Preliminary results from the endemic mollusc-bearing Brașov Basin (Pliocene, Transylvanian Lake System, Romania)

<p>The Pliocene Transylvanian Lake System (TLS) was formed between the various units of the Eastern Carpathians, and consists of three major intermontane (Bra&#537;ov, Ciuc, and Gheorgheni Basins) and some minor sub-basins containing a unique endemic-rich mollusc fauna.</p><p>The palaeogeographical connections of this system to the adjacent basins are still a matter of debate, but this area was probably not connected to the Pannonian, Transylvanian, or Dacian Basins in the latest Miocene-Pliocene. The area lacks numerical age data and a detailed stratigraphic age model; although, some attempts were made to correlate the sedimentary sequences within the TLS, but merely based on lithostratigraphy.</p><p>The last comprehensive monograph on this fauna was published by the Saxon palaeontologist, Erich Jekelius in 1932, therefore a taxonomic revision is unavoidable. Therefore, we revised the available museum collections, and collected new fossil material from several outcrops (mostly from localities of Jekelius). The studied outcrops were logged in order to infer their depositional environment, whilst the fossil molluscs were described and interpreted in terms of palaeoecology.</p><p>Our results show that offshore marls are dominated by the thin-shelled <em>Paradacna fuchsi</em>, which is very frequent throughout the Bra&#537;ov Basin. Littoral sands frequently contain coquina of dreissenids, while nearshore clays are rich of different gastropod groups, such as neritids, bithyniids, planorbids, hydrobiids, valvatiids, and lymnaeids and bivalves, such as dreissenids, cardiids, and sphaeriids.</p><p>Our taxonomic revision combined with field sedimentology and stable isotope analyses will improve our knowledge on the Pliocene mollusc fauna of this segment of the Carpathian region. Comparison of the studied fauna with the well-known fossil remains of the &#8220;<em>Paludina</em> layers&#8221; in Croatia and Serbia will be crucial in reconstruction of the latest Miocene to Pliocene palaeogeography of the Carpathian-Pannonian region.</p><p>Supported by the &#218;NKP-21-3 New National Excellence Program of the Ministry for Innovation and Technology from the source of the National Research, Development and Innovation Fund.</p>