The view from Pioneer Cabin, above Sun Valley, of the cirques at the head
of Hyndman Creek, Pioneer Mountains, (July, 1987). The rugged cirques are
carved from Proterozoic and Paleozoic metamorphic rocks as well as Eocene
granite. Pioneer Cabin was built as a ski base cabin in the 1930s during
early development of the Sun Valley resort .
Folded sedimentary rocks in the high Boulder Mountains, north of Ketchum,
looking south to the Pioneer Mountains. The peaks on the skyline, in the
Pioneer metamorphic core, are made of metamorphic and igneous rock, some
as old as 2300 million years, (July, 1987).
The north face of the Devil's Bedstead, the most prominent peak of the northern
Pioneer Mountains (11,865 feet high). The Bedstead can be seen from a large
area to the east and north in the Lost River Valley. View looks south up
the valley of Kane Creek from the Summit Creek road. The Bedstead is made
of Eocene intrusive rock. The Wildhorse detachment fault, separating lower
from upper plates of the Pioneer Mountains metamorphic core complex, is
in the saddle immediately east (left) of the Bedstead. In the shadows in
the foreground along Kane Creek are humpy mounds made of moraines formed
by the Kane Creek glacier during the Potholes glaciation (about 20,000 years
ago). These lie on flat river terraces formed during the earlier Copper
Basin (bull Lake) glaciation, (July,1993).
View of the Silent City of Rocks, southern Albion Range, southwest of Almo,
looking northeast from the summit of Bath Rock, (September, 1992). The Oligocene
City of Rocks lobe of the Almo Pluton forms the exfoliating and jointed
terrane in the foreground. The Archean Green Creek Complex underlies the
darker colored ridges on the skyline.