Литолого-фациальная модель бакинских отложений Астраханского Прикаспия

Abstract

The influence of fluctuations in the Caspian Sea level on the lithological and facies characteristics of sedimentary deposits is analyzed. Special attention is paid to the study of periodic changes in the water level in the Caspian Sea during the Absheron and Baku time in order to determine the effect of fluctuations on sedimentation processes. The Turanian regression was considered, and its differentiation with the Absheron and Baku transgressions was carried out. The study included the study of climatic conditions of past eras and their impact on the diversity of flora and fauna, which, in turn, had an impact on sedimentation processes in various periods of the Baku stage. Geological and statistical methods were used to determine the characteristics of reservoirs in sediments, as well as to study their distribution over the territory. A lithological and facies model has been constructed that reflects two cycles of regression and transgression characteristic of the deposits of the Baku time, which made it possible to describe the distribution of sandy and clay facies in various sections of the section and interpret a map of sandiness to identify buried river valleys. It is concluded that two lithofacies bundles reflecting the transgressive-regressive cycle of the Great Caspian Sea were identified in Baku time. Hypotheses have been formed according to which the reservoirs were formed in the final stage of the Turkic regression and were later covered with sediments of the Baku transgression. It has been established that these reservoirs play a significant role for gas accumulations and are distributed almost throughout the territory of the Astrakhan Caspian Sea. The identification of areas with a high reservoir content may be important for future exploration in this region.