REARRANGEMENT OF RIVER NETWORK AND DIRECTION OF WATERSHEDS DISPLACEMENT IN THE MIDDLE VOLGA REGION AT THE QUATERNARY TIME

Abstract

The Neogene river valleys of the Middle Volga region are widespread, and their location mainly corresponds to the modern river network. This indicates the sustainability of development of river valleys during Neogene-Quaternary time. The Neogene river network was laid in the Late Miocene. The main rivers on the studied area were Paleo-Volga and Paleo-Kama. The article presents the results of the study of the value and direction of the displacement of modern valley’s cuts in relation to Neogene ones during Quaternary period within the territory of Tatarstan. The data on the displacement of the watershed lines are given. The material for the study was obtained on the basis of data analysis of the geological survey, literary and cartographic sources. Reconstruction of the position of the Neogene paleo-valleys was carried out using geoinformation mapping methods. The analysis of the displacement values of the modern valleys relatively to the Neogene ones allows us to conclude that in the Quaternary time the right-side displacement was predominant. The main factor which impacts on the displacement is Coriolis force. This is especially clearly seen on large and medium-sized rivers, where the value of displacement directly depends on the size of the watercourse. Displacement on large rivers averages 15 to 50 km, on medium-sized rivers - 12 to 15 km, on small rivers these values do not exceed 3.0 to 5.0 km. Changes in the main watershed lines in the Quaternary period are also associated with right-hand displacement. This trend is disrupted due to the increasing role of other factors, primarily lithological and tectonic. Namely these factors affect the left-side cuts offset, as well as the reduction or increase of the displacement value. The role of other factors is not so pronounced.