A palynological study of the Ordovician to Devonian sediments of the Anti Atlas, Morocco
Approximately 300 field and well samples from the Ordovician to Devonian interval of the Anti Atlas, Morocco have been prepared for palynological investigation. Of these, 118 were selected for detailed analysis based on the quality of the palynological recovery, an attempt to achieve the best stratigraphic coverage as possible from the material available and also based on the presence of macrofossil data. A rapid palynological preparation technique for observation by light microscopy has been developed to analyse thermally mature, brittle assemblages, such as those encountered. Reviews of the Acritarcha, the fossil Prasinophyta and the Chitinozoa are presented with discussion of their morphology, biological affinity and classification. Taxa from these groups are treated systematically with 389 described species recorded, assignable to 115 genera. A total of 71 unpublished forms are described in open nomenclature. Miospores; have also been recorded to enhance biostratigraphic resolution and environmental interpretation of the assemblages studied. The miospore taxa recorded are illustrated with their authors cited in the plate captions. Semi-quantitative analyses of the assemblages has enabled the recognition of 33 Palynological Associations from the Ordovician through Devonian based on the presence, absence and abundance of the tax & recorded. Cluster analysis of the samples has been undertaken to assist in the recognition and to quantify the similarity of the assemblages. The Ordovician field samples yielded poorly preserved assemblages from which 12 Associations are recognised. The Silurian to Lower Devonian field samples yielded moderate to well preserved assemblages despite the high thermal grade of the material. Twelve Associations are defined from this interval, the ages of which are all highly constrained by the generally rich graptolite assemblages. Nine Associations are recognised from the Devonian assemblages recovered from Well Oum Doul-I core samples. These assemblages are well preserved with abundant and often diverse marine and terrestrial elements present. 'Me age interpretations of the 33 Associations are based on both macrofaunal evidence, when present, and on comparison with previous palynological studies, primarily those from Northern Gondwana. A general palaeoenvironmental, interpretation of the formations studied is attempted from the semi quantitative analysis of the relative proportions of environmentally sensitive palynomorph groups and the relative proportions of morphotypes within palynomorph groups. The major bathymetric fluctuations in the environment of deposition which are evident from the palynological, assemblages (e.g. the deep water event in the early Silurian) are believed to be eustatically controlled during the Ordovician to Devonian in the Anti Atlas. The broad nature of the study, geographically and stratigraphically, has revealed much potential for future work, of both academic and commercial interest, in the North African and Middle East region.