EVIDENCE OF LATE PALEOCENE - EARLY EOCENE HYPERTHERMAL EVENTS IN BIOSILICEOUS SEDIMENTS OF WESTERN SIBERIA AND ADJACENT AREAS

Changes in diatom and silicoflagellate assemblages from the terminal Paleocene-Early Eocene were analyzed for the first time from the biosiliceous sediments of North Eurasia in the Pechora Depression, northern and middle Transuralia, the Omsk Depression, and Mugodzhary (Russia). Two intervals of significant siliceous microfossil turnover were revealed. The first one correlated with the Apectodinium hyperacanthum+Apectodinium augustum dinocyst zones and is characterized by an increase in species diversity due to the invasion of Tethyan forms, occurrence of Cretaceous and Early Paleocene relicts and appearances of short-lived taxa with atypical morphology, and is interpreted as the PETM event. The second level corresponding to the second half of the Early Eocene (similar to NP 12), is marked by a reappearance of some species characteristic of the transitional Paleocene-Eocene interval, first occurrences of two genera and a number of species and by a strengthened biosiliceous sedimentation indicating an increase in the productivity of the basin.