STRUCTURAL FEATURES OF THE SOUTH-WESTERN EDGE OF THE EAST- EUROPEAN PLATFORM IN THE CONTEXT OF INTERWAR RESEARCH (1918-1939)
Authors: Syvyi Myroslav 
Published: July 2021

During the Polish occupation between the First and Second World Wars, scientific and exploration work in Western Ukraine was carried out by Polish, Ukrainian, Czech and Hungarian researchers. The Carpathian folded region, the Precarpathian boundary deflection, the Transcarpathian inner deflection and the Volyn-Podillia outskirts of the East European platform were studied. The main areas of research were the Carpathians and Precarpathians in connection with the discovery and development of deposits of liquid and gaseous hydrocarbons discovered here, which attracted the attention of researchers for obvious reasons. The main research conducted during this period was organized by the Geological Institute (Warsaw) and the Carpathian Geological Institute (Boryslav). No special studies have been conducted to study the structure of the Volyn-Podillia part of the East European platform at that time. After thorough work of Laskarev V.D. in 1904-1914, works which dealt mainly with local issues of tectonics appeared. This, however, significantly supplemented the existing ideas about the structural features of the region.

A brief overview of studies of the structural features of the East European platform southwestern margin allows us to state the following.

The most significant achievements in studying the structure of the described region were noted by such researchers as W. Teisseyre, V. Zykh, G. Teisseyre, Z. Pazdro, S. Nazarevych and others. Thus, as early as 1922 famous Polish tectonist Wawrzyniec Teisseyre proposed to consider the Holohory-Kremenets anticlinal and the Holohory flexure as independent units. They are associated with the migration of the geosynclinal axis of the Carpathians, ie with the division of the Carpathian chain into three rings (meso-, eo- and neo-Carpathians). By studying the tectonics of the foothills, he also singled out the chronological phases of migration. Comparative studies have revealed cycles of development of Precarpathian dislocations in the foothills. The initial stage of flexure development is a flat roof-like elevation preserved on the Podillia plate, with the Holohory-Kremenets anticlinal on the edge. The processes of change and disintegration of such anticlinales cause the formation of later Holohory flexures and extensive deflections. Developing his views on the decisive role of the foundation in the structure of mountain ranges and the important role of tectonic dislocations (flexures, discharges) in the nature of platform tectonics, he emphasized that transverse dislocations are the manifestation of displacements in the deep base.

Russian tectonist M. Tetyaev suggested that the structure of the Transcarpathian territory is determined primarily by the folded zone of hercinide, which limits it from the west. According to him, the East European platform near the Carpathians is broken by discharges and partially hidden under the structures of the alpine fold. Ye. Oppokov, who studied the geological structure of the Devonian Podillia (Polissia) shaft, comes to the conclusion about its tectonic nature (anticlinal fold). A. Zirgoffer had a different opinion. According to the study of the relief, he believed that the Podillia shaft is a kind of barrier between the Volyn Plain and the Podillia Upland and was formed due to erosion processes.

In 1928, S. Nazarevych suggested the influence of folding on the occurrence of rupture in Transnistria. According to the author the folding of gypsum, fracture of rocks of different ages (from Silurian to Neogene inclusive), the direction of the Dniester, coinciding with the main cracks, the shape of cracks may be the evidence of vigorous movements of the earth's crust, which may be the result of those mountain-building processes, which reached the maximum stress in the third age and formed Carpathians in the West.

W.Teisseyre considers the fundamental issues of epeirotectonics. Based on the study of extensive Polish and foreign literature, he concludes that the network of epeirogenic lines does not correspond to the arcs of mountain ranges, and vice versa - the arcs enter at the intersection of different ages. The author opposes the understanding of epeirogenesis in the form of giant sea waves. W.Teisseyre believed that Podillia is one of the main nodes of the mountain movements of Eastern Europe. Within the Precarpathians, deep ridges and depressions are considered, established mainly according to geophysical data (Bibrka - Mykolayiv, Rozdil - Demnia, Kavske - Opary, Stara Sil - Zhuravno, etc.). From the point of view of oil and gas exploration, preference is given to the Precarpathian part of the Holohory-Kremenets-Boryslav line, then to the Dniester-Stryi basin and to the more ancient epeiroanticlinal line Smykivtsi-Kovalivka-Hrabivka-Maidan (“Stanislaviv Horst”). The importance of Transcarpathian anticlines in the search for oil and gas fields is emphasized. It is noted, in particular, that the uplift of Boryslav and Maidan - the main productive areas of the Carpathian oil and gas zone - coincides with the axes of the Podillia-Transcarpathian anticlines Holohory - Kremenets and Smykivtsi - Kovalivka.

Some conclusions and generalizations were made by researchers in the interwar period (on the decisive role of the crystalline basement in the structure of mountain ranges, on the inheritance of ancient forms of the foundation surface and the chalk surface with modern relief, identified anticline uplifts in Paleozoic sediments and their oil and gas potential, on the coincidence of the axes of the Transcarpathian anticline uplifts and the main productive areas of the Carpathian oil and gas zone, etc.) have not lost their scientific value in our time and are confirmed by modern research.

Studies in the 1920s and 1930s of the tectonic structure of the southwestern outskirts of the ancient East- European platform contributed to the formation of a reliable basis for the establishment and conduction of extensive exploration (oil and gas, coal, sulfur, salts, phosphorites, building materials, etc.) and systematic research in the postwar years.

Key words: East European platform, tectonic structure, anticlinal uplifts, crystalline basement.