Toulon Domes
Location
T13 and 14N, R5E, Henry and Stark Counties (C-4)
References
Treworgy 1979b, 1981
Description
Data from drilling for a compressed-air storage field indicates three domes, the Toulon Domes, in a north-south line near Toulon. Treworgy's (1979b) map shows structure on top of the Tonti Member of the St. Peter Sandstone, but only two wells actually reached this horizon; remaining control was projected downward from the top of the Galena Group. On this basis, the northern dome has about 100 feet (30 m) of closure and covers approximately 5 square miles (13 km2). The middle dome has 85 feet (26 m) of closure and covers 2.5 square miles (6.5 km2); the southern dome has about 55 feet (17 m) of closure and covers more than 2 square miles (5 km2). A pronounced anticlinal nose runs southeast from the middle dome. All three domes are roughly symmetrical, a fact that suggests they resulted from compaction over Precambrian hills rather than from horizontal compression or uplift of faults in the basement. The larger southern dome shown on plate 1 includes the middle and southern domes.
