Type Locality:

The type section (Section 6) is in the Misty Creek Embayment at 62°42'N, 130°47'W, 2 km southwest of Goober Lake (64°44'N, 130°45'W) in the Bonnet Plume Lake (106 B) map area (Cecile, 1982).

Distribution:

The Hess River Formation is recognized everywhere in the Misty Creek Embayment, and on the Niddery High. Within the embayment, thicknesses vary from 100 m near the margin to between 1270+ and 2530 m in central bsin locations. The 2530 m thickness includes 1580 m of quartz sandstone-shale flysch (Hess River flysch) (Cecile, 1982). The Hess River Formation outcrops across the eastern two thirds of the northeastern Niddery Lake map area (Cecile, 1997a, b, d). It is also mapped in the southeastern part of the Niddery Lake map area (Abbott, 1983a; Cecile and Abbott, 1992) (Cecile, 2000).

Lithology:

At its type section the Hess River Formation consists of 60 m of black shale overlain by 360 m of interbedded calcareous shale and argillaceous limestone, with minor barite and phosphate. In the centre of the Misty Creek Embayment the Hess River Formation is more than 1270 m thick, and in the northwest part of the embayment, where it includes a thick succession of quartz sandstone-shale flysch, 2530 m thick. In the central southeastern Niddery Lake map area the Hess River Formation outcrops on the Niddery High. There is between 38 and 115 m thick - less than one tenth the thickness in the adjacent Misty Creek Embayment. This thin succession consists of shale and calcareous shale with some thin bedded limestone. On the southwest limb of the Border Anticline in the northern part of the study area, partly exposed Hess River Formation is thin and anomalous. There is apparently less than 40 m thick and composed dominantly of chert (see outcrops around UTM co-ordinates 433750 E and 7085950 N, Zone 9, NTS 105-O/16) (Cecile, 2000).

Relationship:

All contacts with the underlying Sekwi Formation are conformable and distinct. The contact is marked where shale is more abundant than limestone and can usually be placed to within a metre. The Rabbitkettle Formation is in distinct but conformable contact with the underlying Hess River Formation. The boundary is marked where limestone dominates over shale and can usually be placed to within a metre. The Hess River Formation is continuous into the Misty Creek Embayment to the north, east and southeast. The Hess River Formation is correlative with part of the Mount Cap Formation (glauconitic sandstone, shale, thin bedded limestone) found on the eastern side of the Mackenzie-Redstone Arch. In the southern Mackenzie Mountains it is correlative with a platform dolostone succession (Avalanche Formation), and a basin or slope thin bedded limestone succession, which is a lateral equivalent of the dolostone (Rockslide Formation; Cecile, 1982). In the Nahanni map area the Avalanche Formation is transitional into the Rockslide Formation from the Blackwater Platform on the southeast to the Misty Creek Embayment on the northwest, respectively (Gordey and Anderson, 1993). Farther northwest it is then transitional into the Hess River Formation in the Misty Creek Embayment. In the western northeastern Niddery Lake map area and western Niddery Lake map area the Hess River Formation is thought to be correlative with part of the Gull Lake Formation. Also, Middle Cambrian strata are not separately mappable in the southwestern part of the Nahanni map area (Selwyn Basin) where equivalent beds may also be included within the Gull Lake Formation (Gordey and Anderson, 1993) (Cecile, 2000). Towards the edges of the embayment, it is probable that some Hess River Formation has been removed during sub-Franklin Mountain erosion, and here the upper contact would be a disconformity between tongues of Franklin Mountain Formation or transitional Franklin Mountain dolostone. On the Mackenzie and eastern Ogilvie arches the Hess River Formation is not present below Franklin Mountain Formation, and is equivalent to a period of non-depostion or to strata removed by pre-Late Cambrian erosion in platform areas around the embayment. The Hess River Formation probably extends south across the Sekwi Mountain map area, Unit 13 of Blusson (1971), but continuing south into the west-central Nahanni (105 I) map area it is missing beneath a sub-Rabbitkettle unconformity (Gordey, 1978, 1979) (Cecile, 1982).

History:

The Hess River is a geographic name for a major river in the southern embayment area (Cecile, 1982).

Remark:

The Hess River Formation is a deep-water facies unit consisting of shale with some thin bedded limestone. The variation in thickness in the northeastern Niddery Lake map area may be a result of its diachronous relationship with they Sekwi Formation or may reflect subtle local relief at the time of deposition. The apparent local dominance of chert is anomalous (Cecile, 2000).

References:

Abbott, J.G., 1983. Geology of the MacMillian fold Belt, 105-O S.E. and parts of 105-P S.W.; Exploration and Geological Services Devision, Department of Indian and Northern Affairs, Open File Report (unnumbered) (3 maps and legend; scale 1:50 000).

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.

Cecile, M.P., 1982. The lower Paleozoic Misty Creek Embayment, Selwyn Basin, Yukon and Northwest Territories; Geological Survey of Canada, Bulletin 335, 78 p.

Cecile, M.P., 1997a. Geology of the Thor Hills map area (NTS 105-O/15); Geological Survey of Canada, Map 1899A, Scale: 1:50 000.

Cecile, M.P., 1997b. Geology of NTS 105-O/09 and northern part of Keele Peak map area (NTS 105-O/08); Geological Survey of Canada, Map 1902A. Scale: 1:50 000.

Cecile, M.P., 1997d. Geology of the Hailstone Creek map area (NTS 105-O/16); Geological Survey of Canada, MAp 1900A, Scale: 1:50 000.

Cecile, M.P., 2000. Geology of the northeastern Niddery Lake map area, east-central Yukon and adjacent Northwest Territories; Geological Survey of Canada, Bulletin 553, 120 p.

Cecile, M.P., and Abbott, J.G., 1992. Geology of the Niddery Lake map area (NTS 105-O) at 1:250 000; Geological Survey of Canada, Open File 2465, 1 geological map (Scale 1:250 000) + 1 geological legend.

Fritz, W.H., Norford, B.S., and Tipnis, R.S., 1982. Paleontologic Appendix; in The Lower Paleozoic Misty Creek Embayment, Selwyn Basin, Yukon and Northwest Territories, (ed.) Cecile, M.P.; Geological Survey of Canada, Bulletin 335.

Gordey, S.P. and Anderson, R.G., 1993. Evolution of the northern Cordilleran miogeocline, Nahanni map area (105I), Yukon Territory and District of Mackenzie; Geological Survey of Canada, Memoir 428, 214 p.

Gordey, S.P., 1979. Stratigraphy of the southeastern Selwyn Basin in the Summit Lake area, Yukon and Northwest Territories; in, Current Research, Part A; Geological Survey of Canada, Paper 79-1A, pp.13-16.

Gordey. S.P., 1978. Stratigraphy and structure of the Summit Lake area, Yukon and Northwest Territories; in, Current Research, Part A, Blackadar, R.G., Griffin, P.J., Dumych, H., Irish, E.J.W. (Eds.); Geological Survey of Canada, Paper 78-1A, pp. 43-48.