BURIAL HISTORY OF PALEOZOIC STRATA IN BELGIUM AS REVEALED BY CONODONTCOLOR ALTERATION DATA AND THICKNESS DISTRIBUTIONS

Thickness distributions of Devono-Carboniferous formations and their r elationship to conodont colour alteration indices (CAIs) from over 500 sample locations in Belgium and northern France have been studied to reconstruct the thermal alteration and burial history of Palaeozoic ro cks. The depositional centre during Eifelian through Visean times was located in the subsiding southern part of the Dinant Basin, forming a thick sedimentary pile of probably more than 3.5 km. In order to expla in conodont CAIs chiefly resulting from Upper Carboniferous sedimentat ion, two different depositional centres are considered, giving rise to approximately 4.5 km of sediment in the central part of the Dinant an d Namur Basins. As a consequence of the northward shifting Variscan fo ld belt, the Upper Carboniferous succession in the southern part of th e Dinant Basin and in the Rocroi area was reduced or absent. Conodont CAIs together with other thermal alteration data from the Condroz Mass if indicate that this area was a structural ''high'' for most of the D evonian. The Brabant Massif was probably covered with approximately 1. 5-2.0 km of Upper Carboniferous sediments in the south and less than 1 .0 km in the central and northern parts. In the central Campine Basin Visean strata could have been buried by 3.5-4.5 km of Upper Carbonifer ous rocks.