Speleothems and mountain uplift

Abstract

Ancient speleothems were recovered from caves that today are situated in a high-alpine cirque landscape at 2500 m altitude at the northern rim of the European Alps. U-Pb ages date speleothem deposition to the early Quaternary (between 2.16 and 2.12 Ma and ca. 2.00 Ma), i.e., well before the onset of major alpine and Northern Hemisphere glaciations. Using a stable isotope–based modeling approach, we quantitatively estimate the paleoelevation of both the caves and their former catchment area, which in turn allows us to calculate rates of rock and surface uplift (and hence erosion) since 2 Ma. We show that for the frontal part of the Alps, rates of rock uplift and erosion were ∼0.75 and ∼0.5 mm/yr, respectively, and further suggest that isostatic uplift of mountain peaks of as much as ∼500 m in response to enhanced glacial erosion occurred during the Quaternary. This study highlights the potential of U-Pb-dated speleothems for reconstructing paleoaltimetry, particularly in calcareous mountain ranges, where a standard thermochronologic assessment of exhumation and erosion is generally not feasible.