Sedimentology of cherts in the Early Proterozoic Wishart Formation, Quebec–Newfoundland, Canada

Title:
Sedimentology of cherts in the Early Proterozoic Wishart Formation, Quebec–Newfoundland, Canada
Authors:
Simonson, Bruce M.
Abstract:
The siliciclastic Wishart Formation of the Early Proterozic Labrador trough is high-energy shelf deposit. Wishart sandstones contain both interstitial chert with textures of void-filling cement and thin chert intercalations contaminated with siliciclastic mud. Although volumetrically minor, these cherts occur in several thin, areally extensive stratigraphic mud. Although volumetrically minor, these cherts occur in several thin, areally extensive stratigraphic intervals. The Wishart contains intraclasts of both the chertcemented sandstone and the impure chert layers (as well as several other types of chert sand and gravel). This suggests the cherts formed penecontemporaneously, which is consistent with the absence of any signs of replacement in all but one of the chert types and the clear-cut distinctions between chert types, even where they are side by side in a single thin section. The origin which appears to be most compatible with available evidence is that the cherts represent silica precipitated from thermal waters that rose through the sediments of the Wishart shelf and discharged precipitated from thermal waters that rose through the sediments of the Wishart shelf and discharged into suprajacent seawater. A biogenic origin is unlikely in view of the lack of appropriate organisms during the Early Proterozic and the rapidity with which the cements formed. A volcanogenic origin is likely because volcaniclastic tezxtures are plentiful in associated formations but absent from the Wishart. Precipitation induced by evaporative concentration in unlikely in view of the widespread evidence of tidal currents and the lack of evidence of desiccation in the Wishart. Finally, the cherts are not restricted to the lowest-energy faces, and therefore they presumably did not accumulate as a background sediment. Deposition of silica above the sediment/water interface was probably made possible by ambient concentrations of silica that were significantly higher than those of Phancrozoic seawater. Cherts with similar textures occur in other Early Proterozoic sediments, most notably arenitic or granular iron-formations.
Citation:
Simonson, B.M. 1985. "Sedimentology of cherts in the Early Proterozoic Wishart Formation, Quebec–Newfoundland, Canada." Sedimentology 32(1): 23-40.
Publisher:
Wiley-Blackwell
DATE ISSUED:
1985-02
Department:
Geology
Type:
article
PUBLISHED VERSION:
10.1111/j.1365-3091.1985.tb00490.x
PERMANENT LINK:
http://hdl.handle.net/11282/309716

Full metadata record

DC FieldValue Language
dc.contributor.authorSimonson, Bruce M.en_US
dc.date.accessioned2013-12-23T16:16:13Zen
dc.date.available2013-12-23T16:16:13Zen
dc.date.issued1985-02en
dc.identifier.citationSimonson, B.M. 1985. "Sedimentology of cherts in the Early Proterozoic Wishart Formation, Quebec–Newfoundland, Canada." Sedimentology 32(1): 23-40.en_US
dc.identifier.issn0037-0746en_US
dc.identifier.urihttp://hdl.handle.net/11282/309716en
dc.description.abstractThe siliciclastic Wishart Formation of the Early Proterozic Labrador trough is high-energy shelf deposit. Wishart sandstones contain both interstitial chert with textures of void-filling cement and thin chert intercalations contaminated with siliciclastic mud. Although volumetrically minor, these cherts occur in several thin, areally extensive stratigraphic mud. Although volumetrically minor, these cherts occur in several thin, areally extensive stratigraphic intervals. The Wishart contains intraclasts of both the chertcemented sandstone and the impure chert layers (as well as several other types of chert sand and gravel). This suggests the cherts formed penecontemporaneously, which is consistent with the absence of any signs of replacement in all but one of the chert types and the clear-cut distinctions between chert types, even where they are side by side in a single thin section. The origin which appears to be most compatible with available evidence is that the cherts represent silica precipitated from thermal waters that rose through the sediments of the Wishart shelf and discharged precipitated from thermal waters that rose through the sediments of the Wishart shelf and discharged into suprajacent seawater. A biogenic origin is unlikely in view of the lack of appropriate organisms during the Early Proterozic and the rapidity with which the cements formed. A volcanogenic origin is likely because volcaniclastic tezxtures are plentiful in associated formations but absent from the Wishart. Precipitation induced by evaporative concentration in unlikely in view of the widespread evidence of tidal currents and the lack of evidence of desiccation in the Wishart. Finally, the cherts are not restricted to the lowest-energy faces, and therefore they presumably did not accumulate as a background sediment. Deposition of silica above the sediment/water interface was probably made possible by ambient concentrations of silica that were significantly higher than those of Phancrozoic seawater. Cherts with similar textures occur in other Early Proterozoic sediments, most notably arenitic or granular iron-formations.en_US
dc.language.isoen_USen_US
dc.publisherWiley-Blackwellen_US
dc.identifier.doi10.1111/j.1365-3091.1985.tb00490.xen
dc.subject.departmentGeologyen_US
dc.titleSedimentology of cherts in the Early Proterozoic Wishart Formation, Quebec–Newfoundland, Canadaen_US
dc.typearticleen_US
dc.identifier.journalSedimentologyen_US
dc.subject.keywordSilicaen_US
dc.subject.keywordGeology, Stratigraphic--Proterozoicen_US
dc.subject.keywordHigh energy formingen_US
dc.subject.keywordReefsen_US
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