Post-Paleozoic Deformation in the Triassic Basin, North Africa

J. S. Jackson, S. R. Moore, A. I. Quarles, and J. Bellis

The Triassic Basin of North Africa is a Tethyan rift basin crossing Algeria and Tunisia above portions of the Paleozoic Oued M'ya and Ghadames Basins. Paleozoic strata are deeply truncated at the "Hercynian Unconformity" on a broad arch between the older basins. This is interpreted to reflect rift margin rebound during Carboniferous time. Continental Lower Triassic sediments were deposited in a series of northeast trending grabens which opened as the Neo-Tethys basin propagated from east to west between Africa and Europe. Passive margin subsidence was associated with a marine transgression from the east that reached eastern Tunisia during the Late Permian, and extended into Algeria during the Middle Triassic. Resulting evaporite deposition persisted through the Early Jura sic and was succeeded by carbonate marine deposition through the Early Cretaceous. Several zones of Cretaceous and Cenozoic age inversion and wrench deformation cross the Atlas and adjoining regions, rendering paleogeographic interpretations of the northern Triassic Basin problematic. Strike-slip faulting and inversion occurred before the end of the Early Cretaceous in the Triassic Basin. This episode created discrete uplifts, where major hydrocarbon accumulations have been discovered along several northeast trending lineaments. During the Eocene, the main phase of the Atlas Orogeny produced low amplitude folding of Jurassic and Cretaceous sediments in the Triassic Basin, and added relief to existing inversion features.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California