A geomorphic history based on topographic map evidence

This essay provides an overview more detailed essays using topographic map evidence to interpret  Big Sioux River drainage basin landform origins. The detailed essays can be found under Big Sioux River on this website’s sidebar category list. All interpretations in this overview essay and in the more detailed essays are based entirely on topographic map evidence. The Big Sioux River flows in a south direction in eastern South Dakota from north of Watertown to Brookings and then to Sioux Falls before joining the Missouri River near Sioux City, Iowa. The Big Sioux River course is located on the Prairie Coteau upland, which is an escarpment bounded upland located between the south-oriented James River lowland to the west and the southeast-oriented Minnesota River lowland to the northeast. Away from the Big Sioux River valley the Prairie Coteau upland surface appears to be covered by glacially deposited sediments. The Prairie Coteau upland surface is bounded on the west by a 200-meter high west-facing Prairie Coteau Escarpment and on the northeast by a 200-meter high northeast-facing Prairie Coteau Escarpment. The escarpments and the James River lowland and Minnesota River lowlands are interpreted to have formed when huge ice-walled and bedrock-floored canyons were sliced into the surface of a rapidly melting thick North American ice sheet. The Big Sioux River valley was the location of a smaller and shallower ice-walled and bedrock-floored canyon, which was sliced into the detached ice sheet remnant located between the much deeper and larger southeast-oriented Minnesota River lowland and south-oriented James River lowland ice-walled and bedrock-floored canyons. Supra-glacial melt water flood flow to the smaller Big Sioux River ice-walled canyon was beheaded when the deep James River and Minnesota River ice-walled canyons intersected in what is now southeast North Dakota. For this reason the floor of the Big Sioux River ice-walled canyon was not eroded as deep as the floors of the adjacent James River and Minnesota River ice-walled canyons and is today located on the Prairie Coteau upland surface. Topographic map evidence suggests the detached Prairie Coteau ice sheet remnant, with the Big Sioux River ice-walled and bedrock-floored canyon carved into it, slowly melted with the ice sheet depositing whatever debris it contained on the what is now the Prairie Coteau upland surface.

Figure 1: South Dakota Big Sioux River drainage basin (select and click on map to enlarge). The Big Sioux River flows in a south direction in eastern South Dakota through Watertown, Brookings, and Sioux Falls and joins the Missouri River near Sioux City, Iowa. National Geographic Society map digitally presented using National Geographic Society TOPO software.

Figure 1 provides a regional map showing drainage routes in eastern South Dakota and the adjacent states of Minnesota, North Dakota, Iowa, and Nebraska. The Big Sioux River originates in northeast South Dakota, north of Watertown, and flows in a south direction to Brookings and Sioux Falls, South Dakota before joining the southeast oriented Missouri River near Sioux City, Iowa. West of the Big Sioux River and east of the south and southeast oriented Missouri River is the south-oriented James River, which joins the Missouri River near Yankton, South Dakota. East of the Big Sioux River headwaters is the southeast oriented Minnesota River, which near Mankato, Minnesota turns to flow in a northeast direction to join the southeast- and south-oriented Mississippi River near St. Paul, Minnesota. Further south the southeast-oriented Des Moines River drainage basin is located east of the Big Sioux River drainage basin. The Des Moines River joins the south-oriented Mississippi River south of the figure 1 southeast corner. North of the Big Sioux River headwaters are headwaters of Red River tributaries, with the Red River being the north-oriented river flowing through Fargo, North Dakota (near figure 1 north center edge). Red River water eventually reaches Hudson Bay, which means the Red River-Big Sioux River drainage divide is also the north-south continental divide.

• Detailed essays describing all drainage divides surrounding the present day Big Sioux River drainage basin and describing all South Dakota and North Dakota Missouri River drainage basin drainage divides have been written. Evidence presented in these detailed essays demonstrates the Big Sioux River valley and tributary valleys eroded headward as ice-walled and bedrock-floored valleys carved into a decaying ice sheet remnant. The larger ice sheet had been a thick North American ice sheet comparable in size if not larger than the present day Antarctic Ice Sheet. The ice sheet had been located in a deep “hole” created by deep glacial erosion of regions under the ice sheet and by crustal warping caused by ice sheet’s tremendous weight. Probably when fully developed the ice sheet had stood two or more kilometers above the surrounding non glaciated surface and had “roots” extending one or more kilometers below the surrounding non glaciated surface. The pre-glacial surface both under the ice sheet and adjacent to the ice sheet (and probably throughout much of the North American continent) has been destroyed by deep glacial erosion and/or by deep melt water erosion as melt water floods flowed from the rapidly melting ice sheet. Big Sioux River drainage basin history, which can be determined from topographic map evidence, began late during this gigantic ice sheet’s melt down history, when melting had already lowered the ice sheet surface to the point that only ice sheet “roots’ were left in the region now occupied by South Dakota and the adjacent states. At that time large supra-glacial melt water rivers were flowing on the decaying ice sheet’s surface and were carving deep ice-walled and ice-floored canyons (later bedrock-floored canyons) into the ice sheet’s surface. One of those supra-glacial melt water rivers probably flowed in a south direction along the alignment of the present day Big Sioux River.

• East of the south oriented supra-glacial river flowing on the Big Sioux River alignment was a southeast oriented supra glacial melt water river flowing on what is today the southeast oriented Minnesota River alignment. South-oriented supra-glacial melt water floods to the developing Big Sioux River ice-walled canyon were captured by headward erosion of that much deeper and larger southeast oriented Minnesota River ice-walled canyon which then carved a giant south and southeast oriented canyon into the decaying ice sheet’s surface. The south oriented north end of that giant ice-walled canyon, which had been the Big Sioux River ice-walled canyon headwaters area before being captured, was located on the alignment of the present day north-oriented Red River valley. At the same time as the deep south and southeast oriented Minnesota River ice-walled and bedrock-floored canyon was being carved headward into the decaying ice sheet surface an equally large southeast and south oriented ice-walled and bedrock-floored canyon was being carved west of the Big Sioux River ice-walled canyon along the present day James River alignment. The southeast and south oriented James River ice-walled and bedrock-floored canyon intersected with the south- and southeast-oriented Minnesota River ice-walled and bedrock-floored canyon in southeast North Dakota. The intersection of these two immense ice-walled and bedrock-floored canyons north of the beheaded Big Sioux River ice-walled canyon (which at that time was probably bedrock-floored in the south) completely detached the decaying ice sheet remnant into which the Big Sioux River ice-walled canyon was being carved.

Figure 2: Regional map illustrating drainage routes in northeast South Dakota, a strip of southeast North Dakota, and an area in western Minnesota. The Big Sioux River is the unlabeled stream flowing through Watertown, South Dakota (near south center edge). National Geographic Society map digitally presented using National Geographic Society TOPO software.

Figure 2 provides a somewhat more detailed regional map of northeast South Dakota drainage routes with drainage routes in adjacent western Minnesota and southeast North Dakota also shown. The Big Sioux River is the unlabeled stream flowing through Watertown, South Dakota (located near the figure 2 south center edge). The south-oriented James River is located near the figure 2 west edge. The southeast-oriented Minnesota River flows from the Claire City, South Dakota area (in South Dakota northeast corner) to Big Stone Lake and then to the figure 2 southeast corner. The Bois de Sioux River flows in a north direction from Lake Traverse to the figure 2 north edge and is a north-oriented Red River tributary. The north-south continental divide is located near Browns Valley, Minnesota between Lake Traverse and Big Stone Lake, with Browns Valley being a deep north-south through valley crossing the present day north-south continental divide. In the North Dakota southeast corner the unlabeled east and northeast oriented meandering stream is the Wild Rice River, which has headwaters in northeast South Dakota (although not shown on the figure 2 map). The Wild Rice River is a Red River tributary and the James River-Wild Rice River, Wild Rice River-Minnesota River, and the Wild Rice River-Big Sioux River drainage divides are all segments of the north-south continental divide.

• Topography is not shown on the figure 2 map, however the more detailed Big Sioux drainage basin landform origins essays provide approximately 100 topographic maps of Big Sioux River drainage basin areas. The topographic maps provide evidence the Big Sioux River headwaters originate on an upland surface  200 meters higher than floors of lowlands on either side. The upland surface is covered by what appear on topographic maps to be glacially deposited debris and is known as the Prairie Coteau. Figure 3 below provides a topographic map of the north end of that Prairie Coteau upland surface to illustrate how the Prairie Coteau upland narrows to the north and then ends. The Prairie Coteau upland surface is bounded to the northeast by the northeast-facing Prairie Coteau Escarpment and to the northwest and west by the northwest and west-facing Prairie Coteau Escarpment. The northeast-facing Prairie Coteau Escarpment is what remains of the Minnesota River ice-walled and bedrock-floored canyon’s southwest wall. The west-facing Prairie Coteau Escarpment is what remains of the James River ice-walled and bedrock-floored canyon’s east wall (the east-facing Missouri Escarpment to the west is what remains of the ice-walled and bedrock-floored canyon’s west wall). Today the Big Sioux River and its tributaries drain much of the Prairie Coteau upland surface, which is located between the two escarpments, although some Prairie Coteau upland surface areas are not drained by surface streams and other areas are drained to adjacent drainage basins. This Prairie Coteau upland surface includes regions covered by thick glacial sediments, suggesting the detached ice sheet remnant melted and deposited whatever debris it contained. The Big Sioux River valley system was probably eroded headward into the rapidly melting ice sheet margin as a much smaller and shallower ice-walled and bedrock-floored valley (than the larger and adjacent Minnesota River lowland and James River lowland valleys).

Figure 3: North end of Prairie Coteau upland surface. Further south the Prairie Coteau upland surface is drained by the south-oriented Big Sioux River. West-facing escarpment drains to Wild Rice River, which drains eventually to Hudson Bay. Further south the west-facing escarpment drains to the south-oriented James River. Northeast-facing escarpment drains to southeast-oriented Minnesota River. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 3 uses reduced size topographic maps to illustrate the Prairie Coteau upland surface north end. The Prairie Coteau upland surface is approximately 200 meters higher than the lowlands on all sides. The upland surface landscape suggests it is covered by thick glacial deposits and in much of the upland surface region there is no evidence of surface drainage routes. Evidence for thick glacial deposits is not present on the adjacent escarpment slopes or on the floors of the adjacent lowlands. This figure 3 region is north of the Big Sioux River headwaters region, although the Big Sioux River originates in an upland surface region similar to the upland surface seen in figure 3 and eventually reaches the Missouri River, which flows to the Mississippi River. Streams flowing down the northeast-facing escarpment slope are headwaters of Minnesota River tributaries with water flowing eventually to the Mississippi River and then to the Gulf of Mexico. Most streams flowing down most of the figure 3 west-facing escarpment slope are Wild Rice River headwaters, with the Wild Rice River eventually flowing to the north-oriented Red River and the water eventually reaching Hudson Bay. Streams flowing down the west-facing escarpment slope in the figure 3 southwest corner, however are headwaters of James River tributaries, with the James River flowing to the Missouri River. In other words the north-south continental divide crosses the present day west-facing Prairie Coteau Escarpment slope in a west to east direction and then continues in a north direction to the Prairie Coteau north end. Any explanation of northeast South Dakota drainage history must explain the origin of this north-south continental divide.

• Detailed essays found under Big Sioux River and James River on the sidebar category list illustrate and discuss topographic map evidence suggesting the Prairie Coteau upland surface is where a detached thick ice sheet remnant slowly melted. The ice sheet remnant was detached when the south and southeast-oriented Minnesota River ice-walled and bedrock-floored canyon intersected with the south-oriented James River ice-walled and bedrock-floored canyon just north of the figure 3 map area. The Prairie Coteau ice sheet remnant was located south of the southeast-oriented Minnesota River ice-walled and bedrock-floored canyon and west of the south-oriented James River ice-walled and bedrock-floored canyon. The northeast-facing escarpment seen in figure 3 is what remains of the southeast-oriented Minnesota River ice-walled and bedrock-floored canyon’s southwest wall. The west-facing escarpment in figure 3 is what remains of the giant south-oriented James River ice-walled and bedrock-floored canyon’s east wall. Intersection of these two giant ice-walled and bedrock-floored canyons just north of the figure 3 map area beheaded all ice sheet surface drainage routes to the south-oriented ice-walled canyon being carved into the detached Prairie Coteau ice sheet remnant. Without any melt water drainage from the decaying ice sheet further to the north the south-oriented Big Sioux River ice-walled canyon was not able to erode a bedrock-floored valley as deep as the adjacent Minnesota River and James River ice-walled and bedrock-floored canyon floors. The detached Prairie Coteau ice sheet remnant then melted as an independent ice sheet mass, with much of the melt water flowing south along the Big Sioux River valley route. Much of the debris contained in the Prairie Coteau ice sheet remnant (which was considerable because the ice sheet remnant was probably a remnant of the thick ice sheet “roots”) simply settled out and today covers the Prairie Coteau upland surface.

Figure 4: Regional map illustrating drainage routes in southeast South Dakota, southwest Minnesota, northwest Iowa, and northeast Nebraska. Big Sioux River flows from Watertown, South Dakota (near north center edge) to Brookings and Sioux Falls before joining Missouri River near Sioux City, Iowa. National Geographic Society map digitally presented using National Geographic Society TOPO software.

Figure 4 provides a regional map illustrating drainage routes in southeast South Dakota and adjacent states. The Big Sioux River flows from Watertown, South Dakota (near figure 4 north center edge) to Brookings and Sioux City, South Dakota before joining the southeast oriented Missouri River near Sioux City, Iowa (near south edge). The southeast oriented Missouri River flows from the figure 4 west center edge area to the South Dakota-Nebraska state line and then forms the state boundary until it reaches Sioux City, Iowa. Between the Missouri River and the Big Sioux River is the south-oriented James River, which flows through Huron and Mitchell before joining the Missouri River near Yankton, South Dakota. Also between the Missouri River and the James River is the east-facing Missouri Escarpment and west of the Escarpment crest is the Missouri Coteau upland surface. The Missouri Escarpment and Missouri Coteau could be considered a mirror image of the west-facing Prairie Coteau Escarpment and Prairie Coteau upland surface located east of the west-facing Prairie Coteau Escarpment crest. The east-facing Missouri Escarpment and west-facing Prairie Coteau Escarpment are each escarpments in the 200-meter high range. The Missouri Coteau and the Prairie Coteau upland surfaces are each covered by what appear on topographic maps to be thick glacially deposited debris, while the broad James River lowland located between the two escarpments has a very different appearance. The Missouri Escarpment is what remains of the gigantic south-oriented James River ice-walled and bedrock-floored canyon’s west wall while the west-facing Prairie Coteau Escarpment is what remains of the east wall. The southeast and south oriented James River ice-walled and bedrock-floored canyon in addition to detaching the Prairie Coteau ice sheet remnant also detached the decaying ice sheet’s southwest margin, which was located between the present day Missouri River valley and the Missouri Escarpment crest. The detached ice sheet margin also melted independently and deposited whatever debris it contained, although it was deeply eroded by southeast-oriented ice-marginal floods, some of which breached the detached ice sheet margin ice barrier and flowed to deeper James River ice-walled and bedrock-floored canyon floor.

• Also in figure 4 the southeast oriented Minnesota River can be seen in the northeast corner. To the south in the Minnesota southwest corner are headwaters of the southeast oriented Des Moines River. The Des Moines River headwaters are located along the crest of the northeast-facing Prairie Coteau Escarpment while the Minnesota River flows on the floor of the broad lowland located at the Escarpment base. The Des Moines River flows in a southeast direction across Iowa to join the south-oriented Mississippi River while the Minnesota River after flowing in a southeast direction turns to flow in a northeast direction to join the southeast and south oriented Mississippi River. South and east of the Minnesota River elbow of capture are headwaters of southeast-oriented Mississippi River tributaries and through valleys linking the southeast-oriented Minnesota River valley segment with those southeast-oriented Mississippi River tributary valleys. This evidence suggests the large melt water river flowing on the floor of large southeast-oriented Minnesota River ice-walled and bedrock-floored canyon originally flowed directly to the Mississippi River and then was captured by headward erosion of a deeper northeast-oriented ice-walled and bedrock-floored canyon into the decaying ice sheet surface. While outside the Missouri River drainage basin, this observation further supports interpretations of evidence presented in the Big Sioux River drainage basin landform origins detailed essays. The detailed essays illustrate through valleys linking Big Sioux River headwaters and tributary valleys with Des Moines River headwaters and tributary valleys and also with Minnesota River tributary valleys. The through valleys provide evidence of melt water flood flow routes developed as the Big Sioux River ice-walled canyon eroded headward into the decaying ice sheet and then as the deeper southeast-oriented Minnesota River ice-walled and bedrock-floored canyon detached the Prairie Coteau ice sheet remnant and beheaded melt water flood flow routes to what was then the actively developing Big Sioux River ice-walled canyon system.

Introduction to Missouri River drainage basin research project essay series

• This Big Sioux River drainage basin landform origins overview essay and its related detailed essays is one of a series of overview essays and related detailed essays in the Missouri River drainage basin landform origins research project. The research project goal is to use topographic map evidence to describe the evolution of drainage divides separating each significant present day Missouri River tributary valley and also to describe the evolution of drainage divides separating the present day Missouri River drainage basin from adjacent drainage basins. Each overview essay and its related detailed essays pertains to a specific Missouri River tributary, tributary to a present day Missouri River tributary, or a present day Missouri River valley segment. Each detailed essay illustrates and discusses detailed topographic map evidence describing the evolution of a secondary drainage divide separating specified Missouri River tributary valleys.

• The Missouri River drainage basin research project introduces a new regional geomorphology paradigm. An essay titled “About the ‘thick ice sheet that melted fast’ geomorphology paradigm” provides a brief introduction to the new paradigm and how the new paradigm emerged. Detailed evidence illustrated and discussed in the Missouri River drainage basin research project builds a strong case for (1) deep glacial erosion of the North American continent by a thick North American ice sheet that created and occupied a deep “hole”, (2) rapid melting of that thick North American ice sheet, (3) immense floods of south-oriented melt water, (4) headward erosion of deep east, northeast and north-oriented valley systems to capture the south-oriented melt water floods and to divert the melt water further and further northeast into space the ice sheet had once occupied, (5) deep flood water erosion of the North American continent surface, and (6) crustal warping that resulted in uplift of mountain ranges as flood waters were deeply eroding what are now high mountain regions. This interpretation is fundamentally different from most previous interpretations. The Big Sioux River drainage basin landform origins evidence in this overview essay and its related detailed essays is presented for review and discussion by qualified research geomorphologists and geologists.

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.