Type Locality:

The type section is part of Section 11 of Morrow and Cook; the base of the type section is at 61°33'N latitude and 124°47'W longitude (Morrow and Cook, 1987).

Distribution:

The Cadillac Formation is widespread throughout the Virginia Falls map area in the southern Mackenzie Mountains, Northwest Territories. The orange siltstone and pink shale members occur throughout Root Basin and the Prairie Creek Embayment, but the megabreccia member appears to be confined to a relatively narrow belt adjacent to, and parallel with, the shelf edge of the Root River Formation. The combined thickness of the orange siltstone member and the coeval megabreccia member is greatest on the east side of the embayment. A maximum thickness of 840 m at the type section decreases westward and northward to less than 200 m on the west side of the embayment. The overlying pink shale member is commonly between 100 and 200 m thick throughout most of the embayment (Morrow and Cook, 1987).

Lithology:

The Cadillac Formation is a sequence dominated by slightly to very recessive bright orange- to brown- weathering, thin bedded, dolomitic siltstones and sandstones with scattered limestone beds in its lower part and by pink dolomitic siltstone and shale in its upper part (Morrow and Cook, 1987).

Fossils:

Monograptid graptolites, conodonts, and trilobites (Morrow and Cook, 1987).

Relationship:

The Cadillac Formation is readily divisible into three distinct lithofacies or members: an orange siltstone member, a megabreccia member, and a pink shale member. The orange siltstone member and the laterally equivalent megabreccia member form the lower part of the Cadillac Formation, the pink shale member the upper part. It overlies the Road River Formation with a conformable, gradational contact. The basinal member of the Arnica Formation overlies the Cadillac Formation with an abrupt but conformable contact. Within the Cadillac Formation the Late Silurian to early Early Devonian orange siltstone and megabreccia members pass laterally westward into the Road River Vera and Camsell formations and part of the Sombre Formation. The bulk of the orange silstone and the megabreccia members may pass eastward into a relatively thin sequence at the top of the Root River Formation and possibly some basal Camsell beds. The middle Early to late Early Devonian pink shale member, overlying the orange siltstone member appears to be coeval with the Sombre Formation around the embayment. The detriatal member of the Sombre Formation forms a narrow facies belt that separates the shelf Sombre from the pink shale member of the Cadillac Formation in the central part of the embayment. The Cadillac Formation has been included within the Prairie Creek Assemblage. The Prairie Creek Assemblage has been divided into two phases; the Lower Cadillac phase and the Upper Cadillac phase. The Lower Cadillac phase is composed of the orange siltstone and megabreccia members of the Cadillac Formation within Root Basin, and later within the Prairie Creek Embayment. The Vera Formation and the Corridor Member of the Camsell Formation were deposited outside the embayment. The Upper Cadillac phase is represented by the pink shale member that forms the upper part of the Cadillac Formation, the basinal member of the Arnica Formation, the detrital member of the Sombre Formation within the embayment area, and the Sombre and Arnica formations outside the embayment (Morrow and Cook, 1987).

History:

The formation is named after Cadillac Creek, a tributary of Prairie Creek immediately south of the type section (Morrow and Cook, 1987).

References:

Morrow, D.W. and Cook, D.G., 1987. The Prairie Creek embayment and lower Paleozoic strata of the southern Mackenzie Mountains; Geological Survey of Canada, Memoir 412, 195 p.

Morrow, D.W., 1984. Sedimentation in Root Basin and Prairie Creek Embayment - Siluro-Devonian, Northwewst Territories. Bulletin of Canadian Petroleum Geology, volume 32, number 2, pages 162-189.