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Władysław Pożaryski

Abstrakt


THE VARISCAN STAGE OF PLATFORM TECTONICAL DEVELOPMENT OF THE MIDDLE EUROPE

Summary
The major tectonic elements of the basement, rejuvenated at the Variscan stage of tectogenesis, include Early Proterozoic directions NE - SW in eastern Poland and Byelorussia, Late Proterozoic Kock Fault, and Early Caledonian strike-slip fault, called as Trans-European Fault and representing SW margin of the East-European Platform. In the Middle Devonian a microplate representing SW corner of the East-European Platform became broken-off of the rest of the platform and slightly offset to the west. This was connected on the one hand with origin of a continental rift and alkaline-ultramafic volcanic activity in the Dnepr Trough and, on the other hand, origin of a system of fan-like sublatitudinal fractures west of northern end of that trough. This was the reason of development of W - E oriented strike-slip Płońsk-Mikaszewicze fault (PM), running along the axis of fan- like fracture system and delineating the mobile microcontinent in the north. The fault has been traced in central Poland, where it is responsible for breaking and sinistral offset of TEF, representing the platform margin. This and other strike-slip faults have been identified in part on the basis of the nature of derivative faults from higher levels, with reference to theory recently put forward by W. Jaroszewski.
In the Bretonian phases, the westward movement of the microcontinent ended and volcanic activity ceased in the Dnepr Trough. In connection with collision in the geosyncline in the south, the microcontinent became subjected to a NWN oriented stress. This resulted in strong deformations in area south of PM, in zones bounded by the fan- like fractures, and the strike-slip Krasnystaw-Włodzimierz Wołyński fault (KWW) at western extension of southern margin of the Prypeć Depression, due to squeezing out of a wedge-like block to the west; along PM and KWW. The Lublin part of this wedge-like block, bounded by the Kock Fault and platform margin, underwent rotation and a small rift opened for a short time in the vicinities of Lublin in the Visean, leading to a rise of basic magmas. Fan-like dislocations enter south-western foreland of the East-European Platform in Poland and Baltic area. PM marks northern boundary of the Variscan orogen, and the Grudziądz dislocation (G) coincides with the margin of the platform. Western dislocation zone of marginal anomaly in Moho is rectilinear and may be interpreted as the Skania-Masyw Małopolski strike-slip fault (SMM). The latter represents eastern boundary of shows of epi-Variscan bimodal volcanic activity. A wide zone of NWN - ESE oriented epi-Variscan derivative faults originated above SMM. It should be noted that these faults• were repeatedly rejuvenated in the Mesozoic times.

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