Junction City Dome

Location

T1 and 2N, R1E, Marion County (H-5)

References

St. Clair 1917c, Shaw 1923, Bell 1926b, Brownfield 1954

Description

This feature, better described as a half-dome, is truncated on the west by the Centralia Fault Zone, which follows the dipping flank of the Du Quoin Monocline. As mapped by Brownfield on the upper Pennsylvanian "Shoal Creek" (now called Carthage) Limestone Member of the Bond Formation, the Junction City Dome is about 4.5 miles (7 km) from north to south and 2 miles (3 km) east to west. Closure at this horizon is 80 to 100 feet (24-30 m), and flanking dips are nearly symmetrical. On the Beech Creek ("Barlow") Limestone (ISGS open files), the enclosed area is smaller and centered farther south than on the Carthage. No doming is found west of the fault zone. These facts suggest the dome and fault zone developed at the same time in late or post-Pennsylvanian time.