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Composition and Provenance of the Neogene Clastic Material from Dilj Mt., South Pannonian Basin, Croatia

Dilj gora (Dilj Mt.) is a hillocky area in Eastern Croatia, in the southern part of the Pannonian Basin Province. It represents a small fragment of the Inner Alpine-Carpathian foldbelt and the Dinarides (ROYDEN & HORVÁTH, 1988), built up mainly of Neogene and Quaternary sediments, and small bodies of volcanic rocks (ŠPARICA et. al. 1980). Recent investigations divided Neogene sediments into Lower Miocene sediments (Karpatian(?) to Sarmatian) (PIKIJA et al. 2005) and Late Miocene and Pliocene sediments of Dilj Mt. (KOVAČIĆ et al. 2005) and earmarked eleven informal lithostratigraphic units (Ravan, Tuk, Zdenci, Dubovik, Glogovica, Kasonja, Croatica, Pavlovci, Andraševec, Nova Gradiška and Cernik). Detailed sedimentological investigations showed that the lowest part of the Miocene (Ravan unit) is built up of poorly sorted clastic sediments: sands and gravels. The dominant rock pebbles derived from sedimentary rocks and metamorphic rocks. The sedimentary source rocks were composed (by) of limestone and sandy limestone, calcitic siltstone, sandstone (greywackes) and polimict breccias. Among the metamorphic source rocks marble, slate/phyllite and amphibole schist were the most common. This unit also contains pebbles of anchi-metamorphic rocks (metamorphosed carbonate and clay laminae alternate). The modal composition of the sands is characterized by the dominance of lithic fragments while quartz and kaolinized alkali feldspar are minor components. The heavy mineral association is marked by epidote, tourmaline, garnet, glaucophane and Fe-oxides. Sediments of the Tuk unit (clayey to sandy siltstones with lenses of sands and gravels) develop gradually from the previous unit. This unit is marked by the occurrence of volcanic rock pebbles along with particles of acidic volcanic rocks, fresh alkali feldspar and biotite in the sand fraction. The Zdenci and Glogovica units are built up of bioclastic limestone while the Dubovik unit consists of silty marls and calcsiltstone. The Kasonja unit contains siliciclastic sediments beside fossiliferous carbonates. It is mainly made up of sand rich in quartz and fresh alkali feldspars. Gravels appear occasionally with pebbles of quartz sandstone and metasandstone, leucocratic granite, gneiss, quartzite and limestone. The Croatica and Pavlovci units are composed of limestone and marl. The Andraševec, Nova Gradiška and Cernik units are composed of well sorted sandy and silty sediments rich in quartz. Garnets and epidotes characterize their heavy mineral association. The petrographical composition of the sediments and the imbrication of pebbles in the Ravan unit point to material transport from the south, most probably, from the Inner Dinarides (north Bosnia geographically). The fresh material in the Tuk and Kasonja units suggests their local origin. Meanwhile, the structural and mineralogical maturity of the Andraševec, Nova Gradiška and Cernik unit sediments and the orientation of cross-bedding and cross-lamination in the sands of the Nova Gradiška and Cernik units indicates material transport from the north and points to an Alpine-Carpathian provenance.

provenance; neogene; clastic material; Pannonian Basin; Dilj Mt.

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