A geomorphic history based on topographic map evidence

The Moreau River-Cheyenne River east end drainage divide area discussed here is located in western South Dakota, USA and is east of Dupree, South Dakota. Although detailed topographic maps of the Moreau River-Cheyenne River east end drainage divide area have been available for more than fifty years detailed map evidence has not previously been used to interpret the region’s geomorphic history. The interpretation provided here is based entirely on topographic map evidence. The Moreau River-Cheyenne River east end drainage divide area is interpreted to have been eroded during immense southeast-oriented flood events, the first of which flowed on a topographic surface at least as high as the highest points in the present-day drainage divide area. Flood erosion ended when headward erosion of the east-northeast-oriented Moreau River valley captured all southeast-oriented flood flow.

Preface:

The following interpretation of detailed topographic map evidence is provided as evidence in the Missouri River drainage basin landform origins research project, which is compiling similar evidence for all major drainage divides contained within the Missouri River drainage basin and for all major drainage divides with and within certain adjacent drainage basins. The research project is interpreting evidence in the context of a previously unexplored geomorphology paradigm, which is briefly described in the introduction below. Project essays are listed on the sidebar category list under their appropriate Missouri River tributary drainage basin, Missouri River segment drainage basin (by state), and/or state in which the Missouri River drainage basin is located.

Introduction:

• The purpose of this essay is to use topographic map interpretation methods to explore South Dakota Moreau River-Cheyenne River east end drainage divide area landform origins. Map interpretation methods can be used to unravel many geomorphic events leading up to formation of present-day drainage routes and development of other landform features. While each detailed topographic map feature provides detailed evidence to be explained, the solution must be consistent with explanations for adjacent area map evidence as well as solutions to big picture map evidence puzzles. I invite readers to improve upon my solutions or to propose alternate solutions that better explain evidence and are also consistent with adjacent map area and big picture evidence. Readers may do so either by making comments here or by writing and publishing their own essays.

• This essay is also exploring a paradigm in which erosional landforms are interpreted as evidence left by immense glacial melt water floods. Implied in that interpretation is the immense floods were derived from a thick North American ice sheet that created a deep “hole” in the North American continent and also melted fast. The previously unexplored paradigm being tested in this and similar essays is a thick North American ice sheet, comparable in thickness to the present day Antarctic ice sheet, occupied approximately the North American region usually recognized to have been glaciated and through its weight and erosive actions created a “deep” North American “hole”, through its weight and deep erosion (and perhaps deposition) along major south-oriented melt water flow routes caused significant crustal warping and tectonic change, through its action of melting fast produced immense floods that flowed across the continent, and through its action of melting fast systematically opened up space in the ice sheet created “hole” so headward erosion of newly developed north-oriented drainage systems captured immense south-oriented melt water floods and diverted immense melt water floods north into space the ice sheet had once occupied.

• If this previously unexplored paradigm is correct the geographic region explored by this essay should contain evidence of immense floods that were captured by headward erosion of new valley systems so as to cause the floods to flow in a different direction. Ability of this previously unexplored paradigm to explain Moreau River-Cheyenne River east end drainage divide area landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Moreau River-Cheyenne River east end drainage divide location map

Figure 1: Moreau River-Cheyenne River east end drainage divide location map (select and click on maps to enlarge). National Geographic Society map digitally presented using National Geographic Society TOPO software.

Figure 1 provides a general location map for the Moreau River-Cheyenne River east end drainage divide area. The east end of the Moreau River-Cheyenne River drainage divide to be addressed in this essay refers to the drainage divide region east of Dupree, South Dakota. West of Dupree the Moreau River-Cheyenne River drainage divide evidence is addressed in the Moreau River-Cherry Creek drainage divide area essay (found under Moreau River or Cheyenne River on the sidebar category list). The Moreau River begins in northwest South Dakota just east of the north-oriented Little Missouri River with southeast-oriented headwaters that turn to flow east-northeast across western South Dakota to join the south and southeast-oriented Missouri River as a barbed tributary. North of the Moreau River drainage basin is the parallel Grand River drainage basin. Other regional drainage divide areas are described in essays found under Moreau River, Grand River, Cheyenne River, and Little Missouri River on the sidebar category list. The Cheyenne River begins west of the Black Hills in Wyoming and flows southeast to the Black Hills south end and then turns northeast to flow to the south and southeast-oriented Missouri River as a barbed tributary. Major Cheyenne River tributaries include southeast-oriented Cherry Creek and the southeast-oriented Belle Fourche River (west of the Black Hills Belle Fourche River headwaters are northeast-oriented). Other essays also address Cheyenne River and Belle Fourche River evidence west of the Black Hills and include, among others,  Belle Fourche River-Cheyenne River drainage divide area and Little Missouri River-Belle Fourche River drainage divide area essays. This essay interprets Moreau River-Cheyenne River east end drainage divide evidence to have originated during an immense southeast-oriented flood that was systematically captured and diverted to the northeast. Evidence presented here will demonstrate the deep northeast-oriented Cheyenne River valley eroded headward to capture the southeast-oriented flood flow and subsequently the east-northeast-oriented Moreau River valley eroded headward to behead southeast-oriented flood flow routes to the eastern Cheyenne River valley and to divert the flood water further to the northeast. By doing so headward erosion of the deep Moreau River valley created the present day Moreau River-Cheyenne River east end drainage divide. The essay concludes with a brief discussion of how the south and southeast-oriented Missouri River valley captured what had become (after Cheyenne River and Moreau River valley headward erosion) northeast-oriented flood flow.

Detailed Moreau River-Cheyenne River east end drainage divide location map

Figure 2: Detailed Moreau River-Cheyenne River east end drainage divide location map. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 2 provides a detailed location map for the Moreau River-Cheyenne River east end drainage divide area.The Cheyenne River flows northeast from the figure 2 southwest corner to join the south-oriented at a rather remarkable incised meander, which will be discussed with figure 10. Moreau River headwaters are located in the figure 2 northwest quadrant and flow southeast and east and then the Moreau River turns to flow northeast, before turning southeast just before joining the south-oriented Missouri River in the figure 2 northeast quadrant. Detailed maps below will begin with the Moreau River-Cheyenne River drainage divide area in the Dupree, South Dakota area and proceed east along the Moreau River-Cheyenne River drainage divide. At the drainage divide east end detailed maps will also include a look at the Moreau River valley southeast wall and the Cheyenne River valley north wall as well as a look at the Cheyenne River-Missouri River confluence area. Evidence of the immense southeast-oriented flood that was captured first by headward erosion of the northeast oriented Cheyenne River valley and subsequently by headward erosion of northeast-oriented Moreau River valley can be seen in figure 2 in the many southeast-oriented Cheyenne River and Moreau River tributaries and in northwest-oriented tributaries to the Moreau River and the Cheyenne River. The numerous southeast-oriented tributaries suggest the Cheyenne River valley and subsequently the Moreau River valley eroded headward across multiple southeast-oriented flood flow routes such as might develop in an immense southeast-oriented anastomosing channel complex. The northwest-oriented tributary valleys were probably eroded by reversed flow of flood waters on the northwest ends of southeast-oriented flood channels that were beheaded by headward erosion of the deep northeast-oriented valleys.

Moreau River-Cheyenne River drainage divide area near Dupree, South Dakota

Figure 3: Moreau River-Cheyenne River drainage divide area near Dupree, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the Moreau River-Cheyenne River drainage divide in the Dupree, South Dakota region. Bear Creek flows east from the Red Elm area in the figure 3 northwest corner to the Dupree area and then to the figure 3 northeast corner where it turns north and flows to the northeast-oriented Moreau River, which is located north of the figure 3 map area. Note the southeast-oriented tributaries to east-oriented Bear Creek from the north and northwest-oriented Bear Creek tributaries from the south. This southeast-northwest-oriented tributary alignment is evidence the east-oriented Bear Creek valley eroded west across multiple southeast-oriented flood flow routes. In the figure 3 south center is a large southeast-oriented basin in which the headwaters of a southeast-oriented Cheyenne River tributary are located. That southeast-oriented tributary is Cottonwood Creek (see figure 2) and the basin is an abandoned headcut that was eroded headward along a major southeast-oriented flood flow route that was beheaded when the east-oriented Bear Creek valley eroded west to capture the southeast-oriented flood flow. Similar abandoned headcuts are located on both sides of the Cottonwood Creek abandoned headcut and are evidence of multiple southeast-oriented flood flow routes that were beheaded when the east-oriented Bear Creek valley eroded west. Also note headwaters of Little Bear Creek flowing southeast from near Marpie Butte and then turning northeast to flow to north-oriented Bear Creek and the northwest-oriented tributaries to the northeast-oriented Bear Creek valley segment. The Little Bear Creek valley eroded southwest to capture southeast-oriented flood flow moving to the Rudy Creek (unnamed in figure 3) abandoned headcut located in the figure 3 southeast corner. The figure 3 Moreau River-Cheyenne River drainage divide was created when the Bear Creek and Little Bear Creek valleys eroded headward and systematically captured southeast-oriented flood flow routes that were eroding the southeast-oriented headcuts northwest. Lakes south of Lantry will be addressed in the figure 4 discussion.

Moreau River-Cheyenne River drainage divide area near Lantry, South Dakota

Figure 4: Moreau River-Cheyenne River drainage divide area near Lantry, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates the Moreau River-Cheyenne River drainage divide region east of the figure 3 map area and provides a significant overlap area. The southeast-oriented Cottonwood Creek abandoned headcut is located by Marpie Butte along the figure 4 west edge center. The southeast-oriented Rudy Creek abandoned headcut is located south of the lakes in the figure 4 south center and adjacent southeast-oriented abandoned headcuts have eroded what looks like a southeast-oriented escarpment just southeast of the lake covered upland surface. The northeast-oriented Little Bear Creek valley eroded southwest to capture southeast-oriented flood flow to the southeast-oriented Rudy Creek headcut and headward erosion of that headcut ceased when the southeast-oriented flood flow routes were beheaded. The north-oriented Bear Creek valley (not visible in figure 4) had previously beheaded southeast-oriented flood flow to the southeast-oriented headcuts northeast of the Rudy Creek abandoned headcut, which caused headward erosion of those southeast-oriented headcuts to also cease. The lakes on the upland surface suggest the region may have been glaciated and that ice was still present when the southeast-oriented flood water was flowing over the figure 4 map region. If so flood waters flowed over a decaying ice sheet remnant that perhaps melted after the Moreau River-Cheyenne River drainage divide had been created. Because this area of lakes is small the decaying ice sheet remnant must also have been small, at least by the time flood flow across the figure 4 region was captured by headward erosion of the Moreau River to the north. However, it is quite possible initially this entire Moreau River-Cheyenne River east end drainage divide region was covered by a decaying ice sheet when the southeast-oriented flood flow commenced and that flood waters played a significant role in melting and otherwise removing the decaying ice and also in removing at least some of the ice sheet deposited materials.

Moreau River-Cheyenne River drainage divide east of Eagle Butte, South Dakota

Figure 5: Moreau River-Cheyenne River drainage divide east of Eagle Butte, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Moreau River-Cheyenne River drainage divide region east of the figure 4 map area and provides an overlap area. The Moreau River-Cheyenne River drainage divide is located along the rim of the south and southeast-facing escarpment. The southeast-oriented abandoned headcut southeast of Eagle Butte is today drained by southeast-oriented Herbert Creek to the Cheyenne River. The larger southeast-oriented abandoned headcut southeast of Parade is drained by Hosupa Creek and Fishgut Creeks, with Hosupa Creek being a Fishgut Creek tributary, and also flowing to the northeast-oriented Cheyenne River. Figure 8 below will show where Herbert Creek and Fishgut join the Cheyenne River. North-northeast-oriented Green Grass Creek in the figure 5 northwest corner flows to the northeast-oriented Moreau River. Note northwest-oriented Green Grass Creek tributaries providing evidence the Green Grass Creek valley eroded south-southwest to capture southeast-oriented flood flow that was eroding the southeast-oriented Hosupa Creek-Fishgut Creek headcut to the northwest. In the figure 5 northeast quadrant west and north-northwest-oriented Goose Creek also flows north to the northeast-oriented Moreau River. Note how  west-oriented Goose Creek headwaters are located almost at the rim of the southeast-oriented headcut. Northeast-oriented Goose Creek tributaries may have eroded southwest to capture southeast-oriented flood flow on yet to be beheaded (by headward erosion of the Moreau River valley to the north) flood flow routes. Such captured flood waters probably helped erode the significant Goose Creek valley. There may have been a decaying ice sheet remnant north of Parade where the shallow lakes are today that melted after Moreau River valley headward erosion had captured all flood flow moving across the figure 5 map area.

Moreau River-Cheyenne River drainage divide near Ridgeview, South Dakota

Figure 6: Moreau River-Cheyenne River drainage divide near Ridgeview, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates the Moreau River-Cheyenne River drainage divide region east of the figure 5 map area and provides an overlap area. The large south-oriented abandoned headcut southwest of Ridgeview is drained by Charlie Creek (unnamed on figure 6) and east of the Charlie Creek headwaters are headwaters of south-oriented West and East Branches of Tall Prairie Chicken Creek (figure 10 below will show the Cheyenne River and Missouri River valleys to the south where Charlie Creek and Tall Prairie Chicken flow to the Missouri River). Headwaters of Willow Creek flow southeast in the figure 6 southeast corner. Northwest of Ridgeview are headwaters of northwest oriented Bull Creek and Cottonwood Creek, which flow to the northeast-oriented Moreau River. Northwest-oriented drainage along the figure 6 west edge flows to north-northwest oriented Goose Creek, which also flows to the northeast-oriented Moreau River. The east-facing escarpment south of La Plant, South Dakota drains to the south-oriented Missouri River, with Willow Creek being a southeast oriented Missouri River tributary. Northeast-oriented Virgin Creek flows along the escarpment rim from south of Ridgeview to La Plant and then north to the northeast-oriented Moreau River valley. Events recorded by the figure 6 evidence begin with southeast oriented flood water flowing across the entire figure 6 map area. Headward erosion of the deep northeast-oriented Cheyenne River valley captured the southeast oriented flood water and flood waters began to erode multiple southeast and south-oriented headcuts into the newly eroded and deep Cheyenne River valley north wall. Subsequently the northeast-oriented Moreau River valley and its Virgin Creek tributary eroded southwest to capture southeast oriented flood water flowing to the southeast- and south-oriented Willow Creek and Tall Prairie Chicken headcuts. Headward erosion of the Moreau River valley beheaded southeast-oriented flood flow routes to the figure 6 map area in sequence (from east to west) and reversed flow on the present day Bull Creek, Cottonwood Creek, and Goose Creek alignments to develop the present day northwest and north oriented tributary valleys and to create the present-day Moreau River-Cheyenne River drainage divide.

Moreau River southeast valley wall north of Ridgeview, South Dakota

Figure 7: Moreau River southeast valley wall north of Ridgeview, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Moreau River valley southeast wall north of the figure 6 map area and provides an overlap area. Virgin Creek flows northeast through La Pant and then flows north to the Moreau River. West of Virgin Creek, Swan Creek flows north to Swan Lake and then to the Moreau River. Northwest-oriented Bull Creek and Cottonwood Creek flow to the Moreau River in the figure 7 northwest corner. Events recorded in this figure 7 evidence begin with southeast-oriented flood water flowing across the present day Moreau River-Cheyenne River drainage divide and also across the Moreau River-Missouri River drainage divide seen south of La Plant in the figure 7 southeast corner. At that time the large northeast-oriented Moreau River valley did not exist. Headward erosion of what must have been a large and deep northeast-oriented Moreau River then began to systematically capture the southeast-oriented flood flow. The north and northeast-oriented Virgin Creek valley eroded south to capture southeast-oriented flood flow from yet to be beheaded (by headward erosion of the deep Moreau River valley) flood flow routes using the present day Bull Creek and Cottonwood Creek alignments. As Moreau River valley headward erosion progressed the north-oriented Swan Creek valley eroded headward to capture southeast-oriented flood flow routes that were providing flood waters to the Virgin Creek valley, ending erosion of the Virgin Creek drainage basin. Next headward erosion of the deep Moreau River valley beheaded and captured the southeast-oriented flood flow routes that were providing flood water to erode the north-oriented Swan Creek valley. Flood flow on the northwest ends of those beheaded flood flow routes reversed flow direction to erode the northwest-oriented Bull Creek and Cottonwood Creek valleys.

Cheyenne River valley south of Mossman, South Dakota

Figure 8: Cheyenne River valley south of Mossman, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates the Cheyenne River valley south of the figure 5 map area. There is no overlap with figure 5, although Fishgut Creek flows south from the figure 8 north center to the southeast-oriented bay just west of Fine Weather Draw. Herbert Creek flows south-southeast to the southeast-oriented bay located just west of the southeast-oriented Fishgut Creek bay. The northeast-oriented Cheyenne River valley is at this location turning to become an east-oriented valley before entering the Missouri River valley. The Cheyenne River valley has been flooded here by the Lake Oahe reservoir impounded behind Oahe Dam on the Missouri River. The Kid Rich Flats located southwest of the Herbert Creek bay and similar benches elsewhere in the Cheyenne River valley suggest Cheyenne River valley erosion did not occur in a single step. Apparently an initial somewhat shallower valley eroded west and southwest and later a narrower and deeper valley eroded into the floor of the earlier Cheyenne River valley. Headward erosion of the initial higher level Cheyenne  River valley would have captured all southeast-oriented flood flow and diverted the flood waters northeast. The subsequent deeper and narrower valley within the original Cheyenne River valley probably represents a base level lowering somewhere to the northeast. Reasons for that base level lowering cannot be determined from the figure 8 evidence, but is related to the Missouri River valley, which will be observed in figure 10. The figure 10 discussion will suggest the shallower northeast-oriented valley was eroded by headward erosion of a northeast-oriented valley from somewhere in northeastern South Dakota (and probably further north) while the deeper and narrower inner valley was eroded when the south- and southeast-oriented Missouri River valley captured the northeast-oriented Cheyenne River valley and caused a reversal of flow on the southwest end of the beheaded northeast-oriented valley upstream from the present day Cheyenne River mouth.

Cheyenne River valley wall south of Ridgeview, South Dakota

Figure 9: Cheyenne River valley wall south of Ridgeview, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Cheyenne River valley north wall south of the figure 6 and 7 map areas and provides some overlap areas. Figure 9 evidence may help better explain the Cheyenne River valley relationship with the Missouri River valley. The west-southwest facing escarpment slope south of Ridgeview is drained mostly by Cheyenne River tributaries. The east-facing escarpment slop east of Ridgeview is drained by Missouri River tributaries. The upland surface is drained by northeast-oriented headwaters of Virgin Creek, which later turn north to flow to the northeast-oriented Moreau River. Flood flow that eroded the south-southwest-facing escarpment slope and the east-facing escarpment slope was beheaded by headward erosion of the Virgin Creek valley, which was related to headward erosion of the deep northeast-oriented Moreau River valley. In other words, the Cheyenne River valley and the Missouri River valley both existed when the Moreau River valley and its tributary Virgin Creek valley were being eroded, although there may not have been a significant time gap between the formation of the Cheyenne River and Missouri River valleys (in the figure 9 location) and the headward erosion of the northeast-oriented Virgin Creek valley. The figure 9 evidence suggests there was a close relationship between the erosion of all three valleys, although there also was an important sequence of events that must be accounted for. In any case, immense quantities of water would be need to erode the valleys in this figure 9 map area and to do so in the sequence recorded in evidence this essay presents.

Confluence of Cheyenne River and Missouri River southeast of La Plant, South Dakota

Figure 10: Confluence of Cheyenne River and Missouri River southeast of La Plant, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 illustrates the Cheyenne River downstream from the figure 8 map area and also shows the Cheyenne River-Missouri River confluence area. For reference with figure 6 Tall Prairie Chicken flows south-southeast just west of No Heart Butte in the figure 10 north center and Charlie Creek flows south-southwest just west of Tall Prairie Chicken Creek. Also note southeast-oriented Willow Creek Bay in the figure 10 east center. The flooded Cheyenne River valley is located in figure 10 southwest corner. What is particularly intriguing about this location is the large incised Missouri River meander where the southwest-oriented Missouri River in the figure 10 southeast corner turns to flow northwest and then reverses direction to flow southeast near the location of the east-oriented Cheyenne River mouth. While figure 10 evidence is limited and a bigger picture view is needed to fully understand the regional drainage history this remarkable incised meander suggests a major northeast oriented flood eroded valley and a major southeast-oriented flood eroded valley somehow met at this figure 10 location. The southeast-oriented valley probably was the flood eroded Missouri River valley downstream from this figure 10 location. The northeast oriented valley probably extended northeast along the present day Missouri River valley where the Missouri River today flows southwest (see figure 2). Somewhere upstream, perhaps along the Little Cheyenne Creek alignment may be evidence the northeast oriented valley once continued northeast across northeast South Dakota. What can be said with evidence presented here is a large northeast-oriented valley eroded southwest to the figure 10 location and at approximately the same time what was probably a deeper south- and southeast-oriented Missouri River valley eroded north and northwest and captured flood flow from the newly eroded Cheyenne River valley and also reversed flow on the southwest end of the beheaded northeast-oriented valley to create a southwest-oriented Missouri River valley segment. The northeast- and southeast-oriented Moreau River valley seen upstream from the Moreau River-Missouri River confluence (see figures 1 and 2) probably was initiated as a tributary to the northeast-oriented valley, but was subsequently captured by the south-oriented Missouri River valley when flow on the southwest end of the northeast-oriented valley was reversed to flow south and southeast instead of northeast.

Additional information and sources of maps studied

This essay has provided only a sample of the detailed topographic map evidence supporting the flood erosion interpretation. Many additional illustrations could be provided. Readers are encouraged to look at mosaics of detailed topographic maps to see the abundance of available data. Maps used in this study were created and published by the United States Geologic Survey and can be obtained directly from the United States Geological Survey and/or from dealers offering United States Geological Survey maps. Hard copy maps can also be observed at United States Geological Survey map depositories which are located throughout the United States and elsewhere. Illustrations used here were created using National Geographic Society TOPO software and digital map data. TOPO software and map data can be obtained from the National Geographic Society and/or dealers offering National Geographic Society digital map data.