Sedimentology, coalification pattern and paleogeography of the Campine- Brabant Basin during the Visean

Abstract

During the Visean, four major lithological and biostratigraphical sequences formed in the Campine-Brabant Basin, north of the London-Brabant Massif. The Visean strata are mainly composed of carbonates. The first sequence was formed during the Early Moliniacian. At this time, the Heibaart area was a structural high. During the late Moliniacian, when the second sequence was formed, the whole Campine-Brabant Basin was characterized by carbonate sedimentation on a broad shallow shelf. The third sequence formed during the Livean. Sedimentation was restricted in the Turnhout and Halen area. In the Heibaart area, sediments were deposited in an environment with open water circulation. During the Early Warnantian the fourth sequence was formed. Reef mounds developed in the Poederlee-Heibaart area and probably also in the Turnhout area. The sediments penetrated by the Halen borehole were deposited alternately in an open and in a restricted environment. The thickness variations of the different sequences and the facies distribution indicate that synsedimentary faults were active in the Campine-Brabant Basin during the Visean. A comparison with the Upper Westphalian of the Campine-Brabant Basin, and with the Lower Carboniferous of northern England suggests a block-faulted structural framework for the Campine-Brabant Basin during the Visean. The paleogeothermal gradient of the Visean and the Namurian-Westphalian A strata of the western zone of the Campine-Brabant Basin has been calculated. The coalification data at the top of the Visean confirm the existence of a fault zone near the London-Brabant Massif and of a shelf bordered to the north by a listric fault.