Age, Kinematic and Thermal Constraints of Syn-Orogenic Low-Temperature Deformation Events: Insights From Thermochronology and Structural Data of the Nekézseny Thrust (Alpine-Carpathian-Dinaric Area)

Abstract

Unraveling the age and kinematics of low temperature deformation events is crucial in understanding the late-stage evolution of orogens. However, accurate age constraints can often be challenging to obtain due to unideal outcrop conditions, large sedimentary hiatuses or the lack of well-defined thermal events. In this study, we show on the example of the Nekézseny Thrust, a poorly exposed late orogenic thrust in the southern Western Carpathians, that a combined approach of structural analysis and multi-method thermochronology can provide the necessary temporal, kinematic and thermal constraints for a detailed reconstruction of the deformation history. While structural mapping revealed that the Late Cretaceous Uppony Gosau Basin in the footwall of the Nekézseny Thrust underwent a significant post-Campanian and pre-Miocene shortening, K/Ar dating of fault gouge samples from the main fault zone constrained the primary thrusting event to the Maastrichtian. Based on the acquired apatite fission-track and (U-Th)/He ages, subsequent heating of the Upper Cretaceous sediments due to tectonic burial was limited to 75–100°C, followed by deformation-related and gradual cooling between the Eocene and Early Miocene. Considering the reconstructed deformation history, as well as the large-scale tectonic affinity of the displaced units in its footwall and hanging wall, the Nekézseny Thrust is a far-traveled (ca. 600 km) segment of the Late Cretaceous Alps-Dinarides contact zone, whose development was linked to the switch from lower plate to upper plate position with respect to the Sava Zone and Alpine Tethys sutures, respectively.