A geomorphic history based on topographic map evidence

The Missouri River-James River drainage divide area between Apple Creek and Beaver Creek is located in south central North Dakota, USA. The region is bounded on the west by the south-oriented Missouri River and on the east by the south-oriented James River. Apple Creek and Beaver Creek are Missouri River tributaries. Between the Missouri River and James River are the Missouri Coteau and east-facing Missouri Escarpment. The Missouri Escarpment is interpreted to be a remnant of the west wall of a large southeast and south-oriented ice-walled and bedrock-floored valley sliced by melt water floods into a thick North American ice sheet. The Missouri Coteau is interpreted to be debris deposited by the detached southwest margin of that thick ice sheet. Evidence within the drainage divide region suggests ice-marginal melt water floods carved ice-walled and bedrock-floored valleys across the ice sheet’s detached southwest margin to reach the lower elevation ice-walled and bedrock-floored valley in which the James River is now located.

• The purpose of this essay is to use topographic map interpretation methods to explore Missouri River-James River drainage divide area landform origins between Apple Creek and Beaver Creek, 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-James River drainage divide area landform evidence between Apple Creek and Beaver Creek 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 between Apple Creek and Beaver Creek location map

Figure 1: Missouri River-James River drainage divide area between Apple Creek and Beaver Creek 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-James River drainage divide area between Apple Creek and Beaver Creek location map. North Dakota is the state in the northern three-fourths of figure 1. South Dakota is located south of North Dakota. The Missouri River flows south-southeast from Lake Sakakawea in the figure 1 northwest corner past Bismarck and into South Dakota. Lake Sakakawea is a large reservoir flooding the Missouri River valley upstream from Garrison Dam. Lake Oahe is another large reservoir which floods the Missouri River valley in northern South Dakota and southern North Dakota. The dam responsible for Lake Oahe is located south of the figure 1 map area. The James River originates south of Harvey near the figure 1 north center edge and flows north, east, and southeast before turning to flow south to Jamestown, North Dakota. At Jamestown the James River turns to flow southeast to Oakes, North Dakota and then turns to flow south and south-southwest into South Dakota and to the figure 1 south edge. South of figure 1 the James River eventually joins the southeast oriented Missouri River in southeastern South Dakota. Apple Creek is the unlabeled southeast and southwest-oriented Missouri River tributary joining the Missouri River just south of Bismarck, North Dakota. Beaver Creek is a west-oriented Missouri River located south of Apple Creek and originates at Beaver Lake (southeast of Napoleon, North Dakota) and flows southwest and west to Linton before reaching the south-oriented Missouri River. The Missouri River-James River drainage divide area between Apple and Beaver Creeks as defined in this essay generally is located south of Interstate 94 (between Bismarck and Jamestown) and north of state highway 13 (Between Linton and La Moure). Integrated drainage patterns are found close to the Missouri River valley on the west and close to the James River valley in the east. Much of the region between these integrated patterns is the Missouri Coteau region, which does not have an integrated drainage pattern. The Missouri Coteau is generally thought to be a region of thick glacial moraines, probably deposited by a stagnant ice sheet remnant, which gradually melted. The Missouri Coteau area extends between the Missouri River valley and the James River from northwest North Dakota (actually east central Alberta) southward into South Dakota and is interpreted here to have been deposited by the detached southwest margin of a thick North American ice sheet. Long Lake is located in a large northeast-oriented valley, into which streams drain, but which does not normally have an outlet. The northeast-oriented valley is interpreted here to be evidence of a northeast-oriented ice-walled and bedrock-floored valley, which had been sliced across the detached ice sheet margin occupying the Missouri Coteau region. The eastern edge of the Missouri Coteau is the east-facing Missouri Escarpment, which is illustrated in figures 9 and 10 below.

Missouri River-James River drainage divide area between Apple Creek and Beaver Creek detailed location map

Figure 2 provides a slightly more detailed location map for the Missouri River-James River drainage divide area located between Apple Creek and Beaver Creek. Burleigh, Kidder, Stutsman, Emmons, Logan, McIntosh, La Moure, and Dickey are North Dakota counties. The west-to-east oriented North Dakota-South Dakota state line is located along the figure 2 south edge. The Missouri River flows south-southeast and south from the figure 2 northwest corner to the figure 2 south edge. The James River flows south in the figure 2 northeast quadrant to Jamestown and then flows southeast and south into La Moure County, where it turns to flow southeast to northern Dickey County and to the figure 2 east edge. Apple Creek is the southeast and southwest oriented Missouri River tributary in Burleigh County, which flows to the Missouri River just south of Bismarck. Beaver Creek flows southwest from Beaver Lake near Burnstad in Logan County to the Logan County southwest corner and then flows west across Emmons County to join the south-oriented Missouri River. The northeast-oriented Long Lake valley is located in the red shaded area marked as the Long Lake National Wildlife Refuge. West of the James River are a number of east and southeast oriented streams. These streams originate on the east facing Missouri Escarpment slope and eventually reach the south- and southeast oriented James River. Figures 9 and 10 below illustrate streams in the Minneapolis Flats area located south of Jamestown. The region with numerous small lakes located between the west-oriented Missouri River and the east oriented James River tributaries is the Missouri Coteau. Figure 8 below illustrates a typical Missouri Coteau region. As previously mentioned the east facing Missouri Escarpment is what remains of the west and southwest wall of an immense southeast and south-oriented ice-walled and bedrock-floored valley that was sliced into a thick ice sheet. That valley is here named the Midcontinent Trench and the immense southeast and south-oriented melt water river responsible for slicing the Midcontinent Trench into the ice sheet surface is here named the Midcontinent River. Headward erosion of the Midcontinent Trench valley detached the thick ice sheet’s southwest margin. That detached ice sheet southwest margin is here named the Southwest Ice Sheet. At the same time melt water floods moved along the ice sheet’s southwest margin, which was higher in elevation than the Midcontinent Trench floor, and at certain locations were able to carve east and northeast-oriented ice-walled and bedrock-floored valleys across the Southwest Ice Sheet ice barrier. Late during the thick ice sheet’s rapid melt down those east and northeast-oriented valleys across the Southwest Ice Sheet became blocked (perhaps by a rapid climate change which froze flood waters in the valleys and on the Midcontinent Trench floor and which also reinvigorated the detached Southwest Ice Sheet). Unable to flow in an east and northeast direction onto the Midcontinent Trench floor the ice-marginal floods were forced to move southeast and south along the Southwest Ice Sheet southwest margin, and by doing so they eroded the Missouri River valley.

Apple Creek-Long Lake Creek drainage divide area

Figure 3: Apple Creek-Long Lake Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the Apple Creek-Long Lake Creek drainage divide area east of Bismarck, North Dakota. The southeast oriented Missouri River is located in the figure 3 southwest corner. Apple Creek flows in a southwest direction to join the Missouri River in the figure 3 southwest corner. Long Lake Creek is located in the figure 3 east center area and flows in a southeast direction to the figure 3 east edge. East of figure 3 Long Lake Creek flows to Long Lake, which is located in what is normally an interior drainage basin. Note along the figure 3 north edge area southeast oriented tributaries to southwest-oriented Apple Creek. Also note the northwest-southeast oriented through valleys located southeast of Apple Creek, some of which link the southwest-oriented Apple Creek valley with the southeast oriented Long Lake Creek valley. These northwest-southeast-oriented through valleys provide evidence of a southeast-oriented anastomosing channel complex located in the figure 3 map area prior to headward erosion of the present day deep Missouri River valley. The deep Missouri River valley probably eroded along one of the channels in the anastomosing channel complex and the southwest-oriented Apple Creek valley probably eroded headward from that deep valley to capture southeast-oriented flood flow in channels adjacent to the newly eroded deep Missouri River valley. As the Missouri River eroded further to the northwest and north it beheaded flood flow routes leading to the newly eroded southwest-oriented Apple Creek valley (see Missouri River-Apple Creek drainage divide area essay found under ND Missouri River on sidebar category list). What was happening was prior to headward erosion of the Missouri River valley, ice-marginal melt water floods that had been flowing east and northeast across the detached Southwest Ice Sheet to the lower elevation southeast- and south-oriented Midcontinent Trench (on the thick ice sheet floor) for some reason were blocked and forced to flow along the Southwest Ice Sheet’s southwest margin. These southeast-oriented flood waters carved the anastomosing channels prior to headward erosion of the deep Missouri River valley, which captured the southeast-oriented flood water. Once headward erosion of the deep Missouri River valley had drained water from these final flood events, whatever ice remained melted slowly and no comparable immense flood events occurred (although there were probably many smaller sized flood events). The reason for this change was probably related to the opening up of north-oriented drainage routes across the rapidly melting thick ice sheet floor. These northern drainage routes had shorter distances to sea level and were able to capture the immense south-oriented melt water floods and divert the flood water from the Gulf of Mexico to Hudson Bay and the Arctic Ocean. These gigantic flood diversions probably caused a major climate change, which froze flood waters on the thick ice sheet floor and which blocked the east and northeast-oriented valleys through the detached Southwest Ice Sheet. In effect the climate change created a wet based thin ice sheet with remnants of the thick ice sheet embedded in it. Melting of the resulting thin ice sheet, while probably producing melt water floods, did not produce the immense melt water floods melting of thick ice sheet had produced.

Dutton Slough-Long Lake valley

Figure 4: Dutton Slough-Long Lake valley. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates the Dutton Slough-Long Lake valley southeast of the figure 3 map area and includes overlap areas with figure 3. Lake Oahe, which is a reservoir flooding the Missouri River valley, is located in the figure 4 southwest corner. The southeast-oriented Long Lake Creek seen in figure 3 flows from the figure 4 north center edge to the northwest oriented Long Lake bay located near Moffit, North Dakota. Note how Long Lake and Dutton Slough are located in a southwest-northeast oriented through valley. The southwest end of that through valley (southwest of Dutton Slough) is drained by northwest and southwest-oriented Badger Creek to the south-oriented Missouri River. Dutton Slough and drainage routes in the figure 4 southeast quadrant drain into Long Lake, which normally does not overflow. The west-oriented stream in the figure 4 southwest quadrant is also named Long Lake Creek and southeast of figure 4 is a northwest-oriented stream. The northeast-oriented Dutton Slough-Long Lake through valley provides evidence that at one time water flowed through it. Based on the topographic map evidence alone the direction of flow can probably be debated. One possibility being proposed here is the Long Lake valley (see figure 5 below) originated as a northeast-oriented ice-walled and bedrock-floored valley sliced across the detached Southwest Ice Sheet ice barrier. Southeast-oriented flood water moving along the Southwest Ice Sheet southwest margin flowed into the northeast-oriented valley (along routes such as the southeast-oriented Long Lake Creek route) and then turned to flow northeast across the Southwest Ice Sheet ice barrier to the lower elevation Midcontinent Trench. When northeast-oriented flood flow through that ice-walled and bedrock-floored became blocked, flood waters moved southeast along the Southwest Ice Sheet southwest margin (along routes such as the present day northwest-oriented Long Lake Creek valley southeast of figure 4). Headward erosion of the deep Missouri River valley then enabled the through valley (in which Dutton Slough is located) to erode headward to drain ponded flood water in the blocked Long Lake valley further to the northeast and also to capture the southeast-oriented flood water moving along the Southwest Ice Sheet southwest margin. Headward erosion of this southwest-oriented valley beheaded flood flow routes to the southeast. Flood waters on the northwest ends of those beheaded flood flow routes reversed flow direction to flow north and northwest and to erode the northwest-oriented Long Lake Creek valley and drainage basin (and other north and northwest Long Lake tributary valleys).

Long Lake valley

Figure 5: Long Lake valley. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the northeast-oriented Long Lake valley northeast of figure 4. Note how this is a significant northeast-oriented valley, now blocked to the northeast by glacial moraines. The interpretation provided here, as previously described, is this valley was eroded as the southwest end of a northeast-oriented ice-walled and bedrock-floored valley cutting across the detached Southwest Ice Sheet ice barrier. The valley was used by ice-marginal melt water floods moving to the lower elevation Midcontinent Trench floor located east and northeast of the Missouri Escarpment. The thick ice sheet involved was located in a deep “hole”, which had been developed by deep glacial erosion and by crustal warping caused by the thick ice sheet weight. The thick ice sheet is hypothesized here to have formed on a topographic surface at least as high as the highest Rocky Mountain erosion surfaces today. Being located in a deep “hole” meant the ice sheet floor elevation was considerably below the ice sheet rim elevation, although at one time the ice sheet probably stood considerably higher than the surrounding landscape (the present day Antarctic Ice Sheet would be a modern analog). When the thick ice sheet began to melt faster than new ice was being formed melt water floods poured off the ice sheet surface and moved along the ice sheet margin until they could flow south to the Gulf of Mexico. In time ice sheet melting progressed to the point where the ice sheet surface (at least along the southern margin) was lower in elevation than the ice sheet rim area. Melt water floods then moved onto and across the ice sheet surface in ice-walled and ice-floored valleys to southeast and south-oriented ice-walled and ice-floored valleys, such as southeast and south-oriented Midcontinent Trench valley, which later became a bedrock-floored valley. But, before the Midcontinent Trench became a bedrock-floored valley east and northeast-oriented melt water floods deeply eroded the ice sheet rim area, although floods were moving to what was always a lower elevation south-oriented valley located within the thick ice sheet itself. This northeast-oriented Long Lake valley was probably eroded during the final stages of this northeast-oriented melt water flood movement to the southeast and south-oriented Midcontinent Trench valley. Shortly after this valley eroded the immense south-oriented Midcontinent River was captured and diverted north. Diversion of the immense south-oriented melt water floods to Hudson Bay and the Arctic Ocean triggered a major Northern Hemisphere cooling event, which revitalized the Southwest Ice Sheet and which blocked the east and northeast-oriented valleys crossing the Southwest Ice Sheet ice barrier. The resulting thin ice sheet (with thick ice sheet remnants embedded in it) was responsible for glacial moraines now filling the Long Lake valley further to the northeast.

Horsehead Valley

Figure 6: Horsehead Valley. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates the Horsehead Valley located south of the figure 4 map area and there is a gap between figure 4 and figure 6. The flooded south-oriented Missouri River valley is located along the figure 6 west edge (north half). The west and southwest oriented stream in the figure 6 southeast corner area is Beaver Creek, which flows west to reach the south oriented Missouri River. The large northwest-southeast oriented Horsehead Valley in figure 6 links the south-oriented Missouri River valley (north of figure 6) with the Beaver Creek valley and continues southeast into South Dakota (see figure 1). The valley was eroded by southeast-oriented ice-marginal melt water floods moving along the Southwest Ice Sheet southwest margin prior to headward erosion of the deep south-oriented Missouri River valley. Southeast-oriented flood flow in the Horsehead Valley may have been moving to a northeast-oriented ice-walled and bedrock-floored valley across the Southwest Ice Sheet ice barrier located in northern South Dakota, or it could have been eroded as one of several anastomosing valleys at the time the deep Missouri River valley was being eroded north. In either case as the deep south-oriented Missouri River valley eroded north flood water probably became ponded in the Horsehead Valley and surrounding area and the Beaver Creek valley was able to erode west to drain the ponded flood water. Headward erosion of the deep south-oriented Missouri River valley beheaded the Horsehead Valley north of figure 6, causing a flow reversal on the Horsehead Valley northwest end (creating the present day northwest-oriented drainage system there which flows to the south-oriented Missouri River as a barbed tributary). Note the presence of several short northwest-oriented Missouri River tributaries located in the figure 6 northwest quadrant. Those tributaries provide evidence the south-oriented Missouri River valley eroded headward across multiple southeast-oriented flood flow routes. Flood waters on the northwest ends of those flood flow routes reversed flow direction to erode the short northwest-oriented tributary valleys. The southwest and south-oriented Beaver Creek tributary located in the figure 6 east half is Sand Creek. The Sand Creek valley was probably eroded headward to capture southeast-oriented ice-marginal melt water flood flow and probably was initiated when the deep Horeshead Valley was being eroded.

Beaver Creek headwaters at Beaver Lake

Figure 7: Beaver Creek headwaters at Beaver Lake. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Beaver Creek headwaters at Beaver Lake and southeast of Napoleon, North Dakota. Figure 7 is located east of figure 6 and there is a gap between figure 6 and figure 7. Beaver Creek originates at Beaver Lake in the figure 7 southeast quadrant and flows west and southwest to the figure 7 southwest corner area. Figure 7 illustrates the eastern edge of the area eroded by ice marginal south and southeast-oriented melt water floods along the Southwest Ice Sheet southwest margin and the western edge of the area occupied by the Southwest Ice Sheet at the time the deep south oriented Missouri River valley was eroded headward into North Dakota. Note the large number of small lakes along the figure 7 east edge area. Those small lakes provide evidence of glacial moraine materials not present further to east in the figure 7 map area. Areas in the eastern two-thirds of figure 7, while probably containing significant ice and flood deposited debris, appear to be water-eroded landscapes. Flood waters were probably moving south along the Southwest Ice Sheet southwest and west margin and the Beaver Creek valley eroded headward from the newly eroded Missouri River valley to capture the south oriented flood flow. The south and southwest-oriented valley located just west of Napoleon drains to Beaver Creek southwest of figure 7 and probably eroded headward to capture flood flow. The northwest-oriented valley extending from Peters (in the figure 7 center) to Napoleon is probably located on what was a southeast-oriented flood flow channel alignment. Headward erosion of the south and southwest-oriented valley just west of Napoleon probably beheaded that southeast-oriented flood flow channel. Flood waters on the northwest end of the beheaded flood flow channel reversed flow direction to erode the northwest-oriented valley. Probably at that time yet to be beheaded southeast-oriented flood waters were still flowing further to the east (perhaps into the Beaver Lake area) and reversed flow in the Peters-Napoleon valley captured that yet to be beheaded flood flow. That capture of yet to be beheaded flood flow provided the volumes of water required to erode the northwest-oriented valley. Lakes in the eastern third of figure 7 probably represent locations where final ice sheet remnants, buried in debris the ice sheet had transported, gradually melted and left depressions now partially filled with water.

Missouri Coteau region near Medina, North Dakota

Figure 8: Missouri Coteau region near Medina, North Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates the Missouri Coteau region north and east of the figure 7 map area and there is a gap between the figure 7 map area and the figure 8 map area. The figure 8 landscape is typical of Missouri Coteau landscapes between the Missouri Escarpment and Missouri River valley in North and South Dakota and also found southwest of the Missouri Escarpment extension in Saskatchewan and east central Alberta. The region contains small hills and numerous water-filled depressions suggesting this was an area where a decaying ice sheet (containing significant debris) gradually melted. The hypothesis presented here is the Missouri Coteau represents debris deposited by the detached margin of a thick North American ice sheet, which had been located in a deep “hole.” The ice sheet at one time had probably been several kilometers thick. Whether it was ever that thick in the figure 8 map area can probably be debated, but as previously described the hypothesis presented here is the ice sheet originally was formed on topographic surface now preserved (if it is preserved at all) by the highest level Rocky Mountain erosion surfaces. If so, the elevation of this ice floor region in North Dakota is significantly below the elevation of the surface on which the ice sheet was formed. A combination of deep glacial erosion and crustal warping caused by the ice sheet weight probably created the deep “hole” in which the thick ice sheet was located. Deep glacial erosion probably resulted in considerable debris being contained within the thick ice sheet ice mass (especially in the lower parts of the thick ice sheet). As the ice sheet melted this debris accumulated on the ice sheet surface. Melt water rivers flowing on the ice sheet surface probably removed significant amounts of this debris (especially along the major supra glacial melt water river routes such as the Midcontinent Trench area). However, debris would not have removed from ice sheet surface areas between the immense south-oriented melt water rivers and would simply have accumulated while ice underneath gradually melted. The detached Southwest Ice Sheet represented a thick ice sheet area which was not significantly affected (at least late during the ice sheet melt down) by the immense south-oriented supra glacial melt water rivers. For that reason debris accumulated on the ice sheet surface as ice underneath melted and the Missouri Coteau today represents where that debris ended up.

Missouri Coteau, Missouri Escarpment and James River valley near Jamestown

Figure 9: Missouri Coteau, Missouri Escarpment and James River valley near Jamestown. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Missouri Coteau, Missouri Escarpment, and James River valley area west of Jamestown. Figure 9 is located east of figure 8 and there is a gap between figure 8 and figure 9. Jamestown, North Dakota is the city located in the figure 9 northeast corner. The James River is the southeast oriented river flowing through Jamestown. Note how west of Eldridge (in the figure 9 north center edge area) there is  gradual rise to Windsor in the figure 9 northwest corner (Windsor is approximately 125 meters higher than the James River valley floor at Jamestown and the James River valley is about 25 meters deep at Jamestown). The rise between Eldridge and Windsor is the Missouri Escarpment and is somewhat less obvious in figure 9 than in some areas further north or south. The Missouri Escarpment is a significant landscape feature which can be traced north and northwest from the figure 9 map area across North Dakota and Saskatchewan into east central Alberta. The Missouri Escarpment can also be traced southward into southern South Dakota. Throughout that entire length the Missouri Coteau (or Missouri Coteau type landscape) can be found at the Missouri Escarpment crest. Windsor is located on the Missouri Coteau eastern edge. At the Missouri Escarpment base are lowlands, which while showing evidence of having been glaciated, do not show evidence of having the thick deposits of glacial debris found in the Missouri Coteau type areas immediately to the west and southwest of the Missouri Escarpment. The Missouri Escarpment slope likewise does not usually show evidence of having the thick glacial debris deposits found in the Missouri Coteau type areas immediately to west and southwest. The Missouri Escarpment is interpreted here to be what remains of the western and southwest wall of the immense southeast and south-oriented ice-walled and bedrock-floored Midcontinent Trench which was sliced by an immense southeast and south-oriented melt water river into the rapidly melting North American thick ice sheet surface. The Midcontinent Trench floor may have been subsequently covered with a wet based thin ice sheet late during the thick ice sheet melt down history. At that time the immense south-oriented floods were captured and diverted north, causing a major climate change. The climate change froze melt water floods on the ice sheet floor, creating a thin ice sheet with thick ice sheet remnants embedded within it. Melting of the thin ice sheet did not significant alter drainage routes, which had been developed previously by immense melt water floods during the thick ice sheet rapid melt down.

Missouri Coteau, Missouri Escarpment and James River valley near Minneapolis Flats

Figure 10: Missouri Coteau, Missouri Escarpment and James River valley near Minneapolis Flats. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 illustrates the Missouri Coteau, Missouri Escarpment, and James River valley in the Minneapolis Flats area south and east of the figure 9 map area. The southeast oriented James River valley is located in the figure 10 northeast corner. The eastern edge of the Missouri Coteau is located along the figure 10 west edge. East of the Missouri Coteau is the east facing Missouri Escarpment slope. Note how east oriented drainage routes are present on the Missouri Escarpment slope, while rarely extending headward into the Missouri Coteau region. The east oriented valleys on the Missouri Escarpment slope were probably eroded by melt water from slowly melting Southwest Ice Sheet remnants, which survived the rapid thick ice sheet melt down.  The Minneapolis Flats area in the figure 10 north center area is a south-southeast oriented valley located at the Missouri Escarpment base and was probably eroded late during the Midcontinent Trench history by final south-southeast oriented melt water floods. The James River valley and present day tributary valleys were also probably eroded on the Midcontinent Trench floor by the final south-oriented Midcontinent River flood flow event. South-oriented flood waters in this section of the Midcontinent Trench were captured and diverted north the reversal of flood flow in the Red River valley that captured the Sheyenne River (see James River-Sheyenne River and James River-Wild Rice River drainage divide area essays found under James River on sidebar category list). Headward erosion of the deep Sheyenne River valley following that capture beheaded most southeast and south-oriented Midcontinent River flood flow routes to this figure 10 map area (see Sheyenne River-James River drainage divide area essay). At about the same time as headward erosion of the deep Sheyenne River valley was beheading flood flow routes to the James River valley the Midcontinent River was captured in north central North Dakota (see Souris River loop in Missouri River-Souris River drainage divide area essay found under ND Missouri River on sidebar category list). Evidence for additional Midcontinent River captures and diversions to the north can be found in Saskatchewan and possibly even in Alberta. Ice-marginal flood waters moving through east and northeast oriented valleys cut across the Southwest Ice Sheet ice barrier still reached the Midcontinent Trench floor, until those flood flow routes became blocked.

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.