Interplay between the thermal evolution of an orogenic wedge and its retro-wedge basin: An example from the Ukrainian Carpathians

The Carpathian-Pannonian region is made up of the wide extensional Pannonian Basin surrounded by the Carpathian mountain belt. The Pannonian Basin formed in the Miocene by extension in a retro-wedge position while thrusting was still active at the Carpathian front. The Ukrainian region is an ideal area to reconstruct the relationship between the Pannonian Basin and the Carpathians, due to the relatively simple structural setting and to the progressive but neat transition between the two domains. This study uses low-temperature thermochronometry and vitrinite reflectance analysis to investigate the effect of the opening of the Pannonian Basin on the thermal and burial-exhumation histories of the Ukrainian Carpathians. The results show heating and burial maxima in the central units of the wedge (up to ~170 °C and 6 km, respectively), tapering out toward both the innermost and the outermost thrust sheets. Cooling and exhumation occurred by means of a first rapid stage between ca. 12 and 5 Ma (exhumation rates of up to ~1 mm/yr), followed by a slower stage from ca. 5 Ma to the present (exhumation rates within 0.5 mm/yr). Timing and spatial pattern of exhumation are compatible with post-thrusting erosion enhanced by isostatic uplift. The extent of exhumation progressively decreases toward the Pannonian Basin, characterized by a thinned crust. No further significant influence of the Pannonian Basin opening on the thermal and burial history of the Ukrainian Carpathians may be inferred based on our results, whereas the comparison of the tectonothermal evolution of the two domains suggests that they are both controlled by the same lithospheric processes.