Yellowish orange sandstone, sandy and silty carbonaceous shale, and coal. Alluvial plain. Thickness as much as 300 m (984 ft).
Light gray, bentonitic claystone that alternates with gray to brown sandstone interbedded with carbonaceous shale. Laterally equivalent to Lance Formation. Fluvial and flood plain. Thickness as much as 335 m (1,100 ft).
Yellow sandstone interbedded with subordinate grayish brown and black shale and thin beds of coal. Alluvial plain. Thickness as much as 180 m (590 ft).
Gravel, sand, silt, and clay deposits of stream and river channels, and floodplains.
Dark gray carbonaceous shale, bentonitic claystone, sandstone, and coal. Alluvial plain. Thickness as much as 185 m (607 ft).
Southeastern Montana: orangish brown, arkosic sandstone, lenticular conglomerate and siltstone, dark gray carbonaceous shale, coal, and varicolored claystone. Bears Paw Mountains: variegated red, pink, lavender, light green, yellow, gray, and very light gray shale, bentonitic claystone, and siltstone; light gray, brown, and green cross-bedded sandstone; and lenses of boulder conglomerate. Syntectonic alluvial fan and alluvial plain. Thickness as much as 120 m (394 ft) in Montana; upper part removed by erosion.
Variable deposits that range from pebble to boulder size and include sand, silt, and clay. Dominantly alluvial terrace, abandoned channel and floodplain, remnant alluvial fan, and local glacial outwash.
Yellowish orange to gray, fine- to medium grained, noncalcareous, hummocky-bedded sandstone. Thickness 15–22 m (50–72 ft).
Yellowish orange, wavy-bedded siltstone and black shale with calcareous concretion zone. Thickness 10 m (33 ft).
Soft gray sandstone, gray and brown carbonaceous shale, and thin coal beds.
Variable deposits that range from pebble to boulder size and include sand, silt, and clay. Dominantly alluvial terrace, abandoned channel and floodplain, remnant alluvial fan, and local glacial outwash.
(North Wyoming) - Thick-bedded buff sandstone and drab to green shale; thin conglomerate lenses. (South and Northeast Wyoming) - Brown and gray sandstone and shale; thin coal and carbonaceous shale beds.