Features of the Structure and Development of the Southeastern Part of the East European Platform and the Caspian Basin i
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ures of the Structure and Development of the Southeastern Part of the East European Platform and the Caspian Basin in the Late Precambrian‒Early Paleozoic T. N. Kheraskovaa, *, Yu. A. Volozha, M. P. Antipova, V. A. Bykadorova, and I. S. Postnikovaa aGeological
Institute of the Russian Academy of Sciences, Moscow, 119017 Russia *e-mail: [email protected]
Received April 25, 2020; revised June 20, 2020; accepted July 28, 2020
Abstract—The geological and sedimentological interpretation of several time and deep seismic profiles within junction zone of the Volga‒Ural area of the East European Platform, Pre-Caspian Depression, Ural Foredeep, Bashkir Anticlinorium, and northern margin of the Scythian Platform allowed us to identify a number of previously unknown structural features of Later Precambrian and Early Paleozoic formation. On this basis, structural-facies maps were compiled for the Riphean and Vendian stages of development. It was shown that as a result of the collision of the southeastern passive margin of the continent Baltica with Scythia in the Early Vendian and with the Timanides of the Urals in the Later Vendian, a complex tectonic structure of the Orenburg tectonic node was formed, which forms the foundation of the Caspian oil and gas province. The results obtained substantially clarify the structure of the sedimentary cover of the East European Platform and the Pre-Caspian Basin, the stages of the formation and evolution of their structure, and the degree of inf luence on the sedimentation of structural changes in the adjacent territories of the folded Urals and the Scythian Platform. Keywords: seismostratigraphic complex, seismic section, consolidated crust, shelf, aulacogen, sea level fluctuation, erosial incision, debris fan DOI: 10.1134/S0016852120050052
INTRODUCTION The largest petroleum province is located within the southeastern East European Platform (EEP) and the adjacent Caspian basin. The emergence and preservation of hydrocarbon reservoirs within its limits depend on the geological events and tectonic features of particular structures that have formed at certain stages of its development. The region under study is a very complex junction of three large structures, namely, the EEP, the folded structure of the Urals, and the Scythian Platform. We have considered the Middle and Late Paleozoic evolution of this region earlier [26]. However, the main structural elements of the region nucleated in the Late Precambrian and Early Paleozoic. During this period, the Caspian sedimentary basin and its main peculiarities formed. However, due to the considerable depths (5‒8 km) at which Upper Precambrian and Lower Paleozoic complexes occur, their structure has been studied very fragmentarily until very recently. In recent years, large amounts of seismic data have been re-processed, and as a result, data quality has improved significantly. It has become possible to show the structure and composition of the Upper Precambrian–Lower Paleozoic depositional complex of the mentioned triple tectonic no
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