Conodont and crinoid stratigraphy of the upper Silurian and Lower Devonian scyphocrinoid beds of Tafilalt, southeastern Morocco

Abstract

Three sections (Atrous 3, Atrous 7 and Bou Tchrafine N2) in the “Scyphocrinites Limestones” of Tafilalt (southeastern Morocco) have been investigated for conodont and crinoid stratigraphy. Conodonts allow to discriminate four biozones (Ozarkodina eosteinhornensis s.l., Lower Oulodus elegans detortus, Upper O. elegansdetortus, and Icriodus hesperius) of Pridoli and the lowermost Lochkovian. Cirrus loboliths occur only in the Pridoli, whereas plate loboliths are present in the uppermost Silurian and the basal Devonian; the two types overlap in the uppermost Silurian. As for calices, Scyphocrinites and Carolicrinus occur in the whole Pridoli; Camarocrinus and Marhoumacrinus are present across the Silurian–Devonian boundary and in basal Devonian beds.

Keywords::

• conodonts
• crinoids
• stratigraphy
• Silurian
• Lower Devonian
• Morocco

Acknowledgements

This study would not have been possible without the detailed work of O.H. Walliser, who examined the sections and collected the conodont samples. Helga Groos-Uffenorde is deeply acknowledged for help in the preparation of the manuscript by examination of the conodont samples, maps, field notes and manuscripts in the asset of O.H. Walliser. Peep Männik and Stanislava Vodrážková improved the manuscript with useful comments. This research was partly supported by grants RAS (resp. C. Corradini). This paper is a contribution to IGCP projects numbers 591 (The Early to Middle Paleozoic revolution) and 596 (Climate change and biodiversity patterns in the Mid-Paleozoic).