Stratigraphic Architecture of Early Channel-Fill Within an Interbasinal Conduit: Grand Coyer, Grès d’Annot Formation, SE France

Tomasso, Mark¹, Renaud Bouroullec¹, Keumsuk Lee¹, David R. Pyles¹ (1) The University of Texas at Austin, Austin, TX

Sediments within deep-water confined basin settings form prolific hydrocarbon reservoirs. These confined basins are often connected by canyon-like conduits that provide a transport corridor from one basin to another. Many of these conduits are also sediment filled and form prospective reservoirs.

The earliest fill within an interbasinal conduit records the transition from bypass to deposition as the slope is healed. An analogous exposure of one such conduit crops out at Grand Coyer, which formed a northwesterly transport path between two minibasins of the Eocene-Oligocene Grès d'Annot Formation of southeastern France.

The stratigraphy of the early fill of the conduit can be considered in proximal and distal localities, each with specific axial and marginal depositional settings. The proximal, southern, part of the fill was initially dominated along the axis by MTC deposits that locally exhibit movement back towards the still underfilled updip minibasin. These MTCs are overlain by a series of laterally- and vertically-offset amalgamated channel complexes, comprising up to boulder-grade sediments. Towards the margins at the proximal end of the conduit, the channels are non-amalgamated and laterally offset, and are contained within a finer-grained mudstone-rich background. Distally within the conduit, the axial sediments remain coarse and channelized. Syn-sedimentary deformation, including growth faulting and mud volcanoes, is prevalent here, with direction of movement to the north and east. The margins at the distal end of the conduit are finer-grained, with the strata comprising thinly-bedded sandstone and mudstone and occasional isolated sandstone-rich channels.

The lessons learned from this study concerning the tectonostratigraphic evolution of this large deep-water conduit as well as its stratigraphic architecture can be used to better quantify reservoir distribution in many tectonically controlled deep-water basins.