Late Cretaceous and Tertiary subsidence history of the Sirte Basin (Libya): an example of the use of backstripping analysis

The results of a quantitative analysis of subsidence data from 20 wells covering six major basement blocks of the Sirte Basin (Libya) are presented. Tectonic subsidence curves were calculated from the stratigraphic record using backstripping techniques; these were subsequently used to derive subsidence rates in time. Extension started in the Late Cretaceous, followed by four distinguishable tectonic phases. The onset of extension coincided with the change of the Africa-to-Europe relative motion vector from eastward to westward. Intraplate stress variations and resulting isostatic rebound and downwarping of the lithosphere caused differential fault tectonics and regional uplift and subsidence during the Palaeocene-late Eocene. Termination of this phase in the late Eocene was a result of the change to westward plate motion of Africa. Subsidence and marine deposition continued until the early Miocene, when the stress regime changed to NW-SE compressional as a result of the pronounced northward movement of Africa relative to Europe. -Authors