Evoluzione stratigrafica pre-hirnantiana della Formazione di Kermeur (Massiccio Armoricano)

The stacking pattern of sedimentary facies has been investigated at the base of the Boda event (Katian) in the Armorican Massif, belonging to the North Gondwana platform. A sedimentary facies analysis carried out on the Aber-Kerglintin section leads to the definition of seven sedimentary facies ranging from open to restricted sea environments. Through geological, stratigraphical and depositional features, several sequences are identified and interpreted in cycles of different frequency orders. In the section, three sequences of 3 rd order are identified, with four principal MFS, related to most distal facies overlaid by condensation horizons (i.e. phosphatic levels and shellbeds). These results allow us to estimate the time slice for the deposits of the whole section of about 6 My. This duration is in agreement with the biostratigraphical data obtained by chitinozoans.