engleski

New Proboscidean Site from the High Karst Dinarides in Southern Bosnia and Hercegovina

A new late Neogene proboscidean site, Cebara has been currently discovered by the local fossil collector Vinko Ljubas south of Tomislavgrad in Bosnia and Hercegovina. It is located in one ~40 m deep, ~20 m high and ~17 m wide incision of the escarpment opened during quarry exploitation at the southwestern margin of a typical Dinaride karst polje termed Duvanjsko polje. The latter represents a ~240 km2 large and NW-SE striking intra-mountainous basin that was initiated in the early Miocene (~17 Ma) as the eastern part of the Livno-Tomislavgrad basin. Herein two sedimentary cycles accumulated more than 2500 m of coal bearing lacustrine deposits until the latest Miocene (~6 Ma) therein. The posterior wall of distally narrowing incision shows coarsening upward succession of clays, fluvial gravels and block-breccia including up to 5 m diameter boulders developed through reoccurring cave roof collapses. Upward the incision in unroofed passing into a ~35 m wide and ~10 m deep funnel-shaped doline. The logged succession is 10 m thick with the base covered by debris and top not reachable at present outcrop conditions. It comprise two units of equal thickness. The lower one is characterized by deposition of brownish clay that can include sand lenses and/or laterally grade to block-breccia. Beyond that up to 1 m thick sand, gravel and boulder intercalations are present. The upper unit is composed of two conglomerate packages both topped by cave-in breccia. The lower gravel shows through- and cross-bedding and at its base operculi accumulations of freshwater snail Bythinia occur supporting the inference of riverine and/or lacustrine origin of the sediment. The bone bed interval is about 1.5 m thick and marks the middle part of the lower unit. The fossil bones, tusks and teeth oriented horizontally to the bedding plane, are disarticulated and concentrated in three 10 to 30 cm thick horizons. The lower one appears on top of one 30 cm thick gravel bed, the other two mark lower and upper part of one 90 cm thick sandy layer. Strongly increased magnetic susceptibility values (>100 x 10-6 SI) detects the black color of the bones and matrix sediments as containing iron- bearing minerals. The inspection of up to now available fossil remains allows their tentative classification as Anancus arvernensis (Croizet & Jobert 1928) representing a tetralophodon gomphothere characterized by two oversized straightened tusks in the upper jaw and a body- size of today's elephant. This European gomphothere has the peak distribution in the late Pliocene, and the stratigraphic range from the latest Miocene MN 11 to the early Pleistocene MN 17. Although the stratigraphic data does not allow a precise inference of the age yet, the lithostratigraphic evidence supports the correlation with the Pliocene and/or Pleistocene in a phase post-dating the Miocene long-lived lake conditions.

Dinarides; Proboscidea; late Neogene

nije evidentirano