ABSTRACT

The Belloy Formation (Wolfcampian to Guadalupian age) consists of sandy or silty dolomites, quartzose sandstones, phosphorites, cherts and minor dolomites. The formation thickens towards the southwest, from an erosional edge to over 600 ft west of Fort St. John. The thickening represents original deposition somewhat modified by post-Permian erosion, and coincides with increased argillaceous content. A major period of erosion separated the Upper Carboniferous from the Permian, and rocks of Permian age rest disconformably on those of Osagean to Atokan age.

Rocks of the Belloy Formation are in part very similar lithologically to those of the underlying Stoddart Group, and only through combined consideration of several parameters (mineralogy, textures, diagenetic features, chemistry, fauna and microflora) can a division be established. Within the Belloy it has not been possible to recognize consistently mappable members, although individual sections contain some distinctive units. The occurrence of many thin, intraformational phosphatic chert-conglomerates, and frequent facies changes, suggest many transgressive and regressive sedimentation phases during the Permian time.

Rocks of the Belloy Formation are also petrographically similar to those of the Permian Ishbel Group, which has been shown (McGugan et al., 1968) to have been deposited in a similar environment to that of the Phosphoria Formation. The petrographic features suggest that diagenesis and lithification took place within a very chemically active environment. The mineral groups present are indicative of a phosphate-producing environment, and an evaporite-producing environment, precipitating a carbonate-sulphate-silica sequence. The Belloy Formation can be correlated with the Mount Greene beds to the west and the Ishbel Group to the south of the study area, but equivalents of the Ranger Canyon and Mowitch formations of the Ishbel Group appear to be missing.