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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 T_x, which is noted to scale as L²/q_inand corresponds to a red-to-white noise transition. The conceptual utility of this is that those environmental signals with periods less than T_x will experience shredding (unless signal magnitude overwhelms autogenic processes), while signals with periods greater than T_x 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: T_rwand T_wb. T_rw is defined by the red-to-white noise transition, setting upper bounds on signal degradation, and represents T_x on the power spectra of Jerolmack and Paola (2010), but does not scale with q_in. Whereas signals greater than T_wb, which scales with q_in,are unobscured by autogenic noise and show enhanced detectability in the power spectra. We emphasize that while signals greater than T_rw do not experience degradation, they can still be obscured by autogenic noise, unless signal period is greater than T_wb. 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.

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.