Cryptic biostalactites in a submerged karst cave of the Belize Barrier Reef revisited: Pendant bioconstructions cemented by microbial micrite
Gischler E, Heindel K, Birgel D, Brunner B, Reitner J, Peckmann J (2017)
Publication Type: Journal article
Publication year: 2017
Journal
Publisher: Elsevier B.V.
Book Volume: 468
Pages Range: 34-51
DOI: 10.1016/j.palaeo.2016.11.042
Abstract
Microbial carbonates are important components of postglacial tropical coral reef frameworks. Curious calcium carbonate protrusions in a submarine karst cave in the Belize Barrier Reef platform were initially interpreted as being largely the product of physicochemical precipitation around a meshwork of serpulid tubes. New petrographical, mineralogical, geochronological, and inorganic and organic geochemical data suggest that sulfate-reducing bacteria played a substantial role in carbonate formation, just as in cryptic settings of other modern, tropical coralgal reefs. The bacterial involvement in carbonate authigenesis is indicated by the content and isotopic composition of carbonate-associated sulfate, the presence of non-isoprenoidal sn-1-mono-O-alkyl glycerol monoethers (MAGEs) and terminally-branched fatty acids, and the observation that the majority of molecular fossils assigned to sulfate-reducing bacteria are tightly associated with the carbonate mineral lattice. The carbonate protrusions that were formerly named pseudostalactites, are termed biostalactites here to underline the significance of biological activity during carbonate formation. The Belize biostalactites are composed of four carbonate phases including serpulid tubes, lithified sediment, and microbial carbonate, as well as unconsolidated sediment usually found in macroborings of bivalve molluscs. Lithified sediment and microbial carbonate are fine-grained with clotted, mottled, and peloidal textures. While serpulid tubes are aragonitic, lithified sediment and microbial carbonates are mixtures of high-magnesium calcite and aragonite. Magnesium-calcite content increases with increasing consolidation. Lithified sediment and microbial carbonate are interpreted as fine, biodetrital sediment that was subsequently cemented by authigenic micrite. Scalenohedral high-magnesium calcite and acicular aragonite cements played a subordinate role in cementation. Carbon and oxygen stable isotope ratios of lithified sediment and microbial carbonate exhibit similar ranges as modern reefal microbialites. Our study exemplifies that heterotrophic bacteria can be a crucial agent that contributes to the formation of carbonate build-ups by cementing skeletal frameworks in cryptic environments.
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APA:
Gischler, E., Heindel, K., Birgel, D., Brunner, B., Reitner, J., & Peckmann, J. (2017). Cryptic biostalactites in a submerged karst cave of the Belize Barrier Reef revisited: Pendant bioconstructions cemented by microbial micrite. Palaeogeography, Palaeoclimatology, Palaeoecology, 468, 34-51. https://dx.doi.org/10.1016/j.palaeo.2016.11.042
MLA:
Gischler, Eberhard, et al. "Cryptic biostalactites in a submerged karst cave of the Belize Barrier Reef revisited: Pendant bioconstructions cemented by microbial micrite." Palaeogeography, Palaeoclimatology, Palaeoecology 468 (2017): 34-51.
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