Brucite Microbialites in Living Coral Skeletons: Indicators of Extreme Microenvironments in Shallow-Marine Settings

Buster, Noreen, Holmes, Charles, Kloprogge, Jacob, Nothdurft, Luke, Sorauf, James, & Webb, Gregory (2005) Brucite Microbialites in Living Coral Skeletons: Indicators of Extreme Microenvironments in Shallow-Marine Settings. Geology (Boulder), 33(3), pp. 169-172.

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Brucite [Mg(OH)2] microbialites occur in vacated interseptal spaces of living scleractinian coral colonies (Acropora, Pocillopora, Porites) from subtidal and intertidal settings in the Great Barrier Reef, Australia, and subtidal Montastraea from the Florida Keys, United States. Brucite encrusts microbial filaments of endobionts (i.e., fungi, green algae, cyanobacteria) growing under organic biofilms; the brucite distribution is patchy both within interseptal spaces and within coralla. Although brucite is undersaturated in seawater, its precipitation was apparently induced in the corals by lowered pCO2 and increased pH within microenvironments protected by microbial biofilms. The occurrence of brucite in shallow-marine settings highlights the importance of microenvironments in the formation and early diagenesis of marine carbonates. Significantly, the brucite precipitates discovered in microenvironments in these corals show that early diagenetic products do not necessarily reflect ambient seawater chemistry. Errors in environmental interpretation may arise where unidentified precipitates occur in microenvironments in skeletal carbonates that are subsequently utilized as geochemical seawater proxies.

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26 citations in Web of Science®

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ID Code: 23513
Item Type: Journal Article
Refereed: Yes
Keywords: Brucite, Microbialite, Scleractinian Coral, Paleoclimate, Mg/Ca Ratio, Marine Chemistry
DOI: 10.1130/G20932.1
ISSN: 0091-7613
Subjects: Australian and New Zealand Standard Research Classification > EARTH SCIENCES (040000)
Divisions: Past > QUT Faculties & Divisions > Faculty of Science and Technology
Deposited On: 17 Jun 2009 13:57
Last Modified: 31 Mar 2015 02:56

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