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TitleHistory of Mackenzie Arch and its influence on Cambrian sedimentation in the eastern Mackenzie Mountains and adjacent Mackenzie Plain, Northwest Territories
AuthorMacNaughton, R BORCID logo; Pratt, B R; Fallas, K MORCID logo; Turner, E C
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Abstracts Volume vol. 37, 2014 p. 171 Open Access logo Open Access
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20140062
PublisherGeological Association of Canada
MeetingGAC-MAC 2014; Joint annual meeting of Geological Association of Canada and Mineralogical Association of Canada; Fredericton, NB; CA; May 21-23, 2014
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthwest Territories
AreaMackenzie Mountains; Mackenzie Plain
Subjectssedimentology; depositional history; sedimentary rocks; silts; carbonates; Mackenzie Arch; Mackenzie Mountains Supergroup; Paleozoic; Cambrian
ProgramGEM: Geo-mapping for Energy and Minerals Mackenzie Delta and Corridor
AbstractMackenzie Arch was an elongate, northwest - trending, positive tectonic element in the eastern Mackenzie Mountains. Studies carried out during the GSC's Geo - mapping for Energy and Minerals (GEM) Program permit the history of the Arch and its influence on sedimentation to be reconstructed in more detail than previously was possible. Mackenzie Arch is cored by strata of the early Neopro terozoic Mackenzie Mountains Supergroup. The Arch may have formed during the late Cryogenian to Ediacaran and its present - day southwest flank essentially marks the eastern limit of the Windermere Supergroup. By the Cambrian, uplift of the Arch had led to local erosional removal of more than a kilometre of the upper Mackenzie Mountains Supergroup. Facies belts were well - developed west of the Arch during the Terreneuvian (earliest Cambrian). East of the Arch, the age of the oldest Cambrian deposits is not well constrained. The oldest trilobite faunas east of the Arch, from shale of the basal Mount Cap Formation, belong to Cambrian Stage 2 (traditional Bonnia - Olenellus Biozone). However, the underlying Mount Clark Formation is dominated by intensely burro wed quartz sandstone that records earlier Cambrian deposition of uncertain duration. On the east flank of Mackenzie Arch, Mount Clark Formation formed a sand - dominated, nearshore facies belt that passed eastward into shalier facies of the lower Mount Cap Formation. These facies belts persisted until early in Cambrian Stage 5 (traditional early Middle Cambrian), when transgression led to deposition of shale - dominated upper Mount Cap Formation across a wide region, persisting until late in Stage 5. Uplift of Mackenzie Arch, recorded by westward erosional bevelling of Mount Cap Formation, was followed by deposition of red beds across the crest of Mackenzie Arch. The distribution of red beds delineates local depocentres and highs along the crest of the Arch. To the east, deposition of the correlative, evaporite - bearing Saline River Formation reflects the impact of the uplifted Arch on basin circulation during a poorly constrained period of time that may have encompassed part of the Drumian and Guzhangian (tr aditional mid - to late Middle Cambrian). By late Guzhangian (traditional latest Middle Cambrian) time, a restricted carbonate platform had developed across the study region, leading to deposition of Franklin Mountain Formation. The basal carbonates of th at unit contain quartz sand and silt in proportions that reflect proximity to Mackenzie Arch, but the influence of the Arch was minor by the end of the Cambrian.
Summary(Plain Language Summary, not published)
Mackenzie Arch was a broad, elongate, elevated region that existed roughly between 541 million and 485 million years ago. It stood high in what is now the eastern Mackenzie Mountains of the Northwest Territories. It separated an enclosed marine basin to the present-day east (now the Mackenzie Plain oil and gas exploration region) from an open ocean basin (Selwyn Basin) to the present-day west. This conference talk will describe the ways in which Mackenzie Arch controlled the deposition, erosion, and preservation of sedimentary rocks during its existence.

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