A Geologic History of Fishlake

A Landscape in Motion

A Geologic History of Pando's Home, Fishlake Basin

A Literature Review | by Lorna Campbell and Lance Oditt (Jan 2022)

Utah is internationally recognized for its outstanding geological displays, largely focused on the rocks exposed and preserved in the National parks and monuments in the southeast of the state.  Utah is also home to the Pando Tree, the world’s largest tree. This review details the literature of the geologic characteristics of Fishlake Basin, Pando's home.

Fishlake Basin is located in the Fremont Range of the Fishlake National Forest. Fishlake Basin straddles a volcanically land that spans the physiographic boundary of the Colorado Plateau, the Basin and Range   and the Middle Rocky Mountains. This Colorado Plateau extends to the east into the Four Corners region of Utah, Colorado, Arizona and New Mexico. The Middle Rocky Mountains extend to the north and the Basin and Range province extend from the center and toward the west. (Figure 1).  Each of these provinces display different physiographic characteristics and show the complexity of different times in the Earth’s history.  The Fish Lake area (used throughout to refer to Pando’s location) sits in a broad transition zone between the Colorado Plateau and the Basin and Range province, where features of each domain can be observed.

regional map of utah showing various ecological boundaries
Figure 1. Physiographic provinces of Utah and location of Fish Lake (from Utah Geological survey.

The Colorado Plateau

The Colorado Plateau was uplifted in several pulses beginning around 70-80 million years ago (Laramide orogeny) which built many of the mountains across the west (including the Rocky Mountains) and again more recently beginning ~10 million years ago.  Despite these tectonic pulses deforming much of the west as they did creating the Rocky Mountains, the Colorado Plateau remained as an intact block despite being lifted upward more than 10,000’ above sea level in some areas. One exception to the generally undeformed geology of the region is the Waterpocket fold which formed 35-75 million years ago. The primary feature of Capitol Reef National Park just 40 miles southeast of Pando, this “buckle” as it is known colloquially, runs north-south for almost 100 miles. The more recent uplifting of the plateau led to erosion of the top part of the fold by great rivers, rain and wind, exposing its inclined time layers at the surface (Figures 2 and Figure 3). The oldest rocks observed in the center of the fold are around 248 Million years old (Permian Period).

table showing geologic layers of southern utah
Figure 2. Schematic cross section of the Rocks layers of the Colorado Plateau (from National Park Service brochure)
figure 3 illustration of geologic features in capitol reef national park
Figure 3. Schematic cross section through the Waterpocket fold (from National Park Service brochure)