Norton Formation (Campbell, 1893). Siltstone, shale, sandstone, conglomerate, limestone, and coal. Siltstone and shale, light- to medium-gray, with siderite and claystone concretions, fossiliferous; interbedded with and grades into sandstone. Sandstone, feldspathic, micaceous, argillaceous, light- to medium-gray, very-fine- to coarse-grained, thin- to very-thick-bedded, cross-bedded, locally massive, well-cemented. Conglomerate in thin zones in McClure Sandstone Member (lateral equivalent to part of Bee Rock Sandstone Member of the Lee Formation). Lime stone, medium-gray, micrograined, locally in lenses in two zones above the McClure Sandstone Member (Taylor, 1989; Whitlock, 1989). Coal in several beds and zones. A volcanic ash parting is in the Upper Banner coal bed locally (Diffenbach, 1988, 1989; Evans and Troensegaard, 1991; Henika, 1989a). The base of the Norton is defined as the top of the uppermost quartzarenite of the Lee Formation. On the western side of the coalfield the base of the Norton is at the top of the Bee Rock Sandstone Member of the underlying Lee Formation. However, the Bee Rock grades eastward into feldspathic, conglomeratic sandstone of the McClure Sandstone Member of the Norton. Several underlying Lee quartzarenites successively tongue out or grade into finer-grained clastic rocks to the southeast stratigraphically lowering the base of the Norton. This accounts for the great range in thickness of 500 to 2480 feet for the Norton Formation.