Rock City, Kansas

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Rock City
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Rock City, 2006
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Location Minneapolis, Kansas, Ottawa, Kansas, Kansas, United States
Coordinates 39°5′27.20″N97°44′7.99″W / 39.0908889°N 97.7355528°W / 39.0908889; -97.7355528
Elevation1,276 ft (389 m) [1]
Website Web Site
Designated1976

Rock City is a park located on hillsides overlooking the Solomon River in Ottawa County, Kansas. It is 3.6 miles south of Minneapolis, Kansas and just over 0.5 mile west of Kansas highway K-106 and the Minneapolis City County Airport on Ivy Road. In a patch of prairie about 500 meters (1,600 feet) long and 40 meters (130 feet) wide, Rock City contains three clusters of large spherical boulders. These three clusters contain a total of 200 spherical boulders. It has been designated as a National Natural Landmark.

Contents

The park, owned by a non-profit corporation, has a visitor center and picnic tables. A small admission fee, which is used to maintain this park, is charged.

The remarkable size and spherical shape of these rock formation was first noted by Bell. [2] Later, these boulders were either noted or described by Gould, [3] Landes, [4] Shaffer, [5] Ward, [6] and Swineford. [7] Shaffer [5] was the first person to map the distribution of these boulders at Rock City and investigate their petrography in detail. [8]

Physical characteristics

The large spherical boulders in Rock City are giant calcite-cemented concretions, typically called "cannonball concretions" because of their shape. They range in diameter from 3 to 6 meters (9.8 to 19.7 ft) with the average diameter being 3.6 meters (12 feet). These concretions lie 2 to 8 meters (6.6 to 26.2 ft) apart. [8] Similar giant calcite-cemented concretions have also been found in a quartzite quarry within Lincoln County and in exposures of the similar age sandstones in Utah and Wyoming. [8] [9]

These boulders consist of well-sorted, medium-grained sandstone, which is tightly cemented by calcite. The sandstone consists of more than 95 percent quartz sand. About 20 percent of the original sandstone, mostly feldspar grains, has been replaced by the calcite. Pyrite, which is now oxidized to goethite, occurs within the calcite cement of these concretions as microscopic crystals and very small, knobby concretions. The pyrite concretions typically are about 30 cm (1-foot) in diameter. Also, included within these calcite concretions are smaller calcite concretions, which have been engulfed by the growth of the larger concretions. [8]

The host rock, which contained these spherical boulders, consists of well-sorted, medium-grained, highly porous, and friable sandstone. Being only weakly indurated by small amounts of iron oxide, sometimes seen as Liesegang rings (banding) at Rock City, it is considerably softer and very much more easily eroded than the calcite concretions. The sand comprising it accumulated within a river channel, which is part of the Dakota Sandstone, which accumulated within a low-lying coastal plain. Differential cementation and later erosion of cross-bedding inherited from the riverine sand, in which these concretions occur, created the "ornamentation", which these concretions exhibit. [8]

Origin

In the past, the origin of the spherical boulders found at Rock City had been erroneously interpreted as glacial boulders, corals, concretionary masses of limestone, and normal erosional remnants of sandstone. Shaffer [5] was the first person to recognize them as calcite-cemented concretions. From a detailed examination of the mineralogy of these concretions and the carbon and oxygen isotopes of the calcite cement comprising them, McBride and others [8] concluded that they formed as the result of diffusion of calcium through and precipitation of calcite within the sandstone containing them after being deeply buried. The carbon and calcium comprising these concretions came either from marine limestone, shells, anhydrite, or some combination of these in addition to bicarbonate derived from oxidized methane from strata outside of, but hydrologically connected to, the Dakota Sandstone. After the formation of the concretions, differential erosion of the considerably softer sandstone surrounding them exposed as free-standing boulders. [8]

See also

Other rock formations in Kansas:

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<span class="mw-page-title-main">Graneros Shale</span> Geological formation

The Graneros Shale is a geologic formation in the United States identified in the Great Plains as well as New Mexico that dates to the Cenomanian Age of the Cretaceous Period. It is defined as the finely sandy argillaceous or clayey near-shore/marginal-marine shale that lies above the older, non-marine Dakota sand and mud, but below the younger, chalky open-marine shale of the Greenhorn. This definition was made in Colorado by G. K. Gilbert and has been adopted in other states that use Gilbert's division of the Benton's shales into Carlile, Greenhorn, and Graneros. These states include Kansas, Texas, Oklahoma, Nebraska, and New Mexico as well as corners of Minnesota and Iowa. North Dakota, South Dakota, Wyoming, and Montana have somewhat different usages — in particular, north and west of the Black Hills, the same rock and fossil layer is named Belle Fourche Shale.

<span class="mw-page-title-main">Valentine Formation</span> Geological formation in midwestern US

The Valentine Formation is a geologic unit formation or member within the Ogallala unit in northcentral Nebraska near the South Dakota border. It preserves fossils dating to the Miocene epoch of the Neogene period and is particularly noted for Canid fossils. This unit consists of loosely-consolidated sandstone that crumbles easily. These sands carry the water of the Ogallala Aquifer and is the source of much of the water in the Niobrara River. A particular feature of the Valentine is lenticular beds of green-gray opaline sandstone that can be identified in other states, including South Dakota, Nebraska, Kansas, and Colorado. Although three mammalian fauna stages can be mapped throughout the range of the Ogallala, no beddings of the Ogallala are mappable and all attempts of formally applying the Valentine name to any mappable lithology beyond the type location have been abandoned. Even so, opaline sandstone has been used to refer to this green-gray opalized conglomerate sandstone that is widely found in the lower Ogallala Formation.

<span class="mw-page-title-main">Tesuque Formation</span> Geologic formation in New Mexico, United States

The Tesuque Formation is a geologic formation in north-central New Mexico, United States. The formation provides an unusually complete record of the evolution of mammals during the Miocene epoch.

<span class="mw-page-title-main">Fencepost limestone</span>

Fencepost limestone, Post Rock limestone, or Stone Post is a stone bed in the Great Plains notable for its historic use as fencing and construction material in north-central Kansas resulting in unique cultural expression. The source of this stone is the topmost layer of the Greenhorn Limestone formation. It is a regional marker bed as well as a valued construction material of the late 19th and early 20th centuries in Kansas. This stone was very suitable for early construction in treeless settlements and it adds a notable rust orange tint to the region's many historic stone buildings. But the most famous use is seen in the countless miles of stone posts lining country roads and highways. This status gives rise to such regional appellations as Stone Post Country, Post Rock Scenic Byway, and The Post Rock Capital of Kansas. This rustic quality finds Fencepost limestone still used in Kansas landscaping today.

References

  1. "Rock City". Geographic Names Information System . United States Geological Survey, United States Department of the Interior.
  2. Bell, W.T., 1901, The remarkable concretions of Ottawa County, Kansas, American Journal of Science, 4th Series, v. 11, p. 315-316.
  3. Gould, C.N., 1901, The Dakota Cretaceous of Kansas and Nebraska, Kansas Academy of Science, v. 17, p. 122-178.
  4. Landes, K.K., 1935, Scenic Kansas, Geological Survey of Kansas Bulletin, n. 36, 55 p.
  5. 1 2 3 Shaffer, H.L., 1937, Concretions in the Dakota Sandstone, Compass, v. 17, p. 87-90.
  6. Ward, H.K., 1938, Concretions of Rock City. Mineralogist, v. 6, p. 23-24.
  7. Swineford, Ada (1947). Cemented sandstones of the Dakota and Kiowa formations in Kansas. Geological Survey of Kansas Bulletin. OCLC   5051056.
  8. 1 2 3 4 5 6 7 McBride, Earle F; Milliken, Kitty L (2006). "Giant calcite-cemented concretions, Dakota Formation, central Kansas, USA". Sedimentology. 53 (5): 1161–79. doi:10.1111/j.1365-3091.2006.00813.x.
  9. McBride, E. F; Picard, M. D; Milliken, K. L (2003). "Calcite-Cemented Concretions in Cretaceous Sandstone, Wyoming and Utah, U.S.A". Journal of Sedimentary Research. 73 (3): 462–83. doi:10.1306/111602730462.