%0 Conference Proceedings %T THE EARLY POST-RIFT INCISED-VALLEY FILLS ALONG THEEASTERN MARGIN OF THE CONGO BASIN (SOUTH ATLANTIC),APTIAN CHELA FORMATION %+ Géosciences Rennes (GR) %+ Institut Polytechnique LaSalle Beauvais %+ Total TEPNG %A Kebi-Tsoumou, Sage Paterne %A Guillocheau, François %A Robin, Cécile %A Bailleul, Julien %A Delhaye-Prat, Vincent %< avec comité de lecture %B International Meeting of Sedimentology 2017 %C Toulouse, France %3 Abstract book %P 460 %8 2017-10-10 %D 2017 %Z Sciences of the Universe [physics]/Earth Sciences/Tectonics %Z Sciences of the Universe [physics]/Earth Sciences/StratigraphyConference papers %X The Congo basin displays marginal incised-valley fills, which are for longtime missed of in manyprevious geological studies. We have mapped three of these incised-valley systems, informally namedDoumanga, Nkougniand and Mboubissi incised-valley systems, which extend from the Mayombebelt in thenortheast to the Lower Congo basin in the southwest. In the study area, the incised-valleys cut into thePrecambrian metamorphic and magmatic rocks of the Mayombe Basement. Detailed field mapping revealsthat the location and morphology pattern of these incised-valley systems were strongly controlled by bothtectonic structures and lithology heterogeneities of the underlying basement. They are thought to be cut byrivers which incised into the Precambrian basement and acted as bypass systems prior to their infilling. Theseincised-valleys systems were filled with Aptian non-marine siliciclastic sediments of the Chéla Formation thatis well characterized thanks to rich ostracod and pollen associations. Deposition occurred during the so-calledsag phase subsequently to the Aptian regional transgression recorded in the central segment of the SouthAtlantic. The main sedimentary facies documented in the Chéla Formation are clast and matrix supportedconglomerates, structureless and graded sandstones, cross-stratified sand and sandstones, horizontallaminatedsand and silt, interbedded sand and silty shale, and organic rich silty shale and shale, which have been groupedinto six facies associations interpreted as deposits of flood dominated fan-delta and subaqueous faninterfingering with organic rich lacustrine shales. These deposits are organized into a transgressive sequencebounded at its base by a major angular unconformity and characterized by recurring stacking of finingupwardsedimentary packages. It can be suggested that these incised-paleovalleys were filled in the form ofbackstepping fluvio-lacustrine depositional environment subsequently to the rapid lake level rise during theAptian period. %G English %L insu-01718034 %U https://insu.hal.science/insu-01718034 %~ INSU %~ UNIV-RENNES1 %~ UR2-HB %~ CNRS %~ GR %~ OSUR %~ GIP-BE %~ UR1-HAL %~ UR1-SDLM %~ GR-PPDB %~ UNIV-RENNES2 %~ TEST-UR-CSS %~ UNIV-RENNES %~ UNILASALLE %~ INRAE %~ UR1-ENV %~ GR-R %~ TEST3-HALCNRS %~ TEST4-HALCNRS %~ TEST5-HALCNRS