Biostratigraphy and lithofacies of the Viséan and Serpukhovian deposits of the southeast of the East European platform

Abstract

This paper presents new data on the biostratigraphy and sedimentology of Upper Visan and Serpukhovian deposits (Lower Carboniferous) from boreholes in the southeast of the East European Platform around the Sol-Iletsk Swell (Orenburg region). Based on rock lithology, sublatitudinal facies zones are recognized in the studied area. The deposits are represented by open shallow shelf facies, up to 500 m thick, in the area of the Sol-Iletsk Swell and near-side zone of the Preuralian Foredeep. To the south, at the margin of the Northern Pericaspian, their thickness sharply decreases to 36 m, and the succession is composed of carbonate-clay sediments of the relatively deep shelf. Based on foraminifers and conodonts, the Upper Visan and Serpukhovian are subdivided using the horizons of the stratigraphic scheme of the East European Platform, and foraminiferal zones are recognized. The base of the Serpukhovian in the high-energy shallow-water facies of the open shelf is drawn at the entry of the foraminifers Janischewskina delicata and Endothyranopsis plana; in lower-energy facies, it is placed at the level of the first appearance of Neoarchaediscus postrugosus; in the clay-carbonate facies of the relatively deep shelf it is based on the appearance of the conodont Lochriea ziegleri. The distribution of microfauna from the five boreholes, the characteristics of the foraminiferal zonal assemblages, and the interregional correlation are discussed.

Foraminifers in upper Viséan–lower Serpukhovian limestones (Mississippian) from South Wales: regional correlation and implications for British foraminiferal zonal schemes

“…; both taxa are represented from the mid Brigantian (Hallett 1971;Cózar & Somerville 2004). In west Eryrys, and contrasting with the previous revision, the occurrence of Euxinita in the upper part of the Leete Formation led Davies et al (2004) Viséan marker in the Russian platform for the Aleksian Substage (e.g., Lipina & Reitlinger 1971;Kulagina et al 2003Kulagina et al , 2019, and some rare specimens of Archaediscus at angulatus stage can occur from the top of the Holkerian, but abundant specimens are only present in the Asbian. Thus, contrary to Strank (1981), the upper part of the Leete Limestone in the Llangollen area contains a fauna that can be interpreted, at least, as early Asbian in age.…”

“…protvae and E. inconstans, which are not found anywhere in the Urals below the late Serpukhovian (see Kulagina et al 2003Kulagina et al , 2009Kulagina et al , 2011Kulagina et al , 2019Nikolaeva et al 2009;Kulagina & Klimenko 2014;). It would be rather unusual to record the more advanced species of Eostaffellina in older levels than more primitive species, such as E. decurta or E. paraprotvae.…”

“…Reitlinger (1963) considered the first species of the genus Eostaffellina ovesa (Ganelina), recorded from the Tulian Substage (which was correlated to the upper part of the Holkerian, see Vachard et al 2018a), with an unsuccessful lineage in the Viséan represented by E. zelenica (Durkina) and E. irinae (Ganelina) at the base of the upper Viséan Aleksian and Mikhailovian Russian substages, respectively. Other authors also considered Eostaffella accepta Ganelina as a primitive Eostaffellina (e.g., Kulagina et al, 2019). It is difficult to validate if those small species (E. ovesa and E. accepta) are true Eostaffellina, although the larger species, E. zelenica and E. irenae show more features in common with Eostaffella than with Eostaffellina.…”