Type Locality:

Exposures along banks of Cataract Creek, 0.4 km (0.25 mi) above junction with Highwood River, Highwood Range, Alberta at 50 deg 23.7'N, 114 deg 35'W.

Distribution:

The Etherington Formation consists of a lithologically and environmentally complex sedimentary wedge that thickens westward from a zero edge in the subsurface of the foothills to at least 210 m (689 ft) in westernmost exposures. In the type section of combined eastern and upper facies it is 58 m (190 ft) thick, and elsewhere in the easternmost exposures the two together (Daisy Creek and Ewin Creek Members) range from 60 to 90.8 m (197 to 298 ft). The Ewin Creek Member reaches a maximum of 84 m (276 ft) in thickness, and the Cyclamen Member 68 to 147.5 m (223 to 484 ft) below the Ewin Creek. Where the Ewin Creek Member is missing the Cyclamen reaches at least 201 m (660 ft), and farther west probably considerably more. In the adjacent subsurface the formation is missing due to a combination of differential sedimentation and post-depositional erosion during pre-middle Pennsylvanian and later intervals. The eastern dolomite-shale and upper dolomites and stone facies are exposed in the Livingstone Range, Highwood Range and eastern front ranges north of Kananaskis River. The western limestone facies is exposed in the mountains west of the surface trace of the Lewis Thrust, Misty Fault and Rundle Fault and continues to the westernmost exposures of the Mississippian.

Lithology:

At the type locality the Etherington includes a variety of rock types of which sandy, cryptocrystalline to medium-crystalline dolomite predominates, but also contains sandy limestone and green shale. These alternate in a recurring pattern that permit the recognition of cycles. In the lower part of the formation green shale is abundant with interbedded dolomite; the middle part consists of sandy and cherty limestone and dolomite; the upper part is sandy dolomite. In a detailed regional study of the Etherington Formation Scott (1964a, b, brief summary only) recognized three distinct lithofacies; an eastern, western and upper: The eastern dolomite-shale facies, represented by the lower and middle parts of Douglas' type section includes dolomite, limestone, sandstone, siltstone, shale, locally solution collapse breccia and thin intraformational breccia-conglomerate. Colors range from grey to greenish grey to maroon; shales are green to maroon. Shale is abundant in the lower part, where beds 6 to 10 m (20 to 30 ft) thick occur. To this facies the name Daisy Creek Member was informally given. The western limestone facies is composed predominantly of skeletal limestone (echinoderm-bryozoan calcarenite), but oolite and pseudo-oolite are very abundant in some sections. Thin beds of very fine-grained quartz sandstone are common. Fragments of calcareous algae, brachiopods and forams are subordinate rock-forming components. To this facies Scott informally applied the name Cyclamen Member. The upper part of the Etherington almost everywhere consists of grey, microcrystalline, highly sandy and cherty dolomite with some sandstone interbeds comprising the dolomites and stone lithofacies, to which the name Ewin Creek Member was informally given. It constitutes the entire formation at Lantern Creek in the Highwood Range and grades laterally in the upper part of each of the other two facies, forming an upper member over a broad area. The eastern dolomite-shale and upper dolomite-sandstone facies are lagoonal; the western limestone facies open marine shelf. Oolite, calcarenite and quartz sandstone barriers probably separated the restricted and open marine environments.

Relationship:

The Etherington Formation everywhere overlies the Mount Head Formation with sharp contact that appears to represent a brief hiatus. In easternmost exposures there is evidence of erosion at the contact. The upper contact in easternmost exposures is an unconformity, above which lies sandstones of the Tobermory Formation, Rocky Mountain Supergroup. West of the Livingstone and Highwood Ranges the Etherington is conformably overlain by the Todhunter Formation (Norris, 1965 re-defined the Todhunter as a member of the Etherington Formation).

History:

Norris (1965) re-defined the Etherington Formation in the front ranges to include, at the top the Todhunter Member, stating that the top rather than the base of the Todhunter is more easily recognized on a regional scale. He also dated the Todhunter as Mississippian (Chesteran), the same as the Etherington, although according to Scott (1964a, b) Todhunter fossils were identified by Bamber as Pennsylvanian. In the following description the Todhunter is not included in the Etherington.

Other Citations:

Douglas, 1958; Mamet, 1968; Norris, 1965; Scott, 1964a, 1964b.

References:

Douglas, R.J.W., 1958a. Mount Head map-area, Alberta (with Map 1052A); Geological Survey of Canada, Memoir 291, 241 p.