Unit Name: Horsefeed Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Late Mississippian - Late Permian (328.3 - 251 ma)
Age Justification: Biostratigraphy. The dominantly carbonate Horsefeed Formation contains fossils of late Mississippian, mid- and late Pennsylvanian, and Early and Late Permian ages (Monger, 1975) (Gabrielse, 1998).
Province/Territory: British Columbia; Yukon Territory
Originator: Monger, 1975.
Type Locality:
The type area of the Horsefeed Formation is the Nakina Lake area (Monger, 1975).
Distribution:
Occurs in the southwestern facies belt of the Atlin Terrane. Outcrops near Nakina Lake, Sentinel Mountain, Tagish Lake and Mount White (Monger, 1975). In its type area the Horsefeed Formation is at least 1500 m thick but in the western part of the Dease Lake map area it may be considerably thinner because of bounding faults (Gabrielse, 1998).
Lithology:
In its type area to the northwest in the Atlin map area the lower part of the formation consists of a basal, massive, pale grey-weathering calc-arenite overlain by a thick succession of pale grey, porcellanous, crinoidal, and foraminiferal calc-arenite. This member grades upwards into dark grey, very fine grained detrital limestone and dolomitic limestone. The uppermost member of the Horsefeed Formation is an aggregate of foraminiferal cal-arenite and, in the lower part, locally breccia. Between Koshin and Nahlin rivers the most common lithology is pale grey, unsorted, massive limestone breccia (Monger, 1975) (Gabrielse, 1998).
Relationship:
The Horsefeed Formation regionally overlies Upper Mississippian tuff, argillite, and chert containing limestone pods. These rocks are included in the Kedahda Formation as are lithologies that overlie the Horsefeed Formation consisting of basal limestone breccia overlain by siltstone, argillite, and chert. The contact at the base of the upper Kedahda Formation is considered to be a regional unconformity (Monger, 1975) (Gabrielse, 1998). The Horsefeed Formation is equivalent, at least in part, to Daly's (1915) "member 1" east of Kamloops. Monger and Ross (1971) and Ross (in Monger, 1975) have suggested a correlation with the Marble Canyon Formation in southern British Columbia (Nassichuk, 1977).
History:
Named from Horsefeed Creek, which heads in the valley 9 miles west-northwest of the southwest end of Nakina Lake (Monger, 1975).
References:
Daly, R.A. 1915. A geological reconnaissance between Golden and Kamloops, B.C., along the Canadian Pacific Railway; Geological Survey of Canada Memoir 68, 260 pages.
Gabrielse, H., 1998. Geology of Cry Lake and Dease Lake map areas, north-central British Columbia; Geological Survey of Canada, Bulletin 504, 147 p.
Monger, J.W.H. and Ross, C.A., 1971. Distribution of fusulinaceans in the western Canadian Cordillera; Canadian Journal of Earth Sciences, v. 8, p. 259-278.
Monger, J.W.H., 1975. Upper Paleozoic rocks of the Atlin Terrane, northwestern British Columbia and south-central Yukon; Geological Survey of Canada, Paper 74-47, 63 p.
Nassichuk, W.W., 1977. Upper Permian Ammonoids from the Cache Creek Group in Western Canada; Journal of Paleontology, Vol. 51, No. 3 (May, 1977), pp. 557-590.
Source: GSC file of geological names; T.E. Bolton and J. Dougherty (compiler)
Contributor: Michael Pashulka
Entry Reviewed: No
Name Set: Lithostratigraphic Lexicon
LastChange: 30 Dec 2010