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Western Sahara Atlas of Algeria: Salt Diapirism, Orogenic Folding, and Hydrocarbon Potential

ROEDER, DIETRICH, The Anschutz Corporation, Denver, CO

The Sahara Atlas has been the Algerian part of the surface trace of the Europe/Africa convergent plate boundary since the early Oligocene. In its western segment, the structure of this detached fold belt is evident in surface mapping, in reflection seismic data, and in a finite plate-tectonic convergence of about 300 km. The northward slope at the Saharan foreland flexure of 5-8 degrees is consistent with northward thinning crust. Very large detached folds with minor thrusts are consistent with an 8 km thick, Triassic to Eocene, marine and non-marine, polyphase rifted, passive-margin series. The bulk strain in the fold carpet is only 30-40 km, but large folds near the foreland support the theoretical detachment of 130 km. Triassic and Lower Jurassic evaporites occur in nondiapiric ant clinal cores, in Neocomian salt pillows, and in Neogene to Holocene diapirs and fault laminae. The fold trend records the azimuth of plate convergence. The canted mountain-front trend follows an abrupt fault contact (of late Paleozoic or middle Cretaceous age) between Paleozoics on Saharan basement and Hercynian-type basement. The hydrocarbon potential of the Sahara Atlas depends on infolded rifts or aulacogens of early Jurassic age. The northward extension of the Saharan Paleozoic series into the Sahara Atlas is unlikely.

 

AAPG Search and Discovery Article #91007© 1991 AAPG International Conference, London, England, September 29-October 2, 1991 (2009)