Unit Name: Tahkandit Formation
Unit Type: Lithostratigraphic
Usage: Currently in use
Age Interval: Leonardian (280 - 270.6 ma)
Age Justification: Fusulinids, brachiopods, corals.
Province/Territory: Yukon Territory; Alaska
Originator: Mertie, 1930; modified by Brabb and Grant, 1971.
Along the southwest bank of the Yukon River just above the mouth of the Nation River (old Indian name Tahkandit), east-central Alaska. The best section is seen along the south-west bank of the Yukon, where both the overlying and underlying rocks are exposed (Mertie, 1930, p. 122). This is interpreted to mean the type section by Brabb and Grant (1971) and occurs in the northwest corner of Sec. 17, T4, R30 E (65 deg 10.8'N, 141 deg 41.9'W).
At the type section it is about 100 m (330 ft) thick (Brabb and Grant, 1971). In the Yukon it is 409 m (1,341 ft) thick on the Tatonduk River, 258 m (846 ft) on the south side of Sheep Mountain becoming thinner to the southeast, and is not recognizable east of 139 deg 35'W (Mountjoy, 1967b). It also thins northward from the Tatonduk River with about 396 m (1,300 ft) near Mount Burgess reported by Nelson and Johnson (1968).
Thickness(m): Typical 100.
It consists of cream coloured to white, fossiliferous limestone at the top and lower interval consisting of conglomerate alternating with green and brown shales, massive cream coloured limestones, and sandstone. Grey and green chert pebbles form the clasts within the conglomerate. Brabb and Grant (1971) reinterpreted it to consist of a lower 23 m (75 ft) calcareous sandstone, chert pebble conglomerate and sandy limestone and an upper 78 m (255 ft) of massive skeletal limestone. Similar lithologic subdivision can be recognized in the Yukon except that it is thicker and conglomerates are not as common.
At the type section in Alaska it lies unconformably on the Devonian Nation River and is overlain by the Glen Shale. In the Yukon it conformably and gradationally overlies the Jungle Creek Fm and is overlain unconformably by strata of Triassic and Cretaceous age (Monster Fm). Brabb and Churkin (1969) state that it unconformably overlies the Calico Bluff Fm in east-central Alaska.
Bamber, 1972; Bamber and Waterhouse, 1971; Brabb and Churkin, 1969; Brabb and Grant, 1971; Mertie, 1930; Mountjoy, 1967b; Nelson, 1961; Nelson and Johnson 1968; C.A. Ross, 1967.
Brabb, E.E., and Grant, R.E., 1971. Stratigraphy and paleontology of the revised type section for the Tahkandit Limestone (Permian) in east-central Alaska, United States Geological Survey (USGS), Professional Paper 703, 26 p.
Brabb, Earl E. and Churkin, Michael, Jr., 1969. Age of Nation River Formation, east-central Alaska (discussion of paper by L. R. Laudon, et al., 1966); The American Association of Petroleum Geologists (AAPG), AAPG Bulletin, vol. 53, no. 2 (February), pp. 430-433.
Mertie, J.B., Jr., 1930. Geology of the Eagle-Circle District, Alaska; United States Geological Survey (USGS), Bulletin 816, 168 p.
Mountjoy, E.W., 1967b. Triassic stratigraphy of northern Yukon Territory; Geological Survey of Canada, Paper 66-19, 44 p.
Nelson, Samuel J. and Johnson, Charlie E., 1968. Permo-Pennsylvanian brachythyrid and horridonid brachiopods from the Yukon Territory, Canada; The Paleontological Society, Journal of Paleontology, vol. 42, no. 3 (May), Part 1, pp. 715-746.
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: L.V. Hills; E.W. Bamber
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 20 Mar 2009