Cottonwood Limestone

located in Cottonwood Falls, Kansas, is an example of the many landmark buildings within the Flint Hills that are constructed of Cottonwood Limestone. While many other limestone formations are found in the region and have been widely used in local construction, most (excepting most notably the Fort Riley Limestone) weather poorly, lie with much thinner parting beds, or are generally much higher in the typical Permian silica or flint content and so are much more difficult to cut or sculpt. the latter showing a whiter face with smoother glass-like fracture in contrast to the more buff-colored Cottonwood Limestone showing a rougher earthy fracture. The Cottonwood is the main facing material for the campus buildings of Kansas State University. as well as much of the Kansas State Capitol in Topeka, Kansas are constructed with Cottonwood Limestone. The iconic Campanile in Lawrence, Kansas, is also built from the once-named “Manhattan stone”. Cottonwood Limestone continues to be popular in constructions, and was recently (2014) used to construct the West Side Stadium Center of the Bill Snyder Family Football Stadium. Sculpture The massive, fine-grained, bright-white character of this limestone makes it a practical stone for large sculptures: • Dyche Hall Grotesques, University of Kansas, Sculptors: Joseph Robaldo Frazee and Vitruvius Frazee • Prairie Passage, Lyon County Fair Grounds, Emporia, Kansas, Sculptors: 1992 Kansas Sculptors Association Team Carve • Tonantzin, Elder Center, Prairie Band of Potawatomi Nation Reservation, Sculptors: James Wahwassuck Aquifer . The Cottonwood is a reliable surface limestone aquifer in the region. The brush line seen on many hillsides at the base of this member indicates the moisture it provides. Many springs issue from beneath the massive ledge, especially the west-facing exposures—many of which serve as a source of water for livestock. In many places, springs or shallow wells from the Cottonwood provide large supplies of water for domestic home and farm use. This is especially true along westward-facing hillsides, as strata generally dip to the northwest. == Distribution ==

As the prominent member of the Beattie Limestone formation, Cottonwood Limestone can be traced on the outcrop from Nemaha County, Nebraska, southward to Osage County, Oklahoma, and followed in the subsurface westward to the vicinity of the Colorado-Kansas line as well as into northwestern Oklahoma. The surface outcropping of the Cottonwood Limestone is easily traced in the Flint Hills south of the Kansas River and east of Manhattan, Kansas. In Manhattan, it forms the scenic ridges surrounding the old downtown in the southeast of the city. From there, the line of outcrop is a tortuous one extending several miles north and west along the Kansas and Big Blue rivers and their tributaries. This limestone forms extensive outcrops in the Cottonwood River valley that shares its name; outcrops can be followed several miles up every tributary valley around Cottonwood Falls. == Lithologic character and thickness ==

highway in west Manhattan, Kansas, showing the yellowish-gray or buff of fresh fractures. Just visible is the subtle variations in color, texture, and siliceous nodules between the upper and lower ledges . Note the visible line of parting between the top and bottom "ledges", and the subtle change in tone and texture. on K-113; showing the white to gray weathering and a history of subterranean dissolution along joints, highlighting the more resistant siliceous nodules. The Cottonwood Limestone is a marine limestone and calcareous shale, laterally persistent, bench-forming, and notably and consistently showing abundant fossils. An outstanding example of uniformity of thickness over considerable areas, the outcrop of the Cottonwood Limestone over a distance of 150 miles from Nebraska to central Kansas is nowhere less than 5.5 nor more than 6.5 feet. which commonly part when weathered. This boundary between the upper and lower Cottonwood is evidenced by a sharp textural contrast, porosity difference, and changes in the opaque mineral content. but the Top Ledge has a yellower tint or a creamy gray with open grain while the Bottom Ledge is whiter with tight grain. With respect to fossil content, the upper weathering bed is characterized by the abundant Fusulinid assemblage, while the lower bed is composed of minute particles of various fragmented fossils, especially Osagia, echinoderms, and bryozoans. Fusulinids are common, especially in the upper part, and siliceous nodules project from weathered surfaces. Close observation removes any likelihood of confusing the Cottonwood Limestone with any other layer in this part of Kansas; its distinguishing characters are the massive ledge of uniform thickness, the silicified nodules, and the abundance of fusulinids, chiefly in the resistant upper part. The Cottonwood is not a flinty limestone such as those seen higher on the surrounding hilltops; however, nodules, concretions, and trace fossils (filled-in burrows) of partly to fully silicified material that weather more slowly than the rest of the member can give the limestone an appearance of containing flint. south of Chase County, Kansas the member has lost its massive limestone characteristic and does not form the conspicuous outcrops seen farther north. In Greenwood County, Kansas, the unit appears as light-gray limestone crowded with horizontal thin leaves of platy algae, attaining a maximum observed thickness of 8 feet. The Cottonwood in southern Kansas and northern Oklahoma is an interbedded limestone and calcareous shale with a very diverse, abundant, and well-preserved fossil fauna, especially brachiopods, mollusks, and ammodiscid foraminifera (shelly facies). At the southern limit of its outcrop the Cottonwood Limestone is a medium crystalline limestone with thin, shelly layers. Mollusks, Osagia, and quartz silt are common (silty Osagia facies). == Paleoenvironment ==

Variations in the characteristic content and texture (facies) of the limestone reflect lateral changes in the environment from north to south. • The northern and central bioclastic and fusuline facies of the Cottonwood were deposited in shallow, well-lit, moderately turbulent waters having only very small amounts of material washed in from land. Water circulation was variably restricted. Large amounts of sand-sized to granule-sized fusulinids, identified as Schwagerina are preserved, especially in the upper bed; Schubertella fusulinids are more common in the lower bed. Few animal fossils are present in the upper bed but somewhat more frequent in the lower bead, usually fragments or debris, including echinoderms, bryozoans, trilobites, ostracods, crinoids and occasional gastropods. • Separating the central and the southern provinces was a broad shoal where the platy algal facies was deposited; here waters were moderately turbulent, well-lit, shallow, and somewhat restricted in circulation. • The southern shelly ranges were deposited in a less turbulent and deeper-water environment, having good circulation and relatively large amounts of land-sourced material entering from the south supporting mollusks and sessile, filter-feeding brachiopods. The Osagia, an algal-foraminiferal intergrowth, and other encrusting algae beds in Oklahoma was formed in a shallower, more turbulent, nearer-shore environment marginal to the shelly facies. == Access and viewing ==

. Seen here is a very weathered outcrop just above the landmark MANHATTAN letters. The Cottonwood Limestone is easily accessed or viewed in several locations: • On the Konza Prairie Nature Trail, as one climbs the trail from Kings Creek, the member forms the second bench. Here can be witnessed the characteristic line of boulders and shrubs that follow the rock layer around the hills. The characteristic springs can be found elsewhere on the trail feeding into Kings Creek. • This limestone caps the landmark Bluemont Hill in Manhattan, Kansas, just above the white MANHATTAN letters. that is characteristic of the surface sedimentary formations in the region. Near the dam, the layer is some 40 feet above the usual lake level, but from there it can be seen to very slowly slope below the water miles to the northwest. == See also ==