Tectonics and Subsidence Evolution of the Sirt Basin, Libya

Abstract

Backstripping analysis of 225 wells located within the Sirt Basin (Fig. 1) provide new constraints on the Sirt Basin development. Four coherent tectonic phases from Late Jurassic to present. The presentation of contour maps of subsidence and crustal stretching allows to visualize spatial and temporal stretching migration. A close match is observed with stretching phases documented for other African Basins consistent with discrete phases in the opening of the Tethys and Atlantic. Rifting and reactivation appears to be primarily controlled by the orientation of the basin and the underlying basement structure with respect to stress directions. The tectonic subsidence curves have also been forward modeled with an automated modeling technique to quantify variation in timing and magnitude of rifting. The analysis of the Sirt Basin presented in this paper shows that the Basin evolution is marked by at least eight rifting pulses (a-h) from Early Cretaceous to Early Eocene. For the first time this is documented in a detailed study, indicating that with an increased resolution in subsidence data a better resolution (and hence understanding) of the tectonic signal is obtained. The tectonic subsidence history of the Sirt Basin is characterized by pulsating periods of stretching alternated by periods of relative tectonic quiescence and thermal subsidence. Stretching started at the centers of the troughs and migrated towards the platform crests.