Bulletin 023

Bulletin 023

BUL 023

Precambrian Geology of the Jasper Region, Alberta

Author(s) Charlesworth, H.A. Date 1967-01-01

The Precambrian Miette Group of the Jasper region conformably underlies the Lower Cambrian Gog Group. In ascending order, the group consists of conglomerates, sandstones, siltstones and slates (Meadow Creek Formation) of which only 130 feet are exposed, some 1000 feet of slates, siltstones, limestone breccias and limestones (Old Fort Point Formation), and about 4000 feet of conglomerates, sandstones, siltstones, and slates (Wynd Formation). Two thousand conglomerates and sandstones Jasper Formation) and 900 feet of quartzites (unit A) make up the lower part of the Gog Group. All these rocks were derived from a dominantly metamorphic and igneous source, which lay to the northeast, and were deposited under deltaic conditions or in shallow seas.

During the Rocky Mountain orogeny, Miette strata were tightly folded and faulted. The folds, which are associated with various types of axial-plane cleavage, appear to die out in the upper part of the Wynd Formation, because those in the Gog Group are generally much more open and widely spaced. The bulk of the Miette Group belongs to the quartz-albite-chlorite-muscovite subfacies of the greenschist metamorphic facies. The major metamorphic reactions were the conversion of illite to muscovite, chlorite, and quartz, and the breakdown of potassic and calcic feldspars into albite. The upper part of the Miette Group and the whole of the Gog Group show fewer metamorphic effects. Quartz-calcite-chlorite veins are common in the Miette Group. Radiometric potassium-argon ages range between 1770 and 69 million years and are intermediate between the age of the source rocks and the age of orogenesis.

Charlesworth, H.A. (1967): Precambrian geology of the Jasper region, Alberta; Research Council of Alberta, RCA/AGS Bulletin 23, 83 p.