The Pannonian Palaeoecology and Biostratigraphy of Molluscs from Kostanjek - Medvednica Mt., Croatia

• Main Author: Davor Vrsaljko
• Format: Article
• Language: English
• Published: Croatian Geological Survey 2010-11-01
• Series: Geologia Croatica
• Subjects: Mollusca; Cardiidae; Lymnocardiidae; Phylogenetic series; Biozone; Pannonian; Pannonian basin; Medvednica Mt.; Croatia
• Online Access: http://www.geologia-croatica.hr/ojs/index.php/GC/article/view/276

<div>On the south-western slope of Medvednica Mt., an 83 m thick</div><div>geological column Kostanjek-1, composed of strata representing the</div><div>Sarmatian and Pannonian stages, was investigated in detail. Facies</div><div>analysis allowed separation of five lithofacies units (A, AB, B, C and</div><div>D) and the sedimentary mechanisms for particular successions were</div><div>defined. A rich community of fossil molluscs (50 species) and ostracods</div><div>(42 species) was sampled and determined. From these fossil</div><div>determinations, the sediment age was defined, and biofacies analysis</div><div>allowed the determination of three basic palaeobiocenosis types: 1) a</div><div>community from Sarmatian brackish lagoons, 2) a community from</div><div>an Early Pannonian littoral lake, and 3) a lake basin community in the</div><div>Late Pannonian. The main &Ograve;record&Oacute; of the salinity crisis (drop) at the</div><div>Sarmatian-Pannonian boundary influences in a selective way the</div><div>majority of organisms, and is shown best in the evolutionary form</div><div>changes of cardid bivalves, for which phylogenetic series were made.</div><div>On the basis of dominant and characteristic forms in the entire association&nbsp;of Pannonian molluscs five biozones were separated: I) Lymno&nbsp;cardium praeponticum acrozone, II) Radix croatica - L y m n o c a r d i u m&nbsp;plicataeformis - Gyraulus praeponticus cenozone, III) Neodelminiella&nbsp;venusta - Lymnocardium cekusi cenozone, IV) Congeria banatica -&nbsp;Lymnocardium gorjanovici - Gyraulus tenuistriatus cenozone and V)&nbsp;Congeria czjzeki - Lymnocardium winkleri - Gyraulus tenuistriatus</div><div>cenozone. Many ostracod forms supply and test the stratigraphic value</div><div>of molluscs and support zonality of Pannonian layers.</div>