A geomorphic history based on topographic map evidence

The James River-Big Sioux River drainage divide area north of Redfield and Watertown discussed here is located in northeast South Dakota, USA. The James River flows south in a broad lowland between the east-facing Missouri Escarpment, which marks the Missouri Coteau east boundary, and the west-facing escarpment, which marks the Prairie Coteau west boundary. The Big Sioux River originates on the Prairie Coteau upland surface and flows south. The James River lowland is interpreted to have originated as an immense ice-walled and bedrock-floored valley that was sliced in the surface of a rapidly melting thick North American ice sheet. The Missouri Coteau and Prairie Coteau are interpreted be where ice sheet remnants, on either side of the large south-oriented ice-walled and bedrock-floored valley, melted and deposited whatever debris they contained. The Big Sioux River is interpreted to have originated in a south-oriented ice-walled and ice-floored valley on the Prairie Coteau ice sheet remnant surface.

• The purpose of this essay is to use topographic map interpretation methods to explore James River-Big Sioux River drainage divide area landform origins north of Redfield and Watertown, 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 James River-Big Sioux River drainage divide area landform evidence north of Redfield and Watertown, 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.

James River-Big Sioux River drainage divide area location map

Figure 1 is a location map for the James River-Big Sioux River drainage divide area north of Redfield and Watertown, South Dakota. The state located along the figure 1 east edge area and east of the green boundary is Minnesota. West of Minnesota is the state of South Dakota, except along the figure 1 north edge, where a strip of southern North Dakota is located. The Missouri River is the large south and southeast-oriented river near the figure 1 west edge. The south-oriented James River flows from near Oakes, North Dakota (along the figure 1 north center edge) to near Mitchell (near the figure 1 south center edge). The south-oriented Big Sioux River is located east of the James River and flows from near Summit, South Dakota to Watertown and Brookings before flowing to the figure 1 south edge. Another river important to this discussion is the Minnesota River, which begins at Big Stone Lake in the figure 1 northeast quadrant and flows southeast in Minnesota to the figure 1 east center edge. Figure 1 does not show topography, but if it did it would show the James River flows south in a broad lowland between two escarpment bounded uplands. The east facing escarpment (located west of the James River lowland) is the Missouri Escarpment and at its crest is the Missouri Coteau. The western Missouri Coteau boundary is the Missouri River valley, although the thickness of the glacial moraines generally decreases as one approaches the Missouri River valley. The Missouri Coteau is an area of thick glacial moraines located between the Missouri Escarpment and the Missouri River. The west-facing escarpment is the western escarpment bounding the Prairie Coteau upland, which is also a region of thick glacial moraines. The Prairie Coteau east boundary is a prominent east and northeast-facing escarpment. The Minnesota River flows in a broad southeast-oriented lowland at the eastern escarpment base. The Big Sioux River originates on the Prairie Coteau upland surface and flows south on that upland surface. The Big Sioux River flows south to join the Missouri River near the South Dakota southeast corner. The James River also joins the Missouri River, although west of the Big Sioux River. The Minnesota River flows in a southeast direction across southern Minnesota before making an abrupt turn to the north to flow to the southeast-oriented Mississippi River at St. Paul, Minnesota (see figure 8a below). The James River-Big Sioux River drainage divide area discussed in this essay is located primarily south of US highway 12 (between Aberdeen and Milbank, South Dakota) and north of highway 212 (between Redfield and Watertown, South Dakota).

James River-Big Sioux River drainage divide area detailed location map

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

Figure 2 provides a somewhat more detailed location map for the James River-Big Sioux drainage divide area north of Redfield and Watertown, South Dakota. Brown, Spink, Day, Roberts, Clark, Grant, and Codington are names of South Dakota counties. The red shading identifies land areas in the Sisseton-Wahpeton Indian Reservation. Aberdeen is located in Brown County in the figure 2 northwest quadrant. Redfield is located in Spink County and is in the figure 2 southwest corner. Watertown is in Codington County and is located in the figure 2 southeast quadrant. The James River is located in Brown and Spink Counties, although it is somewhat east of Aberdeen and Redfield. The James River flows from the figure 2 north edge generally in a south-southwest direction almost to Redfield and then turns to flow in a southeast direction to the figure 2 south edge. The Big Sioux River originates north of Watertown and flows south to Watertown and then south to the figure 2 south edge. Note how there is a widening north-south band of numerous small lakes extending from the figure 2 north edge (near the west border of the Indian Reservation) southward to the figure 2 south edge. That widening north-south band of lakes is located on the Prairie Coteau upland, which is seen in detail in several of the figures below. James River tributaries generally begin along the west-facing escarpment bounding the Prairie Coteau upland and along the figure 2 east edge area Minnesota River tributaries begin along the Prairies Coteau northeast-facing escarpment. Note how James River tributaries, once they are away from the Prairies Coteau region, are generally south-oriented and often parallel the south-oriented James River for considerable distances. The south-oriented tributaries are flowing in the James River lowland, which is located between the west-facing Prairie Coteau escarpment and the east-facing Missouri Escarpment. The James River lowland is what remains of an immense southeast and south-oriented ice-walled and bedrock-floored valley carved by south-oriented supra glacial melt water rivers into a rapidly melting thick North American ice sheet. The Prairie Coteau upland to the east and the Missouri Coteau upland to the west represent where ice sheet walls on either side of this giant canyon once stood. Probably when first sliced into the thick ice sheet this southeast and south-oriented ice-walled canyon was comparable in size, if not larger, than any modern-day canyon on the Earth’s surface. As ice melting progressed, the height of the canyon walls decreased and eventually all that remained were deposits of debris that had been contained in those ice walls.

James River-Prairie Coteau drainage divide area near Groton, South Dakota

Figure 3: James River-Prairie Coteau drainage divide area near Groton, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 uses reduced size maps to illustrate the James River-Prairie Coteau drainage divide area near Groton, South Dakota. Groton, South Dakota is the town located in the figure 3 center. Andover is the town on the red highway  southeast of Groton and located near the Prairie Coteau escarpment base. Stratford, South Dakota is the small town in the figure 3 southwest corner (and is seen in more detail in figure 4 below). The west-northwest facing Prairie Coteau escarpment is located along the figure 3 east edge. An area of the Prairie Coteau upland can be seen in the figure 3 southeast corner. The wooded James River valley is located in the figure 3 northwest quadrant and the James River flows south from the figure 3 north edge before turning to flow south-southwest to the figure 3 southwest corner. Mud Creek is an interesting James River tributary and is located in the figure 3 south half between the James River and the Prairie Coteau upland. Mud Creek originates in the figure 3 southeast corner area on the Prairie Coteau upland edge and flows northwest down the Prairie Coteau west escarpment and into the broad James River lowland to join a south-southwest oriented tributary and then to flow south-southwest roughly parallel to the James River to the west. The James River lowland in this region is south-southwest oriented (the Missouri Escarpment orientation on the west also reflects this orientation). North of this region the James River lowland is much more north-south oriented and even further north in central North Dakota the lowland is southeast-oriented. The reason for this change in orientation is probably related to evidence seen further north (and illustrated in figure 5 below). As already described the James River lowland was carved by immense south-oriented melt water floods that sliced an ice-walled and bedrock-floored valley into a rapidly melting thick ice sheet. The south-southwest orientation of the present day James River and Mud Creek valleys (and Mud Creek tributary valley) probably was established during the final large melt water flood event. This final flood event probably eroded an anastomosing complex of channels into the floor of what was probably still an ice-walled and bedrock-floored valley or lowland. These valleys may be superposed on previous valleys, which were filled with flood transported debris. Note how the James River lowland region lacks evidence of the thick glacial moraines found on the adjacent (and higher elevation) Prairie Coteau.

Anastomosing channel complex along James River valley near Statford

Figure 4: Anastomosing channel complex along James River valley near Statford. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates some of the anastomosing channels in the Stratford, South Dakota area and is located in a region seen in less detail in figure 3. The James River is the south-southwest oriented river in the figure 4 west half. Mud Creek is the southwest-oriented stream in the figure 4 southeast quadrant. Note how a dry valley surrounds an erosional residual in the figure 4 southwest corner. Note also how the James River and Mud Creek valleys are linked by a complex of valleys northeast of Stratford. These valley complexes provide evidence the present day James River and Mud Creek valleys were eroded as channels in what was probably a large-scale anastomosing channel complex filling much, if not all, of the present day James River lowland region. Such an anastomosing channel complex is evidence of an immense south-oriented flood moving between what were probably the ice walls on either side of the south-oriented James River lowland. In some other essays the southeast and south-oriented ice-walled and bedrock-floored valley is named the Midcontinent Trench. This final flood event probably occurred as south-oriented flood flow in the Midcontinent Trench was being captured further to the north and being diverted east and north. Evidence for one such capture in southeast North Dakota is presented in the James River-Sheyenne River drainage divide area and James River-Wild Rice River drainage divide area essays (found under James River on the sidebar category list). Another capture occurred in north central North Dakota (see Souris River loop discussion in Missouri River-Souris River drainage divide area essay found under ND Missouri River on the sidebar category list). Additional captures and flood diversions occurred in Saskatchewan. These captures of immense south-oriented floods originally heading for the Gulf of Mexico and diversions of the flood water north to Hudson Bay and the Arctic Ocean significantly changed Atlantic Ocean currents, causing a major Northern Hemisphere cooling event, which ended the thick ice sheet rapid melt down. The cooling event may have frozen large quantities of north-oriented flood water on the former ice sheet floor (in ice-walled and bedrock-floored valleys like this one in South Dakota) and may have created a wet based thin ice sheet with remnants of the thick ice sheet embedded in it. If so, melting of the thin ice sheet and the remaining thick ice sheet remnants occurred gradually and did not trigger a new round of immense melt water flood events.

Prairie Coteau with east and west escarpments

Figure 5: Prairie Coteau with east and west escarpments. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates a Prairie Coteau region north of the Big Sioux River headwaters, but is shown to illustrate how the Prairie Coteau upland is bounded by escarpments on both the east and the west. The escarpments converge to north near the North Dakota and South Dakota border and north of that point there is no escarpment or upland region separating the south-oriented Midcontinent Trench from the lowland to the east of the Prairie Coteau. The southeast-oriented lowland east of the Prairie Coteau east facing escarpment is today the broad Minnesota River valley lowland. The lowland extends north along the North Dakota-Minnesota border, where it is drained by the present day north-oriented Red River. The eastern lowland also originated as another immense ice-walled and bedrock-floored valley moving large volumes of melt water to the present day south-oriented Mississippi River valley in eastern Iowa. The lack of a major barrier separating the south-oriented Midcontinent Trench from the Red River-Minnesota River lowland to the east suggests the two south-oriented ice-walled and bedrock-floored valleys intersected in what is today southeast North Dakota, and it is possible southeast-oriented flood water from the southeast-oriented Midcontinent Trench in northwest and central North Dakota split in southeast North Dakota, with some water moving south in the present day James River lowland and some of the water moving southeast along the present day Minnesota River alignment. This split of the south-oriented Midcontinent Trench melt water flood flow was altered when headward erosion of the south-oriented eastern ice-walled and bedrock-floored valley intersected with east and north-oriented ice-walled and bedrock-floored valleys providing shorter and steeper gradient routes to sea level. Those east and north-oriented ice-walled and bedrock-floored valleys caused a major reversal of flood flow in what is today the Red River valley. Water north of Big Stone Lake (see figures 1 and 2) was reversed to flow north, while water from the Big Stone Lake area and southeast continued to flow southeast. This reversal of flood flow in the Red River valley captured the east half of the south-oriented flood flow in the Midcontinent Trench and the Sheyenne River course in southeast North Dakota provides evidence of that capture (see James River-Sheyenne River drainage divide area essay). The Prairie Coteau area seen in figure 5 is typical of Prairie Coteau areas and was formed as the thick ice sheet remnant isolated by headward erosion of the two ice-walled and bedrock-floored valleys melted and deposited whatever debris it contained. Flood water removed most of the ice sheet transported debris from lowland areas on either side of the Prairie Coteau.

James River-Prairie Coteau drainage divide area in northern Clark County

Figure 6: James River-Prairie Coteau drainage divide area in northern Clark County. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates the James River-Prairie Coteau drainage divide area in northern Clark County and is located south of the figure 3 map area. The James River flows south-southwest in the figure 6 west half. The west-facing Prairie Coteau escarpment is located near the figure 6 east edge. Between the James River and the Prairie Coteau is the east half of the south-oriented James River lowland (or Midcontinent Trench valley). The west-to-east oriented county line is located in the figure 6 north half. The town at the intersection of west-oriented highway on the county line and the north-south red highway is Conde, South Dakota. Between Conde and the James River the town just north of the west-oriented highway is Brentford, South Dakota. The south-oriented stream east of Brentford is Dry Run, which extends from the figure 6 north edge to the figure 6 south edge. The south-oriented stream flowing just west of Conde is Timber Creek. Dry Run and Timber Creek are both tributaries to the James River (see figure 10 below). Timber Creek tributaries flow west from the Prairie Coteau, suggesting drainage routes from the west-facing Prairie Coteau escarpment may have developed independent of drainage routes on the James River lowland (or Midcontinent Trench) floor. West-oriented drainage routes flowing down the west-facing escarpment slope probably reflect drainage of melt water from the melting Prairie Coteau ice sheet remnant, which occurred after final flood events on the Midcontinent Trench floor. If so, the fact these drainage routes have not eroded headward into the Prairie Coteau upland surface suggests melting was gradual and did not produce immense melt water floods of the type that eroded the Midcontinent Trench ice-walled and bedrock-floored valley. Multiple south-oriented valleys on the Midcontinent Trench floor provides evidence of multiple channels. A close look at figure 6 reveals the south-oriented valleys are linked by dry valleys providing evidence of an anastomosing channel complex.

Big Sioux River headwaters near Summit, South Dakota

Figure 7: Big Sioux River headwaters near Summit, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Big Sioux River headwaters area on the Prairie Coteau upland surface and is east of the figure 3 map area. The town located south of Blue Dog Lake is Waubay, South Dakota. East of Waubay on the highway and near the figure 7 center is the small town of Ortley. Continuing east on the highway to the major highway interchange is the town of Summit. The Big Sioux River flows through the Ortley area to the figure 7 south center edge. The Big Sioux River originates in lakes in the figure 7 northwest quadrant and flows southeast and south past Ortley in the figure 7 center to the figure 7 south center edge. Unlike the James River, which for most of it course is flowing in what was an ice-walled and bedrock-floored valley the Big Sioux River originates and flows across the Prairie Coteau upland surface. The Big Sioux River course may have been established by a south-oriented ice-walled and ice-floored melt water flow valley on the isolated Prairie Coteau ice sheet remnant between the large south-oriented ice-walled and bedrock-floored valleys on either side. Melt water flood flow from the north to that south-oriented ice-walled and bedrock-floored valley was beheaded further to the north by headward erosion of the deeper and larger southeast-oriented Red River-Minnesota River ice-walled and bedrock-floored valley and Midcontinent Trench ice-walled and bedrock-floored valley. Lacking a large up glacier drainage basin the Big Sioux River ice-walled and ice-floored valley never obtained enough melt water to erode a large ice-walled and bedrock-floored valley, although there was enough melt water to maintain a south-oriented valley (versus developing east and west-oriented valleys to the adjacent, and deeper ice-walled and bedrock-floored valleys. The Prairie Coteau upland region as already mentioned is underlain by glacially transported debris that was probably simply deposited in place as the Prairie Coteau thick ice sheet remnant melted. Had there not been some sort of south-oriented ice-walled melt water flow route established before all ice melted it is unlikely a major south-oriented river would have originated and flowed south on this upland region. The alternative would be the Big Sioux River originated as a regional drainage route after the ice sheet remnants had melted. If so, it is hard to explain why the Big Sioux River flows south instead of east or west in the figure 7 map area.

Prairie Coteau-Minnesota River drainage divide east of Summit, South Dakota

Figure 8: Prairie Coteau-Minnesota River drainage divide east of Summit, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates the Prairie Coteau-Minnesota River drainage divide area east of Summit, South Dakota and is located east of figure 7. Summit is located in the figure 8 southwest quadrant. The lake in the figure 8 northeast corner is Big Stone Lake, which is where the southeast-oriented Minnesota River begins. The Big Stone Lake surface elevation is more than 250 meters lower than elevations on the Prairie Coteau upland surface and about 50-60 meters lower than elevations on the adjacent lowland surface into which the Big Stone Lake valley has been eroded. The southeast-oriented stream between the east-northeast facing Prairie Coteau escarpment and Big Stone Lake is the North Fork of the Whetstone River, which is a Minnesota River tributary. Note how the North Fork Whetstone River valley parallels the Big Stone Lake valley. The same type of evidence for multiple anastomosing channels is found east of the Prairie Coteau upland as is found west of the Prairie Coteau upland. In other words, lowlands on either side of the Prairie Coteau upland were eroded by immense south-oriented floods. Note how northeast-oriented streams drain the Prairie Coteau escarpment slope, but have not eroded valleys headward into the Prairie Coteau upland surface. This evidence further suggests the Big Sioux River course was established while ice was still on the Prairie Coteau upland surface. Figure 8a below illustrates southern Minnesota and the Minnesota River route downstream from the Big Stone Lake area. Note how the Minnesota River flows southeast to Mankato and then makes an abrupt turn to flow northeast to St. Paul. At St. Paul the Minnesota River joins the southeast-oriented Mississippi River. Note also that at Mankato the Minnesota River is joined by a northwest-oriented tributary. The southeast-oriented Minnesota River is flowing roughly parallel to the orientation of the northwest-southeast oriented northeast-facing Prairie Coteau escarpment, although the escarpment base is located along a line going through Marshall and Sanborn, Minnesota. The present day southeast-oriented Minnesota River route defines the location of a large southeast-oriented ice-walled and bedrock-floored valley that once extended north along the present day Red River alignment (along the North Dakota-Minnesota border north of figure 8a) and connected with the southeast-oriented Midcontinent Trench valley in southeast North Dakota (northwest of figure 8a). The northeast-facing Prairie Coteau escarpment is what remains of that southeast-oriented ice-walled and bedrock-floored valley’s southwest wall. Water in that huge southeast-oriented valley originally moved across southern Minnesota and northeast Iowa directly to the south-oriented Mississippi River. However, an ice-walled and bedrock-floored tributary valley eroded north into the decaying ice sheet (along the present day northeast-oriented Minnesota River alignment) and intersected with the southeast-oriented Mississippi River valley (which probably was located in a deeper ice-walled and bedrock-floored valley). The result was the southeast-oriented Mississippi River at St. Paul captured flood flow from the Minnesota River flood flow route, causing a reversal of flood flow in the present day northeast-oriented Minnesota River valley segment (and also in the valley of the northwest-oriented Minnesota River tributary, which joins the Minnesota River at Mankato).

Figure 8a: Minnesota River route downstream from the Big Stone Lake area. National Geographic Society map digitally presented using National Geographic Society TOPO software.

Big Sioux River valley near Watertown, South Dakota

Figure 9: Big Sioux River valley near Watertown, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Big Sioux River valley in the Watertown, South Dakota area. The figure 9 location is on the Prairie Coteau upland surface and the Big Sioux River flows from the figure 9 north center edge south and southeast to Watertown and then southeast to Sheridan Township and the figure 9 south edge. Willow Creek is a Big Sioux River tributary, which flows in a southwest direction from the figure 9 east center edge area to join the Big Sioux River south of Watertown. The Big Sioux River also gains water from the Lake Kampseka outlet. Mud Creek is another southwest-oriented Big Sioux River tributary joining the Big Sioux River near Lake Kampseka. The area along the figure 9 east edge is approximately 70-80 meters higher than the Big Sioux River valley area, although the area west of the Big Sioux River valley is generally only 20-30 meters higher than the Big Sioux River valley. There are several lakes in the area west of the Big Sioux River, suggesting the region is underlain by glacial moraines. While the figure 9 east area does not show any lakes there are lakes just east of the figure 9 map area. Based on that observation the figure 9 region is interpreted to underlain by thick glacial moraines and the lakes are interpreted to be locations where large blocks of ice buried in glacially deposited debris melted and left depressions. As previously mentioned the Big Sioux River route probably was established, at least to some degree, while ice was still present in the figure 9 map region. Both to the east and west of the figure 9 map area are escarpments leading to significantly lower regions. It is unlikely that a melting ice sheet remnant would deposit whatever debris it carried in such a way that the logical drainage route for the Prairie Coteau upland surface would be south when much steeper gradient routes existed on either side. However, unlike the James River and Minnesota Rivers to the west and east, the Big Sioux River did not develop in what was a broad ice-walled and bedrock-floored valley. The ice-walled and ice-floored (and maybe bedrock-floored) early Big Sioux River valley was much narrower. and while probably moving significant melt water volumes, never experienced the immense melt water floods, which moved south in the James River lowland (Midcontinent Trench) and the southeast-oriented Minnesota River lowland.

James River-Prairie Coteau drainage divide area northeast of Redfield

Figure 10: James River-Prairie Coteau drainage divide area northeast of Redfield. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 illustrates the James River-Prairie Coteau drainage divide area northeast of Redfield, South Dakota and includes significant overlap areas with figure 6. Redfield is located in the figure 10 southwest corner. The James River flows in a south-southwest direction from the figure 10 north edge almost to Redfield, and just north of Redfield turns to flow in a southeast direction to the figure 10 south edge. The stream flowing through Redfield is north-oriented Turtle Creek and originated when flow was reversed in south-oriented flood flow channels by headward erosion of the deeper James River valley channel. East of the south-southwest oriented James River valley is the south-oriented Dry Run valley, which joins the southeast-oriented James River in the figure 10 southwest quadrant. East of Dry Run is south-oriented Timber Creek, which joins the southeast-oriented James River south of the figure 10 south center edge. The south-oriented James River, Dry Run, and Timber Creek valleys all originated as channels in a large south-oriented anastomosing channel complex eroded into the James River lowland (or Midcontinent Trench) floor and provide evidence of an immense south-oriented flood flow event late during the thick ice sheet’s rapid melt down. The scale of the anastomosing channel complex is so large that it may not be easily recognized. However, to better recognize an anastomosing channel complex figure 10a below illustrates an anastomosing channel complex region near Redfield. In figure 10a the south- and southeast-oriented stream with the wooded valley is the James River, which is turning from flowing in a south-southwest direction to flowing in a southeast direction. The northeast and north-oriented stream flowing through Redfield is Turtle Creek. Note in figure 10a the multiple southeast-oriented through valleys and streamlined erosional residuals. This landscape provides evidence of a significant southeast-oriented flood flow event moving across the region. This southeast-oriented flood flow event appears to have captured south-southwest oriented flood flow, which suggests flood waters from two different sources were coming together in this region. The south-southwest oriented flood flow was probably moving in the Midcontinent Trench (or James River lowland) from North Dakota into the region. The southeast-oriented flood flow may have been coming from ice-marginal floods that had breached the decaying ice sheet’s southwest margin. Evidence west of the James River valley needs to be studied in future essays.

Figure 10a. Anastomosing channel complex near Redfield, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

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.