ЛИТОФАЦИАЛЬНЫЕ ОСОБЕННОСТИ ИЗВЕСТНЯКОВ НИЖНЕЙ ПЕРМИ СТЕРЛИТАМАКСКИХ ШИХАНОВ
 (LITHOFACIAL FEATURES OF THE LOWER PERMIAN LIMESTONES OF THE STERLITAMAK SHIKHANS)

Abstract

The article deals with the lithofacial features of the Asselian and Sakmarian limestone of the Cisuralian Series of the Permian System, composing the particular mountains Yuraktau, Kushtau and Tratau on the right bank of the Belaya River near the city of Sterlitamak in the Bashkir PreUrals. Biohermic and bioclastic (detrital) lithofacies are distinguished in the limestone composition. Biohermic types are represented by bryozoans and coral framestones and rudstones, tubiphytes packstones, palaeoaplisyna boundstones and rudstones. Granular or bioclastic lithofacies are represented by fusulinid, crinoid-fusulinid grainstones, bryozoans and bryozoans-tubiphytes packstones, crinoid and polybioclastic packstones and wackstones. Polybioclastic packstones and crinoid-fusulinid grainstones predominate in the section of the Lower Permian limestones. In the Asselian part of the section, at the base of the shikhans, there are bryozoans and bryozoans-tubiphytes lithofacies. These limestones make up the shihan Toratau. Coral lithofacies are common in the section of shikhan Yuraktau in the upper part. On the Mount Kushtau, according to drilling data, coral types are confined to the upper part of section, to the Sakmaian stage. The top of Mount Kushtau is composed of palaeoaplisyna limestones composing stratified bioherms with a thickness of up to 40 m. The distribution of limestone lithotypes by section shows the change of the bryozoans-tubiphytes association in Asselian time by coral- palaeoaplisyna bioherms in the Sakmarian time.