A mud-filled submarine canyon cutting through a sand-prone turbidite succession: A Lower Oligocene field analogue of stratigraphic-structural trap in the Western Alpine Foreland Basin, France

Submarine canyons are key elements of the evolution of convergent margins. Their infilling can be mud-prone and thus represents a good seal if they cut through reservoir series, this erosion phase may be enhanced by tectonic activity. The present study focuses on the Western Alpine Foreland Basin where we use the outcrops of the Schistes à Blocs Formation to study the syn-tectonic evolution of a Lower Oligocene submarine canyon that cuts through the Annot Sandstones Formation. The Intra Schistes à Blocs Erosion Surface (ISaBES) has been mapped in the field. Airborne and drone pictures were also used. Moreover, the deposition model and the stratigraphic architecture of the canyon-fill were reconstructed from the analysis of seven sedimentary logs cumulating 410 m of series, particularly crossing the under described Schistes Bruns Member. The sedimentary system of this lower unit of the canyon-fill has been also constrained by the measurement of paleocurrents, and the provenance analysis of detrital zircons from four samples. The paleocurrent measurements on the unidirectional ripples deposited within the Schistes Bruns Member is witness of a turbulent flow rebound against the steep northern flank of the canyon, during the construction of internal levees which often experimented gravity collapse. Slumping of internal levees improves the seal properties of the canyon-fill, while the canyon thalweg was dominated by by-pass processes. Detrital zircons reveal that the provenance of the Schistes Bruns Member is sourced by the same sedimentary system of the Annot Sandstones Formation. Thus, we interpreted that both the canyon excavation and the sediment by-pass within its thalweg during the deposition of the Schistes Bruns Member, were triggered by an increase in basin slope related to the tectonic evolution of the accretionary prism. Finally, the ISaBES is a composite and diachronous surface resulting both from the morphology of the internal levees, and from their reworking during the deposition of the olistostromes of the Schistes à Blocs Exotiques Member, that predates the emplacement of the Alpine nappes within the foreland basin.