Paleontological characteristic of turonian deposits on the western slope of the Ukrainian shield

Abstract

Formulation of the problem. Turonian deposits of eastern Volhyn are very wide-spread, a number of mineral raw materials deposits are associated with them. The stratigraphic position is justified insufficiently.

The purpose of the article is to perform a detailed zonation based on the study of the fossil complex, to recreate features of the paleogeography of the Turonian basin.

Results. The results of studying the remains of calcareous nannoplankton, foraminifera, ostracod, and bivalve are presented in the work. In the section near the city of Zdolbuniv nanoplankton and foraminifera zones are established. In the lower Turonian the nannoplankton zone UC6 + UC7 and the Marginotruncana pseudolinneiana zone are highlighted.

In the lower part of the middle Turonian, a break is identified, which corresponds to the UC8 nannoplankton zone. In the upper part of the middle Turonian the Marginotruncana coronata zone, in the upper Turonian the Dicarinella canaliculata zone is discernible. In the middle and upper Turonian we defined nannoplankton zone UC9.

The foraminifera, ostracods and the bivalve have features of the Turonian paleobasin. In the lower Turonian, the complex of nannoplankton and foraminifera is depleted, ostracods are represented by one species, bivalvia are very rare, with a thin wall and small dimensions. This indicates a great depth of the basin.

At the beginning of the middle Turonian a break in sedimentation is observed. It was accompanied by erosion or karst in underwater conditions. Accumulation of precipitation at the end of the middle Turonian occurs in a shallow basin. Over time, the pool is even smaller, the amount of benthos and its diversity are increasing.

Scientific novelty and practical significance. For the first time a detailed zonation of Turonian deposits on a complex of fossils is conducted. Some features of the geological history of the basin have been established.