Interval includes Verdigris and Swede Hollow formations; base of map unit drawn at the widespread Whitebreast Coal. Primary Lithologies: shale/mudstone, light to dark gray, part silty to sandy; siltstone, gray. Secondary Lithologies: limestone, part fossiliferous, part sandy; sandstone, very fine to fine-grained. Minor: mudstone, red/maroon to brown; shale, black, phosphatic; carbonaceous shale; coal (beds locally > 2 ft); ironstone/siderite concretions; limestone concretions (may be septarian); pyrite. Average thickness 100 ft (30 m); maximum thicknesses to 130 ft (40 m).