Seismic and stratigraphic characterization of karstogenic horizons in a sequence of carbonate deposits: Example of the Dogger limestones of the Poitou threshold

Abstract

The Deffend Hydrogeological Experimental Site (HES), near Poitiers, has been the site of numerous studies that have shown that the Bajocian and Aalenian limestones were modified by the horizontal development of multiple karstification planes. These investigations have demonstrated the occurrence of stacked circulation. The origin of the structures that generated these sub-horizontal flows has not been specifically explained. Geophysical investigations were conducted at the site, both at the surface (3D seismic) and in wells (vertical seismic profile (PSV) and acoustic logging). Comparison of the geophysical data, mainly acoustic logs, and a stratigraphic interpretation of cuttings and borehole wall imaging makes it possible to propose a coherent karstogenesis scheme that does not involve tectonic constraints. This article offers an explanation based on gaps recorded in the sequence of Dogger deposits. The karstogenic horizons are linked to sedimentary discontinuities that geologists have identified on the Poitou threshold.