An Analysis of Theories Describing the Geomorphology of the Cheyenne Bottoms

Final Project Team Report by G. Alex Sill and Thomas A. Woolman

ES546 - Field Geomorphology, Emporia State University

Fall Semester, 2013


Contents

Introduction | Modern Surface | Subsurface History | Proposed Causes of the Cheyenne Bottoms Formation
The Salt Dissolution Theory | The Subsurface Structural Contouring Theory
The Sand Dunes Erosional Blockage Formation Theory
The Meteorite Impact Theory | Analysis and Conclusions | References

Introduction

The Cheyenne Bottoms is a wetland environment measuring approximately 166 km2, and is generally considered to be the largest wetland environment in the continental United States. It is located approximately midway between the towns of Hoisington and Great Bend in the state of Kansas (Kansas State Wildlife Areas Map, 2013).

The wetland environment consists of a natural basin that was created by an unknown geomorphic process or processes, none of which are entirely understood at present despite significant research beginning over a century ago with Haworth (1897). This paper will attempt to analyze the leading theories related to the geology and geomorphology of this feature and endorse or reject aspects of these hypotheses based on observation and scrutiny of supporting data.


Figure 1: Location of Barton County Kansas and Cheyenne Bottoms Wildlife Area (from www.bartoncounty.org).


Figure 2: Landsat 8 dataset of Cheyenne Bottoms region acquired 29 AUG 2013,
naturalistic false-color composite image generated by T. Woolman with Idrisi Selva
utilizing Bands 2, 3 and 7 (blue-green, green and mid-infrared).



Modern Surface

Cheyenne Bottoms in Barton County Kansas (figure 1) is a large oval depression about 166 km2 (64 square miles). The depression is an area of ongoing sedimentation by both fluvial and eolian processes. Canals bearing sediments in their waters feed the basin from the west and north. Several smaller natural streams feed into the region forming a distinctly radial drainage pattern. The area is currently managed as a wetland environment for migratory birds, and is therefore a marsh (see figure 3), with standing water in all years having normal rainfall. Removing the water would reveal a land surface that tilts slightly eastward. Limestone, or sandstone and clay, form steep bluffs that contain the basin on three sides (figure 2).


Figure 3: Geological map of Cheyenne Bottoms showing fringe of marshland surrounding a flooded central area
(geological map from ref: Latta, Bruce F. 1950. Geology and Ground-Water Resources of Barton and Stafford Counties,
Kansas. KGS Bulletin 88. Taken from Plate 1.).

Figure 3 Legend: Breakdown of geophysical components within the geological
map shown in Figure 3, (Latta, 1950).


Figure 4: View southward from the escarpment that retains the Cheyenne Bottoms on the north.
The south escarpment is visible along the horizon. Professor Aber is seen taking photographs. Photo by G. Alex Sill 2013.

These are areas of erosion and are acted on by both fluvial and eolian processes. The east and southeast margin of the basin is confined by gently undulating dune sand constantly eroded and redeposited by prevailing winds. The drainage divide between the Cheyenne Bottoms and the Arkansas Valley to the south of the basin is comprised of the Dakota Formation (at depth), and overlain by impervious Pleistocene silt of the Sanborn Formation (Merriam, 1962; Bayne, 1977). “On the north, west, and south sides the basin walls are Cretaceous rocks which rise to an elevation above the basin floor of more than 100 feet in a distance of about one mile. On the northeast side, sand dunes rise to an elevation of about 100 feet above the basin floor. The east and southeast sides of the basin are comprised of alluvial deposits which rise 30 to 40 feet above the floor of the basin.” (Bayne, 1976). Surface water flow into the basin is largely provided by seasonal flow from Blood Creek and Deception Creek, from the northeastern section of the formation. “The basin is developed in lower Cretaceous bedrock overlying upper Permian salt-bearing strata. Structural movement (faults) and subsurface salt solution are possible causes for subsidence of the basin, and wind erosion may have further scoured the basin. The sedimentary record of Cheyenne Bottoms encompasses the past 100,000 years (Zimmerman 1990).” (Aber, J.S. accessed online 2013).




Subsurface History

The Precambrian surface of the Cheyenne Bottoms area displayed a flat lowland plain with isolated hills that stood up to 30m (100 ft) above the surrounding landscape (figure 5). See Figure 5A below for how this subsurface map ties to the CB region.

Figure 5A: Structure contour map of the Precambrian basement at Cheyenne Bottoms.
Contour interval is in feet below modern surface. Taken from Bayne (1977).

Figure 5B: Composite inset map showing how Figure 5 above fits into the CB region.
Topographic map from the U.S. Bureau of Land Management, accessed online 3 December 2013.
Composite map image created by G. Alex Sill, 2013.

Many episodes of submergence and subsidence occurred during the Paleozoic in which the sediments accumulated during submergence intervals (transgression) were either completely or mostly eroded away during subsidence intervals (regression). Formation of the Ellis Arch occurred prior to sedimentation during the Mississippian. This anticline formed an axis striking northwest-southeast due to upward warping of pre-Mississippian sediments. The rise of this structure invigorated erosion in the region, which led to erosion of most rocks that had buried the Precambrian hills. Today, the oldest rocks sitting on the buried Precambrian hills are Pennsylvanian rocks of the Kansas City Group (Merriam, 1963; Bayne, 1977).

Following this lengthy period of erosion, the region remained submerged for much of the rest of the Pennsylvanian and through the Early Permian. The continental red beds were deposited during this time. However, much of this red bed sediment was lost to erosion during the Triassic, Jurassic and early parts of the Cretaceous. From the early Cretaceous to the late Cretaceous, the Cheyenne Sandstone (a peripheral beach to a vast inland sea), Kiowa Formation and Dakota Formation were deposited during another long period of transgression. The sea finally receded at the end of the Cretaceous and the region has not been submerged by the sea since (Bayne, 1977).

The Paleogene and Neogene Periods were times of erosion, although the Ogallala Formation was deposited during the Pliocene Epoch of the late Neogene. Stream capture and resulting northward migration of the Arkansas River occurred in Pleistocene time. The same processes have been affecting the region throughout the remainder of the Pleistocene and into the Holocene (Bayne, 1977).




Proposed Causes of the Cheyenne Bottoms Formation

The genesis of Cheyenne Bottoms (CB) has a number of conflicting theories of formation, some of which are more plausible than others but also containing greatly varying levels supporting evidence. “Haworth (1897) was the first to write on the origin of Cheyenne Bottoms and attributed the feature to stream erosion. Johnson (1901) advanced the theory that Cheyenne Bottoms was a basin of subsidence caused by removal of soluble masses of salt within the underlying rock. He noted that the gap in the rock wall on the southeast side of the basin did not favor this theory of origin. Bass (1926) prepared a map of salt thickness in western Kansas that shows thinning of the salt beds beneath Cheyenne Bottoms. He (Bass, 1926) believed that this tended to confirm Johnson's theory of salt solution as the cause of the basin-like feature. Latta (1950) indicated that salt solution and subsidence may have been in part responsible for the feature, but also indicated that stream erosion during the Pleistocene played an important part in its origin and present configuration.” (Bayne, 1976)

Currently there are four main hypotheses concerning the formation of the modern feature called Cheyenne Bottoms. The primary CB formation theories are outlined below.




1. The Salt Dissolution Theory

At the time of Charles K. Bayne's publication of "Geology and Structure of Cheyenne Bottoms Barton County, Kansas" (1977) there were only two ideas that had been put forward possibly explaining the formation of this depression. Bayne's (1977) analysis of test holes drilled by Bruce F. Latta (1950) indicate that features in the shallow subsurface are apparent, but much more pronounced at deeper depths. This observation is good fodder for a salt solution and subsidence mechanism for the formation of the depression since conspicuous features at great depth become obtuse as they are translated upward in the rock sequence (Merriam, 2005) There is indeed a local evaporite deposit known as the Hutchison Salt member of the Wellington Formation (Latta, 1950). It is possible that groundwater was able to penetrate a localized region of this deposit, dissolve the salt, and transport it out of the area. Doing so would leave a void in the subsurface that would eventually be translated upward to the surface as the overlying sediment drooped downward to fill the void (Merriam, 2005).

By applying the principle of superposition and cross-cutting relationships to structure contour diagrams constructed by Bayne (1977), one would assume that no sediments below the Hutchinson Salt would be affected by a collapse triggered by removal of the salt. The structure contour maps, however, show that sediments beneath the Hutchinson Salt also feature a depression (figures 6 and 7). Therefore, the surface depression is not purely a result of a dissolved salt body in the subsurface.

Figure 6: Structure contour map of Cheyenne Bottoms showing the surface directly below the Hutchinson Salt member. Taken from Bayne (1977).


Figure 7: Structure contour of Cheyenne Bottoms showing the top surface of the Hutchinson Salt. Taken from Bayne (1977).

Additionally, the Hutchinson Salt is a widespread deposit with similar overlying sediment types and drainage regimes across large areas. There are no other similar features in the area that share the distinct surface morphology of Cheyenne Bottoms. If it is indeed a depression caused by subsurface salt dissolution, then other similar features would likely be expressed in the landscape.




2. The Subsurface Structural Contouring Theory (Precambrian Surface Contouring, due to Structural Movement)

Bayne (1977) was able to largely dispel any thought of the Cheyenne Bottoms depression being the sole result of a deeply buried void caused by a dissolved salt body. His structure contour maps of the subsurface (figures 5, 6, 7 and 8) clearly show a depression in the area of T18S R12W that persists from the surface to the Precambrian basement becoming more conspicuous going deeper.

It has been hypothesized that the initial depression in rocks above the Precambrian was formed due to structural movement at greater depth in a manner described by Merriam (2005). Bayne's structure maps (1977) clearly show movement above and below the Hutchinson Salt.

The law of cross-cutting relationships dictates that no structural movement that exists in a rock unit could have occurred prior to the deposition of the affected rock unit. Therefore, the Cheyenne Bottoms was formed by structural movement that occurred after the deposition of the Stone Corral formation (Bayne, 1977). Further analysis of the geologic map (figure 3) shows that the Greenhorn Limestone is affected by structural movement, and therefore the movement occurred after its deposition. The structure contour map of the top bedrock surface (figure 9) shows that surface is also affected. The erosion of this surface (which occurred in early Pleistocene time) is not affected. Therefore the structural movement occurred after the deposition of the Greenhorn Limestone, but before the early Pleistocene (Bayne, 1977). It is not known what the mechanism might be for this deep structural movement. Core data from drilled wells in the Precambrian is quite limited.

Figure 8: Structure contour map of Cheyenne Bottoms showing the bottom of the Winfield Limestone. Note the depression in T18S R12W. Taken from Bayne (1977).

Figure 9: Bedrock Surface of CB, taken from Bayne (1977).

Below is an animated slideshow feature showing 3 geological map images from Bayne (1977) corresponding to
structural contours below the Hutchinson Salt, the top surface of the Hutchinson Salt, and the bottom of
the Winfield Limestone at the Cheyenne Bottoms.


The table below contains geological details from Bayne (1977) giving a
general litholic stratigraphy analysis by depth at the CB.
Fig. 10, The Bedrock Surface (above)
Fig. 11, The Stone Corral Bottom (above)
Fig. 12, The Hutchinson Salt Top (above)
Fig. 13, The Hutchinson Salt Bottom (above)
Fig. 14, The Windfield Limestone Base (above)
Fig. 15, The Heebner Shale Top (above)
Fig. 16, The Precambrian Surface (above)



3. The Sand Dunes Erosional Blockage Formation Theory

Another theory involves the sand dune formations on the northeastern corner of the CB, the age of which is presently indeterminate (Salley, 2004), however the source of the sand appears to come from overburden deposits lifted from the Cheyenne Bottoms itself. Another potential sand source could be the underlying Dakota formation which supplies sand across much of south-central Kansas. According to this theory, a paleo-river formation known as the Upper Smoky Hills River had flow diverted due to increasing drainage flow associated with Pleistocene glaciation.

During this change of channel flow and increased velocity, erosion sand dunes currently defining the northeastern edge of the basin accumulated and when water inflow through the channel began to recede during drier periods, the alluvial sand deposits previously in solution began to accumulate at the eastern boundary of the Cheyenne Bottoms. This action served to block the lower portion of the river channels further and eventually created the modern day drainage basin structure. This furthermore led to the current flow path of today’s Smoky Hills River which is well north of the present CB formation.

This being one of the original theories (Haworth, 1897): that sand dunes in this manner blocked lower portions of Blood Creek and Deception Creek, thereby arguing that it was surface erosion of soft Pennsylvanian shales which continued until Mississippian limestone layers were encountered by alluvial flows. One possible problem with this theory is that it would seem unlikely that sand dunes would have the component mass or structural integrity necessary to redirect, much less entirely halt the flow of, any type of significant river formation with enough volume of flow to cause the CB formation.




4. The Meteorite Impact Theory

One of the earlier theories involves speculation that CB was formed from a meteor impact, and although that has slowly faded from the conversation within the geological consensus (Merriam, Xia, Harbaugh, 2009) it does bear analysis and review. Analysis of the Cheyenne Bottoms using hillshade maps and surface feature evaluation initially shows strong evidence that could lead to the interpretation that it was formed as the result of a meteorite crater. The primary surface feature is that of an ovoid polygon measuring approximately 13 km x 17 km with an outer rim reaching 30 m above the median surface elevation in some places, despite its dating to the Cretaceous period (approximately 70 Ma). According to research, “Geological disturbances are evident both on the rim and, as shown by drilling, far under the flat floor, at least 900 meters down. The structure is demonstrably neither volcanic, nor a salt solution pit, nor a limestone sink. Cheyenne Bottoms is larger than any United States meteorite crater listed in the RASC Observer’s Handbook (1981). On the Landsat discovery frame, it appears to be surrounded by a concentric annulus of perhaps 37 km diameter. (Sperling, 1979).

While this discussion is initially appealing as a possible cause of what may be an astrobleme, there is a decided lack of supporting geophysical and geochemical evidence which bears a unique hallmark for an impact feature. In contrast to the CB formation, the Edgerton structure of northwestern Miami County, Kansas has a unique set of geophysical signals that may corroborate a possible impact anomaly. In the case of Edgerton, “The geological and geophysical evidences suggest the feature is at or near the buried Precambrian surface. From the size of the surface topographic expression and the amount of sediment overburden, it is suggested that the relief on the Precambrian surface is on the order of 90 m.” (Merriam, et al., 2009), which would place the feature at a surface depth of approximately 1 km. This geophysical evidence is primarily sourced from a set of geomagnetic surveys which detected magnetic anomaly highs (40 nT) at positions corresponding to the outer edges of the presumed crater, and a weak high at the approximate center.

Using the geostatistical horizontal cylinder formula, researchers were able to estimate the depth of this anomaly at Edgerton to a maximum value of 1 km. The geomagnetic survey data thus indicates that the impact feature is at or near the buried Precambrian surface, which is comprised of granite (1.6 Ga) basement complex, with Pennsylvanian and Mississippian limestone and shale and Cambro-Ordovician Arbuckle Group carbonates as overburden.

Figure 17: Ground magnetic anomalies along east-west line after diurnal correction and spike and linear trend removal at the Edgerton Structure. Taken from Merriam, et al. (2009).

A lack of similar direct geophysical and geochemical evidence for CB such as impact breccia structures or meteoritic regmaglypts or other impactites (moldavite and other tektites) make this theory appear doubtful. Likewise the lack of discovery of shattercones at CB which would be indicative of this type of event, lead us to the conclusion that at this time the meteorite impact theory is unsupported beyond a cursory surface topographic review.




Analysis and Conclusions

As noted above, the meteorite impact formation theory can largely be considered discredited in the absence of direct physical evidence beyond a topographical review. The salt dissolution theory is likewise unlikely given the relatively small size of the Hutchison Salt formation at CB.

What remains then are the Precambrian structual contouring theory and the sand dunes erosional blockage theory. Of the two, it would seem that the Precambrian structural contouring theory would be the most likely, as sand in and of itself, even is vast amounts, would seem unlikely to have the necessary structural integrity to control fluvial motion. In fact, the industrial engineering term for this is "bridge scour", where sand and other loose sediment is removed from the base of bridge piers in rivers due to swiftly moving water. It is the largest cause of highway bridge failure in the United States, where 46 of 86 major bridge failures resulted from scour near piers from 1961 to 1976 (USGS, retrieved 2010).

While the Precambrian structural contouring formation theory remains perhaps the most plausible, additional geophysical research such as deep diamond drilling cores would be required to help validate this formation theory which could be related to paleofaulting.




References

Aber, J.S., “Cheyenne Bottoms, Kansas”, accessed online on 28 October 2013, http://academic.emporia.edu/aberjame/wetland/chey_bot/cheyenne.htm

Haworth, Erasmus, 1897. “Physiography of Western Kansas” Kansas Univ. Geol. Survey, vol. 2, pp. 11-49.

Bass, N. W., 1926. “Geologic investigations in western Kansas”, Kansas Geol. Survey, Bull. 11, pp. 1-96.

Johnson, W. D., 1901.“The High Plains and their Utilization” U.S. Geol. Survey, 21st Annual Report, pt. 4, pp. 601-741.

Latta, Bruce F., 1950. “Geology and ground-water resources of Barton and Stafford Counties, Kansas” Kansas Geol. Survey, Bull. 88, pp. 1-228.

C. Bayne, 1976. “Geology and Structure of Cheyenne Bottoms, Barton County, Kansas”, Kansas Geological Survey, Bulletin 211, Part 2, 1976, pp. 1-12.

Salley, S., 2004. “The Geomorphology and Geologic History of Cheyenne Bottoms Central Kansas”. http://academic.emporia.edu/aberjame/student/salley2/index.htm, accessed October 10 2013.

Sperling, N., 1979. “A Large Cretaceous Meteorite Crater in Kansas”, Presentation 23.06, Proceedings of the 159th Meeting of the American Astronomical Society, Boulder, Colorado.

Merriam, Daniel F., Xia, J., Harbaugh, J., 2009. “The Edgerton Structure: A Possible Meteorite Impact Feature in Eastern Kansas”, International Journal of Geophysics, Volume 2009, pp. 1-6.

Zimmerman, J.L., 1990. "Cheyenne Bottoms: Wetland in jeopardy." University Press of Kansas, Lawrence, Kansas, p. 19-21, 197.

Latta, B. F., 1959. ”Geology and ground-water resources of Barton County, Kansas” KGS Bulletin, no. 88. p. 228.

Merriam, D. F., 2005. "Surface expression of buried geologic features in Kansas, or a practical example of the metaphor. The princess and the pea" Kansas Academy Science, Transactions 108/3/4:121–129.

"USGS OGW, BG: Using Surface Geophysics for Bridge Scour Detection". Water.usgs.gov. Retrieved 2010-07-30.

U.S. Bureau of Land Management, http://www.blm.gov/wo/st/en.html website accessed 3 December 2013.