Nature and dating of karstic filling in the Hainaut Province (Belgium). Karstic, geodynamic and paleogeographic implications

The Carboniferous limestones of the Hainaut Province (Belgium) provide evidence of complex karstification. The forms and deposits recently discovered are (1) ghost-rocks with residual weathered and decayed rock, (2) fluviatile endokarsts filled with pebbles rounded by rolling, and (3) ghost-rocks taken up later by underground fluviatile erosion and containing sandy and clayey deposits. We here provide a detailed sedimentological description, a granulometric study, a palynological dating and geochronological dating (K-Ar method on grains of glauconite and ferriferous illite) of the karstic filling. This palaeokarst stratigraphy of the studied area allows us to propose the following evolution: (1) a fluviatile endokarstification in a hummocky relief in late Early Cretaceous and early Late Cretaceous, (2) the formation of ghost-rocks on a flat relief during the Cenomanian-Turonian, (3) fluviatile deposition of sands and clays filling, as a result of tectonic reactivation during the Maastrichtian-Danian. This multidisciplinary study, taking into consideration karstic, hydrodynamic, tectonic and palaeogeographic factors within a well-defined stratigraphic framework may be of use in studying of the palaeokarst successions.