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Organomineralization of Microbialites from Storr’s Lake, San Salvador Island, Bahamas: Calcium Stable Isotope Analysis using TIMS and a 42Ca-43Ca double spike

Wogsland, Brittan Valhalla
http://rave.ohiolink.edu/etdc/view?acc_num=osu1587723502946554

Abstract Details

2020, Master of Science, Ohio State University, Earth Sciences.
The isotopic composition and mineralogy of modern microbialites provides us with tools useful for interpreting the formation processes and environments of ancient microbialites. Growing in the hypersaline and turbid Storr’s Lake on San Salvador Island in The Bahamas today are microbialites with low levels of photosynthesis and high levels of sulfate reduction-in contrast to many of their modern counterparts. Living planktonic, motile microorganisms and suspended algal and bacterial debris create the high turbidity of the shallow lake (<2 m) and rapidly attenuate sunlight in the water column. Within Storr’s Lake microbial metabolisms induce precipitation of carbonate within microenvironments of the microbial mats. Both high-Mg calcite (HMC) and aragonite are found within a majority of the microbialites measured leading to the hypothesis that the organomineralization process involves a step where HMC transforms to aragonite. Mineralogy and elemental analysis of a wide sampling of microbialites was undertaken to understand the extent of aragonite within Storr’s Lake microbialites. It was found that aragonite occurs at water depths greater than 40 cm within the lake and was present in all but one microbialite measured in this study. New calcium (Ca) stable isotopic analyses from the thermal ionization mass spectrometer using a 42Ca-43Ca double spike provides evidence for exploring the systems fractionating Ca within Storr’s Lake water and microbialites. In contrast to geochemical data and previous Mg stable isotopic measurements on the same waters, the Ca stable isotopic value (δ44/40Ca) of water in Storr’s Lake is not homogeneous. While the northern sector is primarily influenced by seawater, the southern sector δ44/40Ca is shifted away from seawater to lower values, suggesting internal variability within the lake. In both microbialites measured, δ44/40Ca is strongly correlated to mineralogy and trace elements in the carbonate. To explore the potential influence of microbial processes on the Ca isotopic composition of the microbialite carbonate, Δ44/40Cacarbonate-lake water was calculated. For the purest aragonite sample measured, Δ44/40Cacarbonate-lake water water falls within the range of experimental Δ44/40Caaragonite-water of biogenic and abiogenic aragonite. This suggests that the Ca within aragonite may or may not be influenced by biological fractionation during its formation within the microbialite.
Elizabeth Griffith, PhD (Advisor)
Matthew Saltzman, PhD (Committee Member)
Thomas Darrah, PhD (Committee Member)
188 p.
Biogeochemistry; Earth; Geobiology; Geochemistry; Geological; Geology; Morphology; Petroleum Geology
biomineralization; organomineralization; calcium isotopes; TIMS; thermal ionization mass spectrometer; stromatolite; microbialite; thrombolite; Storrs Lake; San Salvador Island; Bahamas; stable isotopes; geochemistry; carbonate; calcite; aragonite; microbial mat

Recommended Citations

Citations

  • Wogsland, B. V. (2020). Organomineralization of Microbialites from Storr’s Lake, San Salvador Island, Bahamas: Calcium Stable Isotope Analysis using TIMS and a 42Ca-43Ca double spike [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587723502946554

    APA Style (7th edition)

  • Wogsland, Brittan. Organomineralization of Microbialites from Storr’s Lake, San Salvador Island, Bahamas: Calcium Stable Isotope Analysis using TIMS and a 42Ca-43Ca double spike. 2020. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1587723502946554.

    MLA Style (8th edition)

  • Wogsland, Brittan. "Organomineralization of Microbialites from Storr’s Lake, San Salvador Island, Bahamas: Calcium Stable Isotope Analysis using TIMS and a 42Ca-43Ca double spike." Master's thesis, Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587723502946554

    Chicago Manual of Style (17th edition)

osu1587723502946554
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This open access ETD is published by The Ohio State University and OhioLINK.