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COMPARATIVE ANALYSIS OF TECTONIC STRUCTURES OF THE NORTH-EASTERN AND EASTERN FRAMING OF THE SIBERIAN PLATFORM (NORTH-EAST ASIA)

Dmitry Vasiliev

Abstract

The Verkhoyansk fold-and-thrust belt (VFTB), composed of terrigenous-carbonate rocks of the Upper Proterozoic, Paleozoic and Mesozoic age and formed in the Late Mesozoic time, stretches along the north-eastern and eastern framing of the Siberian platform. Studies were carried out (from south to north) in the Kuranakh and Kharaulakh segments of the Western-Verkhoyansk sector of VFTB and in the Olenek sector of VFTB. Structures of the Kuranakh and Kharaulakh segments have submeridional strike, and the Olenek ? sublatitudinal strike. As a result of performed researches, it was possible to define that, in general, all studied folds are asymmetric, cylindrical and belong to concentric type of folding. Cleavage occurs in the most deformed parts of the studied region. Obtained data indicate close genetic association between folds and cleavage and their formation in the same stress field. Bedding thrusts are the most common type among faults. These faults, crosscutting beds at a small angle, form gentle thrusts, which are transformed into reverse faults on increase of fault fissure dip subsequently. On limbs of the Chekurovka and Ust-Olenek anticlines of the Kharaulakh segment and the Olenek sector, respectively, back trusts are manifested. Shear fractures is widely spread. They form systems, which strikes are almost orthogonal to each other. They are longitudinal and transverse with respect to folding. Large faults have different kinematics. In most cases, they are represented by large thrust structures, such as the Chekurovka thrust of the Kharaulakh segment and the Tumul thrust of the Olenek sector. Series of such faults is observed at the southern limb of Central-Kharaulakh synclinorium and in the Kharaulakh anticlinorium of the Kharaulakh segment. In the north, at the southern limb of the Bykovsky anticlinorium, large faults, in general, have normal fault kinematics. The same large normal faults limit the Kengdey graben (Kharaulakh segment). There are later strike-slip faults of longitudinal trend with respect to early folding. It is supposed that, tectonic structures of the Kharaulakh and Kuranakh segments are formed above blind thrust duplexes. Study of seismic prospecting time profiles across the Eastern part of the Ust-Olenek fold system (Olenek sector) allowed confirming assumption that, it was also formed above blind thrust duplex. It is determined that, folded and thrust structures of the north-eastern and eastern folded framing of the Siberian platform were formed during one fold-and-thrust stage in the Cretaceous. This main tectonic event is subdivided into several stages. It is determined that, formation of thrusts had rear sequence and took place from west to east. According to constructed balanced cross sections, shortening of deformed rocks could be 20-30%.

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DOI resolver: doi.org/10.5593/sgem2018/1.1/s01.006

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