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Geological Society, London, Special Publications; 2007; v. 275; p. 51-70;
DOI: 10.1144/GSL.SP.2007.275.01.04
© 2007 Geological Society of London

Botoman (Lower Cambrian) turbid- and clear-water reefs and associated environments from the High Atlas, Morocco

J. Javier Álvaro1,2 & Sébastien Clausen2

1 Departamento Ciencias de la Tierra, Universidad de Zaragoza, Ciudad Universitaria, 50009-Zaragoza, Spain
2 LP3, UMR 8014 CNRS, Université des Sciences et Technologies de Lille, 59655-Villeneuve d'Ascq, France (e-mail: Jose-Javier.Alvaro{at}univ-lille1.fr)

Exposures of the Botoman (Lower Cambrian), Lemdad and Issafen formations on the Lemdad syndine, southern High Atlas, provide an excellent example of the interactions between tectonic events, magmatic activity and carbonate productivity. The major factors that controlled the nucleation of carbonate factories on the Botoman High Atlas platform were: (i) synsedimentary tectonism, as normal faulting resulted in tilting of fault blocks causing irregular topographies and subsequent sharp erosion; (ii) volcanism, because pyroclastic influx smothered carbonate factories except in distal areas of the platform or during quiescent episodes of volcanic activity; and (iii) the influence of successive shoaling parasequences. The Botoman reefs exhibit a wide range of external morphologies, including tabular (biostromes) and domal (bioherms and patches) boundstones, which do not exceed 3.5 m of thickness. Although archaeocyathan-microbial reefs only developed under clearwater conditions, microbial reefs grew also under turbid-water conditions. Domal and digitate stromatoids, Girvanella crusts, Epiphyton bushes and thromboid-stromatoid intergrowths document the ability of some microbial communities to develop heterotrophic strategies when submitted to a moderate terrigenous input. Turbidity was a major ecological factor that constrained development of filter/suspension-feeder and phototrophic organisms, but not necessarily of benthic non-phototrophic microbial communities.





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J. J. Alvaro, M. Macouin, H. Ezzouhairi, A. Charif, N. A. Ayad, M. L. Ribeiro, and M. Ader
Late Neoproterozoic carbonate productivity in a rifting context: the Adoudou Formation and its associated bimodal volcanism onlapping the western Saghro inlier, Morocco
Geological Society, London, Special Publications, 2008; 297: 285 - 302.
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