Abstract

The Belcher Fold Belt west of the Nastapoka homocline comprises an ensialic domain with an external zone and an internal zone, and an oceanic domain. The gentle folds of the central portion of the external zone pass into the zone of imbricate structure northward and, possibly, southward. The internal zone is characterized by an imbricate structure which has affected the basement. The oceanic domain is subdivided into several belts. Tectonic transport was generally eastward, but locally some parts of the oceanic domain were thrust westward. The Proterozoic sequence of the Winisk structural low, situated west of the Belcher Fold Belt, is only gently folded and rarely faulted.

It is suggested that the central and northern parts of Hudson Bay belong to the Archean Hudson Protocontinent. The continuation of the Belcher Fold Belt and that of the Winisk structural low are recognized south of the postulated Hudson Protocontinent.

The Hudson Bay Basin was a relatively simple, saucer shaped basin in its early stages of development. Later a northwest-trending central high came into being, probably as a result of reactivation of an important Precambrian fault zone. Originally manifested as a shoal and later as an island belt, the central high divided the Hudson Bay Basin into two sub-basins: an eastern sub-basin and a western sub-basin. General uplift of the study area and eustatic fall of sea level during Early Devonian time resulted in regression of the sea, and erosion. The subsequent transgression occurred first in the western sub-basin, probably in the Siegenian, while the eastern sub-basin, in all probability, was not covered by the sea before the beginning of the Eifelian. During Eifelian time a change of tectonic regime occurred, resulting in subsidence and disappearance of the central island belt and in the union of the two sub-basins.