Stratigraphy and facies development of the upper Tithonian-lower Berriasian Nizniow Formation along the Dnister River (Western Ukraine)

摘要

The deposits of the Nizniow Formation, exposed around Nizniow, mainly on the banks of Dnister River, accumulated in the most proximal, marginal position of the latest Jurassic-earliest Cretaceous epicontinental basin on the SW margin of the East European Platform. The Nizniow Formation directly onlaps a Palaeozoic substrate and consists of transgressive cliff-derived conglomerates, and sandstones and marls which pass laterally into shallow marine carbonates: mainly biomicrites, oncomicrites, and pelmicrites with an abundant benthic fauna dominated by nerineid gastropods. The thickness of the formation in the area studied ranges from 0 to more than 20 metres and was controlled by morphology of the pre-transgression substrate (mainly built of Devonian clastic rocks), synsedimentary fault tectonics and pre-mid-Albian erosion. The age of the Nizniow Formation can be determined, on the evidence of benthic foraminifers encountered in thin sections, as most probably late Tithonian-early Berriasian.