Roadcuts in the St.Francois Mountains, Missouri: Basalt-dike swarm in granite, Precambrian-Paleozoic nonconformity, and a Lamotte channel-fill deposit
Eva B. Kisvarsanyi, Arthur W. Hebrank, 1987. "Roadcuts in the St.Francois Mountains, Missouri: Basalt-dike swarm in granite, Precambrian-Paleozoic nonconformity, and a Lamotte channel-fill deposit", North-Central Section of the Geological Society of America, Donald L. Biggs
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This composite site features roadcuts along U.S.67 and Missouri 72 in the eastern St.Francois Mountains, in Madison County, Missouri (Fig. 1).
STOP 1 (NW¼SW¼NE¼Sec.35, T.34N., R.6E.), along U.S.67 is 14.8 mi (23.7 km) south of the junction, west of Farmington, of U.S.67 and Missouri W. It is located on the Fredericktown 7½-minute Quadrangle. Roadcuts at this stop display a basalt-dike swarm in the Precambrian Slabtown Granite.
STOP 2 (NE¼SE¼NW¼Sec.11, T.33N., R.6E.) is along Missouri 72; from STOP 1, proceed 2.7 mi (4.3 km) south on U.S.67, then 1.8 mi (2.9 km) west on Missouri 72 (Fig. 1). Roadcuts at this locality expose the nonconformable contact between Precambrian and Paleozoic rocks in a spectacular manner.
STOP 3 (NE¼NE¼NE¼Sec.9, T.33N., R.6E.) is 1.7 mi (2.7km) west of STOP 2, along Missouri 72 (Fig. 1). It is located on the Rhodes Mountain 7½-minute Quadrangle. This site displays horizontally bedded, channel-fill sediments within basal boulder conglomerate mantling the Precambrian surface.