Brocton Dome
Part of the La Salle Anticlinorium
Location
Southeastern Douglas and west-central Edgar County (F-8)
References
Mylius 1923,Clegg 1959, 1965b, Buschbach and Bond 1974
Description
Mylius (1923) and Clegg (1959) referred to this structure as the Oakland Dome; Clegg (1965b) renamed it the Brocton Dome to distinguish it from the Oakland Anticlinal Belt, of which the Brocton Dome was considered a part.
Clegg's (1965b) structure map of the Colchester Coal Member (Pennsylvanian) shows the Brocton Dome. It is elongated along a northwest to southeast axis and is about 12 miles (19 km) long and 7 miles (11 km) wide. The east flank of the anticline merges with the steep limb of the Edgar Monocline. Westward, the coal gradually declines toward the Murdock Syncline. Closure of the Brocton Dome on the Colchester Coal is approximately 100 feet (30 m).
Drilling for a potential gas storage field provided data for the Buschbach and Bond (1974) structure map of Brocton Dome on the Middle Devonian Lingle Limestone (fig. 20). Shape and size of the dome at this horizon are similar to the Pennsylvanian configuration, but closure on the Lingle is 220 feet (67 m), roughly twice as great as the Pennsylvanian closure. Here, as elsewhere on the La Salle Anticlinorium, uplift probably was partly late Mississippian to early Pennsylvanian, and partly post-Pennsylvanian.
