SEDIMENTOLOGY AND PALEOENVIRONMENT OF THE UPPER VISEAN ANHYDRITE OF THE FRANCO-BELGIAN CARBONIFEROUS BASIN (SAINT-GHISLAIN BOREHOLE, SOUTHERN BELGIUM)

The Upper Visean (Carboniferous) evaporitic basin of the Franco-Belgia n Variscan domain is represented by the thick anhydrite series cored a t Saint-Ghislain (Hainaut, southern Belgium) and Epinoy 1 (northern Fr ance). Although the sedimentary record has been modified by post-depos itional events (early and late diagenesis, tectonics), a study based o n sedimentology, stable isotope data (sulphates and carbonates) and mi cropalaeontology of the Upper Visean (V3) stratigraphic interval from Saint-Ghislain, allows reconstruction of the evaporitic sedimentation processes and the establishment of a palaeogeographic framework. Most of these Ca-sulphate deposits were subtidal. Deposition occurred in a shallow-water, marine-fed lagoon or ''salina'' filled by a cyclic shoa ling-upward sequence mainly composed of Ca-sulphates associated with c arbonates.