Control of inherited structures on deformation and surface uplift: Crustal-scale analogue modelling with implications for the European eastern Southern Alps

Abstract

We use crustal-scale physical analogue modelling to investigate the effect of mechanical and structural inheritance on the surface uplift of fold-and-thrust belts. Our study includes inversion of a pre-defined basin and platform structure of varying geometry and strength as well as that of a structurally controlled heterogeneity at the model-base. Our experiments represent multiply deformed continental crust, as it is the case for the eastern Southern Alps (ESA) of Europe, where lateral strength variations stem from Permian volcanic and plutonic rocks located within the northern Trento platform. Basal structural heterogeneity in the models represents Permian paleo-faults bordering volcanic rocks, reactivated under various tectonic regimes up to the present-day. Crustal composition and structure variations are embedded in a structural frame of an extensional platform and basin differentiation related to Triassic/Jurassic extension. We present a novel approach of comparing model surface uplift patterns with exhumation data from regional thermochronological studies of the ESA, enabling interpretations of first-order tectonic processes governing specific exhumation patterns. Modelling results demonstrate that pre-defined structures control timing and patterns of uplift of the evolving fold-and-thrust belt and stronger crustal domains and/or basement heterogeneities localise deformation. Besides prevalent in-sequence deformation, out-of-sequence reactivation of specific faults is coeval with slip on multiple faults, influencing spatial and temporal surface uplift. Two distinct end-members of surface uplift patterns emerge: “differential” versus “continuous”. Inherited basement structures control strain localisation and promote “differential” surface uplift, where the rear of the fold-and-thrust belt experiences little surface uplift and uplift is mainly focused above the inherited basement structure, consistent with documented plateaus in low-temperature thermochronology data of the western ESA north of the Valsugana fault system between Jurassic and Neogene times. Contrarily, experiments featuring relative stronger upper crustal domains show “continuous” surface uplift, correlating with continuous exhumation over the last ∼15 Ma according to geochronology data.