1Structural Geology

The Kellerville Quadrangle is located in eastern Adams, western Brown, and northern Pike Counties, Illinois. It oc-curs a few miles east of the crest of the north-south trending Mississippi River Arch. Regional dips average 8 feet per mile to the east (Howard 1961), but local flexures have pro-duced structures which often obscure this regional dip. The most prominent structural feature in the region is the Fishhook Anticline (Meents 1958, Howard 1961), which is about 8 miles long and trends east-southeast. It is located south of the Kellerville Quadrangle on the adjacent Fishhook Quadrangle. An irregular structural terrace occurs on the northeast flank of the Fishhook Anticline in the Kellerville Quadrangle. This terrace is about 250 feet lower than the crest of the anticline and trends in the same east-southeast direction through the central and southeastern portion of the Quadrangle. There is some closure on this terrace (see economic geology below) with oil accumulation in what is known as the Kellerville and Siloam pools (Meents 1958, Howard 1961). The remainder of the quadrangle (roughly the north half) is structurally lower and generally flat com-pared to the structural terrace at the Kellerville and Siloam pools. Economic Geolog