‘Cold spots’ during the Cenozoic evolution of the Eastern Alps: thermochronological interpretation of apatite fission-track data

Abstract

The tectonical and morphological evolution of the Eastern Alps during the Cenozoic is discussed in the light of sedimentary record and thermochronological data of crystalline basement rocks. The regional distribution of apatite fission-track data in the central Eastern Alps reveals the differential Cenozoic exhumation. In contrast to the Penninic of 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 must 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 Pöls Line and the area of the northern Koralpe cooled to below 100°C at the end of the Cretaceous 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 under the term ‘cold spots’. A major post-Cretaceous thickening of the Austroalpine 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 planation surfaces in the crystalline basement at the western border of the Styrian Basin (Koralpe) probably developed in the Late Miocene.