Evolution of conditions of sedimentogenesis in the Carpathian flysch basin in the Cretaceous–Paleogene

Abstract

The aim of this work is to show the evolution of geological-paleoceanographic and geochemical conditions of sedimentation in the segment of Carpathians of the Tethys Ocean. And also, selection of the basic stages of sedimentogenesis, to which the formation of oil and gas parent and oil- and gas-bearing deposits is timed. In the article, the authors showed the lithologic-genetic classification of the Cretaceous-Paleogene flysch of the Ukrainian Carpathians. Authors distinguished the lithologic-geochemical types of sedimentation son the basis of geochemical terms of sedimentation, and also lithologic-facies types of sedimentation on the basis of features of terrigenous sedimentation. Four stages of sedimentogenesis in the history of geological and paleoceanographic development of the Carpathian sedimentary basinare described in the article: Early Cretaceous (stage I), Late Cretaceous (stage II), Paleocene-Eocene (stage III), Oligocene-Early Miocene (stage IV), each of which has specific geochemical conditions of sedimentogenesis and diagenesis. It is shown that forming of Cretaceous-Paleogene flysch deposits of Ukrainian Carpathians took place under action of very changeable geological-paleoceanographic and geochemical factors the joint action of that stipulated oil and gas capacity of this sedimentary complex. The thick series of psamitolites were formed in periods of avalanche terrigenous sedimentation, that are the reservoirs of hydrocarbons. Formation of bituminous parent-rocks-of-oil siliceous-clayed sedimentation is related to deceleration of processes of terrigenous sedimentation and phases of ocean anoxic events of ОАЕ-1 (Barremian–Albian) and ОАЕ-4 (Oligocene).