Guidebook—Geology of the Kanopolis Lake Area

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Dakota Formation

The resistant, conspicuous beds of the Dakota Formation are the dark-brown sandstones cemented with iron oxide that cap the hills and produce the irregular topography so common in the Smoky Hills. The Dakota Formation is a thick, heterogeneous sequence of clay, siltstone, and sandstone. The sandstones are locally cemented with hematite and limonite. The Dakota contains lignite and locally, beds of "quartzitic" sandstone. "Quartzite" concretions have been described in both the Kiowa and Dakota Formations (see discussion for Stop 2, Mushroom Rock State Park). More than one bed of concretions have been observed, and they may, in reality, occur in both units. Crossbedding is a prominent feature in most sandstones in the Dakota.

Although the Dakota is thought of as primarily sandstone, the dominate lithology is light-gray to light-greenish-gray siltstone or clay dappled with abundant red to reddish-brown mottles. Clay and siltstone compose as much as 70 percent of the thickness of the Dakota Formation in many areas. In Ellsworth County, the Dakota Formation ranges from 190 to 250 feet thick.

The Dakota Formation is generally thought to have been deposited during the retreat of the Kiowa sea under nonmarine conditions in a low-lying coastal or deltaic plain bordering the Cretaceous sea. The terrestrial nature of Dakota sedimentation can be inferred from the general absence of marine fossils, the abundance of leaf fossils, and the occurrence of lignitic beds (lignite is a low-grade form of coal and indicates swampy conditions). Sandstones in the Dakota Formation were deposited mainly by streams and rivers. Imprints of oak, willow, walnut, sycamore, magnolia, laurel, and sassafras leaves indicate the climate was mild.

Marine fossils in the upper part of the Dakota and the deposition of marine sediments of the overlying Graneros Shale Formation mark the return of higher sea levels in central Kansas.

Crossbedding—Crossbedding is a series of thin, inclined layers in a larger bed of rock (usually sandstone) that form a distinct angle to the principal horizontal bedding plane. Formed by currents of water or wind, crossbedding is found in dune, stream channel, or delta deposits. The direction in which the beds are inclined usually indicates the direction the current of water or air was flowing at the time of deposition.

The Dakota Aquifer

In recent years these geologic units have been the subject of particular interest because of their potential as a water source. With ground-water-level declines in the High Plains aquifer of western Kansas, underlying Cretaceous rocks may be an important source of water. Water specialists often refer to the Dakota, Kiowa, and underlying Cheyenne Sandstone formations as one unit—the Dakota aquifer. Their research has shown this aquifer is not capable of producing water in amounts as large as the High Plains aquifer, and water quality varies greatly from place to place. As a result, the Dakota aquifer will probably never be as important as the High Plains aquifer, but with careful management could produce significant amounts of water.

Sources

Bayne, C.K., Franks, P.C., and Ives, W., Jr., 1971, Geology and ground-water resources of Ellsworth County, central Kansas: Kansas Geological Survey, Bulletin 201, 84 p. [available online]

Feldman, H.R., comp., 1994, Road log and field guide to the Dakota Aquifer strata in central Kansas: Kansas Geological Survey, Open-file Report 94-15, 30 p.

Fent, O.S., 1950, Geology and ground-water resources of Rice County, Kansas: Kansas Geological Survey, Bulletin 85, 142 p.

Franks, P.C., 1969, Nature, origin, and significance of cone-in-cone structures in the Kiowa Formation (Early Cretaceous), north-central Kansas: Journal of Sedimentary Petrology, v. 39, no. 4, p. 1438-1454.

Franks, P.C., 1975, The transgressive-regressive sequence of the Cretaceous Cheyenne, Kiowa, and Dakota formations of Kansas, in, W.G.E. Caldwell, ed., The Cretaceous System in the Western Interior of North America: The Geological Association of Canada, Special Paper 13, p. 469-521.

Franks, P.C., 1979, Paralic to fluvial record of an Early Cretaceous marine transgression--Longford Member, Kiowa Formation, north-central Kansas: Kansas Geological Survey, Bulletin 219, 55 p. [available online]

Scott, R.W., 1967, Paleontology and paleoecology of the Kiowa Formation (Lower Cretaceous) in Kansas: Unpublished Ph.D. dissertation, University of Kansas, 308 p.

Scott, R.W., 1970, Paleoecology and paleontology of the Lower Cretaceous Kiowa Formation, Kansas: University of Kansas Paleontological Contributions, Article 52 (Cretaceous 1), p. 1-94.

Wicander, R., and Monroe, J. S., 1989, Historical geology--evolution of the earth and life through time: St. Paul, Minnesota, West Publishing Company, 578 p.

Zeller, D.E., ed., 1968, The stratigraphic succession in Kansas: Kansas Geological Survey, Bulletin 189, 81 p. [available online]

This guidebook is also available in print form as Kansas Geological Survey, Open-file Report 2003-52, from KGS Publications Sales office, 785-864-3965.

Unless noted otherwise, illustrations by Jennifer Sims, Kansas Geological Survey; photographs by John Charlton, Kansas Geological Survey. Text by Jim McCauley, Bob Sawin, Rex Buchanan, and Liz Brosius, Kansas Geological Survey.

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