A geomorphic history based on topographic map evidence

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

Introduction:

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

Armells Creek-Box Elder Creek drainage divide area location map

Figure 1: Armells Creek-Box Elder 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 an Armells Creek-Box Elder Creek drainage divide area location map and illustrates a region in Montana. The Missouri River flows northeast in the figure 1 northwest corner to Fort Benton and Loma and then turns southeast, east-northeast and southeast to flow to Fort Peck Lake. The Musselshell River flows from the Little Belt Mountains area (figure 1 west center) to Martinsdale, Harlowton, Ryegate, Lavina, Roundup, and Melstone and then turns north to flow to Mosby and to join the Missouri River at Fort Peck Lake. The Yellowstone River flows from Big Timber (along the figure 1 south edge) to Greycliff, Columbus, Laurel, Billings, Custer, Forsyth, and Rosebud (located near the figure 1 east edge). Armells Creek  begins in the Judith Mountains (located in figure 1 center area) and flows northeast to join the Missouri River. Box Elder Creek begins north of the Judith Mountains near Roy and flows northeast for a short distance before turning southeast to flow to the north-oriented Musselshell River near Mosby as a barbed tributary. Note several unnamed southeast-oriented Box Elder Creek tributaries also originating in the Judith Mountains area. Based on other Missouri River drainage basin landform origins research project essays (published on this website) landform evidence illustrated in this essays 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 deep valleys that eroded headward into a topographic surface at least as high as the figure 1 region highest elevations today. Prior to Musselshell River valley headward erosion (although not much before) the deep Yellowstone River valley eroded southwest to capture southeast-oriented flood waters and to divert flood waters northeast. The Musselshell River valley was the next valley that eroded south and southwest to capture southeast-oriented flood water and divert flood flow northeast. The northeast-oriented North Willow Creek valley then eroded southwest to behead and capture southeast-oriented flood waters moving to the newly eroded northeast-oriented Musselshell River valley. The southeast-oriented North Willow Creek valley segment eroded headward along a captured southeast-oriented flood flow route and the Willow Creek valley eroded headward along another southeast-oriented flood flow route. Next the Flatwillow Creek valley eroded southwest and northwest to capture southeast-oriented flood flow that had been moving to what was then the newly eroded North Willow Creek valley. Headward erosion of Box Elder Creek tributary valleys then progressively captured the flood flow, which as detailed maps below illustrate crossed the Judith Mountain region. Headward erosion of the northeast-oriented Armells Creek valley then beheaded southeast-oriented flood flow routes to Box Elder Creek and Box Elder Creek tributaries and diverted flood waters northeast to the newly eroded Missouri River valley. The Missouri River-Musselshell River drainage divide area essay, McDonald Creek-Flatwillow Creek drainage divide area essay, Flatwillow Creek-North Willow Creek and Willow Creek drainage divide area essay, and North Willow Creek-Musselshell River drainage divide area essay describe drainage divides located near the Armells Creek-Box Elder Creek drainage divide area discussed here and can be found under Musselshell River on the sidebar category list.

Armells Creek-Box Elder Creek drainage divide area detailed location map

Figure 2: Armells Creek-Box Elder 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 Armells Creek-Box Elder Creek drainage divide area discussed here. Fergus and Petroleum Counties are located in Montana. The Missouri River flows in an east-southeast direction in the figure 2 northeast quadrant to join the north-oriented Musselshell River at UL Bend, located in the figure 2 northeast corner. The Musselshell River flows northeast from the figure 2 southeast corner along the county line to join the Missouri River at UL Bend in the figure 2 northeast corner. Armells Creek originates in the Judith Mountains and flows north-northwest and then northeast to join the east-southeast oriented Missouri River near the figure 2 north edge. Box Elder Creek originates in the Judith Mountains near where Armells Creek originates and then flows north and northeast to Fergus and Roy before turning to flow southeast to the figure 2 southeast quadrant, where it joins the north-oriented Musselshell River as a barbed tributary. Note major Box Elder Creek tributaries, most of which also begin in the Judith Mountains area and which have significant southeast-oriented valley segments. These tributaries include Bear Creek, Little Box Elder Creek, Fords Creek, Chippewa Creek, Alkali Creek and North Fork McDonald Creek. Figure 2 shows a number of southeast-oriented streams or segments of streams. This predominance of southeast-oriented drainage is interpreted as evidence the Armells Creek-Box Elder Creek drainage divide area was eroded by an immense southeast-oriented flood which crossed the figure 2 map area. Flood waters originally were moving to what was probably a newly eroded northeast and north-oriented Musselshell River valley.  Evidence in detailed maps below illustrates flood waters originally flowed on a topographic surface at least as high as the highest Judith Mountains elevations today. Flood waters deeply eroded the region surrounding the Judith Mountains and it is possible the Judith Mountains were uplifted as flood waters eroded the figure 2 map region. Headward erosion of what were then deep Box Elder Creek tributary valleys and the Box Elder Creek valley captured the flood waters and diverted flood flow to what was then the newly eroded north-oriented Musselshell River valley. Next headward erosion of the Missouri River-Armells Creek valley captured the flood flow and beheaded flood flow routes to the newly eroded Box Elder Creek and Box Elder Creek tributary valleys. Soon thereafter headward erosion of the Missouri River valley captured all southeast-oriented flood flow that had been moving across the figure 2 map area. Detailed maps below illustrate evidence supporting this interpretation of Armells Creek-Box Elder Creek drainage divide landform origins.

Armells Creek-Box Elder Creek drainage divide area north of Roy, Montana

Figure 3: Armells Creek-Box Elder Creek drainage divide area north of Roy, Montana. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the Armells Creek-Box Elder Creek drainage divide area north of Roy, Montana. Armels Creek flows northeast in the figure 3 northwest corner and continues in a northeast direction to the Missouri River. Dry Armells Creek is the northeast and northwest-oriented stream flowing to the figure 3 north edge east of Armells Creek. Box Elder Creek flows northeast from the figure 3 southwest corner past Fergus and then turns east to flow to Roy. East of Roy Box Elder Creek turns northeast and then southeast to flow to the figure 3 southeast corner. From the figure 3 southeast corner Box Elder Creek flows southeast to eventually join the north-oriented Musselshell River as a barbed tributary. Northeast-oriented Fargo Coulee in the figure 3 north half is an Armells Creek tributary and north of figure 3 turns to drain north to Armells Creek. The figure 3 map area drainage history began with an immense southeast-oriented flood moving across the figure 3 map area on a topographic surface higher than any figure 3 elevations today. A deep southeast-oriented Box Elder Creek valley eroded into the figure 3 map area and then proceeded to erode southwest and west to capture the southeast-oriented flood waters. Headward erosion of a deep northeast-oriented Armells Creek valley and its tributary valleys next began to capture the southeast-oriented flood flow. First a deep Fargo Coulee valley eroded south and southwest from the actively eroding Armells Creek valley head. Next headward of the Armells Creek valley head beheaded a major southeast-oriented flood flow route along the present day northwest-oriented Dry Armells Creek valley segment. Flood waters on the northwest end of the newly beheaded southeast-oriented flood flow route reversed flow direction to flow northwest to the newly eroded northeast-oriented Armells Creek valley. Also, a northeast-oriented tributary valley was eroded southwest from the newly reversed flood flow route to capture yet to beheaded southeast-oriented flood flow. Southeast-oriented flood flow to that northeast-oriented Dry Armells Creek valley segment was then beheaded by headward erosion of the northeast-oriented Armells Creek valley. Figures below provide a bigger picture view of where flood waters were going and why northeast-oriented valleys eroded headward across this region.

Armells Creek-Box Elder Creek drainage divide area west of Roy, Montana

Figure 4: Armells Creek-Box Elder Creek drainage divide area west of Roy, Montana. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates the Armells Creek-Box Elder Creek drainage divide area west and south of the figure 3 map area and includes overlap areas with figure 3. Armells Creek flows north and northeast from the figure 4 southwest corner area to Armells and then flows northwest, southeast, north, and northeast to the figure 4 north edge. The East Fork Armells Creek flows north-northeast (just west of Mitchell Canyon near the figure 3 south edge) and then turns to flow northwest to join Armells Creek where it turns from flowing southeast to flowing north (located north of Armells). The West Fork of Box Elder Creek flows north in Mitchell Canyon and north-oriented East Fork is located just east of it.  Box Elder Creek after flowing north turns northeast and east to flow to Roy as seen in figure 3. East-oriented Bear Creek in the figure 4 southeast quadrant is a Box Elder Creek tributary. This figure 4 map area is north of the Judith Mountains (see figure 5 below) and like the figure 3 map area was eroded by an immense southeast oriented flood first captured by headward erosion of the Box Elder Creek valley and its tributary valleys and captured second by headward erosion of the Armells Creek valley and its tributaries. The deep southeast oriented Box Elder Creek eroded headward east of the Judith Mountains and the west and southwest around the Judith Mountains because the Judith Mountains rock types prevented deep erosion. The north oriented Box Elder Creek valley segments were eroded by reversals of flood flow on beheaded south and southeast oriented flood flow routes. Subsequently the Armells Creek valley eroded southwest from what was at that time the newly eroded Missouri River valley and beheaded southeast-oriented flood flow routes to the newly eroded Box Elder Creek valley. Northwest-oriented and north-oriented Armells Creek valley (and Armells Creek tributary valley) segments were eroded by reversals of flood flow on northwest and north ends of beheaded southeast- and south-oriented flood flow routes. This interpretation of figure 4 evidence by realizing the immensity of the flood involved and the deep erosion flood waters accomplished. Further, as flood waters eroded the region the Judith Mountains may have been uplifted. How could a flood be large enough to uncover a mountain range and/or a mountain range be raised while flood waters were eroding it? While the source of the southeast-oriented flood waters described in this essay cannot be determined from evidence presented in this essay 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 flood waters further and further northeast and north into space in the deep “hole” the rapidly melting thick ice sheet had once occupied. In addition, such a flood water source may explain uplift of mountains regions, such as the Judith Mountains, during an immense southeast-oriented flood. A thick North American ice sheet in deep “hole” created in part due to the ice sheet’s weight would probably create crustal warping elsewhere on the continent, especially along ice sheet margins. Rapid deep erosion of overlying material might also trigger localized uplift.

Armells Creek-Box Elder Creek drainage divide area in eastern Judith Mountains

Figure 5: Armells Creek-Box Elder Creek drainage divide area in eastern Judith Mountains. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the region immediately south of the figure 4 map area, includes overlap areas with figure 4, and also includes evidence southeast-oriented flood waters crossed the Judith Mountains. The Judith Mountains are the dominant figure 5 topographic feature. The north-oriented East and West Forks Box Elder Creek in and near Mitchell Canyon are located in the figure 5 north center area. East-oriented Bear Creek is located along the figure 5 north edge in the figure 5 northeast corner area. North-oriented Armells Creek is located in the figure 5 northwest corner area and originates near Judith Peak, which is located in the figure 5 west center area. All southeast-oriented drainage routes on the south side of the Judith Mountains east of Fords Creek are tributaries to southeast-oriented Little Box Elder Creek, which is a tributary to Fords Creek. Southeast-oriented Fords Creek is a tributary to southeast-oriented Box Elder Creek, which flows southeast to join the north-oriented Musselshell River as a barbed tributary. Figure 5 evidence convinced me flood waters flowed across the Judith Mountains. To understand this evidence start with the southeast-oriented Brickyard Creek and north-oriented East Fork Box Elder Creek drainage divide at Ross Pass (illustrated in detail in figure 6 below) and the north-oriented Armells Creek drainage divide with southeast-oriented Fords Creek tributaries near Judith Peak (illustrated in detail in figure 7 below).  Armells Creek flows north and northeast to the deep east-oriented Missouri River valley. Box Elder Creek, after originating near where the East Fork Armells Creek originates and flowing parallel to the East Fork Armells Creek, makes a turn to flow northeast, east, and southeast as seen in figures 3 and 4. Box Elder Creek then continues to flow southeast as seen in figure 1, 2, and 10 and eventually joins the north-oriented Musselshell River as a barbed tributary. The Musselshell River then flows north to join the east-oriented Missouri River. Further all figure 5 southeast-oriented drainage routes on the Judith Mountains south side are Box Elder Creek tributaries. The question is how did running water create such a drainage pattern? The answer is a large southeast-oriented flood flowed across the Judith Mountains. Because flood water does not flow uphill the flood waters must have initially flowed on a topographic surface at least as high as the tops of the Judith Mountains today. Then as flood waters continued to flow across the region the Judith Mountains gradually emerged. Emergence of the Judith Mountains could have happened in one of two ways, or in a combination of the two ways. First, the Judith Mountains could have been buried in easily eroded sedimentary rocks and/or ice and the Judith Mountains emerged as flood waters removed the surrounding materials. The second way would be if the Judith Mountains were uplifted as flood waters deeply eroded the region. Probably some combination of the two ways is what happened.

Box Elder Creek- Little Box Elder Creek drainage divide area at Ross Pass

Figure 6: Box Elder Creek- Little Box Elder Creek drainage divide area at Ross Pass. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates a detailed map of the East Fork Box Elder Creek-Brickyard Creek (Little Box Elder Creek) drainage divide area seen in less detail in figure 5 above. Ross Pass in located in the figure 6 center. The East Fork Box Elder Creek flows north from Ross Pass to the figure 6 north center edge. Brickyard Creek flows south and southeast from Ross Pass to the figure 6 south center edge. Ross Pass is a water eroded through valley and provides evidence south oriented water once flowed across the Judith Mountains. West of Ross Pass is Lewis Peak and west of Lewis Peak is a much higher level through valley linking north-oriented Mitchell Canyon (West Fork Box Elder Creek) with an unnamed south-oriented Fords Creek tributary. That higher level through valley is also evidence south-oriented water once flowed across the Judith Mountains. Many additional such through valleys can be located in the Judith Mountains region (see figures 5 and 7) and provide evidence multiple channels of south-oriented water, such as might be found in an anastomosing channel complex, moved large volumes of flood waters across the Judith Mountains. Flood waters flowing in the Ross Pass channel were more successful in eroding a deep valley than flood waters flowing in the present day high level through valley west of Lewis Peak, although I suspect flood waters were flowing in both channels right up until the time the flood flow routes were beheaded and reversed. Headward erosion of the deep southeast-oriented Box Elder Creek valley east of the Judith Mountains enabled a deep east-oriented Box Elder Creek valley seen in figures 3 and 4 to erode west and behead south-oriented flood flow moving in the Ross Pass valley. Flood waters on the north end of the beheaded south-oriented flood flow route reversed flow direction to flow north and erode the north-oriented East Fork Box Elder Creek valley. Headward erosion of the deep east-oriented Box Elder Creek valley beheaded south-oriented flood flow channels one channel at a time. Because the channels were interconnected reversed flow on the north end of the Ross Pass through valley channel captured yet to be beheaded south-oriented flood flow from the Mitchell Canyon flood flow route. That captured flood water made a U-turn around the south side of Lewis Peak and helped erode the north-oriented East Fork Box Elder Creek valley. The process was repeated as additional flood flow routes were beheaded.

Armells Creek- Fords Creek drainage divide area near Judith Peak

Figure 7: Armells Creek- Fords Creek drainage divide area near Judith Peak. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates a detailed map of the Armells Creek-Fords Creek drainage divide area west of the figure 6 map area and seen in less detail in figure 5 above. Red Mountain is located in the figure 7 center area. Judith Peak is located in the figure 7 west center area. Armells Creek originates in the valley immediately west of Red Mountain and flows northwest to the figure 7 north edge. South of the Armells Creek headwaters is a high level mountain pass (or through valley) between Red Mountain and Judith Peak and on the south side of that through valley is south-oriented Collar Gulch, which flows to Fords Creek, which in turn flows to Box Elder Creek. Southeast-oriented Chicago Gulch begins on the Red Mountain southeast side and becomes southeast-oriented Fords Creek before reaching the figure 7 southeast corner. Linked to Chicago Gulch by a well-defined through valley between Red Mountain and Maginnis Mountain is the north-oriented East Fork of Armells Creek, located in the figure 7 northeast quadrant. The East Fork Armells Creek-Chicago Gulch through valley and the higher level Armells Creek-Collar Gulch through valley, along with similar through valleys, provide evidence of multiple flood flow channels that once crossed the Judith Mountains. As previously described flood waters must have originally flowed on a topographic surface at least as high as the high as the highest Judith Mountains elevations today. And as previously mentioned that could only have happened 1.)  if the Judith Mountains were buried in easily eroded sediment and/or ice, which flood waters subsequently removed, 2,) if the Judith Mountains were uplifted as flood waters eroded the region, or 3.) if some combination of the first two possibilities occurred. Uplift of the Judith Mountains during an immense southeast-oriented flood may not be unreasonable if the flood water source was rapid melting of a thick North American ice sheet that had eroded and otherwise created a deep “hole” in the North American continent. Ice sheet weight may have played a significant role in creating the deep “hole” and may have triggered crustal warping elsewhere on the continent. Localized crustal warping, such as the Judith Mountains uplift, may have been triggered as flood waters rapidly and deeply eroded some regions and deposited the eroded materials in other locations.

Little Box Elder Creek drainage basin southeast of Judith Mountains

Figure 8: Little Box Elder Creek drainage basin southeast of Judith Mountains. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates the region southeast of the Judith Mountains, is south and east of the figure 5 map area, and includes overlap areas with figure 5. All streams in figure 8 are Box Elder Creek tributaries. Starting from the south Alkali Creek and Chippewa Creek are McDonald Creek tributaries and McDonald Creek flows to Box Elder Creek (see figures 1, 2, and 10). North of Chippewa Creek is Fords Creek, the origin of which was seen in figure 7 above. Continuing northeast from Fords Creek is Little Box Elder Creek, which is formed where Edwards Creek and Brickyard Creek join. The origin of Brickyard Creek at Ross Pass was seen in figure 6. Southeast-oriented Box Elder Creek is located northeast of the figure 8 map area, and has approximately the same southeast orientation as the figure 8 drainage routes. This figure 8 drainage pattern evolved as deep southeast-oriented valleys eroded headward along southeast-oriented flood flow routes moving large quantities of flood waters across the Judith Mountains. As seen in figures 6 and 7 flood waters eroded deep narrow valleys into the Judith Mountains. These confined valleys focused flood flow into well-defined channels, which provided sustained flood flow along specific southeast-oriented flood flow routes. Long deep southeast-oriented valleys headward along those flood flow routes to the Judith Mountains southeast flank. The deep parallel Box Elder Creek valley had the advantage of not having to erode through the resistant Judith Mountains bedrock material and was able to erode northwest and west around the Judith Mountains north flank. North of the Judith Mountains the deep Box Elder Creek valley beheaded and reversed southeast-oriented flood flow routes to southeast-oriented Little Box Elder Creek and Fords Creek valleys. Headward erosion of the deep northeast-oriented Armells Creek valley occurred at approximately the same time and captured southeast-oriented flood flow moving to the newly eroded Box Elder Creek valley and also beheaded and reversed southeast-oriented flood flow routes moving flood waters to Chippewa Creek.

Little Box Elder Creek-McDonald Creek drainage divide north of Grassrange

Figure 9: Little Box Elder Creek-McDonald Creek drainage divide north of Grassrange. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Little Box Elder Creek-McDonald Creek drainage divide area north of Grassrange, Montana, is located east of the figure 8 map area, and includes overlap areas with figure 8 above. Little Box Elder Creek is located in the figure 9 northwest quadrant and flows east-southeast to join east-oriented Fords Creek and then flows northeast and southeast to the figure 9 east edge. Note southeast-oriented Fords Creek tributaries (and also to other major east-oriented valleys). The southeast-oriented tributaries provide evidence the deep Fords Creek valley (and the other east-oriented valleys) eroded headward across southeast-oriented flood flow. They also provide evidence the major east-oriented valleys were eroded in sequence from south to north. Grassrange is located south of the highway intersection in the figure 9 south center area. That highway intersection is located near the point where the north-oriented South Fork McDonald Creek and the east-oriented North Fork McDonald Creek meet and form northeast and east-southeast oriented McDonald Creek. McDonald Creek is a Box Elder Creek tributary. The deep McDonald Creek valley and tributary valleys eroded west and west-northwest from the newly eroded southeast-oriented Box Elder Creek valley along flood flow routes moving between what are today the Judith Mountains in the north and the Big and Little Snowy Mountains in the south (see figures 1 and 2 and also see McDonald Creek-Flatwillow Creek drainage divide essay). Figures in this essay have been following the Little Box Elder Creek and Fords Creek valleys downstream from through valleys linking them with north-oriented valleys. The major figure 9 east and east-southeast oriented valleys were eroded headward along flood flow routes being channeled by narrow valleys that had been eroded by flood waters into the Judith Mountains resistant rock mass.

Box Elder Creek-McDonald Creek drainage divide north of Winnett

Figure 10: Box Elder Creek-McDonald Creek drainage divide north of Winnett. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 illustrates the Box Elder Creek-McDonald Creek drainage divide area east of the figure 9 map area and does not include overlap areas with figure 9. Box Elder Creek flows southeast from the figure 10 north center area to the figure 10 east edge (south half). McDonald Creek flows east-southeast and east in the figure 10 south edge area and joins Box Elder Creek east of the figure 10 map area. Fords Creek joins Box Elder Creek north of the figure 10 map area. East-oriented Buffalo Creek flows south of the lake in the figure 10 northwest corner area and joins southeast-oriented Box Elder Creek. The lake in the figure 10 northwest corner area is War Horse Lake and is located in a west-northwest to east-southeast oriented through valley linking the east-oriented Buffalo Creek valley with the east-oriented Fords Creek valley. The through valley was a flood eroded feature. The lake is at least in part created by a levee on the northwest side (not visible in figure 10). Abandonment of the through valley probably occurred as flood waters were still moving across the figure 10 map area in ever-changing  anastomosing channels. East-oriented valleys probably were initially eroded headward from the deep north-oriented Musselshell River valley as it eroded south to capture southeast-oriented flood waters. Headward erosion of the deep southeast-oriented Box Elder Creek valley then eroded northwest to capture east-oriented flood flow moving in the ever-changing anastomosing channel complex to the newly eroded north-oriented Musselshell River valley. The deep east-oriented McDonald Creek valley probably was eroded by flood waters captured from west of the Judith Mountains area (McDonald Creek headwaters are located south of the Judith Mountains). Southeast-oriented McDonald Creek tributaries provide evidence of southeast-oriented flood flow at the time the deep McDonald Creek valley was eroded. Drainage patterns illustrated in this Armels Creek-Box Elder Creek drainage divide essay are fascinating and like drainage patterns illustrated and described in many of other Missouri River drainage basin landform origins research project essays (published on this website) are worthy of further study.

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.