Flexural plate subsidence, sedimentation rates, and structural development of the super-deep South Caspian Basin

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Flexural plate subsidence, sedimentation rates, and structural development of the super-deep South Caspian Basin

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Title: Flexural plate subsidence, sedimentation rates, and structural development of the super-deep South Caspian Basin
Author: Nadirov, R.S.; Bagirov, E.B.; Tagiyev, M.F.
Abstract: On a 270-km long seismic line across the west central and central parts of the South Caspian Basin an inverse flexural plate method is used to recover original uploaded plate parameters. The original plate shows remarkable consistency of parameters determined from the 12-second deep seismic line, with average rigidity D=1023.6Nm; bending moment M=1016N, dip angle Θ=−0.14°, and in-line compressive stress of 1012.3N m−1. By sequentially adding the sedimentary units to the average ‘bare’ basement, it is shown that the geometry of the basin at Jurassic time had a major downward warp, and high sedimentary fill to the west, leaving the eastern section open to possible erosion during Early and Middle Cretaceous time. The deep western part of the basin was then filled by sediments during late Tertiary/Quaternary time, and a new depocenter created across the central and western parts of the basin. This newer depocenter was then filled during Pliocene/Quaternary time. The combined flexure of the basement plate, and corresponding sediment fill behaviors with time, are indicative of corresponding lithologic variations across the basin and with suspected organic-rich sediments. The integrated description of basement, sediments, and depocenter behavior points to the utility of the inverse procedure for improving our understanding of basinal evolution. The value of rigidity is comparable to estimated oceanic crust values, in line with the suspected Tethys oceanic fragment of an island arc below the sediments. The shift in depositional behavior with time, from west to more northerly across the line of section, is tied to the orogenic rise of the Caucasus mountains to the north of the section, and to the continued subduction of the Talysh-Vandam plate fragment northward today. The transpressional nature of the basin, and the resolution of the in-line compressive stress into components perpendicular to the Great Caucasus (∼70%) and also perpendicular to the West Caspian deep-laid fault (25–30%), are both in accord with the 25–30 km of present day sedimentary cover, including the variations of thicknesses of seismic stratigraphic units along the section from Azerbaijan in the west to nearly the Turkmenian border in the east.
URI: http://hdl.handle.net/123456789/1434
Date: 1997-06


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