Thermochronological markers reveal Late Cretaceous strike-slip faulting in the Yangtze Block, South China

Detecting strike-slip tectonics using thermochronology is challenging because the complex relative motion between fault blocks often does not substantially displace the vertical stratigraphy provided by thermochronological ages. Here we investigate the strike-slip tectonics in the Yangtze Block, South China, based on an original conceptual model and the zircon (U-Th)/He (ZHe) analysis of 17 sandstone samples. We exploit as a marker the northwestward trend of progressively decreasing ZHe ages generated by Mesozoic northwestward shortening. The ZHe age trend is broken by evident steps, which are also found in other published thermochronological datasets. We interpret these age steps as marking a previously undetected Late Cretaceous left-lateral strike-slip fault which intersects with prior deformation-propagation direction. Our approach to detect strike-slip faults confirms a major change in the subduction direction of the Paleo-Pacific Plate beneath Eurasia during the Late Cretaceous, and can find applications to other regions where thermochronological ages define suitable dipping markers.