Unit Name: Melita Formation
Unit Type: Lithostratigraphic
Usage: Currently in use
Age Interval: Bajocian - Callovian ? (171.6 - 161.2 ma)
Originator: Stott, D.F., 1955.
No type section defined. Thickest section described by Stott is in California Standard West Daly Prov. 8-29-10-28WPM, in Manitoba, between 533.4 and 677.3 m (1,750 and 2,222 ft). Suggested reference section is in Tudale Neepawa 5-29-14-14WPM, between 454.7 and 649.5 m (1,492 and 2,131 ft), completely cored.
The Melita is primarily a subsurface unit in southwestern Manitoba. Sparse outcrop is now known to occur southeast of the town of St. Rose du Lac (22-23-15WPM) (Bannatyne, 1970). The name is not widely used. The maximum thickness of the unit is 143.3 m (470 ft). It thins to the north and east due to both depositional thinning and pre-Cretaceous erosional thinning north of the area of Upper Jurassic cover. North of Virden thinning also occurs at the base of the unit because of overstep onto a Paleozoic paleotopographic high. Northward thinning is accompanied by a marked increase in sand/silt content, especially in the lower part of the formation. North of approximately Twp. 20 differentiation of Melita sands from the overlying Cretaceous Swan River sands is difficult.
The Melita is subdivided into two units. The lower Melita consists of varicolored shales and thin interbeds of sandstone. Sandstone is more common towards the base of the unit, and the sand content increases to the north. Marked lithologic changes occur both laterally and vertically. The upper Melita consists of darker greenish to brownish grey, slightly calcareous and silty shales with interbeds of light grey, variably fossiliferous, dense, in part sandy limestone in the upper part of the sequence. Minor thin interbeds of fine-grained, calcareous or kaolinitic quartzose sand are noted.
The Melita is underlain with slight disconformity by oolitic and argillaceous limestones of the Reston Formation. North of approximately Twp. 20 Melita beds overstep the Reston to rest unconformably on Paleozoic (Mississippian and Upper Devonian) strata. South of approximately Twp. 12 the Melita is overlain conformably by sandy calcareous beds of the Waskada Formation, but north of this it is overlain unconformably by either the sands of the Swan River Formation or the grey shales of the Ashville Formation. It is equivalent to the upper Gravelbourg plus the Shaunavon, plus the lower and part of the middle Vanguard of Saskatchewan, and with the Piper plus the Rierdon of North Dakota.
Bannatyne, 1970; Stott, 1968.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: H .R. McCabe
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 29 Apr 2003