Cenozoic Stratigraphy of the Eastern Part of the Opukha-Pekulney Depression, Koryak Upland, Northeast Russia

摘要

The Cenozoic marine deposits (two formations) developed in the eastern part of the Opukha-Pekulney Depression of the Koryak Upland are described. Until recently, there was scarce information about them. The lower (Retyrveem) formation is composed of dark conglomerates and sandstones with a large number of carbonate nodules and representative assemblages of bivalve and gastropod mollusks (more than 400 tests and imprints were studied) and Early Eocene benthic foraminifers. Two subformations and six units were distinguished in the formation. The upper (Morzhovaya) formation is composed of light loose gravestones and sandstones, including fragments of Early Miocene mollusks and foraminifers. The study of faunal assemblages makes it possible to correlate these formations with stratigraphic units of adjacent areas and to reveal hiatuses in the section covering most of the Paleocene sequence, on one hand, and the Upper Eocene and Oligocene, on the other hand. The Retyrveem Formation encloses warm-water molluscan assemblages, the appearance of which in the northern boreal latitudes is supposed to be related to the Early Eocene global warming. Images of the characteristic molluscan remains are given for the first time.