A geomorphic history based on topographic map evidence

The Beaver Creek-Missouri River drainage divide area is located in southern Phillips County, Montana, USA. Although detailed topographic maps of the Beaver Creek-Missouri 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. Beaver Creek is an east and north oriented Milk River tributary with the Milk River being an east oriented Missouri River tributary located north of the Missouri River. The Beaver Creek-Missouri 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 Milk and Missouri River valleys captured all southeast-oriented flood flow.

Preface:

Introduction:

• The purpose of this essay is to use topographic map interpretation methods to explore Beaver Creek-Missouri River drainage divide area landform origins in Phillips County, 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 Beaver Creek-Missouri River drainage divide area landform evidence in Phillips County, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Beaver Creek-Missouri River drainage divide area location map

Figure 1: Beaver Creek-Missouri River 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 Beaver Creek-Missouri River drainage divide area location map. The Missouri River flows in an east-southeast direction from the figure 1 west edge to Fort Peck Lake before joining the southeast-oriented Milk River and flowing to Brockton, Montana near the figure 1 east edge. The Milk River flows from the northwest corner area to Havre, Chinook, Harlem, Dodson, Malta, Saco, Hinsdale, and Glasgow and joins the Missouri River east of Nashua, Montana. The Beaver Creek-Missouri River drainage divide area discussed here is located between the Little Rocky Mountains and the Missouri River. Southeast-oriented Beauchamp Creek is located in the Beaver Creek-Missouri River drainage divide area discussed here. 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 unnamed south-oriented stream flowing south of Regina is Second Creek, which then joins an unnamed south-oriented stream to flow to the Missouri River. The unnamed south-oriented stream is Telegraph Creek, and Telegraph Creek also serves as eastern boundary for the drainage divide region discussed here. The northwest boundary of the drainage divide region discussed here is Beaver Creek, the Little Rocky Mountains, and southwest-oriented Bull Creek, which flows from the Little Rockies to join the Missouri River near the point where southeast-oriented Cow Creek joins the Missouri River. The Missouri River is the southern 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 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 north-oriented Beaver Creek valley segment eroded south from the newly eroded Milk River valley along what is today a south-oriented Telegraph Creek valley segment and southwest and west from there. However, the present day northeast-oriented Missouri River valley, beheaded north-oriented flood flow to the north-oriented Telegraph Creek-Beaver Creek valley. Flood waters on the south end of the beheaded north-oriented flood flow route reversed flow direction and eroded the present day south-oriented Telegraph Creek valley segment. The 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. The first two essays can be found under Milk River on the sidebar category list and the third essay can be found under Musselshell River, while all three essays can be found under MT Missouri River.

Beaver Creek-Missouri River drainage divide area detailed location map

Figure 2: Beaver Creek-Missouri River 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 Beaver Creek-Missouri River drainage divide area discussed in this essay. Phillips County is located in Montana. The Missouri River forms the county line in the figure 2 south half and flows southeast to UL Bend where it joins the north-oriented Musselshell River (south of the figure 2 south edge). From UL Bend the Missouri River flows northeast and east to the figure 2 east edge. The east and southeast-oriented Milk River swings into the figure 2 north edge area and flows through Malta before turning northeast to flow to the figure 2 north edge. Beaver Creek flows southeast and northeast from the Little Rocky Mountains (near figure 2 west edge) 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. Southeast-oriented Flat Creek flows to the 7th Auxiliary Guide Meridian south of Beaver Creek and then turns north to join north-oriented Beaver Creek. South of the Flat Creek elbow of capture in the Sun Prairie region is another interesting elbow of capture where northwest oriented Telegraph Creek turns to flow south to the Missouri River. Telegraph Creek is a northwest, south-southwest and southeast oriented Missouri River tributary located southeast of Sun Prairie in the figure 2 south center area. Telegraph Creek flows south in a large through valley that forms the eastern boundary for the drainage divide region discussed in this essay. Beaver Creek flows north in the same through valley and Flat Creek (near Sun Prairie) is a north-oriented Beaver Creek tributary that also drains the through valley. Beaver Creek originates in the Little Rocky Mountains and this essay discusses drainage divides in the Little Rocky Mountains and also drainage divides between southwest-oriented Bull Creek and the Missouri River. Bull Creek flows southwest from the Little Rocky Mountains to the southeast-oriented Missouri River. 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 near the southwest-oriented Bull Creek alignment, which extends southwest from the Little Rockies to the Missouri River. This southeast-northwest drainage alignment is evidence major trunk stream valleys eroded headward across multiple southeast-oriented flood flow channels such as might be found in a large southeast-oriented anastomosing channel complex. The northwest-oriented tributary valleys 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.

Beaver Creek-Flat Creek drainage divide area

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

Figure 3 illustrates the Beaver Creek-Flat Creek drainage divide area and the Big Sag through valley linking the Beaver Creek valley with the north-northeast oriented Sun Prairie Flats through valley. Beaver Creek flows southeast from the figure 3 west edge and then turns northeast to flow to the figure 3 north center area, Near the figure 3 north center edge Beaver turns abruptly to flow southeast to the north-northeast oriented Sun Prairie Flats through valley, where Beaver Creek makes another abrupt turn to flow northeast in the north extension of the Sun Prairie Flats through valley. The Big Sag is a large northwest-southeast oriented through valley in the figure 3 south center linking the southeast-northeast oriented Beaver Creek valley with the north-northeast oriented Sun Prairie Flats through valley. The Big Sag is drained by southeast-oriented Flat Creek, which upon entering the Sun Prairie Flats through valley turns to flow north-northeast to join Beaver Creek. Note other southeast-oriented drainage routes in the figure 3 northwest quadrant and in the Beaver Creek-Flat Creek drainage divide area. For example, Little Sevenmile Creek flows southeast in the Beaver Creek-Flat Creek drainage divide area to join northeast-oriented Flat Creek. Also note northwest-oriented Camp Coulee flowing from near Mitchell Corner in the Beaver Creek-Flat Creek drainage divide area to join northeast-oriented Beaver Creek and also northwest-oriented Flat Creek tributaries flowing into the Sun Prairie Flats through valley. The numerous small lake basins in figure 3 suggest the possibility that remnants of a decaying ice sheet may have been present when flood waters crossed the region, although without additional evidence other explanations are possible. The figure 3 drainage evidence can be explained in the context of an immense southeast-oriented flood, which originally flowed across the entire figure 3 map area on a topographic surface at least as high as the highest figure 3 elevations today. Headward erosion of the north-northeast-oriented Beaver Creek-Sun Prairie Flats valley (probably from what was then a newly eroded east and southeast-oriented Milk River valley in the north) captured the southeast-oriented flood flow and southeast-oriented tributary valleys began to erode northwest from the newly eroded north-northeast oriented Sun Prairie Flats valley. These actively eroding southeast-oriented tributary valleys include the southeast-oriented Beaver Creek valley (which eroded headward toward the figure 3 north edge), the Little Sevenmile Creek valley, and the southeast-oriented Flat Creek valley (in the Big Sag). A northeast-oriented tributary valley then eroded southwest from the actively eroding southeast-oriented Beaver Creek valley to capture southeast-oriented flood flow moving to the actively eroding southeast-oriented Little Sevenmile Creek and Flat Creek valleys. Flood flow on the northwest end of a beheaded southeast-oriented flood flow route reversed flow direction and eroded the northwest-oriented Camp Coulee valley. The northeast-oriented Beaver Creek valley captured the southeast-oriented flood flow that was eroding the southeast-oriented Flat Creek valley (the Big Sag valley). Subsequently north-oriented flood flow in the Sun Prairie Flats  valley was beheaded in the south and flood waters on the south end of the beheaded north-oriented flood flow route reversed flow direction to erode the south-oriented Telegraph Creek valley, which is illustrated in figure 6 below. The size of the Sun Prairie Flats and Big Sag valleys suggests large volumes of flood water eroded those and some of the other figure 3 valleys. Figures below suggest sources for at least some of the large volumes of flood water required.

Beaver Creek-First and Second Creek drainage divide areas

Figure 4: Beaver Creek-First and Second Creek drainage divide areas. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 4 illustrates the Beaver Creek-First Creek and Beaver Creek-Second Creek drainage divide areas south and west of the figure 3 map area and includes overlap areas with figure 3. The southeast-oriented Big Sag and southeast-oriented Flat Creek headwaters are located in the figure 4 northeast corner area. South of the southeast-oriented Big Sag is southeast-oriented North Fork First Creek and then southeast-oriented First Creek, which flows to the figure 4 east edge and then to the Sun Prairie Flats through valley where its course is lost. In the figure 4 southwest quadrant is southeast-oriented Second Creek, which flows to the figure 4 south center edge and then to the Sun Prairie Flats through valley, where it joins south-oriented Telegraph Creek and flows to the Missouri River. Beaver Creek flows northeast from the figure 4 west center edge to the figure 4 north center edge where it flows east in the northwest extension of the Big Sag valley and then turns northeast as seen in figure 3. Note southeast-oriented drainage in the figure 4 northwest corner area to northeast-oriented Beaver Creek. Again small lake basins in the figure 4 map area may provide evidence of the presence of a decaying ice sheet remnant at the time southeast-oriented flood waters moved across the region, although based on topographic map evidence alone other explanations may be possible. Figure 4 evidence can also be explained by an immense southeast-oriented flood flowing across the entire figure 4 map area to a newly eroded north-oriented Sun Prairie Flats valley east of the figure 4 map area. Southeast-oriented tributary valleys then eroded headward from what was then the newly eroded Sun Prairie Flats valley west wall. These actively eroding southeast-oriented tributary valleys included the southeast-oriented Flat Creek valley (now the southeast-oriented Big Sag), the southeast-oriented First Creek and North Fork First Creek valleys, and the southeast-oriented Second Creek valley. The northeast-oriented Beaver Creek valley in figure 4 eroded southwest from the southeast-oriented Flat Creek valley (or Big Sag valley) to capture southeast-oriented flood flow moving to what were then the actively eroding southeast-oriented North Fork First Creek, First Creek, and Second Creek valleys. Southeast-oriented tributary valleys then were eroded into the newly eroded northeast-oriented Beaver Creek valley. The figure 4 drainage pattern has not changed since.

Beaver Creek-Dry Fork Creek drainage divide area

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

Figure 5 illustrates the Beaver Creek-Dry Fork Creek drainage divide south and west of the figure 4 map area and includes overlap areas with figure 4. Beaver Creek flows southeast from the figure 5 northwest corner and in the figure 5 north center area turns to flow northeast to the figure 5 northeast corner. Dry Fork Creek flows southeast from the figure 5 west center area to the figure 5 southeast quadrant and south edge. Southeast of figure 5 Dry Fork Creek joins southeast-oriented Beauchamp Creek and flows to the Missouri River. Southeast-oriented Beauchamp Creek flows from the figure 5 west edge to Bison Bone Reservoir and then to the figure 5 south center edge. Again the presence of small lake basins may be evidence that a decaying ice sheet was present at the time flood waters moved across the figure 5 map region, however without additional evidence other explanations are also possible. Note the multiple through valleys linking southeast-northeast oriented Beaver Creek in its elbow of capture area with the southeast-oriented Dry Fork Creek valley, The multiple dry valleys are evidence of anastomosing southeast-oriented flood flow channels linking the southeast-oriented Beaver Creek headwaters with the southeast-oriented Dry Fork Creek valley. In other words, the southeast-oriented Dry Fork Creek valley was eroded by southeast-oriented flood flow from the Beaver Creek drainage basin northwest of the figure 5 map region that was subsequently captured by headward erosion of the north-oriented Beaver Creek valley. Figures 7 and 8 illustrate the Beaver Creek headwaters northwest of the figure 5 map area are in the Little Rocky Mountains, which poses some interesting questions to be addressed in the figures 7 and 8 discussions. Evidence seen so far in this essay makes a strong case for an immense southeast-oriented flood that flowed across Phillips County, Montana. 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.

Drainage divides in UL Bend area

Figure 6: Drainage divides in UL Bend area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 6 illustrates the UL Bend area at the southeast corner of the Beaver Creek-Missouri River drainage divide area discussed in this essay and does not include overlap areas with previous figures. The Missouri River flows southeast from the figure 6 west edge to UL Bend south of the figure 6 south center edge and then flows northeast from UL Bend to the figure 6 east edge. The Missouri River valley in figure 6 has been flooded by Fort Peck Lake, which is a large reservoir impounded behind Fort Peck Dam. At UL Bend, south of figure 6, the north oriented Musselshell River joins the Missouri River. In the figure 6 northeast corner south-oriented Telegraph Creek flows south from the south end of the Sun Prairie Flats valley seen in figure 3 and then turns southeast and east to flow to the Missouri River east of figure 6. Hawley Flats in the figure 6 center south area is drained by east-southeast and north oriented Valentine Creek, which in the figure 6 northeast quadrant joins southeast and northeast-oriented Fourchette Creek to flow to south-oriented Telegraph Creek as a barbed tributary. At the west end of Hawley Flats south-oriented Hawley Creek turns west to flow the southeast-oriented Beauchamp Creek valley and the Missouri River (along the figure 6 west center edge). Figure 6 evidence can also be explained in the context of an immense southeast-oriented flood moving across the entire figure 6 map area on a topographic surface at least as high as the highest present day figure 6 elevations. Headward erosion of the deep northeast-oriented Missouri River valley first captured the flood waters and the valley eroded south from the figure 6 map area along the present day north oriented Musselshell River valley alignment to capture additional southeast-oriented flood flow routes (see Missouri River-Musselshell River drainage divide essay). At about the same time the north oriented Beaver Creek-Sun Prairie Flats valley eroded south from what was then the newly eroded southeast-oriented Milk River valley (see Milk River-Missouri River drainage divide area between Beaver Creek and Larb Creek essay) and on reaching the figure 6 map area eroded a valley west to capture southeast-oriented flood water moving to the newly eroded north and northeast-oriented Musselshell-Missouri River valley. Apparently the volume of flood flow in the east and north oriented valley was such that flood waters spilled southeast from that valley into the adjacent north and northeast oriented valley. Two major breaches developed. The eastern breach took place along what is today the southeast oriented Telegraph Creek valley segment. That breach beheaded north oriented flood flow into the north-oriented Sun Prairie Flats-Beaver Creek valley and caused a reversal of flood flow on the south end of the Sun Prairie Flats valley to create the present day Telegraph Creek drainage system. The second breach took place along what is today the figure 6 southeast-oriented Missouri River alignment. With that breach the north- and northeast-oriented Musselshell-Missouri River valley captured what is today the entire Missouri River drainage basin upstream from figure 6. Also, with that breach flood waters on west end of the east- and north-oriented Hawley Flats-Sun Prairie Flats-Beaver Creek valley were beheaded and reversed to create the present day west-oriented Hawley Creek drainage basin.

Beaver Creek-Beauchamp Creek drainage divide area

Figure 7: Beaver Creek-Beauchamp Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 7 illustrates the Beaver Creek-Beauchamp Creek drainage divide in the eastern Little Rocky Mountains west and north of figure 5 and includes overlap areas with figure 5. Beaver Creek originates southwest of Beaver Mountain (located in figure 7 northwest corner area) and flows east and northeast in the Little Rocky Mountains and then flows southeast across the figure 7 center area to the figure 7 east edge. Bear Gulch is a southeast and northeast-oriented Beaver Creek tributary originating west of Bear Mountain and joins Beaver Creek in the figure 7 center area. Note the through valley linking the Bear Gulch headwaters with the Beaver Creek valley. That through valley is evidence water once flowed south from the present day Beaver Creek valley to the present day Bear Gulch valley and for a time at least water flowed from the Beaver Creek valley both northeast and southeast along the present day Beaver Creek route and south and southeast along the Bear Gulch route. Further, note how the southeast-oriented Bear Gulch valley segment is linked by a though valley with southeast-oriented Beauchamp Creek. These through valleys and others like them define a southeast-oriented anastomosing maze of channels that once crossed what is today the Little Rockies upland region. Figure 8 below illustrates the Little Rockies upland region so the complete drainage pattern can be seen. However, figure 7 evidence suggests southeast-oriented flood waters crossed what is today an isolated mountain area standing almost 1000 meters higher than the surrounding region (and even higher than valley areas). How could flood waters reach such an elevation? 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.

Drainage divides in Little Rockies Mountain area

Figure 8: Drainage divides in Little Rockies Mountain area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 8 illustrates the entire Little Rocky Mountain upland region and is located west of the figure 7 map area and includes significant overlap areas with figure 7. Perhaps the most remarkable landscape feature from the viewpoint of this essay are through valleys linking drainage systems on opposites sides of the Little Rocky Mountain upland region. The Beaver Creek-Bear Gulch through valley was illustrated and discussed in figure 7 above. Note how Beaver Creek headwaters are linked in the figure 8 center area to northwest-oriented headwaters of north-northeast oriented Lodge Pole Creek which flows to the figure 8 north edge. Also note the higher level through valley between Beaver Mountain and Green Mountain linking north-oriented White Horse Canyon with the east-oriented Beaver Creek valley. Then note the through valley between Antoine Butte and Shell Butte linking the northwest-oriented headwaters of north-northeast oriented Lodge Pole Creek with headwaters of southeast-oriented Ruby Gulch, which flows to Zortman and to southeast-oriented Camp Creek. Proceeding to the west side of the Little Rockies note the through valleys on both sides of Mission Butte linking headwaters of northwest-oriented Peoples Creek with headwaters of south-oriented Rock Creek (which flows south from the Landusky and Campground areas) and southwest-oriented Bull Creek (which flows southwest to the figure 8 southwest corner). Although all of these through valleys probably are related to underlying geologic structures the through valleys were eroded by water moving from north and northwest of the present day Little Rocky Mountain region to the south and southeast. The multiple through valleys suggest the presence of multiple flow channels such as might be found in anastomosing channel complex. As previously mentioned there are multiple explanations as to how southeast-oriented flood waters were able to cross what is today an isolated uplifted mountain mass. One possibility is the mountain mass was buried in sediments and perhaps ice that flood water removed. Another possibility is the mountain mass was rising as flood waters eroded it and the surrounding region. A third possibility is some combination of the first two possibilities.

Bull Creek-Siparyann Creek drainage divide area

Figure 9: Bull Creek-Siparyann Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 9 illustrates the Bull Creek-Siparyann Creek drainage divide area south and west of the figure 8 map area includes overlap areas with figure 8. Bull Creek flows southwest from its headwaters area near Indian Peak along the Little Rocky Mountain southwest side to the figure 9 west edge (south half). Siparyann Creek originates as Mud Creek in almost the same area as Bull Creek, but flows southeast and southwest around Thornhill Butte before flowing southeast to the figure 9 south edge and then to the southeast-oriented Missouri River, which is located south of figure 9. As shown in figure 8 the Bull Creek headwaters are linked by a well-defined through valley west of Indian Peak with north-oriented headwaters of northwest-oriented Peoples Creek. The through valley and the closeness of the Bull Creek and Mud Creek headwaters area is evidence southeast-oriented flood water once moved across the west end of the Little Rocky Mountains to what was then the actively eroding southeast-oriented Missouri River valley. Flood waters eroded the southeast-oriented erosion surface south of the Little Rocky Mountains. East of Mud Creek are headwaters of south-southeast oriented Rock Creek, which flows to southeast-oriented Cottonwood Creek. Figure 8 evidence also showed how Rock Creek headwaters are linked by through valleys with northwest-oriented headwaters of northwest-oriented Peoples Creek. These multiple southeast-oriented flood flow routes provide evidence of anastomosing flood flow channels being eroded into the Little Rocky Mountain upland. Subsequently headward erosion of the southwest-oriented Bull Creek valley beheaded southeast-oriented flood flow to the Mud Creek-Siparyann Creek drainage basin and shortly thereafter southeast-oriented flood flow across the western Little Rockies was reversed to create the present day northwest-oriented Peoples Creek drainage basin, which drains to the east and southeast-oriented Milk River valley located north of the figure 9 map area.

Bull Creek-Missouri River drainage divide area

Figure 10: Bull Creek-Missouri River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 10 illustrates the Bull Creek-Missouri River drainage divide area south and west of the figure 9 map area and includes overlap areas with figure 9. The deep southeast oriented Missouri River valley is located in the figure 10 southwest quadrant. Southeast and south oriented Cow Creek flows from the figure 10 northwest corner to join the Missouri River near the figure 10 west center edge. Southwest-oriented Bull Creek flows from the figure 10 north center area to join the southeast oriented Missouri River as a barbed tributary also near the figure 10 west center edge. Southeast and south oriented Missouri River tributaries are located southeast of the deep Bull Creek valley. Figure 10 evidence suggests headward erosion of the deep southwest-oriented Bull Creek valley beheaded southeast and south oriented flood flow to what was then probably the actively eroding Missouri River valley. Figure 10 evidence can be explained in the context of southeast oriented flood flow moving across the figure 10 map area on a topographic surface at least as high as the highest figure 10 elevations today. As seen in figures 8 and 9 above the southeast and south oriented flood waters were being channeled by through valleys eroded across the Little Rockies upland mass or were being diverted around the Little Rockies west side. Headward erosion of the southeast and south oriented Cow Creek valley probably was along southeast and south oriented flood flow routes moving around the Little Rockies west side. However, no deep valleys were eroded into the figure 10 map area until the southeast-oriented Missouri River valley eroded headward into the region. Southeast and south oriented tributary valleys eroded headward into the newly eroded Missouri River valley north wall. As Missouri River valley headward erosion progressed to the figure 10 west edge area it captured significant flood flow that had moved around the Little Rockies west side. The deep Cow Creek valley eroded north and northwest and the deep Bull Creek valley erode northeast to capture these south- and southeast-oriented flood waters. As the Bull Creek valley eroded headward it beheaded multiple flood flow routes to what were then actively eroding south- and southeast-oriented Missouri River tributary valleys. Headward erosion of the Bull Creek valley ceased when southeast-oriented flood waters moving to the Little Rockies region were beheaded by headward erosion of the Milk River valley and flood waters on the northwest ends of beheaded flood flow routes reversed flow direction to create the northwest-oriented Peoples Creek drainage basin and the Milk River-Missouri River drainage divide.

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.