WSP07795

• File Number: 7630.200
• Description: Wild and Scenic-Eagles Nest
• State: CO
• Date: 9/24/1971
• Author: USFS
• Title: Eagles Nest Wilderness Area-A Proposal-Eagles Nest Wilderness Arapahoe and White River National Forests
• Water Supply Pro - Doc Type: Report/Study

The U.S. Geological Survey and the Bureau of Mines, Department of the Interior,
conducted a field investigation of the area from 1967-69. The combined report of the
two Bureaus is published as Geological Survey Bulletin 1319-C. Mineral Resources of the
Gore Range-Eagles Nest Primitive Area and Vicinity, Summit and Eagle Counties, Colo-
rado. Its summary, quotation of which in this report is authorized by these two Bureaus.
follows:

"A mineral survey of the Gore Range-Eagles Nest Primitive Area and vicinity
in central Colorado was made by the U.S. Geological Survey in 1969 and by the
U.S. Bureau of Mines in 1968-69. An aeromagnetic survey was made earlier by
the Geological Survey, in 1967. The Primitive Area as defined occupies about
96 square miles in the highest and roughest part of the spectacularly rugged
Gore Range. Bordering areas on the flanks of the range were included in the
study to obtain necessary perspective of the range as a geologic unit, and also
to obtain information on areas that may come under discussion when the Primi-
tive Area is considered for inclusion in the National Wilderness Preservation
System. The total area considered herein is 215 square miles.

Geologically, the Gore Range is a fault block of Precambrian rocks between
the Gore fault on the west and the Frontal fault on the east. Sedimentary rocks
west of the Gore fault are Paleozoic and younger, and those east of the Frontal
fault are Mesozoic and younger. At the south, the range extends into the border
zone of the Colorado mineral belt, which in this region includes the higWy produc-
tive mining districts of Climax. Leadville, and Gilman, as well as many lesser
districts. The Mosquito fault, one of the controlling features of the ore deposits
at Climax and Leadville, extends into the southern part of the Gore Range and
connects with both the Gore and Frontal faults.

The block of Precambrian rocks that makes up the main body of the Gore
Range is broken by' many faults. The Gore and Frontal faults and many of the
interior faults as well are old faults that were later reactivated when the range
was elevated to its present height. This uplift began very late in geologic time
and it continues to the present. The Frontal fault in particular shows evidence of
very recent movement. The recent uplift, which began in late Tertiary time,
produced a high scarp that forms the abrupt eastern front of the range. along the
Frontal fault. Near Cataract Creek, the line of recent uplift turns westward,
along the north base of Eagles Nest Mountain, and connects with young faults
parallel to the Gore fault on the west side of Mount Powell and in the upper Piney
River drainage.

The mineral potential of the area was studied by examining the record of
mining activity and mineral production, by studying the geology in relation to
that of nearby productive mining districts, by examining the area for any signs
of mineral deposits, and by a program of sampling and detailed analysis both of
rocks showing any indication of mineralization and of sediment in the steams
draining the area.

No mineral production is recorded from the Primitive Area, although small
exploratory workings are present at several places. In the bordering areas, the
chief production has come from the Boss Mine, on North Rock Creek about half
a mile east of the Primitive Area. This mine produced about $238,000 worth of

',,;:,"

14