ABSTRACT

The Ice River complex, in Yoho and Kootenay National Parks, consists of plutonic basement rocks of Precambrian age (Gussow and Hunt, 1959), brought to the surface in two thrust sheets as a result of the Rocky Mountain orogeny. The basement rocks consist of nepheline and sodalite syenite, paragneisses, and crystalline limestones, which unconformably underlie rocks of Upper Cambrian age. The strata immediately overlying the basement are dove-gray limestones containing boulders and pebbles of basement rocks, and locally have a thin basal conglomerate or grit. The limestones thin by onlap on basement topography (, ). In recent years, other workers have postulated carbonatites, magmatic differentiation, and liquid immiscibility for their origin (Gussow, 1977).²

The Ice River controversy is dealt with in detail, by documenting the evidence for the true age of the complex, and reinterpreting the data of others in the light of this evidence.