Wapella East Dome

Part of the La Salle Anticlinorium

Location

T21N, R3E, De Witt County (E-6)

References

Howard 1963a, b, 1964, Heigold et al. 1964, Clegg 1972, Treworgy 1978, Whitaker 1988

Description

A structural high and a partially eroded Silurian reef combine in the Wapella East Oil Field. The dome lies along the axis of the Downs Anticline, westernmost fold in the La Salle Anticlinorium of this area. Clegg (1972) mapped closure of about 35 feet (11 m) on the Danville Coal Member (Pennsylvanian). Howard (1963a, b) indicated closure of 90 feet (27 m) on the Devonian Cedar Valley Limestone and 110 feet (33 m) on top of the Silurian. By comparing the relative thinning of various units across the dome, Howard (1964) attributed relief of 25 feet (8 m) to compactional thinning across the reef and the remaining 85 feet (26 m) to tectonic uplift.

Insufficient data are available to map the dome on pre-Silurian horizons. Thus, one can only speculate on whether Wapella East was a high place favoring reef development during the Silurian Period.