The Cenozoic evolution of the South Caspian Basin: application of basin analysis and numerical modeling

The South Caspian Basin is a part of the northern, Crimean – Caucasian – Kopetdagh branch of the Alpine – Himalayan fold-and-thrust belt. Together with the adjacent Rioni – Kura intermontane depression, it spatially separates the Crimean – Caucasian, Lesser Caucasus – Binalud, and Kopetdagh fold-and-thrust systems. The study concerns the key aspects of structural formation and Cenozoic evolution of the South Caspian basin through application of basin analysis supported by digital modelling.

The tectonic structure of the basin was examined, and the position of its pre-Cenozoic western tectonic boundary was specified. Structural modeling results indicate a high concentration and pronounced variability of fold-related dislocations within the stratigraphic interval extending from the top Mesozoic to the modern seafloor. These deformations are especially developed around the mud volcanoes. The folding exhibits a uniform structural style and consistent geometry across all depth levels, suggesting a common origin related to Pliocene – Pleistocene tectonic activity.

Recent research using high-resolution seismic data does not confirm the existence of the Western Caspian deep fault within the structural framework of the Kura intermontane depression. Accordingly, the Saatly – Talysh zone of Mesozoic uplifts may be interpreted as the western boundary of the South Caspian basin until the end of the Mesozoic, after which this boundary progressively migrated westward in the direction of the Black Sea.

Folding within the South Caspian basin is primarily controlled by the redistribution of the Oligocene – Lower Miocene Maykop Group clayey rocks of low-density and prone to plastic flow under the load of the overlying thick Upper Miocene – Pliocene – Pleistocene succession. Entirely, folding and faulting patterns in the basin are governed by regional geodynamic processes associated with compressional, extensional, and shear stress regimes and their interactions.

The structural configuration of Cenozoic folds which governs both hydrocarbon trap development and the efficiency of fluid migration pathways from source rocks, and together with favorable sedimentary, paleogeographic, thermodynamic, and other geological conditions, accounts for the high hydrocarbon potential of the South Caspian basin. This structural framework is particularly responsible for the exceptional commercial petroleum potential observed in the western part of the basin.