Displays

TS9.1

The consideration of entire “Source to Sink" systems is one of the most recent and challenging advance in earth surface dynamics and sedimentary geology. To understand S2S systems it is necessary to promote and enhance sharing of knowledge and concepts between previously separated disciplines that are involved in the analysis of S2S systems. In particular, studying S2S systems implies knowledge and skills from (1) geomorphology, which focuses on the understanding of erosion processes driving landform evolution and sediment fluxes, (2) stratigraphy/sedimentology, which focuses on the nature of sedimentary deposits and their distribution in time and space, and (3) tectonics and structural geology, which set the dimensions, geometry and dynamics of source/transfer areas and sedimentary basins (the sink). Understanding S2S systems also involves other Geosciences disciplines such as paleoclimatology and geochemistry, because they allow quantifying the factors controlling S2S systems dynamics (climatic controls on erosion, solid vs solute fluxes, etc.). The sedimentary record captures Earth’s environmental evolution through interactions with humans. Developing innovative strategies for shaping a sustainable future and responsible growth requires a holistic understanding of Earth’s resources and our impact on the environment that can be informed by the sedimentary archives.
The aim of this general session is to invite contributions from all S2S-related research fields in order to foster connections around a central theme and kickstart the emergence of a European S2S research community. In addition, we propose to use this session to initiate discussion on developing a strategy for S2S training of early-stage researchers to enable them to address the sedimentary system from source to sink and inform them of potential career opportunities in both the academic and non-academic sectors. We welcome all S2S-related and environmental signal propagation contributions, and in particular those addressing 1) perennial S2S dynamics in response to long-term tectonic and climatic signals in deep time, 2) transient S2S dynamics in response to short-term signals and extreme events, 3) generic S2S models inspired by nature, 4) relationships and feedbacks between human and S2S systems, 5) global to regional scale source-to-sink systems and the economic benefits of thinking in this mindset, and 6) innovative S2S training in academia and industry.

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Co-organized by GM4/SSP3, co-sponsored by IAS
Convener: Francois Guillocheau | Co-conveners: Jean Braun, Charlotte FillonECSECS, Benjamin Gréselle, Tor Somme
Displays
| Attendance Fri, 08 May, 08:30–10:15 (CEST)

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Chat time: Friday, 8 May 2020, 08:30–10:15

D1096 |
EGU2020-3798
Yani Najman, Mike Blum, Jamie Gleason, Kimberly Rogers, Devon Orme, Chris Mark, Dan Barfod, Andy Carter, Randy Parrish, Dave Chew, and Lorenzo Gemignani

The Bengal Fan IODP Exp 354 core provides a Neogene re­cord of eastern and central Himalayan exhu­mation. U-Pb analyses of detrital zircons from this sediment archive shows that from ~ 4 Ma, there was a major increase in grains aged <300 Ma, indicating a major increase in contribution from the Trans-Himalaya (Blum et al., Nature SR, 2018). Detrital rutile U-Pb and detrital zircon fission track data from the same archive (Najman et al, GSAB 2019) indicates an approximately coeval increase in exhumation rate from the Eastern Himalayan Syntaxis. Thus an attractive explanation to explain the increase in Transhimalayan input may be that it was caused by initiation of exhumation of the syntaxis from beneath its Transhimalayan cover. However, a similar dataset obtained from the proximal foreland basin Siwalik deposits (Govin et al., in review) indicates an earlier onset to syntaxial exhumation, compared to that recorded in the distal sediment archive. We consider therefore whether climate change may be responsible for the increased Transhimalayan input: onset of Northern Hemisphere glaciation may have increased the proportion of erosion in the higher, glaciated, regions of the Transhimalaya, compared to that part of the orogen south of the suture zone. Analyses of Hf isotopic composition of detrital zircons to assess the possibility that drainage basin changes may explain the increase in material at 4 Ma, are ongoing. The difference in timing of the syntaxial exhumational signal between the proximal and distal archives may be the result of downstream dilution, or may result from sequestration of material on the shelf, with release to the deep ocean during sea level low stands.

How to cite: Najman, Y., Blum, M., Gleason, J., Rogers, K., Orme, D., Mark, C., Barfod, D., Carter, A., Parrish, R., Chew, D., and Gemignani, L.: The Bengal Fan sediment archive: a record of Himalayan tectonics, climate, and/or drainage routing change between source and sink?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3798, https://doi.org/10.5194/egusphere-egu2020-3798, 2020

D1097 |
EGU2020-6696
Kerry Gallagher and Mark Wildman

Products of onshore passive continental margin erosion are preserved in offshore sedimentary basins. Therefore, these basins potentially hold a recoverable record of onshore erosion. We present a suite of apatite fission track (AFT) data for 13 borehole samples from the southern Walvis basin, offshore Namibia. All of the samples show AFT central ages older or similar to their respective stratigraphic ages, and many single grain ages are older. These data show that none of the samples has been totally annealed post-deposition. Furthermore, the large dispersion in single grains ages in some samples suggests multiple age components. A lack of obvious correlation to compositional proxies implies this dispersion is related to different source regions. Using Bayesian mixture modelling we classify single grain ages from a given sample to particular age components to create ‘subsamples’. Subsequently, we jointly invert the entire dataset of subsamples to obtain a consistent thermal history for the well location. For each sample, the post-depositional thermal history is required to be the same for all age components, but each component has an independent pre-depositional thermal history. With this approach we can resolve pre- and post-depositional thermal events and identify potential changes in sediment provenance over time. In the example we present from offshore Namibia, we constrain the erosional evolution of the continental margin over a longer timescale than has been possible using onshore AFT thermochronological data and or offshore sediment volumes.

 

How to cite: Gallagher, K. and Wildman, M.: From sink to source: extracting onshore erosion signals preserved in offshore thermochronometric data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6696, https://doi.org/10.5194/egusphere-egu2020-6696, 2020

D1098 |
EGU2020-14703
Delphine Rouby, Dominique Chardon, Jing Ye, Flora Bajolet, Artiom Loparev, and Massimo Dall'Asta

We summarize the results of a 7 years study of the sediment routing systems of the West African Craton transporting its erosional products to the Central and Equatorial Atlantic passive margins at geological time scale. We used paleogeograhic maps to define the geodynamics framework of this routing system with in particular the propagation of the Equatorial Atlantic oblique rift separating the West African and Amazonian Cratons. We used sub-surface data to evaluate the evolution of lithosphere necking distribution along the conjugated African and South American margins of the rift system. We estimated the long-term denudation pattern at continental scale from low temperature thermochronology measures of samples from 3 transects perpendicular to the Atlantic margin. We used the exceptional preservation of geomorphologic markers to reconstruct the drainage system of the craton since 45 Ma, and estimate the associated denudation and exports of terrigeneous sediments to the Atlantic margin. Finally, we estimated the accumulation history in the passive margin basins and compare them with the estimated denudation histories from thermal histories and geomorphologic markers. We show that the modes of preservation of sedimentary export in the passive margin basins are highly variable in time (immediate post roft versus late post-rift) and space (transform/oblique versus divergent margin segments). We show that the present day drainage of the West African Craton as been stable since 30 Ma when it underwent a major reorganization driven by the growth of the relief associated with the Hoggar mantle plume. We show that accumulation in the passive margin basins fall within the same order of magnitude than denudation on the craton at the scale of the Meso-Cenozoic. This allows us to argue to the relevance of using the stratigraphic architecture of passive margin basins to estimate the denudation history of their continental domains.

How to cite: Rouby, D., Chardon, D., Ye, J., Bajolet, F., Loparev, A., and Dall'Asta, M.: The Equatorial Atlantic Laboratory: sediment routing systems and lithosphere deformation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14703, https://doi.org/10.5194/egusphere-egu2020-14703, 2020

D1099 |
EGU2020-19537
Luis Valero, Elisabet Beamud, Miguel Garcés, Andreu Vinyoles, Nikhil Sharma, Stephen E. Watkins, Maxime Tremblin, Cai Puigdefàbregas, François Guillocheau, Alex C. Whitakker, Miguel López-Blanco, Pau Arbués, and Sébastien Castelltort

During middle Eocene, the Escanilla fluvial system transported and deposited material from East to West in the southern Pyrenees foreland basin. The paleogeography and sedimentology of the source to sink system is well established. The temporal framework is made of scattered low resolution magnetostratigraphies, and a robust temporal framework in the most distal (Olson) and most proximal (Sis) parts of the system. We built a new high resolution magnetostratigraphy from the middle part of the system, the Lascuarre section. The correlation of Lascuarre with the high resolution magnetostratigraphies and the integration of these data with other available chronological constraints results into a robust complete temporal framework from source to sink.

Sedimentological analyses of the Lascuarre section allow recognizing a set of sedimentary sequences throughout the record. Here we present the result of the analyses, and discuss the relative weight of the different forcing. Particularly, we elucidate the role of tectonics in relation to subsidence distribution patterns, and also the distinct expression of climate. Eventually, we identify and explore the signal propagation mechanisms of climate aberrations and of quasi-regular orbital variations along the routing system.

How to cite: Valero, L., Beamud, E., Garcés, M., Vinyoles, A., Sharma, N., Watkins, S. E., Tremblin, M., Puigdefàbregas, C., Guillocheau, F., Whitakker, A. C., López-Blanco, M., Arbués, P., and Castelltort, S.: Origin and propagation of sedimentary sequences throughout the Escanilla fluvial routing system (South Pyrenean foreland basin), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19537, https://doi.org/10.5194/egusphere-egu2020-19537, 2020

D1100 |
EGU2020-1004
Nikhil Sharma, Jean Vérité, Stephen Watkins, Luis Valero, Alex Whittaker, Miguel Garcès, Cai Puigdefabregas, François Guillocheau, Thierry Adatte, and Sébastien Castelltort

The Middle Eocene Climatic Optimum (MECO) represents an episode of widespread warming occurring ~40 million years ago. It is characterized by gradual warming over a period of 500,000 years, leading to a rise in ocean temperatures of about 5° C in the mid and high-latitudes (Sluijs et al., 2013). Contrary to the traditional understanding and consensus that accommodation space or downstream factors control stratigraphic architecture in fluvial successions, we test the hypothesis that upstream factors, rather than downstream factors, control fluvial architecture through changes in the median grain size, sediment supply and water discharge with paleoslope being a measurable proxy to quantify these changes. We test our hypothesis utilizing the natural system of the Escanilla sediment routing system, encompassing the Middle Eocene Climatic Optimum. The Escanilla system is an overall prograding system, consisting of 1000 m thick alluvial and fluvial deposits at the southern-margin of the Tremp-Graus Basin in the south/central Pyrenees, Spain. Multiple lateral measurements for grain size distributions and cross-set measurements, flow direction and channel geometry are taken close to the source (Coll de Vent), at an intermediate location (Lascuarre), and at a distal part (Olson) of the system for paleohydraulic reconstructions. Drone flight missions are also undertaken to capture aerial photographs of the field area, which are required for the construction of 3D photogrammetric models. At Olson, alternating sequences of laterally continuous amalgamated channel bodies and several small sequences of vertically stacked isolated channel bodies have been identified. Preliminary results show distinct values of median grain size, dune height, flow depth and paleoslope for the amalgamated and vertically stacked isolated channel sequences across the MECO; the addition of our 3D models provide further insight into the lateral connectivity of the amalgamated units. Our results suggest different paleohydraulic conditions during the deposition of amalgamated and nonamalgamated units. This data will also be supported by numerical simulations carried out to better understand the response of fluvial systems to changes in upstream factors.

How to cite: Sharma, N., Vérité, J., Watkins, S., Valero, L., Whittaker, A., Garcès, M., Puigdefabregas, C., Guillocheau, F., Adatte, T., and Castelltort, S.: Upstream versus downstream changes in a natural sediment routing system from source to sink, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1004, https://doi.org/10.5194/egusphere-egu2020-1004, 2019

D1101 |
EGU2020-8224
Alexandre Ortiz, François Guillocheau, Eric Lasseur, Cécile Robin, Justine Briais, and Charlotte Fillon

The purpose of this study is to understand the "source-to-sink" evolution of the Pyrenees system and its retro-foreland basin, the Aquitaine basin and its deep equivalent, the Bay of Biscay during the Cenozoic. This work required (1) a biostratigraphic re-evaluation, (2) an analysis in terms of seismic stratigraphy and quantification of preserved sediment volumes, (3) a quantification of eroded volumes from the Massif Central, (4) a quantification of the eroded volumes from the Pyrenees, (5) a synthesis of all these data.

In the Aquitaine basin, the transition from the orogenic to the post-orogenic phase occurs between 27.1 and 25.2 Ma. The orogenic period is divided into two phases, (1) up to 43.5 Ma (Lutetian), is characterized by a strong subsidence at the front of the North-Pyrenean-Thrust, (2) from 43.5 to 27.1 Ma, is characterized by the subsidence migration toward the basin, in sub-basins controlled by the thrusts and the inverted structures activity. The post-orogenic is identified by the succession of three erosional surfaces that fossilize the entire compressive structures period. This period is divided into two phases, (1) from 25.2 to 16 Ma approximately, corresponds to the establishment of the isostatic rebound in the Aquitaine basin, (2) between 16 and 10.6 Ma, corresponds to an uplift of the whole system. This latter phase corresponds to a West European event undoubtedly linked to a mantle activity.

The total quantity of rocks preserved in the Aquitaine basin and the Bay of Biscay is 92 200 km3. The distribution of sediments preserved over time evolves in favour of the Aquitaine basin between 66.0 and 33.9 Ma and in favour of the Bay of Biscay between 5.3 and 0 Ma. This balance is due to the different stages of evolution of the subsidence / uplift in the Aquitaine basin. The sedimentation rates show two periods of increase in sedimentary fluxes, the first at the Eocene-Oligocene limit in the two basins, which we relate to both the period of Pyrenean paroxysmal exhumation and to contemporary global cooling. The second, at 5.3 Ma exclusively in the Bay of Biscay, seems to correspond to the global increase of fluxes, whose climatic origin is favoured by the authors.

From the inversion of the extensive thermochronological dataset in the Pyrenees and the geomorphological analysis of the planation surfaces of the French Massif Central, we obtained the total amount of eroded rock which is 34 335 km3. The difference observed between the sedimented volumes and the eroded volumes can be explained by the contribution of sediments resulting from the currents from the Pliocene, the not taking into account the volumes coming from the Cantabrian massifs, an underestimation of the eroded volumes and of the terrigenous carbonate fraction in the two basins.

How to cite: Ortiz, A., Guillocheau, F., Lasseur, E., Robin, C., Briais, J., and Fillon, C.: Geometries and source-to-sink analysis of a retro-foreland basin during its late to post-orogenic evolution: the case example of the Pyrenees / Aquitaine Basin / Bay of Biscay from 38 to 0 Ma, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8224, https://doi.org/10.5194/egusphere-egu2020-8224, 2020

D1102 |
EGU2020-8811
| Highlight
Anne Bernhardt and Wolfgang Schwanghart

The efficiency of environmental signal propagation from terrestrial sources to marine sinks highly depends on the connectivity of the sediment-routing system. Submarine canyons that couple river outlets with marine depocenters are particularly crucial links in the routing network as they convey terrestrial sediment, associated pollutants and organic carbon to the deep ocean. However, why and where submarine canyons incise into shelves is still poorly understood. Several factors were proposed, including narrow shelves along active continental margins, onshore sediment flux, more proximal sediment supply during sea-level lowstands, mass wasting along high-gradient continental slopes, and the occurrence of durable bedrock in adjacent catchments. In this study, we test whether we can predict shelf incision of submarine canyons from onshore and offshore parameters.

We used maps of global elevation and bathymetry and analyzed them together with a global compilation of 5900 submarine canyon heads. The analysis relies on bagged regression trees that predict the distance of each canyon head from the shelf edge as a function of numerous candidate predictor variables. These variables describe spatial relations of river mouths and canyons, shelf geometry, continental slope gradient, as well as numerous terrestrial catchment properties. Moreover, we added 120 m to the elevation of the present-day topography to simulate a coastal landscape during the Last Glacial Maximum (LGM) and recalculated the topographic terrestrial parameters and the shelf width.

The trained model explains 66% (R2) of the variance within the data set with a root mean square error (RMSE) of 31 km and a mean absolute error (MAE, less sensitive to outliers) of 17 km. The highest predictor importance is consistently reported for the weighted distance from canyon heads to the adjacent river mouths during the LGM and the present-day catchment gradient. We find no significant influence of shelf width, continental slope gradient and sediment load, and the moderate fit of the model indicates that we are still missing one or more important controls on the spatial location of canyon heads. Our predictions may be refined by including a more detailed assessment of catchment lithologies, locations of submarine groundwater discharge, locations of tectonic faults, and longshore current directions. Notwithstanding, we conclude that our model identifies important controls on the spatial occurrence and shelf incision of submarine canyons and sorts out much debated but seemingly unimportant variables.  

How to cite: Bernhardt, A. and Schwanghart, W.: Why do shelf-incising submarine canyons form? - Insights from global topographic analyses and regression trees, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8811, https://doi.org/10.5194/egusphere-egu2020-8811, 2020

D1103 |
EGU2020-5839
Gareth Roberts, Alex Lipp, Alexander Whittaker, Charles Gowing, and Victoria Fernandes

The composition of sediments in large rivers and the rocks they form in sedimentary basins record provenance, weathering and surface processes. We predict the geochemical evolution of the Earth’s eroding surface from source regions through fluvial systems, and into the sedimentary record using a simple deterministic model. Using a stream power formulation of fluvial erosion we predict the incision rate at any point in an eroding landscape. Combining these predictions with information about the geochemistry of the eroding substrate we predict the composition of the eroded sediment as it is routed through the landscape. This simple approach is tested in a case study of Scottish rivers by comparing predictions with fine-grained sediment composition measurements. The high-density GBASE stream sediment geochemical survey was utilised to predict fine-grained sediment geochemistry along major regional rivers (Spey, Dee, Don, Tay, Deveron). Sediment samples were gathered from river heads to mouths and their bulk geochemical composition was determined by ICP-MS following mixed acid digestion. Predicted geochemistry of major rivers was tested using the new independent geochemical dataset. Using this data we discuss down-system trends in fluvial sediment geochemsitry, and evaluate the success of our model. Finally, we discuss how bulk geochemical data from river sediments can be formally inverted to reconstruct the geochemistry of their source regions.

How to cite: Roberts, G., Lipp, A., Whittaker, A., Gowing, C., and Fernandes, V.: A predictive and invertible model of fluvial sediment geochemistry, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5839, https://doi.org/10.5194/egusphere-egu2020-5839, 2020

D1104 |
EGU2020-8117
Hans Jørgen Kjøll, Ivar Midtkandal, and Sverre Planke

Upper Cretaceous and Paleocene sandstone strata represent promising reservoirs along the NE Atlantic margins, including new discoveries in recent years that has spurred increased activity in the area. Exploration and seismic imaging is complicated by massive Paleocene magmatism related to late rifting and early breakup, forming voluminous sill and dyke complexes hosted in the sedimentary succession and extrusive complexes, such as volcanic edifices and lava flows along the margin. Such igneous activity may have played an important role in the thermal and chemical history of reservoir zones. Their diagenetic properties as well as their physical appearance is expected to have been altered by the intrusions, breaking predictive trends otherwise common for deep-marine sedimentary strata. A new understanding of the nature and implication of igneous processes and deposition of sediments, combined with new understanding of sand source-to-sink systems in the region, is thus important to better evaluate the prospectivity of the southern Møre Basin. The focus of this project will therefore be to asses sand provenance and depositional systems in basins in this area by incorporating on shore field work with integrated borehole and seismic studies. The main goal is to develop a new understanding of deposition of sand fairways during the Late Cretaceous and Paleogene to better understand this part of the break-up history of the NE Atlantic.

How to cite: Kjøll, H. J., Midtkandal, I., and Planke, S.: Late Cretaceous to Paleogene sand provenance, deposition and tectonomagmatic development in the southern Møre Basin, Norway, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8117, https://doi.org/10.5194/egusphere-egu2020-8117, 2020

D1105 |
EGU2020-10004
Li Chang and Andrew Tien-Shun Lin

Gaoping Canyon (GPC) is a river-connected canyon that delivers a vast amount of sediments from the Taiwan mountain belt to the Manila trench of the South China Sea. The canyon course traverses through the actively uplifting accretionary wedge, thus structural activities exert strong controls on the deposition/erosion of the canyon system. In this study, we use an array of data, including multi-beam bathymetry, reflection seismic profiles, sub-bottom profiles, and sediment cores to discuss the interactions among bathymetry, sediment transportation and deposition, and tectonic activity along the GPC.

The bathymetry shows that the GPC can be divided into three segments of upper reach, middle reach, and lower reach, respectively, according to literature. The upper-reach is an erosive meandering channel incising into the Gaoping shelf and upper slope with a thalweg depth (relief) in the range of 200-500 m, and a longitudinal gradient of -1.78 %. The canyon thalweg is mostly erosive with sediments accumulated in a few depressions along the thalweg. Piles of hyperpycnites were found on the thalweg of the canyon head, immediately off the Gaoping river mouth. Sediment cores show that the turbidity currents are mostly confined within the incised valley. The middle reach of GPC is nearly straight and develops along the footwall of the NNW-trending splay fault that separates the upper and lower slope of the accretionary wedge. The thalweg depth is in the range of 500-800 m, featuring the deepest of the canyon thalweg for the GPC, and a longitudinal gradient of -1.52 %. The canyon thalweg is mostly erosive with gravel lags. Sediment cores show that the turbidity currents are mostly confined in the incised valley.

The lower reach can be subdivided into proximal and distal segments. The proximal lower reach features large-radius lateral migrating meanders and abundant landslide scars along the banks/levees of the channel. The thalweg depth is in the range of 130-400 m, and a longitudinal gradient of -0.64 %. The relatively shallow thalweg depth leads to overspilling of the turbidity currents, forming a slope fan on the deforming accretionary wedge. The distal lower reach develops among and cutting through a series of uplifting submarine ridges, leading to small meanders and erosive and by-pass channels.

How to cite: Chang, L. and Lin, A. T.-S.: Morpho-sedimentary features of the Gaoping Canyon System in the accretionary wedge off SW Taiwan, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10004, https://doi.org/10.5194/egusphere-egu2020-10004, 2020

D1106 |
EGU2020-10184
Thomas François, Guillaume Baby, Paul Bessin, Julien Baptiste, Jocelyn Barbarand, François Guillocheau, Éric Lasseur, Justine Briais, and Cécile Robin

Documenting surface uplift of basement areas is challenging, usually due to large gaps in the sedimentary record. In order to address this issue for the French Massif Central, we here investigate its denudation history through an integrated study that involves planation surface mapping, Apatite Fission-Track (AFT) Analysis and basement to basin cross-sections.

First, Planation surfaces were identified using a semi-automated fuzzy classification of pixels based on relationships between DEM derivatives (slope, curvature, ruggedness and incision) and field-recognized training samples.  Then, their different generations and age ranges were discriminated from hypsometry, fault partitioning and relationships with dated sedimentary and/or volcanic remnants, providing constraints on basement exhumation. Afterwards, integrating the previous planation surface analysis, geological cross-sections were produced from the Massif Central basement to the surrounding basins (Aquitaine Basin and Paris Basin). These sections provide local thicknesses estimates of the missing sedimentary cover over basement domains. Theses local thicknesses and exhumation phases were finally used as constraints to produce a thermal history modelling and a denudation map of different areas of the French Massif Central estimated from AFT inversion.

Our results show different burial and exhumation patterns with i) a main burial of its western parts (Limousin, Rouergue) during Jurassic times followed by an important regional denudation (1 to 2 km of missing cover and crystallized basement) during the early Cretaceous and ii) an Upper Cretaceous burial of its northeastern parts (Morvan, Forez) followed by an uppermost Cretaceous to Paleogene exhumation (<1 km of missing cover and crystallized basement). This further illustrates the different behavior of each units of the Massif Central during the Mesozoic to Cenozoic times. These results will ultimately be discussed and placed back into the western European deformation framework.

 

(This work is founded and carried out in the framework of the BRGM-TOTAL project Source-to-Sink)

How to cite: François, T., Baby, G., Bessin, P., Baptiste, J., Barbarand, J., Guillocheau, F., Lasseur, É., Briais, J., and Robin, C.: Denudation history of the French Massif Central: new insights from thermochronology, basement-basin cross-sections and semi-automated planation surfaces mapping, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10184, https://doi.org/10.5194/egusphere-egu2020-10184, 2020

D1107 |
EGU2020-12866
Francois Guillocheau and Cécile Robin

The consideration of entire “Source to Sink" systems is one of the most recent and challenging advances in earth surface dynamics and sedimentary geology. To understand S2S systems it is necessary to enhance sharing of knowledge and concepts between (1) geomorphology, which focuses on the understanding of erosion processes driving landform evolution and sediment fluxes, (2) stratigraphy/sedimentology, which focuses on the nature of sedimentary deposits and their distribution in time and space, and (3) tectonics and structural geology, which set the dimensions, geometry and dynamics of source/transfer areas and sedimentary basins (the sink). Understanding S2S systems also involves other Geosciences disciplines such as paleoclimatology and geochemistry, because they allow quantifying the factors controlling S2S systems dynamics (climatic controls on erosion, solid vs. solute fluxes, etc.).

The main challenges are (1) to get all the above mentioned disciplines working together on geological or numerical approaches of the whole S2S system, in different tectonic and climatic settings and (2) to convince some industries of the merits of this approach, e.g. industries dealing with geothermy or granulates.

We here present one example of academia – industry transfer of knowledge for granulates: the low accommodation alluvial system of the Armorican Massif of Messinian to Pliocene age, major source of granulates for the development of the Brittany Province (western France). The understanding of the base level fluctuations sensuWheeler (1964), joined to an knowledge of the uplift history, the climate variations, and the source of sediments (Eocene laterite profiles) gave tools for a better prediction on the location and quality of the granulates.

How to cite: Guillocheau, F. and Robin, C.: Signal propagation in sediment routing systems: an application for granulates prediction (location, grain-size), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12866, https://doi.org/10.5194/egusphere-egu2020-12866, 2020

D1108 |
EGU2020-13087
Sébastien Rohais, Youri Hamon, Rémy Deschamps, Valérie Beaumont, Marta Gasparrini, Daniel Pillot, and Maria Fernanda Romero-Sarmiento

In this contribution, we present a source-to-sink (S2S) analysis of the Late Cretaceous to Early Cenozoic Yacoraite Formation, a typical lacustrine source rock from the Salta rift Basin (NW Argentina). The Yacoraite Formation corresponds to a mixed carbonate-siliciclastic lacustrine sedimentary system, deposited during the sag phase (post-rift) and also records the K-T boundary. An integrated S2S approach was applied using sedimentary, geochronology, geochemical and isotopic datasets at basin scale (ca. 200 x 200 km), to better understand the complex interactions between production, destruction, and dilution processes that characterize the dynamic of organic-rich sediments. These data are used here to discuss the high-resolution (time step ca. 0.05-1 Myr) patterns of organic carbon enrichment in a lacustrine system across the K-T boundary.

Results show that the Yacoraite Formation recorded major climate changes that can be documented in terms of catchment dynamic, erosion processes, carbonate accumulation trends, lacustrine dynamic and source rock quality. The background organic matter corresponds to a Type I kerogen dominated by algal growth (mean HI 600-800 mgHC/gTOC, TOC0 1-2 wt.%). The K-T boundary was the climax of a climate change initiated ca. 0.3 Myr before that induced a major change in the catchment weathering processes, which temporally corresponds to the accumulation of poor quality source rock intervals (TOC0 ≤ 0.2 wt.% and HI < 50 mgHC/gTOC) in these series. The location of the K-T boundary is highlighted by a main negative anomaly in δ13C of the carbonate deposits in the Yacoraite Formation, as also supported by absolute U-Pb dating of inter-fingered volcanic ashes. It was followed by a major pulse in paleo-productivity, in turn followed by a major pulse in TOC0 (10-15 wt.%) under anoxic conditions. In ca. 0.2 Myr the lacustrine dynamic and the related organic-carbon enrichment resumed to their initial setting, just prior to the preluding K-T boundary climate change. The obtained results suggest that the Yacoraite Formation can be considered as a world-class example to illustrate how the K-T boundary is recorded in lacustrine sediments. In particular, it could be used as reference to address key questions related to cross-scale interactions, feedback loops and temporal dynamics in the sedimentary record.

How to cite: Rohais, S., Hamon, Y., Deschamps, R., Beaumont, V., Gasparrini, M., Pillot, D., and Romero-Sarmiento, M. F.: Source-to-Sink (S2S) analysis of a lacustrine system across the K-T boundary: the Yacoraite Formation, Salta rift basin, Argentina, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13087, https://doi.org/10.5194/egusphere-egu2020-13087, 2020

D1109 |
EGU2020-14027
Nicolas Marie, François Guillocheau, Justine Briais, Cécile Robin, and Eric Lasseur

Understanding the source-to-sink system in sedimentary basins supposes the characterization of two key parameters: the source and the mode of sediment production (physical vs. chemical erosion), as well as the distance of the transfer zone. The shape of the quartz grains may record (1) the chemical vs. physical production of the grain, (2) the processes (eolian vs. fluvial) of sediment transfers, and (3) possible post-deposition emersion and weathering.

The criteria to distinguish chemical erosion are microstructures linked to dissolution (oriented etch pits, solution pits, solution crevasses and scaling) or precipitation (crystalline overgrowths and silica globules, flowers and pellicle). The difference between eolian and fluvial processes is mainly based on the roundness and the type of impact (conchoidal breakage, percussion marks and grooves).

This approach was successfully applied to the Cenozoic of the Paris Basin, a low accommodation sedimentary system (maximum 200 m in 35 Ma) encompassing numerous hiatuses. The source was mainly subjected to chemical erosion, since etching microstructures are often observed overcut by eolian or fluvial transport criteria. This chemical weathering is thought to has been particularly pronounced during Paleocene and Early Eocene times. Eolian transport occurred preferentially during Danian, Lutetian and Bartonian times whereas fluvial transport appears dominant in Danian, Thanetian and Ypresian times. Major emersion marked by in situ laterites growing occurred during Late Paleogene times, Ypresian and Bartonian, with minor ones during Thanetian. This is testified by the superimposition of chemical weathering features on grains smoothed by fluvial and/or eolian transport.

How to cite: Marie, N., Guillocheau, F., Briais, J., Robin, C., and Lasseur, E.: Quartz grain shape using S.E.M in source-to-sink studies (production and transfer): the case exemple of the Cenozoic of the Paris Basin, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14027, https://doi.org/10.5194/egusphere-egu2020-14027, 2020

D1110 |
EGU2020-15932
Stephen E. Watkins, Nikhil Sharma, Luis Valero, Maxime Tremblin, Abdallah S. Zaki, Frédéric Arlaud, Guy Simpson, and Sébastien Castelltort

Stratigraphic architecture of fluvial deposits is often interpreted as a record of changes in accommodation created by absolute sea-level change, subsidence, or a combination of both (downstream drivers). An increase or decrease in accommodation causes the fluvial system to respond by either aggrading or degrading to a new equilibrium slope. However, in recent years the role of upstream drivers, such as water discharge and sediment supply (volume and grain-size distribution), in controlling equilibrium slopes has gained more importance, however we still lack significant understanding of these upstream processes. It is important to be able to differentiate between stratigraphy influenced by upstream and downstream drivers in the field because fluvial deposits represent an important archive of environmental changes.  Traditionally, downstream drivers are often invoked to explain past accommodation changes, but in actuality there are rarely robust constraints on the cause of these space changes. At present there is still no well-documented examples of upstream versus downstream driven stratigraphic architecture. One way to address this issue is by undertaking analogue modelling (i.e. flume experiments) as this permits the isolation of individual parameters, such as water discharge, and allows us to investigate their role on the fluvial system in a controlled environment.

 

In the first part of the project that we present here, we investigate how sediment aggradation within a channel develops through time by using a quasi-2D flume.  We have designed and manufactured a narrow (0.05 m), long (2.4 m) flume with an initial gradient of zero.  We aim to (i) investigate how aggradation occurs through time using a series of different water discharges, sediment supplies and sediment concentrations and observe the resulting equilibrium slopes; (ii) perturb the system once equilibrium is reached to observe the readjustment of the system to new conditions; (iii) carry out a series of experiments varying downstream drivers (i.e. sea-level) which theoretically produce the same amount of aggradation as the upstream parameters we have used do, we will then be able to compare any similarities or differences in stratigraphy.  Ultimately we will use these results to scale up to a fully three-dimensional analogue model (i.e. a wide flume, approximately 1 m) that produces channels and floodplains.  We can then investigate how the upstream and downstream changes seen in the narrow flume are translated into the wider flume.

How to cite: Watkins, S. E., Sharma, N., Valero, L., Tremblin, M., Zaki, A. S., Arlaud, F., Simpson, G., and Castelltort, S.: How do river channels aggrade? An investigation into the importance of upstream drivers (water discharge and sediment supply) on sediment aggradation using analogue modelling , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15932, https://doi.org/10.5194/egusphere-egu2020-15932, 2020

D1111 |
EGU2020-10814
Tor O. Sømme, Jakob Skogseid, Patricia Embry, and Helge Løseth

Landscapes and their sediment routing systems can be exposed to various tectonic and climatic perturbations that affect sediment production, transport and delivery to nearby sedimentary basins. Here we investigate a Paleogene depositional system offshore western Norway that was subjected to long-term (~10 Myr) tectonic perturbation and significant hinterland erosion. Superimposed on this long-term uplift, the system was also subjected to a short-lived climatic perturbation during the Paleocene-Eocene Thermal Maximum (PETM), which lasted ~200 kyr. Regional 3D seismic reflection data is integrated with high resolution well data to map the stratigraphic response to these different scales of perturbations on the depositional system. The initiation of the tectonic perturbation is marked by an angular unconformity in seismic data. A rapid increase in sediment flux followed, causing initial progradation of a shelf-slope wedge. Sediment supply estimates indicate that the tectonic uplift caused an order of magnitude increase in sediment flux to the basin, which peaked in the latest Paleocene. This period coincided with the PETM, which is documented by biostratigraphic data as a discrete event within the overall regressive system. Although the PETM often is characterised by increased continental runoff, no increase in sediment supply is evident from seismic data. This work shows that the system response to tectonic and climatic perturbations may vary along strike, depending on the size of the routing systems and the antecedent topography prior to hinterland uplift. A low supply system may produce a tectonically-linked shelf-slope wedge that is of similar thickness as a climatically-linked wedge in a high supply system. This study documents how the same routing system responded to perturbations operating at different spatial and temporal scales and may help recognise similar process-response relationships in other areas.

How to cite: Sømme, T. O., Skogseid, J., Embry, P., and Løseth, H.: Recognising tectonic and climatic signals in the Paleogene stratigraphy offshore Norway , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10814, https://doi.org/10.5194/egusphere-egu2020-10814, 2020

D1112 |
EGU2020-10853
Miguel Garcés, Miguel López-Blanco, Elisabet Beamud, Josep Anton Muñoz, Pau Arbués, Luis Valero, and Andreu Vinyoles

The Early Eocene was the period of most intense plate collision during the building of the Pyrenean orogen. Tectonic loading of the overriding European plate caused flexure of the subducting Iberian plate and formation of an elongated foredeep connected westward with the Atlantic Ocean. The uneven distribution of the Triassic evaporites caused the formation of a thrust salient in the central Pyrenees related to tectonic inversion of the pre-existing Mesozoic rift basins. This process ultimately resulted in the partitioning of the foreland basin and the isolation of the Ripoll Basin in the East from the Tremp-Graus and Ainsa-Jaca basins in central and western south-Pyrenees. The precise timing and the surface processes related to this reorganization of the sediment routing system remains not fully understood. Early tectono-stratigraphic reconstructions envisaged a scenario of isolation of the eastern Pyrenean Foreland basin in the early Eocene, while other recent studies on detrital zircon geochronometry suggest that the sedimentary transfer system in the Tremp-Graus basin connected upstream to the Ripoll basin until middle Lutetian times. In this contribution we discuss constraints on the early Eocene paleogeography of the south-eastern Pyrenees in the light of a revised chronostratigraphic scheme. We put forward a scenario that tries reconciling all available structural, stratigraphic, petrologic, geochronologic, and sedimentologic datasets.

How to cite: Garcés, M., López-Blanco, M., Beamud, E., Muñoz, J. A., Arbués, P., Valero, L., and Vinyoles, A.: Reconstructing the Early Eocene Sediment Routing System of the south-eastern Pyrenees, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10853, https://doi.org/10.5194/egusphere-egu2020-10853, 2020

D1113 |
EGU2020-11284
Laure Guerit, Delphine Rouby, Cécile Robin, François Guillocheau, Brendan Simon, and Jean Braun

Foreland basins that develop at the foot of collisional mountain belts accumulate sediments eroded from the ranges. They thus represent valuable archives of the evolution of orogenic systems through time. A few numerical models have investigated the infilling of foreland basins during the growth of an orogenic range and they provide conceptual frameworks for foreland stratigraphy. However, surface processes (erosion, sediment transport and deposition) are often quite basic in these models, and in the last decade, progress has been made in the description of surface processes and its implementation in numerical models. Recently, we developed a landscape evolution model able to describe the evolution of an eroding source coupled to a flexural sedimentary basin (Yuan et al, 2019, JGR; Guerit et al, 2019, Geology). This model takes into account erosion and deposition at the same time, and it thus allows a full dynamical coupling of the range and its foreland. We take advantage of this efficient numerical model to take another look at the stratigraphic evolution of a foreland basin and at the transmission of sediment signal from source to sink. 
We use the model to simulate the evolution of a flexural retro-foreland basin coupled to an uplifting range and subjected to temporal variations in uplift and precipitation rates. Such variations affect the topography of the range: a lower uplift rate or an higher precipitation lead to a lower range. As a result, because the accommodation space available in the foreland is purely flexural, a decrease in uplift rate or an increase in precipitation rate will be marked by an erosional surface in the foreland basin. On the contrary, an increase in uplift rate or a decrease in precipitation rate will be preserved in the stratigraphy. Interestingly, although the two scenarios induce a different sediment signal from the sources, they are both recorded in the foreland basin as a transient increase in accumulation rate. Such a signal alone can therefore not be used to decipher the type of perturbation that affected the source.
Finally, we discuss the evolution of a natural range and coupled foreland basin, the Pyrenees and the Aquitaine Basin. We show that the spatial pattern of sediment deposition in the Aquitaine Basin is very consistent with the topographic evolution of the Pyrenees. However, this topographic evolution is not consistent with the climatic and tectonic reconstruction in the area since the Eocene, opening discussions among others about local vs regional effects. This work is part of the COLORS project, funded by Total.

How to cite: Guerit, L., Rouby, D., Robin, C., Guillocheau, F., Simon, B., and Braun, J.: Stratigraphy and sediment signal transmission in a flexural foreland basin dynamically linked to an uplifting range, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11284, https://doi.org/10.5194/egusphere-egu2020-11284, 2020

D1114 |
EGU2020-18902
Graeme Nicoll, Joss Smith, and Benjamin Gréselle

In frontier settings where data are limited or nonexistent, exploration often relies on predictive models to define uncertainty and derisk decisions. However, helping predict the spatial and temporal extent of geological elements in ancient systems is often challenging and requires a combined multidisciplinary methodology and mindset. The benefits of following a holistic Earth system science approach to the global-scale prediction of petroleum system elements are discussed.

Building on spatial and temporal frameworks provided by plate tectonic and sequence stratigraphic modelling, palinspastic gross depositional environment maps can be integrated with numerous data sets to generate useful paleo-digital elevation models (PDEM) for discrete time slices of the Earth’s history. With a reliable depiction of ancient landscapes and bathymetry, these global PDEMs are instrumental in identifying sediment source areas, which facilitates modelling of paleodrainage pathways. These PDEMs form an essential input to run global paleoclimate and paleotidal simulations, which, in turn, provide a wide range of useful parameters. In combination, paleodrainage and paleoclimate outputs allow for a predictive source-to-sink approach, which provides useful insights away from data constraints.

To highlight the predictive capabilities of this approach, the focus is on the Cretaceous paleo-margin from Guyana in northeast South America to Morocco in northwest Africa. The generation, quality, and distribution of clastic and carbonate systems related to the changing geomorphological and climatic evolution of the central Atlantic domain are discussed.

Within this prospective region, climatic trends are demonstrated (i.e., an intensification of precipitation along the equatorial margin and a progressive aridification in northern Africa) and their implications are discussed. For a range of Cretaceous time-slices, predictions of sediment flux, submarine fan dimensions, and hinterland composition, which provide useful insight into potential reservoir extent and quality along this margin, are demonstrated. By integrating climate, sediment flux, and sediment composition predictions, a margin-wide screening for clastic reservoir potential highlighting areas where existing plays could be extended (MSGBC) and where climatic controls add significant potential risk to reservoir presence and quality (Morocco) are presented.

How to cite: Nicoll, G., Smith, J., and Gréselle, B.: Source-to-Sink Systems in the Central Atlantic: Cretaceous Climate Transitions and the Consequences for Reservoir Distribution, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18902, https://doi.org/10.5194/egusphere-egu2020-18902, 2020

D1115 |
EGU2020-18895
Brendan Simon, Cécile Robin, Delphine Rouby, Xiaoping Yuan, Laure Guerit, Jean Braun, and François Guillocheau

One major and under-appreciated aspect of coupled erosion-deposition numerical modeling is the ranges of input parameter values used to simulate natural source to sink systems without considering their meaning in term of erosion, transport and deposition processes. Most of the time, numerical models are used as a semi-inversion tool based on a “best-fit” approach, especially in its marine part where it aims to reproduce well-constrained sedimentary architectures which are great recorders of landscape evolution through time.

In this study, we performed several simulations using a new numerical landscape evolution model that accounts for both erosion and deposition onshore, as well as sediment deposition in the marine domain (Yuan et al., 2019; COLORS project, funded by Total). In the marine domain, sediment dynamic is described by a diffusion equation and the diffusion or transport coefficient has been calibrated from natural delta geometries. This model is highly efficient and allows the separation of the different processes involved and exploration of various setups and parameters values in order to address a large variety of questions. Its efficiency also allows inverse simulations that are powerful to determine the best possible scenarios in terms of climatic or tectonic reconstructions, or to determine the evolution of several key parameters.

In order to evaluate the model reliability to reproduce realistic sedimentary geometries, we explore the impact of perturbations in climatic, eustatic or tectonic parameters of the model on the stratigraphic architecture of passive margins shelf-edge deltas and discuss its feedbacks with the erosion dynamic of the onshore domain. This sensitivity analysis also allowed us to define the most relevant geometrical parameters of observed or theoretical stratigraphic architectures that have to be include in the misfit function of the inversions and optimization scheme.

This study is part of the COLORS project, funded by Total.

How to cite: Simon, B., Robin, C., Rouby, D., Yuan, X., Guerit, L., Braun, J., and Guillocheau, F.: Passive-margin delta stratigraphy from source-to-sink numerical models: parametric studies and comparison with natural systems, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18895, https://doi.org/10.5194/egusphere-egu2020-18895, 2020