3. STRATIGRAPHIC SETTING
Dinantian biostratigraphy is mainly based upon foraminifera, rugose corals (Poty, 1985) and conodonts. The biozonation synthesis published by Conil et al. (1991) is followed here except for minor corrections and refinements (Hance et al., 2001).
The Devonian/Carboniferous (D/C) boundary is defined by the entry of the conodont Siphonodella sulcata within an evolutionary lineage S. praesulcata – S. sulcata . This entry follows the Hangenberg event, responsible for the demise of Devonian fauna and reflecting a drastic sea-level drop (Paproth, 1986; Dreesen et al., 1988). In southern Belgium, this event is recorded by a metre-thick bed of rudstones and grainstones with lithoclasts, ooids, crinoids and a reworked Devonian fauna. The D/C boundary has classically been placed at its top, but the diagnostic conodont is lacking at this level (Paproth et al., 1983; Conil et al., 1986).
The boundary between the Dinantian and Silesian subsystems corresponds to Visean/Namurian (Serpukhovian) boundary, whereas the Mississippian/ Pennsylvanian boundary corresponds to the Serpukhovian/Bashkirian boundary.
The Dinantian is divided into two series, Tournaisian and Visean. Five stages were distinguished by Conil et al. (1976) and Paproth et al. (1983), from base to top: Hastarian (Lower Tournaisian), Ivorian (Upper Tournaisian), Moliniacian (Lower Visean), Livian (Middle Visean) and Warnantian (Upper Visean). However, subsequent work (Conil et al., 1989) has shown that the Ivorian/Moliniacian boundary (base of Cf4a1 foraminifera Subzone) does not correspond to, and is lower than the Tournaisian/Visean boundary (which lies at the base of Cf4a2).
Nine third-order sequences have been recognized by Hance et al. (2001) in the Dinantian of Belgium and northern France. The earliest of these starts in the latest Famennian and extends across the D/C boundary.
