Subsidence history and basin-fill evolution in the South Caspian Basin from geophysical mapping, flexural backstripping, forward lithospheric modelling and gravity modelling

Abstract

AbstractThis study summarizes the subsidence history and aspects of the geodynamic evolution of the South Caspian Basin based on the integration of geophysical observations, and subsidence and gravity modelling on selected two-dimensional (2D) profiles. This analysis implies the presence of an attenuated ‘oceanic-type’ crust in the northern portion of the South Caspian Basin, demonstrates characteristics of basin subsidence on variable crustal types and describes sediment-fill evolution in several different parts of the basin. Modelling conducted in this study shows that the observed pattern of subsidence and sedimentation in the South Caspian Basin can be explained by a process of thermal subsidence following Jurassic rifting and further enhanced subsidence that resulted from sediment-induced loading in the Late Tertiary, especially after a large-scale base-level fall after 6 Ma.Variation in crustal type is reflected in differences observed in the degree of subsidence and sediment fill in the overlying stratigraphy. The western part of the South Caspian Basin has subsided differently to the eastern part because of this difference in crustal type. This is also confirmed by gravity modelling, which shows that the South Caspian Basin crustal density is compatible with an oceanic composition in the western part of the South Caspian Basin: the crust in the eastern part of the basin, however, is thicker.