CONODONT-BASED QUANTITATIVE BIOSTRATIGRAPHY FOR THE EIFELIAN OF THE EASTERN ANTI-ATLAS, MOROCCO

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 A nti-Atlas regional composite developed in this study provides much hig her stratigraphic resolution than the traditionally used conodont zona tion, It allows a subdivision of the Eifelian into 65.7 composite stan dard units, derived from the Jebel Ou Driss section, which was selecte d as the standard reference section. The framework appears to have a l inear 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 hemian satus chrons, An alternative upper Eifelian-lower Givetian conodont zo nation with zones of more equal duration is proposed, Several conodont index taxa in the Anti-Atlas area display an almost synchronous appea rance, independent of facies conditions and shelf paleobathymetry. The analysis by graphic correlation reveals significant differences in ra te of sediment accumulation between the Tafilalt Platform, which had c ondensed sedimentation (approximate to 2.5 m/m.y.), and the Mader Basi n, characterized by rates up to 40 m/m.y.