Oblong Anticline (New)
Part of the La Salle Anticlinorium
Location
T7N, R13W, Crawford County (G, H-8)
References
Blatchley 1913, Cady 1920, Potter 1956, Bristol and Buschbach 1973, Bristol and Howard 1976, Stevenson et al. 1981
Description
Treworgy (1981) listed the Oblong structure as a "significant unnamed structure." It is hereby named the Oblong Anticline for the nearby town of Oblong.
The Oblong Anticline is in line with the Hardinville Anticline, from which it is separated by a saddle. Both anticlines follow the upper limb of the Charleston Monocline in the La Salle Anticlinorium. The axis of the Oblong Anticline trends slightly west of north and plunges to the south.
Potter's (1956) map of the Herrin Coal Member (Pennsylvanian) is the most detailed structure map of the Oblong Anticline. This map (fig. 40) shows the anticline to be about 3 miles (5 km) long and 1 mile (1.6 km) wide, and to have about 50 feet (15 m) of closure. Bristol and Howard's (1976) map of the Ste. Genevieve Limestone indicated a small enclosed area on the Oblong Anticline. Their unpublished work map (ISGS, open files) indicates at least 60 feet (18 m) of closure on the anticline. No closure is shown on the New Albany Group (Stevenson et al. 1981) or Galena (Trenton) Group (Bristol and Buschbach 1973). These two maps show a south-trending nose separated from the Hardinville Anticline by a saddle. A shortage of control points on the deeper horizons and the use of a 100-foot contour interval may account for absence of mapped closure.
Figure(s)
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