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Accueil du site → Master → Etats Unis → 2010 → The Distribution, Composition, and Formation of Sahara Desert Microbialites From the Base of the Meski Plateau, outside Erfoud, Morocco

University of Massachusetts Amherst (2010)

The Distribution, Composition, and Formation of Sahara Desert Microbialites From the Base of the Meski Plateau, outside Erfoud, Morocco

Faulkner Sean

Titre : The Distribution, Composition, and Formation of Sahara Desert Microbialites From the Base of the Meski Plateau, outside Erfoud, Morocco

Auteur : Faulkner Sean

Université de soutenance : University of Massachusetts Amherst

Grade : Master of Science (M.S.) 2010

Résumé
Seven distinctly different museum-quality concretionary morphotypes of elongate, spheroidal, banded, botryoidal, columnar, rosette, and speleothem in regolith at two small sites at the base of the Meski Plateau near Erfoud, Morocco are described. Although most are isolated hand samples, the largest concretions are meter-sized blocks. Not one sample resembles any surrounding outcrop or bedrock. The barite rosettes formed first via periodic mixing of Ba2+/SO42- saturated solutions. They provided nuclei for cyclical precipitation-based concentric concretion development. The speleothem formed via precipitation from a carbonate-saturated solution in a large void within porous sandstone. The sand concretions formed when calcite precipitated around grains in unconsolidated quartz sands with cyclic fluctuation of Ca2+/CO32- saturated ground water. Petrographic analyses, stable isotope data, sample morphology, coupled with light and scanning electron microscopy indicate that microbial processes induced the periodic cement precipitation that produced the unique concretions.

Mots-clés : Concretions, sandstone, carbonate cement, bacteria, microbialites, Morocco

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Page publiée le 9 mai 2011, mise à jour le 22 février 2019