Evolution of depositional systems and sedimentary cycles in Želiezovce Depression of the Danube Basin

Abstract

Five deep wells (Pozba4, Pozba3, Dubnik1, Nová Vieska1, Modrany1), drilled in the Želiezovce depression of the south-east Danube Basin penetrate the Cenozoic sedimentary record in overall thickness ranging from 1000 m up to 3000 m, the total thickness gradually increases from South to the North. This area is well known for the complex geological structure related to the Central Western Carpathians and Transdanubian Range junction along the Hurbanovo – Diösjenö line. Many authors have studied this area in the past,  nevertheless Depositional systems, sedimentary cycles and the development of sedimentary facies were never understood in detail. The Re-evaluation of biostratigraphy, paleoecology, sedimentology and the Re-interpretation of e-logs ware all incorporated into well correlations, what resulted in definition of four main sedimentary cycles: (1) The Lowermost Oligocene cycle, consisting of mudstones with occasional sandstone intercalations, associated with slope to offshore marine environment what is supported by the presence of the NP 22 calcareous nannoplankton zone. (2) The transgressive Langhian (Lower Badenian) deposits, composed of mudstones with epiclastic volcanic material and tuffite beds ware associated with shelfall to offshore environement the age is supported by the NN4 - NN5 calcareous nannoplankton zone. (3) The Serravallian (Upper Badenian - Sarmatian) cycle is composed mainly by mudstones with abundant Lithothamnium fragments associated with brackish coastal pain environment, supported by the NN6 calcareous nannoplankton zone and by the mass occurrence of fish scales and  Ervilia dissita (Eichwald) bivalves. (4) The overlying strata are represent the Tortonian-Pliocene (Pannonian-Pliocene) cycle, consists mostly from claystone which are overlain by sandstone and siltstones layers is associated with lake, deltaic and alluvial plain environment.