanced provenance study, including detrital zircon U-Pb-Hf and heavy mineral assemblage investigations, of Oligocene-Miocene siliciclastic sediments retrieved from four boreholes across the Levant Basin. Our investigations reveal a preponderance of Neoproterozoic and older Precambrian zircons with mostly negative εHf values. This U-Pb-Hf pattern indicates that the studied sediments were mainly reworked from Paleozoic-Mesozoic sandstones of Afro-Arabia with variable derivation from the juvenile basement of the Arabian-Nubian Shield. Comparison of the detrital signal in various stratigraphic levels of the Levant Basin shows that Early Oligocene and Early Miocene sand intervals are typified by a large proportion of pre-900 Ma zircons (ca. 50%), by a relatively small proportion of Neoproterozoic zircons with positive εHf values (ca. 25%), and by abundant detrital apatite peloids in the heavy mineral fraction. Resembling Miocene clastic sequences preserved in Israel, these characteristics are taken by us to indicate a dominant provenance in the Arabian side of the Red Sea Rift. On the other hand, Late Oligocene-lowest Early Miocene and Middle-Late Miocene intervals are typified by a mild proportion of pre-900 Ma zircon (ca. 35%) and by a larger proportion of Neoproterozoic zircons with positive εHf values (ca. 35%), they also contain scarce Mesozoic-Cenozoic zircons. These similarities to the Nile Delta sediments are taken by us to indicate a dominant provenance in NE Africa. Overall, our findings suggest that the Levant Basin was fed by varying proportions of sediments derived both from Arabia via the Levant continental margin and from NE Africa via the Nile Delta. While Early Oligocene and Early Miocene sediments, including the main section of the “Tamar Sands”, were chiefly derived from Arabian sources, Late Oligocene-lowest Early Miocene and Middle-Late Miocene sediments mainly sourced from NE Africa. The mere absence of Paleozoic and Mesozoic-aged detrital zircons, abundant in the Eurasian side of the Eastern Mediterranean, suggests that sand sourcing in the overriding plate of the Arabian-Eurasian collision belt did not reach the Levant Basin.

How to cite: Glazer, A., Avigad, D., Morag, N., and Gerdes, A.: The Oligocene and Miocene sands in the deep Levant Basin: Provenance and sediment routing, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8937, https://doi.org/10.5194/egusphere-egu23-8937, 2023.

15:40–15:42
Coffee break
Chairpersons: Marine Prieur, Camilo Esteban Gaitan, Rocio Jaimes-Gutierrez
16:15–16:25
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EGU23-15483
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GM4.3
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ECS
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On-site presentation
Delia Rösel, Martin Köhler, Anna Petts, and Thomas Zack

Mica, especially white mica, is a common detrital mineral in siliciclastic sediments and sedimentary rocks. It is used in provenance studies to constrain the thermal history and exhumation processes in the source region. It thus records valuable complementary provenance information to e.g. U-Pb geochronology of detrital zircon that date magmatic and high-grade metamorphic events in the provenance area.

However, in contrast to U-Pb geochronology of detrital zircon, there was a major disadvantage of using mica geochronology in provenance investigations until now: the conventional Argon-Argon (Ar-Ar) or Rubidium-Strontium (Rb-Sr) dating techniques are rather time-consuming due to complex sample preparation. Thus, of major interest for mica-based provenance studies is a recent improvement in in-situ Rb-Sr dating by laser ablation (LA) – inductively coupled plasma (ICP) - mass spectrometer (MS/MS) analyses. This analytical setup uses a reaction cell between two mass spectrometers. Induced gases allow the reaction of targeted masses and thus to chemically separating 87Rb and its daughter isotope 87Sr. This avoids the isobaric overlap during mass-spectrometric analysis. In combination with the novel approach of Rösel and Zack (2022) (GGR 46, 143-168), single-spot Rb-Sr ages can be calculated from individual detrital mica grains. Trace and major elements can be determined contamporaneously from the same laser spots. Consequently, LA-ICP-MS/MS analyses of detrital mica enables collecting of time and cost efficient multi-proxy datasets – a prerequisite for provenance studies.

In this contribution, we focus on (1) the analytical routine, (2) data reduction and age calculation strategy and (3) interpretation of in-situ Rb-Sr age and geochemical data from detral mica for provenance investigations. In-situ Rb-Sr LA-ICP-MS/MS dating was tested on detrital white mica from the Late Miocene Loxton Sand Formation, Murray Bain, South Australia. U-Pb dating from detrital zircon extracted from the same formation was performed for comparison.

How to cite: Rösel, D., Köhler, M., Petts, A., and Zack, T.: In-situ Rb-Sr dating of detrital mica and its application for provenance studies, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15483, https://doi.org/10.5194/egusphere-egu23-15483, 2023.

16:25–16:27
16:27–16:37
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EGU23-7725
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GM4.3
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ECS
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Highlight
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On-site presentation
Ekta Aggarwal, Sanjeev Gupta, and Alexander C. Whittaker

Flooding is one of the most devastating of natural disasters, occurring at varying spatial scales and leading to human and resource loss. Where the extent of flooding is large, satellite-derived data such as the NASA-derived DMSP, VIIRS, or the Black Marble nightlights data provide a useful approach for flood extent, flood exposure, and vulnerability. The recent floods in August 2022 on the Indus River, Pakistan is an example of a high-magnitude flood event. According to Pakistan’s National Disaster Management Authority (NDMA), around 33 million people were affected by the floods, and 8 million people were displaced.

To quantify exposure to flooding, we explore the use of nightlight data in determining flood vulnerability and human impact. We first associated lit pixels of the NASA DMSP nightlights data with channel pattern type and the proximity to the river in the Indus basin to provide an understanding of the influence of landscape parameters on human presence. Based on the hypothesis of preferential human presence near the river of the basin, we show that nightlight distribution is enhanced by 26% within the 0 to 5 km proximity of the river relative to the basin as a whole. This finding shows how human presence is concentrated in close proximity to the Indus River and its key tributaries.

To quantify the impact of the August 2022 floods we use NASA’s monthly and daily Black Marble night light data. We compare published flood extents with spatial and temporal variations in nightlights over similar areas to examine the impact of flooding on human presence. We use this to quantify the impact of the floods as measured in terms of the percentage of affected or reduced nightlight pixels and to estimate differential recovery time periods of the floodplain versus the non-floodplain area of the Indus river. The results will be compared with the population and demographics statistics of the area to provide information about flood exposure and vulnerability of different socio-economic groups within the flood plains. Our findings have the potential to aid improvement in our understanding of flood risk assessment and vulnerability and provide a framework for policymakers to assess flood vulnerability and impact at a basin scale.

How to cite: Aggarwal, E., Gupta, S., and Whittaker, A. C.: Nightlights as a tool to study flood exposure and vulnerability for the 2022 Indus River flood., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7725, https://doi.org/10.5194/egusphere-egu23-7725, 2023.

16:37–16:42
16:42–16:52
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EGU23-14525
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GM4.3
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On-site presentation
Philippos Garefalakis, Ariel do Prado, David Mair, Guilhem Amin Douillet, Franziska Nyffenegger, and Fritz Schlunegger

The grain size of coarse (>2mm) grained sedimentary particles can be determined by various methods such as Wolman-point or -grid counts on photos or directly in-situ, or upon sieving the material. Among the three perpendicular axes of a grain, transportation in the water flow direction usually occurs parallel to the intermediate b-axis, thus making this specific axis essential for hydraulic applications.

Determination of the length of the b-axis in recent deposits is straightforward because the longest a-axis and intermediate b-axis are visible from a top-view, while the shortest c-axis is oriented perpendicular to the riverbed surface. However, accumulation of river sediments either forms unconsolidated gravel commonly exposed as vertical steep walls (e.g., in gravel pits), or consolidated conglomerates which are commonly analyzed along stratigraphic sections. In contrast to recent deposits, the identification and measurement of specific grain axes within such ancient sedimentary deposits bear several limitations. These outcrops usually offer a view of the deposits perpendicular or oblique to the initial bedding of sediments, where either the a-/b- or b-/c-axes are visible, depending on the paleoflow direction. Furthermore, in such deposits, the embedding and possible occlusion of individual grains still prevent measurements of the full length of a specific axis. While in unconsolidated outcrops individual grains could be extracted for sieving, lithified deposits limit such approaches. Therefore, in consolidated outcrops, the longest visible axis of individual clasts is preferably measured through photo surveys. Although such surveys have been widely applied to lithified deposits, only a few studies evaluated the accuracy of such measurements and the relation of the longest visible grain axes to the b-axis.

Here, we compare and evaluate three different measuring techniques applied to coarse grains from outcrops in a gravel pit consisting of unconsolidated sediments with architectural and morphological similarities to conglomerates. We compared grain sizes and percentiles thereof measured by i) hand using a caliper (a-, b- and c-axes), ii) mechanical sieving of the material, and iii) measurements on digital images (longest and shortest visible axis). For the data collection on images, we compared two measuring techniques and tested if image-specific factors such as distortion effects have an influence on the results.

Our results show that sieving of the material (b-axis equivalent) yields datasets that can be best compared to measurements of the longest visible axis on images. In addition, both methods (sieving and images) yield underestimates of the length of the real b-axis by c. 15% if the grain size values determined with calipers are taken as reference. Additionally, grain size datasets are independent if grains are selected randomly on images or through a Wolman-grid approach. Furthermore, measurements are not significantly biased by possible image distortion effects for short-distance surveys (c. 1-1.5 m from outcrop) with hand-held cameras.

Finally, an underestimation of c. 15% of the length of the b-axis from images influences the outcomes of further applications (e.g. paleo-hydraulic calculations) that are based on grain size data. Therefore, we recommend these uncertainties to be considered for such applications.

How to cite: Garefalakis, P., do Prado, A., Mair, D., Douillet, G. A., Nyffenegger, F., and Schlunegger, F.: Grain size measurements from gravelly outcrops: Methods, uncertainties, and implications, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14525, https://doi.org/10.5194/egusphere-egu23-14525, 2023.

16:52–16:54
16:54–17:04
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EGU23-14437
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GM4.3
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ECS
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On-site presentation
Amanda Wild, Jean Braun, Alex Whittaker, Sébastien Castelltort, and Charlotte Fillon

Interpretation of the sedimentary record requires a thorough understanding of both external forcing and autogenic dynamics within sedimentary basins. This research analyzes the influence of autogenic and basin dynamics on grain size fining through landscape evolution modeling (Myr timescales) of a flexural foreland basin and observations from real-world basins with well-known underlying subsidence for comparison. In previous work, we have incorporated the Fedele and Paola (2007) self-similar gravel grain size method in two dimensions allowing for the formation of multichannels (2D) into the FastScape (Braun and Willett, 2013) landscape evolution model. We have validated this modelling approach against the self-similar grain size results of Duller et al. (2010) without multiple channels (1D). Here, we analyze different upstream precipitation and flexural elastic thicknesses (impacting the pattern and rate of subsidence) on the evolution of grain size fining, stratigraphic thickness, topography, and channel dynamics. We use real world scenarios with known underlying subsidence, grain size fining, and surface ages (such as the Grapevine Mountain fans of Death Valley) to compare with model results. Underlying subsidence controls on grain size have been well described by Duller et al. (2010), but never with the consideration of channel and topographic dynamics that vary the deposition rate relative to the subsidence rate across the basin. Braun (2022) has described the upstream area and precipitation influence relative to downstream on fan extents, but has not yet applied this to grain size fining trends. Our results show that multiple channels influence the grain size fining solution (more fining) compared to solutions with a single set channel pathway in conditions ranging from full sediment capture in the basin to full bypass, and these results vary depending on fan extents and the pattern of underlying subsidence. The model can be also used to estimate a variance range in grain size fining in which autogenic dynamics may be playing a greater role to statistically rule out or acknowledge a potential autogenic control induced by channel dynamics.

 

Braun & Willet (2013). Geomorphology: 180. Braun (2022). ESP: 10(2). Duller et al. (2010). JGR: ES 115(F3). Fedele & Paola (2007). JGR: ES 112(F2).

How to cite: Wild, A., Braun, J., Whittaker, A., Castelltort, S., and Fillon, C.: Basin Evolution Controls on Grain Size Fining: Beyond the 1D Solution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14437, https://doi.org/10.5194/egusphere-egu23-14437, 2023.

17:04–17:06
17:06–17:16
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EGU23-10232
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GM4.3
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ECS
|
On-site presentation
Sinead Lyster, Alexander Whittaker, Alexander Farnsworth, Gary Hampson, and Elizabeth Hajek

Quantitative investigations of ancient source-to-sink systems usually provide insights into either instantaneous conditions or mean conditions. Field-based channel palaeohydraulic approaches effectively recover instantaneous water discharges and sediment fluxes, whereas catchment- and regional-scale modelling approaches often recover mean annual water discharges and sediment fluxes, or mean discharges and fluxes on longer, million-year timescales. There is a critical gap between these timescales of investigation which reflects the intermittency of flow and sediment transport. However, at present, this gap is difficult to reconcile. In ancient source-to-sink systems, constraining the intermittency of flow and sediment transport is necessary to reconstruct water discharges and sediment fluxes and, therefore, investigate: (1) magnitudes and characteristics of ancient floods; (2) river behaviour in warmer palaeoclimates; (3) river response to climatic perturbation; and (4) catchment hydroclimate. Intermittency constraints are therefore crucial to decipher how landscapes evolved in response to tectonic and climatic forcing in the geological past. Here we take a multi-proxy approach to address this challenge. We combine fluvial stratigraphic datasets, flow and sediment transport models, and general circulation model (GCM) results to develop new methods to constrain intermittency in ancient source-to-sink systems. We illustrate these methods for ancient systems preserved in the Turonian Ferron Sandstone, USA, which records a Cretaceous greenhouse climate, and the Paleocene–Eocene Esplugafreda Formation and Claret Formation, Spain, which record the Paleocene–Eocene Thermal Maximum. To evaluate our methods, we compare our intermittency estimates with facies observations that reflect discharge regime and surface runoff regime, as well as terrestrial palaeoclimate proxies. We find these methods are effective and, further, we outline the necessary next steps to advance these methods. Our results demonstrate the potential to use multidisciplinary datasets to constrain intermittency and, therefore, the dynamics and evolution of ancient source-to-sink systems in response to tectonic and climatic forcing. Further, with continual advances in the use of GCMs to model palaeoclimates, our results highlight the potential to use GCMs to explore water discharges and sediment fluxes in systems where the rock record is incomplete or inaccessible.

How to cite: Lyster, S., Whittaker, A., Farnsworth, A., Hampson, G., and Hajek, E.: Constraining intermittency in the geological past: Implications for reconstructing water discharges and sediment fluxes in ancient source-to-sink systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10232, https://doi.org/10.5194/egusphere-egu23-10232, 2023.

17:16–17:18
17:18–17:28
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EGU23-5704
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GM4.3
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ECS
|
On-site presentation
Chloe Griffin, Robert Duller, and Kyle Straub

Tectonic, climatic, and anthropogenic forcing generate sediment flux signals that propagate across the Earth’s surface. Some of these signals get stored in strata but autogenic processes present in the Earth surface active layer can shred (i.e. degrade) and obscure many signals of environmental change prior to stratigraphic storage. In a landmark paper, Jerolmack and Paola (2010) use a numerical rice pile to show that autogenic events in the system saturate at a timescale Tx, which is noted to scale as L2/qinand corresponds to a red-to-white noise transition. The conceptual utility of this is that those environmental signals with periods less than Tx will experience shredding (unless signal magnitude overwhelms autogenic processes), while signals with periods greater than Tx would be detectable in the output. However, the relationships between signal shredding, preservation and detection are currently not established using physical experiments. Advancing on this work, we use a physical rice pile and find that power spectra generated from efflux time-series exhibit a tripartite geometry defined by red, white and blue noise. The transition between each regime defines two key autogenic timescales: Trwand Twb. Trw is defined by the red-to-white noise transition, setting upper bounds on signal degradation, and represents Tx on the power spectra of Jerolmack and Paola (2010), but does not scale with qin. Whereas signals greater than Twb, which scales with qin,are unobscured by autogenic noise and show enhanced detectability in the power spectra. We emphasize that while signals greater than Trw do not experience degradation, they can still be obscured by autogenic noise, unless signal period is greater than Twb. This framework can be used to predict the severity of shredding as signals propagate through the Earth surface active layer, and establish robust confidence limits of signal detectability in landscapes and strata.

How to cite: Griffin, C., Duller, R., and Straub, K.: Detecting Shredded Signals in a Physical Avalanching Rice Pile, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5704, https://doi.org/10.5194/egusphere-egu23-5704, 2023.

17:28–17:30
17:30–17:50
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EGU23-8413
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GM4.3
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ECS
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solicited
|
On-site presentation
Aneesa Ijaz Rabbani, Dr Janok Bhattacharya, Dr Beth Parker, and Julie Zettl

The Cretaceous Dunvegan Formation in the Western Canada Sedimentary Basin is a well-characterized source-to sink system that extends for about 1000 km from proximal gravelly alluvial systems in the Liard Basin, Northwest Territories, to well-developed sandy deltaic and prodelta muddy shelf systems in Alberta. The mud to sand transition has been well-documented and the sandy deltas have been shown to be fed by tributive incised valley systems driven by cycles of high frequency sea-level change. These incised valleys in turn pass landward into the conglomerate alluvial systems, but the nature of these conglomerates and the controls on the gravel-sand transition have not been well examined.

Dunvegan conglomerates in outcrops in the Liard Basin are moderately-sorted and well- rounded reaching up to small cobbles in size. These have previously been interpreted as alluvial fans; however, our investigations show a domination of sharp to scoured based meters-thick fining upward facies successions consisting of dune- and bar- scale cross stratification. The conglomeratic units comprise highly amalgamated channel belt deposits that form cliff exposures that are about 70 m high. There is an absence of debris flows or of sedimentary structures characteristic of supercritical flows, and we thus interpret these as likely deposited by meters-deep lower-gradient gravel-bed streams, rather than steep-gradient, sheet-flood dominated alluvial fans.

Trunk channels in the sink area, farther to the southeast are associated with incised valleys and have a mean bankfull depth of 10-15 m, carry medium sand (< 200 microns) with slopes estimated to be on the order of 6x 10-5. Source to sink calculations indicate a back-water length of around 200 kilometers. Based on paleogeographic reconstructions, the conglomerates appear to have been deposited 300 to 500 km from the mapped deltaic shorelines, indicating that the gravel sand transition is not related to the back water and is likely not controlled by sea-level changes, thought to be important in generating the incised valleys in the sink area. 

The conglomerates appear to be confined within the Liard Basin, which is bounded to the east by the Bovie Fault, expressed as a major kilometer-throw normal fault. The Bovie structure was long-lived and may have been active throughout Dunvegan time. Hence, excess accommodation, driven by movement on the Bovie Fault may have prevented gravel from escaping into the more distal parts of the Western Canada Sedimentary basin.  

This is in contrast to other clastic wedges in the Cretaceous Interior Seaway, such as the Frontier and Cardium formations, that contain conglomeratic shoreline and shelf deposits and may indicate steeper gradient S2S systems.

Tectonics and climate in the Dunvegan drainage basin may not have been linked to processes downstream because of the Bovie Fault. Despite clear evidence of downstream sea-level controls in the Dunvegan sink, it does not appear that these signals were able to propagate upstream.

How to cite: Rabbani, A. I., Bhattacharya, D. J., Parker, D. B., and Zettl, J.: Evaluating Backwater versus Upstream Tectonic Controls on the Gravel-Sand Transition, Cretaceous Dunvegan Formation, Western Canada Sedimentary Basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8413, https://doi.org/10.5194/egusphere-egu23-8413, 2023.

17:50–17:53

Posters on site: Fri, 28 Apr, 08:30–10:15 | Hall X3

Chairpersons: Rocio Jaimes-Gutierrez, Marine Prieur, Philémon Juvany
X3.17
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EGU23-1915
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GM4.3
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ECS
|
Aurora Garcia, Benjamin Bellwald, Ivar Midtkandal, Sverre Planke, Ingrid Anell, Pietro Sternai, and Reidun Myklebust

To understand the dynamics of the Fennoscandian Ice Sheet, extensive studies have been done on the Norwegian Channel which was formed by intense ice streaming activity throughout the Quaternary. However, the understanding of trough mouth fans developed in front of such ice streams is still evolving, with recent research showing the importance of meltwater in the transport and deposition of sediments into the depocenter. This study focus on characterizing the deposits of the last glacial highstand and previous interglacial period at the North Sea Fan in order to unravel the predominant sedimentary processes and paleo-geographical configuration since Marine Isotope Stage 6 (last 130ka). We use over 14000km2 of high-resolution 3D seismic reflection data (vertical resolution of 2m and bin size of 6.25 x 18.75m) covering the slope and shelf break to map six surfaces and delimitate five seismic units. The stratigraphy of the section comprehends over 600 meters of sediments in the thickest part of the fan, spanning from the top of the Tampen Slide to the seabed. The lowermost units, U1 and U2, have similar seismic facies (continuous low amplitude reflections, with increasing contrast towards the head and sidewall of the Tampen Slide) but different geometries: U1 is tabular and covers the entire study area whereas U2 have a lenticular body and is limited to the northernmost part. U3 is characterized by a combination of chaotic, transparent, deformed and parallel seismic facies and is divided into four subunits by high-amplitude reflections that can be mapped throughout the dataset. Within U3, channels were described and grouped into five categories based on their morphologies and infill. Overall, the channels vary in width from tens of meters to > 2km, with depths reaching up to 105 meters. They can exceed 100km in length and have extremely low sinuosity (max. 1.05). U4 is the uppermost unit on the slope, characterized by transparent seismic facies close to the paleo-shelf, with parallel to undulating continuous reflections downslope where the thickness of the unit decreases. Two of the five types of channels are observed within this unit, as well as pockmark fields. On the shelf, U5 represents a thin wedge-shaped package with few internal reflections. Multiple iceberg ploughmarks, iceberg pits and mega-scale glacial lineations are identified, eroding into the unit. The different units represent different sedimentary processes and periods within a glacial cycle: U1 and U2 are the products of contour currents during the interglacial period after the failure of the Tampen Slide; U3 is deposited during the glacial maximum (23-19ka) mainly by meltwater turbidites and subordinately glacigenic debris flows; U4 represents the deglacial period on the slope, where the suspended load from the meltwater turbidites and ice rafted debris were deposited; U5 represents the deglacial period on the shelf, with deposition of subglacial tills. The deposits account for a big percentage of 2km thick fan, especially when considering the short deposition period of ~123 years, highlighting the variability and intensity of active processes at the North Sea Trough Mouth Fan during the Weichselian glaciation.

How to cite: Garcia, A., Bellwald, B., Midtkandal, I., Planke, S., Anell, I., Sternai, P., and Myklebust, R.: The stratigraphy of a glacial cycle: a study case of the Weichselian deposits of the North Sea Fan, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1915, https://doi.org/10.5194/egusphere-egu23-1915, 2023.

X3.18
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EGU23-3311
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GM4.3
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ECS
Lucas Vimpere, Sébastien Castelltort, Pietro Sternai, and Pierre Bouilhol

 

Since the industrial revolution, the constant increase in atmospheric CO2 had pivotal impacts on global climate with current concentrations being the highest of the last 800 ka. In order to better understand the Earth system and the future evolution of climates, it is essential to study past hyperthermals during which global surface temperature dramatically increased above present levels. The Himalaya arose from the biggest known continental collision and has been associated with a bustling volcanism, which most likely steered the global warming (+12-14 °C) during the Early Eocene Climatic Optimum (EECO).

We here present the analytic strategy that will be implemented to quantify the carbon cycle within the Kohistan-Ladakh forearc sediments. Whilst the CO2 input (warming) in the atmosphere related to the intensity of subduction magmatism will be quantified using the mercury isotopes, the CO2 sink (cooling) induced by continental alteration of the exhumed units will be studied through different isotopic analyses (e.g., Hf, Nd, Sr). The stratigraphy and the reconstruction of depositional environments will be assessed through conventional field surveys and various dating methods such as, detrital zircon, nannofossils, radiolarians, and calibrated carbon isotopic curves. The overall objective is to establish the influence of the collisional Himalayan chain on global climate changes.

How to cite: Vimpere, L., Castelltort, S., Sternai, P., and Bouilhol, P.: Tethys carbon cycle, India-Eurasia collision, and Cenozoic climate evolution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3311, https://doi.org/10.5194/egusphere-egu23-3311, 2023.

X3.19
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EGU23-7821
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GM4.3
|
ECS
Iwan Setiawan, François Guillocheau, Cécile Robin, and Jean Braun

Nile River, the longest river in the world (>6,500 km), has been studied since long time ago tracing back to the fifth century yet the timing of origin of its present-day drainage is still disputed. There are two end-members of notions of the birth of the Nile, the first one believes that the present-day Nile has been connected to the Ethiopian Plateau since ~30 Ma, while the other supports the idea of young Nile around ~6 Ma. The Nile crosses today two former endorheic systems (Sudanese and Albertine “Basins”) and one exorheic system (Tethys Margin) before finally depositing sediments in the Mediterranean Sea. Our objective here focuses on deciphering the source-to-sink scenario of the Nile through relief growth, tectonic, and climate since the uppermost Cretaceous.

The timing of the uplifts and deformation wavelengths are constrained by characterizing and mapping several generations of stepped pediments on DEM and satellite images which then dated using their geometrical relationships with dated magmatic rocks. Additionally, stratigraphic records of the sedimentary basins were studied to complement the dating of the pediments. The authenticity of the approaches is to integrate those data enclosing all the source-to-sink (S2S) systems to construct a coherent scenario of the Nile paleorouting systems especially on the dynamics of its sediment sources.

We proposed the following model for the S2S of the Nile where its catchment grew larger southwards through time. First, a significant deformation occurred around the Cretaceous-Paleogene boundary (66 Ma) with the uplift of western limit of the Nile catchment, the Darfur-Ennedi-Tibesti domains, followed by the formation of a main large pediment. Second, this pediment was then flooded during late Paleocene (58-57 Ma) until a subtle high bounding northward the endorheic Sudanese “Basin”. Consequently, carbonate platforms were widely deposited from Paleocene until middle Eocene in the Egypt extending southwards to the former Hudi Lakes in northeast Sudan and there was no siliciclastic supply for the Nile during that time. Third, the first evidence of a fluvial system (“Pre-Eonile” according to Said, 1981) was discovered during late Eocene (~37 Ma) by large channel incisions on top of the carbonate platforms. Contemporaneously, the Uweinat Dome was uplifted and likely acted as the main siliciclastic source during late Eocene to Oligocene. Fourth, the initiation of Red Sea rifts during the Oligocene followed by a major uplift at the scale of north-east Africa (~10 Ma) provoked another plausible siliciclastic source, the Red Sea Hill’s flanks, in addition to the Uweinat Dome. Fifth, during the capture of the Sudanese endorheic system in the Early Pliocene (~4 Ma), the Nile catchment grew significantly larger and the sources were actively provided by the Darfur and Ethiopian Plateau. Finally, during middle-late Pleistocene (< 1 Ma) the Nile completed its present-day catchment by capturing the Albertine endorheic system and the siliciclastic sediments were supplied by the Ethiopian Plateau and the East African Dome.

How to cite: Setiawan, I., Guillocheau, F., Robin, C., and Braun, J.: Source-to-sink system evolution of the Nile since 70 Ma, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7821, https://doi.org/10.5194/egusphere-egu23-7821, 2023.

X3.20
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EGU23-12957
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GM4.3
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ECS
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Panagiotis Athanasios Giannenas, Cécile Robin, François Guillocheau, Benjamin Gréselle, and Emmanuelle Vennin

In order to understand the effects of the OAE1a on the sedimentary system in a Source to Sink approach, we studied the Late Barremian-Aptian sediments of the Wessex-Channel and Weald Basins and present a synthesis of the sequence stratigraphic framework and sedimentary patterns of the siliciclastic system developed during this time interval. We present a regional and detailed sequence stratigraphic model for the Lower Greensand Group and provide new stratigraphic insights.

This synthesis is based on field work (Isle of Wight) with focus on defining sedimentological and stratigraphic signatures using facies analysis and is coupled with published datasets and studies on bio- chemo-stratigraphy. The results are integrated with well-logs correlations for regional scale understanding.

It presents updated composite lithostratigraphic logs for three areas of the island which are correlated and provide a better 3D understanding for this part of the basin. The analysis and interpretation of the well database (84 petroleum exploration wells) contributed to understanding the regional architecture including the extent, facies distributions and thickness variations of the sediments. The sequence stratigraphic model includes 3rd order (composite) sequences within the context of 2nd order super-sequences and a nomenclature in support of the model was proposed. Also, on the Isle of Wight, we present how the sedimentary system along with the relative sea level variations additionally recorded significant changes in terms of depositional environments. Finally, the applicability of the sequence stratigraphic model will be examined on a global scale for the proposal of a unified regional nomenclature in accordance with the global understanding of eustatic variations. Therefore, a long-distance correlation with already established schemes will be performed including France, Spain, the Southern Tethyan margin (Tunisia) and the Arabian plate.

The project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No 860383 (https://www.s2s-future.eu/).

How to cite: Giannenas, P. A., Robin, C., Guillocheau, F., Gréselle, B., and Vennin, E.: Sequence stratigraphic synthesis of the Late Barremian-Aptian of the Wessex-Channel and Weald Basins: Insights from well-logs correlations and outcrop-based field geological studies, Isle of Wight, Southern England, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12957, https://doi.org/10.5194/egusphere-egu23-12957, 2023.

X3.21
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EGU23-6625
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GM4.3
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ECS
Philémon Juvany, Miguel Garcés, Cécile Robin, Miguel López-Blanco, Romain Pellen, Charlotte Fillon, and Josep Anton Muñoz De La Fuente

The Pyrenean system has been largely studied in its globality from the tectono-sedimentary evolution of the retro and pro-foreland basins (sinks) to the exhumation history of the Axial Zone (sources) constrained by thermochronological studies.  The present estimation of the siliciclastic sediment volumes from the entire South Pyrenean pro-foreland basin completes the recent measurements made from the Aquitanian retro-foreland basin by using the same methodology. A re-evaluated complete budget of the deposited material in the southern foreland basins (South Pyrenean zone, Ebro basin and Valencia gulf) derived exclusively from the Pyrenean domain is proposed for the Early Eocene-Holocene period (56-0 Ma). Measurement of the compacted siliciclastic sediment volume is based on isopach maps (thickness maps) from Lanaja., 1987 for the Ebro and South Pyrenean zone, while volumes of the Valencia gulf were calculated from R. Pellen 2016.

The volumes from the Eocene period (56-33.9Ma) will allow comparison of deposited siliciclastic sediments in both northern and southern sinks and the eroded volumes at the scale of the entire orogen (obtained from the interpolation of compiled thermochronological data) in the light of a source to sink approach.

References:

Lanaja, J. M. (1987). Contribución de la exploración petrolífera al conocimiento de la geología de España. IGME.

Pellen Romain (2016). Géodynamique et impact de la crise d'érosion et de salinité Messinienne sur les transferts sédimentaires (bassins de Valence et Adriatique). PhD Thesis, Université Bretagne Loire. https://archimer.ifremer.fr/doc/00406/51714/

How to cite: Juvany, P., Garcés, M., Robin, C., López-Blanco, M., Pellen, R., Fillon, C., and Muñoz De La Fuente, J. A.: Siliciclastic sediment volumes of the South-Pyrenean pro-foreland basin: Eocene exhumation and Source to Sink approach., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6625, https://doi.org/10.5194/egusphere-egu23-6625, 2023.

X3.22
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EGU23-15839
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GM4.3
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ECS
Marine Prieur, Perach Nuriel, Alexander C. Whittaker, Fritz Schlunegger, Tor O. Somme, Jean Braun, Charlotte Fillon, and Sébastien Castelltort

Climate is a primary driver of sedimentary processes from source to sink. A key challenge for stratigraphic studies in deep time is to constrain how perturbations of hydroclimate in the past have affected surface processes and source-to-sink dynamics. In modern fluvial systems, precipitation and the global hydrological cycles are fundamental determinants of sediment production, transport and deposition, and have also long been shown to exert major influence on river channel dynamics. For instance, recent works suggest that increased seasonality in precipitation could enhance lateral river dynamics, through less-frequent but higher-energy flood events and decreased bank stability associated to droughts and vegetation decline. In such settings, channel mobility has more impact than water discharge on the export of fine sediments downsystem, hence predicting specific stratigraphic patterns potentially diagnostic of hydroclimate perturbations in deep time.

This hypothesis has been tested by paleohydraulic reconstructions and estimates of avulsion occurrences based on facies analyses, but lacks direct assessment of the intensity of floodplain reworking. Therefore, to further test this hypothesis, we propose to quantify the degree of floodplain reworking by looking at the amount and spatial distribution of floodplain elements contained in fluvial to coastal sandstones within a source-to-sink system during an important climate perturbation.

Our study focuses on the Paleocene-Eocene Thermal Maximum (PETM, 56Myr) in the Southern Pyrenees (Tremp-Graus Basin, Spain). Several authors described the PETM in many localities over the area, showing a widespread deposition of an anomalously thick conglomeratic interval suggesting a perturbation of the fluvial channel dynamics at that time. We point-counted the content of 45 sandstone samples that span the pre-, syn- and post-PETM intervals in continental channels to deltas and carbonated platform depositional environments. Reworked floodplain was identified by the presence of microcodiums and carbonate nodules. To assess whether these elements were reworked from floodplain significantly older (erosion of underlying layers) or contemporaneous (lateral erosion by channel migration), we attempted LA-MC-ICPMS U-Pb dating on carbonates. Preliminary results show an increase of the amount of reworked floodplain in distal environments during the PETM climatic event. This observation is in adequation with other studies predicting a link between enhanced seasonality during global warming and channel migration rate, and provides a new way of assessing and testing fluvial dynamics in deep time as a proxy for perturbations of ancient hydroclimates.

How to cite: Prieur, M., Nuriel, P., C. Whittaker, A., Schlunegger, F., O. Somme, T., Braun, J., Fillon, C., and Castelltort, S.: Enhanced channel mobility assessed from the preservation of floodplain elements in fluvial to coastal sandstones: An example from the Paleocene Eocene Thermal Maximum (PETM) in the Southern Pyrenees (Spain), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15839, https://doi.org/10.5194/egusphere-egu23-15839, 2023.

X3.23
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EGU23-3986
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GM4.3
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ECS
Nahin Rezwan, Alexander Whittaker, Sanjeev Gupta, Sébastien Castelltort, Fritz Schlunegger, Jean Braun, Tor Sømme, Jonah Mcleod, and Joel Hook

Stratigraphy represents a physical record of the behavior of source to sink sedimentary systems in the geological past. Grain-size fining in stratigraphy toward the downstream direction is driven by the sediment supply, subsidence rate and accommodation space generation. In principle these grain size trends can be inverted to quantify the temporal and spatial variation in these driving forces. This work addresses this challenge to understand how stratigraphic grain size fining reflects sediment flux and accommodation space generation in a normal fault bounded sedimentary system in the Gulf of Corinth, Greece. A SW to NE 2.6 km exposed natural cliff cut section of the middle Pleistocene Kerinitis Gilbert type delta has been selected for its accessibility, where the stratigraphic units are traceable, and where the timing of sediment deposition is well constrained (500 to 800 ka). The qualitative evolution of the fault is also understood as the three mapped depositional packages (lower part, middle part and the upper part) in the Kerinitis delta are thought to represent the initiation, development, and termination of the Pirgaki-Marmoussia fault. Down-system grain size data has been collected using the Wolman point count method at 25 measurement stations, predominantly from fluvial top-sets following for several timelines. Furthermore, high-resolution grain size photographs have been captured to study the inaccessible higher stratigraphic units. Paleoflow direction is reconstructed using a pebble imbrication dataset, which indicates the source to sink direction. For the grain size datasets, we have applied several self-similarity tests to evaluate the mutual relationship among the datasets. Our result shows that almost all the datasets exhibit significantly self-similarity with each other. We reconstruct grain size fining trends for each of the units, which we quantitatively relate to the spatial distribution of subsidence and sediment flux using a self-similarity based fining model. Our analysis gives new insights into the evolution of the delta bounding Pirgaki-Marmoussia fault and show how grain size data can be used to reconstruct landscape dynamics in the past.

How to cite: Rezwan, N., Whittaker, A., Gupta, S., Castelltort, S., Schlunegger, F., Braun, J., Sømme, T., Mcleod, J., and Hook, J.: Decoding downstream trends in stratigraphic grain size distribution: examples from the Kerinitis Gilbert type delta, Greece., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3986, https://doi.org/10.5194/egusphere-egu23-3986, 2023.

X3.24
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EGU23-6953
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GM4.3
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ECS
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Ariel do Prado, David Mair, Philippos Garefalakis, Chantal Schmidt, Alexander Whittaker, Sébastien Castelltort, and Fritz Schlunegger

The construction of check dams is a common human practice around the world where the aim is to reduce the damage by flooding events through mountain streams. However, quantifying the effectiveness of such engineering structures has remained very challenging and requires a specific case study, since it is very sensitive to the geometrical, geological, and climatical conditions. One key parameter to measure the check dams’ effectiveness is to quantify the change in the amount of the bedload carried by the stream after the check dam construction. A permanent lowering of this parameter not only points to success in reducing the probability of sediment transport occurrence but also implies that the catchment sediment input into the system is likely to decrease. Here, classical methods to estimate the sediment transport in a stream depend on measurements of the riverbed slope, grain size percentiles, water discharge, and channel widths. In this work, we selected the Gürbe River situated in the Swiss Alps as a case study, which has been engineered with more than 110 check dams along a c. 5 km reach where sediment has been continuously supplied from adjacent hillslopes, primarily by landsliding. We measured the riverbed grain size, energy gradients, and river widths within selected segments along this reach. Additionally, a gauging station downstream of the check dams yielded information to calibrate the hydroclimatic situation, thus yielding ideal conditions for our catchment scale experiment. Using the acquired data and the historical runoff dataset covering the time interval between 2009 and 2021, we estimated a total volume of bedload transport ranging from 1.0x104 to 7.0x104 m3 over this period. These estimates are consistent with previous studies in this catchment (Delunel et al., 2020; Ramirez et al., 2022), thereby validating our approach. We then envisaged possible channel geometries for the time before the check dams were constructed. We considered (1) higher energy gradients for the scale of the check dams, representing a proxy for the river slope under natural conditions, (2) channel widths that are smaller than those measured today, thereby anticipating that the channel was more confined in the past due to lateral sediment supply by landslides, and (3) larger grain size percentiles, which we consider to be similar to the values measured from preserved landslides in the region. Using such potential natural scenarios as constraints, we found a significant increase in the predicted bedload in comparison with the current situation, and we calculated a total bedload transport ranging from 7.0x105 to 6.0x306 m3 for a period of 13 years. These results suggest that the check dams in the Gürbe River are highly efficient not only in decreasing the probability of torrents with high sediment flux but also in stabilizing the channel bed by avoiding incision. The most likely consequence is a stabilization of the terrain around it by reducing the landslide occurrence. 

How to cite: do Prado, A., Mair, D., Garefalakis, P., Schmidt, C., Whittaker, A., Castelltort, S., and Schlunegger, F.: Check dam impact on sediment load: a catchment scale experiment from the Gurbe River, Swiss Alps, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6953, https://doi.org/10.5194/egusphere-egu23-6953, 2023.

X3.25
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EGU23-14952
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GM4.3
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ECS
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Ewerton da Silva Guimarães, Cornelis Kasse, Freek S. Busschers, Naki Akçar, Duna Roda-Boluda, Fritz Schlunegger, Renaud Bouroullec, Alain Demoulin, Marcus Christl, Christof Vockenhuber, and Ronald T. van Balen

River terrace deposits are excellent archives of paleoenvironmental conditions. They reflect the tectonic and climatic settings of their time of formation. For this reason, Late-Pleistocene and Holocene terraces have been previously studied in detail because of their good state of preservation and age control. However, less is known about the Middle- and Early-Pleistocene terraces. The Lower Meuse River, a major tributary of the Rhine River, located in the Southern Netherlands, exhibits a well-preserved terrace staircase which, for decades, has been intensely investigated. Age constraints are available, which are mainly based on correlations to the marine isotope record. As of late, the availability of numerical ages of these terraces have been increasing, allowing for a better determination of the boundaries of the Early, Middle and Late Pleistocene terraces.

In order to better understand the effects of the Mid-Pleistocene Transition (MPT; 1.2 – 0.8 Ma) in the Meuse River, we improved the spatial and temporal resolution of the terraces of the Lower Meuse. For the spatial resolution, we used a dense borehole database to characterize key geometrical and compositional parameters of the different terrace levels. For the temporal resolution, we used cosmogenic-nuclide geochronological methods, relying on the measurements of the paired isotopes 26Al-10Be, allowing for the estimation of terraces burial age.

In this work we outline general spatial trends of geometrical and compositional parameters of terraces formed pre-, syn-, and post-MPT. These results are displayed in an improved time framework that relies upon the new burial ages results from the cosmogenic nuclides concentration measured for specific terrace levels. We present three new isochron-burial ages from Main Terrace levels, and thirteen new simple-burial ages from Middle-, Main-, and East Meuse-Terraces.

The results allow us to better understand the signal propagation generated by the MPT. A general increasing trend in the gravel content and terrace thickness have been observed from older to younger terraces. The ages are mostly in good agreement (within uncertainty) with previously proposed age models, especially the ages for the East Meuse Terraces, which have been confirmed to be Early Pleistocene.

How to cite: da Silva Guimarães, E., Kasse, C., Busschers, F. S., Akçar, N., Roda-Boluda, D., Schlunegger, F., Bouroullec, R., Demoulin, A., Christl, M., Vockenhuber, C., and van Balen, R. T.: Impact of the Mid-Pleistocene Transition on Meuse River Terraces in the Southern Netherlands: New Terrace Burial Ages, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14952, https://doi.org/10.5194/egusphere-egu23-14952, 2023.

X3.26
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EGU23-14972
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GM4.3
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ECS
Camilo Esteban Gaitan, Emmanuelle Pucéat, Pierre Pellenard, Thierry Adatte, Germain Bayon, Cécile Robin, and François Guillocheau

Recent studies have coupled the Lu-Hf and Sm-Nd isotopic systems on clay fractions to assess the evolution of chemical weathering in both ancient and modern environments. Results of this proxy in the abyssal plain of the Cape Basin in Southwestern Africa show a concomitant increase of chemical weathering and physical erosion in response to a late Cretaceous tectonic uplift. In this study, we performed analyses on sediments in the continental slope of the basin that show significant differences compared to the abyssal plain: A long-steady decrease in quartz simultaneous to an increase in the calcite content during the late Cretaceous; a lower content of detrital smectite throughout the section; and the presence of mixed layer assemblages of illite – smectite (R0 or R1) and vermiculite – chlorite during the early-late Cretaceous transition, coinciding with the period of low carbonate content. First, these differences indicate a variation in the input of siliciclastic material and a change in the carbonate compensation depth. Second, clay assemblages reveal a burial diagenetic influence compared to those recorded in the abyssal domain, likely due to thicker deposition in the continental slope. These diagenetic processes indicate that there is a perturbation in the chemical weathering signal at the continental slope, therefore the disparities between the denudation record on clays in both segments cannot be attributed to an effect of signal propagation due to this post-deposition processes.

How to cite: Gaitan, C. E., Pucéat, E., Pellenard, P., Adatte, T., Bayon, G., Robin, C., and Guillocheau, F.: Diagenetic effects in Hf-Nd isotopic compositions on clay fractions: Source-to-sink analysis of signal perturbation in denudation records, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14972, https://doi.org/10.5194/egusphere-egu23-14972, 2023.

X3.27
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EGU23-6886
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GM4.3
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ECS
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Caroline Fenske, Jean Braun, François Guillocheau, and Cécile Robin

Duricrusts are hard elemental layers forming in tropical and subtropical regions. Different types of duricrusts exist, including calcretes, silcretes and ferricretes (or iron duricrusts), that differ by their composition and, most likely, their formation mechanism. In places such as Africa, Australia or Brazil, we can observe them capping hills and protecting landscapes, thus being an important part of regional geomorphology. Their formation is highly dependent on climate and requires strong seasonal precipitation cycles, enabling transport and accumulation of elements during wet seasons and precipitation and hardening during dry seasons. However, it is also known that duricrusts form in tectonically quiet environments, and multiple tens of thousands of years are needed to form centimetres to metres thick elemental layers. 

Two hypotheses for duricrust formation exist, namely the water table (or horizontal) hypothesis and the laterite (or vertical) hypothesis. Yet, until recently, no quantitative (numerical) model exists that represents either of them. We presented last year (Fenske et al, 2022) a model based on the water table hypothesis. Here we present a second model based on the laterite hypothesis and compare the predictions of the two models. Although the models we propose are potentially applicable to a wide range of duricrusts, we will concentrate here on the formation of ferricretes.

Laterites are a type of regolith covering around 33\% of land surfaces. The thickest lateritic profiles are found in the centre of continental cratons, where they evolved for millions of years. The main process responsible for laterisation is weathering, the process transforming bedrock into regolith. During weathering rocks progressively lose their structure, elements are dissolved, re-precipitated, leached, or transported, leading to progressive porification and compaction. Subsequently, from the weathering front to the surface, a typical lateritic profile is made of coarse grained and then fine grained saprolite, a mottled zone and at the top, an indurated cover, the ferricrete. 

We recently developed a numerical model for duricrust formation according to the laterisation hypothesis (LT model). In this model, iron duricrusts are genetically linked to the bed rock. Material from the bedrock are transformed and leached within a given vertical column of rocks but are also moved vertically due to tectonic uplift. We assume that as the regolith ages, it undergoes a process of transformation that is proportional to mean fluid flow and that leads to hardening and compaction. As material is constantly removed from the regolith layer, the model is dependant on a constant material input (through uplift and, potentially, surface erosion) to reach sufficient laterisation for ferricrete formation.     
Comparing predictions of the laterisation (LT) model to those of the water table (WT) model, we observe that they require slightly different tectonic regime, with the WT model most efficient during period of complete quiescence and the LT model needing a slow constant rate of base level fall to produce duricrusts. The two models also differ by the geometry of the duricrusts they predict and, in particular, the depth at which duricrust forms in the regolith (at or above the water table level).

How to cite: Fenske, C., Braun, J., Guillocheau, F., and Robin, C.: Comparing Models for Duricrust Formation in Tropical and Subtropical Areas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6886, https://doi.org/10.5194/egusphere-egu23-6886, 2023.

X3.28
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EGU23-12682
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GM4.3
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ECS
Rocio Jaimes-Gutierrez, Emmanuelle Puceat, Thierry Adatte, David J. Wilson, Philip Pogge von Strandmann, Justine Blondet, and Sebastien Castelltort

We explore the feedback mechanisms at play during the climate recovery of the Paleocene Eocene Thermal Maximum (PETM) in a continental section of the Spanish Pyrenees, the Esplugafreda section. We combine isotopic and mineralogical proxies to assess the changes in the chemical weathering intensity and regime and explore their implications in this mid-latitude catchment. The changes in the clay mineral assemblages in two size fractions (<0.5 µm and 0.5-2 µm) were examined as paleoclimatic proxies. We also used these fractions to study the combined Sm-Nd and Lu-Hf radiogenic isotope systems to constrain the clay provenance and chemical weathering intensity. Furthermore, we measured lithium isotopes in the bulk clays to assess local changes in the weathering regime and clay neoformation during the PETM.

The clay mineralogy reveals an interplay between detrital clay input during extreme events and more hydrolyzing conditions reflected in the presence of pedogenetic smectites during the onset and body of the PETM. The extent to which the clay samples deviate from the clay array (ΔεHf) show no variations throughout the section, indicating no increase in the chemical weathering intensity. Nonetheless, the δ7Li values show a distinct negative excursion during the recovery of the PETM in the Esplugafreda section. This excursion is coeval with an increase in the proportions of illite and chlorite relative to smectite, an indicator of increasing physical erosion.

Our results suggest that the low surface reactivity of the floodplain deposit sediments resulted in negligible variations in the chemical weathering intensity recorded in the clays. Yet, the floodplain soils saw more fractionated lithium isotope compositions, contemporary with an increase in the detrital nature of the clay minerals. Climate change in the region was characterized by a substantial temperature increase with massive but short precipitation events, resulting in efficient sediment transport. Although weathering in the Pyrenees was kinetic-limited, both chemical weathering and physical erosion played a role in the climate recovery to pre-PETM conditions. Rapid climatic changes and their impact on the geological record are of utmost importance for understanding ongoing global warming and the associated feedback mechanisms on environmental conditions.

How to cite: Jaimes-Gutierrez, R., Puceat, E., Adatte, T., Wilson, D. J., Pogge von Strandmann, P., Blondet, J., and Castelltort, S.: Chemical weathering during the PETM: Insights from stable and radiogenic isotopes in the Spanish Pyrenees, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12682, https://doi.org/10.5194/egusphere-egu23-12682, 2023.

Posters virtual: Fri, 28 Apr, 08:30–10:15 | vHall SSP/GM

Chairpersons: Iwan Setiawan, Camilo Esteban Gaitan
vSG.3
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EGU23-1706
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GM4.3
Gaoyuan Sun and Shurui Li

The radial sand ridges (RSRs) off the Jiangsu coastal zone, East China, is a large special sedimentary landform formed by land-ocean interactions. Its sedimentary provenance is a scientific issue worthy of attention. However, there still existed some debates on the provenance or which source is the dominant to the RSRs. To constrain the provenance of the RSRs, the in-situ micro-area X-ray fluorescence spectroscopy, the statistics of heavy minerals and the detrital zircon U-Pb geochronology are employed in this study. The results show that the heavy mineral combination of the RSRs is amphibole-epidote-iron oxide minerals, and the content of amphibole is much higher than that of epidote. The detrital zircon U-Pb ages yield five significant age ranges of 160-330 Ma (22.89 %, peaking at ~200 Ma), 350-550 Ma (18.61 %, peaking at ~430 Ma), 650-1200 Ma (29.32 %, peaking at ~750-800 Ma), 1700-2000 Ma (10.58 %, peaking at ~1850 Ma) and 2400-2600 Ma (5.09 %, peaking at ~2500 Ma). Through the comparison with the potential source area, we found a strong similarity of the heavy mineral combination and zircon U-Pb ages between the RSRs and Yangtze River (YtR), indicating the YtR as the major source for the RSRs. In addition, the sediments of the ancient Yellow River Delta (AYRD) could have limited impacts on the coast of northern Jiangsu, while the modern Yellow River (YR) possibly only influences the northern edge of the RSRs.

How to cite: Sun, G. and Li, S.: The provenance of radial sand ridges off the Jiangsu coast, East China: Constraints from the heavy mineral compositions and zircon geochronology, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1706, https://doi.org/10.5194/egusphere-egu23-1706, 2023.