Microbialites and micro-encrusters role in the reefs lithification: examples of the Maghrebian Atlas reefs during the Upper Jurassic

In the Upper Jurassic, reefs from the Maghrebian Atlas, inter- and intraske letal cavities were infilled by microbialites associated with microencruste rs: Bacinella iregularis, Tubiphytes obscurus, Lithococdium aggregatum and encrusting forams. Microbialitic activity was the main lithifying agent in the reef framework both in the Tethysian and Atlantic buildups of the Maghr eb Atlas. They occupied about 20 % of the whole biomass volume in the Oxfor dian reef, 40 % in the Kimmeridgian reef (High Atlas, Morocco) and 25 % in the Tithonian bioherm (Tunisia). (C) 2000 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.