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TitlePalaeoenvironmental distribution of Proterozoic microfossils, with an example from the Agu Bay Formation, Baffin Island
AuthorButterfield, N J; Chandler, F W
SourcePalaeontology vol. 35, pt. 4, 1992 p. 943-957
Alt SeriesGeological Survey of Canada, Contribution Series 222091
NTS47E/03; 47E/04; 47E/05; 47E/06; 47E/11; 47E/12; 47E/13; 47E/14; 47F
AreaBaffin Island
Lat/Long WENS -88.0000 -82.0000 71.0000 70.0000
Subjectsgeneral geology; marine geology; sedimentology; paleontology; shales; black shales; microfossils; taxonomy; fossils; bedding planes; paleoecology; paleoenvironment; biostratigraphy; depositional environment
Illustrationslocation maps; cross-sections, stratigraphic; photomicrographs; graphs; schematic diagrams
ProgramNSERC Natural Sciences and Engineering Research Council of Canada
Released1992 01 01
AbstractA shale sample from the Black Shale Member of the c. 1250 Ma Agu Bay Formation, Fury and Hecla Group, north-west Baffin Island contains abundant, well-preserved microfossils. The assemblage is dominated by small leiosphaerid acritarchs of which c. 15 per cent show structures here interpreted as medial split release structures. Colonial unicells and larger spheroidal acritarchs are uncommon, and filamentous microfossils extremely rare. A single specimen of the highly distinctive acritarch Valeria lophostriata extends the geographic range of this taxon and, in concert with geochronological and chemostratigraphical data, constrains the timing of Fury and Hecla deposition to the early Late Riphean. The overall habit of the Black Shale Member assemblage, including the even bedding plane distribution of fossils, supports the sedimentological and stratigraphical evidence for a mid to outer shelf depositional environment. Incorporating these findings into a review of Proterozoic shale-hosted microfossils reveals a distinct depth/diversity trend in assemblage structure such that five broad zones can be recognized extending from restricted nearshore to basinal environments. The depositional environments of the Neoproterozoic Mineral Fork Formation, Utah, and the terminal Proterozoic Pertatataka Formation, Australia, are reconsidered using this palaeoecological measure of depositional environment.

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