Deep Structure and Geodynamics of the South Caspian Basin

The geological and geophysical data available on the structure of the South Caspian Basin suggest that the upper mantle of this region includes a thick low velocity presumably fluid-saturated layer descending from the Apsheron Threshold under the Alborz Ridge. This zone may correspond to the upper sedimentary layer of the subduction zone connected with subduction of the South Caspian basin beneath the Alborz Ridge. The fluid-saturated layer appears to be the main source of deep aqueous and hydrocarbon fluids connected with the formation of marine seeps, mud volcanoes, and oil-gas reservoirs numerous in this region. The active discharge of the deep fluids in connection with the strong dependence of intensity of the deep fluid flows from the permeability of the corresponding deep fault zones can explain such phenomena as a power-law distribution of the gas and oil field stocks in different deposits and a process of recent refilling of oil and gas reservoirs.