07

Kings Peak

Duchesne County, Utah

13,528 ft

4,123 m

Kings Peak catches the morning sun above shadowed cliffs at the head of the Henrys Fork cirque basin in the heart of the Uinta Mountains. The layered sedimentary strata, consisting mostly of sandstone, siltstone, and shale, belong to the Precambrian Uinta Mountain Group, which underlies much of the Uinta Mountains.

Kings Peak catches the morning sun above shadowed cliffs at the head of the Henrys Fork cirque basin in the heart of the Uinta Mountains. The layered sedimentary strata, consisting mostly of sandstone, siltstone, and shale, belong to the Precambrian Uinta Mountain Group, which underlies much of the Uinta Mountains.

 

The origins of Kings Peak, the highest point in Utah’s Uinta Mountains, go back some 750 million years to late Precambrian time, when life on Earth consisted solely of microorganisms such as cyanobacteria (blue-green algae). Utah occupied a place on the edge of a former continent called Laurentia, which at that time was beginning to separate from what would eventually become Antarctica and Australia along a continental rift zone. As Laurentia slowly moved away from the other continents, an arm of the rift opened up and extended inland, forming a long, narrow basin. Over time, sand, gravel, silt, and clay were carried by streams from the continental interior and deposited in the rift basin, eventually accumulating to a thickness of 16,000 feet (4,900 m). This sequence of sedimentary rocks is now known as the Uinta Mountain Group, and contains cyanobacteria that are Utah’s oldest fossils.

Hikers negotiate talus on interbedded sandstone, siltstone, and shale of the Uinta Mountain Group at the head of the Henrys Fork basin. Like all of the major valleys throughout the Uintas, the Henrys Fork basin was filled with ice during Pleistocene glacial episodes, the most recent being around 24,000 to 12,000 years ago.

Hikers negotiate talus on interbedded sandstone, siltstone, and shale of the Uinta Mountain Group at the head of the Henrys Fork basin. Like all of the major valleys throughout the Uintas, the Henrys Fork basin was filled with ice during Pleistocene glacial episodes, the most recent being around 24,000 to 12,000 years ago.

 

Fast-forward to about 65 million years ago, at the end of the Age of Dinosaurs. What had been the rifted margin of Laurentia is now evolving into western North America. But, instead of being extended and pulled apart, western North America is now being squeezed and compressed in a mountain-building event called the Laramide orogeny. During Laramide time (about 65 to 40 million years ago), numerous upwarps and adjacent basins formed throughout the Rocky Mountain region, including what would eventually be known as the Uinta Mountains, the Green River Basin to the north, and the Uinta Basin to the south. Uplift of the Uinta Mountains occurred partly by broad folding (forming the Uinta anticline) and partly by fault movement along reverse faults that extend the entire length of the range along both the north and south flanks. So the sediments that accumulated 750 million years ago in a rift basin near sea level now lie as sedimentary rocks 13,000 feet (4,000 m) above sea level, forming a mountain range whose unusual east-west orientation reflects the configuration of the ancient rift basin.

The present topography of the Uinta Mountains is largely the result of Pleistocene glacial episodes, the most recent having reached its maximum extent about 20,000 years ago. Cirque glaciers joined to form confined valley glaciers, which generally did not cover the crest of the range or major drainage divides. The result is deep, glacially scoured valleys separated by sharp ridges (arêtes) and broad, unglaciated alpine plateaus (biscuit-board topography).

Oblique aerial view (Google EarthTM image), looking east at Kings Peak and the upper Henrys Fork basin, shows the characteristic biscuit-board topography of the Uinta Mountains. Peaks, ridges, and alpine plateaus preserve bedrock that remains after glaciers eroded the valleys. (Base image © 2015 Google Inc., used with permission. Map data: Google, USDA Farm Service Agency.)

Oblique aerial view, looking east at Kings Peak and the upper Henrys Fork basin, shows the characteristic biscuit-board topography of the Uinta Mountains. Peaks, ridges, and alpine plateaus preserve bedrock that remains after glaciers eroded the valleys. (Base image © 2013 Google Inc., used with permission. Map data: Google, USDA Farm Service Agency.)

  • LAT./LONG. 40.776 N / 110.373 W
  • Land Status/Administration
    Ashley National Forest
  • Physiographic Province
    Middle Rocky Mountains
  • Representative Rocks:
    • Class: Sedimentary
    • Type: Sandstone
    • Age: Precambrian
    • Landform: Arête