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Daria Baranova, Paleontological Institute RAS (Russian Federation)
Pavel Kabanov, Paleontological Institute RAS (Russian Federation)
Aleksandr Alekseev, Moscow State University (Russian Federation)
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The studied section occurs in Mesen Basin, a narrowed part of the Late Carboniferous eperic shelf dividing the Moscow and Arctic basins. The succession consists of thin (< 3-4 m) shallow-marine carbonate (in Moscovian) and argillaceous-carbonate (in Kasimovian) "catch-up" sequences or cyclothems. Cyclothem-dividing unconformities are expressed by truncated subaerial exposure profiles. Numerous ravinements define the smaller-scale cycles regarded as parasequences. The section is dominated by shallow subtidal bioclastic wackestones and packstones. Three sequences (ORL1 through ORL3) are recognized in Myachkovian and four (RNP1 through RNP4) in Kasimovian. The non-dolomitized or partly dolomitized sedimentary facies are available in six sequences marked as ORL1, ORL2, ORL3, RNP1, RNP2, and RNP3. Dolomitization obscures the section of the sequence RNP4 and completely obliterates sedimentary features in the section above.
Fusulinoid assemblages of ORL1 - ORL2 are dominated by Fusulinella incl. F. bocki, which is consistent with co-named zone. The lower part of ORL3 shows abundant Fusulina and first Fusiella lancetiformis pointing to the zone Fusulina cylindrica. The ORL1 through ORL3 contain numerous Fusulinella famula, the form typical for coeval strata of North America and Canadian Arctic but previously unknown in Moscow Syneclise. The overlying sequences RNP1 through RNP3 are rich in fusulinoids. The RNP1 and RNP2 retain the upper Myachkovian character with Fusulina cylindrica, numerous Fusulinella in RNP1, Fusulina quasicylindrica in RNP2, and no lower Kasimovian index species. New species (mass Protriticites pseudomontiparus, P. subovatus, and large tests of Fusulina pulchella) show up only in the upper part of RNP3 pointing to the Voskresensk-Neverovo interval of the lower Kasimovian. Rare Montiparus sp. appearing in RNP3-f is consistent with the Neverovo Formation. Surprisingly, the base of RNP4 contains relict Myackovian Fusulina cylindrica and F. quasicylindrica, whereas Kasimovian index species are not observed. Relict genus Neostaffella also persists up to RNP4.
Fusulinoid data conform to allostratigraphic and conodont correlations. The sequences ORL2 and ORL3 correspond to the Domodedovo and Peski cyclothems of Moscow Basin. The ORL1 corresponds to the Korobcheevo part of the Shurovo-Korobcheevo cyclothem. Assuming Kasimovian age of the overlying section, the sequence RNP1 is matching Suvorovo cyclothem. The RNP2 generally corresponds to the Voskresensk Formation with the shallow-water carbonate unit RNP2/3 correlated to Ratmirovo limestone of the type area. The RNP3 with its thickest highstand unit RNP3-f is consistently correlated with Neverovo formation of the Moscow Syneclise where maximum early Kasimovian flooding is recorded.
Studied cyclothems can be correlated at distances exceeding 1000 km across the EEC. Fusulinoid assemblages of studied section include North American forms. This study is supported by RFBR Project 07-05-00737.
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