Chitinozoan Biozonation and New Lithostratigraphical Data in the Upper Ordovician of the Fauquez and Asquemont Areas (Brabant Massif, Belgium)

A chitinozoan biozonation is established for the Upper Ordovician rocks of the Sennette valley in the Fauquez area and the Asquemont area, revising the existing chitinozoan biozonation of the Brabant Massif. The chitinozoans of five formations (the Ittre, Bornival, Huet, Fauquez, and Madot formations) are studied from 70 samples. The chitinozoan biozonation is correlated with Baltoscandia and the Avalonian Upper Ordovician type sections in the U.K. This correlation provides an accurate dating of the studied formations. A megasumping event, affecting a part of the Ittre and Bornival formations and causing the overturning of a pile of sediments estimated at minimum 200 m thick, may be placed in the mid Oandu (Cheneyan, middle Caradoc, early "Stage 6"). The volcanic rocks in the Fauquez area, formally thought to be restricted to the Ashgill, are confined to the late Caradoc - early Ashgill timespan. In addition to this, this paper presents new lithostratigraphical data on the Ittre Formation and the lower member of the Bornival Formation.