Miocene high elevation in the Central Alps

Abstract

Reconstructing Oligocene-Miocene paleoelevation contributes to our understanding of the evolutionary history 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 elevation history of the European Alps remain scarce. Here we present stable and clumped isotope measurements to provide a new paleoelevation estimate for the mid-Miocene (g1/414.5gMa) European Central Alps. We apply stable isotope paleoaltimetry to near-sea-level pedogenic carbonate oxygen isotope (18O) records from the Northern Alpine Foreland Basin (Swiss Molasse Basin) and high-Alpine phyllosilicate 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 ("47) isotope data from three foreland basin sections in different alluvial megafan settings (proximal, mid-fan, and distal). Combined pedogenic carbonate 18O values and "47 temperatures (30±5ggC) yield a near-sea-level precipitation 18Ow value of -5.8±1.2g‰ and, in conjunction with the high-Alpine phyllosilicate D value of -14.6±0.3g‰, suggest that the region surrounding the Simplon Fault Zone attained surface elevations of >4000gm 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 -4.2g‰ and -7.6g‰ for the Northern Alpine Foreland Basin.