Abstract
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 (∼14.5 Ma) European Central Alps. We apply stable isotope δ–δ paleoaltimetry to near-sea-level pedogenic carbonate oxygen isotope (δ18O) records from the Northern Alpine Foreland Basin (Swiss Molasse Basin) and high-Alpine phyllosilicate hydrogen isotope (δD) records from the Simplon Fault Zone (Swiss Alps). We further explore Miocene paleoclimate and paleoenvironmental conditions in the Swiss Molasse Basin through carbonate stable (δ18O, δ13C) and clumped (Δ47) isotope data from three foreland basin sections in different alluvial megafan settings (proximal, mid-fan, and distal). Combined pedogenic carbonate δ18O values and Δ47 temperatures (30±5 ∘C) yield a near-sea-level precipitation δ18Ow value of -5.8±1.2 ‰ and, in conjunction with the high-Alpine phyllosilicate δD value of -14.6±0.3 ‰, suggest that the region surrounding the Simplon Fault Zone attained surface elevations of >4000 m no later than the mid-Miocene. Our near-sea-level δ18Ow estimate is supported by paleoclimate (iGCM ECHAM5-wiso) modeled δ18O values, which vary between −4.2 ‰ and −7.6 ‰ for the Northern Alpine Foreland Basin.
Highlights
Past elevations of mountain ranges provide insight into the coupled climatic and geodynamic processes that shape orogenic belts
The topographic evolution of continent–continent collision zones such as the European Alps is mainly controlled by isostatic compensation for crustal and/or lithospheric deformation caused by plate convergence (e.g., Beaumont et al, 1996; Schmid et al, 1996; Willett et al, 1993)
We observe differences in δ18O values of pedogenic carbonate (δ18Oc) and δ13C values among the three foreland basin records, which we relate to their depositional setting within the megafans and the varying impact of soil water evaporation as well as soil productivity and interaction with atmospheric CO2 for δ18Oc and δ13C, respectively
Summary
Past elevations of mountain ranges provide insight into the coupled climatic and geodynamic processes that shape orogenic belts. The topographic evolution of continent–continent collision zones such as the European Alps is mainly controlled by isostatic compensation for crustal and/or lithospheric deformation caused by plate convergence (e.g., Beaumont et al, 1996; Schmid et al, 1996; Willett et al, 1993). Various mechanisms may have contributed to the increase in post-collisional Alpine surface elevation. These include horizontal shortening, thickening of the continental crust and following isostatic adjustment of the lithosphere (e.g., Pfiffner et al, 2002), mantle-scale uplift caused by slab break-off (e.g., Lippitsch, 2003), slab rollback and associated delamination within the lithosphere (Kissling and Schlunegger, 2018; Schlunegger and Kissling, 2015), and asthenospheric upwelling (e.g., Lyon-Caen and Molnar, 1989). Despite being a prime example of continent–continent collision following protracted convergence and subduction of oceanic lithosphere (e.g., Frisch, 1979; Froitzheim et al, 2008; Schmid et al, 1996; Stampfli et al, 1998), recent studies in the Euro-
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