4D forward stratigraphic modelling of the Late Quaternary Congo deep-sea fan : Role of climate/vegetation coupling in architectural

Dimitri Laurent (1) , Tania Marsset (1) , Laurence Droz (2) , Didier Granjeon (3) , Stéphane Molliex (2) , Marie Picot (2) , Marina Rabineau (2)

1 GM - Unité Géosciences Marines
2 IUEM - Institut Universitaire Européen de la Mer
3 IFPEN - IFP Energies nouvelles

The relative impacts of autogenic and allogenic controls on the architectural evolution of deep-sea fans are not well constrained, mainly because of the difficulty in evaluating the role of each control on any specific stratigraphic pattern. This study presents four-dimensional (4D) forward stratigraphic modelling of the Late Quaternary Congo Axial Fan, which provides new insights on forcing factors of sedimentation over time. This modelling is based on a geological model describing successive sedimentary progradational/retrogradational cycles in the Congo turbidite system during the last 38 kyr. Analyses of geophysical and marine core data have suggested that the architectural cycles were controlled by changes in fluvial sediment discharge in relation to arid and humid periods in the Congo River watershed. The aims of this study were to simulate the architectural evolution of the Late Quaternary Congo Axial Fan from 210 ka to the present and investigate the factors controlling sedimentation using DionisosFlow™, a process-based stratigraphic forward modelling software. For this objective, several scenarios were tested to simulate the role of autogenic and climate forcings based on proxies recorded in marine sediments. The modelling results confirmed that climatic variations of sediment and water discharge succeeded in reproducing the timing, position, and sediment volume of basin-scale progradational/retrogradational cycles. The best-fit simulations particularly emphasise the role of continental vegetation cover expansion, governed by the precession-driven West African monsoon, on the sediment flux to the deep-marine environment. This vegetation/climate coupling acts directly on the transport capacity of flow over time by controlling the magnitude of river runoff and the timing of sediment production, storage, and transfer from the continent to the ocean. Thus, our results confirm the utility of stratigraphic forward models in constraining “source-to-sink” models for the architectural evolution of submarine fans.

Mots clés: Congo; Quaternary; turbidite system; deep-sea fan; vegetation/climate coupling; sedimentary cycles; geophysical data; stratigraphic modelling; DionisosFlow TM; palaeoclimate

Domaines: Sciences de la Terre; Sciences de l'environnement; Géochimie; Climatologie

Dimitri Laurent, Tania Marsset, Laurence Droz, Didier Granjeon, Stéphane Molliex, et al.. 4D forward stratigraphic modelling of the Late Quaternary Congo deep-sea fan : Role of climate/vegetation coupling in architectural. Marine Geology, 2020, 429, pp.106334. ⟨10.1016/j.margeo.2020.106334⟩. ⟨hal-02973284⟩