Late Jurassic-earliest Cretaceous evolution of the epicontinental sedimentary basin of southeastern Poland and Western Ukraine

Abstract

The following Late Jurassic depositional systems have been recognized in the W Ukrainian and SE Polish margin of the East European Platform: shelf slope/basin, open shelf, carbonate ramp, siliciclastic shelf, fluvial/playa, deltaic/swamp, restricted marine/evaporate lagoon. Three depositional megasequences have been identified. Their upper boundaries have been dated by means of targeted stratigraphic studies, compilation of existing data and reinterpretation of stratigraphic correlation concepts respectively as: lower Kimmeridgian divisum/hypselocyclum zones boundary, uppermost upper Kimmeridgian and lower Berriasian. Analysis of thickness and depositional system architecture within the megasequences in six regional cross-sections indicates that depocentre was located in the SW margin of the Mid-Polish Trough during Oxfordian and early Kimmeridgian times and propagated in Tithonian time to the Lviv region. This can be explained by changes in the palaeostress field. Approximately N-S oriented extension during Oxfordian and earliest Kimmeridgian times was replaced by approximately NE-SW oriented extension in Tithonian time. The thickness pattern of the megasequences as well as proximity trends of the system tracts within the sequences clearly coincide with the depocentre propagation.