ПРОИСХОЖДЕНИЕ “ВРЕЗАННЫХˮ ИЛИ СЛЕПЫХ ДЕЛЬТ НА ВОЛГО-УРАЛЬСКОМ МЕЖДУРЕЧЬЕ В СВЕТЕ НОВЫХ ПРЕДСТАВЛЕНИЙ ОБ ИСТОРИИ КОЛЕБАНИЙ УРОВНЯ КАСПИЯ

Abstract

The relief of the Volga-Ural interfluve is considered, where the rivers in the mouths form “embedded” or blind deltas. These deltas terminate close to the Volga-Ural Sands. During spring snowmelt floods, large lakes appear at the mouths of rivers. Therefore, it is difficult to agree with the opinion that the rivers disconnected from the sea during the regression phases due to the low water levels in rivers. Sea regression led to the downcutting of the delta channels into the alluvial and marine deposits. Analysis of the outcrops, taking into account the coastal geomorphology and the impact of the sea level fluctuations on the coast has led to the conclusion that there was no deep Atelian regression and Great Early Khvalynian transgression. It was a Great Khazarian transgression, after which lagoon-transgressive terraces formed sequentially at the background of the gradual lowering of the Caspian Sea. Positive oscillations of sea level led to the formation of lagoons, where the chocolate clays accumulated. All tributary rivers formed deltas that prograded into such lagoons. Therefore, Sea the rivers could not follow the coastline during the subsequent lowering of the Caspian Sea. The shallowing of the lagoons resulted in the drainage of the deltas. When the water level in the lagoons dropped, rivers cut in deltaic deposits and “embedded” or blind deltas were formed.