Depositional evolution of the Valjevo-Mionica Basin (Internal Dinarides, Serbia) revealed through U-Pb zircon dating: correlation with regional tectonics and Miocene climate change

Intramountain basins serve as records of paleoclimatic, paleobiogeographic and tectonic histories of past continental environments. This offers a crucial glimpse into the evolution orogens during and after the main mountain-building phase, and their effect on modifying local climatic and environmental conditions. In this work, we test the hypothesis that the Dinarides significantly influenced the development of a rain shadow, leaving the range's eastern flank (Internal Dinarides) dry during the Miocene Climatic Optimum. We do so by looking at the lacustrine successions of the Serbian Lake System (SLS), stretching across the eastern flank of the mountain range. We conducted outcrop and core logging in the Valjevo-Mionica Basin (VMB, western Serbia), as well as LA-ICP-MS U-Pb dating of intercalated tuff layers, to assess the effects of global vs regional climate change on basin development and the correlation with regional tectonic events. The basin fill consists of polymict conglomerates and sandstones in the lower part, followed by laminated marls with microbial mat intercalations and tufa deposits. In the middle part, laminated to massive marls predominate. The upper part comprises dolomitic marlstones with evaporitic minerals (notably searlesite and analcime), and sandstone intercalations, pointing to an arid climate. Radiometric dating of intercalated volcanic ash horizons implies lacustrine conditions developing after ~14.5 Ma and persisting until the Sarmatian, correlating with the global cooling trend of the Middle Miocene climatic transition (MMCT) and opening of the neighbouring Pannonian Basin. In contrast to several other intramountain basins in the region, our new data from the VMB suggest the arid phase in the Internal Dinarides was likely induced by the MMCT, post-dating the MCO. Considering published sedimentological, radiometric and paleontological datasets, this study implies that a prolonged arid phase affected the Internal Dinarides during MCO and MMCT. During the MCO, the arid phase was likely caused by tectonic influences on the local climate. Later, the MMCT helped maintain the arid environment.