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Roadcuts in the St.Francois Mountains, Missouri: Basalt-dike swarm in granite, Precambrian-Paleozoic nonconformity, and a Lamotte channel-fill deposit

Eva B. Kisvarsanyi
Eva B. Kisvarsanyi
Missouri Geological Survey, Rolls Missouri 64501
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Arthur W. Hebrank
Arthur W. Hebrank
Missouri Geological Survey, Rolls Missouri 64501
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January 01, 1987


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.

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Figures & Tables


DNAG, Centennial Field Guides

North-Central Section of the Geological Society of America

Donald L. Biggs
Donald L. Biggs
531 Hayward Avenue Ames, Iowa 50010
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Geological Society of America
ISBN electronic:
Publication date:
January 01, 1987




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