Mesozoic and Early Tertiary evolution of the Alpine foreland in upper Austria and Salzburg, Austria

Abstract

The Cenozoic Molasse Basin of Upper Austria and Salzburg is part of the Alpine foredeep. Its substratum is formed by the crystalline basement of the Bohemian Massif and its Mesozoic sedimentary cover. This autochthonous complex extends for a considerable but unquantifiable distance beneath the Alpine nappes.The area occupied by Upper Austria and Salzburg started to subside during the Middle Jurassic, and by Late Jurassic time it was covered by an extensive carbonate platform. Early Cretaceous wrench deformations, related to rifting activity in northwestern Europe, were accompanied by a major erosional phase. During the Late Cretaceous, 750 to 1000 m of shallow marine shales and elastics accumulated in the area, whereby the clastic influx from the Bohemian Massif increased during the Late Senonian. At the transition from the Cretaceous to the Tertiary, dextral transpressional deformation induced partial basin inversion. This deformation phase may be related to the collision of the North European craton with the Alpine orogenic system.Following an erosional phase during the Palaeocene and Early Eocene the area subsided again and became part of the Alpine foredeep.