THE present study deals with the geology of an area some 115 miles long and averaging about 33 miles wide along the Mediterranean coast in the Coastal Atlas of western Algeria. The strata are chiefly of marine sedimentary origin and range in age from late Paleozoic or early Mesozoic to Recent. Whereas numerous features of the general geology and geography are dealt with, the special emphasis concerns a discussion of the Cenozoic stratigraphic sequence and structural history, with particular reference to the Miocene and Pliocene periods, and the presentation of a geological map on the scale of 1/200,000. The map shows in detail the distribution of the formations representing the latter periods.
The region corresponds with the central portion of a Tertiary basin which, although subject to strong orogenic movements, received in successive epochs a great volume of sediments. To some extent the basin structure has persisted, and surrounding, as it does, the depressed areas of the Chelif and Habra plains, the region may be broadly referred to as the Chelif-Habra basin.
LOCATION OF REGION
From a district some 100 miles west of the city of Algiers the region extends southwestward to within 10 miles east of the city of Oran. It may be roughly described as the belt extending parallel with the coast from the towns of Ténès and Orleansville on the east to the vicinity of the towns of Arzeu and Mascara on the west. Its location and general features are shown on the key map (Fig. 1).