Tidal sediments in the Upper Marine Molasse (OMM) of the Allgau area (Lower Miocene, Southwest-Germany)

Abstract

, B. (2009): Tidal sediments in the Upper MarineMolasse (OMM) of the Allgau area (Lower Miocene, Southwest-Germany). – N. Jb. Geol. Palaont.Abh., 254 : 151–163; Stuttgart.Abstract: Evidence for tidal influences in the Upper Marine Molasse (OMM) of the Allgau area(Southwest German part of the Molasse Basin) is presented. The studied sections in the “EllhoferTobel” ravine reveal an approximately 140 m thick succession of marine sediments. Four differentfacies types are distinguished in this succession: 1) a Glauconitic Sandstone Facies, 2) a HeterolithicFacies, 3) a Cross-Stratified Sandstone Facies and 4) a Conglomeratic Facies. These lithofaciesrepresent different near coastal and shallow marine environments. A tidal influence is indicated bythe presence of the Heterolithic Facies which contains associated epsilon cross-stratification andmegaripples (or subaquatic dunes). A general current direction from south to north is consistentdocumented by subaquatic dune foresets and the orientation of ripple foresets. If the coastalenvironment near the southern coast of the Molasse Sea had a rather simple tidal current regime thisdominant northerly current direction could be interpreted as ebb currents. Keywords: Early Miocene, Molasse Basin, Allgau, Upper Marine Molasse (OMM), tidal sediments.