Type Locality:

Quarry at Stony Mountain, Manitoba, in 14-13-2EPM. Suggested reference core hole is Manitoba Core Hole M-3-74, Headingly North (1-21-11-1EPM), between 19.5 and 54.9 m (64 and 180 ft).

Distribution:

The Stony Mountain Formation extends throughout the Williston Basin, but the shaly Gunn Member is limited to the more central region to the south and east. The unit thins to the north along the outcrop belt, from about 45 m (148 ft) near the border with the United States to 30 m (98 ft) at the northern erosional limit. A comparable, though more irregular thinning occurs to the north and west in Saskatchewan.

Lithology:

The Stony Mountain Formation shows pronounced lateral facies changes along the outcrop belt. To the south, towards the centre of the Williston Basin the lower part of the formation consists of Gunn-type lithology; i.e. a sequence of interbedded, red to grey calcareous shales and highly fossiliferous limestones. These are overlain by thin, red to yellowish grey, argillaceous, fossiliferous dolomites of the Penitentiary Member. To the north the Stony Mountain changes rapidly to argillaceous dolomite, so that the entire lower Stony Mountain acquires a Penitentiary-type lithology. Still farther north the shale content decreases progressively to the point where the lower Stony Mountain beds are virtually indistinguishable from the overlying Gunton dolomites. The Gunton Member maintains a relatively uniform lithology, consisting of pale yellowish brown, faintly mottled, very finely crystalline, dense, sparsely fossiliferous dolomite, show thin nodular bedding. In the central portion of the Williston Basin Kendall (1976) noted the presence of a thin evaporite (the Gunton anhydrite) at the top of the formation.

Relationship:

In the type area the Stony Mountain Formation overlies the Fort Garry Member of the Red River Formation sharply, and possibly with slight disconformity. It is overlain, also with possible slight disconformity by the sandy, argillaceous (non-sequential) marker beds of the Stonewall Formation.

History:

Dowling's Stony Mountain was subdivided by Okulitch (1943) into four members, in ascending sequence the Stony Mountain Shale, Penitentiary, Gunton and Birse. Sinclair and Leith (1952) renamed the lower shaly unit the Gunn Member to conform to the Stratigraphic Code. Baillie (1952) indicated that the Birse Member was indistinguishable from the Gunton Member and assigned all Birse strata to the Gunton Member. In 1952 Baillie proposed that the 6 m (20 ft) sequence of red, argillaceous and arenaceous dolomites immediately above the Gunton dolomite be part of the Stony Mountain Formation, rather than the Stonewall. These beds were named the Williams Member (Smith, 1963a), but general usage has retained the argillaceous marker beds as part of the Stonewall Formation (Kendall, 1976). In the subsurface the Gunn and Penitentiary members cannot be differentiated. The Saskatchewan Geological Society (1958) subdivided the Stony Mountain into Stoughton and Gunton "Beds", which Kent (1960) formalized as members. Kendall (1976) revised the Stony Mountain Formation to include the Hartaven, Gunn and Gunton members.

Other Citations:

Baillie, 1951, 1952; Dowling, 1900; Kendall, 1976; Kent, 1960; McCabe 1971; Okulitch, 1943; Porter and Fuller, 1958, 1959; Saskatchewan Geological Society, 1958; Sinclair and Leith, 1958; Smith, 1964a, 1964b.

References:

Baillie, A.D., 1952. Ordovician geology of Lake Winnipeg and adjacent areas, Manitoba; Manitoba Department of Mines and Natural Resources, Mines Branch, Bulletin 51-6, 64 p. + 2 Maps.

Dowling, D.B., 1900. Report on the Geology of the West Shore and Islands of Lake Winnipeg; Geological Survey of Canada, Annual Report 1898, Volume XI, Part F, with Map 664.

Kendall, A.C., 1976. The Ordovician carbonate succession (Bighorn Group) ot southern Saskatchewan. Saskatchewan Dept. Min. Res., Rept. 180.

Kent, D.M., 1960. The evaporites of the Upper Ordovician strata in the northern part of the Williston Basin, Saskatchewan Department of Mineral Resources (SDMR), Saskatchewan Industry and Resources (SIR) Report no. 46, 45 p., 2 tables, 5 plates, 7 figures. 3 cross sections, 1 panel diagram, in pocket.

Okulitch, V.J., 1943. The Stony Mountain Fornnation of Manitoba. Transactions of the Royal Society of Canada, v. 37, Ser. 3, s. 4, p. 59-74.

Saskatchewan Geological Society, 1958. Report of the Lower Paleozoic Names and Correlation Committee, Regina.

Sinclair, George Winston and Leith, Edward Isaac, 1958. New name for an Ordovician shale in Manitoba; Journal of Paleontology, vol. 32, no. 1 (January), pp. 243-244.

Smith, Donald Leigh, 1963a. A lithologic study of the Stony Mountain Formation and Stonewall formations in southern Manitoba; University of Manitoba, Winnipeg, MB, M.Sc. thesis, 219 p.