Subaerial exposure unconformities on the Vercors carbonate platform (SE France) and their sequence stratigraphic significance

Outcrops at the margin of the Cretaceous Vercors platform expose prograding to aggrading tongues of platform grainstones. Growth and lateral progradation of these platform tongues was frequently interrupted. Petrographic and geochemical analyses have been carried out at strategic bedding surfaces in order to evaluate the extent to which these breaks relate to sea-level falls and subaerial exposure. The analyses reveal evidence for minor meteoric alteration at all four of the bedding surfaces on the platform top that were studied. However, the Surface 3 bedding plane is unique in that it shows the overprinting of several events of meteoric diagenesis. Within the framework of changing stratal geometries at the margin of the Vercors platform, the exposure Surface 3 represents a rather insignificant event. In contrast, the most prominent break in depositional style at the Vercors platform-margin exhibits only minor meteoric alteration along its platform-top continuation. This "stratigraphic mismatch' suggests that sea-level falls exposing the platform-top exerted only a minor influence on the resulting platform stratal geometries. -from Authors