WESTERN END OF THE BRECCIA NAPPE IN THE C HABLAIS AREA (HTE-SAVOIE, FRANCE) - SEDIMENTOLOGY, STRATIGRAPHIC ELEMENTS AND PALEOGEOGRAPHIC INTERPRETATION

Two areas from the western end of the Breccia nappe are studied here: the first at the Praz-de-Lys (Taninges) and the second at the Col de J oux Plane (Morzine). Sedimentological and stratigraphical analysis ind icates the existence of marginal or proximal deposits (Praz-de-Lys are a) and, clearly distinct, basinal or distal deposits (Col de Joux Plan e area). Proximal continental slope deposits begin with Piemont or Aus tro-alpine type dolomites, dated from the Carnian-Norian: the Chalune Formation. The overlying Lower Breccia Formation (= Breccia inferieure ) (Lias-Dogger) consists of large breccias containing carbonates deriv ed from the Brianconnais, alternating with turbidites. This formation constitutes a sedimentary prism. In the basinal deposits, the Lower Sh ale Formation (= Schistes inferieurs) is a lateral equivalent of the b asal part of the Lower Breccia Formation. It grades to an alternation of breccias and turbidites, rich in crinoidal fragments. Current beddi ng and grainsize analysis reveal several supply areas, from the west t o the north. Upper Shale Formation (= Schistes ardoisiers) (Callovian- Oxfordian?) shows rather uniform facies in both areas, including turbi dites, breccias and green or red siliceous shales. Upper Breccia Forma tion (= Breche superieure) (Kimmeridgian - Neocomian?) is made of calc ilutites and breccias. These breccias contain elements similar to thos e present in the Lower Breccia Formation and chloritic hercynian shale s and quartzites. Detailed sedimentological study indicates synrift de posits, most probably in a pull apart system, which evolved into a con tinental margin.