PERMFILE51657

• Permit No: C1981008A
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: NH1 TAB 6 GEOLOGIC INFORMATION
• Media Type: D
• Archive: Yes

State Reg.
glanerate of the Dakota separates the Dakota Sandstone fran the
underlying Burro Canyon Formation (Lohman, 1965). The Burro
Canyon comprises a varied assemblage of white, gray, and light
brawn sandstone and conglamsates interbedded with green and
purplish shales, siltstones, and mudstones, and thin beds of
immure limestone. It may attain a maximum thickness of 200 feet
in the area (Williams, 1969).
In the Nucla Syncline, exposures of the Burro Canyon are re-
stricted to the rims of mesas and deep canyons located to the
west and northwest of the mine. Small map scale and lithologic
similarity with the Dakota Sandstone cause these formations to
be mapped together as undifferentiated in the southern part of
the syncline (see FSchihit 6-1).
Pre-Burro Canyon Formations (U. Jurassic to Precambrian).
Table 6-1 sununarizes the general lithologic characteristics and
• thicknesses for Pre-Burro Canyon Formations. As mentioned be-
fore, these formations show slight to extreme variations in
thickness between anticlines and synclines due to past tectonic
activity and syntectonic sedimentation. Most, if not all, of
these formations probably underly the Nucla Syncline. Hocever,
the lateral extent and thickness of most formations cannot be
predicted accurately over a few miles distance.
Exposures of these formations are generally restricted to the
steeply, dipping flanks and gyres of anticlines, and the walls
and floors of deep canyons. Excellent exposures of all for-
mations, except the Pennsylvanian Hermosa Formation, are seen
in the Unaweep, Iblores, and San Miguel River Canyons along
Route 141 between Whitewater, Colorado and Naturita, Colorado.
•~
6-8