Analyse biostratigraphique des conodontes du Silurien supérieur de la zone de Rabat-Tiflet (nord-ouest de la Meseta, Maroc)

摘要: – Silurian sections from the Rabat-Tiflet area (northwestern Moroccan Meseta) have been systematically sampled for conodonts. The conodont faunas are characterized by two index species of European zonation (Ozarkodina sagitta and Ozarkodina remsceidensis eosteinhornensis) other north American (Kockelella stauros Kockelella variabilis). Recognition sagitta/stauros through lower variabilis zones in part limestone shale succession area, proves first time presence Wenlock below Ludlow-Pridoli, sequences this area. Most northwestern Meseta is represented black graptolitic shales with intercalations (beds or lenses) its upper part. biostratigraphy Morocco generally based on graptolites [Willefert Destombes et al., 1985]. In present contribution age some (fig. 3) re-assessed using stratigraphically important taxa described Benfrika [1999]. Section Oued Grou I (G I) Situated near barrage Mohamed Ben Abdellah, section shows 30 m alternating limestones. unit (I) provided : sagitta, absidata, stauros, bohemica, excavata, Dapsilodus obliquicostatus, Panderodus unicostatus, Pseudooneotodus bicornis. appearance Oz. K. indicates boundary Zone established Walliser [1964] Carnic Alps also proposed Barrick Klapper [1976] North America 2). These age. II II) This located at approximately a hundred meters preceding section. It subdivided into 2 units • Unit IIA 12 greyish to limestones interbedded green ; IIB 65 conodonts identified A absidata stauros. fauna occurrence sample variablis zone (lower Ludlow). Al Khaloua Iron Mines (AK) yield Polygnathoides emarginatus variabilis. association Ludlow (Caudicriodus sp. Belodella devonica) indicate Lower Devonian Tiflet syncline (T) Two recognized 18 providing Decoriconus fragilis, excavata. Upper B 34 intercalations, probably Ludlow-Pridoli Bull. Soc. geol. Fr., 2003, t. 174, n o 4, pp. 337-342 4 Universite Hassan IIMohammedia, Faculte des Sciences M’Sik, Departement de Geologie, BP 7955, Sidi Othmane, Casablanca, Maroc (benfrikael@hotmail.com medraji@hotmail.com) Manuscrit depose le 29 mai 2002 accepte apres revision 7 fevrier 2003.