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TitleMiddle-Upper Devonian conodont faunas and biostratigraphy of the Horn River Group in the northern Mackenzie Mountains and Plain (NWT, Canada)
AuthorGouwy, S AORCID logo
SourceGeoconvention 2020, abstract archive; 2020 p. 1 Open Access logo Open Access
LinksOnline - En ligne
Alt SeriesNatural Resources Canada, Contribution Series 20200407
MeetingGeoconvention 2020; September 13-15, 2020
DocumentWeb site
Mediaon-line; digital
File formatpdf
ProvinceNorthwest Territories
NTS96C; 96D; 96E; 96F
AreaMackenzie Mountains; Norman Wells; Powell Creek
Lat/Long WENS-128.0000 -125.0000 65.5000 64.5000
Subjectspaleontology; stratigraphy; Nature and Environment; Science and Technology; Upper Devonian; Middle Devonian; biostratigraphy; micropaleontology; microfossils; conodonts; faunas; depositional history; paleoenvironment; index fossils; stratigraphic correlations; sedimentary basins; fossil zones; Mackenzie Plain; Horn River Group; Hare Indian Formation; Bluefish Member; Canol Formation; Ramparts Formation; Kee Scarp Member; Ramparts Plateau Member; Phanerozoic; Paleozoic; Devonian
ProgramGEM2: Geo-mapping for Energy and Minerals Mackenzie Corridor
Released2020 09 01
The Horn River Group (Middle and Upper Devonian) of the northern Mackenzie Mountains and Mackenzie Plain has been a topic of conodont biostratigraphic research since the early 1970's. The drowning of the lower Middle Devonian shelf with deposition of organic-rich black shales (Bluefish Member of the Hare Indian Formation, Canol Formation) and the development of platform and reefal facies (Ramparts Formation) produced diverse paleoenvironments for the study of conodont fauna. Conodonts are important index fossils for regional and interregional correlation in the Devonian and a detailed biostratigraphic framework is essential for understanding facies relationships within the Group, for the regional study of the Horn River Group and for correlation with other sedimentary basins.
This study is based on new sampling during several field campaigns (2016-2019; within NRCan's GEM II and GNES projects), combined with historical GSC conodont collections from the 1970's and 1980's. Conodonts from 16 sections, situated along the northern Mackenzie Mountain front and in the Mackenzie Plain near the town of Norman Wells, were studied for biostratigraphy and faunal diversity. The best-studied section in the study area, Powell Creek, is chosen as conodont biostratigraphic reference section to which other sections are compared and correlated.
In this new framework, most of the Givetian and several of the Frasnian conodont zones are now recognized. The base of the Horn River Group (base of the Hare Indian Formation) is situated within the ensensis Zone. The oldest Ramparts deposits are found in the Middle varcus Zone; its Kee Scarp Member starts in the disparilis Zone and possibly reaches up into the Frasnian Zone 4. The base of the Canol Formation is of Givetian age (hermanni Zone), in the western part of the study area where the Ramparts Formation is not present, but is of latest Givetian age (norrisi Zone) and early Frasnian age above the Ramparts Plateau and Key Scarp members respectively. Conodonts from the top of the Canol Formation suggest a late Frasnian age. Abundance of data depends largely on the lithology, favoring calcareous deposits for sample processing (Ramparts Formation limestone versus Hare Indian and Canol shales with some calcareous beds). Conodont faunas are reasonably diverse in the Hare Indian Formation and increase slightly in diversity and abundance in the Ramparts Formation. This decreases again in the Canol Formation. Using this biostratigraphic framework, multiple anoxic events within the Horn River Group can tentatively be correlated with black-shale events in other sedimentary basins.
Summary(Plain Language Summary, not published)
Conodonts are an extinct group of jawless marine chordates whose feeding apparatus elements or teeth are common microfossils in marine sediments (Cambrian to Triassic, 541Ma-201Ma). The evolution of these elements forms the basis of a relative time framework (biostratigraphy) in which the marine sediments in a basin are positioned. The conodont biostratigraphy allows comparison/correlation of different time-equivalent outcrops in a sedimentary basin and correlation with other basins. A relative time framework is created based on the study of conodont elements from the Middle-Upper Devonian (393Ma-359Ma) Horn River Group in the Mackenzie Mountains and Plain. Most of the key zones in the framework can be recognized and allow a regional and global correlation.

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