THE SILURIAN OF LOWER PRIDNESTROVIE, THE PROBLEMS OF STUDY, PROSPECTS, PRACTICAL SIGNIFICANCE

Abstract

Problem Statement and Purpose. In Lower Pridnestrovie, the Silurian system rocks are widely distributed, well stratified, and composed of thick mainly limestone-do­lomite strata with thin layers of anhydrite, reaching 243-400 m in the southern part. The last geological survey works were carried out in the study area in the early 1990s. Reinterpretation of the received factual material of previous years can give more ac­curate ideas about the stratigraphy of the pre-Mesozoic sediments of the region.Data & Methods. For the article, the deep drilling data for 28 wells crossing the Si­lurian served as material. While processing the actual material, modern GIS methods were used. The actual material on the well columns was compiled in the database "Mane base" created in the software product K-MINE.Results. The article shows the comparison of Silurian stratigraphical schemes of re­search area of different authors as well as the contradictions are examined. The first campaigns of geological exploration of the territory were conducted in the 1960s (Bukatchuk et al., 1967). Following the chronology of the Lower Palaeozoic of Po­dillya of that time, accordingly, the Moldavian horizons and strata were assigned to older epochs and ages of the Silurian. The refinement in the 1970s of the stratigraph­ical scheme of the Silurian of Western Ukraine allowed Moldavian geologists in the 1980s to redistribute the intervals in earlier drilled (1960s) exploration wells to new local formations and members of corresponding age (Bukatchuk et al., 1985). The last survey campaigns in the region in the late 1980s-early 1990s used this revised stratigraphical scheme (Zakharov et al., 1987; Pozdnyakov et al., 1992). As the result of research carried out the data on Silurian formations were collected and system­atized, lithological characteristics were described, and characteristic faunal elements were identified for objective geochronological dating of stratigraphic divisions. As the main outcome of the work, the local stratigraphic scheme was presented. Eight for­mations were assigned: Morosesti and Step-Soci Formations (Llandovery), Balti For­mation and Lower Puhoi Subformation (Wenlock), Upper Puhoi Subformation, Ichel Formation and lower parts of Chisinau Formation (Ludlow), upper parts of Chisinau Formation, Rashkiv and Zvenyhorod Formations (Pridoli).