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Sekwi Formation

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Journal Article

New information on olenelline trilobites from the Cambrian Sekwi Formation in northwestern Canada

Francine R. Abe, Bruce S. Lieberman, Michael C. Pope, Kelly Dilliard
Published: 12 November 2010
Canadian Journal of Earth Sciences (2010) 47 (12): 1445–1449.
DOI: https://doi.org/10.1139/E10-073
...Francine R. Abe; Bruce S. Lieberman; Michael C. Pope; Kelly Dilliard Abstract A new species of olenelline trilobite, Nevadella keelensis , is described from the Early Cambrian (Cambrian Series 2, Stage 3) in the Sekwi Formation, Mackenzie Mountains, Canada. The difficulty in discerning between...
FIGURES
View PDF for article title, New information on olenelline trilobites from the Cambrian <span class="search-highlight">Sekwi</span> <span class="search-highlight">Formation</span> in northwestern Canada
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Journal Article

NEW CHANCELLORIIDS FROM THE EARLY CAMBRIAN SEKWI FORMATION WITH A COMMENT ON CHANCELLORIID AFFINITIES

ROBERT D. RANDELL, BRUCE S. LIEBERMAN, STEPHEN T. HASIOTIS, MICHAEL C. POPE
Published: 01 September 2005
Journal of Paleontology (2005) 79 (5): 987–996.
DOI: https://doi.org/10.1666/0022-3360(2005)079[0987:NCFTEC]2.0.CO;2
...ROBERT D. RANDELL; BRUCE S. LIEBERMAN; STEPHEN T. HASIOTIS; MICHAEL C. POPE Abstract Articulated scleritomes of the chancelloriids Archiasterella fletchergryllus new species and Chancelloria cf. eros Walcott, 1920 are described from the Early Cambrian (Branchian) Sekwi Formation, Mackenzie...
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View PDF for article title, NEW CHANCELLORIIDS FROM THE EARLY CAMBRIAN <span class="search-highlight">SEKWI</span> <span class="search-highlight">FORMATION</span> WITH A COMMENT ON CHANCELLORIID AFFINITIES
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Journal Article

Submarine carbonate breccia beds—a oppositional model for two-layer, sediment gravity flows from the Sekwi Formation (Lower Cambrian), Mackenzie Mountains, Northwest Territories, Canada

F. F. Krause, A. E. Oldershaw
Published: 01 January 1979
Canadian Journal of Earth Sciences (1979) 16 (1): 189–199.
DOI: https://doi.org/10.1139/e79-017
...F. F. Krause; A. E. Oldershaw Abstract In the Sekwi Formation, carbonate breccia beds interbedded with slope sediments are interpreted as submarine sediment gravity flows that formed a two-layer deposit during a single transport event. They are intermediate between true slumps and turbidites...
Add to Citation Manager for Submarine carbonate breccia beds—a oppositional model for two-layer, sediment gravity flows from the <span class="search-highlight">Sekwi</span> <span class="search-highlight">Formation</span> (Lower Cambrian), Mackenzie Mountains, Northwest Territories, Canada
Image
Representative trilobites from units 1 (Sekwi Formation), 2 (Hess River Formation), and 4 (Hess River Formation) demonstrate that all three units belong to the upper Bonnia–Olenellus Zone. All specimens are identified by a Geological Survey of Canada (GSC) location number (“C-number”) followed by a reference number referring to the national collection of type and figured specimens at the GSC in Ottawa; suffix “a” indicates that the figured material is a cast or mould. (A) Indet. dorypygid Unit 1. GSC location C-625728, GSC 142649. Partial cranidium. Sample U1-F, specimen 1. (B) Ogygopsis sp. Unit 1. GSC location C-625728, GSC 142650. Pygidium. Sample U1-G, specimen 1. (C) Ogygopsis cf. Ogygopsis batis Unit 4, GSC location C-625730, GSC 142651. Cranidium. Sample U4-E, specimen 1. (D) Ogygopsis cf. Ogygopsis batis Unit 4, GSC location C-625730, GSC 142652. Pygidium. Sample U4-G, specimen 1. (E) Kootenia marcoui Unit 2, GSC location C-625729, GSC 142653. Cranidium. Sample U2-H, specimen 3. (F) Kootenia marcoui Unit 2, GSC location C-625729, GSC 142654a. Silicone putty cast of external mould of pygidium. Sample U2-C, specimen 1. (G) Olenellus cf. Olenellus parvofrontatus Unit 2, GSC location C-625729, GSC 142655a. Silicone putty cast of external cephalic mould. Sample U2-O, 1. (H) Zacanthopsis? sp. Unit 2, GSC location C-625729, GSC 142656. Cranidium. Sample U2-C, specimen 7. (I) Zacanthopsis cf. Zacanthopsis expansa Unit 4, GSC location C-625730, GSC 142657a. Silicone putty cast of external mould of cranidium. Sample U4-R, specimen 8. (J) “Syspacephalus” sp. Unit 4, GSC location C-625730, GSC 142658. Sample U4-Q, specimen 4.

Representative trilobites from units 1 (Sekwi Formation), 2 (Hess River For...

Published: 23 February 2022
Fig. 7. Representative trilobites from units 1 (Sekwi Formation), 2 (Hess River Formation), and 4 (Hess River Formation) demonstrate that all three units belong to the upper Bonnia–Olenellus Zone. All specimens are identified by a Geological Survey of Canada (GSC) location number (“C-number
Image
Figure1—Location of study area and outcrop of the Sekwi Formation. 1, Map of North America showing the location of the study area, Mackenzie Mountains, Northwest Territories, Canada. 2, Geological map of study area showing outcrop of the Sekwi Formation and major tectonic features, modified from Blusson (1971a, 1971b). The filled circle marks locality 1

Figure 1 —Location of study area and outcrop of the Sekwi Formation. 1, ...

Published: 01 September 2005
Figure 1 —Location of study area and outcrop of the Sekwi Formation. 1, Map of North America showing the location of the study area, Mackenzie Mountains, Northwest Territories, Canada. 2, Geological map of study area showing outcrop of the Sekwi Formation and major tectonic features, modified
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Figure2—Lithological column of the Sekwi Formation; the section yielding the chancelloriids is indicated

Figure 2 —Lithological column of the Sekwi Formation; the section yielding...

Published: 01 September 2005
Figure 2 —Lithological column of the Sekwi Formation; the section yielding the chancelloriids is indicated
Journal Article

Biostratigraphic evidence for incremental tectonic development of early Cambrian deep-water environments in the Misty Creek embayment (Selwyn basin, Northwest Territories, Canada)

R. William Scott, Elizabeth C. Turner, Robert B. MacNaughton, Karen M. Fallas
Published: 23 February 2022
Canadian Journal of Earth Sciences (2022) 59 (4): 216–231.
DOI: https://doi.org/10.1139/cjes-2021-0049
...Fig. 7. Representative trilobites from units 1 (Sekwi Formation), 2 (Hess River Formation), and 4 (Hess River Formation) demonstrate that all three units belong to the upper Bonnia–Olenellus Zone. All specimens are identified by a Geological Survey of Canada (GSC) location number (“C-number...
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View PDF for article title, Biostratigraphic evidence for incremental tectonic development of early Cambrian deep-water environments in the Misty Creek embayment (Selwyn basin, Northwest Territories, Canada)
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(A) Chronology of Sekwi and Hess River formations, based on compilation of the standard genus-based biostratigraphic scheme for lower and middle Cambrian (Fritz 1972; Hollingsworth 2007), time scale of Peng et al. (2020), and global isotope excursions adapted from Geyer (2019). The positions of some biozones and chemostratigraphic excursions against the global time scale are not well established. (B) Sekwi Formation section 4 (Dilliard et al. 2007), showing general lithologies, trilobite biostratigraphy, carbon isotope chemostratigraphy, and sequence stratigraphy. The Cambrian arthropod radiation isotope excursion (CARE), Mingxinsi carbon isotope excursion (MICE), and archaeocyathan extinction isotope excursion (AECE) are evident in the Sekwi Formation curve. The redlichiid–olenellid extinction carbon isotope excursion (ROECE) may be present in either uppermost Sekwi Formation or lowermost Hess River Formation. The Zhujiaqing carbon isotope excursion (ZHUCE), Shiyantou carbon isotope excursion (SHICE), and early Atdabanian/Repinaella Zone excursion (EAREZE) are in Cambrian stages 2 and 3 prior to Sekwi Formation deposition (Geyer 2019). The Drumian carbon isotope excursion (DICE) is in the lower Hess River Formation (Turner 2015). [Colour online.]

(A) Chronology of Sekwi and Hess River formations, based on compilation of ...

Published: 23 February 2022
Fig. 2. (A) Chronology of Sekwi and Hess River formations, based on compilation of the standard genus-based biostratigraphic scheme for lower and middle Cambrian ( Fritz 1972 ; Hollingsworth 2007 ), time scale of Peng et al. (2020) , and global isotope excursions adapted from Geyer (2019
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(A) Cross-section of the Misty Creek embayment (MCE; green line A–A′ in Fig. 1) compiled from sections from Fritz (1978) and Cecile (1982). Along the deep-water axis of the MCE, Sekwi – Hess River formational contact is in middle Bonnia–Olenellus Zone, but in southwestern and northeastern MCE areas, the contact is in the upper Bonnia–Olenellus Zone. At the northeastern MCE margin, Sekwi – Hess River contact is unconformable (lowermost Hess River Formation is middle Cambrian). Panel is hung from base of middle Cambrian. (B) Tectonic interpretation of the initiation of MCE deep-water sedimentation in the Cambrian through extension-related normal faulting, depicted along a hypothetical SW–NE cross-section. (0) Sekwi Formation was deposited on a west-facing carbonate ramp during Fallotaspis, Nevadella, and early Bonnia–Olenellus zones. (1) Normal faulting caused subsidence during middle Bonnia–Olenellus Zone, in the area where the contact age is in middle Bonnia–Olenellus Zone and Hess River Formation is thickest (Fig. 4). Deep-water Hess River Formation facies began to accumulate in the narrow, newly deepened axial area, but shallower-water Sekwi Formation deposition continued nearby. (2) Further extension and subsidence occurred more broadly during late Bonnia–Olenellus Zone, causing change to deep-water Hess River Formation depositional environments throughout most of the MCE. Uplift caused erosion of easternmost upper Sekwi Formation. (3) Continued regional subsidence or eustatic sea-level rise led to deposition of Hess River Formation lithofacies in middle Cambrian throughout the entire sub-basin. Sekwi – Hess River contact near embayment margin (Mackenzie–Redstone arch) is unconformable. Configuration of northwestern margin of MCE and northwestern extent of the area of middle Bonnia–Olenellus Zone Sekwi – Hess River contact age are not known owing to exposure constraints. [Colour online.]

(A) Cross-section of the Misty Creek embayment (MCE; green line A–A′ in Fi...

Published: 23 February 2022
Fig. 8. (A) Cross-section of the Misty Creek embayment (MCE; green line A–A′ in Fig. 1 ) compiled from sections from Fritz (1978) and Cecile (1982) . Along the deep-water axis of the MCE, Sekwi – Hess River formational contact is in middle Bonnia–Olenellus Zone, but in southwestern
Journal Article

Palynology of uppermost Proterozoic and lowermost Cambrian formations, central Mackenzie Mountains, northwestern Canada

D. Baudet, J. D. Aitken, M. Vanguestaine
Published: 01 January 1989
Canadian Journal of Earth Sciences (1989) 26 (1): 129–148.
DOI: https://doi.org/10.1139/e89-011
...D. Baudet; J. D. Aitken; M. Vanguestaine Abstract The acritarch assemblages of strata from the base of the Upper Proterozoic Sheepbed Formation to the base of the Lower Cambrian (Atdabanian) Sekwi Formation are described. The sections sampled are in southwestern (internal) structural units where...
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Journal Article

Evolution of a Mixed Carbonate/Terrigenous Platform: Lower Cambrian Continental Terrace Wedge of Mackenzie Mountains, Northwest Territories, Canada: ABSTRACT

F. F. Krause
Journal: AAPG Bulletin
Published: 01 May 1982
AAPG Bulletin (1982) 66 (5): 590.
DOI: https://doi.org/10.1306/03B59ECC-16D1-11D7-8645000102C1865D
...F. F. Krause Rocks of the Sekwi Formation and underlying siltstones of G.S.C. units 10A and 13 exposed in the western Mackenzie Mountains define a continental terrace wedge that evolved during the Early Cambrian on the northwestern flanks of the North American continent. Growth of the continental...
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Journal Article

Early Cambrian coral-like fossils from the Northern Cordillera of Western Canada

Robert C. Handfield
Published: 01 August 1969
Canadian Journal of Earth Sciences (1969) 6 (4): 782–785.
DOI: https://doi.org/10.1139/e69-074
...Robert C. Handfield Abstract Tabulaconus kordeae , n. gen., n. sp., is a coral-like fossil found in the Sekwi Formation, Mackenzie Mountains, District of Mackenzie and the Atan Group, Cassiar Mountains, British Columbia. The species consists of small, conical shells with a layered external wall...
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Image
Probable syndepositional normal fault in Hess River Formation in NTS 106-B between study location and section C10 (see Fig. 6). Hess River Formation thickens from approximately 40 to 150 m across a normal fault offsetting strata of the Hess River and Sekwi formations. Overlying Rabbitkettle Formation and younger strata are unaffected. Down-dropped side of fault (southwest) indicated by symbols. DL, Duo Lake Formation; HR, Hess River Formation; R, Rabbitkettle Formation; Sk, Sekwi Formation. Topography from the Canadian Digital Elevation Model (Natural Resources Canada 2015), 20 m resolution, accessed April 2015. Map generated in ArcMap 10.7.1. [Colour online.]

Probable syndepositional normal fault in Hess River Formation in NTS 106-B ...

Published: 23 February 2022
Fig. 9. Probable syndepositional normal fault in Hess River Formation in NTS 106-B between study location and section C10 (see Fig. 6 ). Hess River Formation thickens from approximately 40 to 150 m across a normal fault offsetting strata of the Hess River and Sekwi formations. Overlying
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Figure6—Chancelloria cf. eros, KUMIP 308850, Early Cambrian (Branchian), Sekwi Formation, Northwest Territories, Canada, locality 1, ×2.2

Figure 6 — Chancelloria cf. eros , KUMIP 308850, Early Cambrian (Branchi...

Published: 01 September 2005
Figure 6 — Chancelloria cf. eros , KUMIP 308850, Early Cambrian (Branchian), Sekwi Formation, Northwest Territories, Canada, locality 1, ×2.2
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(A) Isopach map showing thickness of the Bonnia–Olenellus Zone in the Sekwi Formation, after Chan et al. (2019), with 1:250 000 NTS map-sheet numbers. Red square shows eventual location of Misty Creek embayment (MCE). (B) Isopach map of entire Hess River Formation in MCE, after Cecile (1982). Red square outlines same geographic area as red square in Fig. 3A. Cambrian–Ordovician shallow- to deep-water facies boundary serves as a general outline of the MCE. Area of thickest Sekwi Bonnia–Olenellus Zone in NTS 106B (A) closely corresponds to deep-water axis of the MCE (B). [Colour online.]

(A) Isopach map showing thickness of the Bonnia–Olenellus Zone in the Sek...

Published: 23 February 2022
Fig. 3. (A) Isopach map showing thickness of the Bonnia–Olenellus Zone in the Sekwi Formation, after Chan et al. (2019) , with 1:250 000 NTS map-sheet numbers. Red square shows eventual location of Misty Creek embayment (MCE). (B) Isopach map of entire Hess River Formation in MCE, after
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Exposure at study location (64°35′35.178″N, 130°46′19.218″E). Sekwi Formation (unit 1) is in foreground; Hess River Formation (units 2–4 and above) continues up-section into the distance. Graphic log at right shows estimated thicknesses and summary of rock types. [Colour online.]

Exposure at study location (64°35′35.178″N, 130°46′19.218″E). Sekwi Formati...

Published: 23 February 2022
Fig. 5. Exposure at study location (64°35′35.178″N, 130°46′19.218″E). Sekwi Formation (unit 1) is in foreground; Hess River Formation (units 2–4 and above) continues up-section into the distance. Graphic log at right shows estimated thicknesses and summary of rock types. [Colour online.]
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Distribution of the occurrences Reticella corrugata in the Cambrian. Comparable acritarch assemblages from the early Cambrian are marked with shaded fields on the palaeogeographical reconstruction of the continents in the early Cambrian. Records of R. corrugata from the Lükati Formation, Estonia, as well as synonymised records from the Brennæter shale, Norway; Skiag Bridge, Scotland; Oville Formation, Spain and Sekwi Formation, Canada, are marked with black dots. Modified from McKerrow &amp; Cocks (1995) and Moczydłowska (1998).

Distribution of the occurrences Reticella corrugata in the Cambrian. Comp...

Published: 01 November 2016
Formation, Estonia, as well as synonymised records from the Brennæter shale, Norway; Skiag Bridge, Scotland; Oville Formation, Spain and Sekwi Formation, Canada, are marked with black dots. Modified from McKerrow & Cocks (1995) and Moczydłowska (1998) .
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Figure5—Microscopic cyanobacterial fabric (possibly GirvanellaNicholson and Etheridge, 1878) from within the microbial framework encrusting a scleritome of Archiasterella fletchergryllus n. sp., KUMIP 308859, Early Cambrian (Branchian), Sekwi Formation, Northwest Territories, Canada, locality 1; the upward doming confirms the paleo-orientation; indistinct radial microbial fabrics are more usual; cellular and possibly algal fabrics also occur (thin section, plane-polarized transmitted light), ×120

Figure 5 —Microscopic cyanobacterial fabric (possibly Girvanella Nichols...

Published: 01 September 2005
Figure 5 —Microscopic cyanobacterial fabric (possibly Girvanella Nicholson and Etheridge, 1878 ) from within the microbial framework encrusting a scleritome of Archiasterella fletchergryllus n. sp., KUMIP 308859, Early Cambrian (Branchian), Sekwi Formation, Northwest Territories, Canada
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Fig. 3. Specimens collected from the Nevadella zone, Cambrian Series 2, S...

Published: 12 November 2010
Fig. 3. Specimens collected from the Nevadella zone, Cambrian Series 2, Stage 3, in the Sekwi Formation, Northwest Territories, Canada. ( a ) and ( b ) Esmeraldina sp. aff. rowei ( Walcott, 1910 ). ( a ) cephalon, dorsal view, KUMIP 315001, ×2.0; ( b ) oblique view of ( a ) ×2.0. ( c ) and ( d
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Figure9—Archiasterella fletchergryllus n. sp., Early Cambrian (Branchian), Sekwi Formation, Northwest Territories, Canada, locality 1. 1, Paratype KUMIP 308855, partially articulated scleritome close to basal tip, length of basal ray decreases exponentially towards the basal tip, lateral rays become highly reduced, ×5.9; 2, holotype KUMIP 308851, detail of sclerite (pale) in situ on body surface, view is equivalent to that in Figure 3.4 but with basal ray broken away; lateral rays lie parallel to the body surface, the microbialite crust (dark) is particularly dense around the sclerite (equivalent to the pale crust in Fig. 4), ×7.8

Figure 9 — Archiasterella fletchergryllus n. sp., Early Cambrian (Branchi...

Published: 01 September 2005
Figure 9 — Archiasterella fletchergryllus n. sp., Early Cambrian (Branchian), Sekwi Formation, Northwest Territories, Canada, locality 1. 1, Paratype KUMIP 308855, partially articulated scleritome close to basal tip, length of basal ray decreases exponentially towards the basal tip, lateral