A geomorphic history based on topographic map evidence

The Missouri River-Sheyenne River drainage divide area discussed here is located in central North Dakota, USA. Major landforms present include the Missouri Escarpment and the Missouri Coteau. The Sheyenne River originates near a major indentation in the Missouri Escarpment at Lincoln Valley. Landforms in the drainage divide area formed during a thick North American ice sheet’s rapid melt down. Thick ice sheet rapid melting produced immense floods, which late during the ice sheet melt down history flowed from the present day Missouri River valley to the Sheyenne River valley. This melt water flood flow was blocked when a significant climate change halted ice sheet melting, blocked the Lincoln Valley flood flow route, and forced remaining flood waters to flow south, which eroded the present day Missouri River valley.

• The purpose of this essay is to use topographic map interpretation methods to explore Missouri River-Sheyenne River drainage divide area landform origins in central North 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-Sheyenne River drainage divide area landform evidence in central North 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-Sheyenne River drainage divide area location map

Figure 1: Missouri River-Sheyenne 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 Missouri River-Sheyenne River drainage divide area location map and illustrates a large region in central North Dakota.  The Missouri River flows from Lake Sakakawea in the figure 1 west center area to Bismarck and then to the figure 1 south edge. Lake Sakakawea is a large reservoir flooding the Missouri River valley upstream from Garrison Dam. Note how the Missouri River segment immediately upstream from Garrison Dam is east-oriented and the segment downstream from Garrison Dam is south-southeast oriented. The Sheyenne River originates in the figure 1 center and flows east and northeast to Harvey. From Harvey the Sheyenne River flows northeast and east-southeast before turning to flow south to Valley City and Fort Ransom (in the figure 1 southeast corner). At Fort Ransom the Sheyenne River begins to make a U-turn before reaching the figure 1 east edge. East of figure 1 the Sheyenne River flows in a northeast direction to join the north-oriented Red River and Sheyenne River water eventually reaches Hudson Bay.

• Southeast of the Sheyenne River at Harvey is the northeast-, southeast-, and south-oriented James River, which unlike the Sheyenne River continues to flow south and in southern South Dakota joins the southeast-oriented Missouri River. Note how the Sheyenne and James Rivers are very close together in the Harvey area, yet water in the two rivers flows to opposite sides of the North American continent. Another regional river worthy of mention here is the Souris (or Mouse) River which originates in Canada and flows  southeast to Minot and Velva, North Dakota. At Velva the Souris River turns to flow northeast and then northwest to the Canadian border. Souris River water eventually reaches Hudson Bay. Note also the Knife River, which flows northeast to join the south-southeast oriented Missouri River just south of Garrison Dam. Essays illustrating and discussing evidence north and west of this essay’s study region include the Missouri River-Des Lacs River drainage divide area essay, the Knife River drainage basin essay, and the Missouri River-Souris River drainage divide area essay, all of which can be found under ND Missouri River on the sidebar category list.

• This essay uses topographic maps to illustrate and describe how the Missouri River and Sheyenne River are related to the Missouri Coteau and Missouri Escarpment, which are two prominent landforms not identified in figure 1, but which can be identified on detailed topographic maps below. The interpretation provided by this Missouri River drainage basin research project series is fundamentally different from interpretations provided by previous researchers and is based almost entirely on topographic map evidence. The Missouri Coteau briefly is a region of hummocky topography and numerous small lakes and depressions located between the Missouri River and the northeast-facing Missouri Escarpment slope. Missouri Coteau area drainage is often to local depressions or small lakes, although southwest areas of the Missouri Coteau region drain to the Missouri River. The Missouri Coteau is interpreted here as being covered by glacial deposits left by decaying remnants of what had been a rapidly melting thick North American ice sheet that had occupied a deep “hole”. The lowland at the Missouri Escarpment base is referred to here as the Midcontinent Trench, which was eroded by an immense southeast and south-oriented glacial melt water river. The immense river, which originated on the thick ice sheet’s surface, is here named the Midcontinent River. The Missouri Escarpment is interpreted to have been formed as the Midcontinent Trench’s southwest wall or the southwest wall of what at one time was the Midcontinent River’s ice-walled and bedrock-floored valley.

Missouri River-Sheyenne River drainage divide area detailed location map

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

Figure 2 provides a more detailed map of the Missouri River-Sheyenne River drainage divide area. McLean, Pierce, Sheridan, Ward, and Wells Counties are located in North Dakota. McHenry County is the unnamed county between Ward and Pierce Counties. Lake Sakakawea is a large reservoir impounded behind Garrison Dam (located in the figure 2 southwest quadrant). Upstream from Garrison Dam the flooded Missouri River valley is east-oriented. Downstream from Garrison Dam the Missouri River is south-southeast and southeast oriented, which means the Missouri River makes an abrupt direction change immediately upstream from Garrison Dam. Note the large west-oriented flooded valley northeast of Garrison Dam. East of the highway (which crosses that Lake Sakakawea arm) is Lake Audubon, which includes a northwest oriented arm in the Audubon National Wildlife Refuge area. That flooded northwest-oriented valley provides important evidence about the Missouri River history. The Sheyenne River originates near the Sheyenne Lake National Wildlife Refuge in northeast Sheridan County and flows southeast and northeast to Harvey (located in northwest Wells County). From Harvey the Sheyenne River continues to flow northeast to the figure 2 east edge. Parallel to the northeast oriented Sheyenne River in Wells County (just south of Harvey) is the northeast, northwest, northeast and southeast-oriented James River, which turns southeast at the highway leading from Harvey to Manfred. As previously mentioned, water in the Sheyenne River after flowing to southeast North Dakota, makes a U-turn and flows north to eventually reach Hudson Bay. Water in the James River, after flowing on a route roughly paralleling the Sheyenne River route to southeast North Dakota, continues to flow south and reaches the Missouri River in southern South Dakota and eventually reaches the Gulf of Mexico. As will be seen on topographic maps below there is no high drainage divide separating these two drainage routes. The road from Harvey (where the Sheyenne River is crossed) is almost flat to the location where the James River is crossed. Another interesting figure 2 is the McClusky Canal, which on figure 2 appears to begin in eastern McLean County (south of Turtle Lake) and heads southeast before turning north-northeast just south of Sheridan County and continues in a north-northeast direction in Sheridan County (near McClusky and Lincoln Valley) to an area west of the Sheyenne Lake National Wildlife Refuge. Detailed maps below will show the McClusky Canal begins at Lake Audubon and continues to the Sheyenne River valley. The McClusky Canal is an irrigation canal that moves water from Lake Audubon across the Missouri Coteau to the lower elevation Sheyenne River and James River valleys at the Missouri Escarpment base and roughly follows the route of former east-oriented valley, now largely blocked by glacially deposited debris. Headward erosion of the south-southeast and southeast-oriented Missouri River valley south of Garrison Dam appears to have captured the east-oriented river that once flowed through that valley.

Missouri River valley near Garrison Dam

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

Figure 3 illustrates the Missouri River valley near Garrison Dam. Garrison Dam is located in the figure 3 southwest quadrant and the south-southeast oriented Missouri River valley is located downstream from the dam. The Missouri River valley upstream from the dam is today flooded by Lake Sakakawea. Note how the lake floods a large west-oriented valley. The highway crossing the lake serves as barrier separating the  eastern section of that flooded valley from the main Lake Sakakawea body of water. The section of the flooded valley east of the highway is known as Lake Audubon and there is a pumping plant (located at the north end of the highway embankment), which when necessary can pump water from Lake Sakakawea (which can fluctuate in elevation) to Lake Audubon (which usually is maintained at a constant level). The flooded west-oriented valley is the west end of what was once an east-oriented valley. Figures 7 and 8 below illustrate the valley east end where it has cut into the northeast-facing Missouri Escarpment slope. Evidence of the valley between the two ends is more subtle. To understand the Missouri River valley relationship to this one time east-oriented valley it is necessary to understand the Missouri Coteau, which is located north and east of the Missouri River. Today the Missouri Coteau is a region of hummocky topography, with numerous small lakes, and on topographic maps has the appearance of being a glacial moraine area. The Missouri Coteau is a major topographic feature extending in a northwest-southeast direction from east central Alberta across Saskatchewan to central North Dakota. In Canada the Missouri Coteau type areas are located immediately southwest of a northeast-facing escarpment equivalent to the Missouri Escarpment seen in this essay. In North Dakota the Missouri Coteau is located immediately to the northeast of the Missouri River valley and southwest of the northeast-facing Missouri Escarpment. In central North Dakota the Missouri Coteau and the Missouri Escarpment orientation change from being northwest-southeast oriented to being much more closely north-south oriented. That direction change maintains the same relationship with the Missouri River valley, because as seen in figure 3 above the Missouri River valley changes direction from being southeast and east-oriented to being south-southeast and south-oriented (see figure 1 to obtain a big picture view).

• To understand this east-oriented valley and why headward erosion of the south-southeast oriented Missouri River valley was able to captured it this essay needs to explain how the deep glacial erosion paradigm used in this Missouri River drainage basin research project essay series interprets the Missouri Coteau and the Missouri Escarpment origins. The Missouri Escarpment and Missouri Coteau history are closely related to the history of a thick North American ice sheet (comparable in thickness to the present day Antarctic Ice Sheet) that rapidly melted. The thick North American ice sheet developed on a topographic surface now represented by high level Rocky Mountain erosion surfaces (if the topographic surface on which the thick North American ice sheet developed has been preserved at all). A deep North American “hole” was created by the thick ice sheet weight, which caused crustal down warping. In addition, deep glacial erosion probably further deepened ice sheet’s deep “hole”. Over time a considerable per cent of the ice sheet came to be located at elevations significantly below the ice sheet rim elevation, although a significant per cent of the ice sheet mass probably stood high above the ice sheet rim elevation. Exactly where this ice sheet’s southwest rim was located probably cannot be determined, because the rim has since been deeply eroded by melt water flood erosion. At some point in the ice sheet’s history the thick ice sheet began to melt faster than new ice was being formed.

• When the thick ice sheet rapid melt down began melt water rivers developed on the ice sheet surface. These supra-glacial rivers carved ice-walled and ice-floored valleys into the ice sheet surface, which eroded headward just as small gullies erode headward into unconsolidated clays. Over time some ice-walled and ice-floored river valleys developed extensive supra-glacial drainage networks. During periods of intense melting these supra-glacial rivers became immense melt water flood routes. Such melt water floods flowing to the ice sheet’s southern margin eventually flowed to the Gulf of Mexico and significantly eroded the landscape between the thick ice sheet’s southern margin and the Gulf of Mexico. In time melting progressed to the point where some ice-walled and ice-floored valleys became ice-walled and bedrock-floored valleys. One such giant ice-walled and bedrock-floored valley was carved by an immense southeast and south-oriented melt water river, named here as the Midcontinent River, which at its peak flowed from east central Alberta southeast through Saskatchewan to central North Dakota, where it turned to flow south to southern South Dakota. The Midcontinent River ice-walled and bedrock-floored valley (or canyon) is here named the Midcontinent Trench, and the Missouri Escarpment was eroded at the base of the Midcontinent Trench’s southwest and west wall.

• The Midcontinent Trench detached the thick ice sheet’s southwest margin in South Dakota, North Dakota and Saskatchewan. The detached ice sheet margin is named here as the Southwest Ice Sheet and its northeast edge was located at the Missouri Escarpment crest. The Southwest Ice Sheet was an immense ice wall between melt water floods moving along the Southwest Ice Sheet’s southwest margin and on the Midcontinent Trench valley floor to the east and northeast. In time the Southwest Ice Sheet melted and whatever debris contained within that detached ice mass was deposited forming the present day Missouri Coteau. Melt water flood erosion along the Southwest Ice Sheet’s southwest and west margin removed much of that debris, although closer to the Missouri Escarpment, where that ice marginal melt water flood erosion was not as intense, debris deposited by the melting Southwest Ice Sheet still remains. In places the ice-marginal floods broke through the Southwest Ice Sheet ice wall barrier and eroded ice-walled and bedrock-floored valleys to the lower Midcontinent Trench floor located to the northeast and east. The east-oriented valley extending east from the Lake Audubon was initiated as one such ice-walled and bedrock-floored flood flow valley.

McClusky Canal in Turtle Lake area

Figure 4: McClusky Canal in Turtle Lake area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates the Turtle Lake area east of Lake Audubon and includes overlap areas with figure 3. The eastern tip of Lake Audubon is located in the figure 4 northwest corner. The McClusky Canal begins in the figure 4 northwest corner at Lake Audubon and extends generally eastward to north of the town of Turtle Lake. East of Turtle Lake the McClusky Canal turns south and south-southwest to make use of a south-southwest oriented valley parallel to the south-oriented Turtle Creek valley. South of figure 4 the McClusky Canal leaves the south-southwest oriented valley to head east and northeast across the Missouri Coteau while the south-southwest oriented valley joins the Turtle Creek valley. Turtle Creek then flows south and south-southwest to join the south-southeast oriented Missouri River. In the figure 4 southwest quadrant there is another south-oriented valley (Coal Lake Coulee). The presence of these south-oriented valleys is evidence headward erosion of the south-southeast oriented Missouri River valley captured multiple south-oriented flood flow routes along the Missouri Coteau west edge prior to eroding north in the deep valley now occupied by Garrison Dam (see figure 3). In other words, the eastward flow of ice marginal flood waters to the Midcontinent Trench east of the figure 4 map area for some reason was blocked and flood waters were forced to flow south. Initially flood waters moved south along the Southwest Ice Sheet west margin in multiple (and probably anastomosing) channels. Headward erosion of the deep Missouri River valley captured the south-oriented flood flow and consolidated that flood flow in one large channel. Why would melt water floods move south along the Southwest Ice Sheet’s west margin when there was an ice-walled and bedrock-floored valley that could move the flood waters northeast to the deeper Midcontinent Trench floor? Probably the best explanation is the thick ice sheet rapid melt down ended when a sudden climate change froze flood waters on the thick ice sheet floor and reinvigorated thick ice sheet remnants (such as the detached Southwest Ice Sheet). Shortly before that time the south-oriented Midcontinent River had been captured by new north-oriented ice-walled and bedrock-floored valleys and the immense melt water floods that had been moving south to the Gulf of Mexico were diverted north to Hudson Bay. Evidence for one such capture is seen in figure 9 below.This change in flood flow direction triggered a major climate change and caused Northern Hemisphere cooling. The resulting freezing of flood waters and reinvigorating of the Southwest Ice Sheet effectively blocked flood waters still south and west of the Southwest Ice Sheet from moving east to the Midcontinent Trench floor. Flood waters instead had to flow south along the Southwest Ice Sheet west margin (i. e. where that west margin was located at that time). This change in flood water flow direction resulted in the erosion of the present day Missouri River valley along the Southwest Ice Sheet west margin.

Prophets Mountains northeast of Mercer, North Dakota

Figure 5: Prophets Mountains northeast of Mercer, North Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Prophets Mountains area northeast of Mercer, North Dakota and is located east of figure 4. The north-northeast oriented McClusky Canal is located in the figure 5 southeast quadrant and extends from the figure 5 south edge to the figure 5 east center edge area. The numerous small lakes are typical of Missouri Coteau topography and suggest the presence of underlying glacial moraine materials. The Prophets Mountains area northeast of Mercer appear to be north-south linear ridges similar to hogback ridges. These might be a series of ice thrust structures. If so, the ice thrusting probably required a wet based thin ice sheet, not the thick ice sheet interpreted to have formed the Missouri Coteau. Why would landscape features associated with wet based thin ice sheets be present in the Missouri Coteau region, which has been interpreted here to have been formed by decaying thick ice sheet remnants? The figure 4 discussion described how during most of the thick ice sheet rapid melt down melt water floods moved to the Gulf of Mexico. As the thick ice sheet melt down progressed melt water flood flow routes changed with flood waters being directed into the “hole” the ice sheet had occupied when the ice sheet elevation fell below the ice sheet rim elevation. However, even after flowing northeast into the “hole” the flood waters, until very late during the melt down history, turned to flow south on the former ice sheet floor (in giant ice-walled and bedrock-floored river valleys, such as the Midcontinent Trench). Very late during the thick ice sheet melt down these immense south-oriented melt water flood rivers were captured and diverted north (see evidence in figure 9 below). The sudden change in flood water flow from the Gulf of Mexico to Hudson Bay significantly altered Atlantic Ocean currents. Instead of moving warm tropical water north to warm Northern Hemisphere climates the Atlantic Ocean currents began to move cold Arctic region waters south to cool Northern Hemisphere climates. This sudden Northern Hemisphere cooling stopped the thick ice sheet rapid melt down and also froze melt water floods on the former ice sheet floor. In addition, immense ice marginal floods still south and west of the thick ice sheet southwest margin were headed northeast into the “hole” the thick ice sheet had once occupied. As those flood waters entered the “hole” and began to flow north they also froze. The result was rapid formation of a wet based thin ice sheet with reinvigorated remnants of the former thick ice sheet embedded in it. Some of the frozen flood waters included frozen slabs of what had been underlying water saturated bedrock. Subsequently, when for various reasons the wet based thin ice sheet moved, the attached frozen slabs of underlying bedrock also moved and in some cases were piled up against each other. The Prophets Mountains area probably provides evidence of such wet based thin ice sheets and also of such thin ice sheet movements.

McClusky Canal south of Mercer, North Dakota

Figure 6: McClusky Canal south of Mercer, North Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates the McClusky Canal route south of the figure 5 map area and includes overlap areas with figure 5. The McClusky Canal is southeast-oriented in the figure 6 southwest quadrant and in the figure 6 south center turns east and northeast and then heads north to the figure 6 northeast quadrant and north edge. The McClusky Canal has been constructed to follow what is one of the lowest elevation routes across the Missouri Coteau. This low elevation route is probably related to one or more ice-walled and bedrock floored valleys that once carried ice marginal floods from southwest of the Southwest Ice Sheet eastward to the lower elevation Midcontinent Trench floor. One such valley probably extended east from the Lake Audubon area and was eroded by east-oriented flood waters that eroded the east-oriented Missouri River valley segment upstream from Garrison Dam. That east-oriented Missouri River valley segment was probably related in some way to headward erosion of the east-oriented Little Missouri River valley segment in western North Dakota (see essays under Little Missouri River on sidebar category list). Another such valley may be related to the northeast-oriented Knife River, which today flows as a barbed tributary to the south-southeast oriented Missouri River just south of Garrison Dam (see figure 1 and Knife River drainage basin essay). Probably the northeast-oriented Knife River valley once extended northeast as an ice-walled and bedrock-floored valley across the Southwest Ice Sheet ice wall to the deeper Midcontinent Trench floor on the thick ice sheet floor. Precise locations of these former valleys across the Missouri Coteau probably cannot be determined from topographic map evidence alone, although topographic map evidence does make a strong case for the existence of one or more such valleys. The McClusky Canal route has been designed so irrigation water can flow freely by gravity from Lake Audubon across the Missouri Coteau. So as the McClusky Canal proceeds eastward the elevation is gradually becoming lower. The McClusky Canal route north of figure 6 was shown in figure 5 above. Figure 7 below illustrates the McClusky Canal route north and east of figure 5.

McClusky Canal north of McClusky, North Dakota

Figure 7: McClusky Canal north of McClusky, North Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the McClusky Canal route north of McClusky, North Dakota and north and east of figure 5 (figure 7 includes overlap areas with figure 5). McClusky, North Dakota is located in the figure 7 southwest quadrant. The McClusky Canal enters the figure 7 map area in the southwest corner and heads northeast and north-northeast to the figure 7 north edge. Note how the northeast and north-northeast oriented McClusky Canal is entering what appears to be a large northeast-oriented valley. The McClusky Canal had been following that valley further to the south and west, although the valley was not as obvious as it is in figure 7. Note how the northeast-oriented valley today does show evidence of being partially filled with glacial moraine materials. Those moraine materials provide evidence of a glacial event after the valley was eroded. However, the glacial event responsible for depositing those glacial moraine materials did not significantly erode the figure 7 map area (otherwise evidence of the northeast-oriented valley would have been destroyed). For that reason the subsequent glacial event was probably minor compared to the much more significant earlier glacial event. The northeast-oriented valley was carved as an ice-walled and bedrock-floored valley across the Southwest Ice Sheet by flood waters moving from southwest of the Southwest Ice Sheet to the Midcontinent Trench on the former thick ice sheet floor. Today the northeast-oriented valley is a large indentation in the otherwise northeast-facing Missouri Escarpment slope (to see the Missouri Escarpment slope without such an indentation (see the Missouri River-Souris River drainage divide area essay). South of Kindschi Lake (located in the figure 7 north center) is a high area consisting of what might be more ice-thrust slabs similar to those in the Prophets Mountains area (figure 5). If so, these ice thrust slabs are located along the southeast wall of a northeast-oriented valley, which suggests flood waters and saturated underlying bedrock froze in and near the valley walls and then were lifted by subsequent ice movements. If ice responsible for the ice thrusting was frozen flood water, freezing probably was from the top down, which means in deeper water areas there was still liquid water under the ice surface. That underlying liquid water probably played a significant role in subsequent ice movements that lifted the frozen bedrock slabs into positions seen today.

McClusky Canal in Lincoln Valley

Figure 8: McClusky Canal in Lincoln Valley. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates the McClusky Canal in the northeast oriented Lincoln Valley north of the figure 7 map area and includes overlap areas with figure 7. The town located in the figure 8 southeast quadrant is Lincoln Valley, which provides a name for the northeast oriented valley seen in figure 7. The McClusky Canal heads northeast from the figure 8 south center edge to join the east-oriented Sheyenne River in the figure 8 northeast quadrant. Note how the Sheyenne River originates in the figure 8 northwest quadrant and flows generally east across the figure 8 map area. Note how the Sheyenne River headwaters are closely related to the Lincoln Valley location, providing evidence the Sheyenne River valley downstream from the figure 8 area may once have carried water that flowed northeast through the now blocked Lincoln Valley. The northeast-facing escarpment slope in the figure 8 northwest quadrant is the Missouri Escarpment slope. As previously mentioned the northwest-southeast oriented northeast-facing Missouri Escarpment extends from east central Alberta to central North Dakota. In central North Dakota the Missouri Escarpment becomes a north-south oriented feature and extends south from central North Dakota to southern South Dakota. The northeast-oriented Lincoln Valley seen in figures 7 and 8 is one of several similar northeast- and east-oriented valleys cut into the otherwise continuous Missouri Escarpment. Northeast of the Missouri Escarpment is the northwest-southeast oriented Midcontinent Trench, which was formed originally as an immense northwest-southeast oriented ice-walled and bedrock-floored canyon when headward erosion of the Midcontinent River sliced its ice-walled and bedrock-floored valley into the rapidly melting thick North American ice sheet. Headward erosion of that immense ice-walled and bedrock-floored Midcontinent Trench canyon for all practical purposes detached the rapidly melting ice sheet’s southwest margin (or Southwest Ice Sheet). Headward erosion of Midcontinent River tributary valleys, such as the northeast-oriented Lincoln Valley seen here in figure 8, carved what were probably narrow ice-walled and bedrock-floored valleys across the ice sheet’s southwest margin and further broke up the Southwest Ice Sheet (headward erosion of Midcontinent River tributary ice-walled and bedrock-floored valleys further to the north and east were also chopping the rapidly melting thick ice sheet up into smaller detached ice sheet masses. This process of chopping up the thick ice sheet further accelerated the ice sheet melting.

Wintering River-Sheyenne River drainage divide northeast of Missouri Escarpment

Figure 9: Wintering River-Sheyenne River drainage divide northeast of Missouri Escarpment. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 uses greatly reduced size topographic maps to illustrate the Wintering River-Sheyenne River drainage divide area northeast of the Missouri Escarpment and includes overlap areas with figure 8. The Sheyenne River originates on the Missouri Escarpment slope in the figure 9 south center area and flows east to northwest-southeast oriented Sheyenne Lake and southeast to the figure 9 southeast corner area. The Wintering River is just barely seen along the figure 9 north center edge area where it flows southeast into the figure 9 map area and then immediately makes a U-turn to flow northwest near Bentley Lake (located just south of the red highway at the figure 9 north edge). The southeast and northwest-oriented Wintering River flows to the southeast and northwest-oriented Souris River illustrated and mentioned in figure 1. The northwest-southeast oriented Missouri Escarpment is the northeast-facing slope in the figure 9 west center area and is broken by the Lincoln Valley indentation in the figure 9 south center. Southwest of the Missouri Escarpment is the Missouri Coteau (located in the figure 9 southwest quadrant), which is characterized on figure 9 by many small lakes. Northeast of the Missouri Escarpment slope is the Midcontinent Trench floor, which today serves as the Wintering River-Sheyenne River drainage divide. The Midcontinent Trench as described previously originated as an immense southeast and south-oriented ice-walled and bedrock-floored valley sliced into the rapidly melting thick North American ice sheet. North and northwest of the figure 9 map area the Midcontinent Trench had ice-walled and bedrock-floored tributary valleys that eroded headward in a north-oriented direction. Southeast of the figure 9 map area the Midcontinent Trench intersected with other south-oriented ice-walled and bedrock-floored valleys in southeast North Dakota. In time headward erosion of the south-oriented ice-walled and bedrock-floored valleys intersected with north-oriented ice-walled and bedrock-floored valleys being sliced headward from the thick ice sheet’s north margin. Those intersections resulted in massive flood flow reversals, with the south-oriented flood waters being captured and diverted to flow north. One such capture occurred just north of the figure 9 map area and caused southeast-oriented flood waters to be captured and diverted north to Hudson Bay. Note on figure 1 how the Souris River makes a U-turn in north central North Dakota. The Wintering River in figure 1 is the unnamed Souris River tributary flowing through Karlsruhe and makes a similar U-turn near Bentley Lake (see also figure 2). At the time that capture occurred ice marginal flood waters from southwest of the Southwest Ice Sheet were flowing east and northeast through the Lincoln Valley ice-walled and bedrock-floored valley into the Midcontinent Trench. Being downstream from the capture location flood waters moving through the Lincoln Valley breach continued to flow east and then southeast to the Sheyenne River and James River valleys seen in figure 10 below.

Sheyenne River-James River drainage divide northeast of Missouri Escarpment

Figure 10: Sheyenne River-James River drainage divide northeast of Missouri Escarpment. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 uses greatly reduced topographic maps to illustrate the Sheyenne River and James River valleys northeast of the Missouri Escarpment and is located southeast of figure 9 (and includes overlap areas with figure 9). The northeast-facing Missouri Escarpment slope can be seen in the figure 10 south center area. To the west in the figure 10 southwest quadrant is the northeast-oriented Lincoln Valley. The Sheyenne River flows east from the figure 10 west edge area to northwest-southeast oriented Sheyenne Lake (located in figure 10 west center area) and then southeast to the Missouri Escarpment base where it makes an abrupt turn to flow northeast to Harvey, North Dakota (located on the highway in the figure 10 northeast quadrant) and then to flow to the figure 10 northeast corner. The James River flows north in the figure 10 southeast quadrant to the red highway and then makes an abrupt turn to flow southeast along the highway to Manfred, North Dakota and then to the figure 10 east edge. Note an unnamed James River tributary, which flows northwest along the Missouri Escarpment base towards the southeast-oriented Sheyenne River segment, and then abruptly turns northeast to flow to the north and southeast-oriented James River. What is remarkable about these two rivers is they flow to opposite sides of the North American continent. As shown in figure 1 from the figure 10 map area the Sheyenne River flows east and then south before making a U-turn in southeast North Dakota to flow northeast to the north-oriented Red River and to eventually drain to Hudson Bay. The James River from figure 10 flows southeast and south into southern South Dakota, where it joins the southeast-oriented Missouri River and eventually drains to the Gulf of Mexico. The Sheyenne River-James River drainage divide is further illustrated and discussed in other essays (see essays under James River on sidebar category list), but briefly flood flow in what is today the Sheyenne River drainage basin was captured when south-oriented flood flow in the Red River valley was beheaded and reversed so as to flow north, while flood flow in what is today the James River drainage basin was not captured by that flood flow reversal event. The Sheyenne River capture event probably occurred before the Souris River capture event described in the figure 9 discussion. The present day Sheyenne River and James River valleys were probably deepened by flood waters moving through the Lincoln Valley breach prior to the climatic change that closed the breach and forced flood waters south along the Southwest Ice Sheet west margin.

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.