Rock Creek Graben
Location
Hardin and Pope Counties, Illinois and Livingston County, Kentucky (J, K-7 and pl. 2)
References
J. Weller et al. 1952, Baxter et al. 1963, Ross 1963, 1964, McGinnis and Bradbury 1964, Baxter and Desborough 1965, Heyl et al. 1965, Baxter et al. 1967, Kolata et al. 1981, Trace and Amos 1984
Description
Like the Dixon Springs Graben, the Rock Creek Graben is a large and complicated zone of downfaulting. The Rock Creek Graben is as much as 2.5 miles (4 km) wide and strata have been displaced downward as much as 2,000 feet (600 m) within it. The trend is 55°E in eastern Hardin County. This trend changes to N20°E near Rosiclare where the graben crosses into Kentucky and then reenters Illinois in southern Pope County. Drilling in Massac County indicated that the graben continues beneath Cretaceous and Tertiary rocks in the Mississippi Embayment. The total length is more than 30 miles (50 km).
Most of the faults are high-angle normal, but high-angle reverse faults are reported to occur along the northwest side of the graben. The combination of reverse and normal faulting might indicate two or more periods of movement under different (compressional and tensional) stress regimes, as on the Lusk Creek and Shawneetown Fault Zones.
