An Eocene paleodoline in the Morcles Nappe of Anzeindaz (Canton of Vaud, Switzerland)

Abstract

In the helvetic Morcles Nappe of Anzeindaz (Canton of Vaud, Switzerland), Eocene sediments document the successive bypassing of the forebulge and foreland basin of the Alpine orogeny. Cretaceous sediments are cut off by the major erosive unconformity of the so-called "siderolithic" emersion phase. This persistent phase of continental exposure and erosion caused by the presence of the forebulge during the Early to Middle Eocene removed the older sediment record down to the relatively resistant "Mid-Cretaceous" sediments. For the area under consideration, the continental erosion resulted in a peneplain which is perforated at two points by large paleodolines. The study of the sedimentary filling and fossil content of the better preserved one of these paleodolines allows for a reconstruction of the gradual transgression of the foreland basin over the study area. The origin of the paleodoline is interpreted as resulting from a combination of Eocene synorogenic tectonics, providing faults, and the subsequent attack of continental erosion alongside such weak zones.