Sunblood Formation

Unit Name: Sunblood Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Middle Ordovician (471.8 - 460.9 ma)
Age Justification: Formation is sparsely fossiliferous. Fossils include trilobites, brachiopods ostra-codes, bryozoans, bivalves, cephalopods and conodonts.
Province/Territory: Northwest Territories

Originator: Kingston, 1951 (revised by Douglas and Norris, 1960b).

Type Locality:

Sunblood Mountain from cairn to base of Virginia Falls, Sunblood Range, District of Mackenzie, 61°31'N, 125°44'W. The "type reference section" established by Gabrielse et al. (1973) in the Thundercloud Range includes strata assignable to the Sunblood, Esbataottine, and Whittaker formations (Ludvigsen, 1975, p. 668).

Distribution:

Southern Mackenzie Mountains between Whittaker Range, Natla River, and Mary Range. About 1,000 m (3,281 ft) thick at type section, but here the base is not exposed. Maximum thickness of 1,040 m (3,412 ft) in Thundercloud Range. Sunblood thins towards the north to 500 m (1,640 ft) at Grizzly Bear Lake, 300 m (984 ft) at Whittaker Range, and 230 m (755 ft) near Natla River.

Locality Data:

Thickness(m): Minimum 230, Maximum 1040, Typical 1000.

Lithology:

At the type locality, the Sunblood consists of generally micritic, grey, thin- to thick-bedded limestones that weather in shades of grey, orange, pink and buff due to silt content. Limestones are commonly finely laminated and mud cracks are common. Sparites and finely crystalline dolostones are uncommon. An arenaceous unit forms top of Sunblood in Sunblood, Whittaker, and Thundercloud ranges. Towards the north, the formation changes to grey, finely to medium crystalline dolostones. The Sunblood is generally resistant.

Relationship:

Conformably (?) overlies Broken Skull Formation. Conformably overlain by Esbataottine Formation and disconformably overlain by Whittaker Formation. To the west, Sunblood passes into dark shales of Road River Formation, but details of this facies change are unknown. It unconformably overlies the Nonda Formation in parts of the southern Yukon.

Other Citations:

Copeland, 1974, 1978; Douglas and Norris, 1961; Gordey, 1979; D.E. Jackson, 1978; Ludvigsen, 1978, 1979; Tipnis et al., 1978.

References:

Copeland, M.J., 1974. Middle Ordovician ostracoda from southwestern District of Mackenzie; Geological Survey of Canada, Bulletin 244, 55 p.

Copeland, M.J., 1978. Early Paleozoic ostracode assemblages, northwestern Canada; pp. 93-111: 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.

Douglas, R.J.W. and Norris, D.K., 1960b. Virginia Falls and Sibbeston Lake map-areas, Northwest Territories (95F and 95G); Geological Survey of Canada, Paper 60-19, 26 p.

Douglas, R.J.W. and Norris, D.K., 1961. Camsell Bend and Root River map-areas, Northwest Territories; Geological Survey of Canada, Paper 61-13, 36 p.

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.

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.

Jackson, D.E., 1978. Recent developments in graptolite research; pp. 113-131: in Stelck, C.R. and Chatterton, B.D.E. (eds,), Western and Arctic Canadia Biostratigraphy, Geological Association of Canada Special Paper no. 18, 602 p.

Kingston, Dave Russell, 1951. Stratigraphic reconnaissance along the Upper south Nahanni River, N.W.T.; America Association of Petroleum Geologists (AAPG), AAPG Bulletin, vol. 35, no. 11 (November), pp. 2409-2426.

Ludvigsen, R., 1975. Ordovician formations and faunas, southern Mackenzie Mountains; Canadian Journal of Earth Sciences = Journal Canadien des Sciences de la Terre, vol. 12, no. 4, pp. 663-697.

Ludvigsen, R., 1978. Middle Ordovician trilobite biofacies, southern Mackenzie Mountains; p. 1-38: 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.

Ludvigsen, R., 1979. A trilobite zonation of Middle Ordovician rocks, southwestern District of Mackenzie; Geological Survey of Canada, Bulletin 312.

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.

Source: CSPG Lexicon of Canadian Stratigraphy, Volume 2, Yukon Territory and District of Mackenzie; L.V. Hills, E.V. Sangster and L.B. Suneby (editor)
Contributor: R. Ludvigsen; L.V. Hills
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 07 Dec 2010