Moosebar–Gates sandstones are predominantly litharenites, with some feldspathic litharenites. Both the light- and heavy-mineral suites indicate a mixed source characterized by clastic and carbonate sedimentary rocks, acidic to intermediate plutonic and volcanic igneous rocks, and metamorphic rocks. The sediment sources all fall within a recycled orogenic provenance grouping. Histograms showing stratigraphic variation of mineral content do not indicate any significant progressive unroofing of more deeply buried source rocks.The source area was very extensive regionally and extended well into the Omineca Crystalline Belt and eastern margins of the Intermontane Belt. Zebraic chalcedony was derived from evaporitic rocks of the Charlie Lake Formation, situated east of the Rocky Mountain Trench. Kyanite and almandine garnet were probably derived from the Omineca Crystalline Belt west of the Rocky Mountain Trench. Regional paleoslope dipped towards the north-northwest. Restoration of strike-slip on the Rocky Mountain Trench places potential source areas to the south of the depocentre; this supports paleoslope data. During Moosebar–Gates time the Tenakihi Group in the Omineca Crystalline Belt would have been hundreds of kilometres south of its present location and south of the study area, where it could have provided sediment. Volcanic rocks were derived from west of the Rocky Mountain Trench. Source rocks in the Omineca Crystalline Belt were being eroded as early as late early Albian and providing sediment into the foreland basin to the east.

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