The stratigraphy of the Sperati Point Quadrangle, McKenzie County, North Dakota
The Sperati Point Quadrangle is in McKenzie County, northwestern North Dakota, about 30 miles south-southwest of Watford City, North Dakota. The quadrangle is bounded by Ts. 146-148 N., Rs. 100- 101 W., and encompasses an area of about: 54 square miles. The topography consists of weakly dissected upland plains and, adjacent to the Little Missouri River and tributaries, well dissected, well drained, badland areas characterized by extensive slumping. About 570 feet of the Sentinel Butte Member of the Tongue River Formation of Paleocene age is exposed in the quadrangle. The lower 200 to 250 feet is dominantly grayish, fine to medium-grained greywacke sandstone and siltstone. The remainder of the section is dominantly gray, yellow, and brownish claystone, siltstone, shale and lignite. Characteristic sedimentary structures are "cannonball" and "log-lL-e" siltstone and c aystone concretions. A blue bentonitic claystone, the "blue bed", which occurs about 200 feet below the top of the member, and a yellow clayey siltstone, the "yellow bed", 45to 60 feet above the "blue bed", were correlated in measured sections of the member. Fresh-water pelecypods and gastropods occur throughout the member, but most of these mollusks are found in the "yellow bed". Plant fossils occur in benconitic claystones, siltstones, lignitic shales and lignites. The Sentinel Butte Memb2r is comprised of alluvial, fluviatile, and lacustrine sediments deposited on a vast alluvial or coastal plain. Major source areas for these sediments were presumably in the Rocky Mountains to the west and the Black Hills to the south. Conformably overlying the Sentinel Butte Member is about 100 to 160 feet of yellow silty clay and micaceous sandstone of the Golden Valley Formation of Eocene age. Wisconsinan (?) glacial outwash deposits and preglacial Wiota Gravel (?) are also present in the quadrangle.
Geology, Stratigraphic; Geology--North Dakota--McKenzie County
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