Ammonite biostratigraphy for the middle–upper Oxfordian of northwestern Algeria
Abstract
An ammonite biostratigraphy for Oxfordian in the Tlemcenian domain (northwestern Algeria) belonging to the south Tethyan margin is presented. It is based on the study of many sections located near Takhemaret and Frenda cities (Province of Tiaret). From bottom to top, the following biozones and subzones are distinguished: (i) Liosphinctes plicatilis Zone subdivided into the Cardioceras vertebrale (including the Otosphinctes arkelli Horizon) and Dichotomosphinctes antecedens subzone (including the Dichotomosphinctes antecedens Horizon); (ii) Gregoryceras transversarium Zone subdivided into four subzones: Perisphinctes parandieri, Dichotomosphinctes luciaeformis (its presence is doubtful), Larcheria schilli and Dichotomoceras rotoides subzones; (iii) Dichotomoceras bifurcatus Zone subdivided into two subzones: Dichotomoceras stenocycloides Subzone including the Dichotomoceras bifurcatoides Horizon, and the Dichotomoceras grossouvrei Subzone. The obtained results are compared and completed with those of Bou Rheddou and Bechtout (northern Tiaret city). The recorded biozones are very similar to the standard biozonation of the Upper Jurassic recognized throughout the Mediterranean region.