A geomorphic history based on topographic map evidence

The Little Bighorn River-Rosebud Creek (and Tongue River) drainage divide area is located in Montana, USA. This essay also includes Little Bighorn River-Tongue River drainage divide evidence located along the Montana-Wyoming state line. Although detailed topographic maps of the Little Bighorn River-Rosebud Creek (and Tongue River) 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 Little Bighorn River-Rosebud Creek (and Tongue River) 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 Little Bighorn River-Rosebud Creek (and Tongue River) 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 Little Bighorn River-Rosebud Creek (and Tongue River) drainage divide area landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Little Bighorn River-Rosebud Creek (and Tongue River) drainage divide area location map

Figure 1 provides a Little Bighorn River-Rosebud Creek (and Tongue River) drainage divide area location map and illustrates a region in southern Montana and northern Wyoming. The Yellowstone River flows from Billings in a northeast direction to Miles City and then to the figure 1 north edge. The Bighorn River originates in Wyoming south of the figure 1 map area and enters the figure 1 map area at Worland, Wyoming. After flowing north-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 originates in the northern Bighorn Mountains and flows northeast and northwest to join the Bighorn River at Hardin, Montana. Rosebud Creek originates in the Wolf Mountains area near the Montana-Wyoming state line and flows north, northeast, and north-northwest to join the Yellowstone River at Rosebud. The Tongue River also originates in the Wyoming Bighorn Mountains and flows northeast into Montana and shortly before reaching Miles City turns to flow northwest to join the northeast-oriented Yellowstone River as a barbed tributary. Based on evidence from the hundreds of Missouri River drainage basin landform origins research project essays published on this website landform evidence illustrated here 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 northeast by headward erosion of deep valleys eroded into a topographic surface at least as high as the figure 1 region highest elevations today.

• The northeast oriented Yellowstone River valley was one of the deep valleys that eroded southwest to capture the southeast-oriented flood water and to divert the flood flow northeast. North-oriented Yellowstone River tributary valleys eroded south from the actively eroding Yellowstone River valley head to capture yet to be beheaded flood flow south and southwest of the deep Yellowstone River valley head. North-oriented tributary valleys of concern in this essay include the Tongue River, Rosebud Creek, and the Bighorn River-Little Bighorn River valleys. Of these three valleys headward erosion of the northeast and northwest oriented Tongue River valley first captured the southeast-oriented flood flow and diverted the flood waters to the northeast-oriented Yellowstone River valley. As the deep Yellowstone River valley head eroded southwest the Rosebud Creek valley next eroded south to capture some of the southeast-oriented flood flow moving to the newly eroded Tongue River valley. And, as the deep Yellowstone River valley head continued to erode southwest headward erosion of the north-northeast oriented Bighorn River valley and northwest-oriented Little Bighorn River valley captured southeast-oriented flood flow routes moving water to the newly eroded Rosebud Creek valley and to the newly eroded Tongue River (south of the Rosebud Creek valley head). Detailed maps below provide evidence supporting this interpretation. This essay only addresses Little Bighorn River-Tongue River drainage divide area evidence northeast of the Bighorn Mountain front. The Bighorn River-Tullock Creek drainage divide area essay, the Tullock Creek-Sarpy Creek drainage divide area essay, and the Sarpy Creek-Rosebud Creek drainage divide area essay describe regions which are located east of the drainage divide area discussed here and can be found under Bighorn River or Yellowstone River on the sidebar category list.

Little Bighorn River-Rosebud Creek drainage divide area detailed location map

Figure 2: Little Bighorn River-Rosebud 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 Little Bighorn River-Rosebud Creek (and Tongue River) drainage divide area discussed in this essay. Big Horn County is located in Montana. The west to east boundary near the figure 2 south edge is the Montana-Wyoming state line. The Little Bighorn River-Rosebud Creek (and Tongue River) drainage divide area discussed here is located in the Wolf Mountains area of southeast Big Horn County, bounded by highways on all sides and includes a small area in northern Wyoming. Rosebud Creek originates in the Wolf Mountains and then flows north on the east side of the Wolf Mountains to Busby, Montana where it turns to flow northeast. The north-northeast oriented Bighorn River flows from the figure 2 west edge (south half) through the Crow Indian Reservation to Hardin. The Little Bighorn River flows northeast from the green National Forest area in the figure 2 southwest quadrant to Wyola (west of the Wolf Mountains) and then north-northwest and northwest to join the Bighorn River near Hardin. The Tongue River flows northeast from the figure 2 south center area to the figure 2 northeast corner. Figure 2 shows southeast-oriented Tongue River tributaries and Rosebud Creek tributaries (where Rosebud Creek is northeast oriented). Figure 2 also shows northwest-oriented tributaries to northeast and other north-oriented major drainage routes.  This southeast and northwest drainage alignment is evidence the northeast oriented Tongue River valley (and other valleys) eroded headward to capture southeast-oriented flood flow. The southeast-oriented tributary valleys were eroded by southeast-oriented flood flow moving into the newly eroded valleys and the northwest-oriented tributary valleys were eroded by reversals of flood flow on the northwest ends of beheaded southeast-oriented flood flow routes. Because flood waters move in and erode anastomosing (or inter-connected) 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 Little Bighorn River-Rosebud Creek drainage divide area immediately south of the north-oriented Tullock Creek headwaters area and then progress south along the Little Bighorn River-Rosebud Creek drainage divide area in the Wolf Mountains and conclude by looking at the Little Bighorn River (Owl Creek)-Tongue River drainage divide area south of Rosebud Creek headwaters area in the Wolf Mountains.

North end of Little Bighorn River-Rosebud Creek drainage divide area

Figure 3: North end of Little Bighorn River-Rosebud 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 Little Bighorn River-Rosebud Creek drainage divide area at the north end of the Wolf Mountains. North-oriented Rosebud Creek is located along the figure 3 east edge. North-oriented drainage in the figure 3 north center area flows to northwest and north-oriented Tullock Creek, which flows directly to the Yellowstone River. West-oriented drainage flowing to the figure 3 west edge flows to the north-northwest and northwest oriented Little Bighorn River, which flows to the north-northeast oriented Bighorn River, which in turn flows to the Yellowstone River. The major west-oriented drainage system is northwest and southwest-oriented Reno Creek, which flows to the figure 3 west edge center (northwest and west-oriented North Fork Reno Creek is located by the highway in the figure 3 northwest corner). Note how most Reno Creek tributaries are northwest oriented. The northwest orientation of the Reno Creek tributaries and headwaters is evidence the southwest-oriented Reno Creek valley eroded northeast to capture multiple southeast-oriented flood flow routes and that flood waters on the northwest ends of the beheaded flood flow routes reversed flow direction to flow northwest to the newly eroded southwest-oriented Reno Creek valley. Note also northwest oriented headwaters of the north-oriented drainage flowing to northwest- and north-oriented Tullock Creek. The northwest-orientation of the Tullock Creek headwaters is also evidence of reversals of southeast oriented flood flow on the northwest ends of beheaded flood flow routes. The north-oriented Rosebud Creek valley may also have been eroded by reversed flood flow, although more evidence is needed than that shown in figure 3. The northeast-oriented Rosebud Creek tributary valleys eroded headward to capture southeast oriented flood flow. The flood water source cannot be determined from evidence presented here. However, the hundreds of Missouri River drainage basin landform origins research project essays when taken as a group can be used to trace flood waters toward their source. Southeast-oriented flood flow across the Little Bighorn River-Rosebud Creek (and Tongue River) drainage divide is inconsistent with present day elevations. This inconsistency can be explained in one of three ways. First, evidence for southeast-oriented flood flow can be ignored or explained by some other mechanism. I reject this solution because ignoring evidence is dangerous and I have been unable to explain the evidence by other mechanisms. Second, the present day north-oriented slope was entirely produced by flood water erosion associated with headward erosion of the deep northeast-oriented Yellowstone River valley. While flood water erosion associated with headward erosion of the deep Yellowstone River definitely did deeply erode the region and contributed to the north-oriented regional slope for reasons which will become apparent in figure 10 below I doubt the north-oriented slope is entirely the result of flood water erosion. Third, the north-oriented slope was at least in part developed by uplift of the Bighorn Mountains area to the south as flood waters were eroding the region. This third possibility is discussed further as additional topographic map evidence is illustrated in figures shown below.

Little Bighorn River-Rosebud Creek drainage divide area in Wolf Mountains

Figure 4: Little Bighorn River-Rosebud Creek drainage divide area in Wolf Mountains. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 4 illustrates the Little Bighorn River-Rosebud Creek drainage divide area in the Wolf Mountains and is located south of the figure 3 map area and includes overlap areas with figure 3. West and northwest-oriented drainage in the figure 4 west half flows to the north-northwest and northwest oriented Little Bighorn River. East and northeast-oriented drainage in the figure 4 east half flows to north-oriented Rosebud Creek. Corral Creek is the northeast-oriented Rosebud Creek tributary flowing from the figure 4 south center edge to the figure 4 east center edge. Note southeast and northwest-oriented tributaries to Corral Creek, which provide evidence the northeast-oriented Corral Creek valley eroded headward to capture southeast-oriented flood flow. Note also northwest-oriented headwaters of east, north, and northeast-oriented Thompson Creek, which originates in the figure 4 center area. The northwest-oriented headwaters valley is evidence the east-oriented Thompson Creek valley segment eroded west to capture southeast-oriented flood flow moving to what was then the newly eroded Corral Creek valley. A reversal of flood flow on the northwest end of a beheaded flood flow route eroded the northwest-oriented Thompson Creek headwaters valley. Northwest-oriented Little Bighorn River tributary valleys (and/or valley segments) were also eroded by reversals of flood flow on the northwest ends of beheaded southeast-oriented flood flow routes. Because the southeast-oriented flood waters were moving in anastomosing (or interconnected) channels reversed flood flow in one channel could easily capture yet to be beheaded (and yet to be reversed) flood flow from adjacent channels. Such captures of yet to be beheaded flood flow provided the large quantities of water required to erode significant reversed flood flow valleys. A close look at figure 4 evidence reveals multiple through valleys notched into the present day drainage divide between the Little Bighorn River and Rosebud Creek. The through valleys provide evidence multiple channels of flood water once moved east from the present day Little Bighorn River drainage basin to the present day Rosebud Creek drainage basin. Water movement responsible for eroding those through valleys occurred before southeast-oriented flood flow in the Little Bighorn River drainage basin had been beheaded and reversed, but after headward erosion of the north-oriented Rosebud Creek valley had captured the southeast-oriented flood flow and had begun diverting flood waters east, north, and northeast to the deep Yellowstone River valley. Figure 5 below illustrates in detail through valleys in the South Fork Reno Creek-Corral Creek drainage divide area, which is located near the “F” in Wolf Mountains.

Detailed map of Little Bighorn River-Rosebud Creek drainage divide area in Wolf Mountains

Figure 5: Detailed map of Little Bighorn River-Rosebud Creek drainage divide area in Wolf Mountains. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 5 illustrates in detail through valleys crossing the Little Bighorn River-Rosebud Creek drainage divide in the South Fork Reno Creek-Corral Creek drainage divide area illustrated in less detail in figure 4 above. Corral Creek flows northeast from the figure 5 south edge to the figure 5 east edge. The South Fork Reno Creek flows northwest to the figure 5 northwest corner area. West-oriented drainage in the figure 5 southwest corner area are headwaters of northwest and west-oriented Shavings Creek, which flows to the Little Bighorn River. Note the through valley crossing the drainage divide between the Shavings Creek headwaters and an unnamed northeast and east-southeast oriented Corral Creek tributary valley. Also note the through valley linking that unnamed Corral Creek tributary valley with headwaters of northwest-oriented South Fork Reno Creek. Further, follow the Little Bighorn River-Rosebud Creek drainage divide further north in figure 5 and note additional through valleys notched into the ridge that serves as the present day drainage divide. Elevations of these through valleys imply significant amounts of water on both sides of the drainage divide were required to erode the present day valleys. Headward erosion of the Corral Creek valley and tributary valleys to capture southeast-oriented flood flow eroded valleys on the Rosebud Creek side of the divide. This erosion was occurring as flood waters were being systematically beheaded and reversed on the Little Bighorn River side of the drainage divide. What was happening in brief is an immense southeast-oriented flood moving in a southeast-oriented anastomosing channel complex was captured by headward erosion of an east- and northeast-oriented anastomosing channel complex. At the same time southeast-oriented flood flow was being beheaded and reversed further to the northwest. The beheading and reversal in the north was occurring headward erosion of the deep Yellowstone River-Bighorn River valley and was occurring from north (northeast) to south (southwest) and was beheading one flood flow channel at a time, which meant reversed flood flow on each beheaded flood flow channel was able to capture yet to be beheaded flood flow from adjacent yet to be beheaded channels. The Little Bighorn River-Rosebud Creek drainage divide illustrated in figure 5 is typical of drainage divides developed by such flood flow captures.

Little Bighorn River-Rosebud Creek drainage divide area east of Lodge Grass

Figure 6: Little Bighorn River-Rosebud Creek drainage divide area east of Lodge Grass. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 6 illustrates the Little Bighorn River-Rosebud Creek drainage divide area south of the figure 4 map area and includes overlap areas with figure 4. The north-oriented Little Bighorn River is located along the figure 6 west edge. North-northwest oriented Owl Creek flows from the figure 6 south edge (west half) to join the Little Bighorn River near Lodge Grass. Northwest-oriented Little Owl Creek flows from the figure 6 south center edge to join Owl Creek. Between Owl Creek and Little Owl Creek is northwest-oriented Dry Creek, which also flows from the figure 6 south edge to join Owl Creek. West-northwest and southwest oriented Grey Blanket Creek originates near the headwaters of northeast-oriented Corral Creek in the figure 6 northeast quadrant and is linked by through valleys with the northeast-oriented Corral Creek valley (figure 7 below illustrates the through valley in detail). The through valley provides additional evidence flood water once moved west from the present day Little Bighorn River drainage basin to the Rosebud Creek drainage basin. Additional and similar through valleys, including Sioux Pass, can be found by following the Little Bighorn River-Rosebud Creek drainage divide ridge. As previously mentioned an east-oriented anastomosing channel complex was capturing a southeast-oriented anastomosing channel complex at the same time headward erosion of a deep valley to the north of figure 6 was systematically beheading flood flow in the southeast-oriented anastomosing complex. How could an immense southeast-oriented flood such as one described by this evidence originate and why would deep valley systems erode headward to capture the flood waters and divert the flood flow northeast? Again as previously mentioned the answers cannot be found in evidence illustrated here. However a logical answer is rapid melting of a thick North American ice sheet that was located in a deep “hole” occupying approximately the North American location usually considered to have been glaciated would explain the immense southeast-oriented flood source. Further, rapid melting of such a thick North American ice sheet (located in a deep “hole” that had been created by deep glacial erosion and crustal warping due to the ice sheet weight) would also explain why deep valleys were eroding headward to capture southeast-oriented melt water floods and to divert flood waters northeast into space in the deep “hole” the rapidly melting ice sheet had once occupied. Further, crustal warping caused by such an ice sheet could also explain crustal warping along ice sheet margins and elsewhere in the continent and might help explain why regions, such as the Bighorn Mountains area, were being uplifted as flood erosion of the region progressed.

Detailed map of Grey Blanket Creek-Corral Creek drainage divide area in Wolf Mountains

Figure 7 illustrates a detailed map of the Grey Blanket Creek-Corral Creek drainage divide area south and west of the figure 5 map area and includes overlap areas with figure 5 (the figure 7 map area is also shown in less detail figure 6 above). Northwest oriented Shavings Creek is located in the figure 7 northwest quadrant. Note the previously mentioned through valley linking the northwest-oriented Shavings Creek headwaters with headwaters of an unnamed northeast and east oriented Corral Creek tributary. Northwest, west, and southwest-oriented Grey Blanket Creek is located in the north half of the figure 7 southwest quadrant. Note how through valleys are notched into the ridge that serves as the drainage divide between the Grey Blanket Creek headwaters and the Corral Creek valley. A west-northwest oriented unnamed Grey Blanket Creek tributary is located in the south half of the figure 7 southwest quadrant. Corral Creek flows northeast in the figure 7 east center area to the figure 7 east edge (north half). Note the well-defined through valley (used by the road) linking the unnamed Grey Blanket Creek tributary valley with the Corral Creek valley. All of these through valleys and others provide evidence of multiple flood flow routes that once moved flood waters from the present day Little Bighorn River drainage basin area to the present day Rosebud Creek drainage basin area. Again as previously mentioned these through valleys and the present day Little Bighorn River-Rosebud Creek drainage divide are best explained in the context of headward erosion of a northeast and east oriented anastomosing channel complex to capture an immense flood moving in a southeast-oriented anastomosing channel complex, where flood flow in the southeast-oriented anastomosing channel complex was being beheaded further to the north by headward erosion of a deep northeast-oriented valley.

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

Figure 8: South end of Little Bighorn River-Rosebud Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 8 illustrates the south end of the Little Bighorn River-Rosebud Creek drainage divide area and a segment of the Owl Creek (a Little Bighorn River tributary)-Tongue River drainage divide area (figure 8 includes overlap areas with figure 6). Rosebud Creek flows east-northeast, north, east, and north in the figure 8 north center area and northeast quadrant. Northwest-oriented drainage in the figure 8 northwest corner is Kid Creek, which flows to northwest-oriented Little Owl Creek (the northwest-oriented “Creek” south of Kid Creek). Northwest-oriented Little Bear Creek in the figure 8 southwest corner flows to west-oriented Bear Creek and then to northwest and north-northwest oriented Owl Creek. Southeast-oriented drainage flows to the northeast-oriented Tongue River located southeast of the figure 8 map area. Figure 8 evidence can best be explained by southeast-oriented flood flow moving across the figure 8 map area on a topographic surface at least as high as the highest figure 8 elevations today. Headward erosion of the deep northeast-oriented Tongue River valley captured the southeast-oriented flood flow and southeast-oriented tributary valleys eroded headward from the newly eroded and deep Tongue River valley northwest wall. The deep Rosebud Creek valley then eroded south, southwest, and west-southwest to capture the southeast-oriented flood flow and was in the process of doing so when flood waters were beheaded and reversed causing a major reversal of flood flow along the figure 8 west edge (and west of figure 8). Shallow through valleys link headwaters of southeast-oriented Tongue River tributaries with the Rosebud Creek valley and provide evidence headward erosion of the Rosebud Creek valley beheaded multiple southeast-oriented flood flow channels. Reversed flood waters must have captured significant amounts of yet to beheaded and yet to be reversed flood waters from flood flow routes further to the west and southwest because the reversed flood waters were able to erode a significant north-northwest oriented valley and drainage basin. Multiple through valleys link the northwest-oriented Kid Creek valley and tributary valleys with the Rosebud Creek valley and provide evidence the reversal of flood flow in the Kid Creek valley (and Little Owl Creek valley) beheaded southeast-oriented flood flow to the actively eroding Rosebud Creek valley and created the present day Kid Creek-Rosebud Creek drainage divide.

Owl Creek-Tongue River drainage divide area along state line

Figure 9: Owl Creek-Tongue River drainage divide area along state line. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 9 illustrates the Owl Creek-Tongue River drainage divide area south and slightly west of the figure 8 map area and includes overlap areas with figure 8. The west to east oriented boundary line in the figure 9 south half is the boundary between Montana (north) and Wyoming (south). The northeast-oriented Tongue River is located in the figure 9 southeast corner. North-northeast and north-northwest oriented Owl Creek is located along the figure 9 west edge. West-oriented Bear Creek and northwest-oriented Little Bear Creek are located in the figure 9 northwest corner and flow to Owl Creek. Southeast-oriented drainage flows to the northeast-oriented Tongue River. As described in the figure 8 discussion the figure 9 evidence can best be explained by southeast-oriented flood water moving across the entire figure 9 map area on a topographic surface at least as high as the highest figure 9 elevations today. Headward erosion of the deep northeast-oriented Tongue River valley next captured the southeast-oriented flood water and diverted the flood flow northeast. Multiple southeast-oriented flood flow channels then eroded southeast-oriented valleys headward into the newly eroded and deep Tongue River valley northwest wall. Headward erosion of the deep north-northeast and north-west oriented Owl Creek valley then beheaded the southeast-oriented flood flow routes to the newly eroded Tongue River valley. Through valleys link headwaters of the southeast-oriented Tongue River tributaries with the north-northeast and north-northwest Owl Creek valley and provide evidence of the original southeast-oriented flood flow and also that headward erosion of the Owl Creek valley beheaded the southeast-oriented flood flow. The north-oriented Owl Creek valley was eroded by reversed flood flow on the northwest ends of beheaded southeast-oriented flood flow routes. The southeast-oriented flood flow routes were beheaded by headward erosion of the deep Yellowstone River-Bighorn River valley located north and west of the Little Bighorn River-Rosebud Creek drainage divide area discussed here. The north-oriented Owl Creek valley was eroded by large quantities of yet to be beheaded southeast-oriented flood flow captured by reversed flood waters moving north and northwest on the Owl Creek alignment. Figure 10 below provides some evidence as to how that captured flood flow reached the newly reversed Owl Creek valley.

South end of Owl Creek-Tongue River drainage divide area along state line

Figure 10: South end of Owl Creek-Tongue River drainage divide area along state line. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 10 illustrates the south end of the Owl Creek-Tongue River drainage divide area and includes overlap areas with figure 9. The west to east Montana-Wyoming state line divides the figure 10 north and south halves. The northeast-oriented Tongue River is located in the figure 10 southeast corner (along the south edge east of Ranchester). The northeast-oriented stream in the figure 10 northwest corner is the Little Bighorn River. Northeast-oriented Pass Creek flows from the figure 10 west center edge to Aberdeen and then northwest to the figure 10 north edge and to join the Little Bighorn River north of the figure 10 map area. Hogbacks along the Bighorn Mountains northeast flank are located in the figure 10 southwest corner. Owl Creek flows north-northeast from west of Wolf Mountain (located along the state line) to the figure 10 north edge. Southeast-oriented drainage flowing to the figure 10 east edge flows to the northeast-oriented Tongue River. While many figure 10 landscape features provide evidence of southeast-oriented flood flow that was captured by reversed flood flow moving north in the Owl Creek and Pass Creek valleys the most remarkable figure 10 landscape feature is the large northwest-southeast oriented through valley eroded between the Bighorn Mountain hogbacks and Wolf Mountain. Through valley is a major transportation route and is used by the highway and railroad and is a major link between the deep northeast-oriented Tongue River valley with the north, north-northwest, and northwest-oriented drainage and the deep Bighorn River valley. Wolf Mountain stands almost 1000 feet (300 meters) higher than the through valley floor. The through valley provides evidence southeast-oriented flood flow moved from the present day Bighorn River drainage basin to what was then the newly eroded deep northeast-oriented Tongue River valley and also provides clues as the immense magnitude of the flood flow involved and the magnitude of erosion flood waters accomplished. Also figure 10 evidence provides clues as to magnitude of the flood flow reversal that eroded the north-oriented Owl Creek valley, which  captured yet to be beheaded southeast-oriented flood flow still moving across the present day north-oriented Little Bighorn River drainage basin. The north-oriented Little Bighorn River valley (north of the figure 10 map area) was subsequently eroded by an even larger reversal of flood flow. In summary, evidence illustrated in this essay suggests southeast-oriented flood flow eroded the present day Little Bighorn River-Rosebud Creek (and Tongue River) drainage divide area and massive flood erosion occurred along the Bighorn Mountain northeast flank, which suggests flood erosion may have occurring as the Bighorn Mountains area was being uplifted.

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.