Falls of the Big Sioux

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Falls of the Big Sioux
Leif Ericson Web Site

The Falls of the Big Sioux were carved in the hard Sioux Quartzite metamorphic rock on the Big Sioux River near the end of the Wisconsin Ice age, 14,000 years ago. The sand that eventually became this quartzite was deposited around 1.6 billion years ago, during the Precambrian, by a series of southeastward draining plexus of braided streams flowing into a shallow inland sea. The rock is pinkish, interlaced with deposits of claystone (Pipestone), and shale, most of which are shades of light to very dark pink. The red color comes from Iron Oxide. The Pipestone was quarried at three or more locations by paleo-Indian to modern Indian tribes. Two of the more prominent locations being Pipestone National Monument in S.W. Minnesota, and the ancient quarry at Palisades State Park near Garretson, S.D. . Uranium test holes were recently drilled near Brandon, S.D. Silver deposits were found in these drillings. Paleo-placer gold deposits are a possibility in Quartzite areas.
The strong, hard Sioux Quartzite was quarried in numerous locations. Many of the historic buildings in the area are made from this stone. Masons were brought from Europe to do the cutting and shaping. The Sweetman quarries near Sioux Falls are still a major source of Sioux Quartzite for construction. Sioux Quartzite, with a hardness of 7 on the Mohs scale, is extremly hard. The shale and claystone layers range from inches to 30 feet thick, while the quartzite itself can be over 500 feet thick. Ripple marks indicate a shallow water scenario. In early Paleozoic times, the quartzite was a steep mesa hundreds of feet above the surrounding land. During later Paleozoic times, the western edge of the quartzite sank as far as 2,500 feet below the surface. It was covered by deposits of the great Cretaceous Sea around 70 million years ago, while the eastern edge stayed on the surface awaiting the scouring it received by the ice sheets. These great ice bodies left striations on the quartzite showing direction of glacial flow. The color of this text is roughly the color of Sioux Quartzite.