Development of Carbonate Banks and Hypersaline Basins, Shark Bay, Western Australia&lt;xref ref-type="fn" rid="ch2fn1"&gt;&lt;sup&gt;1&lt;/sup&gt;&lt;/xref&gt;

Hagan, Gregory M.; Logan, Brian W.

doi:10.1306/m22379c2

Cited by 10 publications

(3 citation statements)

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“…For example, smaller holes within dense peloidal micrite in smooth and colloform mats (Figures 9 and 10, Supplemental Figures S2 and S3) may result from the calcification of younger Entophysalis colonies, which have not undergone many cell divisions, whereas larger honeycomb structures observed in peloidal micrite forming in pustular mats (Figure 8, Supplemental Figure S1) may reflect the calcification of older Entophysalis colonies with multiple generations of cell divisions. Moreover, pustular mats are periodically subaerially exposed [11,23,24,43,44], which may lead to the preferential degradation of the older, outermost sheath and/or evaporitic precipitation of carbonate during exposure [9,45], thereby leading to large honeycomb textures.…”

Section: Do Microbes Influence the Micritic Textures?mentioning

confidence: 99%

Initial Accretion in Hamelin Pool Microbialites: The Role of Entophysalis in Precipitation of Microbial Micrite

et al. 2022

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One of the largest assemblages of living marine microbialites, with shapes and sizes analogous to ancient structures, is found along the margins of Hamelin Pool, Shark Bay, Western Australia. An investigation of microbial mats on the surfaces of these structures using petrographic analysis, light, and scanning electron microscopy identified the in situ precipitation of micrite as an important accretion mechanism in all major mat types (pustular, smooth, and colloform). Within each mat type, peloidal micrite, composed of nano-bulbous spheres to tabular and rod-shaped crystals, was closely linked with cells of the coccoid cyanobacterium Entophysalis, and microtextures of the micrite reflected the size and distribution of Entophysalis colonies. In pustular surface mats, where large colonies of Entophysalis were common, large clots of micrite were distributed randomly throughout the mat. In contrast, in smooth and colloform mats, where smaller colonies of Entophysalis were distributed along horizons, micrite formed fine laminae. In all surface mat types, micrite associated with Entophysalis had a characteristic honeycomb appearance, resulting from cell and/or colony entombment. These findings redefine our understanding of microbialite accretion in Hamelin Pool, recognizing the importance of microbial micrite in microbialite growth and showing that coccoid cyanobacteria are capable of building laminated structures. Moreover, Entophysalis, the dominant visible microbe associated with the precipitation of micrite in Hamelin Pool, has a lineage to Eoentophysalis, found throughout early and middle Proterozoic microbialites assemblages. These findings reinforce the importance of Hamelin Pool as a window to the past.

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Section: Do Microbes Influence the Micritic Textures?mentioning

confidence: 99%

Initial Accretion in Hamelin Pool Microbialites: The Role of Entophysalis in Precipitation of Microbial Micrite

et al. 2022

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“…The organisms living in Hamelin Pool are restricted by the large seasonal temperature fluctuations (11–33°C) and high salinity (Suosaari et al, 2016). The salinity began to increase from baseline ocean levels (35–40‰) around 5000 years ago when sediment and seagrass barriers limited the amount of water exiting the basin (Hagan & Logan, 1974; Logan & Cebulski, 1970). Microbial trapping and binding of shell fragments and carbonate precipitation contribute to the formation of microbialites in Hamelin Pool (Hoffman, 1976; Playford & Cockbain, 1976), and degradation of the microbial mats is thought to contribute to abundant peloids (Suosaari et al, 2022).…”

Section: Geologic Settingmentioning

confidence: 99%

“…Shark Bay ooids are aragonitic, 0.2–0.3 mm in diameter (typically quite small), with nuclei that contain carbonate and quartz grains, foraminiferal tests, or mollusk fragments (Davies, 1970; Hagan & Logan, 1974). Most ooids in Shark Bay are white, in some cases preserving laminae better than their bored Bahamian counterparts (Diaz et al, 2014; Harris et al, 2019; Mariotti et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Organic‐rich bimineralic ooids record biological processes in Shark Bay, Western Australia

et al. 2023

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Marine ooids have formed in microbially colonized environments for billions of years, but the microbial contributions to mineral formation in ooids continue to be debated. Here we provide evidence of these contributions in ooids from Carbla Beach, Shark Bay, Western Australia. Dark 100–240 μm diameter ooids from Carbla Beach contain two different carbonate minerals. These ooids have 50–100 μm‐diameter dark nuclei that contain aragonite, amorphous iron sulfide, detrital aluminosilicate grains and organic matter, and 10–20 μm‐thick layers of high‐Mg calcite that separate nuclei from aragonitic outer cortices. Raman spectroscopy indicates organic enrichments in the nuclei and high‐Mg calcite layers. Synchrotron‐based microfocused X‐ray fluorescence mapping reveals high‐Mg calcite layers and the presence of iron sulfides and detrital grains in the peloidal nuclei. Iron sulfide grains within the nuclei indicate past sulfate reduction in the presence of iron. The preservation of organic signals in and around high‐Mg calcite layers and the absence of iron sulfide suggest that organics stabilized high‐Mg calcite under less sulfidic conditions. Aragonitic cortices that surround the nuclei and Mg‐calcite layers do not preserve microporosity, iron sulfide minerals nor organic enrichments, indicating growth under more oxidizing conditions. These morphological, compositional, and mineralogical signals of microbial processes in dark ooids from Shark Bay, Western Australia, record the formation of ooid nuclei and the accretion of magnesium‐rich cortical layers in benthic, reducing, microbially colonized areas.

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Effects of isolation by distance and geographical discontinuity on genetic subdivision of Littoraria cingulata

Johnson

1998

Marine Biology

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Development of Carbonate Banks and Hypersaline Basins, Shark Bay, Western Australia<xref ref-type="fn" rid="ch2fn1"><sup>1</sup></xref>

Cited by 10 publications

References 0 publications

Initial Accretion in Hamelin Pool Microbialites: The Role of Entophysalis in Precipitation of Microbial Micrite

Initial Accretion in Hamelin Pool Microbialites: The Role of Entophysalis in Precipitation of Microbial Micrite

Organic‐rich bimineralic ooids record biological processes in Shark Bay, Western Australia

Effects of isolation by distance and geographical discontinuity on genetic subdivision of Littoraria cingulata

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