Environmental conditions during the late Oligocene transgression in the North Alpine Foreland Basin (Eferding Formation, Egerian) – A multidisciplinary approach

The North Alpine Foreland Basin (NAFB) comprises one of the most complete sedimentary records of the
Oligocene and Miocene, driven by global sea-level fluctuations, vast sedimentary influx and tectonic movement.
The locality of Unterrudling near Eferding (Upper Austria) exposes the largest succession of sedimentary deposits
from the late Oligocene in the eastern NAFB. Additionally, this section shows the facies transition from the
shallow-water Linz-Melk Formation to the deep-water Eferding Formation. In this work, the fossil fauna and flora
of the Eferding Formation as well as its lithology are re-evaluated using a multidisciplinary approach to gain new
insights into the palaeoenvironment, palaeoclimate, and palaeoecology. A transgressive sequence is documented
using sedimentological and ichnological data. Furthermore, a correlation to the late Chattian transgressive Ch-3
sequence is suggested. The impact of rising sea-level on marine biota is shown in detail by analysing various
groups (Bivalvia, Echinodermata, Anthozoa, Foraminifera, Chondrichthyes and Osteichthyes), with several
newly reported species for the Eferding Formation. Moreover, washed in plant material was analysed for the
interpretation of the terrestrial climate indicating mainly humid subtropical conditions. Finally, the presence of
phosphatic nodules indicates eutrophication on the shelf environment and the possibility of upwelling currents.