Distribution:

Most of the Lorrain is resistant to erosion, forms ridges and hills, and is fairly well exposed (Frarey, 1977).

Lithology:

The Lorrain Formation (Miller and Knight, 1906) is a very thick, distinctive assemblage of sandstones mainly, but it includes minor argillite, siltstone, and oligomictic pebble conglomerate. The Lorrain is treated in Frarey according to the following six stratigraphic subdivisions, comprising five lithologies. All contacts are conformable and gradational. White quartzite member: orthoquartzite, pebble conglomerate, minor feldspathic quartzite. Upper red quartzite member: cross-bedded pebbly pink, red, buff, and white quartzite. Jasper conglomerate member: white orthoquartzite and pebble conglomerate. Lower red quartzite member: cross-bedded pebbly and conglomerate pink, red, and white quartzite. Purple siltstone member (local to Desbarats area only): purple and maroon siltstone, argillite. Basal arkose member: buff and pink arkose; feldspathic quartzite; basal siltstone, argillite, and greywacke. (Frarey, 1977).

Relationship:

The complete stratigraphic sequence of the Cobalt Group (Huronian Supergroup), which is as follows in order downward, is the: Bar River Formation, Gordon Lake Formation, Lorrain Formation, and Gowganda Formation. The Lorrain conformably overlies the upper argillite member of the Gowganda Formation (Frarey, 1977). The Gordon Lake succeeds the Lorrain Formation conformably through a thin interbedded zone (Frarey, 1967b).

History:

Originally, Murray (1859, p. 77) employed three separate stratigraphic units - a lower red quartzite, a middle jasper conglomerate, and an upper white quartzite - equal in rank to his other formations to embrace what later became Collin's Lorrain Formation in this area. Collins (1925, pp. 67, 68) rejected Murrary's threefold separation on the grounds that it was local to the Bruce Mines area and that the three 'formations' were gradational and represented a continuing period of deposition. Although Collins' observations are factual, Frarey nevertheless found his Lorrain to be readily and consistently subdivisible (Frarey, 1962), providing useful reference for descriptive and interpretative purposes, and also found that in places subdivision is useful in determining structural conditions. The Lorrain, then, is treated in Frarey (1977) (Frarey, 1977).

References:

Collins, W.H., 1925. North Shore of Lake Huron; Geological Survey of Canada Memoir 143, 160 p.

Frarey, M.J., 1962. Bruce Mines, Ontario; Geological Survey of Canada, Map 32-1962.

Frarey, M.J., 1967b. Three New Huronian Formational Names; Geological Survey of Canada, Paper 67-06, 3 p.

Frarey, M.J., 1977. Geology of the Huronian Belt between Sault Ste. Marie and Blind River, Ontario; Geological Survey of Canada, Memoir 383, 87 p.

Miller, W.G. and Knight, C.W., 1906. Map of the cobalt-nickel-arsenic-silver area near Lake Temiskaming, Ontario, 2nd ed.; in Cobalt-nickel arsenides and silver deposits of Temiskaming, Ontario; Ontario Bureau of Mines, 14 Annual Report, p. II, pp. 1-51.

Murray, A., 1859. On the country between the Thessalon River and Lake Huron and between the Thessalon and the Mississagi; Geological Survey of Canada, Report of Progress for the Year 1858, pp. 67-100.