PROJ00132

• Contract/PO #: FS0014X
• Contractor Name: Southern High Plains Ground Water Management District
• Contract Type: Loan
• Water District: 0
• County: Prowers
• Loan Projects - Doc Type: Feasibility Study

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

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.

7.2.6 Kiowa Shale
The Kiowa Shale is light-gray to black with interbedded thin limestones and, locally,
sandstones. These thin, well-cemented sandstones make the Kiowa difficult to separate
from the Dakota and the Cheyenne sandstones which are above and below it
respectively. The Kiowa pinches out with the other Cretaceous strata to the southeast
and varies from 40 to 90 feet across the rest of the study area. It may be thinner or
discontinuous in the subsurface, as the Kiowa is not always recognizable in the lithologic
descriptions.

7.2.7 Dakota Sandstone
The Dakota Sandstone is a series of sandstones and sandy shales present in all except
the southeastern part of the Basin and adjacent to the Two Butte intrusive, where it was
uplifted and removed by erosion. It outcrops north and west of the Basin and in the
deeper incised drainages. It is estimated to be between 85 and 195 feet thick, with cliff-
forming ledges up to 50 feet thick exposed in the southwestern canyons.

The Dakota bedding character varies from thin-bedded to cross-bedded, to massive and
from fine-grained quartzites to coarse-grained sand/gravel lenses. The color is usually
buff to dark brown, but can be dark red-brown with ironstone concretions, and dark-gray
to dark-brown where lignitic or coaly beds are present.

7.2.8 Graneros Shale
The Graneros Shale is the lowest member of the Colorado Group. The Graneros and
Greenhorn are the only significant member of the Colorado Group present in the Basin.
Some Carlile Shale may be present in the Basin, but this has not been confirmed. The
overlying Niobrara Chalk and Pierre Shale formations are not present in the Basin. As
shown in Table 7-1, the Colorado Group includes, in ascending order, the Graneros,
Greenhorn Limestone, Carlile Shale, Niobrara Chalk and Pierre Shale. The Graneros is
present only in the northern part of the Basin where it may be up to 150 feet thick. It is
shown on the northern part of cross-sections B-B', C-C', 0-0' and E-E', and pinches out
to the southeast. The Graneros is exposed in the Bear Creek tributaries west of
Springfield and in northwest Baca County, just northwest of the Basin boundaries (i.e.,
where the drainages are tributary to the Arkansas River Basin).

VII-3