Stratigraphy and sequence stratigraphy of the Moscovian, Kasimovian and Gzhelian in the Moscow Basin

The Moscovian deposits form a second order sequence (5-6 m.y.) with a complete cycle of tectono-eustatic variations including a lowstand system tract (LST), a transgressive system tract (TST) and a highstand system tract (HST). The Moscovian deposits are subdivided into four formations or third order sequences (1 m.y.) named Vereia, Kashira, Podolsk and Myachkovo by the Russian stratigraphers; which can be further subdivided into two fourth order sequences (about 500 k.y.); which in turn can be further subdivided into elementary sequences (about 100 k.y.). Vereia shows tow fourth order sequences, Kashira four, Podolsk three and Myachkovo two. The Kasimovian deposits form a second order sequence (3-5 m.y.) with a complete cycle of tectono-eustatic variations. They are subdivided into three formations or four third order sequences (1 m.y.) named Krevyakino, Khamovnichi, Dorogomilovo; which can be further subdivided into members or fourth order sequences (about 600 k.y.); which in turn can be further subdivided into elementary sequences (about 250 k.y.). Each third order sequence shows two fourth order sequences, the first more transgressive and the second more regressive. The Gzhelian deposits form a second order sequence (5-6 m.y.) with a complete cycle of tectono-eustatic variations. They are subdivided into five formations or five third order sequences (1 m.y.) named Rechitsy, Amerevo, Pavlov-Posad, Noginsk and Melekhovo; which can be further subdivided into members or fourth order sequences (about 600 k.y.); which can be in turn further subdivided into elementary sequences (about 200 k.y.). Each third order sequence shows two fourth order sequences, the first more transgressive and the second more regressive. At whatever order, the sequences present a similar organization: the TST consists mainly of limey deposits. The overlying deposits are more clayey and dolomitic: they represent a HST with terrigenous supply. In order to check the continuity of the sequences, our data have been compared with previously described boreholes located on West-East cross-sections. Except for the Tsna Member known only eastwards, the same fourth order sequences number is recorded within the basin. During the Moscovian and Kasimovian time, the Moscow Basin presents a thinner western border and a eastern trough. During the Gzhelian time, some inversions in subsidence occur. For the mechanisms of genesis of these sequences, their continuity proves the allocyclicity. However, the tectonics and the eustasy interfere. The tectonic subsidence is low or moderate in the Moscow Basin. The fourth order sequences are more prominent than the third order sequences, which would be characteristic of an eustasy produced by the melting of polar ice cap located in Gondwanaland during the late Carboniferous. However, the stratigraphic completeness and the associated preservation of the sequences are low at the western border of the basin and better eastwards.