UPPER ORDOVICIAN LITHOSTRATIGRAPHY AND STRUCTURAL ARCHITECTURE OF THE FAUQUEZ AREA (BRABANT MASSIF, BELGIUM)
Universiteit Gent, Vakgroep Geologie en Bodemkunde, Onderzoekseenheid Paleontologie, Krijgslaan 281, B-9000 Gent, Belgium, E-mail: Jacques.Verniers@Ugent.be.
Universiteit Gent, Vakgroep Geologie en Bodemkunde, Onderzoekseenheid Paleontologie, Krijgslaan 281, B-9000 Gent, Belgium.
Universiteit Gent, Vakgroep Geologie en Bodemkunde, Onderzoekseenheid Paleontologie, Krijgslaan 281, B-9000 Gent, Belgium and Katholieke Universiteit Leuven, Structural Geology & Tectonics Group, Redingenstraat 16, B-3000 Leuven, Belgium.
Abstract
The Fauquez area along the Sennette Valley in the Brabant Massif is known for its Upper Ordovician graptolite and shelly macrofossil bearing sediments. Renewed fieldwork and a detailed overview of the geological studies in the area allowed the proposition of a new lithostratigraphy of the Upper Ordovician rocks with a detailed description of four formations (Bornival, Huet, Fauquez and Madot), the construction of a detailed lithostratigraphical column, a geological section and a geological map. On the basis of a detailed structural analysis, we interpret the Fauquez area as a large-scale, non-cylindrical antiform, being cogenetic with cleavage development, which is cut by relatively important post-cleavage normal faults. The antiform and cleavage development are attributed to the Brabantian deformation phase. The non-cylindrical shape of the large-scale antiform, as well as the non-cylindrical nature of many of the smaller, parasitic folds, is compatible with a local, syn-cleavage and syn-folding dextral shear. Possibly, this local dextral shear is a result of the unequal distribution of the more competent volcanic bodies of the Madot Formation, being significantly thicker in the western part of the area. In contrast to previous views, there is no evidence for important reverse faulting.