A NEW STRATIGRAPHICAL INTERPRETATION OF THE MESOZOIC COVER OF THE TAMBO AND SURETTA NAPPES - EVIDENCE FOR EARLY THIN-SKINNED TECTONICS (SWISS CENTRAL ALPS)

The sedimentary cover of the Tambo and Suretta crystalline nappes (Mid Penninic, Eastern Switzerland), hitherto regarded as only Triassic, i s similar to the reduced Mesozoic series of the internal Brianconnais (Acceglio zone) of the French-Italian Alps. This series, which include s an unconformable thick member of polygenic breccias considered to be mainly late Cretaceous, must be divided into (1) a reduced autochthon ous cover overlain by (2) a more complete allochthonous cover, the ''S tarlera Nappe''. An early phase of thin-skinned thrusting accounts for the emplacement of this new unit of more internal origin.