The influence of climate on the dynamics of mountain building within the Northern Patagonian Andes

Abstract

Theoretical studies support the idea that the internal dynamics of actively deforming mountain ranges are influenced by spatial and temporal variations in climate. The identification of plausible correlations between orogen behaviour and external climatic processes requires, among other factors, that the initiation and duration of any deformation event be precisely constrained. Here we add new detrital zircon U‐Pb ages and Be surface exposure dating to the already extensive dataset for the low‐temperature cooling history, to analyze the spatial patterns of deformation, and their temporal variations across the foreland of North Patagonia, with the aim of evaluating potential feedbacks between climate and deformation. Stratal relationships, together with geomorphic evidences of deformation document the precise timing of individual structures within the fold‐thrust belt and the broken foreland. Our data record a progressive decrease of upper‐plate shortening rates and subsidence after a first period of widespread deformation and uplift (ca. 13 - 7 Ma). This ?transitional? foreland phase coeval to the onset of glacial conditions at 7.4 ‐ 5 Ma is followed by astructural reorganization after ca. 3 Ma, marked by the abandonment of the foreland and enhanced slip on interior faults, with the intensification of glacial erosion at this time. We propose that acceleration in erosion rates during the past 7 Ma may have influenced the regional geometry and kinematic history of the orogenic belt. Our empirical results match theoretical predictions and provide compelling evidence at the scale of individual thrust faults for the significant impact of climate change on orogenic behaviour.