Microbial Biofacies and the Influence of Metazoans in Holocene Deposits of the Lagoa Salgada, Rio De Janeiro State, Brazil

Ricardi-Branco, Frésia; Callefo, Flavia; Cataldo, Rafael Amaral; Noffke, Nora; Pessenda, Luiz Carlos Ruiz; Vidal, Alexandre Campane; Branco, Fábio Cardinale

doi:10.2110/jsr.2018.64

Cited by 13 publications

(3 citation statements)

References 45 publications

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“…Castro-Contreras et al, 2014;Tarhan et al, 2013). In some cases, metazoan activities such as grazing and burrowing (top-down pressures) can, at least partially, rework an originally stromatolitic fabric to a thrombolitic one (Planavsky & Ginsburg, 2009;Ricardi-Branco et al, 2018). However, the co-existence of well-laminated microbialite varieties with metazoans suggest that non-laminated species (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…In addition to ichnology, microbialites are also important regarding taphonomy and the preservation of fossils. The bioclasts present in the microbialite deposits may have been transported to the microbialite pools by storm events or could be indicative of resident organisms using the microbialite as a refuge habitat (Ricardi-Branco et al, 2018;Rishworth et al, 2019). In Brazil, microbial mats allowed for the extraordinary preservation of organisms, including soft-bodied animals such as shrimp and brittle echinoid tests, by protecting remains against disarticulation and scavenging, as well as advancing geochemical gradients that are conducive to fossilization (Varejao et al, 2019;Varejao et al, 2019).…”

Section: Discussionmentioning

confidence: 99%

“…Open, closed and total porosity percentages were calculated with CT Analyser (CTan) Software (v.1.17.17.2) by selecting a volume of interest for each 3D model. This method is non-destructive, requires no special sample preparation and has been successfully applied to characterize microbial carbonates (Machado et al, 2015;Ricardi-Branco et al, 2018). Volume rendering to highlight specific elements of the scans was performed using CTvox Software (v. 3.3).…”

Section: Sample Collection and Analysismentioning

confidence: 99%

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Metazoan activity facilitates passive sediment trapping in modern supratidal microbialites: Revealed using µ‐CT‐scanning and microscopy

et al. 2021

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Microbialites are formed through two processes, the trapping and binding of sediment grains and mineral precipitation. Sediment trapping and binding result in coarse sandy textures, whereas fine micritic textures are produced by mineral precipitation.Although well-studied modern microbialites (e.g. Bahamas and Shark Bay) are formed through the former process, purely trapped-and-bound examples are rare throughout the geologic record and limited to shallow-marine environments. Through the use of conventional microscopy and 3D micro-computed tomography (µ-CT) scanning, this study found that South African coastal microbialites have a primarily mineral precipitated texture, although detrital material is included sporadically. Furthermore, these modern microbialites exhibit both micritic and fibrous layering with high porosity. The novel use of 3D microtomography rotational scans has revealed that microbialites are extensively burrowed by metazoan activity and was also able to distinguish the occurrence and distribution of heavy minerals and detrital shell material in the samples. Some of the detrital grains appeared to be accidental/random inclusions, while in other cases the metazoan burrows provided space for the accumulation of sediment once abandoned. In both cases, sediment was incorporated as a product of intermittent accumulation, rather than systematic trapping and binding. The microfabric texture of South African microbialites is therefore a function of both biological (e.g. microbially mediated precipitation) and environmental (e.g. sporadic sediment deposition and inorganic cementation) influence. Overall, the findings presented here highlight the importance of these systems regarding microbialite formation, ichnology and taphonomy.

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