VARIATIONS OF EU/EU* RATIO IN VENDIAN SHALES OF THE VOLGA-URAL REGION AND THE BOUNDARY TRACED BETWEEN THE REDKINO AND KOTLIN HORIZONS

Abstract

Variations of Eu/Eu* ratio in shales from the upper Vendian Kairovo and Shkapovo groups of the Shkapovo-Shikhan depression, the Volga-Ural region, are considered. Shales in the lower part of the Karlin Formation are established to be similar in geochemistry to the shale member with abnormally low Eu/Eu* ratios at the base of the Upper Vendian Kotlin Horizon of the East European Platform. According to these data, the studied formation appears to be a lithostratigraphic unit of the Kotlin Horizon, while the Baikibashevo, Staropetrovo and Salikhovo formations belong to the Redkino Horizon of the upper Vendian. © MAIK "Nauka/Interperiodica" 2006.