TURON NANNOPLANKTON BIOSTRATIGRAPHY OF NORTH-WESTERN DONBASS

Abstract

A Turonian stage in. north-western Donbass is composed of homogeneous chalk and chalk-like marl, in which there are no remains of macrofossils. Several sections of Kharkiv region have been studied.

To show chalk monoliths textures were impregnated with machine oil. Four types of textures were established: numerous cracks, traces of mud-eaters, spotted texture, stains of ferrugination. Three packets were identified (bottom-up): chalky breccias, chalk with interbedded clay and flintstone, chalk with moves of mud-eaters and the remnants of the shells Inoceramus.

In the studied range (upper Cenomanian - lower Cognacian) 51 species of calcareous nannoplankton were established. In the nannocomplexes of Turonian north-westerm Donbass no dominant taxa were found. They were numerous in the southern sections Watznaueria, Cyclagelosphaera, Retecapsa, Zeughrabdotus, Microrhabdulus, and in the studied deposits they were found in small quantities. But such species as Kamptnerius magnificus, Manivela pentatomidae, Quadrum gartneri, Gartnerago spp., are becoming more numerous.

In the lower Turonian zone UC6, UC7; on middle Turonian zone UC8; in the upper Turonian subzone UC9a+b were identified. Boundary of Turonian and Coniacian in sole subzone UC9c conducted. Also, the lower zone of Cognacian UC10 has been installed.

Regional break on the boundary of the lower and middle Turonian not one but a series of closely spaced unconformities were presented. This is due to the non-accumulation of sediment or flushing.