Emsian and Eifelian ammonoids from Oufrane, eastern Dra Valley (Anti-Atlas, Morocco) – taxonomy, stratigraphy and correlation
Abstract:Emsian and Eifelian ammonoids from four lateral sections at Oufrane, Tata area, western Dra Valley (Anti-Atlas, Morocco), are described and compared with contemporaneous assemblages from other areas of the Anti-Atlas. Upper Emsian faunas are assigned to the successive Sellanarcestes wenkenbachi Zone (LD IV-C), Anarcestes simulans Subzone (lower LD IV-D1, with Sell. neglectus and Achguigites tafilaltensis as additional marker species), and An. crassus Subzone (upper LD IV-D1). The Lower/Middle Devonian transition falls in a poorly exposed interval without critical ammonoids or other fossils. Subsequent lower Eifelian Pinacites jugleri (MD I-C) and Subanarcestes macrocephalus zones (MD I-D) can be distinguished. The upper Eifelian is mostly covered and poorly fossiliferous. The Oufrane succession allows easy correlation with the Tafilalt to the East but an overall lower diversity suggests a facies-controlled, limited exchange of nekton between both areas. An increased westward restriction of faunal exchange is supported by preliminary data from the western Dra Valley and was probably caused by the gradual shallowing of the environment. There are 18 species belonging to ten genera (Latanarcestes auct., Sellanarcestes, Anarcestes, Achguigites, Fidelites, Pinacites, Subanarcestes, Sobolewia, Werneroceras, Clarkeoceras). Sell. draensis n. sp., Ach. hidens n. sp., Cl. oufranense n.sp., Sob. chouberti n. sp., the Achguigitidae n. fam., and the Chlupacitinae n. subfam. (Agoniatitidae) are established. Selection of a lectotype for the widely ignored An. crassus (Barrande, 1867) renders An. latissimus Chlupáč & Turek, 1983 to be an objective junior synonym. Sell. tenuior Walliser, 1965 is regarded as a subjective junior synonym of Sell. applanatus (Frech, 1897). Distributions in time and space of all species are compiled. Close similarities between NW Gondwanan and European faunas characterize the western Protethys, which had a limited exchange of certain species with Asia and only very poor faunal links with North and South America.
Document Type: Research Article
Publication date: 2011-03-01
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