--> Abstract: The Saharian Atlas (North Algeria): An Example of an Inverted Basin, by R. Villay, J. Letouzey, F. Benard, N. Haddadi, G. Desforges, H. Askri, and A. Boudjema; #90987 (1993).

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VILLAY, ROLAND, J. LETOUZEY, and F. BENARD, Institut Francais du Petrole, Rueil-Malmaison, France; N. HADDADI and G. DESFORGES, Total Algerie, Alger, Algeria; and H. ASKRI and A. BOUDJEMA, Sonatrach Exploration, Hussen Dey, Alger, Algeria

ABSTRACT: The Saharian Atlas (North Algeria): An Example of an Inverted Basin

The Saharian Atlas is located between the Tellian domain (in the North) which is a segment of the Tethyan paleomargin and the Saharian platform (in the South), relatively stable since the end of the Paleozoic.

In the western part of the Saharian Atlas (between the Moroccan border and the Algiers meridian), the Mesozoic series begins with a thick Triassic evaporitic sequence which formed the major decollement level during the Tertiary compression. The extensional phase continued during the Early and Middle Jurassic, and resulted in the formation of a subsident intracratonic basin infilled with a thick Mesozoic series (7 to 9 km). To the north (Hauts Plateaux) and to the South (Saharian platform), this basin is bordered by relatively stable Mesozoic areas.

During the compressive phases (Tertiary), associated to the genesis of the peri-Mediterranean ranges, the extensional structures were reactivated into reverse faults; the evolution of the Atlas Mesozoic basin ended with the formation of the Saharian Atlas range, which is a typical inverted basin.

The structural study of the inverted structures includes integrated exploration well data, field data as well as an important seismic imagery. Using analogue modelling (X-ray tomography) we could specify the precise geometry and the dynamics of this type of structure. We could also underline the important influence of the pre-existing halokinesis on the structural style in the Atlas region. In addition, numerical modelling of the deformation (THRUSTPACK{R} software) gave us a new hypothesis about the in-depth geometry of the reactivated normal fault, especially in the transition zone between the Saharian Atlas and the Saharian platform (Saharian flexure).

All the results are discussed in terms of structural evolution, geologic history and petroleum exploration.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.