Palaeontological evidence of communication between the Central Paratethys and the Mediterranean in the late Badenian/early Serravalian

In the Middle Miocene the area of present-day eastern Slovenia was situated at the eastern mouth of the Slovenian Corridor - a hypothetical seaway connecting the Central Paratethys and the Mediterranean. The exact location and time of closure of a seaway between the two neighbouring marine realms are still a matter of debate. We studied Badenian (late Langhian and early Serravallian) calcareous nannoplankton assemblages from eastern Slovenia for their palaeogeographical significance by comparing them to contemporaneous Central Paratethyan and Mediterranean assemblages and the assemblages described in selected ODP and IODP reports. Assemblage composition and the sequence of biostratigraphic events observed in Slovenia were very similar to that in several Mediterranean sites. Comparison with the World Ocean suggests that this similarity reflects communication between the Mediterranean and Paratethyan populations rather than a universal trend of nannoplankton evolution. Late Badenian assemblages from different localities within the Central Paratethys exhibit considerable variation with respect to the presence of discoasters (considered as typical of the Mediterranean) and the presence of Rhabdosphaera poculi and Hayella challengeri (considered as typical of the Eastern Paratethys). Our results suggest the mixing of Mediterranean and Eastern Paratethyan influences throughout the entire Central Paratethys during the late Badenian. The observed variability explains how opposing views on the status of the marine connection between the Central Paratethys and the Mediterranean in the late Badenian can arise from palaeontological studies of fossil assemblages considering only a single site or a small area. The gastropod species Pereiraea gervaisi migrated from the Mediterranean to the Central Paratethys - where it is only known from the immediate proximity of the hypothesised Slovenian Corridor. This supports the thesis that the communication between the two seas took place via the Slovenian Corridor and not some other marine connection like the hypothetical Axios (Vardar) Trench. (C) 2013 Elsevier B.V. All rights reserved.