Opportunities and Challenges for Paleoaltimetry in “Small” Orogens: Insights From the European Alps

S Botsyun,E Krsnik,S G Mutz,A Mulch,K Methner,T A Ehlers

doi:10.1029/2019gl086046

Abstract

AbstractMany stable isotope paleoaltimetry studies have focused on paleoelevation reconstructions of orogenic plateaus such as the Tibetan or Andean Plateaus. We address the opportunities and challenges of applying stable isotope paleoaltimetry to “smaller” orogens. We do this using a high‐resolution isotope tracking general circulation model (ECHAM5‐wiso) and explore the precipitation δ18O (δ18Op) signal of Cenozoic paleoclimate and topographic change in the European Alps. Results predict a maximum δ18Op change of 4–5‰ (relative to present day) during topographic development of the Alps. This signal of topographic change has the same magnitude as changes in δ18Op values resulting from Pliocene and Last Glacial Maximum global climatic change. Despite the similar magnitude of the isotopic signals resulting from topographic and paleoclimate changes, their spatial patterns across central Europe differ. Our results suggest that an integration of paleoclimate modeling, multiproxy approaches, and low‐elevation reference proxy records distal from an orogen improve topographic reconstructions.

Highlights

Quantifying the elevation history of orogens is essential for understanding the subsurface density structure of orogens, their isostatic compensation, and interactions among climate, tectonics, and surface processes (e.g., Clark, 2007; Molnar et al, 2010)
Over the Alps, δ18Op values show a clear decrease from the foothills to the top (e.g., −0.24‰/100 m in the Northern Alps for JJA) that is consistent with the modern observed isotopic lapse rate (−0.21‰/100 m in the Northern Alps and −0.19‰/100 m in the southern Alps; Campani et al, 2012)
The results of our experiments with varied alpine elevations suggest that surface uplift of the Alps affects δ18Op values by about 4–5‰ within the high‐Alpine region

Summary

Introduction

Quantifying the elevation history of orogens is essential for understanding the subsurface density structure of orogens, their isostatic compensation, and interactions among climate, tectonics, and surface processes (e.g., Clark, 2007; Molnar et al, 2010). Among the methods developed to establish the elevation history of orogens including orogenic plateaus and their margins, stable isotope paleoaltimetry is the most widely used. Despite extensive application, this method has several uncertainties due to the sensitivity of both δ18Op values and the δ18Op‐elevation gradient (isotopic lapse rate (ILR)) to regional and global climate change and topographic changes that can deflect air masses, induce adiabatic and nonadiabatic temperature changes, relative humidity variations, thereby changing continental evapotranspiration and vapor recycling (Botsyun et al, 2016, 2019; Ehlers & Poulsen, 2009; Insel et al, 2012; Mulch, 2016; Poulsen et al, 2010)

Methods

Results

Conclusion