Origins of carbonate spherulites: Implications for Brazilian Aptian pre-salt reservoir

Chafetz, Henry S.; Barth, Jennifer; Cook, Megan; Guo, Xuan; Zhou, Jie

doi:10.1016/j.sedgeo.2017.12.024

Cited by 72 publications

(42 citation statements)

References 45 publications

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“…Spherulites form in spring‐fed microbialite pinnacles in Lake Van and are thought to be directly related to both microbial activity and the mixing chemistry between lake water and groundwater (López‐García et al, ). Spherulites are also found in subaerial hot springs and spring‐associated tufa mounds at Searles Lake (Chafetz et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Notably, the WDL tufas contain large, millimeter‐scale, reworked spherulites, which are absent from FGL microbialites. Spherulites form around a central nucleus consisting of bacterial fossils and are interpreted as biogenic in origin (Chafetz, Barth, Cook, Guo, & Zhou, ). The spherulites in WDL tufas are typically amalgamations of several spherulites, indicating reworking of the sediments by shoreline processes (Figure c).…”

Section: Discussionmentioning

confidence: 99%

“…Spherulites are also found in subaerial hot springs and spring-associated tufa mounds at Searles Lake (Chafetz et al, 2018).…”

Section: Groundwater Associationmentioning

confidence: 95%

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Microbially influenced lacustrine carbonates: A comparison of Late Quaternary Lahontan tufa and modern thrombolite from Fayetteville Green Lake, NY

et al. 2019

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Carbonate microbialites in lakes can serve as valuable indicators of past environments, so long as the biogenicity and depositional setting of the microbialite can be accurately determined. Late Pleistocene to Early Holocene frondose draping tufa deposits from Winnemucca Dry Lake (Nevada, USA), a subbasin of pluvial Lake Lahontan, were examined in outcrop, petrographically, and geochemically to determine whether microbially induced precipitation is a dominant control on deposition. These observations were compared to modern, actively accumulating microbialites from Fayetteville Green Lake (New York, USA) using similar methods. In addition, preserved microbial DNA was extracted from the Lahontan tufa and sequenced to provide a more complete picture of the microbial communities. Tufas are texturally and geochemically similar to modern thrombolitic microbialites from Fayetteville Green Lake, and the stable isotopic composition of organic C, N, inorganic C, and O supports deposition associated with a lacustrine microbial mat environment dominated by photosynthetic processes. DNA extraction and sequencing indicate that photosynthetic microbial builders were present during tufa deposition, primarily Chloroflexi and Proteobacteria with minor abundances of Cyanobacteria and Acidobacteria. Based on the sequencing results, the depositional environment of the tufas can be constrained to the photic zone of the lake, contrasting with some previous interpretations that put tufa formation in deeper waters. Additionally, the presence of a number of mesothermophilic phyla, including Deinococcus–Thermus, indicates that thermal groundwater may have played a role in tufa deposition at sites not previously associated with groundwater influx. The interpretation of frondose tufas as microbially influenced deposits provides new context to interpretations of lake level and past environments in the Lahontan lake basins.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Microbially influenced lacustrine carbonates: A comparison of Late Quaternary Lahontan tufa and modern thrombolite from Fayetteville Green Lake, NY

et al. 2019

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“…Microbialites with an internal fabric characterized by fibrous‐radiating carbonate spherulites have also been identified in a number of modern lakes, including in saline lakes in southeastern Australia (Taylor, 1975) and on an atoll in the equatorial Pacific Ocean (Arp et al., 2012). Spherulites have been found in a number of other modern depositional settings, notably hot springs (Chafetz, Barth, Cook, Guo, & Zhou, 2018; Jones & Renaut, 1995) and in calcrete crusts (Verrecchia, Freytet, Verrecchia, & Dumont, 1995), emphasizing a wide range of formation modes. In the geological record, carbonate spherulites associated with Mg‐silicate minerals and poorly crystalline Mg‐Si substances or “gels” have been reported in the economically important Lower Cretaceous (Aptian) “Pre‐Salt” South Atlantic lacustrine carbonate rocks (Muniz & Bosence, 2015; Saller et al., 2016; Terra et al., 2010) and have also been reported in lake deposits of Carboniferous age (Rogerson et al., 2017).…”

Section: Introductionmentioning

confidence: 99%

“…Rapid precipitation of aragonitic spherulites in microbialites has been observed in saline lakes on an atoll in the tropical Pacific Ocean, interpreted as resulting from pH increases driven by high rates of cyanobacterial oxygenic photosynthesis(Arp et al, 2012), though pH values are not given. In addition, observational and empirical data have shown that spherulites preferentially initiate in the presence of organic matter(Braissant, Cailleau, Dupraz, & Verrecchia, 2003;Chafetz et al, 2018;Mercedes-Martín et al, 2016), shown to have been present within the large spherulites by coccoid cell molds (Figure 5b). Seasonal changes in the lake physiochemistry may have contributed to aragonite and/or calcite precipitation in all three layers.…”

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confidence: 98%

Spherulitic microbialites from modern hypersaline lakes, Rottnest Island, Western Australia

et al. 2020

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Microbialites are organosedimentary deposits formed by the interaction of benthic microbial communities with their environment (Burne & Moore, 1987) and provide the only continuous macroscopic record for life spanning its appearance in the Archean through to the present day (Riding, 2000). Biological, physical, and chemical processes combine to produce an internal structure characteristic of microbialites, which include laminated fabrics and clotted to unlayered fabrics (Kennard & James, 1986).

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Effects of salinity, organic acids and alkalinity on the growth of calcite spherulites: Implications for evaporitic lacustrine sedimentation

Mercedes‐Martín¹,

Rao

Rogerson

et al. 2021

The Depositional Record

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Lacustrine non‐skeletal carbonates exhibit a diversity of petrographies due to interactions between physico‐chemical and biologically influenced mechanisms. Despite the suggestion that evaporative concentration was involved in the formation of spherulite and shrubby‐bearing carbonate successions in the Pre‐Salt Cretaceous alkaline lakes of the South Atlantic, no consensus exists about the water chemistries promoting these exotic mineral textures. In this work, an experimental approach was developed to evaluate how changes in salinity (NaCl) and biopolymer concentrations (alginic acid) impact calcite growth dynamics from saline and alkaline synthetic solutions. Hydrochemical and petrographical data from selected modern saline/alkaline environments were compared with experimental datasets to further estimate how the underlying (bio)chemical conditions and lake locations probably converge to allow the formation of calcite spherulite grains in evaporitic settings. Spherulitic calcite from Recent saline lakes and experiments arise from waters with moderate to high [Calcium]/[Alkalinity] ratios ([Ca]/[Alk]) rather than in calcium‐depleted and alkaline‐rich environments which tend to produce single‐crystal calcites during abiotic water mixing or lake evaporation. This observation is consistent with the assembly of polycrystalline textures being a kinetically controlled feature, forced by remarkably high rates of nucleation. Also, the data analysed do not support a causative relationship between evaporite‐driven salinity fluctuations and the preferential formation of spherulites, shrubs or their intermediate textures. Ubiquitous in saline lakes, organic substances can lower the kinetic thresholds for spherulitic calcite aggregation while microbial photosynthesis can also raise pH, altogether enhancing calcite supersaturation and promoting spherulite formation in waters with moderate‐high [Ca]/[Alk] ratios and high salinities. Localised observations of abiotic spherulites in Recent soda lakes can occur in restricted mixing zones where [Ca]/[Alk] ratios are enhanced. This work highlights the roles of concentration regimes associated with biopolymers and microbial metabolism against the background salinity fluctuations in determining the morphological and textural transitions in lacustrine carbonate minerals.

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Origins of carbonate spherulites: Implications for Brazilian Aptian pre-salt reservoir

Cited by 72 publications

References 45 publications

Microbially influenced lacustrine carbonates: A comparison of Late Quaternary Lahontan tufa and modern thrombolite from Fayetteville Green Lake, NY

Microbially influenced lacustrine carbonates: A comparison of Late Quaternary Lahontan tufa and modern thrombolite from Fayetteville Green Lake, NY

Spherulitic microbialites from modern hypersaline lakes, Rottnest Island, Western Australia

Effects of salinity, organic acids and alkalinity on the growth of calcite spherulites: Implications for evaporitic lacustrine sedimentation

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