Red Butte Canyon Geology

Red Butte Bedrock

The rocks underlying Red Butte Canyon range in age from Holocene deposits of our time to Mississippian rocks that are about 360 million years old. Holocene and Pleistocene deposits are unconsolidated, consisting mostly of landslides or alluvium deposited by existing streams. The aerial distribution generally follows an east-west axis, and a description of the deposits is given in Table 1.

The older rocks range in age from Mississippian to Jurassic, a span of about 220 million years. They are all consolidated now, but originally they were formed as deposits in oceans or inland seas or as sand dunes in an arid environment. No rocks representing the approximately 140 million years between the end of Jurassic time and the Holocene are present in Red Butte Canyon. Either they were never deposited or they have been eroded.

The consolidated rocks in most parts of the lower walls of the canyon consist chiefly of shale, with some gritty quartzite and sandstone. The upper southeast-facing slopes consist mostly of limestone with some sandstone and limy shale. The upper northwest-facing slopes are made up mostly of sandstone with limestone and limy shale near the southeast divide. Fig. 3 shows the distribution of the rocks in the canyon, and they are described in Table 1.

The older consolidated rocks in the canyon generally dip toward the southeast and they form the northern flank of a large syncline whose axis trends toward the northeast and whose southern flank is in Mill Creek Canyon, about 6.5 km to the south. The rocks are cut by numerous normal faults which are part of the Wasatch fault zone, a lengthy fault zone that bounds the west face of the Wasatch Range for almost its entire length. Movement along these normal faults has resulted in horizontal displacement of the rock formations, whereas movement along the Black Mountain thrust fault in the northwestern part of the canyon has raised older rocks to a position overlying younger rocks. The faults and their effects on the consolidated rocks are visible from the ground.