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TitleNew conodont data constraining the age of the 'Bear Rock assemblage' in the Colville Hills, Northwest Territories
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorGouwy, S AORCID logo; MacNaughton, R BORCID logo; Fallas, K MORCID logo
SourceGeological Survey of Canada, Current Research (Online) 2017-3, 2017, 11 pages, Open Access logo Open Access
PublisherNatural Resources Canada
Mediaon-line; digital
File formatpdf
ProvinceNorthwest Territories
NTS96K; 96L; 96M; 96N
AreaColville Hills; Colville Lake; Aubrey Lake; Lac Maunoir; Lac Bélot; Lac Des Bois; Hare Indian River
Lat/Long WENS-128.0000 -124.0000 68.0000 66.0000
Subjectsstratigraphy; paleontology; bedrock geology; lithology; sedimentary rocks; limestones; dolostones; brecciation; laminations; micropaleontology; systematic paleontology; microfossils; conodonts; fossil assemblages; fossil descriptions; biostratigraphy; Middle Devonian; Eifelian; Lower Devonian; Emsian; stratigraphic analyses; stratigraphic correlations; thermal maturation; thermal history; thermal alteration; hydrothermal alteration; thermal alteration index; colour alteration index; lithostratigraphy; unconformities; Bear Rock Formation; Bear Rock assemblage; Arnica Formation; Landry Formation; Ramparts Formation; Hare Indian Formation; Hume Formation; Mount Kindle Formation; Phanerozoic; Paleozoic; Devonian
Illustrationsgeoscientific sketch maps; stratigraphic charts; photographs; photomicrographs
ProgramGEM2: Geo-mapping for Energy and Minerals Mackenzie Corridor, Shield-to-Selwyn geo-transect, Mackenzie-Selwyn sub-activity
Released2017 12 05
AbstractIn the Colville Hills region of the Northwest Territories, the Lower to Middle Devonian succession consists of variably brecciated limestone and dolostone that historically has been assigned to the Bear Rock Formation. Nonbrecciated strata within this interval can be assigned to the Arnica and Landry formations, but bedrock exposure is too sparse to permit these units to be mapped. In view of the internal complexity of this stratigraphic succession, the term 'Bear Rock assemblage' is applied to this interval. Only limited age constraints on these strata have been reported. Conodont assemblages collected in 2015 demonstrate that the succession ranges from lowermost Emsian to lower Eifelian (dehiscens to costatus zones). This is comparable to the inferred age of Bear Rock Formation in the Franklin Mountains and Mackenzie Mountains. Thermal alteration of most samples is low, but one sample records evidence of higher maximum temperatures, possibly related to hydrothermal alteration.
Summary(Plain Language Summary, not published)
This report describes rocks deposited during the Early to Middle Devonian Epochs in the present-day Colville Hills. The rocks consist of limestone and dolostone. In many places, the originally bedded rocks were broken up into a mass of angular rock fragments, and then cemented together as a kind of rock called a breccia. These rock types will be grouped together as the 'Bear Rock assemblage' on new bedrock geology maps for the Colville Hills. Phosphatic microfossils (tiny teeth) called conodonts have been recovered from these rocks. The conodonts confirm that the rocks belong to the Emsian and Eifelian Ages (roughly 387-407 million years ago). The preservation of the conodonts shows that some parts of the Colville Hills were affected by very hot (hydrothermal) groundwater at some point after the time of the fossils.

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