Le Crétacé inférieur dans le Massif de lʼOuarsenis et les Monts de Tiaret (Algérie du Nord)

Abstract

The Lower Cretaceous sediments in the Monts de Tiaret (Oranian High Plains) (Tlemcenian Palaeogeographic Domain) and the Western Ouarsenis (Tellian Palaeogeographic Domain) are subdivided in lithostratigraphic units which differ for the Tlemcenian and the Tellian Domains. In the first one, a specific feature is the development of shalow, and in the second – of deep water sediments. The following formal lithostratigraphic units are distinguished in the Tlemcenian Domain: (1) Remaïlia Carbonate Formation – limestones, marls and dolomites (Berriasian – Early Hauterivian (p.p.); (2) Berthelot Sandstone Formation (Early Hauterivien (p.p.) – Aptian); (3) Djebel Tenfeld Carbonate Formation – alternation of marls and limestones, rich in shallow water molluscs. Within the Tellian Atlas (Tell ian Domain) are distinguished: (l) Oued Fodda Carbonate Formation (Late Tithonian – Early Aptian); (2) El Melaab Turbiditic Formation (new unit of Aptian (p.p.) – Early Albian age) subdivided in 2 new Members: (a) Oued Sidi Mohamed Member (Aptian) – marls with turbiditic sandstones – distal flysch; (b) Oued Mezdar Member (Early Albian) – sandstones with intercalations of marls – proximal flysch; (3) Rhedadoua Marls Formation (Middle – Late (p.p.) Albian; (4) Hassi ben Ziane Carbonate Formation – marls and limestones (Late Albian (p.p.) – Early Cenomanian). In the Chouala region crop out the allochtonous sediments of the Sidi Seba Achir Limestones-Marls Formation (new unit of Berriasian-Middle Aptian Age) subdivided in 3 new members: (a) Oued el Ouakal Member – alternation of marls and limestones (Berriasian – Valanginian); (b) Oued Malah Member - marls (Hauterivian); (c) Sidi Ounes Member – marls and limestones (Barremian – Middle Aptian). The region of the High Plains (Monts de Tiaret) was uplifted at the end of the Jurassic, and the Berriasian sea transgressed over it. The subsidence of the Tellian Domain continued since the Late Jurassic and became an area of turbiditic sedimentation during the Aptian-Early Albian. The sedimentation in the Tlemcenian and Tellian Domains continued without interruption into the Cenomanian.