Formation Conditions of Aptian-Albian Sediments in the Western Ciscaucasus Region

摘要

Results of investigations carried out in the Ciscaucasus region have revealed that Aptian and Albian sequences of this region are composed of sandy, silty, and clayey rocks. Glauconite is present in all types of petrographic rocks. The average glauconite content is 12-17% in sandstones and siltstones and is less than 5% in clayey rocks. The glauconite distribution is cor- related with the grain size composition of terrigenous rocks. The maximal glauconite concentration is confined to fine-psammitic and coarse-silty fractions. In order to reveal the formation conditions of glauc-onite-bearing complexes, we carried out a lithofacies study and paleogeographic reconstructions for the Aptian and Albian ages of the Ciscaucasus region. The Aptian-Albian rocks make up a single terrigenous formation. Based on specific features of composition and structure, the terrigenous formation is divided into the lower Aptian clayey-terrigenous, middle-upper Aptian glauconite-terrigenous, and Aptian terrigenous-clayey subformations.