LOHKOVIAN DEPOSITS OF THE WEST SLOPE OF THE SOUTH URALS, THEIR DIVISION AND GLOBAL CORRELATION BASED ON CONODONTS

Abstract

Relevance of the research. Today, among the global priorities is the development of a standard conodont scale for the Lohkkovian and Pragien stages of the Lower Devonian. In accordance with this, the study of regularity of conodonts distribution in Lower Devonian sediments is actively conducted in various regions of the world. The aim of the study is to identify regularity of conodonts distribution in the Lohkkovian deposits of the west slope of the South Urals to create a regional conodont zonation. Methods. Two horizons are distinguished in the carbonate sections of the Lohkkovian stage on the west slope of the South Urals. The Lower Lohkkovian corresponds to the Siyak Horizon, the upper Lohkkovian – to Sherlubay Horizon. We studied the sections of the Siyak and Sherlubay Horizons on the сonodont fauna to solve the problems posed. The samples were taken with an interval of 15–20 cm. The weight of the samples was 1–2 kg. Under laboratory conditions, limestone was disintegrated in formic acid. The insoluble residue was viewed under a binolupe in order to identify conodonts. The selected conodonts fauna was analyzed. Results. Numerous conodonts were found in the Sherlubay Horizon in the Mindigulovo section. They are represented by cosmopolitan species that allowed the creation of a regional biozonal conodont scale for the west slope of the Southern Urals. Seven conodont zones were identified: omoalpha, transitans, eleanorae, trigonicus, kutscheri, pandora beta, gilberti. The developed conodont scale is equivalent to other scales of the peri-Gondwana regions, which makes it possible to directly perform the global correlation. The data obtained in the research allow us to accept the point of view on three-term division of the Lohkkovian stage. According to this, the Sherlubay horizon includes the middle (lower part of the horizon) and the upper Lohkkovian (upper part).

Keywords

• south urals
• lower devonian
• lohkkovian stage
• sherlubay horizon
• conodont zonation
• correlation