A geomorphic history based on topographic map evidence

The Missouri River-James River drainage divide area discussed here is located in Buffalo, Jerauld, Brule, and Aurora Counties, South Dakota and also includes some areas in Hyde and Hand Counties. Major landforms illustrated and discussed include the Missouri River valley, a Missouri Coteau upland surface remnant, and escarpments bounding the Missouri Coteau upland surface remnant. The Missouri River valley is interpreted to have eroded around the southwest margin of a decaying North American ice sheet at a time when immense southeast-oriented melt water floods were being captured and diverted east and northeast onto the former ice sheet floor. Escarpments bounding the Missouri Coteau remnant are interpreted to be what remains of the walls of immense ice-walled and bedrock-floored valleys sliced into the decaying ice sheet’s surface. The Missouri Coteau upland surface area is interpreted to be where a detached ice sheet remnant once stood and eventually melted and deposited whatever debris it contained.

• The purpose of this essay is to use topographic map interpretation methods to explore Missouri River-James River drainage divide area landform origins in Buffalo, Jerauld, Brule, and Aurora Counties, South Dakota, USA. 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 and/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 new geomorphology 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 other Missouri River drainage basin landform origins research project essays is a thick North American ice sheet, comparable in thickness to the Antarctic ice sheet, occupied the North American region usually recognized to have been glaciated, and through its weight and erosive actions created a deep North American “hole”. The southwestern rim of that deep “hole” is today preserved in the high Rocky Mountains. The ice sheet 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 Missouri River-James River drainage divide area landform evidence in Buffalo, Jerauld, Brule, and Aurora Counties, South Dakota will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm. This essay is included in the Missouri River drainage basin landform origins research project essay collection.

Missouri River-James River drainage divide area location map

Figure 1: Missouri River-James River drainage divide area 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 location map for the Missouri River-James River drainage divide area discussed in this essay. South Dakota is the state occupying most of the figure 1 map area. Nebraska is the state south of South Dakota. A small area of southwest Minnesota can be seen along the figure 1 east edge (north half). Iowa is the state seen along the figure 1 east edge south of Minnesota. The Missouri River flows from the figure 1 northwest corner in a south and southeast direction to the Nebraska border and then forms the South Dakota-Nebraska border as it flows to Sioux City, Iowa in the figure 1 southeast corner. The James River flows in a south-southeast direction from near Redfield in the figure 1 north center to Huron, Mitchell and Yankton, where it joins the Missouri River. The Missouri River valley has been flooded by reservoirs impounded behind several major dams. Lake Oahe is a large reservoir impounded behind Oahe Dam located near Pierre. Lake Sharpe is the reservoir created by Big Bend Dam, located near Fort Thompson. Lake Francis is the reservoir created by Fort Randall Dam, located near Pickstown. Major Missouri River tributaries from the west (from north to south) are the northeast and east oriented Cheyenne River (located in the figure northwest corner); the northeast-oriented Bad River, joining the Missouri River as a barbed tributary near Pierre; and the east-oriented White River, which joins the Missouri River a short distance downstream from Chamberlain. The Missouri River-James River drainage divide area discussed here emphasizes the Missouri River valley area and includes a detailed discussion of the region east and north of Big Bend Dam and extends as far north as Ree Heights and extends south to the Red Lake area along Interstate highway 90 between Chamberlain and Mitchell. The James River-Big Sioux River drainage divide area essay discusses the region south of Mitchell and Sioux Falls and includes James River valley maps, which are not included here. Of particular interest in this essay is the region between a large through valley roughly following the route of west to east oriented highway 14, which links the Missouri River and James River valleys and through valleys linking the Missouri River valley with headwaters of southwest-oriented Platte Creek, which originates near White Lake. On figure 1 the northern through valley appears to be an extension of the northeast-oriented Bad River valley and the southern through valleys appear to be extensions of the White River valley. If so, those valleys were eroded prior to headward erosion of the southeast-oriented Missouri River valley. Missouri River valley headward erosion is interpreted here to have occurred late during the rapid melt down of a thick North American ice sheet.

Missouri River-James River drainage divide area detailed location map

Figure 2: Missouri River-James River drainage divide area detailed location map. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 2 provides a slightly more detail map of the Missouri River-James River drainage divide area in Buffalo, Jerauld, Brule, and Aurora Counties. County boundaries and names are shown in figure 2 and generally maps and discussion in this essay focus on the indicated counties, although figures 3, 4, and 5 below include areas in Hyde and Hand Counties, which are located north of Buffalo County. The Missouri River is the south-southeast oriented river in the figure 2 west half. The James River flows south-southeast in Sanborn County and the Davison County northeast corner to Mitchell. From Mitchell the James River flows in a southeast direction to the figure 2 southeast corner. The red shaded area east of the Missouri River is the Crow Creek Indian Reservation and west of the Missouri River is the Lower Brule Indian Reservation. The essay begins with topographic maps of a high level drainage divide area immediately north and northeast of Big Bend Dam in the figure 2 northwest corner area. Maps show northwest-southeast and north-south oriented through valleys eroded into an upland surface characterized by a glacial moraine type landscape. Of particular interest in that area are the Elm Creek and Smith Creek valleys. That upland surface is a Missouri Coteau upland surface remnant. A north-facing escarpment, which marks the south wall of the northern east-oriented through valley referred to in figure 1 (the through valley associated with the Bad River) is shown in figure 5 although the escarpment location is north of the figure 2 map area. Next are three maps illustrating valley systems and through valleys south and southeast from Big Bend Dam. The Smith Creek valley is investigated as are valleys in the Red Lake area. Figure 9 illustrates the east-facing Missouri Escarpment near Wessington Springs in Jerauld County. The Missouri Escarpment marks the eastern boundary of the Missouri Coteau upland surface area seen earlier and the western boundary of the James River lowland surface. The essay concludes with maps of the Red Lake area in eastern Brule County and the Missouri Escarpment near White Lake in western Aurora County and of the Platte Creek headwaters area near the Escarpment base. Platte Creek flows south along the Aurora County west edge and then turns to flow in a southwest direction to join the Missouri River south of the figure 2 map area. Note how the Red Lake and White Lake areas are located east of where the east-oriented White River joins the south-oriented Missouri River.

Missouri River valley near Big Bend Dam

Figure 3: Missouri River valley near Big Bend Dam. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the Missouri River valley in the Big Bend Dam area. The Missouri River flows east and southeast from the figure 3 west edge before making a U-turn to flow in a northwest direction before making another U-turn to flow in a southeast, south, and southeast direction to Big Bend Dam and then to the figure 3 south edge. Medicine Creek is the north-oriented Missouri River tributary located in the figure 3 southwest corner. The southeast oriented stream located adjacent to the highway in the figure 3 north center is the West Fork Elm Creek. Elm Creek flows south and southeast in the figure 3 northeast corner and joins the West Fork before flowing to the figure 3 east edge. Note other southeast oriented streams located between the West Fork Elm Creek and the Missouri River valley. Also note southwest oriented streams in the figure 3 northwest quadrant, which flow to the Missouri River valley as barbed tributaries. Figure 3 landforms can be explained in the context of an immense southeast oriented flood, which originally flowed on a topographic surface at least as high as the highest figure 3 elevations today. The multiple southeast-oriented valleys indicate that flood waters were moving in what was probably a large-scale southeast-oriented anastomosing channel complex. Headward erosion of the Missouri River valley and its tributary valleys systematically captured the southeast-oriented flood flow which was deeply eroding the figure 3 map area. To understand how the Missouri River valley U-turns originated first look at the north-oriented Medicine Creek valley in the figure 3 southwest corner. Note how Medicine Creek has southeast- and northwest-oriented tributary valleys. This northwest-southeast tributary orientation is evidence the north-oriented Medicine Creek valley eroded headward across multiple southeast-oriented flood flow channels. The southeast-oriented tributary valleys were eroded headward from the newly eroded Medicine Creek valley wall. The northwest-oriented tributary valleys were eroded by reversals of flood flow on the northwest ends of beheaded southeast-oriented flood flow routes. Because the Medicine Creek valley eroded headward it beheaded the flood flow channels one channel at a time. Also, because the flood flow channels were anastomosing (or interconnected), reversed flow in one channel could often capture yet to be beheaded flood flow from adjacent channels. The Missouri River U-turns originated from the beheading of southeast-oriented flood flow channels and then captures of yet to be flood flow from adjacent channels. As the deep Missouri River valley eroded headward it beheaded southeast-oriented flood flow to several of the southeast-oriented streams located between the West Fork Elm Creek and the Missouri River valley. Also southwest-oriented tributary valleys in the figure 3 northwest corner area eroded headward to capture southeast-oriented flood flow to the West Fork Elm Creek valley

West Fork Elm Creek headwaters area

Figure 4: West Fork Elm Creek headwaters area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates the West Fork Elm Creek headwaters area north of the figure 3 map area and includes overlap areas with figure 3. Figure 4a below shows the Chapelle Creek-West Fork Elm Creek drainage divide area northwest of the figure 4 map area (and includes overlap areas with figure 4). The Missouri River is located in the figure 4 southwest corner. The West Fork Elm Creek originates in the Dewey Township area in the figure 4 northwest quadrant and flows in a southeast direction to join south-oriented Elm Creek in the figure 4 southeast quadrant. Elm Creek flows in a southwest direction in the figure 4 northeast quadrant before turning to flow south to join the West Fork in the figure 4 southeast quadrant. Note a southeast-oriented West Fork Elm Creek tributary which originates almost on the edge of the steep Missouri River valley wall and which flows east-southeast along the highway to join the West Fork just southeast of Stephan. Note the southeast-oriented slope south of Stephan and the southeast-oriented stream originating on that slope. That southeast-oriented slope was eroded by southeast-oriented flood water moving into what was then the actively eroding Missouri River valley head. Headward erosion of the West Fork Elm Creek valley and its east-southeast oriented tributary valley captured the southeast-oriented flood flow at about the same time headward erosion of the Missouri River valley and Missouri River tributary valleys beheaded flood flow routes crossing the figure 4 map area. Evidence that southeast-oriented flood water once moved across the drainage divide in the figure 4a can be seen in the form of through valleys linking the West Fork Elm Creek drainage basin with northwest-oriented tributaries to west and west-southwest oriented Chapelle Creek (seen in the figure 4a north half). Also note in figure 4a how the southwest-oriented Chaney Rush Creek valley eroded headward from the deep Missouri River valley to capture southeast-oriented flood flow. Headward erosion of the deeper Chapelle Creek valley beheaded southeast-oriented flood flow channels and diverted the water west and southwest to newly eroded and much deeper Missouri River valley. Reversals of flood flow on the northwest ends of beheaded flood flow routes were responsible for eroding the northwest-oriented Chapelle Creek valley slope.

Figure 4a: Chapelle Creek-West Fork Elm Creek drainage divide area northwest of figure 4. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Missouri Coteau upland surface and Elm Creek headwaters area

Figure 5: Missouri Coteau upland surface and Elm Creek headwaters area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Missouri Coteau and the Elm Creek headwaters area and is located in Hyde and Hand County north of the figure 4 map areas. Figure 5 is intended to link areas in Buffalo and Jerauld Counties with areas illustrated and discussed in the Missouri River-James River drainage divide area in Sully, Hyde, Hand and Hughes Counties essay, which addresses the region immediately to the north of figure 5 see essays under James River on sidebar category list). Ree Heights is the town located just east of the north center edge area. Note the north-facing escarpment just south of Ree Heights and the east-northeast facing escarpment along the figure 5 east edge area. The upland region south and west of these escarpments is the Missouri Coteau upland surface. The Missouri Coteau upland surface seen here is isolated from Missouri Coteau upland surface areas further to the north by a large east-oriented through valley. The north-facing escarpment is the east-oriented through valley’s southern wall. The east-northeast facing escarpment is the Missouri Escarpment, which serves as the western boundary of the James River lowland. The Missouri Escarpment is interpreted to be what remains of the west wall of an immense south-oriented ice-walled and bedrock-floored valley sliced into the surface of a rapidly melting thick North American ice sheet. The north-facing escarpment in figure 5 is interpreted to be what remains of the south wall of a large east-oriented ice-walled and bedrock-floored valley sliced into the surface of that same decaying ice sheet. The Missouri Coteau upland surface remnant seen in figure 5 is interpreted to be where an isolated ice sheet remnant once stood, and eventually melted and deposited whatever debris it contained (melt water floods removed much of the ice sheet contained debris from the adjacent valley floors). The north-northeast to south-southwest through valley located in the center of figure 5 is where Elm Creek originates (just north of the words SPRING HILL). An Elm Creek tributary originates in the southeast-oriented through valley located west of the north-northeast-south-southwest through valley. Note how both through valleys extend to north-facing escarpment crest and are in fact eroded into the upper escarpment slope. These Elm Creek headwaters valleys probably originated as narrow ice-walled and bedrock-floored valleys prior to headward erosion of the larger and deeper east-oriented through valley north of the north-facing escarpment. Water responsible for eroding these south-oriented Elm Creek valleys probably was south-oriented melt water coming from north of the figure 5 map area and may have been moving to what was then the actively eroding Missouri River valley head. If so the large east-oriented through valley north of figure 5 was eroded at approximately the same time as the Missouri River valley was eroding northwest through Big Bend Dam area.

Crow Creek valley near Big Bend Dam

Figure 6: Crow Creek valley near Big Bend Dam. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates the Crow Creek valley located southeast of Big Bend Dam and south and east of figure 3 (and includes overlap areas with figure 3). The southeast, south, and southeast oriented Missouri River is located in the figure 6 west half. Big Bend Dam is located in the figure 6 northwest corner. Crow Creek flows west from the figure 6 east edge and meanders north and then south before flowing west and northwest to join the south-oriented Missouri River as a barbed tributary. The northwest-oriented tributary joining the northwest-oriented Crow Creek valley segment is Smith Creek (figure 7 illustrates the Smith Creek valley southeast of the figure 6 map area). Elm Creek is the meandering south-oriented stream with a wooded valley located in the figure 6 northeast corner. Note the high level southeast-sloping erosion surface in the figure 6 southwest quadrant into which the Missouri River valley has been eroded. Elevations on the erosion surface are more than 100 meters higher than the reservoir elevation in Lake Francis Case (impounded behind Fort Randall Dam). In other words, the Missouri River valley was eroded into an erosion surface at least 100 meters higher than the valley floor is today. The northwest-oriented Smith Creek-Crow Creek valley was eroded by southeast-oriented flood water prior to headward erosion of the deep Missouri River valley. Note how that northwest-oriented tributary valley is on the same alignment as the southeast-oriented Missouri River valley segment upstream from the Crow Creek mouth. Elevations on the bench just north of the northwest-oriented Crow Creek valley segment are more than 50 meters lower than on the high level erosion surface just south of that valley segment, which means the southeast-oriented flood flow was moving in channel at least 50 meters deep. Yet, enough flood water was spilling south from that southeast-oriented flood flow channel to erode the much deeper Missouri River valley northwest and north to behead the large southeast-oriented Crow Creek-Smith Creek flood flow channel. Flood waters on the northwest end of the beheaded southeast-oriented flood flow channel reversed flow direction and created the present day northwest-oriented Smith Creek-Crow Creek valley. Smaller amounts of flood water also flowed south into the Crow Creek valley from the Elm Creek valley seen in figure 5 above and also from the Crow Creek headwaters area. What is impressive about the Smith Creek-Crow Creek valley is the evidence it provides concerning the volumes of flood waters moving across the figure 6 area at the time the deep Missouri River valley eroded headward into the region.

Smith Creek valley area southeast of Big Bend Dam

Figure 7: Smith Creek valley area southeast of Big Bend Dam. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the west and northwest oriented Smith Creek valley southeast of the figure 6 map area and includes overlap areas with figure 6. Smith Creek flows west-southwest in Lyon Township (in the figure 7 east center edge area) and then turns to flow in a northwest direction to join southwest and northwest oriented Crow Creek in the figure 7 northwest corner. The south-oriented Missouri River can be seen along the figure 7 west edge. Chamberlain is the town located just west of the figure 7 southwest corner area. American Creek is the northwest and west oriented stream flowing to the Missouri River at Chamberlain. Note the large through valley linking the northwest oriented Smith Creek valley with the American Creek valley. Also, note the northwest oriented Smith Creek tributary flowing from the figure 7 southeast corner area to join the northwest oriented Smith Creek. Finally, refer back to figures 1 and 2 to see how this figure 7 map area relates to the east-oriented White River, which flows to the south-oriented Missouri River just south of Chamberlain. White River drainage basin evolution is discussed in the essays under White River on the sidebar category list. Prior to headward erosion of the Missouri River valley into the figure 7 map region immense east-oriented floods from the developing White River valley moved east across the figure 7 map area. The southeast-sloping erosion surface seen in figure 6 and again here in figure 7 probably formed as the north wall of an east-oriented valley carved by that White River drainage basin flood flow. At that time immense quantities of flood water were moving across the figure 7, both from the northwest along the present day southeast-oriented Missouri River valley-northwest-oriented Smith Creek-Crow Creek alignment seen in figure 6 and eastward along what is today the northwest- and west-oriented American Creek alignment. Headward erosion of the deep Missouri River valley first reached the figure 7 map area and beheaded east-oriented flow along the American Creek alignment. Flood waters on the west end of the beheaded flood flow route reversed flow direction and flowed northwest and west to erode the American Creek valley seen today. At the same time the reversed flow captured yet to be beheaded southeast-oriented flood flow moving on the present day Smith Creek alignment, and that captured flow eroded the through valley linking the Smith Creek and American Creek valleys. Headward erosion of the deep Missouri River valley then beheaded southeast-oriented flood flow on the Smith Creek alignment, causing a reversal of flood flow that created the present day northwest-oriented Smith Creek valley (and also the northwest-oriented Smith Creek tributary valley).

Red Lake area near Chamberlain, South Dakota

Figure 8: Red Lake area near Chamberlain, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates the Red Lake region south of the figure 7 map area and includes overlap areas with figure 7. The south-oriented Missouri River is located in the figure 8 west half. The Missouri River valley here is flooded by the Lake Francis Case, which is a large reservoir impounded behind Fort Randall Dam. The flood southeast-oriented Missouri River tributary valley in the figure west center edge area is the White River valley. Refer back to figure 1 to see that west of the figure 8 map area the White River is an east oriented river. Chamberlain is the town located along the Missouri River in the figure 8 northwest quadrant. Kimball is the town located along the Interstate highway near the figure 8 east edge. Red Lake is the swamp surrounded lake area just south of the Interstate highway in the figure 8 center area. American Creek is the northwest and west oriented stream flowing to the Missouri River as a barbed tributary at Chamberlain. The northwest-oriented Smith Creek tributary discussed in figure 7 is located in the figure 8 northeast corner area. The through valley linking the American Creek valley with the Smith Creek valley can be seen in the figure 8 north center and northeast quadrant area. Note how the entire figure 8 southeast region is today an erosion surface into which the deep Missouri River valley has been eroded. This erosion surface was formed by massive east and southeast oriented floods coming from the actively developing White River valley. Flood waters were probably flowing along what was then the southwest margin of a rapidly melting North American ice sheet and had eroded a deep valley headward from this area (the south wall of which is the present day Pine Ridge Escarpment (see essays under White River on sidebar category list). Elevation of this extensive figure 8 erosion surface is generally 50 or more meters lower than elevations of the higher level erosion surface seen in figure 6, which provides evidence that flood waters flowing southeast in the present day northwest-oriented Smith Creek channel were flowing to join the much more massive volumes of flood waters flowing across the figure 8 map area. The deep Missouri River valley eroded north to capture these massive ice marginal floods. Drainage routes seen today were formed as flood waters on the beheaded flood flow routes drained into the newly eroded and much deeper Missouri River valley.

Missouri Escarpment near Wessington Springs, South Dakota

Figure 9: Missouri Escarpment near Wessington Springs, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 leaves the Missouri River valley area and illustrates the Missouri Escarpment and Missouri Coteau near Wessington Springs and is located south and east from the figure 5 map area (there is no overlap). The town of Wessington Springs is located at the base of the east-facing Missouri Escarpment. East of the Missouri Escarpment is the south oriented James River lowland floor. The James River lowland originated as an immense south oriented ice-walled and bedrock-floored valley sliced into the surface of the rapidly melting North American ice sheet. The Missouri Escarpment is what remains of the ice-walled and bedrock-floored valley’s west wall. West of the Missouri Escarpment is the Missouri Coteau upland surface. The Missouri Coteau upland surface is where the south oriented ice-walled and bedrock-floored valley’s western ice wall once stood. The detached ice sheet remnant located on this Missouri Coteau upland surface area eventually melted and deposited whatever debris it contained. As seen in figure 5 above this Missouri Coteau upland surface area is isolated from Missouri Coteau upland surface further to the north. The south-oriented stream in the figure 9 southwest corner area is Smith Creek, which originates today in the Missouri Coteau area west of Wessington Springs. Smith Creek flows south and southwest along the Missouri Escarpment crest from this figure 9 region to enter the large northwest-oriented valley seen in figures 6 and 7. Figure 9 evidence suggests the south- and southwest-oriented Smith Creek valley may have originated at the same time the south-oriented James River lowland ice-walled and bedrock-floored valley originated. Immense supra glacial melt water floods were responsible for carving the James River lowland ice-walled and bedrock-floored valley. Those floods probably moved in a large-scale south-oriented supra glacial anastomosing channel complex to whatever ice marginal low areas existed. Flood flow east of the Missouri Escarpment was probably much greater than flood flow in channels west of the Missouri Escarpment, which resulted in the large south-oriented James River lowland ice-walled and bedrock-floored valley being carved. However, flood flow moving in channels west of the Missouri Escarpment was able to carve narrower and shallower ice-walled and (perhaps) bedrock-floored valleys, which are now routes used by Smith Creek, Crow Creek, and Elm Creek headwaters.

Platte Creek headwaters near White Lake

Figure 10: Platte Creek headwaters near White Lake. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 illustrates Platte Creek headwaters area near White Lake and is located south of the figure 9 map area and east of the figure 7 map area and there are no overlap areas with previous figures. White Lake is the lake located in the figure 10 west center area. The town of White Lake is located south of White Lake and is in the figure 10 southwest quadrant. The south-oriented valley extending from White Lake (the lake) to the figure 10 south edge is where Platte Creek originates. South of the figure 10 map area Platte Creek turns to flow in southwest direction to join the southeast-oriented Missouri River as a barbed tributary (see figure 1). The Missouri Escarpment crest is located northwest from White Lake and is facing southeast. The Missouri Coteau upland surface is located in the figure 10 northwest corner at the Missouri Escarpment crest. The Missouri Escarpment in this figure 10 map area is much more complicated than seen further north. While the upper Missouri Escarpment slope is facing southeast the lower slope is facing east-northeast. The north-northwest-south-southeast oriented lowland  located at the Missouri Escarpment base and near the figure 10 east edge is the south-oriented James River lowland. The upper Missouri Escarpment slope orientation and Platte Creek valley orientation (southwest of figure 10) suggest this figure 10 map area may be where a large ice marginal flood flowed around a decaying ice sheet remnant and into the lower elevation James River lowland ice-walled and bedrock-floored valley. Figure 10 evidence suggests the water may have been moving northeast at that time, which raises the possibility of north-oriented flood flow in the James River lowland ice-walled and bedrock-floored valley. If so, the flow direction was subsequently reversed to flow south to the actively eroding deep Missouri River valley, and the deeper south-oriented James River lowland valley was eroded. Why would water flow north in the James River lowland ice-walled and bedrock-floored valley? Further north, in southeast North Dakota the James River lowland is linked by through valleys with the present day north-oriented Red River valley. The Red River valley originated as an ice-walled and bedrock-floored valley, but was reversed when headward erosion of east- and north-oriented ice-walled and bedrock-floored valleys opened up shorter and/or steeper gradient routes to sea level (which probably was lower than it is today). Reversal of flow in the Red River valley could have captured and reversed flood flow in the James River lowland valley, although as already mentioned, south-oriented flood flow in the James River lowland resumed and eroded the James River lowland valley floor still lower than when northeast-oriented floods flowed across the figure 10 map area.

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.