Lay summary
The reconstruction of the first marine transgression onto the Vindelician High after the Hercynian orogeny in the Alpine region has fascinated geologists since the 18th century. Despite the numerous effords to refine the knowledge on the stratigraphic allocation, depositional environment and paleogeographic position, the lack of chronostratigraphic ages has thwarted a detailed reconstruction of the palaeorelief, the dynamics and the direction of the transgression during early Triassic times in Central Switzerland. Similarly, it has been unclear whether the basal Triassic in this part of the Alps is part of the Germanic Basin or belongs to the Tethys realm.The aim of this project is to reconstruct the depositional environments of the basal Triassic of Central Switzerland in a detailed chronological frame. This restoration is anticipated to yield information for calculations of transgression rates, palaeorelief and palaeotopography at Early Triassic times, and for assignments of predominant controls (i.e.eustatic versus tectonic processes in the Tethys or the Germanic Basin) on the Alpine realm during the transgression.The methods include a detailed analysis of the facies, depositional surfaces, sedimentary structures, micro- and biofacies. In addition, palynologic analyses will be carried out to determine the ages of deposition. This temporal framework will be the basis for further chemo- and sequence-stratigraphic analyses of the sections, which, in turn, will further improve the chronological resolution of the Triassic sequences.With this combination of chronological tools, it will become possible to propose a cyclostratigraphic interpretation, i.e., to attribute an exact duration for each order of depositional sequence.The importance of the project lies in a high-resolution reconstruction of the dynamics controlling the Triassic transgression onto the Vindelician High, which in turn will result in the estimation of the palaeotopography.This information is not yet available for this palaeosurface. If successful, our methodology can be applied to other cases where palaeosurfaces exist but where no information is available about paleorelief. Knowing the position relative to the Vindelician High will also give new insights on the evolution of the northern boundary of the Tethys ocean, specifically about the change from an epicontinental sea to a passive margin. These new insights will modify the paleogeographic picture during the Early Triassic in the Central Alps.