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TitleUpper Ordovician conodont biostratigraphy and revised lithostratigraphy and geological map, Akpatok Island, Ungava Bay, Nunavut
AuthorZhang, S
SourceCanadian Journal of Earth Sciences vol. 55, issue 1, 2017 p. 52-69, https://doi.org/10.1139/cjes-2017-0145
Year2017
Alt SeriesEarth Sciences Sector, Contribution Series 20160440
PublisherNational Research Council Canada
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf; html
ProvinceNunavut
NTS25B/05; 25B/12; 25C/08; 25C/09
AreaAkpatok Island; Gregson Creek; D'Aeth Point; Cox Ridges; Ungava Bay; Canadian Arctic
Lat/Long WENS -68.3833 -67.8667 60.5833 60.4000
Subjectsregional geology; stratigraphy; paleontology; stratigraphic analyses; biostratigraphy; microfossils; conodonts; fossil zones; lithostratigraphy; bedrock geology; lithology; limestones; clasts; Upper Ordovician; Amadjuak Formation; Akpatok Formation; Foster Bay Formation; Belodina confluens; Oulodus velicuspis; Amorphognathus ordovicicus; Plegagnathus dartoni; Rhipidognathus symmetricus; Boas River Formation; Ungava Bay Formation; Frobisher Bay Formation; North Atlantic Province; North American Midcontinent Province; geological mapping; geographic information systems; stratigraphic unit thickness; Phanerozoic; Paleozoic; Ordovician
Illustrationslocation maps; geoscientific sketch maps; stratigraphic cross-sections; stratigraphic charts; biostratigraphic charts; photographs; photomicrographs
ProgramHudson/Ungava, Stratigraphy Petroleum Basins, GEM2: Geo-mapping for Energy and Minerals
ProgramCanada-Nunavut Geoscience Office, Funding Program
ProgramPolar Continental Shelf Program
AbstractStratigraphic units exposed on Akpatok Island, Ungava Bay, Nunavut, were previously recognized as Boas River and Akpatok formations; their biostratigraphic ages and correlations, in particular the stratigraphic position and age of the organic rich "Boas River" Formation, were largely based on limited data. New detailed field observations have recognized three stratigraphic units, namely the Amadjuak, Akpatok, and Foster Bay formations, in which extensive microfossil sampling recovered over 22 000 conodont elements from 66 productive samples from both outcrops and rubble at over 20 localities in four areas. Four Upper Ordovician conodont zones and one unzoned interval are established for the three redefined formations: Belodina confluens and Oulodus velicuspis Interval zones are confined to the exposed Amadjuak Formation and correlated to Edenian and Maysvillian; Amorphognathus ordovicicus - Plegagnathus dartoni Concurrent-range Zone occurs with the Akpatok Formation and correlated to lower Richmondian; Rhipidognathus symmetricus Taxon-range Zone is retained in the Foster Bay Formation and correlated to upper Richmondian; and an "Unzoned Interval" is defined between the last two zones in the lower Foster Bay Formation. The conodont Amorphognathus ordovicicus occurs in both Akpatok and lower Foster Bay formations, and it is also recovered from the bituminous, argillaceous limestone rubble, based on which the stratigraphic position of the previously named "Boas River" Formation is most likely positioned within the lower Foster Bay Formation. The biostratigraphy and lithostratigraphy are combined with geographic information systems (GIS) to establish the thicknesses of the three formations and revise the geologic map of the island.
Summary(Plain Language Summary, not published)
Rocks exposed on Akpatok Island, were previously recognized as Boas River and Akpatok formations; their ages and correlations, in particular the stratigraphic position and age of the organic rich ¿Boas River¿ Formation, were largely based on inference. These rocks are newly recognized as three stratigraphic units by this study, namely the Amadjuak, Akpatok and Foster Bay formations. A great number of conodont microfossils collected at over 20 localities on the island allow establishing four Upper Ordovician conodont zones in the three rock units, and comparing the three rock units to Upper Ordovician Edenina-Masvillian, lower Richmondian and upper Richmondian, respectively. Based on the conodont Amorphognathus ordovicicus recovered from the bituminous argillaceous limestone rubble, the stratigraphic position of the ¿Boas River¿ Formation is most likely within the lower Foster Bay Formation with an age of late Richmondian. The biostratigraphy and lithostratigraphy are combined with GIS to establish the thicknesses of the three formations and revise the geologic map of the island.
GEOSCAN ID299886