Les abrupts asymétriques du Massif armoricain. 2e série : les abrupts de l'ellipse de Réminiac

Abstract

In the south eastern center of Brittany, between the Landes de Lanvaux heights and the appalachian region of the middle course of the Vilaine, the ellipse of Reminiac, formed by two synclines of primitive terranes, provides the example of two asymetrical scarps. The first one is located on the northern flank of the ellipse ; it rises above the stream Oyon, north of which one finds the syncline of Coëtquidan. If the Oyon Valley may, with some evidence, appear as a depressed area of selective erosion, one supplies numerous arguments, both geological and morphological, to retain the assumption of a partially tectonic origin of the relief : the synclines of Coëtquidan and of the Corbinais, situated respectively north and south of the Oyon are southward silted blocks. Between the two synclines of the ellipse, the course of the stream Vaupayen is situated similary to that of the Oyon. One can show that the southern side of the dissymetrical depression — a gentle northern slope and abrupt southern slopes which il runs through, — is a fault zone.