Wind River Range

The Wind River Range is the largest and highest discrete mountain mass in Wyoming, containing most of the state’s highest summit peaks, such as Gannett Peak (at 13,804 feet, the highest point in Wyoming), Fremont Peak (13,745 feet), and Wind River Peak (13,192 feet). Trending N 40° W from South Pass City on the south to Fish Lake Mountain on the north, the range is a major barrier between western and central Wyoming; it separates the Wind River Basin to the northeast from the Greater Green River Basin to the south and southwest. The northeast flank of the Wind River Range consists of a 96-mile-long, continuous band of Paleozoic sedimentary rocks exposed in a series of hogbacks and dip slopes that dip eastward into the Wind River Basin. The core of the range exposes an extensive area of some of the oldest Precambrian rocks in the state. The southwest flank of the range is characterized by an extensive thrust fault system, with Precambrian rocks thrust south and southwest onto relatively flat-lying Tertiary rocks in the Green River Basin. The fault system extends eastward where Precambrian rocks in the South Pass area were thrust over Tertiary rocks of the northern Great Divide Basin. A survey by the Consortium for Continental Reflection Profiling (COCORP) used reflection seismology across the southern Wind River Range along Wyoming State Highway 28 to gather new data on crustal structure. The data revealed that the thrust fault along the western boundary of the range dips to the east at an angle of 30° and extends to a depth of approximately 18.7 miles.

Glaciated peaks mark the high central region of the range; glaciers and permanent snowfields lie in the higher valley heads. U-shaped glaciated valleys issue from both the east and west sides of the Continental Divide, which forms the backbone of the range. On the west side of the range, a broad bench-like platform at about 9,400 feet above sea level is dotted by a myriad of glacial lakes. This high, relatively flat subsummit surface above timberline is dissected, as if by a biscuit cutter, by steep-sided glacial valleys. The range’s highest peaks stand high above the subsummit surface. At the base of the mountain flanks, long, deep, moraine-dammed lakes—such as Fremont and New Fork on the west side and Dinwoody and Bull lakes on the east side—occupy valleys where glacial ice once flowed down from the higher regions onto the basin floor.

The South Pass area at the south end of the Wind River Range hosts a sequence of Archean (more than 2.5 billion years old) supracrustal metamorphic rocks called a greenstone belt that contains the state’s principal gold deposits as well as iron ore deposits. Besides being an important point along the Oregon Trail, South Pass was also the site of extensive lode and placer gold mining in the 19th century and of a surface iron ore mine and mill in the 20th century. The area remains attractive for gold prospectors and has a rich and well-preserved history.

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