The biogeomorphology of Shark Bay's microbialite coasts

Morris, Therese; Visscher, Pieter T.; O’Leary, Michael J.; Fearns, Peter; Collins, Lindsay B.

doi:10.1016/j.earscirev.2019.102921

Cited by 8 publications

(29 citation statements)

References 136 publications

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“…Microbial mats and cyclone-derived materials were sampled from the RRBS monitoring site (Morris et al, 2020) on the south eastern coast/shore(line) of Hamelin Pool (Figure 1). The RRBS monitoring site lies at the southern end of a bight (sensu Logan & Cebulski, 1970), north of Flint Cliff, at the mouth of an outwash drainage channel that flows episodically during rare high rainfall events such as TC Olwyn.…”

Section: Site and Sample Descriptionsmentioning

confidence: 99%

“…The RRBS monitoring site lies at the southern end of a bight (sensu Logan & Cebulski, 1970), north of Flint Cliff, at the mouth of an outwash drainage channel that flows episodically during rare high rainfall events such as TC Olwyn. At this location, the steep beach face abuts a more gently sloping intertidal terrace across which a number of distinct biogeomorphological units have been defined (Morris et al, 2020). Samples were collected from within the intertidal zone across a number of different biogeomorphological units both within the mouth of the channel and beyond.…”

Section: Site and Sample Descriptionsmentioning

confidence: 99%

“…Thick deposits occurred between microbialitic structures within the mid-intertidal zone (TMMU of Morris et al, 2020) and in protected areas of the upper intertidal zone (MPU). In the upper intertidal zone, these deposits experienced repeated desiccation and inundation cycles with the tide variations.…”

Section: Introductionmentioning

confidence: 99%

“…In the upper intertidal zone, these deposits experienced repeated desiccation and inundation cycles with the tide variations. Fair-weather waves reworked the deposit into cobble-sized mucilage clasts (mudballs) close to the base of the beach face (IBFU/MPU boundary of Morris et al, 2020). Upon returning to the impacted site in July 2016 (481 days after the cyclone), it was found that the black sludge deposits were still recognizable, although their surface morphology was modified (Morris et al submitted), between microbialite columns, and mucilage cobbles were still present closer to the shoreline.…”

Section: Introductionmentioning

confidence: 99%

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Structure and function of Shark Bay microbial communities following tropical cyclone Olwyn: A metatranscriptomic and organic geochemical perspective

et al. 2021

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Shark Bay, Western Australia, is episodically impacted by tropical cyclones. During 2015, the region was hit by a category 3 cyclone, "severe tropical cyclone Olywn," leading to the formation of a black sludge in an intertidal zone harboring microbial mats and microbialites. Upon returning to the impacted site 12 months later, the black sludge deposit was still recognizable between the microbialite columns and mucilaginous cobbles near the shoreline in the impacted area. Metatranscriptomic and organic geochemical analyses were carried out on the cyclone-derived materials and impacted microbial mat communities to unravel the structure, function, and potential preservation of these deposits following a tropical cyclone. It was found that samples derived from the black sludge contained low relative abundances of cyanobacteria but had higher proportions of heterotrophic and anaerobic microorganisms (e.g., methanogens and sulfate-reducing bacteria). Increased metabolic activity by these microorganisms (e.g., sulfate reduction and organic matter degradation) is thought to drive calcium carbonate precipitation and helps in mat preservation. Comparison of the aliphatic biomarker by gas chromatography-mass spectrometry (GC-MS) analyses showed that C 25 highly branched isoprenoid (HBI) alkenes were significantly higher in the cyclone-derived materials attributed to the relocation of subtidal sediments containing HBI-producing diatom communities by the tropical cyclone. Raney nickel desulfurization of the polar fraction extracted from a mucilaginous cobble revealed sulfur-bound hopanoids and a series of benzohopanes. The presence of these compounds could be indicative of microbial matter that has been influenced by the tropical cyclone which may have caused elevated levels of water column anoxia promoting increased sulfurization of the organic matter to occur.

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Section: Site and Sample Descriptionsmentioning

confidence: 99%

Section: Site and Sample Descriptionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structure and function of Shark Bay microbial communities following tropical cyclone Olwyn: A metatranscriptomic and organic geochemical perspective

et al. 2021

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“…The combination of sealevel fall and bank development reduced oceanic circulation within Hamelin Pool which, combined with high evaporation rates, allowed the development of hypersaline conditions (Logan & Cebulski, 1970). This hypersalinity resulted in restricted biological diversity within Hamelin Pool, supporting both the development of the extant benthic microbialites since approximately 2000 years ago (Chivas et al, 1990;Giusfredi, 2014;Morris et al, 2020;Playford et al, 2013) and the abundant development of the cockle Fragum eragatum since about 4500 years ago (Correia Baptista da Silva, 2014;Playford et al, 2013). Fragum shells accumulate in deposits of the Hamelin Coquina (Logan & Cebulski, 1970) around and within Hamelin Pool.…”

Section: Field Setting Overviewmentioning

confidence: 99%

Impacts of Severe Tropical Cyclone Olwyn and the biogeomorphic response, Hamelin Pool, Shark Bay, Western Australia

Morris

Fearns

et al. 2022

The Depositional Record

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Storm disturbance and recovery of the peritidal benthic microbial ecosystem occurs as part of the natural climate regime in Shark Bay. However, tropical cyclone and winter storm frequency and intensity are known to be changing due to climate forcing. Presented here is an analysis of the biogeomorphic response of the benthic microbial ecosystem within the intertidal to upper subtidal zone and the beach face coquina deposits of Hamelin Pool, to the passage of Category 3 Severe Tropical Cyclone Olwyn (13 March 2015). Storm effects (initial response to 40 days post‐event) include: erosional sculpting of sediments, mats and structures; deposition and winnowing of sediments; accumulation of mucilaginous products into flocs, slurries and sludges; along with limited development of new coquina deposits in the beach face. Medium (15 months) term observations include: mat recovery and changes with transformation of mucilage deposits into new subtidal gelatinous mats, intertidal transitional mats and low‐elevation microbial structures. Observations suggest that this disturbance had both positive (the floc‐to‐mat biogeomorphic storm response) and negative feedbacks (enhanced bioturbation), which impact the development of stromatolite forming microbial mats and microbialite structures.

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Bidirectional fabric evolution in Hamelin Pool microbialites, Shark Bay, Western Australia

Vitek

Suosaari

Oehlert

et al. 2023

The Depositional Record

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Hamelin Pool, Shark Bay, Western Australia hosts the world's largest and most extensive assemblages of living marine microbialites, comparable in size and shape to ancient structures found throughout the fossil record. Here, we document the internal fabrics of modern microbialites collected throughout Hamelin Pool. Meso‐ and microscale observations of microbialite polished slabs and thin section scans, optical microscopy, and scanning electron microscopy coupled with energy‐dispersive X‐ray spectroscopy formed the basis for a fabric classification system that combines accretionary mat type with microfabric. Accretionary mat types included pustular, smooth, colloform, as well as ‘transitional’ mats that are a cross between pustular and smooth mats. Mapping of fabrics in 45 microbialite heads indicated bi‐directional evolution. An upward progression of fabrics corresponded to changes in mat type as the head grew upward into shallower water. A downward evolution of microfabrics occurred as surface mats transitioned into the subsurface of the microbialite structure. Downward microfabric evolution occurred as a result of early taphonomic processes, and involved a progression from the original depositional architecture to subsequent stages of micritic thickening, and finally, cement infilling. The observed bi‐directional evolution of microbialite microfabrics within Hamelin Pool offers a conceptual framework for the study of modern microbialites, not simply as the sole product of accretionary mat types but rather as the combined result of the activity of surface mats and their taphonomic evolution. Early taphonomic processes induce further lithification of the microbialites which may enhance preservation potential in the geological record.

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The biogeomorphology of Shark Bay's microbialite coasts

Cited by 8 publications

References 136 publications

Structure and function of Shark Bay microbial communities following tropical cyclone Olwyn: A metatranscriptomic and organic geochemical perspective

Structure and function of Shark Bay microbial communities following tropical cyclone Olwyn: A metatranscriptomic and organic geochemical perspective

Impacts of Severe Tropical Cyclone Olwyn and the biogeomorphic response, Hamelin Pool, Shark Bay, Western Australia

Bidirectional fabric evolution in Hamelin Pool microbialites, Shark Bay, Western Australia

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