Accelerated erosion of the Eastern European Alps since ~ 3 Ma: a response to climatic cooling?

Global cooling and repeated glaciations during the late Cenozoic are inferred to have altered the topography of many mountain belts by enhancing the rates of erosion and valley incision. However, quantifying these changes in erosion rate and local relief has proven challenging. In this study, we use apatite (U-Th)/He (AHe) and apatite fission track (AFT) dating to constrain the erosion history of the Ötztal-Stubai Complex—a deeply incised basement complex in the European Alps, which remained undeformed during the late stages of the Alpine orogeny. The mean AHe ages (~ 3–15 Ma) and AFT ages (~ 10–20 Ma) increase with altitude and indicate continuous cooling and exhumation. Thermo-kinematic inverse and forward modeling shows that the age data can be explained by an increase in erosion and exhumation rate (from ~ 0.2 to ~ 0.4 km/Myr) since the late Pliocene (3.1 ± 0.8 Ma) and a concomitant deepening of the main valleys by 300–600 m. The exhumation during the Miocene and Pliocene is interpreted to reflect the erosion of thickened crust after the main phase of mountain building, whereas the onset of enhanced erosion and valley incision is attributed to repeated glacial–interglacial cycles, which caused erosion to become more efficient in the high internal parts of the mountain belt.