Seismic Mapping, Stratigraphy and Subsidence in the South Caspian Basin, Azerbaijan

The South Caspian Basin is believed to contain more than 20 km of Mesozoic and Tertiary sediments deposited on oceanic or thinned continental crust. The Pliocene to Recent sequence has been mapped on a regionally extensive grid of 2D seismic data and penetrated by recently drilled exploration wells and is over 7 km thick. Most of this sequence (6 km) is formed of fluvial-lacustrine deltaic sediments of the Pliocene Productive Series that are deposited unconformably above a marine Miocene shale sequence and form the principal hydrocarbon reservoirs in the basin. The thickness of the Pliocene sedimentary sequence implies that relatively rapid, late Tertiary subsidence occurred in the South Caspian Basin. Modelling presented in this paper suggests that it is possible to account for the observed pattern of subsidence and sedimentation in the South Caspian Basin by a process of sediment loading and compaction on a thermally-subsiding, late Mesozoic crust. The Pliocene Productive Series is interpreted to have been deposited in a topographic depression, isolated from the global oceanic system, in which base-level was controlled by local factors rather than by global sea-level.