Harrison Creek Anticline
Part of the Ste. Genevieve Fault Zone
Location
Union and northernmost Alexander Counties (J,K-5)
References
Savage 1920, J. Weller 1940, J. Weller and Ekblaw 1940, Heyl et al. 1965, Nelson and Lumm 1985, Devera et al. 1994, Nelson and Devera 1994, Sargent et al. 1992
Description
The Harrison Creek Anticline was first mapped by Savage (1920) and was remapped and named by J. Weller and Ekblaw (1940). New mapping (Devera et al. 1994, Nelson and Devera 1994) provides additional information on this structure. The fold axis is slightly sinuous and extends about 7 (11.3 km) miles north from its southern terminus near the Union-Alexander County line. The anticline is depicted on plate 1 as it was mapped by J. Weller and Ekblaw (1940), who showed the fold extending about 8 miles farther north and 3 miles farther south than its true extent. The nearly symmetrical Harrison Creek has maximum dips of about 20° on the west flank and 15° on the east flank. Total structural relief is at least 550 feet (170 m), and closure is several hundred feet. Strata of the upper part of the Maquoketa Group (Cincinnatian) are exposed at the core and flanked by outward dipping Silurian and Lower Devonian beds.
At its southern end, the Harrison Creek Anticline plunges gently and dies out. Near its northern end, the east flank of the fold is truncated by the Atwood Fault. The anticline and fault disappear northward beneath the alluvium of Dutch Creek and do not reemerge north of that stream.
A dry oil test hole, Humble No. 1 Pickel, was drilled near the apex of the Harrison Creek Anticline. The well bottomed in the Cambrian Mt. Simon Sandstone at a total depth of 8,492 feet (2,590 m).
A gravity survey by Coe (Nelson and Lumm 1985), indicates a large positive anomaly coincident with the anticline. This evidence suggests that the anticline is the product of uplift of a basement fault block.
