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Processes and timescales of sediment production, transport, and deposition from source to sink.

The production, transport, and deposition of sediment govern the fluxes and distribution of solid mass on the surface of the Earth. The frequency, magnitude, and physical and chemical properties of these fluxes are initially controlled by external forcing (climate and tectonics) before being modulated by the complex interplay of surface processes. Understanding the interplay of these processes and how they are affected by external forcing is vital to understanding how sediment fluxes have changed through time.
A growing body of studies continues to develop a process-based understanding of the coupling between climate, tectonics, and the production and transport of solids across catchments. Important insights into sediment recycling and residence time have been provided by recent advances in geochemical and geophysical techniques, highlighting the dynamic nature of sediment transport. However, many challenges remain including; (1) fully quantifying the temporal- and spatial scales of sediment transport, (2) assessing the importance of large and infrequent events in controlling erosion and sediment transport and, (3) bridging the gap between short- and long-term or small- and large-scale records of sediment production and fluxes.
In this session we welcome field-based, experimental, and modelling studies, that (1) constrain mechanisms, rates, and scales of erosion, transport, and deposition processes, (2) analyse the influence of internal and external forcing on these processes, (3) investigate the propagation of geochemical or physical signals across the earth surface (such as changes in sedimentary fluxes, grain size distributions, cosmogenic nuclide concentrations).
Contributions across all temporal and spatial scales are welcome.

Invited presentation : Sebastien Carretier - Delayed sedimentary grains

Co-organized by SSP3
Convener: Oliver FrancisECSECS | Co-conveners: Aaron BufeECSECS, Lisa HarrisonECSECS, Stefanie TofeldeECSECS
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Tue, 27 Apr, 11:00–12:30

Chairpersons: Oliver Francis, Lisa Harrison, Aaron Bufe

Simon M. Mudd et al.

The shape of soil-mantled hillslopes is typically attributed to erosion rate and the transport efficiency of the various processes that contribute to soil creep. While climate is generally hypothesized to have an important influence on soil creep rates, a lack of uniformity in the measurement of transport efficiency has been an obstacle to evaluating the controls on this important landscape parameter. We addressed this problem by compiling a data set in which the transport efficiency has been calculated using a single method, the analysis of hilltop curvatures using 1-m LiDAR data, and the erosion rates have also been determined via a single method, in-situ  ­cosmogenic 10Be concentrations. Moreover, to control for lithology, we chose sites that are only underlain by resistant bedrock. The sites span a range of erosion rates (6 – 1373 mm/kyr), annual precipitation (31 – 320 cm/yr), and aridity index (0.08 – 1.38). Surprisingly, we find that hilltop curvature varies with the square root of erosion rate, whereas previous studies predict a linear relationship. In addition, we find that the inferred transport coefficient also varies with the square root of erosion rate but is insensitive to climate. We explore various mechanisms that might link the transport coefficient to the erosion rate and conclude that present theory regarding soil-mantled hillslopes is unable to explain our results and is, therefore, incomplete. Finally, we tentatively suggest that bedrock processes may be responsible for the shape of hillslope profiles at our sites.

How to cite: Mudd, S. M., Gabet, E. J., Wood, R. W., Grieve, S. W. D., Binnie, S. A., and Dunai, T. J.: Rapidly eroding hilltops are surprisingly smooth: ridgetop curvature varies with the square root of erosion rate , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12536, https://doi.org/10.5194/egusphere-egu21-12536, 2021.

Jerome Curoy et al.

In Thailand landslides and flooding are two major natural disasters affecting more than 11 million people living in coastal provinces. Such events have significant human and economic impacts. For example, in 1988, landslides resulted in 373 deaths and caused up to US$80 million in damage (Tanavud, 2008); in 2011, floods and landslides affected more than two million people and killed 53 across Southern Thailand with a village of about 100 households being buried by one large slide (EarthObservatory, 2021). Landslides in the Krabi province in Thailand are predominantly shallow and rainfall-induced, they also represent the main source of sediment pulses for coastal environments such as mangroves and beaches. This study aims at investigating the link between sediment availability from 3 river catchments in the province of Krabi in Southern Thailand and sedimentation rate evolution in mangroves directly downstream in order to understand coastal the sediment shortages and therefore coastal erosion in that area.

Landslide inventories were evaluated using high resolution imagery (<10m) such as aerial photographs, Theos and EO-1 satellite imagery, Google Earth historical tool covering a time period from 2007 to present. Calculations of the surface areas and volumes of landslides was calculated in ArcMap using the formulae developed by Larsen et al. (2010). Landslide erosion was modelled using an approach based upon the negative power law scaling properties of rockfall magnitude–frequency distribution to establish total volumes of sediment for specific years or seasons.

Core samples taken in the mangroves near the river mouths were used to identify markers of landslide events and associated sediment cascades based on grain size distribution and 137Cs dating.

Preliminary results show sedimentation rates in the mangroves from 0.9 to 2 mm/year since 1963 and sediment volumes made available to transport from 0.3 to 68300 m3/year since 2007 across the 3 catchments.

Grain size analysis shows variations of the D50 and the sorting coefficient throughout the sediment recording indicators of landslides and high intensity rainfall events.

How to cite: Curoy, J., Ward, R., and Barlow, J.: From the Landslide to the Mangrove; Coupling Sediment Supply Pulses and River Sediment Deposits in the context of Climate Change in Thailand., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-839, https://doi.org/10.5194/egusphere-egu21-839, 2021.

Erin L. Harvey et al.

Large, catchment transitioning debris flows are an important mechanism for transporting sediment from hillslopes into higher order channels. Extremely large flows can exceed volumes of 109 m3, however even flows with volumes of  ~103 m3 can lead to fatalities and extensive damage. Few processes transport a wider range of grain sizes than debris flows, which can transport grains from clays to 10 m boulders. While the structure of debris flows can often be inferred by their deposits, the range of grain sizes presents a challenge for their interpretation. Debris flow grain size distributions can be used to constrain debris flow runout due to their effect on excess pore pressure dissipation. Currently, there is limited data available for the entire grain size distribution of debris flow deposits in the field.

We constrained the entire grain size distribution for two extremely large (>1 km in length) post-earthquake debris flows in Sichuan Province, China. These debris flows were triggered in August 2019 after an extreme rainfall event occurred close to the epicentre of the 2008 Wenchuan earthquake. We sampled the debris flows in November 2019 at intervals of 200 m and 500 m, respectively. At each site, we used a combination of field and laboratory sieving to obtain the coarse and fine fraction for both the surface and subsurface. We dug 1 m x 1 m x 0.5 m pits, excavating each layer at 10 cm depth increments. We sieved these increments into five size fractions in the field, including < 1 cm. We sieved 1 kg of the <1 cm fraction in the laboratory to estimate the distribution of the finest grains. The coarse surface fraction was then independently constrained using photogrammetry. Preliminary results for one debris flow show that the distribution of fine grains (~<4 mm) is consistent both laterally and vertically across the runout. This suggests that the processes occurring vertically and laterally during deposition result in the consistent distribution of fines.

How to cite: Harvey, E. L., Hales, T. C., Hobley, D. E. J., Fan, X., Liu, J., Xu, Q., and Huang, R.: Downstream evolution of grain size in extremely mobile post-earthquake debris flows, China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7389, https://doi.org/10.5194/egusphere-egu21-7389, 2021.

Lena Katharina Schmidt et al.

High alpine areas are affected disproportionately by global warming and are thus found to be in a transient state. This causes accelerating glacial retreat, which can have severe impacts on discharge and potentially sediment dynamics. Possible effects include changes in water quantities and hydrograph timing as well as changing sediment source areas and the associated magnitude and timing of transport capacities. In turn, the resulting changes in water and sediment supplies and timing have the potential to severely impact downstream ecosystems and infrastructure.

An essential step towards estimating the effects of future changes and developing sustainable management strategies is to quantify the behavior in the past and present. We therefore used the excellent data availability of discharge and suspended sediment concentrations in our study area in the upper Ötztal in Tyrol, Austria, to make such an assessment. We study discharge and suspended sediment concentrations, which have been monitored at three gauges and for a minimum of seven years in the case of the youngest gauge. The resulting nested catchment setup, with catchment sizes ranging between 98 km² and 785 km², allows us to learn about discharge and sediment fluxes and their spatial distribution, thus allowing us to quantify the relative importance of the glaciated areas as compared to the lower-lying catchment areas. It also allows us to study the temporal dynamics, such as the seasonal timing of the peaks and their interannual differences. In turn, the nested catchments allows us to investigate the spatial variability of these temporal dynamics.  

The results confirm the high specific sediment yields for alpine catchments in the order of 10³ t/km² per year and higher yields in areas with higher glacier cover as well as a very pronounced seasonality.

How to cite: Schmidt, L. K., Francke, T., Blume, T., Schöber, J., Pfurtscheller, D., Achleitner, S., and Bronstert, A.: Suspended sediment and discharge dynamics across multiple spatial and temporal scales in a glaciated alpine environment: the case of the upper Ötztal, Austria, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9575, https://doi.org/10.5194/egusphere-egu21-9575, 2021.

Jan Henrik Blöthe and Thomas Hoffmann

Sediment yield from lowland rivers around the globe is often dominated by suspended sediment that also acts as a carrier for pollutants and contaminants. Achieving a deeper understanding of the suspended sediment dynamics is important for river management, but often complicated by short or discontinuous time-series and scattered surveying locations. However, suspended sediment transport is highly variable in space and time, calling for decadal observations that reflect this variability. Here we make use of >130,000 measurements on water discharge (Q) and suspended sediment concentration (SSC) from twelve stations that drain large parts of the central German uplands, to investigate the spatiotemporal variability in suspended sediment flux. 
The data has been collected during working days between 1965 and 2018 in context of the suspended sediment monitoring conducted by the Federal Waterways and Shipping Administration (WSV). The contributing catchments of the twelve monitoring stations range between 2500 and 22000 km2 and cover observation periods between 27 and 53 years. 
Despite roughly similar topographic and climatic conditions, average specific (suspended) sediment yield (SSY) varies between ~6 and ~29 t km2 yr-1. Highest specific yields are observed for those catchments that drain the escarpment of the Swabian cuesta landscape. Even more pronounced than the spatial variability is the interannual variability in sediment yield, with SSY for very wet years exceeding SSY for dry years more than tenfold. Separating the hydrograph into base-flow and event-flow components, we find that sediment export during event-flows accounts for 60 to 85% of the long-term SSY, with individual floods accounting for more than 90% of the annual sediment export. We conclude that high specific (suspended) sediment yields in the central German uplands are conditioned by rapidly responding catchments (i.e. large fraction of event-flow contribution) with highly erodible lithologies of the Swabian cuesta landscapes.

How to cite: Blöthe, J. H. and Hoffmann, T.: Few floods govern decades of suspended sediment flux in German upland rivers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12056, https://doi.org/10.5194/egusphere-egu21-12056, 2021.

Brahim Hichem Belbal et al.

The middle Loire riverbed, after its confluence with Allier, is characterised by a morphology of alternate bars more or less vegetated and possesses riverbank flood protections. The suspended particulate matter (SPM) fluxes are therefore originated from these two catchment areas that drain the eastern and southern parts of the Massif Central. The temporal dynamics of the SPM fluxes are very variable, both on an interannual scale and on the scale of a flood event. Furthermore, SPM fluxes also present high spatial heterogeneities as they are governed by complex processes of production (erosion) and transfer (storage/remobilisation). The Loire river plays an important role in supporting the French energy production by providing cooling water to several Nuclear Power Plants (NPP). However, the cooling systems of the NPPs on the middle Loire are exposed to the risk of silting. In order to ensure a safe management of water intakes and prevent the industrial risks arising from sediment transport, it is therefore imperative to understand the spatio-temporal dynamic of sediment production and transfer.

In this context, the objective of this thesis work is to provide keys to improve sediment management of the river between the two NPPs of Belleville and Dampierre. In a first place, the river flow and SPM data available at the upstream NPP of Belleville will be analysed in order to understand the temporal variations of the incoming SPM fluxes. In a second phase, a soil erosion and hydrological model will be implemented to understand the production processes in the upstream catchments. This second part will allow to determine the interactions of the SPM inputs in the river with the morphodynamics of the bed of the Loire between the two stations. We will present the methodology that has been designed to apprehend these two phases and the first results of the river SPM temporal dynamic at the Belleville NPP station.

How to cite: Belbal, B. H., Goutal, N., Antoine, G., and Cerdan, O.: Temporal and spatial dynamic of suspended sediments fluxes and sources and morphological evolution of the bed in the middle Loire river, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15401, https://doi.org/10.5194/egusphere-egu21-15401, 2021.

Noelia Garijo et al.

Temporal fluctuations of suspended sediment fluxes are highly related with the flow and sediment regime of river networks. Flow dynamics are mainly triggered by climatic forces. Conversely, sediment regime is majorly controlled by land cover/land use changes and by human infrastructures (e.g. dams). Resulting sediment fluxes thus show a non-linear and non-stationary nature.  The wavelet transformation technique emerges as a skilful tool capable of dealing with this type of data. It allows to distinguish within the full spectrum of time-scales, those which are dominant and thus govern the overall trend of the time-series. Furthermore, the temporal multiresolution wavelet technique allows to accurately denoise the discharge and SSC time-series, filtering out the high frequency intermittent physical processes which are superimposed on the main signal. In this research, we analyse a long-term dataset of discharge and sediment fluxes time-series for the Upper Changjiang (Yangtze River, China).

How to cite: Garijo, N., Juez, C., Hassan, M., and Nadal-Romero, E.: Long-term temporal structure analysis of sediment fluxes in the Upper Changjiang (Yangtze River) using a wavelet transformation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12666, https://doi.org/10.5194/egusphere-egu21-12666, 2021.

Sebastien Carretier et al.

River sediment grains are transported and stored episodically in different reservoirs (terraces, alluvial fans, foreland basin, etc.). The residence time of sediment grains in each reservoir has important implications for the paleo-environmental interpretation established from these grains, and their stratigraphic record, as well as for soil contamination, when these grains come from contaminated sources. The recycling of old sediments, via erosion of an old reservoir (e.g. foreland basin erosion), is a known problem. What is less well recognised is that the recycling of a minority of very old grains can strongly bias the average residence time of a grain population deposited in a stratum. In this case, the time-dependent paleo-environmental properties of a population of grains, such as the degree of weathering, or the concentration of cosmogenic isotopes, can then be biased. Several lines of evidence for this phenomenon, inherent to fluvial transport processes, have emerged, though reconstructing the residence time distribution of a grain population over long times (>>ka) remains a challenge. Using a landscape evolution model coupled with grain transport, we show that at the scale of a piedmont, grains can remain several hundred ka before being evacuated. At the scale of a river in Northern Chile, we used the concentration of 10Be in individual pebbles to show that some pebbles remain stored for several tens of ka before being evacuated to the river outlet. In addition, the distribution of residence times can also provide information on the nature of the diffusive processes that control the fluxes of exported sediment. These results suggest that the characterisation of grain-by-grain properties in a grain population can not only help to avoid possible interpretation biases but also provide constraints for models of long-term fluvial sediment outfluxes.  

How to cite: Carretier, S., Guerit, L., Harries, R., Regard, V., Maffre, P., Bonnet, S., Choy, S., and Farías, M.: Delayed sedimentary grains, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5200, https://doi.org/10.5194/egusphere-egu21-5200, 2021.

James Pizzuto

As sediment is carried through watersheds, it may be stored in floodplains and other alluvial deposits, remaining in place for hundreds to millions of years before being remobilized and transported farther downstream.  Sediment routing models based on reservoir theory can account for time-varying sediment storage and predict lags in sediment delivery imposed by sediment storage, but observational data are needed to construct and validate these models.  Because of the long timescales involved, direct observations are rarely useful, but stratigraphic observations coupled with sediment dating techniques can be used to quantify the amount of sediment stored through time and its associated age and storage (or transit) time distributions. To illustrate this approach, a meta-analysis of published geologic data is used to quantify river corridor storage through time associated with European colonization of the mid-Atlantic U.S.  The history of floodplain growth from Holocene to the present is summarized by empirical distributions extracted from stratigraphic data; distributions were sampled to create thousands of synthetic age-depth curves.  Deposits predating European colonization range in age from >18,000 yrs. to 225 yrs. B.P. and with a median thickness of 40% of the total accumulation; sedimentation rates for these deposits are low (median = 0.06 cm/yr).  The median thickness of sediments deposited between 1750 and 1900 (“legacy sediments”) comprises 36% of the total; the median accumulation rate of legacy sediments is 0.32 cm/yr.  The median thickness of sediments deposited after 1950 represents 11% of total accumulation, and the median contemporary sedimentation rate of 0.26 cm/yr is statistically indistinguishable from that of legacy sediments.  Synthetic vertical sequences can be recast as age distributions, and when combined with geomorphic mapping and assessment of patterns of erosion through time, as storage time distributions as well.  Age and storage time distributions at 1000 yrs. B.P., in 1900 A.D., and at present are highly variable, and could be represented by many different mathematical functions, though averaged data appear to be heavy-tailed.   Records of mass accumulation through time and the present and past age and storage time distributions provide useful summaries of the history of sediment storage, and can be used to calibrate and verify watershed scale sediment routing models over millennial timescales.

How to cite: Pizzuto, J.: Quantitative Sediment Storage Chronology Associated with European Colonization of the Mid-Atlantic U.S. and its Application to Watershed Scale Sediment Routing, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5834, https://doi.org/10.5194/egusphere-egu21-5834, 2021.

Benjamin Purinton and Bodo Bookhagen

Grain-size data are imperative for understanding erosional and fining processes in steep terrain as rivers are the primary conduits for sediment transport. However, collecting hundreds of pebble measurements at multiple channel bed survey sites in steep and dynamic high-mountain river settings remains a challenging roadblock in studying downstream variations in grain-size. Using PebbleCounts (https://github.com/UP-RS-ESP/PebbleCounts), we survey large (~1,000+ m2) channel cross sections and measure thousands of grains per survey to build robust grain-size distributions in the Quebrada del Toro, Northwest Argentina. Because of imagery resolution considerations, we only examine the grain sizes in the ≥ 2.5 cm fraction of the distribution. We gather measurements via a careful counting and validation process to constrain uncertainties, which highlights the dominant over- and under-segmentation errors that occur in PebbleCounts in this challenging geographic setting. Despite uncertainties, we are able to study downstream changes in grain-size percentiles at seven survey sites along a 100-km stretch of the trunk stream, which traverses a steep topographic and environmental gradient. We find that only the upper-most percentiles (≥ 95th) are sensitive, whereas the 50th and 84th percentiles show little downstream variability in this rapidly eroding catchment. In particular, we note a strong relation between increases in these upper percentiles and the along-channel junctions with large, oversteepened tributaries, where extreme channel steepness reaches are > 200 m0.8 (θ=0.4). Furthermore, independent spaceborne synthetic aperture radar (SAR) coherence and amplitude observations show clear relations to mass transfer and channel bed roughness changes, which also relate to the grain-size variability that we find.

How to cite: Purinton, B. and Bookhagen, B.: Downstream grain-size changes using PebbleCounts in the south-central Andes: Relations to channel steepness and SAR observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1703, https://doi.org/10.5194/egusphere-egu21-1703, 2021.

Jose Silvestre et al.

Many deltas contain extensive marshes, typically defined as laterally extensive, low energy settings tied to a narrow elevation window around sea level. Biological activity in marshes results in in-situ organic sediment accumulation that has the potential to be stored in the sedimentary record. However, it is unclear how marshes interact with channels that transport the clastic sediment and typically control autogenic stratigraphic architecture. We present results from a physical experiment designed to explore the coupled evolution of marshes and deltas over geologic timescales. In the experiment, deltaic channels self-organized due to constant input rates of water and clastic sediment that experience constant long-term accommodation production through sea-level rise. A low bulk density kaolinite clay was deposited on the delta-top following rules developed by the ecology community for in-situ organic production. The kaolinite clay serves as a proxy for the in-situ organic sediments in overbank regions. As such, the autogenic processes of the clastic transport system, which influence elevation relative to sea-level, also exert a control on the scales of preserved organic-rich strata. We quantify the fraction of the organic sediment proxy in the fluvio-deltaic deposit to define a transfer function between the accumulation of organic sediment and its preservation beneath the morphodynamically active layer. We also use synthetic stratigraphy and images of the preserved strata to characterize the spatial arrangements of organic strata, and the influence of marshes on the resulting arrangement of channel bodies. Initial findings suggest that the thickest seams are located near the mean shoreline but extend significant distances from this location due to autogenic shoreline transgressions and regressions. Quantifying these trends will inform our understanding of how in-situ organic sediment accumulation influences clastic transport systems and the structure of deltaic stratigraphy.

How to cite: Silvestre, J., Sanks, K., Zapp, S., Ripul, D., Shaw, J., and Straub, K.: Exploring the relationship between organic deposition resulting from marshes and autogenic scales in deltaic stratigraphy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12844, https://doi.org/10.5194/egusphere-egu21-12844, 2021.

Lucas Albanese Valore et al.

The source-to-sink approach to sedimentology has become an increasingly valuable approach for addressing how external and internal forcing mechanisms are tied together in time and space. Processes that are initiated deep within the lower mantle can eventually propagate and affect shallow crustal sedimentary systems. This is important to predict the presence of reservoirs in areas of little data, and to interpret the sedimentary record in terms of climate and tectonic settings during deposition. To address this issue, we will study the Early Palaeogene succession of the East Shetland Platform in the North Sea, which was deposited during the emplacement of the Icelandic Plume. The plume’s activity is hypothesized to be the cause of a major uplift cycle in the continental source areas, which is coeval to a sharp increase in sedimentation rates recorded in the East Shetland Platform during the Palaeocene. However, this relationship is still in need of accurate constraints derived from data with better spatial and temporal resolution, particularly due to overlapping climatic and tectonic controls, regional-to-local variations in sediment supply systems and overall gaps in the sedimentary record. This correlation can benefit from high-quality 3D seismic data on the platform, especially due to an exceptional preservation of shelf-edge geometries that are absent elsewhere. Using different 3D and 2D seismic surveys, well data and biostratigraphic data from the Shetland Platform and the North Sea, we will quantify sediment volumes supplied through time. The observed sediment volumes will be investigated using models of dynamic topography, plume activity and paleoclimatic data to closely relate supplied volumes to changes in relief, catchment geometries, precipitation and other key forcing parameters. Ultimately, we aim to investigate the relative influence of both tectonics and climate, as both long term (mantle dynamics) and short term (Palaeocene-Eocene Thermal Maximum) have been interpreted to play an important role in this system.


How to cite: Albanese Valore, L., Haug Eide, C., and Oftedal Sømme, T.: Tectonic influence of Large Igneous Provinces on source-to-sink systems, the case study of Shetland during the Palaeocene - Preliminary results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13122, https://doi.org/10.5194/egusphere-egu21-13122, 2021.

Si Chen et al.

This study discusses the sedimentary flux, and sedimentary system source tracking on the shelf margins of Yinggehai (YGH) and Qiongdongnan (QDN) Basins, Northern South China Sea. The shelf margin clinoforms of YGH and QDN Basins, have grown since the Late Cenozoic (10.5 Ma), which generated more than 4 km-thick shelf prism above the T40 surface. By using the core, well drilling data, 2D and 3D seismic surveys, this study aims to: ① demonstrate the geometry morphology and architecture of the clinoforms, while the shelf margin trajectory (including the shelf-edge trajectory and toe of slope trajectory) showing down-flatting and rising patterns where the progradation and aggradation happened through the vertical evolution; ② estimate sediment supply values, load volumes, and their changes since the Late Cenozoic, predict ratio of the sediment flux across shelf-edge during their dynamic processes; ③ investigate the contradiction and correlation among the phenomena that sediments show distinctly increasing in flux, decreasing in grain size, and response delay of flux rate peak since 2-4 Ma. The preliminary results show that the vertical sediment accumulation rate increased significantly across the entire YGH and QDN Basin margin system after 2.4 Ma, with a marked increase in mud content that likely caused by long‐distance, alongshore currents with high content of mud during the Pleistocene. Furthermore, laterally, the estimated total sediment flux onto the margin shows a dramatic decline from west to east while moving away from the Red River depocenter, as well as a decrease in the percentage of total discharge crossing the shelf break in this same direction. The overall margin geometry shows a remarkable change from sigmoidal, strongly progradational and aggradational in the west to weakly progradational in the east of QDN Basin margin. The Late Cenozoic shelf margin growth, with its overall increased sediment flux, responded to global, high‐frequency transgressive‐regressive climate cycles during a falling global sea level and gradual cooling temperature in this icehouse period.

How to cite: Chen, S., Wang, H., Ma, J., Gong, T., and Yu, Z.: Clinoform growth and sediment flux of Late Cenozoic Yinggehai and Qiongdongnan shelf margins, Northern South China Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12221, https://doi.org/10.5194/egusphere-egu21-12221, 2021.

Aurora Machado Garcia et al.

Trough mouth fans are large depocentres forming the ultimate sinks in glacial source-to-sink systems. Their architecture, sedimentological aspects (origin and processes) and their role as paleoclimatic archives are essential components in improving our understanding of Pleistocene and ongoing climate changes. For many years, these depocentres were thought to be dominated by debris flows accumulated in front of ice streams located at the shelf break. However, recent studies have shown that meltwater plays a major role in bringing sediment to the most distal parts of these fans, especially in lower latitudes. The North Sea Trough Mouth Fan encompasses ~110,000 km2 with water depths of up to 3500 m. It has received sediments throughout the Quaternary, with increased sedimentation rates in the last 1.1 Ma when the Norwegian Channel Ice Stream was active. Recent insight of the fan shows that meltwater turbidites play a major role in sediment delivery to the continental slope and deep-sea basin. The results could entail distinct morphologies for mid-latitude and high-latitude fans. As a result of glacial erosion and the absence of clear imprints of ice sheets on the paleo-shelves, studying trough mouth fan deposits becomes paramount in understanding glacial-interglacial cycles. This project will assess the source-to-sink parameters of the last glaciation (Weichselian) at the North Sea Fan, elucidating the dominant marine and terrestrial processes that led to the studied sedimentary sequences. High-resolution 2D and 3D seismic data, core, volumetric and numerical modeling data will be assimilated to establish a source-to-sink model for the target interval. These results will contribute to the knowledge of how glaciations affect surface mass redistribution, directly affecting the landscape dynamics and sediment routing from Fennoscandia via the North Sea to the slopes and deep basin. Sediment production will be evaluated, assessing whether it increases during the glaciation or if observed higher sedimentation rates are a result of enhanced sediment transport. This project is a part of the Marie Sklodowska-Curie Innovative Training Networks “S2S – Future: Signal propagation in source to sink for the future of the Earth resources and energy” and will further advance how trough mouth flans are highly dynamic areas where sediment transport, dispersal, remobilization and deposition take place, and serve as excellent proxies to the dynamics of glacial pulses in the hinterland.

How to cite: Machado Garcia, A., Midtkandal, I., Bellwald, B., and Anell, I. M.: A Source to Sink Approach to the North Sea Fan Pleistocene Glacial Sediments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12600, https://doi.org/10.5194/egusphere-egu21-12600, 2021.

Rohan Bhattacharyya and Satinder Pal Singh

The Great Indian Desert, Thar is a natural source of the atmospheric mineral dust burden over India and nearby landmasses/seas and regulates the regional climate and ecosystem health. However, the limited geochemical/isotope data of Thar sediments from the source region in Rajasthan restrict their source delineation and implication for characterization of the Thar dust signatures. For this purpose, we have measured major, trace, and rare-earth elemental concentrations, and radiogenic Sr and Nd isotope compositions in 51 surface sediment samples collected over a wide area from the Thar Desert, Rajasthan. The geochemical data reveals a low degree of the chemical index of alteration (CIA ~43–54), a quartz dilution of major oxides, and depletion of heavy minerals such as zircons. The UCC normalized spider diagram, as well as La/Yb–Eu anomaly plot, reveal that the Thar surface sediments collected in this study are geochemically similar to that of a sedimentary sequence from the Luni River originating from the Aravalli mountains. The 87Sr/86Sr and εNd of Thar sediments overlap with the reported values for the Indus delta and Luni river sediments but are distinctly different from those of the Ghaggar river sediments. Thus, the sediment contribution from the Indus delta cannot be completely ruled out, while the Ghaggar sediment contributions are minimum. Furthermore, the radiogenic isotope compositions of the decarbonated Thar sediments are strikingly contrasting to the reported values for silicate fractions of eolian deposits in northwestern India. These differences could be due to grain size effects during the dust production/transport or local sediment contributions to the eolian deposits.

How to cite: Bhattacharyya, R. and Singh, S. P.: Geochemical/isotope characterization of sediments from the Great Indian Desert, Thar, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12391, https://doi.org/10.5194/egusphere-egu21-12391, 2021.

Guido Pastore et al.

The Sahara is by far the largest hot desert on Earth. Its composite structure includes large dune fields hosted in sedimentary basins separated by elevated areas exposing the roots of Precambrian orogens or created by recent intraplate volcanism. Such an heterogeneity of landscapes and geological formations is contrasted by a remarkably homogeneous composition of dune sand, consisting almost everywhere of quartz and durable minerals such as zircon, tourmaline, and rutile.

We here present the first comprehensive provenance study of the Sahara Desert using a combination of multiple provenance proxies such as bulk-petrography, heavy-mineral, and detrital-zircon U–Pb geochronology. A set of statistical tools including Multidimensional Scaling, Correspondence Analysis, Individual Difference Scaling, and General Procrustes Analysis was applied to discriminate among sample groups with the purpose to reveal meaningful compositional patterns and infer sediment transport pathways on a geological scale.

Saharan dune fields are, with a few local exceptions, composed of pure quartz with very poor heavy-mineral suites dominated by durable zircon, tourmaline, and rutile. Some more feldspars, amphibole, epidote, garnet, or staurolite occur closer to basement exposures, and carbonate grains, clinopyroxene and olivine near a basaltic field in Libya. Relatively varied compositions also characterize sand along the Nile Valley and the southern front of the Anti-Atlas fold belt in Morocco. Otherwise, from the Sahel to the Mediterranean Sea and from the Nile River to the Atlantic Ocean, sand consists nearly exclusively of quartz and durable minerals. These have been concentrated through multiple cycles of erosion, deposition, and diagenesis during the long period of relative tectonic quiescence that followed the Neoproterozoic Pan-African orogeny, the last episode of major crustal growth in the region. The principal ultimate source of recycled sand is held to be represented by the thick blanket of quartz-rich sandstones that were deposited in the Cambro-Ordovician from the newly formed Arabian-Nubian Shield in the east to Mauritania in the west.

The composition and homogeneity of Saharan dune sand reflects similar generative processes and source rocks, and extensive recycling repeated through geological time after the end of the Neoproterozoic, which zircon-age spectra indicate as the last major event of crustal growth in the region. The geographic zircon-age distribution in daughter sands thus chiefly reflects the zircon-age distribution in parent sandstones, and hence sediment dispersal systems existing at those times rather than present wind patterns. This leads to the coclusion that, provenance studies based on detrital-zircon ages, the assumption that observed age patterns reflect transport pathways existing at the time of deposition rather than inheritance from even multiple and remote landscapes of the past thus needs to be carefully investigated and convincingly demonstrated rather than implicitly assumed.

How to cite: Pastore, G., Baird, T., Vermeesch, P., Resentini, A., and Garzanti, E.: Recycling of Sahara desert sand, a comprehensive provenance study approach., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1095, https://doi.org/10.5194/egusphere-egu21-1095, 2021.

Alexandre Ortiz et al.

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 for oil and gas exploration and storage.

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 the framework of this new cartography, we propose to compile the available and newly acquired data from the S2S project (TOTAL, BRGM), over the entire peri-Pyrenean domain. We produced large scale quantitative and qualitative maps and wheeler diagrams to better observe and interpret the tectonic, climatic and surface processes impacts of the SRS behavior.

The 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 structural accidents 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-orogenic, syn-orogenic 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 discuss the 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: Ortiz, A., Fillon, C., Lasseur, E., Briais, J., Guillocheau, F., Bessin, P., Baby, G., Baptiste, J., Uzel, J., Robin, C., Calassou, S., Catelltort, S., and Frasca, G.: A new way to predict sediment production and deposition: integrated Source to Sink maps at pluri-basins-scale, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12133, https://doi.org/10.5194/egusphere-egu21-12133, 2021.

Benjamin Amann et al.

Fjord sediments are increasingly recognized as high-resolution recorders of past climate and hydrological variability. Using them as such, however, requires a comprehensive understanding of the variables that affect their properties and accumulation rates. Here, we conduct a spatial and temporal study of sediment samples collected at the head of Martínez Channel (Chilean Patagonia, 48°S), to understand how the fjord’s sediments register changes in the hydrodynamics of Baker River, Chile's largest river in terms of mean annual discharge. We apply end-member modeling to particle-size distributions of: (i) river suspended sediments, (ii) surface sediments collected along a proximal-distal transect at the fjord head, and (iii) fjord sediments collected in a sequential sediment trap at 15-day resolution during two consecutive years. Results show that the river suspended sediments and fjord sediments are consistently composed of two grain-size subpopulations. The finest end member (EM1; mode 4.03 μm) reflects the meltwater contribution, which dominates in all but the winter season. The coarser end member (EM2; mode 18.7 μm) dominates in winter, when the meltwater contribution is reduced, and is associated to rainfall events. We propose that log(EM1/EM2) can be used to reconstruct temperature in the lower Baker River watershed (r = 0.81, p < 0.001). We also show that the fluxes of EM1 and EM2 provide quantitative estimates of baseflow (r = 0.82, p < 0.001) and quickflow (r = 0.90, p < 0.001), respectively. These results support the use of fjord sediments for quantitative reconstructions of climate and hydrological changes in glacierized watersheds.

How to cite: Amann, B., Bertrand, S., Alvarez Garreton, C., and Reid, B.: Seasonal variations in the origin of river sediments (Baker River, Chile): A pre-requisite for climate and hydrological reconstructions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2430, https://doi.org/10.5194/egusphere-egu21-2430, 2021.

Melanie Kling et al.

The emplacement of the Siberian Traps Large Igneous Province around the Permian–Triassic boundary significantly affected both climate and depositional environments across the world. Known long term consequences of this event are (I) global warming, (II) increased continental weathering, (III) oceanic stagnation and acidification and (IV) mass extinction. These effects have the potential to strongly alter signals from source-to-sink systems in terms of petrography, sediment volumes and geochemistry. The Barents Sea Basin is an excellent area to investigate the response of source-to-sink systems to such climatic changes because it contains a continuous record of sediments deposited before, during and after the Permian-Triassic event, and because this interval is sampled in several exploration wells.

The goal of this project is to investigate how the Triassic climatic changes were expressed in source-to-sink systems, mainly using techniques such as facies analysis, petrograpy, mudstone geochemistry and sediment volumes. Herein we present preliminary results mainly from sandstone petrology. On the Finnmark Plattform, the upper Permian strata of the Røye Formation contains spiculitic mudstones and limestones with sparse sandstones. These are overlain by mudstones, interbedded turbidites and prograding deltas of the Lower Triassic. In order to determine how the signal from the catchment changed to the great climatic changes, it is of high importance to examine changes within provenance and sediment volumes across the P-T boundary.

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How to cite: Kling, M., Sirevaag, H., Pucéat, E., and Eide, C. H.: Impact of climatic step-changes on source-to-sink systems: Petrographic changes across the Permian-Triassic changes on the Finnmark Platform, Barents Sea, N Norway, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9296, https://doi.org/10.5194/egusphere-egu21-9296, 2021.

Bodo Bookhagen et al.

The intensity of the Asian summer-monsoon circulation varies over decadal to millennial timescales and impacts surface processes, terrestrial environments, and marine sediment records. The duration and magnitude of this climatic forcing on erosion processes varies, depending on duration and intensity of the climatic events, as well as on the tectonic and geomorphologic preconditioning of the landscape. In this study, we focus on a region in the transition zone between continuous and episodic monsoon impacts: the Spiti River, the largest tributary (12x103 km2 ) to the Sutlej River in the western Himalaya. The river valley is located in the northern lee of the Himalayan orographic barrier in a presently arid environment. The Spiti Valley has received significant precipitation during intensified monsoon periods during the late Pleistocene and Holocene and thus constitutes an ideal location to evaluate effects of episodic moisture transport into an arid, high-relief mountainous region.

Here we present 21 new surface-exposure ages of fluvial-fill terraces combined with previously published data to quantify temporal patterns in river incision and erosion rates. Our data include catchment-wide erosion rates and in-situ cosmogenic nuclide ages derived from 10Be, 26Al, and 21Ne and document that terrace formation (i.e., terrace abandonment) occurred during intensified monsoon phases at ∼100 ka, ∼65 ka, ∼43 ka, and ∼12 ka, although dating uncertainties prevent the calculation of exact correlation between monsoonal strength and terrace formation. We show that incision into Late Pleistocene valley fills that integrate over several cut-and-fill cycles at 105 y are comparable to exhumation rates determined from thermochronology studies averaging over 10^6 y in that area. We argue that the limiting factor for sediment removal and river incision on shorter, millennial timescales is due to large bedrock landslides that impounded the river network and formed transient sedimentary basins lasting for 103 -104 years. We suggest a feedback process between sediment removal and landsliding, where large landsliding predominantly occurs when the transiently-stored valley fills have been carved out, leading to exposed valley bottoms, bedrock erosion, lateral scouring of rivers, and ultimately to the over-steepening of hillslopes. We suggest that Late Quaternary climatic variability is the main forcing factor in filling and evacuating transiently stored sediments in high mountain ranges and thus plays a direct role in controlling bedrock incision.

How to cite: Bookhagen, B., Strecker, M., Niedermann, S., and Thiede, R.: Late Quaternary Climate Variability Constrains River Incision and Aggradation in the Spiti Valley, Western Himalaya, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15369, https://doi.org/10.5194/egusphere-egu21-15369, 2021.

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