Features of formation of deposits sedimentary cover of southwest part Caspian depression
Recurrence of accumulation of rainfall and formation of deposits of a sedimentary cover of the largest positive tectonic structure of Caspian Depression - Astrakhan Anticline is considered. The analysis of the extensive geological material received in the course of production of prospecting works in the second half of the 20th century and now allows to restore the course of accumulation of deposits and to reveal regularities of distribution of deposits of hydrocarbons on a section. Within the territory of Astrakhan Anticline the orogenny stage of development has ended in dorifeysky time with formation and consolidation of the crystal base. Geological age of breeds - archaean and Proterozoic. During рифея, Venda and the early Paleozoic there was a zalozheniye large палеоструктур various sign and formation of an intermediate doplatformenny sedimentary cover. The platform stage of development of the territory has begun in Devonian time and was followed by accumulation of deposits, various on lithologic structure. The analysis of the actual material has allowed to allocate in the territory of the Astrakhanksky arch four and the beginning of the fifth cycle of platform sedimentation. The first cycle of accumulation of rainfall within Astrakhan Anticline covers time period from an eyfelsky century of an average of Devon to the late Bashkir of a srednekamennougolny era. The second cycle has begun with the general immersion of the huge territory of Prikaspiya and was marked by formation in the Kungur time of the extensive solerodny pool. Duration of a cycle makes 72 million years, since an asselsky century of early Perm and finishing with the late Triassic. The third cycle has begun with the second half of an aalensky century and has ended at the end of the verkhneyursky period. The fourth cycle of sedimentation covers time period from a late valanzhin to a Miocene. Since a Pliocene there has come the newest fifth cycle of development of transgression and accumulation of mainly clay rainfall composing an integumentary cover.