Revisiting stratigraphic complexes and regional stratigraphic scheme of the lower precambrian of the Ukrainian shield

Abstract

The stratigraphic scheme of the Early Precambrian of the Ukrainian Shield bears a number of differences from the traditional regional stratigraphic schemes: 1) along with stratified subdivisions it includes intrusive and ultrametamorphic complexes that are not accounted for in the “Stratigraphic Code of Ukraine”; 2) The leading role in creating the regional stratigraphic scheme was played by isotopic dating results; 3) The Stratigraphic Scheme does not include the taxon “complex”, as it is described in the “Stratigraphic Code of Ukraine”. According to “Stratigraphic Code of Ukraine”, “Complex” is the largest regional stratigraphic unit that corresponds to a large geo-historical period. Due to the absence of the taxon of “complex” in the regional Precambrian stratigraphic scheme, the main stages of geological development of the region in the Precambrian have not been identified for the Ukrainian Shield. The first article of the cycle is devoted to the feasibility of introducing the taxon of “complex” in the regional stratigraphic scheme on the materials of the Ukrainian Shield. It notes that most of the series in the current stratigraphic scheme correspond to complexes by their level of study and their historical and geological content. Such units are Konkska, Kryvorizka, Teterivska, Ingulo-Inguletska and some other series. Each of them can be separated into several series. The Dniestrovsko-Bugska and Bugska series, the West-Priazovska and Central-Priazovska series of granulite-gneiss complexes are artificially separated and shown as different age subdivisions in the current stratigraphic scheme. These series should be included in the Bug Area and Azov Area complexes, but their volumes and names need clarification. Amphibolite-gneiss complexes can be included in the stratigraphic scheme without dismemberment into series, since they correspond to a large geohistoric stage marked by the peculiarities of their material composition and structural-tectonic position.