Investigation of potential geologic hazards near the Thistle landslide, Utah County, Utah (RI-213)

By: G. C. Willis

In the spring of 1983 an old landslide near Thistle, Utah reactivated and moved downslope, forming a dam 220 feet (67 m) high which blocked a major railroad, highway, and river. Thistle Lake, which formed behind the landslide dam, reached a depth of 160 feet (50 m) before being drained by a diversion tunnel constructed that summer. One of several long-term proposals suggests that either the landslide be developed into a permanent dam and reservoir or that a dam and reservoir be constructed immediately upstream from the blockage. Irving J. Witkind, a geologist of the U.S. Geological Survey, expressed concern regarding two possible geologic hazards which he believed could exist in the area and could be of concern to a permanent dam and reservoir. The geologic structures he is concerned with are the Thistle Canyon fault, a feature mapped by earlier workers, and the Thistle Creek diapir, a feature which Witkind proposed. Because of poor surface expression and the lack of subsurface data, the existence and configuration of the Thistle Canyon fault and Thistle Creek diapir are controversial. This study indicates evidence supports the existence of the Thistle canyon fault. It also indicates that the Thistle Creek diapir may be present but probably is a smaller structure and is deeper in the subsurface than proposed by Witkind, and thus presents a lesser concern than he suggests. Both structures are of concern, however, and should be investigated further through several approaches, primarily through the acquisition of subsurface data.

Other Information:
Published: 1987
Pages: 24 p.
Location: Utah County
Media Type: Paper Publication