Ashmore Dome

Part of the La Salle Anticlinorium

Location

Southeastern Coles County (G-7,8)

References

Clegg 1965b, Meents 1965, Buschbach and Bond 1974

Description

The roughly oval Ashmore Dome provides structural traps for gas storage in basal Pennsylvanian sandstone and the Mississippian Salem Limestone. It trends north-south and is about 4 miles (6.5 km) long by 2 miles (3.2 km) wide. The Dome lacks a well defined axis. Dips on the west flank are about twice as steep as those on the east flank. Closure is 144 feet (44 m) on the Salem, 87 feet (26.5 m) on the Pennsylvanian gas sand, and only 25 feet (7.6 m) on the younger Seelyville (?) Coal Member (Meents 1965). The upward decrease in closure suggests that most uplift took place in late Mississippian and early Pennsylvanian time.