Shoreline Cross-bedded Biocalcarenites (Middle Miocene) in the Podvrsko-Snjegavic Area, Mt. Psunj, and their Petroleum Significance (Pozega Subdepression - Eastern Croatia)

Abstract

The extensively distributed bioclastic sedimentary bodies in the Podvrsko-Snjegavic Area, Mt. Psunj (Pozega Subdepression, Eastern Croatia) are mostly composed of fragments of bryozoans, echinoids, lamellibranchs and corallinaceans. Apart from this, a relatively compositionally uniform, but granulometrically variable bioclastic detritus occurs, which also contains a smaller proportion (5-30%) of siliciclastic grains of medium to coarse sand, as well as sporadic pebbles up to 60 mm in diameter. These sediments are characterised by remarkably large-scale cross-bedding with erosional surfaces clearly delimiting the sets. They are interpreted as shallow-marine shoreface subaqueous dunes, sand bars and barriers formed on the nearshore - mainly shoreface area during the Late Badenian in a high-energy depositional cycle with strong synsedimentary tectonics. With regard to the petroleum-geological reservoir characteristics, the described Middle Miocene cross-bedded biocalcarenites are compared with numerous large oil and gas pools globally, and in other localities in Croatia on the margins of inselberg massifs between the Drava and Sava rivers and south of the Sava river.