Ichnocenoses du grès armoricain (ordovicien inférieur du massif armoricain) dans leur contexte sédimentologique

Several lithofacies are identified in the Grès armoricain Formation (Lower Ordovician of the Armorican Massif, France). Two of them are studied: the Skolithos quartzarenite lithofacies (with Daedalus halli and Diplocraterion) and the Cruziana heterolithic lithofacies (with Phycodes and Daedalus labechei). The relationship between Skolithos, Tigillites and Monocraterion is discussed. Skolithos is interpreted as a response to sediment influx. The whole physical and biogenic sedimentary structures suggest that the Grès armoricain was deposited under a tidal influence in a flat environment.