Stratigraphy and sequence stratigraphy of the Moscovian in the Donets basin

Abstract

New results are presented on the stratigraphy based on Fusulinids and Palynomorphs and the sequence stratigraphy of the Moscovian in the Donets basin. They have been developed by comparison of our observations on cross-sections near Artemovsk and the published coal mine logs of Artemovsk Geological Survey. The Moscovian of the Donets basin is equivalent to the uppermost Westphalian B and the Westphalian C and D of western Europe. In the Donets basin, the Moscovian forms a second-order sequence as in the Moscow basin, that can be subdivided into four third-order sequences, subdivided into fourth-order sequences. The upper Bashkirian shows two fourth-order sequences. The Vereian exhibits two fourth-order sequences. The Kashirian shows four fourth-order sequences. The Podolskian offers eight fourth-order sequences. The Myatchkovian presents four fourth-order sequences. These sequences begin with an erosive base and show a succession of elementary sequences with fluvial sandstone, coal seam, limestone and deltaic facies. The fluvial sandstone corresponds with an aggradation period, the coal and the limestone with a transgressive period and the deltaic facies with a progradation period. A decrease of the sandstone thickness and an increase of the marine deposits that are transgressive and regressive upwards are observed from the base to the top of sequences. These fourth-order sequences present a higher spatial amplitude than the third-order sequence and obscure these sequences. The second-order sequence equivalent to the Moscovian shows a lowstand system tract with more fluvial sandstone in the lower part of the Vereian, a transgressive system tract in the upper part of the Vereian, Tsinskaya and Kashirian, a maximum flooding period during the Podolskian and lower part of the Myatchkovian with more marine facies and a highstand system tract in the upper part of the Myatchkovian with more lagoonal and swampy palaeoenvironments. The sequences are controlled by the regional tectonic subsidence in the graben and the uplift of the horsts and/or by eustasy with either a plate-tectonic or a glacial origin. Other investigations, particularly radiometric dating, will be useful for solving this problem.