Late Early Devonian ostracodes from the Torkoz area (SW Morocco) and the Emsian/Eifelian boundary

Abstract

A new rich and diversified ostracode fauna from the Torkoz area (section Hassi Mouf South, Moroccan Anti-Atlas) is described and the ostracode distribution near the Early/Middle Devonian boundary is discussed. This ostracode fauna of a single limestone bed yields 32 taxa and is compared with the less-diversified ostracode fauna from an adjacent parallel section Hassi Mouf South as well as with a published conodont-bearing sample from section Torkoz. All three ostracode faunas are closely related, and therefore, the same latest Emsian age is postulated. Palynomorphs (acritarchs and prasinophytes) from section Torkoz support this late Early Devonian age and the scarce brachiopod fauna of the equivalent level from section Hassi Mouf South suggests a stratigraphical position very close to the Emsian/Eifelian boundary, probably latest Emsian. Zygobeyrichiasubcylindrica from a thin marly bed embedded in shales, slightly below the ostracode-rich sample from section Hassi Mouf South, and the conodonts of the patulus Zone from section Torkoz, favours the position of the Early/Middle Devonian boundary within the Yeraifia Formation and not in or on top of the Rich 4 Sandstone in the SW Dra Valley area as hitherto published. The latest Early Devonian ostracode faunas from the Torkoz area belong to the shallow-water Eifelian Ecotype of G. Becker. The new genus Karlingrella for Euglyphella? granulosa Blumenstengel, 1962 and the new species Quasillites (Beckjennites) gebeckeri are erected.