Little Cache Fault Zone (New)

Location

T11, 12 and 13S, R3E, Johnson County (K-6)

References

S. Weller and Krey 1939, J. Weller 1940, Dial 1963, Trask and Jacobson 1990, Jacobson 1991, Nelson et al. 1991, Nelson 1993

Description

The name Little Cache Fault Zone was given by Nelson et al. (1991) to a zone of high-angle normal faults that follows the valley of Little Cache Creek in central Johnson County. This fault zone first appeared on the maps of S. Weller and Krey (1939) and J. Weller (1940). Recent mapping (Dial 1963, Trask and Jacobson 1990, Jacobson 1991, Nelson 1993) has modified details of the earlier mapping only slightly. The faults outline grabens that are 0.25 to 0.5 mile (0.4 to 0.8 km) wide and trend slightly east of north. A maximum displacement of 280 feet (85 m) was noted on a west-dipping fault in Section 15, T12S, R3E (Nelson 1993). Relatively little drag or brecciation is associated with this fault zone. Fault surfaces dip 70° to 80° and show vertical (dip-slip) striations.

The Little Cache Fault Zone lies a short distance west of the western termini of the McCormick and New Burnside Anticlines. Several normal faults are thought to be products of an extensional episode that postdate the compressional event responsible for the anticlines (Nelson 1987a, Nelson et al. 1991).