ABSTRACT

The stratigraphic nomenclature of Canadian (Lower Ordovician) strata of the southern Rocky Mountains of Alberta is revised. The terms Mons Formation, Sarbach Formation, Robson Limestones, Goodsir Group, and Sarceen Series are discarded. Two new formations are proposed: the Survey Peak Formation and the overlying Outram Formation. The type sections of both formations are at Mount Wilson, which can be considered the standard section for the Ordovician rocks of Alberta.

The Survey Peak Formation consists of calcareous shales and mudstones, siltstones, microcrystalline limestones, calcisiltites, limestone-pebble conglomerates, biocalcarenites, and cryptalgal limestones. Four informal members, basal silty, putty shale, middle, and upper massive, can be distinguished. All of these apparently originated on a shallow to very shallow, intermittently emergent sea bottom. The Survey Peak rests with abrupt but concordant contact upon the uppermost Cambrian Mistaya Formation or its equivalent in the Lynx Group. The formation can be recognized in the upper part of the McKay Group of adjacent British Columbia.

The Outram Formation includes dark-coloured shales, calcareous siltstones, calcisiltites, clotted, nodular, and laminated limestones, biocalcarenites, and limestone-pebble conglomerates. Chert is present as nodules, tracery, and irregular masses. Origin in moderately shallow, poorly aerated marine waters is suggested. The Outram has conformable and gradational contacts with the Survey Peak Formation below and the Skoki Formation above. The formation is coeval with the lowest part of the Glenogle Shales of southeastern British Columbia.

The Survey Peak, Outram and basal Skoki appear to represent a complete sequence through Canadian time. The trilobite zonation of the Survey Peak and Outram is remarkably similar to the zonation established in Utah and Nevada. The uppermost Cambrian Saukia Zone and Canadian Zones A, B, D, E, F, and G₁ can be recognized in the Survey Peak Formation, and Zones G₁, G₂, and J in the Outram Formation. Zones C, H, and I have not yet been detected in the southern Rocky Mountains.