A geomorphic history based on topographic map evidence

The Bighorn River-Tullock Creek drainage divide area is located in Montana, USA. Although detailed topographic maps of the Bighorn River-Tullock Creek drainage divide area have been available for more than fifty years detailed map evidence has not previously been used to interpret the region’s geomorphic history. The interpretation provided here is based entirely on topographic map evidence. The Bighorn River-Tullock Creek drainage divide area is interpreted to have been eroded during immense southeast-oriented flood events, the first of which flowed on a topographic surface at least as high as the highest points in the present-day drainage divide area. Flood erosion across the drainage divide ended when headward erosion of the deep Bighorn River valley captured all southeast-oriented flood flow.

Preface:

The following interpretation of detailed topographic map evidence is provided as evidence in the Missouri River drainage basin landform origins research project, which is compiling similar evidence for all major drainage divides contained within the Missouri River drainage basin and for all major drainage divides with and within certain adjacent drainage basins. The research project is interpreting evidence in the context of a previously unexplored geomorphology paradigm, which is briefly described in the introduction below. Project essays are listed on the sidebar category list under their appropriate Missouri River tributary drainage basin, Missouri River segment drainage basin (by state), and/or state in which the Missouri River drainage basin is located.

Introduction:

• The purpose of this essay is to use topographic map interpretation methods to explore Montana Bighorn River-Tullock Creek drainage divide area landform origins. 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 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 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 similar essays is a thick North American ice sheet, comparable in thickness to the present day Antarctic ice sheet, occupied approximately the North American region usually recognized to have been glaciated and through its weight and erosive actions created a “deep” North American “hole”, 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 Bighorn River-Tullock Creek drainage divide area landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Bighorn River-Tullock Creek drainage divide area location map

Figure 1: Bighorn River-Tullock Creek 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 Bighorn River-Tullock Creek drainage divide area location map and illustrates a region in Montana. The state of Wyoming is located south of Montana. The Yellowstone River flows from Billings in a northeast direction to Fallon, located near the figure 1 northeast corner. The Bighorn River originates in Wyoming south of the figure 1 map area and enters the figure 1 map area at Greybull, Wyoming. After flowing northwest to the Montana state line the Bighorn River turns to flow northeast through the Bighorn Canyon National Recreation Area and then north-northeast to join the northeast-oriented Yellowstone River at Bighorn, Montana. The north-northwest and northwest oriented Little Bighorn River is the major Montana Bighorn River tributary and the Little Bighorn River joins the Bighorn River at Hardin, Montana. Tullock Creek originates in the Rosebud Mountains area southwest of Busby and flows north-northwest to join the Yellowstone River at Bighorn (at almost the same location as the location where the Bighorn River joins the Yellowstone River). Figure 1 illustrates a number of southeast and northwest-oriented Yellowstone River tributaries. The southeast and northwest-orientation of tributary valleys is evidence the northeast-oriented Yellowstone River valley eroded southwest across multiple southeast-oriented flood flow routes, such as might be found in a large-scale flood-formed anastomosing channel complex. Northwest-oriented tributary valleys were eroded by reversed flood flow on northwest ends of beheaded flood flow channels. Because channels were anastomosing (meaning they were interconnected) reversed flood flow on beheaded flood flow channels often captured yet to be beheaded southeast-oriented flood flow from flood flow channels further southwest. Such captures of yet to be beheaded flood flow helped erode significant northwest-oriented tributary valleys. Based on the northwest-southeast orientation of Yellowstone River tributary streams, landform evidence illustrated in this essay is interpreted in the context of an immense southeast-oriented flood flowing across the figure 1 map area and which was systematically captured and diverted further and further northeast by headward erosion of deep valleys eroded into a topographic surface at least as high as the figure 1 region highest elevations today. In the figure 1 map region headward erosion of the north-northwest oriented Tullock Creek valley first captured the southeast-oriented flood flow and diverted the flood waters to the northeast-oriented Yellowstone River valley and then headward erosion of the north-northeast oriented Bighorn River valley captured southeast-oriented flood flow routes moving water to the newly eroded Tullock Creek valley. Detailed maps below provide evidence supporting this interpretation. The Big Dry Creek-Yellowstone River drainage divide area essay and the Musselshell River-Yellowstone River drainage divide area essay both describe regions north of the Bighorn River-Tullock Creek drainage divide area discussed here and can be found under Yellowstone River on the sidebar category list. The Tullock Creek-Sarpy Creek drainage divide area and the Sarpy Creek-Rosebud Creek drainage divide area essay describe regions located east of the Bighorn River-Tullock Creek drainage divide area discussed here and can be found under Yellowstone River on the sidebar category list.

Bighorn River-Tullock Creek drainage divide area detailed location map

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

Figure 2 illustrates a somewhat more detailed map of the Bighorn River-Tullock Creek drainage divide area discussed here. Yellowstone, Treasure, Big Horn and Rosebud Counties are located in Montana. The Bighorn River-Tullock Creek drainage divide area discussed here is located in Treasure and Big Horn Counties and is south of the Yellowstone River. Tullock Creek originates southwest of Busby and flows northwest and north-northwest to the Yellowstone River at Bighorn (which is also where the north-northeast oriented Bighorn River joins the Yellowstone River). The north-northeast oriented Bighorn River flows from the figure 2 south edge through the Crow Indian Reservation to Hardin and then to join the Yellowstone River at Bighorn. The Little Bighorn River flows north-northwest and northwest from the figure 2 south edge to join the Bighorn River near Hardin. Figure 2 shows southeast and northwest-oriented Bighorn River tributaries, especially north of the Crow Indian Reservation. This southeast and northwest drainage alignment is evidence the north-northeast oriented Bighorn River valley eroded southwest to capture southeast-oriented flood flow. The southeast-oriented tributary valleys were eroded by southeast-oriented flood flow moving into the newly eroded Bighorn River valley and the northwest-oriented tributary valleys were eroded by reversals of flood flow on the northwest ends of beheaded southeast-oriented flood flow routes. Figure 2 also shows northwest-oriented Tullock Creek headwaters and tributaries, which were also eroded by reversals of flood flow on the northwest ends of beheaded southeast-oriented flood flow routes. Northwest-oriented Tullock Creek headwaters valleys were also eroded by reversals of flood flow on the northwest ends of beheaded southeast-oriented flood flow routes The Tullock Creek valley and the Bighorn River probably were eroding headward at about the same time, with Tullock Creek valley headward erosion slightly in advance of Bighorn River valley headward erosion because the Bighorn River valley eroded south to capture flood waters that were moving to the newly eroded Tullock Creek valley. Because flood waters move in and erode anastomosing (or interconnected) channels reversed flood flow on a beheaded flood flow route could capture flood flow from yet to be beheaded flood flow routes. Such captures of yet to be beheaded flood flow could enable the reversed flood flow routes to erode much deeper and larger northwest-oriented valleys than might otherwise be possible. Often evidence for such flow reversals and captures can be found on detailed topographic maps. Detailed maps below start with the Bighorn River-Tullock Creek drainage divide area immediately south of Bighorn, Montana and then progress south along the Bighorn River-Tullock Creek drainage divide and conclude by looking at the Little Bighorn River-Tullock Creek drainage divide area east of the Custer Battlefield National Monument.

North end of the Bighorn River-Tullock Creek drainage divide area

Figure 3: North end of the Bighorn River-Tullock Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the north end of the Bighorn River-Tullock Creek drainage divide area. The Yellowstone River flows northeast from the figure 3 west center edge to the figure 3 north edge near Bighorn. The Bighorn River flows north-northeast from the figure 3 south center edge to join the Yellowstone River near Bighorn. Tullock Creek flows northwest from the figure 3 southeast corner to join the Yellowstone River, also near Bighorn. Note southeast-oriented Yellowstone River tributaries in the figure 3 northwest corner and southeast-oriented Bighorn River tributaries from the west. Also note northwest-oriented Bighorn River tributaries from the east and northwest-oriented tributaries (including Tullock Creek) from the south. The southeast and northwest orientation of the Yellowstone River and Bighorn River tributaries is evidence the deep Yellowstone River valley and the deep Bighorn River valley eroded headward across southeast-oriented flood flow routes. The northwest-oriented tributary valleys were eroded by reversals of flood flow on the northwest ends of beheaded southeast-oriented flood flow routes. Because the southeast-oriented flood water was moving in anastomosing (or interconnected) channels reversed flood flow in newly beheaded flood flow channels often was able to capture yet to be beheaded flood flow from yet to be beheaded flood flow routes. Such captured flood waters then eroded valleys leading from a yet to be beheaded flood flow channel to the newly reversed flood flow channel. The northeast-oriented Tullock Creek tributary valleys were probably eroded by such yet to be beheaded southeast-oriented flood waters moving to the newly beheaded Tullock Creek flood flow route. Southwest-oriented Tullock Creek tributary valleys may have been initiated by yet to be beheaded southeast-oriented flood flow moving northeast to newly beheaded and reversed flood flow further northeast or may have been initiated as southeast-oriented flood flow became concentrated in a southeast-oriented Tullock Creek valley (that was subsequently reversed to become a northwest-oriented valley). In either case southeast-oriented flood flow once moved across the figure 3 map area on a topographic surface at least as high as the highest figure 3 elevations today. Headward erosion of the deep Yellowstone River valley then captured the southeast-oriented flood flow and caused reversals of flow on the northwest ends of the beheaded flood flow routes. Headward erosion of the deep Bighorn River valley south-southwest proceeded slightly in advance of headward erosion of Yellowstone River valley southwest of Custer because the Bighorn River valley captured and beheaded southeast-oriented flood flow routes. The net result of the regional erosion was flood waters that had been moving southeast across the figure 3 map area were captured and diverted northeast.

Bighorn River-Tullock Creek drainage divide area east of Foster

Figure 4: Bighorn River-Tullock Creek drainage divide area east of Foster. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates the Bighorn River-Tullock Creek drainage divide area south of the figure 3 map area and includes a small overlap area with figure 3. The north-northeast oriented Bighorn River flows north in the figure 4 west half and north and north-northwest oriented Tullock Creek is located along the figure 4 east edge. Bighorn River tributaries from the east are predominantly northwest oriented although there are exceptions. Tullock Creek tributaries from the west vary in orientation and include east, southeast and northeast orientations. The northwest-oriented Bighorn River tributaries provide evidence the deep north-northeast oriented Bighorn River valley eroded south-southwest to capture multiple southeast-oriented flood flow routes moving flood waters to what was then the newly reversed Tullock Creek valley. Shallow through valleys notched into the present day Bighorn River-Tullock Creek drainage divide provide evidence multiple channels of southeast-oriented flood water once flowed on a topographic surface at least as high as the highest points on that Bighorn River-Tullock Creek drainage divide today. East, northeast, and southeast oriented Tullock Creek tributary valleys were eroded by flood waters that crossed the present day drainage divide. Headward erosion of the deep Bighorn River valley then beheaded the southeast-oriented flood flow routes in sequence (from north to south) and caused reversals of flood flow on the northwest ends of he beheaded flood flow channels. The flood flow reversals eroded the northwest-oriented Bighorn River tributary valleys, which also resulted in the creation of the present day Bighorn River-Tullock Creek drainage divide. Erosion of the northwest-oriented Bighorn River tributary valleys was aided by capture of flood flow from yet to be beheaded southeast-oriented flood flow routes further to the south. For example, reversed flow on the Pocket Creek alignment probably captured yet to be beheaded southeast-oriented flood flow on the Brant Coulee alignment and the north and north-northwest oriented South Fork Pocket Creek valley was eroded by that captured flow.

Bighorn River-Tullock Creek drainage divide area north of the Dugout

Figure 5: Bighorn River-Tullock Creek drainage divide area north of the Dugout. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Bighorn River-Tullock Creek drainage divide area south of the figure 4 map area and includes an overlap area with figure 4. The north-oriented Bighorn River is located along the figure 5 west edge and north-oriented Tullock Creek is located along the figure 5 east edge. Bighorn River tributaries from the east are predominantly northwest-oriented. Tullock Creek tributaries from the west are predominantly east-northeast oriented. Shallow through valleys notched into the present day Bighorn River-Tullock Creek drainage divide link northwest-oriented Bighorn River tributary valleys with east-northeast-oriented Tullock Creek tributary valleys and provide evidence multiple channels of flood water once moved across the drainage divide. For example, note how the west-oriented Ninemile Creek valley is linked with the east-oriented Big Meadow Creek valley and how the west-oriented Little Ninemile Creek valley is linked with the east-oriented Lazy Man Creek valley. Two separate channels of flood water were required to establish these two linkages. Similar linkages can be found to the north and to the south of these two linkages suggesting multiple channels of flood flow, such as might be found in an anastomosing channel complex, crossed the present day drainage divide. The multiple channels of southeast-oriented flood flow were in the process of being captured by headward erosion of the newly reversed north-oriented Tullock Creek valley when headward erosion of the deep north-oriented Bighorn River valley captured the flood waters further to the west. Headward erosion of the Bighorn River valley beheaded the flood flow channels to the newly reversed Tullock Creek valley and flood waters on the northwest ends of the beheaded flood flow routes reversed flow direction to flow northwest (or west) to the newly eroded and much deeper north-oriented Bighorn River valley.

Bighorn River-Tullock Creek drainage divide area south of the Dugout

Figure 6: Bighorn River-Tullock Creek drainage divide area south of the Dugout. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates the Little Bighorn River-Tullock Creek drainage divide south of the figure 5 map area and includes an overlap area with figure 5. The northwest-oriented Little Bighorn River is located in the figure 6 west half. North-northwest oriented Tullock Creek is located in the figure 6 east half. Northwest oriented Dry Creek in the figure 6 northwest quadrant is a Bighorn River tributary (see figure 5 above). The northwest-oriented Tullock Creek tributary in the figure 6 northeast corner area is the East Fork of Tullock Creek. Northwest oriented Middle Fork of Tullock Creek joins the north-northwest oriented West Fork of Tullock in the figure 6 southeast corner (see figure 8 below). Northwest and northeast-oriented Ash Creek is a Tullock Creek tributary. Northeast-oriented Tullock Creek tributaries may have eroded southwest in sequence from what was then the newly reversed flood flow in the north-northwest oriented Tullock Creek valley to capture yet to be beheaded southeast-oriented flood flow on the Dry Creek and (northwest-oriented) Ash Creek alignments and also probably on the Little Bighorn River alignment. Headward erosion of the northeast-oriented Ash Creek valley segment then beheaded a southeast-oriented flood flow route (see northwest-oriented Dry Creek tributary on same alignment) and caused a reversal of flood flow that eroded the northwest-oriented Ash Creek valley segment. Headward erosion of the Bighorn River valley next beheaded southeast-oriented flood flow on the Dy Creek alignment causing a reversal of flood flow that eroded the northwest-oriented Dry Creek valley and tributary valleys and that created the Dry Creek-Ash Creek drainage divide. Subsequently headward erosion of the Bighorn River valley beheaded southeast-oriented flood flow on the Little Bighorn River alignment, which caused a major flood flow reversal that eroded the northwest-oriented Little Bighorn River valley. Figure 7 below illustrates in detail through valleys crossing the drainage divide between Dry Creek and Dawes Creek located east of the Dugout along the figure 6 north edge. The source of the immense southeast-oriented flood cannot be determined from evidence presented here. However, the hundreds of Missouri River drainage basin landform origins research project essays (published on this website) when used as a group to trace flood waters towards their source. Tracing flood waters reveals a path inconsistent with present day elevations, which suggests crustal warping and uplift has taken place since or that crustal warping and uplift was taking place as flood waters eroded the region. A logical flood water source would be rapid melting of a thick North American ice sheet located in a deep “hole” occupying approximately the North American location usually recognized to have been glaciated. Such an explanation would not only explain the immense southeast-oriented floods, but would also explain why deep valleys were eroding headward to capture the flood flow and divert the flood water further and further northeast into space in the deep “hole” the rapidly melting thick ice sheet had once occupied. Further, the presence of a thick North American ice sheet might explain crustal warping elsewhere on the North American continent, especially in locations where melt water flood erosion was removing large quantities of bedrock material.

Detailed map of Bighorn River-Tullock Creek drainage divide area east of the Dugout

Figure 7: Detailed map of Bighorn River-Tullock Creek drainage divide area east of the Dugout. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates in detail the Dry Creek-Dawes Creek drainage divide area shown in less detail in figure 6 located east of the Dugout (along the figure 6 north edge). Dry Creek flows southwest from the figure 7 center area and then west and northwest to the figure 7 west edge near the highway. Dawes Creek flows east-northeast to the figure 7 east center edge. Note the multiple through valleys crossing the present day Bighorn River-Tullock Creek drainage divide. One such through valley is used by the highway and links the southwest-oriented Dry Creek headwaters with a southeast-oriented Dawes Creek tributary valley. Another through valley is directly east of the small lake where Dry Creek turns from being southwest oriented to being west oriented. Still another through valley is located in the gravel pit area along the figure 7 north edge (center). These through valleys provide evidence multiple channels of flood water once flowed east across the present day Bighorn River-Tullock Creek drainage divide. Flood waters eroding the landscape seen today probably were flowing southeast on yet to be beheaded southeast-oriented flood flow routes west of the figure 7 map area (meaning the deep Bighorn River valley did not yet exist) to what was then the newly reversed flood flow on the newly beheaded Tullock Creek valley route. Headward erosion of the deep north-northeast oriented Bighorn River valley then captured the southeast-oriented flood flow routes that had been moving flood water across the figure 7 map area and caused reversals of flood flow that eroded the northwest-oriented Dry Creek valley and tributary valleys and also that created the Bighorn River-Tullock Creek drainage divide.

Bighorn River-Tullock Creek drainage divide area east of Crow Agency

Figure 8: Bighorn River-Tullock Creek drainage divide area east of Crow Agency. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates the Little Bighorn River-Tullock Creek drainage divide area south of the figure 6 map area and includes overlap areas with figure 6. The north-northwest oriented Little Bighorn River is located along the figure 8 west edge. Northwest oriented West Fork Tullock Creek flows from the figure 8 southeast corner area to the figure 8 north edge (east half) and is joined by northwest-oriented Middle Fork Tullock Creek, which flows from the figure 8 east edge (center). Northwest and west-oriented Custer Creek flows from the figure 8 south center area to the Little Bighorn River. Northwest and northeast-oriented Ash Creek flows to the figure 8 north edge (center) and north of figure 8 joins Tullock Creek (see figure 6). While the northwest-southeast orientation of major valleys in the figure 8 map area probably reflects the direction of flood flow across the region prior to being beheaded by headward erosion of the deep Yellowstone River and Bighorn River valleys, the figure 8 landscape was eroded almost entirely by reversed flood flow moving northwest to the newly eroded and much deeper Bighorn River and Yellowstone River valleys. Flood flow on the Tullock Creek alignment was beheaded and reversed first and for a time there was northwest-oriented water moving in the Tullock Creek drainage system and southeast-oriented water moving further to the west in the present day Little Bighorn River valley area (although the deep Little Bighorn River valley did not exist at that time). Northwest-oriented flow on the Tullock Creek alignment was capturing yet to be beheaded southeast-oriented flood flow from the Little Bighorn River alignment and the captured flood waters were responsible for eroding the northeast-oriented Tullock Creek tributary valleys. Headward erosion of the deep north-northeast oriented Bighorn River valley then beheaded southeast-oriented flood flow routes on the Little Bighorn River alignment and caused a major reversal of flood flow on that alignment. The reversed flood water eroded the north-northwest oriented Little Bighorn River valley and in the process created the Little Bighorn River-Tullock Creek drainage divide. The magnitude of the flood flow reversals seen here and in other evidence presented in this essay suggests the flood flow reversals were being aided by some other mechanism besides headward erosion of deep northeast-oriented valleys. Because southeast-oriented flood movements across the Bighorn River-Tullock Creek drainage divide area are not consistent with present day elevations the possibility that southern drainage divide areas were being uplifted relative to northern drainage divide areas needs to be considered. Such uplift may have been taking place as flood waters were moving across the region.

South end of Little Bighorn River-Tullock Creek drainage divide area

Figure 9: South end of Little Bighorn River-Tullock Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the south end of the Little Bighorn River-Tullock Creek drainage divide area. The north and north-northwest oriented Little Bighorn River is located in the figure 9 west half. Northwest oriented West Fork Tullock Creek is located in the figure 9 northeast corner area and various north and northeast oriented tributaries flow to it. Northwest and northeast oriented Dipping Vat Creek originates south of the highway. Northwest and west-oriented Custer Creek is located in figure 9 northwest quadrant. Northwest and west-oriented Reno Creek flows from the figure 9 southeast corner to the Little Bighorn River and northwest and southwest-oriented North Fork Reno Creek is located in the figure 9 center area. Headwaters of east-oriented tributaries to north- and northeast oriented Rosebud Creek are located in the figure 9 southeast corner. Rosebud Creek is north and east of Tullock Creek and flows to the Yellowstone River with the Tullock Creek-Sarpy Creek drainage divide area and Sarpy Creek-Rosebud Creek drainage divide area essays describing landform evidence between Tullock Creek and Rosebud Creek. The deep Yellowstone River valley was eroded headward from the northeast to the southwest and the deep Rosebud Creek valley eroded south and southwest before headward erosion of the Yellowstone River valley beheaded and reversed flood flow on the Tullock Creek alignment. For a time southeast-oriented flood flow moving across the present day Tullock Creek and Little Bighorn River drainage basins was moving to what was then the newly eroded and deep northeast and north-oriented Rosebud Creek valley. Headward erosion of the Yellowstone River valley then beheaded and reversed flood flow in the Tullock Creek drainage basin and the reversed flood flow eroded the north-oriented Tullock Creek valley and tributary valleys seen in figure 9, while yet to be beheaded southeast-oriented flood flow moving across the Little Bighorn River drainage basin continued to flow east and southeast to the northeast and north-oriented Rosebud Creek valley located south and east of the figure 9 map area. Headward erosion of the deep Bighorn River valley next beheaded southeast-oriented flood flow routes in the Little Bighorn River drainage basin and the reversed flood flow moved northwest to the newly eroded and much deeper Bighorn River valley. This reversal of flood flow eroded west-oriented Little Bighorn River tributary valleys, such as the Reno Creek valley, which previous to the flood flow reversal had been developing as a major flood flow route to the northeast and north-oriented Rosebud Creek valley. Figure 10 below illustrates a detailed map of the Custer Creek-North Fork Reno Creek drainage divide area.

Detailed map of Custer Creek-Tullock Creek drainage divide area

Figure 10 illustrates a detailed map of the Custer Creek-Tullock Creek drainage divide area illustrated in less detail in figure 9 above. Custer Creek flows from the figure 10 south center area to and through the figure 10 southwest quadrant. The southwest-oriented headwaters originate along the Little Bighorn River-Tullock Creek drainage divide. North-northeast-oriented Willow Creek flows to northwest-oriented West Fork Tullock Creek. The butte labeled Reno with an elevation of 4122 in the figure 10 southeast quadrant marks a triple drainage divide between Custer Creek to west and southwest, North Fork Reno Creek to the south, and Tullock Creek to the north and west. The through valley eroded across the Custer Creek-Tullock Creek drainage divide provides evidence flood water once moved from a southeast-oriented Custer Creek drainage basin to a north-oriented Tullock Creek drainage basin. That valley is almost 100 meters (more than 300 feet) lower than the butte marked Reno. Flood waters once flowed on a topographic surface at least as high as the butte labeled Reno, although regional elevations probably have changed significantly since that time with uplift occurring in the south. The flood flow reversals observed in this region suggest uplift may have been occurring as flood erosion was taking place. As previously noted many southeast-oriented flood flow movements described here and in other essays are not consistent with present day elevations. There are at least three ways to solve this elevation problem. One solution is to ignore evidence for southeast-oriented flood flow and to try to explain the evidence in some other way. I do not like to ignore evidence and reject the first solution for that reason. A second solution is to try to explain present day elevations by eroding immense quantities of bedrock material. While the evidence definitely makes a case for massive erosion, deep erosion of the continental surface could also trigger crustal warping and uplift and for that reason a combination of erosion and crustal warping and uplift probably best explains the evidence presented in these essays. When observed in little pieces such as these individual essays it is impossible to see the big picture. However, when viewed collectively evidence presented in the hundreds of Missouri RIver drainage basin landform origins research project essay builds a strong case that the northern Missouri River drainage basin is in fact the deeply eroded southwest wall of the deep North American “hole” once occupied by the rapidly melting thick ice sheet  responsible for the immense southeast-oriented floods described in the individual essays.

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.