Michael Lewis | ES 546 | December 2009
Cheyenne Bottoms is an ovoid depression in Central Kansas comprising more than 100 square kilometers in Barton County. The north and south basin walls rise about 30 meters from the basin floor and are comprised of Cretaceous Dakota Formation sandstone and Greenhorn Limestone. The northwest wall features both inlets through the exposed bedrock. The basin is superficially endorheic with two streams bringing water into the basin in an inland delta pattern supplying intermittent water to the saline marsh within the basin; a manmade channel has been cut into the Cheyenne Creek channel to move excess water out of the basin. However water also leaves the basin though subsurface seeping through alluvial deposits on the eastern and southeastern sides of the basin (Bayne, 1976). The northeast is composed of Quaternary dune sand about 12 meters in height, common in this area of the Arkansas River Valley.
Figure 1 Kansas Geological Survey map of Barton County, Kansas and Cheyenne Bottoms
The Arkansas River bends abruptly to the South East from its northeasterly direction south of Cheyenne Bottoms. The local region has many set dunes with sands source likely originating in the northward lateral movement and stream capture of the Arkansas River across the river valley. The region was subject to marine inundation repeatedly, most recently at the end of the cretaceous, and which laid down great amounts of shale and limestone, followed by dry periods in which erosion was the dominate action. Much of the sand in central Kansas is the remnants of the Cretaceous deposition in the area. As the Arkansas River moved northward, the fluvial energy scoured away the deposits and left copious amounts of sand behind to be picked up by the wind. Today most of that sand has been fixed but in drier periods or through overuse by humans and animals that sand can and recently has been relatively unbound and freely migrated through the region.
Identifying the geomorphologic origins of this feature has been difficult. The most striking feature of this landform is its oval shape. So perhaps looking at the origin of other oval depressions will shed some new light on the origin of Cheyenne Bottoms.
(United Stated Geological Survey)
This landform consists of a plethora of oval depressions stretching along the eastern Coastal Plain from New Jersey to Florida with similar structures stretching westward to Texas. These depressions, ranging in length from several miles to a couple hundred feet, are generally shallow, often overlapping, with an axis running northwest-southeast. The depressions are generally deeper to the Southeast of the center and are deeper with greater size. The shape of these depressions vary with smaller depressions being more rounded while larger depressions become more oval with increasing size.
Figure 2 Carolina Bays in Bladen County, North Carolina from Landsat 5 composite. (United Stated Geological Survey)
In Virginia the Carolina Bay formations are formed in upland gravel areas of the coastal plain, with the basin floors being 345-360 feet above sea level. (Goodwin & Johnson, 1970) Rims are present and most well developed on the South and east sides of the depressions. These streams are often endorheic in nature with only a few being breached by streams or drainage. Elsewhere along the coastal plain the features are found on the coastal plain right up to the barrier dunes and most common to river plains.
The bays of Virginia sit on a gravel base but are composed primarily of sand with some pebbles while moving into the interior of the structure the sand begins to give way to silty clays which become the dominate element within 200 feet of the rim. (Goodwin & Johnson, 1970)
The bays have not been seen on the piedmont or on the heavily eroded coastal region but have been found in gravels over a wide variety of bedrock in the upland coastal region so it is not thought to be a geomorphologic origin associated with any particular bedrock.
Aging of the bays by Ivester et al. using optically stimulated luminescence suggest multiple periods of activity with rims of different ages on the same feature developing over thousands of years. Ages range from 15 ka BP to 80 ka BP and older (Ivester, 2004).
Figure 3 Ovoid depression lakes in South Africa about 200mi. from the ocean. Image from Google Earth 2009.
Carolina Bays are not a landform unique to the southeastern US though. The same oriented lakes are found in Western Australia near Perth and in South Africa. The landform is also common throughout the tundra but the origins there are likely related to thermokarst conditions.
Origin theories are numerous, here I will briefly expound upon the most popular. One of the most popular is extraterrestrial in origin. Second is erosion, through either aeolian or marine means. Periglacial mechanisms could also account for the similarity of the area to some of today’s tundra regions. Another theory is one of subsidence while the final tries to link the Carolina Bays to maar lakes due to their similarity in appearance.
Extraterrestrial origin theories often cite the similar orientation and overlap, as well as the carbon spherical concentrations in the bay fill as evidence of a meteoric impact. However, no shocked quartz, ejecta flap, or meteoric remains have been found to date. The stratigraphy underneath the bay features appear to be intact. Eyton and Parkhurst (Eyton & Parkhurst, 1975)suggest an overhead explosion of an icy comet, much like the Tunguska event. Another idea is that an impactor hit the Great Lakes region during glaciations and ice was ejected to the Eastern Coast to form the Carolina Bay structures. The resulting destabilization may have initiated the Younger Dryas cooling 12.9 ka (Firestone, et al., 2007). A second team was unable to corroborate the findings of Firestone et al however when their analysis of materials within the bays were not conclusively able to locate the impact markers of an impact event (Surovell, et al., 2009)
If the bays were from
a single event we should find that the lowest layers of sediment should be
similar in age. We would also need to identify why this feature is found from
New Jersey to Texas and with orientation not pointing to a single location. We
also do not find a radiating pattern in Chrissiesmeer, South Africa or
Mariginiup, Western Australia where these oriented oval lakes also occur. Another
problem with the idea of impact creation is the rims of smaller crater
overlapping or inside larger craters. In an impact, craters build their rims on
top of the surface below where they hit, the result is a wave pattern of
addition, Carolina Bays do not exhibit this pattern, internal and external rims
share the same internal base without additive effects. Some of this
may be caused by added settling of debris and sediment within the basins
removing traces of impacts resulting in a rim lower than the present basin
Figure 4 (Savage, 1903)
What is true for the Carolina Bays would also hold true for Cheyenne Bottoms but again, there is no disturbance to the stratigraphy to suggest an impact nor associated impact rocks. No meteor remnants have been found nor has the water table showed the disturbances common at other impact sites.
and Lacustrine Erosion
H. N. Fisk suggested a fluvial origin to the depressions that would become these rounded depressions. He suggested the thalwegs of abandoned Pleistocene channels were blown out by wind erosion (Aronow). He also suggests these depressions were kept active through animal action as they were used as a wallow keeping the depression disturbed. The origin of the rim feature seems unclear however. Many who have studied the Texan iterations of this landform have suggested that these low rims are caused by windblown sand being captured by grass and plant growth on the depression rim building up a small ridge around the depression over time (Aronow). This solution does seem possible as the lack of free roaming ungulates would not enable wallows to be continually disturbed but I would expect variation in the origin dates of these features.
On a variation of Fisk’s idea, Kaczorowski, in 1976, followed up on an earlier theory that lakes formed the original depression and were worked into their alignment and shape by prevailing winds driving wave action on the shores.
Plenty of alluvial deposits exist south of Cheyenne Bottoms from the migrating Arkansas River. This could have been the tool used to scour out a depression from a remnant thalweg depression of an ancient river. Blood and Deception creeks have deeply eroded the sandstone through the basin wall and formerly flowed on through the Little Cheyenne Creek exit channel towards the Arkansas. Given their age and persistence the ancestor of these creeks likely may have been the origin of the depression scoured into Cheyenne Bottoms. In “Physiography of Western Kansas, (Haworth, 1897)” Eramus Haworth describes an ancient channel carving back through the Cheyenne depression as a waterfall and then being blocked by aeolian deposits of alluvium, both by its own and that of the Arkansas Rivers.
Figure 5 Geologic cross section of Cheyenne Bottoms (Latta, 1950)
It is likely these creeks did indeed form the headwaters of an ancient channel that flowed over an elevated cuesta with a southern exposure over the Arkansas Valley, the face of which the river ran parallel to. Pulling the falls back would (Kansas Geological Survey)reveal two faces inside the valley as well as the remaining face over the Arkansas River. When the alluvium cuts off stream flow, sand would scour the walls during dry periods while periodic flooding and wave action would continue to erode the walls into smoothly rounded concave ovoids.
This theory seems plausible but it is uncommon to find a landscape in a relatively moist environment, subject to flooding and unable to develop an outflow. The only plausible case for such a situation is active sedimentation and deposit to prevent an escape channel developing. Sediment load can easily be dropped in a widened valley and the area is known as a dormant dune sea, these two factors seemed to have coincided to produce the active blocking of an escape channel from the depression. Catastrophic flooding never built up to clear the channel because underground movement continued to move water out of the depression.
Aronow reports many karst or solutional depressions have formed in areas that lack traditionally associated karst rock. Decaying plant mater acidifies water which in turn dissolves out hydrated iron oxides and clay minerals. Clay mineral kaolinite AL2Si2O5(OH)4 can have its silica component dissolved in this manner with the forming gibbsite precipitate of Al(OH)3 representing a 35% volume loss.
While this seems to be a possible explanation for subsidence, kaolinite assemblages, not gibbsite, seem to make-up the Carolina Bay features and show little alteration since deposition. In fact the clay makeup is similar to the surrounding materials at the same elevation suggesting the material was blown or washed in. (Ingram, Robinson, & Odum, 1959)
Figure 6 (Walters, 1978)
Cheyenne Bottoms sits over the Hutchison salt member, an ideal source of subsidence. However, subsurface date do not demonstrate subsidence as being a primary cause of this deformation. Comparing Tet well 17-12-29dd, on the slope of the Cheyenne Bottoms rim to 18-12-4bb inside the Cheyenne Bottoms depression, the Kiowa shale formation to remain at a consistent depth. If subsidence were a major cause of deformation, the deformation should be mimicked throughout all layers of the stratigraphy down to the dissolving member. This is not what is found, furthermore salt layer mapping, while showing a slight thinning under Cheyenne Bottoms does not meet the requisite size or volume of dissolution to show considerable transference of character to the surface.
Dissolution of nontraditional karst materials are also a possibility given the clay streaking and iron nodules identified in test wells. Anodic dissolution of iron silicates are a possibility in this situation but given the large volume of depression and the relative paucity of dissolvable materials, while this may in fact be occurring, it is likely not the cause of major deformation and only a minor secondary process.
Figure 7 Further Values include an elevation of 1,654 feet for the beginning of the Kiowa Shale in Rice County in well 18-10-31cc, elevation 1,760 feet & 1,631 feet elevation for Kiowa Shale for well 18-11-36aa at 1,749 feet in Eastern Barton Co. at the Rice County line. Data from KGS (Latta, 1950)
Piping is the erosion activity of water in weakened or available flow paths below the surface. This can occur in a situation where for example an animal burrow lies in a path that promotes water movement during flooding episodes. The water continues to erode headward elongating and enlarging the pipe. Not only does the pipe create a structural cavity but it also promotes the escape of fine materials from the drained location, eventually this area will collapse creating localized false karst topography. This type of formation is common to swelling clays, most commonly, bentonite, illite, and montmorillonite. (Parker) While piping is usually associated with dry regions, it can be a factor in humid areas and may have played a role in the origin of the Caroline Bays. (Aronow)
Cheyenne Bottoms was likely formed by the action of an ancient ancestor to Blood and Deception creek. This ancestral stream left alluvium in its former channel that is still being used as a route of subsurface evacuation by the waters of Cheyenne Bottoms. The deepest portions of the depression lie closest to this exit due to continued illuviation and escape of sediment and water through this ancient channel.
The multiple ovoids of the Carolina Bays and the massive ovoid of Cheyenne Bottoms likely share a common aeolian past. Persistent coastal winds on the alluvial beachheads and river valleys of the coast were likely enlarged through scouring of fluvial or lacustrian action as Cheyenne Bottoms we scoured by the strong winds driving from the northern periglacial regions of the Quaternary to the warmer temperate forest and grasslands of the Gulf of Mexico. The alluvium of the historical channel was the medium upon which this depression was built and the source of the sand dunes to the East of Cheyenne Bottoms. As periods of alternating moisture and dryness passed, the basin was scoured and experienced some isostatic depression further enlarging capacity and initiating some slight structural deformation. The former channel of the ancient river has continued to serve as an exit for the waters of Cheyenne Bottoms slowing pulling water through the alluvium in a capillary action, taking silt and fine sediment with it and over time, further clearing the southeastern portion of the Bottoms that today hold the deepest portions of the basin.
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