Geomicrobiology of carbonate microbialites in the Tahiti reef
Rolf J. Warthmann, Gilbert Camoin, Judith A. McKenzie, Crisógono Vasconcelos, 2015. "Geomicrobiology of carbonate microbialites in the Tahiti reef", Microbial Carbonates in Space and Time: Implications for Global Exploration and Production, D. W. J. Bosence, K. A. Gibbons, D. P. Le Heron, W. A. Morgan, T. Pritchard, B. A. Vining
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Integrated Ocean Drilling Program (IODP) Expedition 310 (Tahiti Sea Level) offered an opportunity to study the geomicrobiology of a reef framework. Offshore drilling was conducted on the coastal reefs of Tahiti (French Polynesia) at 22 sites in water depths of up to 117 m. Up to 80% of the retrieved core material comprises authigenic grey microbial carbonates with laminated or thrombolitic morphologies, which are associated with corals. Microbialites infilled the cavities during reef development and stabilized the coral reef framework. Rock-surface analyses were performed to track ongoing microbial activity in biofilms that could represent a modern counterpart of the processes at the origin of the formation of fossil microbialites. Significant concentrations of adenosine 5′-triphosphate, indicative of the presence of living microorganisms, were detected at relatively shallow depths, 0–6 m below the seafloor. Exoenzyme activities confirmed the presence of an active metabolizing microbiota forming biofilms in reef cavities. Onshore investigations of the recovered microbes and biofilms completed our picture that the rapid postglacial formation of carbonate microbialites was mediated by the activity of anaerobic microbes, such as sulphate-reducing bacteria and iron-respiring organisms, stimulated by the highly productive reef environment.
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Microbial carbonates (microbialites) are remarkable sedimentary deposits. They have the longest geological range of any type of biogenic limestones, form in the greatest range of different sedimentary environments, oxygenated the Earth’s atmosphere and produce and, furthermore, store large volumes of hydrocarbons. This Special Publication provides significant contributions at a pivotal time in our understanding of microbial carbonates when their economic importance has become established and the results of many research programmes are coming to fruition.
It is the first book to focus on the economic aspects of microbialites and in particular the giant pre-salt discoveries offshore Brazil. The volume contains papers on the processes involved in the formation of both ancient and modern microbialites and the diversity of style in microbial carbonate build-ups. Structures and fabrics from both marine and non-marine settings are discussed from throughout the geological record.