COLD SPOTS DURING THE CENOZOIC EVOLUTION OF THE EASTERN ALPS - THERMOCHRONOLOGICAL INTERPRETATION OF APATITE FISSION-TRACK DATA

The tectonical and morphological evolution of the Eastern Alps during the Cenozoic is discussed in the light of sedimentary record and therm ochronological data of crystalline basement rocks. The regional distri bution of apatite fission-track data in the central Eastern Alps revea ls the differential Cenozoic exhumation. In contrast to the Penninic o f the Tauern Window, which has been strongly uplifted and eroded since the Early Miocene, the amount of Neogene denudation was much smaller in most areas east of the Hohe Tauern. A sudden change in the regional cooling behaviour is observed at the Katschberg fault system which mu st have been active in post-Oligocene times. Within the Austroalpine, only the Schladming Tauern have experienced a rather strong denudation . The Seckau Core Complex east of the Pals Line and the area of the no rthern Koralpe cooled to below 100 degrees C at the end of the Cretace ous and in the Early Eocene, respectively, and have never been heated again. During the Cenozoic, these parts of the Austroalpine nappe pile were always near to the surface and, therefore, may be summarized und er the term 'cold spots'. A major post-Cretaceous thickening of the Au stroalpine can be excluded, because it would have produced more uplift and erosion. Any remnants of Miocene or older landforms are certainly not preserved in the area of the Tauern Window. The uppermost planati on surfaces in the crystalline basement at the western border of the S tyrian Basin (Koralpe) probably developed in the Late Miocene.