This image shows the Volga Delta and the northern part of the Caspian Sea, bright green and blue from sediments and phytoplankton. The sedimentation rates and the types of recent deposits in the Northern Caspian Sea are governed mainly by the abundant Volga discharge.
Investigations based on a complex of techniques revealed that the modern deposits in the Northern Caspian Sea involve terrigenous sands and aleurites with an admixture of detritus and intact bivalve shells, including coquina. Generally, these deposits overlay dark grayish viscous clays.
A similar geological situation occurs in the Volga delta; however, the local deposits are much poorer in biogenic constituents. Illite prevails among the clay minerals. The heavy transparent minerals are represented in the coarse aleurite fraction mostly by epidotes, while quartz and feldspars represent the lighter minerals. The sedimentary material in the Volga delta is far from completely differentiated into fractions due to the abundance of terrigenous inflows, which exceed the energy potential of the river (click here for more information).