Cooks Mills Anticline

Location

Northwestern Coles and southwestern Douglas Counties (F-7)

References

Clegg 1959, 1965b

Description

Clegg mapped this structure from subsurface data on the base of the Pennsylvanian System and on the Colchester, Herrin, and Danville Coal Members. It is also defined on structure maps of the Beech Creek ("Barlow") and Karnak Limestones (ISGS open files). Configuration is similar at all four levels: an elongate high, about 10 miles (16 km) long and 3 miles (4.8 km) wide, plunging about S35°W. A series of irregular domes, saddles, and depressions occurs on the broad crest of the anticline. Local closure is at least 60 feet (18 m). The Cooks Mills structure is separated from the much larger Tuscola Anticline on the east by a slight saddle, and lies offset to the Mattoon Anticline on the south. The Cooks Mills Consolidated Field, on the anticline, has produced 1.9 billion cubic feet of gas and 2.56 million barrels of oil from Chesterian, Valmeyeran, and Devonian pay zones. Natural gas is stored in the Chesterian Cypress Sandstone.