Hudson Dome
Part of the La Salle Anticlinorium
Location
T24 and 25N, R2E, McLean County (D-5, 6)
References
Clegg 1972, Buschbach and Bond 1974
Description
Hudson Dome is a high point on the Downs Anticline, which marks the west edge of the La Salle Anticlinorium in this area. The dome is irregular in outline and 5 to 6 miles (8-10 km) in diameter. The east and north flanks are steeper than the south and west flanks. It apparently affects the entire stratigraphic column, and closure increases with depth. On the Danville Coal Member, as mapped by Clegg (1972), closure is about 85 feet (26 m); Buschbach and Bond (1974) mapped 160 feet (50 m) of closure on the basal Cambrian Mt. Simon Sandstone. A gas storage reservoir has been developed in the Mt. Simon.
Residual gravity contours (Heigold et al. 1964) show a similar configuration to structure contours of the top of the Mt. Simon Sandstone (fig. 25). This map also shows pronounced gravity highs corresponding with the neighboring Lake Bloomington and Lexington Domes. Note that the gravity survey was conducted before the domes were discovered. The coinciding gravity highs, the irregular outlines of the domes, and the absence of faulting on proprietary seismic reflection surveys suggest that Hudson, Lake Bloomington, and Lexington Domes Domes overlie Precambrian Hills composed of relatively dense rock. This example illustrates the value of gravity surveys in prospecting for structural traps.
Figure(s)
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