Abstract:
Results of the litho- and biostratigraphic studies of core samples from more than 40 deep oil and gas prospecting wells drilled in the Kolpakovka depression in the 1980s and 1990s were considered. The lithology of Paleogene deposits and their fossils (bivalve mollusks, benthic foraminifers, and palynofloral assemblages) were investigated. Paleogene sections of two types - eastern and western - were established based on the data obtained. Sections of the first type comprise a more complete Paleogene rock succession that includes the Snatol and Kovachina formations and the entire Voyampol Group; the lower part of the Paleogene sequence is missing here. Sections of the second type are characterized by an incomplete Paleogene succession. The lower Paleogene strata are also missing here (the Khulgun Formation is defined arbitrarily); only the Snatol Formation and the upper Voyampol Group are present. The absence of the Kovachina, Amanin-Gakkh, and lower Utkholok-Viventek horizons from the Paleogene section of the western part of the depression implies a hiatus corresponding to the upper Eocene-lower Oligocene.