The source-to-sink system of the Golo River, the largest catchment of Corsica (Western Mediterranean) is a well-established test case for inferring erosion rate variations from the sedimentary record in a quiescent tectonic setting. Previous studies have analyzed the onshore part of the source-to-sink system during late Quaternary climatic and sea level variations, and the offshore sink to highlight the main variations in sediment yield during the late Pleistocene and the last glacial cycle. Here we expand the analysis of the river network of Corsica and of the offshore sink back to the Miocene, when the region was still tectonically active. Based on a unique set of geological and in situ ¹⁰Be cosmogenic data, we show how the landscape have responded and is still responding to the disequilibrium caused by the late Miocene uplift of Alpine Corsica, and we provide evidence of a two-stage river capture event affecting the river network during the Pliocene. Our data reveal that ~1280 km² of basin area originally draining towards the Ligurian Sea was abruptly connected in the Pliocene to the Tyrrhenian Sea through headward erosion. River capture led to the formation of a large Pliocene-Quaternary submarine fan offshore the Tyrrhenian coast, associated to an increased sediment yield that was three times greater than the average sediment yield in the same source-to-sink system during the Holocene. Such a major change in sediment flux towards the Tyrrhenian margin was greater magnitude than any subsequent peaks in sediment yield documented during Pleistocene glaciations. In situ ¹⁰Be cosmogenic data demonstrate that erosion is focused on previous capture sites even today, which indicates persistence of disequilibrium after millions of years. Our findings suggest that using the sedimentary archive to infer tectonic growth of topography or climate changes is not straightforward and may lead to incorrect interpretation unless river piracy can be safely excluded.

How to cite: Malusa', M. G., Resentini, A., and Wittmann, H.: A two-stage river capture event in Corsica and its impact on erosion rates and offshore sedimentation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9855, https://doi.org/10.5194/egusphere-egu24-9855, 2024.

Many deltas worldwide are at the risk of drowning under projected future rates of sea-level rise. Understanding the morphodynamic response of deltas through stages in the Holocene, is crucial to know their current state and determine their future and to take effective action.

To understand the relation of coastal-plain morphology and substrate with history of vegetation cover, sediment supply, tides and salinity gradients, between vegetation cover, sediment supply and coastal morphology we examine the history of the Tagliamento river delta in Northern Italy, a backbarrier coastal system with large lagoonal areas. This river mouth is one of the morphologically intact in Europe, even though it has experienced a long history of human presence. We combine a large dataset of 4,000 core descriptions with detailed proxy-analyses of multiple cores to map accretion surfaces in time and link them to past changes in vegetation, sea level and climate. Lithology, pollen data and C-14 ages provide quantitative information on infill rates and landscape change and human influence. Resulting geologic transects and paleogeographic maps show the 3D infill history of the former lagoon and provide constraints on sediment fluxes and degree of marine ingression. First results from pollen analysis and sedimentology show clear local and region changes in vegetation cover but relatively late and low direct human influence. Further work will attempt to confront the reconstructions with idealized model simulations of sediment budgets and geomorphology at selected moments in time.

How to cite: Gerats, W., Donders, T., van der Vegt, M., Fontana, A., Stouthamer, E., and Cohen, K.: Understanding coastal response to sea level rise in Northern Italy: the Holocene history of the Tagliamento river delta, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9769, https://doi.org/10.5194/egusphere-egu24-9769, 2024.

Submarine canyons serve as important sediment transport conduits from littoral zones to the deep sea, with strong impacts on the sedimentation patterns in marginal areas of the ocean. Here, we present a study of the geological history and the recent activity of the Nahariya submarine canyon, the longest of a system of ~15 small blind canyons located in the eastern Mediterranean Sea, offshore Israel. Two piston cores retrieved from the middle and outlet of the canyon, at 650 m and 915 m water depth, respectively, were the focus of a multi-proxy study aiming to characterize sediment transport and deposition along the canyon during the Last Glacial and up to the present.

Both cores reveal a sequence of homogenous sediment of late last glacial age, which are capped by an unconformity overlying by fine laminated sediment dated to the last ~200 years. Thus, the deglacial and most of the Holocene intervals are absent from the record. Evidence for down canyon sediment transport are abundant and include a 70 cm interval of mud clasts with disordered glacial ages that appears immediately below the hiatus, as well as broken calcareous shells of dead benthic foraminiferal species of shallow marine habitats, which are abundant throughout both cores. Similarly, shelf-derived living benthic foraminiferal species were found in the core-tops, indicating that active sediment transport persists along this canyon today.

We conclude that the history of Nahariya submarine canyon includes a period of sediment accumulation that lasted until the last deglaciation. Thereafter, the canyon was dominated by an erosive regime that persisted throughout the Holocene. Sediment accumulation resumed ~200 years ago. We suggest that the recent resumption of sediment-accumulation is a result of anthropogenic amplification of on-land soil erosion accompanied by a wet period that persisted in the region and enhanced land to sea sediment transport.

How to cite: Katz, O., Moshe, N., Torfstein, A., Kanari, M., Masque, P., and Hyams-Kaphzan, O.: Glacial-Holocene variability in sediment accumulation and erosion along submarine blind canyons: a case study from Eastern Mediterranean Sea , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16308, https://doi.org/10.5194/egusphere-egu24-16308, 2024.

The sedimentary infill of peripheral foreland basins records an intricate relationship between the development of the thrust wedge and related isostatic adjustments, eustasy, and sedimentation processes, posing challenges to the classical source-to-sink concept. The evolution of such basins commences with an “underfilled” flysch stage in the foredeep depozone and passes to a filled and finally an “overfilled” molasse stage in the orogen-proximal zone (Sinclair, 1997). On basin-scale, progressively younger sediments exhibit a regressive character, with the molasse commonly being deposited in alluvial environments.

This study from the North Dalmatian foreland basin in Croatia documents a peculiar gravel association in the alluvial conglomerates of the foreland molasse. These deposits are the youngest unit of the Promina Beds – a calciclastic succession that was deposited in the wedge-top depozone in shallow-marine, marginal marine, and terrestrial environments from the middle Eocene to the late Oligocene (Mrinjek et al., 2012). The alluvial conglomerates were deposited on Oligocene alluvial fans or in proximal braided-river settings (Mrinjek et al., 2012). Besides limestone clasts derived from Cretaceous bedrock, these conglomerates comprise well-rounded calciclastic cobbles and boulders. These clasts are fine-grained calcarenites, whose carbonate content ranges from 61 to 99%. Their macroscopic features resemble sandstones of Eocene flysch that crop out 16 km to the southwest, but samples from these two units show significant differences in microfossil content and heavy mineral associations. Large benthic foraminifera and sporadic planktic forms are found in the Eocene flysch, which was deposited in the prodelta zone of a river-fed delta (Babić & Zupanič, 2008). Contrarily, the calciclastic gravel clasts of the alluvial unit bear more planktic than benthic foraminifera, suggesting original deposition in a deeper and more distal marine environment. The clasts are rich in muscovite (32%), opaque heavy minerals (24%), and biotite (19%), with subordinate transparent heavy minerals (12%). Flysch samples show a coequal abundance of opaque (39%) and transparent heavy minerals (40%). Among the latter, garnet is the most abundant.

These preliminary results suggest that the calciclastic gravel clasts of the alluvial unit most likely derive from a foredeep setting older than the Eocene flysch, that was probably located in the hinterland of the present-day thrust-wedge. The heavy mineral assemblage suggests provenance from metamorphic, igneous, or recycled sedimentary rocks from the Internal Dinarides. Therefore, drastic geomorphic changes must have occurred during the development of the foreland basin, with deep-marine sediments being deposited, subsequently uplifted, eroded, transported, and deposited in continental environments, which will eventually become a new source for a future sink.

CITED REFERENCES:

Babić, Lj., Zupanič, J. 2008. Evolution of a river-fed foreland basin fill: the North Dalmatian flysch revisited (Eocene, Outer Dinarides). Natura Croatica, 17/4, 357–374.

Mrinjek, E., Nemec, W., Pencinger, V., Mikša, G., Vlahović, I., Ćosović, V., Velić, I., Bergant, S., Matičec, D. 2012. The Eocene-Oligocene Promina Beds of the Dinaric Foreland Basin in northern Dalmatia. Journal of Alpine Geology, 55, 409–451.

Sinclair, H.D. 1997. Tectonostratigraphic model for underfilled peripheral foreland basins: An Alpine perspective. GSA Bulletin, 109/3, 324–346.

How to cite: Gobo, K., Lužar-Oberiter, B., Čičak, D., and Mrinjek, E.: Foredeep inclusions into foreland molasse in the North Dalmatian foreland basin, Croatia – from sink to source?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11242, https://doi.org/10.5194/egusphere-egu24-11242, 2024.

Changes in the grain size distribution of river sediment have environmental, ecological and social implications. This study investigated the variation of the grain size of bulk samples, detrital zircons and rutiles from the mainstream and major tributaries of the Yangtze River. The mean size of bulk samples from the upper reaches is significantly higher than the mid-lower reaches. The Equivalent Spherical Diameter (ESD) of most zircons (from previous work) and rutile grains fall within the range of 32-250 μm with dominant size of 63-125 μm. Coarse-sized zircons and rutiles with ESD of 125-250 μm are found in higher proportions in the upper reaches than in the mid-lower reaches, and a significant grain size decrease is observed downstream of the Three Gorges Dam. The significantly decreasing in coarse grains downstream of the dam indicates that the massive sediment contributed by the Three Gorges Dam (TGD), especially coarse-sized sediment. Our study demonstrates that a complex sediment routing system like the Yangtze River is interrupted by the Three Gorges Dam. The problem of grain-size bias caused by human activities on age-data acquisition and interpretation of detrital minerals (rutile and zircon) from large rivers is not negligible and deserves more attention when using single grain geochronology to constrain sediment provenance and tectonic evolution.

How to cite: Guo, R., Sun, X., Li, C., Wegner, W., Zhang, Z., Wei, C., Li, Y., and Klotzli, U.: Grain size distribution of bulk-sample, detrital zircons and rutiles from the Yangtze River: implications for the sediment routing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3451, https://doi.org/10.5194/egusphere-egu24-3451, 2024.

Grain size within the stratigraphic record is often used to interpret changes in tectonics and climate. For example, past work has described the influence of underlying subsidence or flux oscillations due to climate on grain size fining rates within the basin. However, little research has deconstructed the role of internal dynamics in shaping the grain size fining rates preserved within strata under varied basin geometries, precipitation gradients, and bypass states of basin evolution. Through the combination of a landscape evolution model based on the Stream Power Law modified for sedimentation by Yuan et al. (2019) with an extension of the self-similar grain size model of Fedele and Paola (2007) into multiple dimensions (i.e., along dynamically evolving river channels) by Wild et al (in review), we have developed a steady-state framework identifying autogenic vs subsidence dominated grain size fining. When basin accommodation is high relative to incoming flux, or early in the basin evolution, grain size fining is primarily subsidence-dominated regardless of precipitation gradients and basin geometries. Alternatively, under high bypass and low underlying accommodation, grain size fining is autogenically dominated and controlled by relative upstream discharge (or the ratio of the upstream, mountain catchment area vs the downstream, sedimentary system area). Foreland basins (eg: the Alberta foreland basin) with ample downstream area tend to evolve from a high subsidence to autogenic dominated state as they fill over time. Constrained downstream areas (eg: Death Valley fans) display a minimal autogenic impact on grain size fining regardless of their bypass state. We will present our modelled stratigraphic results and compare them to natural systems, such as the Alberta Foreland basin and alluvial fans of Death Valley.

How to cite: Wild, A., Braun, J., Whittaker, A., and Castelltort, S.: Autogenic vs Subsidence Controls on Fluvial Stratigraphic Grain Size Fining through Multi-Channel Landscape Evolution Modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8988, https://doi.org/10.5194/egusphere-egu24-8988, 2024.

Reconstructing source to sink relationships or the origin of sediments and sedimentary rocks is the main goal of sedimentary provenance analysis. Several processes alter the source signal during transport and deposition and the extraction of the initial provenance signal is usually realized by combination of multiple single grain methods determining mineralogy, chemical composition or radiometric ages. However, such methods are mostly applied to sand-sized sediments or sedimentary rocks, while finer grained material is usually analyzed by whole-rock geochemical means and seldom by single-grain methods. Considering the abundance of fine-grained sedimentary archives and that short lived climatic signals are frequently encoded in such archives (e.g. loess, varves, etc.), a strong need for single-grain, multi-method analyses of silt-sized sediments is obvious.

Therefore, we developed a highly automated approach to modal mineralogy of silt-sized sediments and sedimentary rocks based on image segmentation and object detection capabilities of machine learning methods, which allows for correlative analysis (e.g. optical microscopy, Raman spectroscopy, SEM, EPMA, LA-ICP-MS) and increased sample throughput.

To test if our approach is feasible for silt-sized sediments, we sampled three loess-paleosol-sequences (LPS) of similar age and from different loess domains. Based on heavy mineral compositional data and zircon U-Pb age distributions the LPSs can readily be differentiated, verifying the feasibility of our approach. Consequently, we hypothesize that this novel multi-method, high-throughput data acquisition within a highly automated workflow will allow for hitherto unprecedented spatial and temporal resolution as well as statistical significance of provenance information, potentially enabling new research pathways in sedimentary provenance analysis.

How to cite: Lünsdorf, N. K., Lünsdorf, J. O., Újvári, G., Dunkl, I., Wolfram, L., Hobrecht, A., Laake, L., and von Eynatten, H.: From outcrop to spectrum, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17622, https://doi.org/10.5194/egusphere-egu24-17622, 2024.

The modern surface of Mars does not sustain liquid water, however relict landforms observed on orbital images provide strong evidence of past aqueous activity. Nevertheless on-the-ground analysis of sedimentary strata are required to robustly characterise the specific nature of early Mars palaeoenvironments. The Mars 2020 Perseverance rover is exploring a prominent sedimentary fan deposit at the western margin of Jezero crater – the Western fan – which has been interpreted to be an river delta that prograded into an ancient lake basin during the Late Noachian-Early Hesperian epochs on Mars (~3.6-3.8 Ga). Perseverance’s traverse across the fan in 2022-2023 provides a remarkable window into a fossilised sediment routing system on Mars with potential to understand how water and sediment were distributed across a Martian landscape under a markedly different climate to present day. Here we use the rover’s Mastcam-Z cameras to characterise sedimentary geometries in a distal to proximal transect across the western fan and reconstruct sediment dynamics on the Western fan and infer past environmental change. The distal reaches of the preserved fan show a sedimentary succession that records a transition from distal alluvial fan into lacustrine and subsequently foreset delta deposits. This succession records the initiation of a martian lake system and lake level rise, though the delta stratal geometries suggest deposition during episodes of lake level fall. In the medial sector of the upper exhumed portion of the fan, complex stratal geometries are observed with a variety of scenarios for palaeoenvironmental interactions possible. In particular, the presence of large-scale foreset units preserved in this ‘mid-fan’ sector possibly suggests complex deltaic interfingering with fluvial strata during lake level fluctuations. In more proximal and stratigraphically higher (and hence younger) sectors of the fan, we observe strata deposited by progradation of fluvial systems culminating in a sequence of rounded boulder-containing deposits that signal transition to a routing system characterised by high discharges. Misquoting Shakira “the sediments don’t lie”; they record a history of sustained water transport and habitability on early Mars.

How to cite: Gupta, S., Stack Morgan, K., Mangold, N., Ives, E., Gwizd, S., Caravaca, G., Williams, R., Barnes, R., Randazzo, N., Horgan, B., Siebach, K., Tate, C., Núñez, J., Sholes, S., Kah, L., Paar, G., Maki, J., and Bell III, J.: Landscape evolution on early Mars: a look inside a martian fan system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17742, https://doi.org/10.5194/egusphere-egu24-17742, 2024.