Palaeontological dataof the San Emiliano Formation (Cantabrian Mountains, Spain) and their significance in the Carboniferous chronostratigraphy

Abstract

This paper deals with the chronostratigraphic position of the San Emiliano Formation (lower Upper Carboniferous of the Cantabrian Mountains, Spain), which contains marine as well as continental fossiliferous strata, and therefore provides the elements for a correlation between East and West-European chronostratigraphic schemes. These studies have been carried out in the type-section, near the village of San Emiliano, and in the Bernesga Valley, near Villamanín. Important for the determination of its stratigraphic position is the presence of continental flora, brachiopods, and fusulinid foraminifera, at various levels in the formation. Hence, data on flora and fauna with a bearing on the stratigraphic position of the formation are reviewed, with special attention to fusulinid foraminifera. Additional data on the fusulinid content in some localities in the type-area are also presented on the basis of a collection of thin sections described by Carballeira et al. (1985). The results of some earlier studies, from 1965 to 1988, on the identification and dating of fusulinids, are compiled and, whenever necessary, modified. Conclusions are drawn from the analysis of data on the age of the various subdivisions of the formation. The revised biostratigraphic information on the San Emiliano Formation allows to suggest correlations between the relevant parts of the chronostratigraphic classifications of West and East Europe. It seems that the Lower/Upper Bashkirian boundary and that between the Namurian and the Westphalian more or less coincide. The Bashkirian/Moscovian boundary probably corresponds to the interval between Upper Westphalian A and basal Westphalian B. This is a lower position than that admitted in the Donets Basin where it has generally been correlated with the Westphalian B/C boundary.