Discovery of themessaoudensis–trifidumacritarch assemblage (upper Tremadocian–lower Floian, Lower Ordovician) in the subsurface of Morocco

T Servais,M Akodad,H Nowak,B Lefebvre

doi:10.3176/earth.2015.14

Abstract

The upper Tremadocian to lower Floian messaoudensis-trifidum acritarch assemblage was first described from the Skiddaw Group of England and subsequently from several localities on the Gondwanan margin that were positioned in high southern latitudes during the Early Ordovician. It is here reported for the first time from North Africa, from the Fezouata formations (Tremadocian to Floian) in the AZ-1 borehole, southeastern Morocco. The assemblage is comparable with that from the Skiddaw Group, with Cymatiogalea deunffii, C. messaoudensis, C. velifera, Caldariola glabra glabra, Stelliferidium trifidum and Veryhachium lairdii s.l. The Moroccan assemblage indicates a late Tremadocian age.

Highlights

The messaoudensis–trifidum acritarch assemblage is known from upper Tremadocian to lower Floian (Lower Ordovician) strata in many localities on the Gondwanan margin (Servais et al 2003)
It was first described as the ‘Watch Hill assemblage’ from the Watch Hill Formation of the Skiddaw Group in the English Lake District by Molyneux & Rushton (1988)
The assemblage has not been effectively reported from North Africa, Cymatiogalea messaoudensis was originally described from the Algerian Sahara (Jardiné et al 1974)

Summary

INTRODUCTION

The messaoudensis–trifidum acritarch assemblage is known from upper Tremadocian to lower Floian (Lower Ordovician) strata in many localities on the Gondwanan margin (Servais et al 2003). It was first described as the ‘Watch Hill assemblage’ from the Watch Hill Formation of the Skiddaw Group in the English Lake District by Molyneux & Rushton (1988). Snape (1993), in an unpublished PhD thesis, recognized an association comparable to the one reported by Molyneux & Rushton (1988), marked by the co-occurrence of Cymatiogalea deunffii, C. messaoudensis, Stelliferidium trifidum and Vogtlandia coalita Martin in Dean & Martin, 1978, from surface samples of the Moroccan Lower Fezouata Formation. Palynomorphs from the Fezouata formations have previously been studied by Deunff (1968a, 1968b, in Destombes et al 1985), Elaouad-Debbaj (1984, 1988) and Snape (1993)

MATERIALS AND METHODS

RESULTS

DISCUSSION