The Slanicul de Buzau section, a unit stratotype for the Romanian stage of the Dacian Basin (Plio-Pleistocene, Eastern Paratethys)

Abstract

Climatic changes cause large paleoenvironmental responses in semi-isolated basins. We analyze here the sedimentary successions of the Dacian Basin (Romania) to evaluate Late Pliocene and Early Pleistocene paleoenvironmental changes through macro- and micropaleontology. These changes are dated by creating a magnetostratigraphic time frame for two long and continuous sections with a combined total thickness of 2850m. The studied succession spans the time interval between 4.7Ma and 1.6Ma and records both the mid Pliocene Warm Period (3.3–2.9Ma) and the onset of large-scale glaciations on the Northern Hemisphere (~2.7Ma). Due to progressive basin infill, the paleoenvironment changes from brackish to fluvio-lacustrine with a major extinction event of lymnocardiine bivalves around 4.15Ma. Rich and dominantly freshwater mollusk and ostracod faunas develop from this moment onwards. Between 3.2Ma and 2.95Ma, the reappearance of lymnocardiines identifies a short moment of higher salinities, the previously identified Plescoi event. In time, this correlates closely to the warmest interval of the Pliocene, and is therefore most likely related to connectivity to the Black Sea during maximum sea-level. After the climatic optimum, deposition continues in a fluvio-deltaic setting with only scarce finds of fauna. Increasing amounts of coarse grained fluvial sediments show a close relationship with the progressive cooling during the Pleistocene.