Type Locality:

Located in Mackenzie Mountains. Sekwi Range, on the first ridge immediately north of June Lake (63°23'N, 128°41'W, Sekwi Mountain map sheet 105P). A reference section located at Caribou Pass 26 km (16 mi) west of June Lake, has also been proposed (63°33'N, 129°12'W).

Distribution:

Presently known outcrops extend from Coal River in Hyland Plateau to Snake River in northern Mackenzie Mountains; a distance of approximately 600 km (373 mi). Recorded thicknesses range between 150 and 1,370 m (492 and 4,495 ft). The formation attains its thickest development near the headwaters of Arctic Red, Stewart and Bonnet Plume rivers in northern Mackenzie Mountains.

Locality Data:

Thickness(m): Minimum 150, Maximum 1370.

Lithology:

Rock types contained within the formation define a coastal plain through continental shelf to continental slope sedimentary sequence. In general, the formation consists of basal brown weathering siltstones and grey and yellow weathering limestones and dolostones. Siltstones are characterized by parallel, wavy and ripple cross-laminations, small scale soft sediment deformation features, burrows, tracks, trails and cm-dm thick, fine-grained, load casted, quartzose sandstones with parallel and ripple cross-laminations. Limestones and dolostones are nodular or parallel bedded mudstones, wackestones, packstones or grainstones and are characterized by burrows, trails, parallel and ripple cross-laminations, slump folds, load casts, rotated nodules, turbidites and breccia deposits. Overlying deposits consist of orange, brown, grey and yellow weathering muddy dolostones, limestones and a lesser fraction of sandstones, siltstones and shales. Dominant are cryptalgal and bioturbated dolostones and limestones. Common sedimentary features of the carbonate rocks are cryptalgalaminates, stromatolites , thrombolites, bird's-eye and laminar fenestrae, desiccation cracks, intraclasts, karst sinkholes and breccias, channels, oscillation ripples with and without desiccation cracks, lingoid ripples with superimposed rill marks, Runzel marks, flat pebble conglomerates, burrows, tracks, trails, burrow mottling, parallel ripple cross-laminations, thin cm-dm sized beds with oolites and fossil coquinas with trilobites and salterellids. Sandstones are quartzose, coarse- to medium-grained, well sorted and are frequently interbedded with siltstones and shales. Predominant sedimentary structures are trough cross-beds, planar tabular cross-stratification, plane-parallel laminations, desiccation cracks, salt casts and bioturbation fabrics like trails, tracks and burrows. Gabrielse et al. (1973) recognized a distinct unit of orange and yellow weathering interbedded limestones and silty and sandy dolostones at the top of the Sekwi Formation west of Mount Ida which they referred to as the Brintnell Member. According to Tipnis et al. (1978), the Rabbitkettle Formation unconformably overlies Lower to Middle Cambrian strata in the southern Mackenzie Mountains. This would include the Sekwi Formation and its Brintnell Member.

Relationship:

Conformably overlies and interdigitates with units 10A and 13 (proposed June Lake Formation) of Sekwi Mountain map sheet. It is overlapped by Road River Formation (formational contacts are conformable in western exposures and unconformable in eastern exposures). It is unconformably overlain by the Broken Skull Formation and, in the southern Mackenzie Mountains, by the Rabbitkettle and Rockslide formations.

Other Citations:

Aitken and Cook, 1974a; Aitken et al., 1973b; Blusson, 1971, 1974; Douglas et al., 1970; Fritz, 1972a, 1973, 1974, 1975, 1976a, 1976b, 1978, 1979; Handfield, 1969, 1971; Krause and Oldershaw, 1977, 1978, 1979; Norris, 1975.

References:

Aitken, J.D. and Cook, D.G., 1974a. Carcajou Canyon map-area, District of Mackenzie Northwest Territories; Geological Survey of Canada, Paper 74-13, 28 p.

Aitken, J.D., Macqueen, R.W., and Usher, J.L., 1973b. Reconnaissance studies of Proterozoic and Cambrian stratigraphy, lower Mackenzie River area (Operation Norman), District of Mackenzie; Geological Survey of Canada, Paper 73-9, 178 p.

Blusson, S.L., 1971. Sekwi Mountain map-area, Yukon Territory and District of Mackenzie (105 P); Geological Survey of Canada, Paper 71-22, 17 p. + "A" Series Map 1333A, Geology, Sekwi Mountain, Northwest Territories - Yukon Territories; Scale: 1:250 000.

Blusson, S.L., 1974. Draft of five geological maps of Operation Stewart, northern Selwyn Basin, Yukon Territory and District of Mackenzie; Geological Survey of Canada, Open File 205.

Douglas, R.J.W., Gabrielse, H., Wheeler, J.O., Stott, D.F., and Belyea, H.R., 1970. Geology of Western Canada, pp. 367-488; in Douglas, RJ.W. (ed.), Geology and Economic Minerals of Canada, Geological Survey of Canada Economic Geology Report, 5th edition,

Fritz, W.H., 1972a. Lower Cambrian trilobites from the Sekwi Formation type section, MacKenzie Mountains, northwestern Canada; Geological Survey of Canada, Bulletin 212, 90 p.

Fritz, W.H., 1973. Medial Lower Cambrian trilobites from the MacKenzie Mountains, northwestern Canada; Geological Survey of Canada, Paper 73-24, 43 p.

Fritz, W.H., 1974. Cambrian biostratigraphy, northern Yukon Territory and adjacent areas; in, Report of Activities, Part A, April to October 1973, Structural geology, stratigraphy and paleontology; Geological Survey of Canada, Paper 74-1 A, pp. 309-313.

Fritz, W.H., 1975. Broad correlations of some Lower and Middle Cambrian strata in the North American Cordillera; in, Report of Activities, April to October 1974; Stratigraphy, Geological Survey of Canada, Paper 75-1, Part A, pp. 533-540.

Fritz, W.H., 1976a. Lower Cambrian stratigraphy, Mackenzie Mountains northwestern Canada; pp. 7-22: in Robinson, R.A. and Powell, A.H. (eds.), Paleontology and depositional environments: Cambrian of Western North America, Brigham Young University Geology.

Fritz, W.H., 1976b. Ten stratigraphic sections from the Lower Cambrian Sekwi Formation, Mackenzie Mountains, northwestern Canada; Geological Survey of Canada, Paper 76-22, 42 p.

Fritz, W.H., 1978. Fifteen stratigraphic sections from the Lower Cambrian of the Mackenzie Mountains, northwestern Canada; Geological Survey of Canada, Paper 77-33, 19 p.

Fritz, W.H., 1979. Cambrian stratigraphic sections between southern Nahanni and Broken Skull rivers, southern MacKenzie Mountains: Geological Survey of Canada; Current Research, Paper 79- 1B, pp. 121-126.

Gabrielse, H., Blusson, S.L., and Roddick, J.A., 1973. Geology of the Flat River, Glacier Lake and Wrigley Lake map-areas, District of Mackenzie and Yukon Territory; Geological Survey of Canada, Memoir 366 (Parts I and II), 421 p.

Handfield, R.C., 1968. Sekwi Formation, a new Lower Cambrian formation in the southern Mackenzie Mountains, District of Mackenzie (95L, 105I, 105P) (Report and 4 figures); Geological Survey of Canada, Paper 68-47, 23 p.

Handfield, R.C., 1969. Early Cambrian coral-like fossils from the Northern Cordillera of Western Canada; Canadian Journal of Earth Sciences = Journal Canadien des Sciences de la Terre, vol. 6, no. 4, part 1, pp. 782-785.

Handfield, Robert C., 1971. Archaeocyatha from the Mackenzie and Cassiar Mountains, Northwest Territories, Yukon Territory and British Columbia; Geological Survey of Canada Bulletin 201, 119 p.

Krause, F.F. and Oldershaw, A.E., 1977. The sedimentology of a shelf to slope transition: the Lower Cambrian Sekwi Formation Mackenzie Mountains, N.W.T., Canada; Geology and Mineralogy Association of Canada, Annual Meeting, vol. 2, p. 30.

Krause, F.F. and Oldershaw, A.E., 1978. Stratigraphic and paleoenvironmental analysis of the Sekwi Formation, Mackenzie Mountains, Northwest Territories; Department of Indian and Northern Affairs, Mineral Industry Report 1975, Northwest Territories EGS 1978-5, pp. 136-156.

Krause, Federico F. and Oldershaw, A.E., 1979. Submarine carbonate breccia beds - a oppositional model for two-layer, sediment gravity flows from the Sekwi Formation (Lower Cambrian), Mackenzie Mountains, Northwest Territories, Canada; Canadian Journal of Earth Sciences = Journal Canadien des Sciences de la Terre, vol. 16, no. 1 (January), pp. 189-199.

Norris, D.K., 1975. Geologic maps of part of Yukon and Northwest Territories, Snake River 106F, Wind River 106E and Hart River 116H (1:250,000); Geological Survey of Canada, Open File Report 279.

Tipnis, R.S., Chatterton, B.D.E., and Ludvigsen, R., 1978. Ordovician conodont biostratigraphy of the southern District of Mackenzie, Canada; pp. 39-91: in Stelck, C.R. and Chatterton, B.D.E. (eds.), Western and Arctic Canadian Biostratigraphy, Geological Association of Canada, Special Paper no. 18, 602 p.