2004-12-07_PERMIT FILE - C1984063

• Permit No: C1984063
• IBM Index Class Name: Permit File
• Doc Date: 12/7/2004
• Section_Exhibit Name: Rule 2.04 Environmental Resources
• Media Type: D
• Archive: No

• 4. Geology
Harvey Gap is located in the Grand Hogback Coal Field. The
Grand Hogback is a prominent ridge of steeply dipping beds
of the Mesa Verde Group that extends from Meeker, Colorado
south to the Chair Mountain region south of Redstone.
Underlying the Mesa Verde Group is the Mancos Shale.
Overlying the Mesa Verde Group is the Wasatch Formation and
Ohio Creek Conglomerate (see Figure 3: Bedrock
Geology Map and Map HGP-18: Regional Geology and Hydrology
Map).
Creation of the Grand Hogback is due to the White River
uplift and erosion of the Mancos Shale and Wasatch
Formations around the resistant Mesa Verde Group. The
strike of the beds is N 80-85o W (see Map HGP-17: Geology
Map). The beds generally dip 45-60o to the southwest. In
the area of the mine dips of almost 700 occur. It is
believed that the near surface coal burn bulged and warped
the overlying beds. Angle of dip decreases in the dowr~dip
direction.
The Eastside Mine permit area is typical of the geology
found along the Grand Hogback. The Mancos Shale Formation,
• Mesa Verde Group, including the Iles and Williams ForK
Formations, and the Wasatch Formation are present in or
adJacent to the permit area. These units ar•e Cretaceous to
lower Tertiary in age. The oldest unit in the area is the
marine Mancos shale which intertongues with the overlying
Mesa Verde Group (Figure 1: Stratigraphic Correlation
Chart). The shale is gray to dark gray tending toward a
siltstone or mudstone that is fossiliferous. No major
faulting occurs in the area.
Along the Grand Hogback the Mesa Verde Group has been
subdivided into the Iles and Williams Fork Formations (see
Figure 1: Stratigraphic Correlation Chart and Figure 4:
Geologic Cross Section A-A). The Iles Formation overlies
the Mancos Shale and is capped by the Trout CreeK Sandstone
(Murray 1966).
The Iles Sandstone Formation extends from the sandstone unit
below the Harvey Gap seam #o the Trout Creek Sandstone
(Figues 1, 4, and 5; and Drawing 13: Lithologic
Correlation). The unit is laterally continuous within the
5-year permit area (see Map HGP-17: Geology Map). Local
terminology for specific beds has been used since conclusive
correlation outside of the permit area is not possible at
this time. The Mancos Shale intertongues with the formation
so that it is divided into the Sego, Corcoran, Cozette, and
Trout Creek members, The Sego was not identified.
23 Revised 5/87