Omaha Graben

Location

T7S, R8E, Gallatin and White Counties (J-7)

References

Bristol 1975

Description

The Omaha Graben is bounded by two parallel normal faults that strike northward from the north edge of Omaha Dome. The faults are at most 4 miles (6.4 km) long and less than 0.5 mile (0.8 km) apart. Maximum throw is about 60 feet (18 m) in Pennsylvanian rocks and it decreases downward. Bristol (1975) interpreted the faults as tension-release structures associated with igneous intrusion under the Omaha Dome. This explanation appears unlikely because the faults are far from the apex of the dome and no other faults radial to Omaha Dome have been detected in spite of dense drilling. An alternate interpretation is that the graben developed under regional east-west extensional stress that created the Wabash Valley Fault System.