HISTORY OF THE GEOLOGICAL DEVELOPMENT OF THE BLACK SEA NORTHWEST SHELF IN THE LATE NEOPLEISTOCENE-HOLOCENE

Abstract

Research results are presented into the geological history of the Black Sea’s northwestern shelf during the late Neopleistocene and Holocene. The principal goal was to reconstruct the age, character of transformation, and changes in Black Sea level and salinity focusing on the Neopleistocene-Holocene boundary using evidence from conjugate paleontological (foraminifers, ostracods, mollusks), lithological, and ecostratigraphic analyses of bottom sediments supplemented by radiocarbon dating.Samples were collected during geological survey of the northwestern Black Sea shelf, and data have been entered into electronic databases for use in future paleo-oceanographic reconstructions.The Early Neoeuxinian lake level rose from -100 m to -39 m bsl following the Late Neoeuxinian transgression due to Caspian inflow. It was brackish (5-12 psu), never freshwater, and it transformed into the Black Sea around 9.0 ka BP with the Mediterranean transgression, which was progressive, gradual, and oscillatory, not catastrophic or fast. The first wave of in-migrating Mediterranean organisms was weak and synchronous with the first (Bugazian) transgression phase. It slowed and even stopped during the following Kolchidian regressive phase, then stabilized during the second (Vityazevian) wave of migration, reaching its maximum during the Kalamitian and Dzhemetinian transgressive phases (third and fourth migration waves). The oscillating character of the Mediterranean transgression and re-colonization of the Late Neoeuxinian lake by marine fauna can be clearly traced on the inner shelf only due to the low amplitude of the sea-level and salinity changes. It is almost invisible on the outer shelf of the Black Sea, below isobath -100 m.