Numerical reconstructions of thermal evolution of sedimentary cover and underlying lithosphere in western part of the South Caspian Basin

Abstract

Thermal evolution of the South Caspian sedimentary basin since the Upper Triassic is numerically reconstructed on the example of the deepest sedimentary sections of the South Apsheron and Pre-Alborz depressions. The modeling suggests thermally active mantle of the region with present-day depth of the asthenosphere top of 50–60 km. The temperature at the base of the sedimentary cover at depth of about 20 km is estimated by 400 to 500 °C. The abnormally low temperatures of sedimentary rocks in the upper 5–6 km of the present-day sedimentary cover are in contrast with high temperature regime of the upper mantle in the region. These low temperatures are explained by high effective thermal conductivity of the rocks in the upper 5–6 km of sedimentary cover in conditions of avalanche sedimentation. It is believed that the considerable increase in effective heat conductivity of sedimentary rocks took place during the last 0.5–1 million years and can be due to contribution of the dispersional heat transfer. The latter is effective in deconsolidate upper layer of sediments deposited with high rate of sedimentation during last 2–5 My.