Abstract
The measured ranges of 52 conodont taxa present in 7 Eifelian sections of the eastern Anti-Atlas in southern Morocco have been assembled by graphic correlation method into a chronostratigraphic framework. The Anti-Atlas regional composite developed in this study provides much higher stratigraphic resolution than the traditionally used conodont zonation. It allows a subdivision of the Eifelian into 65.7 composite standard units, derived from the Jebel Ou Driss section, which was selected as the standard reference section. The framework appears to have a linear fit to time, giving the first image of the relative duration of the conodont zones in the upper Emsian to lower Givetian interval. The costatus, kockelianus, and Lower varcus chrons appear to have lasted more than two times longer than the partitus, australis, and/or hemiansatus chrons. An alternative upper Eifelian–lower Givetian conodont zonation with zones of more equal duration is proposed. Several conodont index taxa in the Anti-Atlas area display an almost synchronous appearance, independent of facies conditions and shelf paleobathymetry.
The analysis by graphic correlation reveals significant differences in rate of sediment accumulation between the Tafilalt Platform, which had condensed sedimentation (≈2.5 m/m.y.), and the Mader Basin, characterized by rates up to 40 m/m.y.
