Chitinozoan bio- and lithostratigraphical study of the Ashgill Fosses and Génicot Formations (Condroz Inlier, Belgium)

Ashgill chitinozoans from the Fosses and the Géniot Formations were studied in seven sections in the western part of the Condroz Inlier, Belgium. Twenty-three previously published samples as well as thirty-five new samples were analyzed. The combination of the results led to the definition of six local biozones and a local biozonation for the Ashgill of the region west of Fosses and eventually to the dating of both formations studied. Generally, the local biozonation allowed correlation of the sections. In combination with the detailed study of the lithostratigraphy, a hypothesis is proposed concerning the depositional history of both formations. Two conglomeratic levels in the Géniot Formation might be the sedimentological response to the sea level drop associated with the Hirnantian glaciation event. Two new species are defined: Spinachitina fossensis and Conochitina eustachensis.