Change of sedimentary record as a consequence of variation in depth and dynamics of depositional environment (East Slovakian Basin, Middle Miocene)

Middle Miocene sedimentary record of VSP-1 borehole situated in the East Slovakian Basin area was studied on well cores and well log diagrams. Documented sedimentary structures provided valuable information about the mode of transport and deposition, as well as about subsequent synsedimentary changes in soft sediment. Different transport mechanisms and depositional environments provide important information on the basin palaeogeography during the Serravalian (Upper Badenian and Lower Sarmatian regional stages), since the depositional environment in the study area changed from the deeper neritic environment of basin slope or lower part of the delta slope to the shallow neritic to littoral, coastal or delta plain environment. Deep water setting is characterized mainly by fine-grained sediments of gravity flows with slumps, showing grain flow to turbidity current features. The typical sedimentary structures are: erosive base of beds, normal grading, etc. Sediments are usually disturbed by synsedimentary deformations as slumps and growth faults. Shallow water setting was identified on the basis of specific sedimentary structures as: planar cross and trough cross bedding, ripple marks, hummocky cross stratification, flaser, wave and lenticular bedding. These sedimentary structures originated in shallow water, high energy environment, but each of them at different dynamic condition. Results obtained by the study of sedimentary record of the VSP-1 borehole fit well with the Upper Badenian and Lower Sarmatian palaeogeographical models of Vass et al. (2002) and confirm the rightness of defined changes of depositional environment in the Trebi ov Depression of the East Slovakian Basin in time and space.