69. Omars (1940s)


In 1873 in northern Ontario, Geological Survey of Canada geologist Robert Bell discovered distinctive grey rocks with rounded and elongated weathering pits. He interpreted them to have been glacially transported from the northeast. Rocks transported by glaciers away from their region of origin are called erratics. Bell’s erratics were later tracked to the Omarolluk Formation on the Belcher Islands in eastern Hudson Bay, and were named omars after their source location.

In the 1940s, Survey geologist Victor Prest recognized that the unique place of origin of omars made them an important marker for reconstructing past glacier movements. Since then, omars have been identified in the Prairies, western Quebec, Ontario, and in several northern U.S. states. They are a testimony to at least two phases of glaciation and glacial transport over thousands of kilometres by the Laurentide Ice Sheet, which had covered all of eastern and northern Canada during the last glaciation about 21,000 years ago.

This omar specimen was found in southern Saskatchewan by Survey geologist Stephen Wolfe and represents 1800 kilometers of glacial transport. It was identified and autographed by Prest.

Category: Rocks, Fossils, Minerals and Meteorites

Decade: 1940s


Prest, V.K., Donaldson, J.A., and Mooers, H.D., 2000. The omar story: the role of omars in assessing glacial history of west-central North America; Géographie physique et Quaternaire, v. 54, p. 257–270. doi:10.7202/005654ar

GSC 175 - CGC 175