Paleogeographic and climatic evolution of the Moliniacian (lower Visean) in southeastern Belgium

Abstract

A detailed biostratigraphical subdivision of the lower Visean (Moliniacian) in southeastern Belgium is not possible. Therefore correlations are based on the facies evolution. Based on these correlations, the paleogeographical evolution during the early Visean can be reconstructed. During the early Moliniacian, open marine subtidal limestones were deposited. Near the coast, these sediments were subsequently dolomitized and intense karstification took place under humid conditions. Basinwards, algal laminites formed in the intertidal zone. The continental interval was followed by open marine sedimentation above wave base. At the end of the early Moliniacian, beginning of the middle Moliniacian, the depositional environment became shallower. A second continental interval occurred near the Brabant Massif and a sabkha developed further to the south (i.e. basinwards) in a semi-arid to arid climate. The subsequent transgressive trend was very gradual. Middle Moliniacian sedimentation occurred in an evaporitic lagoonal and intertidal setting. The peritidal sediments contain numerous paleosol horizons, which formed under semi-arid conditions. Upper Moliniacian limestones, were deposited on a shallow open marine shelf. The paleolatitudinal position of Euramerica during the early Visean was close to the equator and normally a humid climate must have been present. The recognized semi-arid intervals are due to the large Gondwana landmass situated south of the equator, deflecting rains away from Euramerica.