Coarse gravels of the Miocene Wood Mountain Formation that cap the Wood Mountain upland in southern Saskatchewan are an erosional remant of a much more expansive sheet of gravel and sand. The formation consists of gravel and sand deposited as a thin sheet on a regional planation surface that extends approximately along strike for at least 160 km. This sheet, with a maximum thickness of 31 m, is the deposit of low-sinuosity, braided-river channels that flowed to the north-northeast. The Wood Mountain Formation represents an initial episode of erosion followed by low-accommodation deposition, where the net aggradation rate was likely low. The sediments of the Wood Mountain Formation are associated with change in tectonic style in western North America from one of compression to one of extension. The gravels were deposited above a regional erosion surface associated with isostatic uplift of the central Montana Uplift.