Peoples Creek-Beaver Creek drainage divide area landform origins in Blaine and Phillips Counties, Montana, USA

· Little Rocky Mountains, Milk River, Montana
Authors

A geomorphic history based on topographic map evidence

Abstract:

The Peoples Creek-Beaver Creek drainage divide area is located in Blaine and Phillips Counties, Montana, USA. Although detailed topographic maps of the Peoples Creek-Beaver 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. Peoples and Beaver Creek are east and north oriented Milk River tributaries with Peoples Creek being located west and north of the Beaver Creek. The Peoples-Beaver Creek drainage divide area includes the Little Rockies Mountains. The Peoples Creek-Beaver 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 Milk 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 Peoples Creek-Beaver Creek drainage divide area landform origins in Blaine and Phillips Counties, Montana. 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 Peoples Creek-Beaver Creek drainage divide area landform evidence in Phillips and Blaine Counties, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Peoples Creek-Beaver Creek drainage divide area location map

Figure 1: Peoples Creek-Beaver 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 Peoples Creek-Beaver Creek drainage divide area location map. The Missouri River flows east-southeast from Fort Benton near the figure 1 west edge to Fort Peck Lake before joining the southeast-oriented Milk River and flowing to the figure 1 east edge. The Milk River flows southeast from Canada (in the figure 1 northwest corner) to Fresno Reservoir, Havre, Chinook, Harlem, Dodson, Malta, Saco, Hinsdale, and Glasgow and joins the Missouri River east of Nashua, Montana. Peoples Creek originates northwest of the Little Rocky Mountains and flows northeast to join the Milk River near Dodson. Beaver Creek flows southeast from the Little Rocky Mountains and then northeast and southeast before turning north and finally turns southeast and east to join the Milk River near Hinsdale. The Peoples Creek-Beaver Creek drainage divide area discussed here includes the Little Rocky Mountains. The southeast boundary of the drainage divide region discussed here is Beaver Creek and the Little Rocky Mountains. Peoples Creek and the Milk River form the northwest and northern boundary. 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 east-oriented Missouri River valley eroded west to near the location of Nashua (where the Milk River joins the Missouri River) and the Milk River valley eroded northwest and west to capture southeast-oriented flood water and to divert flood flow to the newly eroded Missouri River valley east of Nashua. Northeast, east, and north-oriented tributary valleys eroded headward from the newly eroded north-oriented Milk River valley and one such tributary valley was the valley now used by the northeast oriented Missouri River located southwest of Nashua. The northeast and north-oriented Beaver Creek valley eroded south from the newly eroded Milk River valley. Subsequently, as the deep Milk River valley eroded west, the northeast oriented Peoples Creek valley eroded southwest from the newly eroded Milk River valley to capture southeast-oriented flood flow moving to the newly eroded northeast and north oriented Beaver Creek valley. Flood waters on the ends of beheaded southeast-oriented flood flow routes reversed flow direction and eroded the present day northwest-oriented Peoples Creek tributary valleys. The Beaver Creek-Missouri River drainage divide area essay, Milk River-Missouri River drainage divide area between Beaver Creek and Larb Creek essay, the Milk River-Missouri River drainage divide area east of Larb Creek essay, and the Missouri River-Musselshell River drainage divide area essay describe drainage divide areas located near the Milk River-Missouri River drainage divide area discussed here and can be located under Milk River on the sidebar category list (Musselshell River for the Missouri River-Musselshell River essay).

Peoples Creek-Beaver Creek drainage divide area detailed location map

Figure 2: Peoples Creek-Beaver 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 Peoples Creek-Beaver Creek-Missouri River drainage divide area discussed in this essay. Blaine and Phillips Counties are located in Montana. The red shaded area is the Fort Belknap Indian Reservation. The Missouri River forms the county line in the figure 2 south half and flows southeast in the figure 2 southwest corner and flows northeast and east in the figure 2 southeast corner. The southeast oriented Milk River is located near the figure 2 north edge and flows through Malta before turning northeast and southeast to flow to the figure 2 east edge. Beaver Creek flows southeast and northeast from the Little Rocky Mountains (located in the indentation at the south end of the Fort Belknap Indian Reservation) to the 7th Auxiliary Guide Meridian and then turns southeast before turning north. Beaver Creek after flowing north turns southeast and east and joins the southeast oriented Milk River near Hinsdale. Peoples Creek originates in the Bear Paw Mountains west of figure 2. The Peoples Creek segment of concern in this essay flows southeast and northeast in the Fort Belknap Indian Reservation north of Three Buttes and then turns north to join the southeast oriented Milk River west of Dodson. Little Peoples Creek (also labeled Little Rocky Creek on figure 2) and Beaver Creek originate in the Little Rocky Mountains and this essay discusses drainage divides in the Little Rocky Mountains. Note the large number of southeast-oriented and northwest-oriented Beaver Creek tributaries and southeast-oriented Missouri River tributaries originating near the northeast-oriented Beaver Creek valley segment and south of the Little Rockies. Also note the southeast- and/or northwest-orientation of many valley segments including Missouri River, Milk River, Beaver Creek, Peoples Creek and Little Peoples Creek valley segments. Further, note northwest-oriented tributaries to Beaver Creek, Peoples Creek, and Little Peoples Creek. This southeast-northwest drainage alignment is evidence major trunk stream valleys eroded headward across and/or along multiple southeast-oriented flood flow channels such as might be found in a large southeast-oriented anastomosing channel complex. The northwest-oriented tributary valleys and/or valley segments were eroded by reversals of flood water on the northwest ends of beheaded southeast-oriented flood flow channels. Because channels were anastomosing (or interconnected) and because trunk stream valleys eroded headward, the reversed flood flow in newly beheaded channels could usually capture flood waters from adjacent yet to be beheaded flood flow channels. With the help of such captured yet to be beheaded flood waters the reversed flood flow in newly beheaded flood flow channels could often erode significant northwest-oriented valleys.

Milk River-Beaver Creek drainage divide area

Figure 3: Milk River-Beaver Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the Milk River-Beaver Creek drainage divide area at the northeast end of the Peoples Creek-Beaver Creek drainage divide area discussed in this essay. The Milk River is located in the figure 3 northwest corner and flows east to Malta where it turns northeast to flow to the figure 3 north edge. However a large east-oriented valley extends east from Malta to the north oriented Beaver Creek valley, which is located along the figure 3 east edge. The east-oriented valley suggests large volumes of flood waters once moved east in the Milk River valley. Northwest-oriented Alkali Creek is located in the figure 3 southwest corner and southeast-oriented Sevenmile Creek is located in the southeast quadrant. Other northwest oriented or barbed Milk River tributaries or valley segments of Milk River tributaries can be located. For example, southwest of Malta is northwest oriented Taylor Coulee and southeast of Malta Gonzales Coulees drains northwest to northeast oriented Black Coulee. Also other southeast-oriented or barbed Beaver Creek tributaries or tributary valley segments are present. For example, Lenoir Coulee in the figure 3 east center area drains southeast before turning northeast to join north oriented Beaver Creek. The northwest and southeast oriented barbed tributaries are evidence the Milk River valley, the Beaver Creek valley, and northeast oriented tributary valleys (such as the Black Coulee valley) eroded headward across multiple southeast-oriented flood flow channels such as might be found in a southeast-oriented anastomosing channel complex. Flood waters originally moved on a topographic surface at least as high as the highest figure 3 elevations today. The deep Milk River valley then eroded headward into that high level topographic surface to capture the southeast-oriented flood flow and northeast and north oriented tributary valleys eroded southwest and west from the actively eroding Milk River valley head to capture yet to be beheaded southeast-oriented flood flow routes further to the south. Flood waters on the northwest and north ends of beheaded southeast-oriented flood flow routes reversed flow direction to flow northwest or north to the newly and deeper Milk River valley. Because flood waters were moving in anastomosing (or interconnected) channels and because valleys eroded headward, often this reversed flood flow was able to capture flood flow from adjacent yet to be beheaded flood flow channels further to the south and southwest. With the help of such captured yet to be beheaded flood flow significant north- and northwest-oriented valleys were sometimes eroded. Figures below illustrate how the Beaver Creek valley eroded south and southwest to capture significant amounts of yet to be beheaded southeast-oriented flood flow and diverted the flood waters northeast and north to the newly eroded Milk River valley. Also figures below illustrate how headward erosion of the Peoples Creek valley beheaded and reversed southeast-oriented flood flow moving to what was then the newly eroded Beaver Creek valley.

Peoples Creek-Beaver Creek drainage divide area

Figure 4: Peoples Creek-Beaver Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates the Peoples Creek-Beaver Creek drainage divide area west of the figure 3 map area and includes a narrow overlap area with figure 3. The Milk River flows southeast from Dodson (located near the figure 4 north center edge) across the figure 4 northeast quadrant to the figure 4 east edge. Peoples Creek flows northeast from the figure 4 west center edge and turns to flow north-northwest to join the southeast oriented Milk River as a barbed tributary just north of the figure 4 north edge. Northwest-oriented Alkali Creek flows to the Milk River as a barbed tributary in the figure 4 east half. Going west from Alkali Creek are other barbed tributaries flowing to the Milk River, including northwest-oriented Davison Coulee. Note also northwest-oriented tributaries to northeast and north oriented Peoples Creek. For example, Mud Creek flows northwest to Peoples Creek and has northwest-oriented tributaries including the North Fork of Mud Creek. Mud Creek also has northeast-oriented tributaries, which have northwest-oriented tributaries. Southeast of Weigand Reservoir (the large reservoir in the figure 4 west center) drainage is southeast oriented and flows to northeast-southeast oriented Big Warm Creek, which flows to Beaver Creek. The Big Warm Creek elbow of capture, where it turns from flowing northeast to flowing southeast (to Beaver Creek), is located along the figure 4 south edge just east of the red highway. Figure 4 evidence can be interpreted in the context of an immense southeast oriented flood that flowed across the entire figure 4 map area on a topographic surface at least as high as the highest figure 4 elevations today. Headward erosion of the southeast- and east-oriented Milk River valley and its northeast-oriented tributary valleys (such as the Peoples Creek valley) captured southeast-oriented oriented flood flow and flood waters on the northwest ends of the beheaded southeast-oriented flood flow routes reversed flow direction to flow north and northwest to the newly eroded and deeper trunk stream valleys. Reversed flood flow eroded the north and northwest-oriented tributary valleys and often captured flood waters from yet to be beheaded southeast-oriented flood flow routes further to the south. Sometimes these captures of yet to be beheaded flood flow enabled the north and northwest-oriented tributaries to erode significant north- and northwest-oriented valley systems while also creating drainage divides with what had been actively eroding drainage systems further to the southeast.

Alkali Creek-Beaver Creek drainage divide area

Figure 5: Alkali Creek-Beaver Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Alkali Creek-Beaver Creek drainage divide area southwest of figure 3 and southeast of figure 4 and includes overlap areas with figures 3 and 4. Beaver Creek flows northeast from the figure 5 south center edge area to the figure 5 east center area and then turns southeast to flow to the figure 5 east edge. Northwest of the Beaver Creek elbow of capture is Alkali Flats and northwest of Alkali Flats is northwest-oriented Alkali Creek, which flows to the figure 5 north edge (east of the red highway). Little Warm Creek flows in an easterly direction across the red highway in the figure 5 southwest quadrant and then turns to flow north to join Big Warm Creek near Phillips. Big Warm Creek flows northeast and east from the figure 5 west edge to join Little Warm Creek at Phillips. From Phillips Big Warm Creek flows northeast for a short distance and then turns to flow southeast to join northeast-oriented Beaver Creek. Note the predominance of northwest-southeast oriented valleys and valley segments. This northwest-southeast streamlining of the figure 5 landscape resulted from southeast-oriented flood flow that once moved across the figure 5 map region and was systematically captured by headward erosion of the Beaver Creek valley system. Initially flood waters flowed southeast across the entire figure 5 map area on a topographic surface at least as high as the present day figure 5 highest elevations. Headward erosion of the deep north-oriented Beaver Creek valley east of the figure 5 map area (see Beaver Creek-Missouri River drainage divide area and Milk River-Missouri River drainage divide area between Beaver Creek and Larb Creek essays) captured the southeast-oriented flood flow and diverted flood waters north to what was then the newly eroded Milk River valley. The southeast-oriented Beaver Creek valley segment in figure 5 was one of the southeast-oriented flood flow routes headward erosion of the north-oriented Beaver Creek valley captured. The figure 5 northeast-oriented Beaver Creek valley segment eroded southwest from the southeast-oriented Beaver Creek valley to capture southeast-oriented flood flow routes further southwest. The figure 5 southeast-oriented Big Warm Creek valley segment was a flood flow route headward erosion of the figure 5 northeast-oriented Beaver Creek valley segment captured. And the process was repeated when a northeast-oriented valley eroded south from the southeast-oriented Big Warm Creek valley segment, which not only captured flood flow routes from the west, but which reversed flood flow on the northwest ends of beheaded flood flow routes to erode the north-northwest oriented Little Warm Creek valley segment immediately south of Phillips. The Big Warm Creek-Little Warm Creek drainage divide area at the northwest-southeast oriented Parrot Flat valley southwest of Phillips is shown in detail in figure 6 below.

Big Warm Creek-Little Warm Creek drainage divide area at Parrot Flat

Figure 6: Big Warm Creek-Little Warm Creek drainage divide area at Parrot FlatUnited States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates the Big Warm Creek-Little Warm Creek drainage divide area at Parrot Flat, which was illustrated in less detail in figure 5 above. Northeast-oriented  Big Warm Creek flows across the figure 6 northwest quadrant and north of figure 6 turns to flow east to join Little Warm Creek at Phillips. Little Warm Creek flows northeast and southeast in the figure 6 south center area and then east along the figure 6 south edge and east of figure 6 turns north to join Big Warm Creek at Phillips, located northeast of figure 6. Parrot Flat is located in a large northwest-southeast oriented through valley which extends across much of the north-oriented Beaver Creek drainage basin. Beaver Creek and various Beaver Creek tributaries cross the valley and/or flow for short distances in the valley before turning northeast or north to eventually flow to the Milk River. Note the northwest-oriented Big Warm Creek tributary located northwest of the small lake. The tributary provides evidence headward erosion of the northeast oriented Big Warm Creek valley captured southeast-oriented flow in the valley and diverted the flow northeast to Beaver Creek. Further, the tributary is evidence flood waters on the northwest end of the beheaded southeast-oriented flow route reversed flow direction to flow northwest to the newly eroded and deeper northeast oriented Big Warm Creek valley. The size of the southeast-oriented Parrot Flat valley suggests large volumes of southeast-oriented flood flow once moved in the valley. Further supporting this interpretation is the adjacent southeast-oriented valley located just to the southwest, which is now used by the figure 6 southeast-oriented Little Warm Creek valley segment. Note how the two southeast-oriented valleys are connected at both ends of the northwest-southeast erosional residual separating them. This evidence strongly suggests the two valleys were components of a southeast-oriented anastomosing channel complex that was systematically captured by headward erosion of the deeper northeast and north oriented Beaver Creek valley system. The source of the southeast-oriented flood waters 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 taken as a group can be used to trace flood waters both up flood to source areas and down flood to see where flood waters were going. 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. The deep “hole” would have been created by deep glacial erosion and by crustal warping caused by the ice sheet weight. Such a flood water source would not only explain the immense southeast-oriented floods this essay series describes, but would also explain why deep valleys were eroding headward to capture the southeast-oriented flood waters and diverting the flood waters further and further to the northeast and north into space in the deep “hole” the rapidly melting thick ice sheet had once occupied.

Peoples Creek-Beaver Creek drainage divides in eastern Little Rockies

Figure 7: Peoples Creek-Beaver Creek drainage divide area in eastern Little Rockies. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Peoples Creek-Beaver Creek drainage divide area in the eastern Little Rockies. Beaver Creek originates southwest of Beaver Mountain (located midway between Lodge Pole and the figure 7 south edge) and flows east, northeast, and southeast to the highway in the figure 7 southeast corner area and then flows east to the figure 7 east edge. The stream flowing north at Lodge Pole is Lodge Pole Creek which also originates southwest of Beaver Mountain. Lodge Pole Creek flows north and northwest from the figure 7 map area to join northeast-oriented South Fork Peoples Creek. Flowing north in the figure 7 north center area, just west of the Blaine County-Phillips County line, and then turning east to flow through a water gap eroded into Judith River Ridge is Big Warm Creek, which then flows northeast, southeast, northeast and north. The figure 6 map area is located in the figure 7 northeast corner. Little Warm Creek flows southeast between Travois Butte and Judith River Ridge to the southeast end of Judith River Ridge and then flows northeast before turning southeast near the figure 7 east edge. While Judith River Ridge is a northwest-southeast oriented hogback the through valley linking Little Warm Creek headwaters with the north-oriented Big Warm Creek valley provides evidence headward erosion of the north-oriented Big Warm Creek valley beheaded southeast oriented flood flow to the southeast oriented Little Warm Creek valley segment. Also note the meandering through valley extending from the southeast end of Judith River Ridge to the Beaver Creek valley. That meandering through valley provides evidence flood waters once flowed southeast from the Little Warm Creek headwaters area to the Beaver Creek valley in the figure 7 southeast corner. Perhaps even more interesting than through valleys along the Little Rocky Mountain margins are through valleys eroded across the Little Rocky Mountain uplifted mountain mass. These much higher level through valleys (or mountain passes) provide evidence water once moved across what is today a high isolated mountain area. Examples of such through valleys link north-oriented Lodge Pole Creek (which flows to Peoples Creek) with east-oriented Beaver Creek and with southeast oriented Ruby Gulch, which drains eventually to the Missouri River. Another interesting high level through valley links headwaters of southeast- and northeast oriented Bear Gulch (located along the figure 7 south edge) with the east-oriented Beaver Creek. Figure 8 below looks at some of the through valleys in detail.

Detailed map of eastern Little Rockies drainage divides

Figure 8: Detailed map of eastern Little Rockies drainage divides. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates a detailed map of through valleys across the Little Rocky Mountain highest area linking north and northwest-oriented Lodge Pole Creek (flowing to Peoples Creek) with southeast and northeast-oriented Beaver Creek headwaters and with southeast oriented Ruby Gulch (flowing to southeast oriented Camp Creek and the Missouri River). The figure 8 region is shown in less detail in figure 7 above. Green Mountain is located in the figure 8 northwest corner. Shell Butte is located south of Green Mountain in the figure 8 west center. Old Scraggy Peak is located east of Shell Butte. Beaver Mountain is located north of Old Scraggy Peak in the figure 8 north center. Lodge Pole Creek headwaters are located west of Green Mountain and have eroded a north-oriented valley. Beaver Creek originates between Green Mountain and Beaver Mountain and has eroded a southeast and northeast oriented valley. Ruby Gulch originates west of Shell Butte and a tributary originates between Shell Butte and Old Scraggy Peak. Through valleys linking headwaters of streams mentioned and other streams not mentioned are today high mountain passes, but figure 8 evidence suggests they are erosional features, which means water once flowed across the present day drainage divides. The water that flowed across those high mountain passes was southeast-oriented flood water. Note how the north-oriented Lodge Pole Creek valley is aligned with the southeast-oriented Ruby Gulch valley and is also linked to a northeast-oriented Beaver Creek tributary valley. If located on the plains away from the Little Rocky Mountains this drainage relationship would suggest southeast-oriented flood flow was moving on the present day Lodge Pole Creek route and was actively eroding the southeast-oriented Ruby Creek valley when headward erosion of the northeast-oriented Beaver Creek valley captured the southeast-oriented flood flow and beheaded flood flow routes to Ruby Gulch. Subsequently south-oriented flood flow on the Lodge Pole Creek route was beheaded by headward erosion of the northeast-oriented South Fork of Peoples Creek and flood waters on the northwest end of the beheaded flood flow route reversed flow direction to flow northwest to the South Fork Peoples Creek valley. Today the Little Rocky Mountains are an isolated mountain mass standing more than 1000 meters above the surrounding plains. Obviously if flood waters flowed across the Little Rocky Mountains the present day elevations did not exist. Several explanations appear possible. First, the Little Rockies mountain mass had been buried under bedrock layers (and perhaps ice from the melting ice sheet) and initially flood waters flowed on a topographic surface equivalent in elevation to the present day Little Rocky Mountain high elevations. If so flood waters removed immense amounts of materials surrounding the Little Rockies mountain mass. Such an explanation is more plausible if a significant amount of the surrounding material was ice. A second possible explanation is the Little Rockies mountain mass was uplifted as flood waters eroded the surrounding region. While such an explanation is inconsistent with most interpretations of Little Rocky Mountain geologic history, the removal of large volumes of overlying bedrock could trigger uplifts such as the Little Rocky Mountain uplift. Further, if the flood waters were derived from a rapidly melting thick North American ice sheet located in a deep “hole” that had been created by deep glacial erosion and ice sheet weight, then crustal warping elsewhere on the continent and especially along ice sheet margins might be a logical consequence. A third possibility is some combination of the first two explanations.

Peoples Creek-Missouri River drainage divide in western Little Rockies

Figure 9: Peoples Creek-Missouri River drainage divide in western Little Rockies. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Little Peoples Creek-Missouri River drainage divide area in the western Little Rocky Mountain area and includes an overlap area with figure 7. The figure 8 map area is also located in figure 9. Northwest-oriented Little Peoples Creek originates in the figure 9 center area and flows to the north oriented highway in the figure 9 northwest quadrant. North of figure 9 Little Peoples Creek flows north, northwest, and northeast to become the northeast-oriented South Fork Peoples Creek. Note the high level through valleys on both sides of Mission Peak linking north and northwest-oriented Little Peoples Creek tributary valleys with the south-oriented Rock Creek valley, which originates near Landusky. Rock Creek flows south and southeast to the southeast-oriented Missouri River valley located south of figure 9. Also note the high level through valley between Eagle Child Mountain and Indian Peak linking a northeast-oriented Little Peoples Creek tributary valley with headwaters of southwest-oriented Bull Creek, which flows to the Missouri River southwest of the figure 9 map area. The obstacles involved in moving flood waters across these mountain passes are just as challenging as those illustrated in figure 8 above. However map evidence suggests these three high level through valleys (and others like them) are erosional features and that at one time water flowed across them. The interpretation here is the water was southeast-oriented flood flow moving along what is today the northwest-oriented Little Peoples Creek valley alignment to what probably was then the actively eroding southeast-oriented Missouri River valley head (located south and east of figure 9-see Beaver Creek-Missouri River drainage divide essay for additional information). Flood flow across the present day Little Peoples Creek-Missouri River drainage divide ended when headward erosion of the deep northeast-oriented South Fork Peoples Creek valley beheaded the southeast-oriented flood flow route. Flood waters on the northwest end of the beheaded flood flow reversed flow direction to erode the present day north and northwest-oriented Little Peoples Creek valley segments. Reversed flood on the Little Peoples Creek alignment captured yet to be beheaded southeast oriented flood flow on the present day northwest-oriented Bradley Canyon alignment and with the help of that yet to be beheaded southeast-oriented flood flow was able to erode a significant north and northwest oriented valley. Figure 10 illustrates the through valleys in more detail.

Detailed map of through valleys across western Little Rockies

Figure 10: Detailed map of through valleys across western Little Rockies. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 illustrates a more detailed map of the through valleys illustrated and discussed in figure 9 above. Eagle Child Mountain is located in the figure 10 southwest corner. Mission Peak is located at the west end of the figure 10 southeast quadrant. The South Fork Big Horn Creek flows southwest from the figure 10 east center area and the northwest to the South Fork Little Peoples Creek, which flows north and northwest in the figure 10 north center area, where it is joined by west-southwest oriented North Fork to form northwest-oriented Little Peoples Creek. Note north to south oriented through valleys (or mountain passes) located on both sides of Mission Peak and also east of Eagle Child Mountain. Also note northwest-oriented Bradley Canyon north of Eagle Child Mountain and the through valley linking the northwest-oriented Bradley Canyon valley with an east and northeast-oriented valley leading to the north oriented South Fork Little Peoples Creek valley. The interpretation provided in the figure 9 discussion above is multiple channels of southeast-oriented flood water moved south through the three through valleys identified here. Flood waters were probably moving to what was then the actively eroding southeast-oriented Missouri River valley head. The through valley east of Mission Peak is the highest of three and was probably abandoned first. The valley east of Eagle Child Mountain is the lowest of three and was probably abandoned last. Abandonment of at least the last valley occurred because headward erosion of the South Fork Peoples Creek valley to the north and west of the figure 10 beheaded southeast-oriented flood flow moving south to the actively eroding Missouri River valley. Flood waters on the northwest end of the beheaded flood flow route reversed flow direction to flow northwest on the present day northwest-oriented Little Peoples Creek valley alignment. Because southeast-oriented flood flow routes were beheaded in sequence from the northeast to the southwest the reversed flood flow on the north and northwest-oriented Little Peoples Creek alignment was able to capture yet to be beheaded flood flow on the Bradley Canyon alignment. That yet to be beheaded flood flow moved southeast along the Bradley Canyon alignment and then made a U-turn and flowed north and northwest along the Little Peoples Creek alignment. With the aid of that yet to be beheaded southeast-oriented flood flow the deep north and northwest oriented Little Peoples Creek valley was eroded. Subsequently southeast-oriented flood flow on the Bradley Canyon alignment was beheaded and reversed to create the northwest-oriented Bradley Canyon valley.

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.

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