Late Miocene intensification of continentality in the Black Sea region

Abstract

The Black Sea basin is the sink for some of the largest European rivers and has acted as such, since it was part of the Eastern Paratethys. The late Miocene-to-Pliocene sedimentary record of the Black Sea documents several phases of strongly evaporitic conditions associated with extreme changes in regional hydrology. Here, we present the first combined record of continental temperature, soil type, and biomass burning in the circum–Black Sea region from the late Miocene to the transition into Pliocene (~ 10.0 to 5.0 Ma). We use branched glycerol dialkyl glycerol tetraethers (brGDGT) to reconstruct mean annual air temperature (MAT) and soil pH within the catchment of the Black Sea basin and complement these data with evidence from charcoal morphology as a proxy for burned biomass. The brGDGT data reveal generally decreasing temperatures and acidic soils between ~ 10 and 8.5 Ma, overlapping with increase in herbaceous cover in the Black Sea region. The Pontian flooding at 6.12 Ma is characterized by large quantities of organic debris and charcoal fragments in the basin and is followed by cooling starting at 5.97 Ma, event that is superimposed on the TG 20 and TG 22 glacial peaks (at 5.8 Ma). Between 5.8 and 5.0 Ma, the brGDGTs seem to be primarily derived from a cold steppe environment. Enhanced fire activity coinciding with generally cooler temperatures and a higher proportion of herbaceous plants are indicative of increased continentality between 5.8 and 5.0 Ma in the Black Sea region.