Miocene high elevation in the Central Alps

Reconstructing Oligocene–Miocene paleoeleva- tion contributes to our understanding of the evolutionary his- tory of the European Alps and sheds light on geodynamic and Earth surface processes involved in the development of Alpine topography. Despite being one of the most intensively explored mountain ranges worldwide, constraints on the el- evation history of the European Alps remain scarce. Here we present stable and clumped isotope measurements to pro- vide a new paleoelevation estimate for the mid-Miocene (⇠ 14.5 Ma) European Central Alps. We apply stable isotope – paleoaltimetry to near-sea-level pedogenic carbonate oxy- gen isotope ( 18O) records from the Northern Alpine Fore- land Basin (Swiss Molasse Basin) and high-Alpine phyllosil- icate hydrogen isotope ( D) records from the Simplon Fault Zone (Swiss Alps). We further explore Miocene paleoclimate and paleoenvironmental conditions in the Swiss Molasse Basin through carbonate stable ( 18O, 13C) and clumped (147) isotope data from three foreland basin sections in dif- ferent alluvial megafan settings (proximal, mid-fan, and dis- tal). Combined pedogenic carbonate 18O values and 147 temperatures (30 ± 5 C) yield a near-sea-level precipitation 18Ow value of 5.8 ± 1.2 ‰ and, in conjunction with the high-Alpine phyllosilicate D value of 14.6 ± 0.3 ‰, sug- gest that the region surrounding the Simplon Fault Zone at- tained surface elevations of > 4000 m no later than the mid- Miocene. Our near-sea-level 18Ow estimate is supported by paleoclimate (iGCM ECHAM5-wiso) modeled 18O values, which vary between 4.2 ‰ and 7.6 ‰ for the Northern Alpine Foreland Basin