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TitleSedimentation in a subaqueous arc/back-arc setting: the Bobby Cove Formation, Snooks Arm Group, Newfoundland
AuthorCousineau, P A; Bédard, J H
SourcePrecambrian Research vol. 101, issue 2-4, 2000 p. 111-134,
Alt SeriesGeological Survey of Canada, Contribution Series 1999050
PublisherElsevier BV
Mediapaper; on-line; digital
File formathtml; pdf
ProvinceNewfoundland and Labrador
AreaBetts Cove
Lat/Long WENS -55.7500 -55.5000 50.0000 49.9167
Subjectsregional geology; sedimentology; igneous rocks; volcanic rocks; sedimentary rocks; sedimentation; volcaniclastics; depositional environment; petrography; tuffs; turbidites; conglomerates; breccias; facies; basalts; volcanism; Archean; Bobby Cove Formation; Snooks Arm Group; Ordovician; Paleozoic; Precambrian
Illustrationssketch maps; stratigraphic sections; photomicrographs; tables; cross-sections
AbstractThe Bobby Cove Formation of the Snooks Arm Group, north-central Newfoundland, displays cycles of lava- and sediment-dominated successions. The formation, located between pillow basalts and black graptolite-bearing mudstones, was deposited in a subaqueous setting. Volcaniclastic rocks were produced by calc-alkaline volcanism that either occurred during quiescence of, or was synchronous with, periods of tholeiitic volcanism. Variation in rock chemistry supports a change in tectonic setting from an expanding fore-arc oceanic crust to a progressively more mature magmatic arc/back-arc system. Combined chemical, sedimentological and detailed petrographic studies define several types of volcaniclastic sedimentary rocks of pyroclastic, epiclastic, and mixed origin. The volcaniclastic rocks were divided into three groups based of clast components and textures: (1) a monogenic facies with minor mudstone interbeds, composed of basaltic to basaltic andesite clasts, is interpreted to have originated from subaqueous vertically-directed, pyroclastic eruptions; (2) a polygenic facies with abundant mudstone interbeds composed of rounded fragments and a lack of vitric vesicular mafic fragments, was probably derived from chemical weathering and mechanical erosion of volcanic rocks (i.e. epiclastic volcanolithic sandstone); and (3) a second polygenic facies with minor mudstone interbeds is characterized by diverse clast compositions and textures, and is interpreted as remobilized deposits from previously deposited, fresh and/or altered, pyroclastic debris.

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