Le Jurassique dans les Monts de Tiaret et de lʼOuarsenis occidental (Algérie). II. Paléogéographie

Abstract

At the end of the Triassic and the very beginning of the Jurassic the region of the Monts de Tiaret and the Western Ouarsenis was a part of an emerged zone of Gondwana. The formation of the southern branch of the Tethys started during the Jurassic, when the region was situated at the limit between this southern branch of the Tethys (Tellian palaeogeographic Domain) and the margin of the platform of the High Plains (Tlemcenian palaeogeographie Domain) - transitional realm between Gondwana and Tethys. The region of the High Plains (Monts de Tiaret), northern part of the Tlemcenian paleogeography Domain subsided during pre-Callovian Jurassic times when the Tellian Domain was uplifted. Since Callovian time a tectonic inversion took place - the Tellian Domain started to subside, and at the end of the Early Cretaceous became a region with turbiditic sedimentation. During the Mid-Cretaceous (Austrian) tectogenesis the Tellian Domain subducted partially bellow the Tlemcenian Domain when the nappe outlier of Kei Sidi Amar was formed by backthrusting. It overthrusted the para-autochthonous region of the pics of Sra Sidi Abdelkader, Belkeiret and Rachael Alba, and structured the highest pic of Ouarsenis.