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Geologic History of Cheyenne Bottoms

 

The geology of Cheyenne Bottoms has lead to much debate. The genesis of the Bottoms is one of the last unsolved physiographical problems in Kansas. There are four major theories that should be considered: salt subsidence, structural movement, Pleistocene drainage stream capture, and scouring and damming by deposits of sand at the south-eastern margin. Although the most widely accepted theory attributed to the formation of the large basin is dissolution of subterranean salt beds, all the theories are in part are responsible to the regional physiography.


Salt Dissolution
The theory of salt dissolution and subsidence is the most supported theory for the genesis of the Bottoms (Johnson, 1901; Bass, 1926; Latta, 1950; Keiswetter et al., 1995). Only the Hutchinson salt member of the Wellington Formation is thick enough to support the amount of dissolution necessary to cause Cheyenne Bottoms. These subterranean salt deposits would be leached out from ground water causing the large subsidence. Two oval trends seen in the false collar composite from change in vegetation show elliptical sink holes which are remnant of the salt dissolution. If both are attributed to salt dissolution then the larger oval trend would have occurred first. The second smaller oval trends in different orientation and is centered around the lowest portion of the basin at the State Wildlife Preserve. Keiswetter et al., (1995) also showed through ground penetrating radar (GPR) that there is thinning of the Hutchinson salt member below the south-eastern edge of the Wildlife Refuge.


False Color Composite 2001 Landsat TM 257 imagery of Cheyenne Bottoms. There are two elliptical oval shapes which are controlled by topography and vegetation. Depression 1 is the basin-proper and Depression 2 immediately around Wildlife Preserve apears to be another land-sink. Image taken from Aber and Pavri (2003).

Seismic data taken from the south-east corner of the basin. Seismic data modified from Keiswetter et al. (1995)
Detail and interpretation of seismic data at the Hutchinson formation. As the profile gets closer to the basin, the salt formation thins. Seismic data modified from Keiswetter et al. (1995).


Structural Movement
The structural subsidence theory was advanced by Bayne (1977). He noted through detailed subsurface structural contouring that formations bellow the Hutchinson Salt member also subsided. He attributed the formation of the bottoms sink hole to structural movement. Bayne showed that the Precambrian surface below the Bottom’s is a structural low and that the Heebner Shale of the Oread Limeston exhibited a basin which was evidence of deeper subsidence below the Wellington Formation. The timing of the structural movement Bayne showed was between early Late Cretaceous time and latest Pliocene time. This corresponds to the same period as the Kimberlites in Riley County and the intrusive rocks in Woodson County.


Structural contour map of the Winfield Limestone Base. This unit is 250 feet below the base of the Hutchinson Salt Member and yet shows a developed basin under the current Cheyenne Bottoms. Modified from Bayne (1977).

Pleistocene Drainage
The theory that involves the Pleistocene drainage in the area is more complicated and background information must be presented to understand this theory. In the vicinity of Galatia, Kansas, north-west of the Bottoms, there is deposits of alluvium with thicknesses of 10 to 40 feet (Latta, 1950). These deposits rest along the upland drainage divide between the Bottoms and the Lower Smoky Hill River and have an elongated trend northwest to southeast. This is a remnant terrace deposit of the ancestral stream that flowed in a direction similar to the current Blood Creek. It is this paleo-river system which eroded the Cretaceous bedrock and cut the large plain and valley associated with the Bottoms.


Ground water contouring (Latta, 1950) as well as bedrock surface mapping (Bayne, 1977) shows a buried river valley through the center of Cheyenne Bottoms (See geologic map). The ancestral Upper Smoky Hill River flowed across the “Galatia Channel” (Latta, 1950) and entered Cheyenne Bottoms. After the stream flowed through the Bottoms it joined the “Chase Channel” (Fent, 1950) flowing through Rice County and into the north south master stream in Sedgwick County known as the “McPherson Channel”. Bayne and Fent (1963) gave the age of the stream capture, to which the course of the Smoky Hill River currently flows, to the early Kansan Stage of the Pleistocene. They attributed this headward erosion of the Smoky Hill River to a change to wetter climate with the accumulation of Kansan Ice.


Map of Kansas showing the Upper Smoky Hills River drainage basin. The whole area from zone 1 highlighted in red at one time flowed through Chyenne Bottoms.  Modified from Bayne and Fent (1963).

Once the large supply of sediment and water was cut off from the Bottoms, the basin started to sediment in. There was no longer a perennial source of water to move sediment out of the relatively flat basin. Sedimentation of the Bottoms thus became controlled by storm deposits as it is today. Once the buried valley sedimented in, the sheet flow sedimentation and flooding added more sediment layers and alternating paleosols. This is verified through coring analysis where periods of alternating wet and dry climates were seen. This theory is explained in a non-technical format by Zimmerman (1990, 19).


Sand Dunes
There are deposits of sand dunes located at the eastern margin of the basin (See geologic map). The source depression of these deposits is the Bottoms. After the stream capture of the Upper Smoky Hills River, there was an insufficient volume of water to fill the previous channels. This previous high capacity channel now dried up and allowed sand dunes to mobilize sediment to the east of the channel, the same direction of the trade winds. Another hypothesis states that these dunes scoured the basin during a hypsithermal event, however the basin is mostly made up of fine grained material which differs from the dune texture. The age of the dune field is unknown  (Fredlund, 1995) and there is need for further investigations.


Acording to Miller (Haworth, 1897, p. 313) it was the sand dunes that blocked the down stream channels of Blood and Deception Creeks. He attributed the formation of the Bottoms to stream erosion. When the creeks incised through the harder Dakota sandstone, it hit the softer shale and eroded quickly until it contacted lower limestones and created large flood plains in which sand deposits mobilized and then blocked the lower channels over time. Through winnowing of water the finer sediment filled the Bottoms as it contacted the sand dune dam.


 

 

 

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© S.W. Salley (2004). All rights reserved. All illustrations and ideas presented in this paper are intellectual
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