Emsian tabulate corals of Hamar Laghdad (Morocco): taxonomy and ecological interpretation

The taxonomy of tabulate coral assemblages from Emsian deposits of Hamar Laghdad, Morocco, was studied for the first time in detail, with attribution of the tabulate taxa to different facies. The studied coralla come from the famous Kess-Kess mud mounds (early Emsian, inversus conodont zone) and from the mound-covering unit of marly shales and nodular limestones of the Amerboh Group (late Emsian, serotinus and patulus conodont zones). Additionally, tabulate corals from the small caves and cavities related to hydrothermal venting occurring within the Kess-Kess mounds (inversus to serotinus conodont zones) are described for the first time. Emsian tabulates of Hamar Laghdad are characterised by a moderate diversity; 16 genera and 22 species (three new, twelve in open nomenclature) were identified. The assemblages of the Kess-Kess mounds and cavities are dominated by auloporids and pachyporids and share many similarities. The assemblage of the Amerboh shales is distinctly different from the remaining two as it consists predominantly of favositids and pachyporids. The driving factor behind the shift in tabulate faunas of Hamar Laghdad was likely the change of characteristics of sedimentation to more argillaceous in the Late Emsian. The prevalence of pachyporids and other branching and ramose tabulates could illustrate their adaptation to higher sedimentation rates, a constant feature in the Emsian strata of Hamar Laghdad.