Stratigraphic succession (Albian to lower? Cenomanian) and upper Albian ammonites and biozones from the Talerhza Basin (South Riffian Ridges, northern Morocco)

Abstract

Lithostratigraphical analysis of more than ten sections of the El Mizab Formation (Talerhza Basin), previously assigned to the "Vraconnian" lead to distinguish a similar succession of five members, called from oldest to youngest: Silty marly limestones; Lower shelly marly limestones, Platy limestones, Upper shelly marly limestones and Marly limestones with Rhynchostreon. The lower and middle parts of the second member yielded a rich ammonite fauna of Mortoniceras (Mortoniceras) pricei and Mortoniceras (M.) inflatum zones, including: Hypengonoceras faugeresi sp. nov., Mortoniceras (Deiradoceras) aff. albense Spath, Mortoniceras (D.) bipunctatum Spath, Mortoniceras (D.) cunningtoni Spath, Mortoniceras (Mortoniceras) pricei (Spath), Mortoniceras (M.) inflatum (Sowerby) and Oxytropidoceras (Tarfayites) cf. bituberculatum Collignon. The upper part of the same member and the lower part of the fourth one yielded rare Mortoniceras (M.) fallax (Breistoffer) and Mortoniceras (M.) pachys (Seeley) of the Mortoniceras (M.) fallax Zone. The first member, having not yielded any ammonites, may have an early late Albian age, probably within the Dipoloceras cristatum Zone? The fifth member, rich in Rhynchostreon suborbiculatum (Lamarck), could be early? Cenomanian in age. The two underlying formations, El Heitouf and Bab Lkarma, previously assigned to the upper Albian (Mortoniceras inflatum Zone), could have an early to middle Albian age. The collected ammonites are studied and illustrated in the present contribution.