Abstract

An outlier of sedimentary rock assigned to the Gowganda Formation of the Huronian Supergroup was discovered during field mapping in the Goulais River area, District of Algoma, Ontario. This outlier is the northernmost documented occurrence of Huronian sedimentary rocks in the Algoma region. The outlier is 53 m in stratigraphic thickness and consists of polymictic to oligomictic paraconglomerate and orthoconglomerate with interbeds of pink arkose, siltstone, and dark grey greywacke. The conglomerates contain metavolcanic fragments and altered feldspars that suggest part of the sediment had a nearby source. Hematite results in a pink matrix in both conglomerates and arkosic interbeds and may indicate that an oxidizing environment prevailed during deposition. Air photo interpretation may help locate other outliers in the vicinity of lineaments, faults, or topographic highs.

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