Skip to main content

Stop #3 Water Tank

(You are one mile high, 5280 feet)

The formation you are looking at is the Precambrian Mineral Fork Tillite (Turn to the geologic map and find your position). It is olive brown in color, and contains boulders, cobbles, and pebbles of dolomite and quartzite in a fine mud matrix. The formation is named after the Mineral Fork of the Big Cottonwood Creek close to Salt Lake City. The deposit is 3,000 feet thick in this area.


The origin of the tillite has been disputed by geologists for years. Most believe that the formation was an ancient till, deposited by a large glacier. Others believe the formation to be an ancient mud flow. Although the tillite does have similar characteristics to a mud flow, the evidence of a glacial origin is hard to dispute.

The tillite was most likely deposited as large tongues of ice extended into the area scooping out broad smooth basins. As this happened, thick deposits of till accumulated. The cobbles and boulders in the tillite are striated, attesting to a glacial origin. Geologists have also studied the tillite using extremely thin sections of rock under a microscope. The formation is virtually indistinguishable from modern tills, and from pre-Cambrian tillites in other parts of the world. The smooth profile of the deposition basins, and the polished surface of the underlying rocks suggest ice action as well. This formation is a shining example of the value of careful observation. By making proper observations, geologists are able to decipher an environmental profile from well over 500 million years ago.

Continue following this high trail to the east until you have reached the base of the mine. At this point, you may wish to take a side trip up the small pathway to the mine, or you can turn to the south and follow the small path back across the creek to the main trail. Across the creek, you will see massive walls of quartzite which have been thrusted into a vertical position. During the summer, these walls are filled with rock climbers trying to push the limits of their ability. If you look closely, you can see many of the fractures in the quartzite which are used for grips and holds by the climbers.

The tour backtracks approximately 100 feet at this point. Proceed down the canyon 100 feet until you have reached the base of the massive walls of quartzite. Stop #4 begins at the large boulders located at the base.