Late early Miocene lake deposits near Mauensee, central Switzerland: Fish fauna (otoliths, teeth), accompanying biota and palaeoecology

Abstract

The Mauensee section in the Molasse Basin of central Switzerland exposes a 3.7 m thick lacustrine sequence intercalated in marine siliciclastic deposits of the Upper Marine Molasse. From this sequence, which is Karpatian in age, a teleost fish fauna (otoliths, teeth) is described that consists of 15 species, including Cyprinidae, Mugilidae, Atherinidae, Cyprinodontidae, Gobiidae, and Channidae. In addition, charophytes, vascular plant remains, bivalves, gastropods, ostracods, amphibia, reptilia, and mammals are recorded. Palaeoecological analyses indicate that the fishes lived in a large, oligohaline, warm, and oligo- to mesotrophic lake with a water depth of five metres or more. Sedimentation rate estimates suggest that the lake existed for approximately 18.000 to 20.000 years. A remarkable enrichment of otoliths and teeth in the uppermost part of the lacustrine sequence is indicative of increased fish mortality, due perhaps to decreasing water-levels and seasonal occurrences of anoxic conditions. The persistence of a large lake in the Molasse Basin of central Switzerland during the Karpatian was certainly favoured by low sedimentation rates during this period of time.