A geomorphic history based on topographic map evidence

The Cheyenne River-Niobrara River drainage divide area between Old Woman Creek and Hat Creek discussed here is located in northwest Nebraska, southwest South Dakota and eastern Wyoming, USA. Although detailed topographic maps of the Cheyenne River-Niobrara River 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 Cheyenne River-Niobrara River 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 deep northeast and north-oriented Powder 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 northwest Nebraska, southwest South Dakota and eastern Wyoming Cheyenne River-Niobrara River drainage divide area landform origins between the Old Woman Creek and Hat Creek. 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 and then by leaving a link to those essays in a comment here.

• 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 northwest Nebraska, southwest South Dakota, and eastern Wyoming Cheyenne River-Niobrara River drainage divide area landform evidence between Old Woman Creek and Hat Creek will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Cheyenne River-Niobrara River drainage divide area between Old Woman Creek and Hat Creek general location map

Figure 1: Cheyenne River-Niobrara River drainage divide area between Old Woman Creek and Hat Creek general 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 Cheyenne River-Niobrara River drainage divide area between Old Woman Creek and Hat Creek. The Cheyenne River begins north of Douglas, Wyoming and flows northeast, southeast, and northeast to the South Dakota border and then southeast around the Black Hills south end before turning northeast to flow as a barbed tributary to the southeast oriented Missouri River (not shown in figure 1). The Niobrara River begins near Lusk in eastern Wyoming (figure 1 south center) and flows southeast before turning northeast in Nebraska and eventually reaches the southeast oriented Missouri River. Old Woman Creek is a north-oriented Cheyenne River tributary, which originates north of Lusk. Hat Creek is not labeled on figure 1, but is the unlabeled stream beginning near Harrison, Nebraska and flowing north-northeast to Ardmore, South Dakota and then to join the Cheyenne River just west of Angostura Reservoir. South and southeast of the Hat Creek-White River drainage divide area is the southeast and northeast oriented Niobrara River. The Hat Creek-White River drainage divide area essay addresses evidence east of the Old Woman Creek-Hat Creek drainage divide area. Northeast of the Hat Creek-White River drainage divide area the Cheyenne River-White River drainage divide area essay address the evidence.  These and other nearby drainage divide area essays can be found under Cheyenne River, White River, or Niobrara River on the sidebar category list (as appropriate to the drainage divide involved).  North of the Cheyenne River-Niobrara River drainage divide area, between Old Woman Creek and Hat Creek, are the Black Hills, which today have elevations significantly higher than Old Woman Creek and Hat Creek drainage basin area locations, and which played an important role in shaping the erosional development of the Cheyenne River-Niobrara River drainage divide area landforms between Old Woman Creek and Hat Creek landforms. This essay interprets Cheyenne River-Niobrara River drainage divide area landform origins between Old Woman Creek and Hat Creek in the context of an immense southeast-oriented flood. Other essays found under appropriate river names on the sidebar category list have established southeast-oriented flood waters flowed across northeast Wyoming’s Powder River Basin and south of the Black Hills to the Old Woman Creek-Hat Creek drainage divide area (see Wyoming’s Belle Fourche River-Cheyenne River drainage divide and Powder River-Belle Fourche River drainage divide essay for examples). Flood waters were first captured by headward erosion of the Niobrara River valley and diverted east and northeast. Next flood waters were captured by headward erosion of the deeper northeast oriented Cheyenne River valley and its north-oriented Hat Creek tributary valley. Subsequently headward erosion of the Cheyenne River-Lance Creek-Old Woman Creek valley captured all southeast-oriented flood flow to the Hat Creek valley. Finally headward erosion of the northeast and north-oriented Powder River valley captured all southeast-oriented flood flow to what is now the Cheyenne River drainage basin and rapid erosion of the Cheyenne River-Niobrara River drainage divide area between Old Woman Creek and Hat Creek ceased.

Cheyenne River-Niobrara River drainage divide area between Old Woman Creek and Hat Creek detailed location map

Figure 2: Cheyenne River-Niobrara River drainage divide area between Old Woman Creek and Hat Creek detailed location map. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 2 provides a detailed location map for the Cheyenne River-Niobrara River drainage divide between Old Woman Creek and Hat Creek. Fall River County is in South Dakota, Dawes County is in Nebraska, and Niobrara County is in Wyoming. Sioux County, Nebraska is located between Dawes County and Niobrara County and is not labelled in figure 2. The Cheyenne River flows southeast from the figure 2 northwest corner to join northeast-oriented Lance Creek near Mule Creek Junction, Wyoming and then flows northeast before turning southeast to flow to Edgemont, South Dakota and around the Black Hills south end and then to flow northeast. Several east and southeast oriented tributaries in the Lusk, Wyoming area (figure 2 southwest quadrant)  flow to the southeast oriented Niobrara River, which flows from Manville, Wyoming to the figure 2 south center edge. Most Niobrara River tributaries shown in figure 2 are southeast oriented. Old Woman Creek originates a short distance north of Lusk and flows north-northeast to join northeast-oriented Lance Creek (near Mule Creek Junction) shortly before Lance Creek joins the Cheyenne River. Hat Creek originates north of Harrison, Nebraska (figure 2 south center) and flows north-northeast to join the Cheyenne River near the Black Hills south end. On figure 2 most Old Woman Creek tributaries are from the east and flow in a northwest direction. One major exception is north- and northeast-oriented Young Woman Creek. Hat Creek tributaries in its headwaters area are both northwest and northeast oriented, although further north there are several southeast-oriented (barbed) tributaries along with more northwest-oriented tributaries. The southeast- and northwest-oriented Hat Creek tributaries, northwest-oriented Old Woman Creek tributaries, and southeast-oriented Cheyenne River and Niobrara River orientations (along with the southeast-orientations of Niobrara River headwaters and of several Cheyenne River tributaries) are evidence valleys of what are today major figure 2 region drainage routes were eroded headward across multiple southeast-oriented flood flow routes such as might be found in a large-scale anastomosing channel complex. The northwest-oriented tributary valleys were eroded by reversals of flood flow on the northwest ends of beheaded flood flow routes.

Cheyenne River-Niobrara River drainage divide area near Lusk, Wyoming

Figure 3: Cheyenne River-Niobrara River drainage divide area near Lusk, Wyoming. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the Old Woman Creek-Niobrara River drainage divide area near Lusk, Wyoming. The Niobrara River originates near Manville, Wyoming and flows southeast to Lusk, where it jogs northeast and then turns southeast to flow to the figure 3 south center edge. North of Lusk are several southeast-oriented Niobrara River tributaries including southeast-oriented Bergreen Creek. North-oriented Old Woman Creek originates in the Hat Creek Breaks area north of Lusk and has northeast and northwest-oriented headwaters. West of the Old Woman Creek headwaters are north-oriented Young Woman Creek headwaters and in the figure 3 northwest corner are northwest-oriented streams to north-northeast-oriented Lance Creek. East of Old Woman Creek are north-oriented Cottonwood Creek and north-northwest-oriented Sage Creek (both Old Woman Creek tributaries). Northwest-oriented Chip Creek is a short distance north of southeast-oriented Bergreen Creek and the two adjacent and parallel streams flowing in opposite directions provide evidence supporting the southeast-oriented flood erosion interpretation. Headward erosion of the southeast-oriented Niobrara River valley first captured southeast-oriented flood flow moving on a topographic surface at least as high as the upland south of Hat Creek Breaks. Headward erosion of the deep Cheyenne River valley to the north then enabled a deep north-oriented Old Woman Creek valley to erode south where it captured southeast-oriented flood flow moving to what was then the actively eroding Niobrara River valley and to divert captured flood waters north to the much deeper Cheyenne River valley. Subsequently the deep Lance Creek valley eroded south-southwest (to the west of the figure 3 map area) and captured southeast-oriented flood flow to the figure 3 map area. In the case of the Bergreen Creek and Chip Creek example, the Bergreen Creek valley orientation was determined by southeast-oriented flood flow moving to the actively eroding Niobrara River valley. The Chip Creek valley alignment was likewise determined by southeast-oriented flood flow moving to the actively eroding Niobrara River valley. However, in the case of Chip Creek, headward erosion of the deep Old Woman Creek valley beheaded a southeast-oriented flood flow route and flood waters on the northwest end of the beheaded flood flow channel reversed flow direction to flow northwest and eroded a northwest-oriented Old Woman Creek tributary valley and created the Cheyenne River-Niobrara River drainage divide.

Cheyenne River-Niobrara River drainage divide area along Hat Creek Breaks east of Lusk, Wyoming

Figure 4: Cheyenne River-Niobrara River drainage divide area along Hat Creek Breaks east of Lusk, Wyoming. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates the Cheyenne River-Niobrara River drainage divide area east of the figure 3 map area and includes overlap areas with figure 3. North-northwest-oriented Sage Creek is located in the figure 4 northwest corner and flows to north-oriented Old Woman Creek. Northeast-oriented Indian Creek flows to the figure 4 north center edge and has several northwest-oriented tributaries flowing from the Hat Creek Breaks escarpment slope. These northwest-oriented tributaries include Mill Creek and Middle Creek. East of northeast-oriented Indian Creek is north-northeast oriented Plum Creek, which is an Indian Creek tributary, and which also has northwest-oriented headwaters. Indian Creek and other northeast-oriented streams flow from the Hat Creek Breaks escarpment base to north-northeast oriented Hat Creek, which is located east of the figure 4 map area. The upland surface south of Hat Creek Breaks is drained by southeast-oriented Duck Creek and south-southeast-oriented Van Tassel Creek, which both flow to the southeast-oriented Niobrara River (south of the figure 4 map area). Northwest-oriented Mill Creek and Middle Creek and north-northwest oriented Sage Creek provide evidence of flood flow reversals on the northwest ends of southeast-oriented flood flow routes. In all three cases the southeast-oriented flood flow was moving on an upland surface at least as high as the upland surface south of Hat Creek Breaks today and was moving to what was then the actively eroding Niobrara River valley. In the case of Mill Creek and Middle Creek the flood flow reversals took place as the deep northeast-oriented Indian Creek valley eroded southwest from what was then a newly eroded north-oriented Hat Creek valley and beheaded southeast-oriented flood flow to the Niobrara River valley. In the case of Sage Creek the flood flow reversal took place as the deep Old Woman Creek valley eroded south and beheaded southeast-oriented flood flow to the newly eroded Indian Creek valley and southeast-oriented flood flow routes to the Niobrara River valley that had yet to be beheaded by Indian Creek valley headward erosion.

Cheyenne River-Niobrara River drainage divide area along Hat Creek Breaks northeast of Van Tassell, Wyoming

Figure 5: Cheyenne River-Niobrara River drainage divide area along Hat Creek Breaks northeast of Van Tassell, Wyoming. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Hat Creek-Niobrara River drainage divide area northeast-of Van Tassell, Wyoming, is east and south of the figure 4 map area, and includes overlap areas with figure 4. North-oriented Hat Creek is located in the figure 5 northeast corner. Northeast-oriented drainage from the Hat Creek Breaks escarpment slope flows to north-oriented Hat Creek and then to the northeast-oriented Cheyenne River. Southeast of Harrison, Nebraska in the figure 5 southeast corner are southeast oriented headwaters of the White River, which after flowing in a southeast direction turns northeast to eventually flow to the southeast oriented Missouri River. The southeast oriented Niobrara River is located in the figure 5 southwest corner and flows to Van Tassell, Wyoming and then south of the figure 5 map (and eventually northeast and east across Nebraska to the Missouri River). South-southeast oriented Van Tassell Creek drains much of the figure 5 Wyoming upland surface to the Niobrara River at Van Tassell, while an unnamed southeast and south-oriented Niobrara River tributary in Nebraska flows along the crest of the Hat Creek Breaks escarpment and then south to Harrison and to the Niobrara River (south of figure 5). Again, note orientations of headwaters of the northeast-oriented Hat Creek tributaries flowing down the Hat Creek Breaks escarpment slope. For example, Monroe Creek headwaters near Gilbert Baker State Wildlife Management Area are northwest-oriented and then turn northeast to flow to Hat Creek. Once more drainage along the escarpment slope is northwest-oriented while on the escarpment crest just a short distance away the drainage is southeast-oriented. This evidence again supports the flood erosion interpretation, with southeast-oriented flood flow moving across the figure 5 map region on a topographic surface at least as high as the upland surface south and west of the Hat Creek Breaks escarpment. Flood waters were moving to what was then an actively eroding Niobrara River valley and were also being captured by headward erosion of an actively eroding White River valley. However headward erosion of the much deeper northeast-oriented Monroe Creek valley from the newly eroded north-oriented Hat Creek valley beheaded southeast-oriented flood flow routes and diverted flood waters northeast and north to the northeast-oriented Cheyenne River valley. Flood flow on the northwest end of the beheaded flood flow route reversed flow direction and eroded what is today the northwest-oriented Monroe Creek headwaters valley.

Old Woman Creek-Hat Creek drainage divide area near Seaman Hills

Figure 6: Old Woman Creek-Hat Creek drainage divide area near Seaman Hills. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates the Old Woman Creek-Hat Creek drainage divide area north of the figure 4 map area and includes overlap areas with figure 4. North-oriented Sage Creek flows along the figure 6 west edge and joins Old Woman Creek north of the figure 6 map area. Note northwest-oriented Sage Creek tributaries including Badland Draw and Sand Draw in the figure 6 northwest quadrant and north and northwest-oriented Spring Creek in the southwest quadrant. The northwest-oriented tributary valleys were eroded by reversals of flood flow on the northwest ends of southeast-oriented flood flow channels captured by headward erosion of the north-oriented Sage Creek valley. The southeast-oriented flood flow had been moving to the actively eroding Indian Creek valley and its tributary valleys located further east in the figure 6 map area. Northeast-oriented Indian Creek flows from the figure 6 southwest quadrant (a short distance east of Spring Creek) to the figure 6 east center edge and has patches of green (trees) located in its valley. Southeast-oriented Oat Creek flows from the figure 6 north center edge to join Indian Creek at the figure 6 east center edge. South of Oat Creek is Brush Creek, which originates in the Seaman Hills area as a northwest-oriented stream and then makes a U-turn to flow southeast to flow to northeast-oriented Indian Creek, which in turn flows to north-oriented Hat Creek and the northeast-oriented Cheyenne River. How did the Brush Creek U-turn originate? Southeast-oriented flood waters flowed across the entire figure 6 map area on a topographic surface at least as high as the upland surface south of the Hat Creek Breaks today. Headward erosion of the deep northeast-oriented Indian Creek valley captured southeast-oriented flood flow routes including southeast-oriented flood flow on the present day southeast-oriented Brush Creek alignment. Flow on that captured route then eroded a deep southeast-oriented valley to the northwest. At about the same time South Brush Creek  was eroding a deep valley southwest from the newly eroded Brush Creek valley and then west and northwest into the Seaman Hills area. For reasons probably related to bedrock characteristics the southeast-oriented Brush Creek valley was able to eroded headward much faster than the South Brush Creek valley. The southeast-oriented Brush Creek then captured the southeast-oriented oriented flood flow route that was eroding the South Brush Creek valley. Flood waters on the northwest end of the beheaded flood flow route reversed flow direction to initiate the northwest-oriented Brush Creek valley. Additional erosion of the northwest-oriented Brush Creek valley was accomplished by flood water moving southeast along the present-day Sand Draw alignment, while those flood waters were still moving at a higher level and prior to being beheaded by Sage Creek headward erosion.

Old Woman Creek-Cottonwood Creek drainage divide area east of Old Woman Hills

Figure 7: Old Woman Creek-Cottonwood Creek drainage divide area east of Old Woman Hills. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Old Woman Creek-Cottonwood Creek drainage divide area north of the figure 6 map area and includes overlap areas with figure 6. Sage Creek joins north-northeast oriented Old Woman Creek in the figure 7 southwest corner and Old Woman Creek roughly parallels the highway to the figure 7 north edge. Southeast-oriented drainage in the figure 7 southeast corner flows to northeast-oriented Indian Creek and then to north-oriented Hat Creek. South-oriented North Brush Creek flows to the figure 7 south center edge and then to southeast-oriented Brush Creek and northeast-oriented Indian Creek. Northeast-oriented Cottonwood Creek flows to the figure 7 east center edge and then to the Cheyenne River at Edgemont, South Dakota. Except along the south edge of figure 7 the Old Woman Creek-Cottonwood Creek drainage divide is a north-south oriented ridge slightly east of the figure 7 center. Even though Cottonwood Creek is northeast-oriented almost all Cottonwood Creek headwaters and tributaries are southeast-oriented, indicating the deep northeast-oriented Cottonwood Creek valley eroded southwest to capture southeast-oriented flood flow moving to the newly eroded northeast-oriented Indian Creek valley and the north-oriented Hat Creek valley. Southeast-oriented North and South Cottonwood Creek headwaters originate today in southeast-oriented basins were being eroded headward as actively eroding heacuts prior to Old Woman Creek valley beheading of the  southeast-oriented flood flow routes to Cottonwood Creek. Beheading of the southeast-oriented flood flow routes to the actively eroding Cottonwood Creek valley system was accomplished first by headward erosion of what is today a south-north oriented through valley located east of the Old Woman Hills, which was closely followed by headward erosion of he north-oriented Old Woman Creek valley. Headward erosion of the Old Woman Creek valley systematically reversed flood flow on the northwest ends southeast-oriented flood flow routes and those reversed flood flow routes captured north-oriented flood waters in the eastern valley, so today the eastern through valley is drained by a series of northwest-oriented Old Woman Creek tributaries.

Drainage divides in Redbird, Wyoming area

Figure 8: Drainage divides in Redbird, Wyoming area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrate drainage divides in the region north of the figure 7 map area and includes overlap areas with figure 7. Old Woman Creek flows north just east of the north oriented highway at the figure 8 south edge and then turns northwest to join northeast-oriented Lance Creek, which flows to the east-northeast oriented Cheyenne River in the figure 8 northwest quadrant. Southeast-oriented drainage in the figure 8 southeast corner flows to northeast-oriented Cottonwood Creek, which flows to the Cheyenne River. Northeast-oriented drainage in the figure 8 northeast corner flows to northeast-oriented Moss Agate Creek, which flows to a southeast-oriented Cheyenne River valley segment. The north-south through valley dividing the figure 8 east and west halves is the previously mentioned through valley east of north-oriented Old Woman Creek valley. The north end of that through valley is drained by north- and northwest-oriented Mule Creek to a northeast-oriented Cheyenne River valley segment. The through valley south end (in figure 8) is drained by northwest-oriented Antelope Creek to the northwest-oriented Old Woman Creek valley. Some events recorded by figure 8 evidence begin with southeast-oriented flood water flowing across the entire figure 8 map region on a topographic surface at least as high as the upland surface located south of the Hat Creek Breaks to the south. Headward erosion of deep northeast-oriented Cottonwood Creek valley next captured southeast-oriented flood flow across the region and southeast-oriented headcuts began to erode into the figure 8 map area. Headward erosion of the deep Cheyenne River valley and its tributary northeast-oriented Moss Agate Creek valley next began to capture southeast-oriented flood flow routes to the actively eroding Cottonwood Creek valley system. Continued headward erosion of the deep Cheyenne River valley next beheaded a major southeast-oriented flood flow route carrying water to the actively eroding Moss Agate Creek and Cottonwood Creek valley systems, causing a reversal of flood flow on the northwest ends of the beheaded flood flow routes. That flood flow reversal initiated the northwest-oriented Mule Creek valley, which eroded a deep valley southeast and then south to capture additional southeast-oriented flood flow. As the north-northwest-oriented Mule Creek valley was being eroded south the parallel deep north-oriented Old Woman Creek valley was also being eroded a short distance to the west. Headward erosion of the Old Woman Creek valley beheaded southeast-oriented flood flow to the actively eroding Mule Creek valley and caused flow reversals that captured north-oriented flood flow in the Mule Creek valley, with the result the Mule Creek valley drainage route was dismembered and is now drained by northwest-oriented Old Woman Creek tributaries. Subsequently the Lance Creek valley eroded southwest and captured all southeast-oriented flood flow to the figure 8 map area.

Drainage divides in the Cheyenne River loop area

Figure 9: Drainage divides in the Cheyenne River loop area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the region north of the figure 8 map area and includes significant overlap areas with figure 8. The Cheyenne River flows northeast and then east in the figure 9 northeast corner and then turns southeast to flow to the figure 9 east center edge. East and West Mule Creek join in the figure 9 southwest corner to form northwest-oriented Mule Creek, which flows to the northeast-oriented Cheyenne River just west of the figure 9 west edge. The North and South Forks of northeast-oriented Moss Agate Creek join in the figure 9 center and Moss Agate Creek then flows to the southeast-oriented Cheyenne River. Northeast-oriented Cottonwood Creek is located in the figure 9 southeast corner. Uplands in the figure 9 northeast corner are part of the Black Hills uplift. Northeast of the southeast-oriented Cheyenne River is southeast-oriented Beaver Creek (not seen in this essay, but discussed in the Wyoming’s Belle Fourche River-Cheyenne River drainage divide essay). The Beaver Creek route apparently carried significant quantities of southeast-oriented flood water from west of he Black Hills to the Black Hills south end and erosion of the deep Cheyenne River valley along what was then a major southeast-oriented flood flow route would be logical. The northeast-oriented Cheyenne River valley segment seen in figure 8 and in the figure 9 northwest corner is aligned with northeast-oriented Lance Creek (and its northeast-oriented Lightning Creek tributary-see figure 1). The northeast-oriented Lightning Creek-Lance Creek valley system was being eroded headward by east-oriented flood waters which the deep Cheyenne River valley captured and which were subsequently captured by North Platte River valley headward erosion (considerably west of the study region here). The east-oriented flood waters were coming east from west of the Wind River Basin and south through the Bighorn Basin, although other essays establish the flood water source to have been elsewhere. Evidence presented here is not adequate to determine flood waters originally flowed in a south and southeast direction from the present day Canadian Rocky Mountains to the Wind River Basin area. Use of many different Missouri River drainage basin landform origins essays permits flood water flow routes to be traced and rapid melting of a thick North American ice sheet located in a deep “hole”  (with the Canadian Rocky Mountains being located along the deep “hole’s” western rim) would be a logical flood water source and would also explain why deep valleys eroded headward to capture south and southeast-oriented flood waters and to divert flood waters further and further to the northeast and north into space the rapidly melting North American ice sheet had once occupied.

Cottonwood Creek-Hat Creek drainage divide near Edgemont, South Dakota

Figure 10: Cottonwood Creek-Hat Creek drainage divide near Edgemont, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 illustrates the Cottonwood Creek-Hat Creek drainage area southeast of the figure 9 map area (the figure 9 southeast corner roughly corresponds with the figure 10 northwest corner). The Cheyenne River flows southeast through Edgemont, South Dakota and cuts a deep canyon through what must be resistant rocks and then flows northeast along the edge of the uplifted resistant rock mass. Cottonwood Creek flows northeast to join the Cheyenne River at Edgemont. Hat Creek flows north-northeast in the figure 10 southeast corner and joins the Cheyenne River just east of the figure 10 east edge. North-northwest-oriented Coal Creek flows from the Igloo area to join Cottonwood Creek and southeast-oriented Plains Creek flows from the Provo, South Dakota area to join the north-oriented Hat Creek as a barbed tributary south of the figure 10 map area. The size of the southeast-oriented Plains Valley is evidence vast quantities of flood water moved along that route (initially to the northeast-oriented White River valley located further to the southeast (see Hat Creek-White River drainage divide essay). Headward erosion of the deep north-oriented Hat Creek valley captured the southeast-oriented flood flow moving to the White River valley and diverted the water north to what must have been the newly eroded and deeper northeast-oriented Cheyenne River valley. Remember, these valleys were being eroded headward into a topographic surface at least as high as the upland surface south of the Hat Creek Breaks and the resistant rocks through which the Cheyenne River canyon is cut were probably still buried. When southeast-oriented flood flow did cut the deep Cheyenne River canyon the deep Cheyenne River valley was able to erode northwest and its tributary northeast-oriented Cottonwood Creek valley was able to erode southwest and to capture southeast-oriented flood flow that had been eroding what is now the Cottonwood Creek-Hat Creek drainage divide. The north-northwest oriented Coal Creek drainage basin was initiated by reversals of flood flow on the beheaded flood flow route to the Plains Creek valley and those reversed flood waters also captured southeast-oriented flood flow from yet to be beheaded (by Cottonwood Creek valley headward erosion) southeast-oriented flow routes further to the south.

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.