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predominantly gray to buff, fine- to medium -grained sandstone. It is generally friable and forms rounded cliffs where exposed. The Entrada is a potential aquifer, but, because it is generally too deep and is overlain by more productive water -bearing formations, it is not a common water exploration target. The Morrison is composed of marl, siltstone, clay and shale with some interbedded sandstone, limestone and conglomerate. The maroon, red, gray and green variegated shales are distinct in outcrop, but can be confused with the underlying Dockum red beds in drill cuttings. The Morrison is reported to range from 0 to 325 feet in thickness. In southeastern Colorado and southwestern Kansas, the Morrison-Dockum is considered an aquifer, and is elsewhere a part of the Permian -Pennsylvanian aquitard (Macfarlane). For purposes of this report, the Morrison is considered a leaky barrier which separates the Cheyenne and Dockum in the north and west parts of the District, and wedges out to the southeast, thus not being a very extensive aquitard. 6.2.5 Cheyenne Sandstone The Cheyenne Sandstone was previously considered to be the lower member of the Purgatorie, with the Kiowa Shale being the top member. The Cheyenne, Kiowa and Dakota are each clastic, lower Cretaceous formations comprised of interbedded gray sandstone, siltstone and shale. The Cheyenne and Dakota are predominately sandstone and the Kiowa predominately shale; distinction of these units in drill cuttings can be difficult. As described below, the heterogeneity of the Kiowa suggests that it is largely a leaky interval between the water -bearing Dakota and Cheyenne units. The Kiowa was an adequate seal to create artesian conditions in the Cheyenne in an area north of Walsh. The Cheyenne has been an important aquifer in the District. The Cheyenne Sandstone is a fine- to coarse-grained, light gray to buff sandstone. It is generally friable, contains lenses of conglomerate and ranges from 0 to 250 feet in thickness. The Cheyenne forms cliffs and steep valleys in the southwest part of the Basin and pinches out in the southeast corner of Baca County. The Cheyenne is generally described only as "sandstone", but an average of 10 detailed driller's logs indicated about 15% shale in the sandstone. 6.2.6 Kiowa Shale The Kiowa Shale is light -gray to black with interbedded thin limestones and, locally, sandstones. Although generally reported simply as black shale or blue shale, the thin, well -cemented sandstone interbeds may make the Kiowa difficult to separate from the Dakota and the Cheyenne sandstones, in drill cuttings. The Kiowa pinches out with the VI 3 99-028.003\Phase 2 Report\Hydrogeology