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). |
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Seismic data taken from the south-east corner of the basin.
Seismic data modified from Keiswetter et al. (1995) |
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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.
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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.
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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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