A geomorphic history based on topographic map evidence

The Missouri River-Big Dry Creek and Musselshell River-Big Dry Creek drainage divide area discussed here is located in Montana, USA. Although detailed topographic maps of the Missouri River-Big Dry Creek and Musselshell River-Big Dry 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 Missouri River-Big Dry Creek and Musselshell River-Big Dry 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 and Musselshell River valleys captured all southeast-oriented flood flow.

Introduction:

• The purpose of this essay is to use topographic map interpretation methods to explore Montana Missouri River-Big Dry Creek and Musselshell River-Big Dry Creek drainage divide area landform origins. Map interpretation methods can be used to unravel many geomorphic events leading up to formation of present-day drainage routes and development of other landform features. While each detailed topographic map feature provides detailed evidence to be explained, the solution must be consistent with explanations for adjacent area map evidence as well as solutions to big picture map evidence puzzles. I invite readers to improve upon my solutions or to propose alternate solutions that better explain evidence and are also consistent with adjacent map area and big picture evidence. Readers may do so either by making comments here or by writing and publishing their own essays and then by leaving a link to those essays in a comment here.

• This essay is also exploring a paradigm in which erosional landforms are interpreted as evidence left by immense glacial melt water floods. Implied in that interpretation is the immense floods were derived from a thick North American ice sheet that created a deep “hole” in the North American continent and also melted fast. The previously unexplored paradigm being tested in this and similar essays is a thick North American ice sheet, comparable in thickness to the present day Antarctic ice sheet, occupied approximately the North American region usually recognized to have been glaciated and through its weight and erosive actions created a “deep” North American “hole”, through its weight and deep erosion (and perhaps deposition) along major south-oriented melt water flow routes caused significant crustal warping and tectonic change, through its action of melting fast produced immense floods that flowed across the continent, and through its action of melting fast systematically opened up space in the ice sheet created “hole” so headward erosion of newly developed north-oriented drainage systems captured immense south-oriented melt water floods and diverted immense melt water floods north into space the ice sheet had once occupied.

• If this previously unexplored paradigm is correct the geographic region explored by this essay should contain evidence of immense floods that were captured by headward erosion of new valley systems so as to cause the floods to flow in a different direction. Ability of this previously unexplored paradigm to explain Missouri River-Big Dry Creek and Musselshell River-Big Dry Creek drainage divide area landform evidence in Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Missouri River-Big Dry Creek and Musselshell River-Big Dry Creek drainage divide area location map

Figure 1: Missouri River-Big Dry Creek and Musselshell River-Big Dry 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 Missouri River-Big Dry Creek and Musselshell River-Big Dry Creek drainage divide area location map and illustrates a region in Montana. The Missouri River flows east-southeast from the figure 1 west edge to Fort Peck Lake and then northeast and east to Wolf Point, Poplar, and Brockton before flowing to the figure 1 east edge. The Yellowstone River flows northeast from the figure 1 map south edge (center east) to Custer, Miles City and Glendive (located on the figure 1 east edge). The Musselshell River flows northeast from Ryegate in the figure 1 southwest corner to Lavina, Roundup, and Melstone and then turns north to Mosby and then flows to join the Missouri River at Fort Peck Lake. Big Dry Creek originates east of Mosby and flows northeast to Jordan, Montana and after joining north-oriented Little Dry Creek flows north to join the Missouri River at Fort Peck Lake. 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 and the north-oriented Big Dry Creek and Musselshell River valleys eroded south and southwest to capture southeast-oriented flood water and to divert the flood flow to the northeast. First, the East-oriented Missouri River valley eroded west to the Fort Peck Dam location and the deep Big Dry Creek valley head eroded south and southwest to capture southeast-oriented flood waters and to divert flood waters to the north and northeast. As the Big Dry Creek valley eroded south to capture the southeast-oriented flood flow the Missouri River valley eroded west and southwest to also capture the flood flow and beheaded flood flow routes to the newly eroded Big Dry Creek valley. Subsequently the Musselshell River valley eroded south to also behead southeast-oriented flood flow routes to the newly eroded Big Dry Creek valley. The Big Dry Creek-Prairie Elk Creek drainage divide area essay, the Prairie Elk Creek-Redwater River drainage divide area essay, which are located east or southeast of the drainage divide area discussed here and in the Big Dry Creek-Yellowstone River drainage divide area essay describe drainage divide areas near the Missouri River-Big Dry Creek and Musselshell River-Big Dry Creek drainage divide area discussed and illustrated here and can be found under Big Dry Creek or Redwater River on the sidebar category list.

Missouri River-Big Dry Creek and Musselshell River-Big Dry Creek drainage divide area detailed location map

Figure 2: Missouri River-Big Dry Creek and Musselshell River-Big Dry 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 Missouri River-Big Dry Creek and Musselshell River-Big Dry Creek drainage divide areas discussed here. Garfield County is located in Montana. The Missouri River flows southeast and northeast to Fort Peck Lake in the figure 2 north half. Fort Peck Lake is a large reservoir impounded behind Fort Peck Dam (located north of figure 2). The Musselshell River enters the figure 2 southwest corner area, serves as a county line, and flows north to join the Missouri River in the figure 2 west center area. Big Dry Creek originates south of Sand Springs in the figure 2 southwest quadrant and flows northeast through Jordan, Montana to join north-oriented Little Dry Creek near the Garfield-Mc Cone County line. Big Dry Creek, after joining Little Dry Creek, flows north to join the Missouri River at Fort Peck Lake and the north-south arm of Fort Peck Lake is the flooded Big Dry Creek valley. This essay first illustrates evidence at the northeast end of Missouri River-Big Dry Creek drainage divide area located west of Big Dry Creek Bay and southeast of the flooded Missouri River valley. Next the essay looks at evidence in the Snow Creek-Hell Creek drainage divide area and Hell Creek-Big Dry Creek drainage divide area before looking at evidence in the South Fork Snow Creek-Big Dry Creek drainage divide area. Next evidence in the northeast-oriented Missouri River-Big Dry Creek drainage divide area is observed and the essay concludes by looking at evidence in the Musselshell River-Big Dry Creek drainage divide area. Figure 2 shows numerous southeast and northwest-oriented Missouri River tributaries and numerous southeast-oriented Big Dry Creek tributaries. This southeast and northwest drainage alignment is evidence the Big Dry Creek and Missouri River valleys eroded headward to capture southeast-oriented flood flow. The southeast-oriented tributary valleys were eroded by southeast-oriented flood flow moving into the newly eroded valleys and the northwest-oriented tributary valleys were eroded by reversals of flood flow on the northwest ends of beheaded southeast-oriented flood flow routes. Because flood waters move in and erode anastomosing (or inter-connected) channels reversed flood flow on a beheaded flood flow route could capture flood flow from yet to be beheaded flood flow routes. Such captures of yet to be beheaded flood flow could enable reversed flood flow routes to erode much deeper and larger northwest-oriented valleys than might otherwise be possible. Often evidence for such flow reversals and captures can be found on detailed topographic maps such as those illustrated below.

Northeast end of Missouri River-Big Dry Creek drainage divide area

Figure 3: Northeast end of Missouri River-Big Dry Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 3 illustrates the northeast end of the Missouri River-Big Dry Creek drainage divide area. The flooded northeast-oriented Missouri River valley is located in the figure 3 northwest corner area. The flooded northwest-oriented Big Dry Creek valley is located in the figure 3 east half. The present day north oriented peninsula between the flooded Missouri River valley and the flooded Big Dry Creek valley is the northeast end of the Missouri River-Big Dry Creek drainage divide. Note how almost all Missouri River tributaries are northwest oriented and almost all Big Dry Creek tributaries are southeast-oriented or have southeast-oriented valley segments. Through valleys link heads of southeast-oriented Big Dry Creek tributary valleys with heads of northwest-oriented Missouri River tributary valley heads. These through valleys are hard to identify on figure 3 and figure 4 below illustrates a detailed map of through valley slinking the northwest-oriented Sage Creek valley with the southeast-oriented Box Creek valley. The northwest-southeast drainage alignment and the through valleys provide evidence multiple channels of southeast-oriented flood flow once moved across the present day Missouri River-Big Dry Creek drainage divide to what was then the newly eroded north and northwest-oriented Big Dry Creek valley. The multiple channels suggest flood waters were eroding an ever-changing southeast-oriented anastomosing channel complex. Further, the evidence suggests the flood waters were coming from a source northwest of the present day northeast-oriented Missouri River valley, which means at the time the southeast-oriented Big Dry Creek tributary valleys were eroded the deep northeast-oriented Missouri River valley did not exist. Headward erosion of the deep northeast-oriented Missouri River valley  beheaded the southeast-oriented flood flow routes to what were then the actively eroding southeast-oriented Big Dry Creek tributary valleys. Flood waters on the northwest ends of the beheaded southeast-oriented flood flow routes reversed their flow direction and began to flow northwest into the newly eroded northeast-oriented Missouri River valley. Because flood waters were flowing in anastomosing channels and also because southeast-oriented flood flow channels were beheaded one channel at a time (by headward erosion of the deep northeast-oriented Missouri River valley) reversed flood flow on newly beheaded flood flow routes could capture yet to be beheaded flood flow from flood flow routes further to the southwest. These captures of yet to be beheaded flood flow helped erode the northwest-oriented Missouri River tributary valleys.

Sage Creek-Box Creek drainage divide area

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

Figure 4 illustrates the Sage Creek-Box Creek drainage divide area seen in less detail in figure 3 above. Sage Creek flows northwest to Sage Creek Bay located in the figure 4 northwest corner. Box Creek flows southeast to the figure 3 southeast corner. Note the northwest-southeast oriented through valley linking the northwest-oriented Sage Creek headwaters with the southeast-oriented Box Creek headwaters. The North Fork Box Creek flows southeast from the figure 4 center area to join southeast-oriented Box Creek near the figure 4 southeast corner. Note how southeast-oriented North Fork Box Creek is linked by a northwest-southeast oriented through valley with northwest-oriented Spring Draw located in the figure 4 north center area. Similar through valleys are located all along the present day Missouri River-Big Dry Creek drainage divide. The through valleys provide evidence that multiple channels of southeast-oriented flood flow moved across the present day drainage divide. At the time flood flow waters crossed the drainage divide the deep northeast-oriented Missouri River valley did not exist. Headward erosion of the deep northeast-oriented Missouri River valley beheaded and reversed the southeast-oriented flood flow. Flood waters on the northwest ends of the beheaded southeast-oriented flood flow channels reversed flow direction to flow northwest into the newly eroded northeast-oriented Missouri River valley. The source of the flood waters cannot be determined from evidence presented here. However, the hundreds of Missouri River drainage basin landform origins research project essay 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” located approximately in 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.

Crooked Creek-Pass Creek drainage divide area

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

Figure 5 illustrates another detailed map of through valleys linking northwest-oriented Crooked Creek with southeast-oriented Pass Creek. Crooked Creek flows northwest to Crooked Creek Bay, which is the unlabeled bay east of Hell Creek Bay in figure 2. Pass Creek is not shown on figure 2, but flows southeast to join southeast-oriented Woody Creek, which flows to Big Dry Creek. Pass Creek flows southeast to the figure 5 southeast corner. Headwaters of southeast-oriented South Fork Pass Creek are located west of Pass Creek along the figure 5 south edge. Crooked Creek flows north in the figure 5 center area and then northwest to the figure 5 northwest corner area. Note multiple northwest-southeast oriented through valleys linking the northwest-oriented Crooked Creek drainage system with the southeast-oriented Pass Creek drainage system. These through valleys provide evidence flood waters once flowed in a southeast-oriented anastomosing channel complex that crossed the present day drainage divide. Flood waters moved southeast and were eroding southeast-oriented tributary valleys headward from what was then the newly eroded north-oriented Big Dry Creek valley. At the time flood waters crossed the drainage divide the deep northeast-oriented Missouri River valley did not exists and flood waters came from a source northwest of the present day Missouri River valley. Headward erosion of the deep northeast-oriented Missouri River valley then beheaded and reversed southeast-oriented flood flow channels in sequence from the northeast to the southwest. Flood waters on northwest ends of beheaded flood flow routes reversed flow direction to flow northwest into the newly eroded and deeper northeast-oriented Missouri River valley. Because flood waters were flowing in anastomosing (or interconnected) channels reversed flood flow on a newly beheaded flood flow route could capture yet to be beheaded flood flow from flood flow routes further to the southwest. Such captures of yet to be beheaded flood flow helped erode northwest-oriented Missouri River tributary valleys, such as the Crooked Creek valley, and also helped create the present day Missouri River-Big Dry Creek drainage divide.

Snow Creek-Hell Creek drainage divide area

Figure 6: Snow Creek-Hell Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 6 illustrates the Snow Creek-Hell Creek drainage divide area west of the  figure 5 map area and there is no overlap with previous figures. Hell Creek Bay is located in the figure 6 northeast corner area and Hell Creek flows north and northeast from the figure 6 south edge across the figure 6 south center area to Hell Creek Bay. The unlabeled bay west of Hell Creek Bay is Snow Creek Bay and Snow Creek flows northeast from the figure 6 west edge to Snow Creek Bay. The present day peninsula separating Snow Creek Bay from Hell Creek Bay is drained by northwest-oriented Snow Creek tributaries and by southeast-oriented Hell Creek tributaries. The drainage alignment seen here is again evidence that southeast-oriented flood flow once moved across the present day Snow Creek-Hell Creek drainage divide. Briefly the figure 6 evidence suggests southeast-oriented flood waters once flowed across the entire figure 7 map area before the existence of the northeast and east-oriented Hell Creek, Snow Creek, and Missouri River valleys. Headward erosion of the deep northeast-oriented Hell Creek valley (probably from what was then the actively eroding deep Missouri River valley head) first captured the southeast-oriented flood flow that was moving to what was then the newly eroded northeast-oriented Big Dry Creek valley (located southeast of the figure 6 map area-see figure 7 below). As the deep Missouri River valley eroded west the deep northeast-oriented Snow Creek valley eroded southwest to capture southeast-oriented flood flow routes to the newly eroded northeast-oriented Hell Creek valley. Flood waters on the northwest ends of beheaded flood flow reversed flow direction to flow northwest into the newly eroded Snow Creek valley. Subsequently the deep east-oriented Missouri River valley eroded headward to capture southeast-oriented flood flow to the newly eroded Snow Creek valley.

Hell Creek-Big Dry Creek drainage divide area

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

Figure 7 illustrates the Hell Creek-Big Dry Creek drainage divide area south and slightly west of the figure 6 map area and includes overlap with figure 6. Hell Creek flows northwest from the Biscuit Butte area in the northeast quarter of the figure 7 southwest quadrant and then turns to flow northeast across the figure 7 north center area to the figure 7 north edge (east half). Northwest-oriented Hell Hollow in the figure 7 northwest corner area drains to northeast oriented South Fork Snow Creek. Southeast-oriented drainage flowing to the figure 7 south edge flows to northeast oriented Big Dry Creek. Major figure 7 southeast-oriented Big Dry Creek tributaries include White Horse Creek, Bear Creek, Frazier Creek, and Vail Creek. Headward erosion of the northeast oriented Hell Creek valley beheaded southeast-oriented flood flow to the Big Dry Creek valley and reversed flood flow on the northwest ends of beheaded flood flow routes. The best evidence for the flood flow reversals is found in the northwest oriented Hell Creek headwaters valley. Headward erosion of the northeast oriented Hell Creek valley beheaded southeast-oriented flood flow in a northwest-southeast oriented channel on that alignment and reversed flood flow moved northwest to the newly eroded northeast-oriented Hell Creek valley. Drainage divides such as this Hell Creek-Big Dry Creek drainage divide can be used to reconstruct a region’s drainage history. In the case of figure 7 southeast-oriented flood flow first moved across the entire figure 7 map area to what was then the newly eroded northeast-oriented Big Dry Creek valley, which had eroded south and southwest from the newly eroded northeast- and east-oriented Missouri River valley. When headward erosion of the Missouri River valley reached the present day Hell Creek Bay area headward erosion of the northeast-oriented Hell Creek valley began and channel by channel captured the southeast-oriented flood flow routes moving flood waters to the newly eroded Big Dry Creek valley and in the process beheading southeast-oriented Big Dry Creek tributary valleys and creating the Hell Creek-Big Dry Creek drainage divide. As Missouri River valley erosion progressed west the northeast-oriented South Fork Snow Creek-Snow Creek valley eroded southwest and captured southeast-oriented flood flow to the newly eroded Hell Creek valley, and then headward erosion of the deep Missouri River valley captured flood flow moving to Snow Creek.

South Fork Snow Creek-Big Dry Creek drainage divide area

Figure 8: South Fork Snow Creek-Big Dry Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 8 illustrates the South Fork Snow Creek-Big Dry Creek drainage divide area west and south of the figure 7 map area and includes overlap areas with figure 7. Headwaters of northwest-oriented Hell Creek and southeast oriented Frazier Creek are located in the figure 8 east center area. As seen in figure 7 north of figure 8 Hell Creek turns to flow northeast to eventually reach Hell Creek Bay and Frazier Creek flows southeast and eventually reaches northeast-oriented Big Dry Creek. Southeast-oriented Vail Creek flows to the figure 8 southeast corner and west of Vail Creek is southeast oriented Smoky Butte Creek. North of the Smoky Butte Creek and Vail Creek headwaters flowing east and northeast from the Chalk Butte area is a tributary to southeast and northeast oriented South Fork Snow Creek, which can be seen along the figure 8 north edge. Figure 8a below illustrates a detailed map of the Snow Creek-South Fork Snow Creek headwaters area located just north of the figure 8 northwest quadrant. Headward erosion of the South Fork Snow Creek valley and the east and northeast-oriented tributary valley beheaded southeast-oriented flood flow that had been moving flood waters to what were then the actively eroding southeast-oriented Vail Creek and Smoky Butte Creek valleys. The South Fork Snow Creek tributary valley eroded southwest and west first, although headward erosion of the South Fork Snow Creek valley followed soon after, with headward erosion of the Snow Creek next capturing all of the southeast-oriented flood flow. Headwaters of all three valleys do not extend further west, suggesting at the time they beheaded flood flow to the Smoky Butte Creek valley that flood flow was being reduced and beheaded further to the northwest. In other words, headward erosion of the east-oriented Snow Creek valley captured the southeast-oriented flood flow routes, and once the southeast-oriented flood flows were captured all flood flow to what had been the actively eroding the South Fork Snow Creek drainage basin ceased. Note in figure 8a below how headward erosion of the east-oriented Snow Creek valley beheaded southeast-oriented flood flow to the South Fork Snow Creek valley and the South Fork Snow Creek tributary valley located south of the South Fork Snow Creek valley. Shortly after Missouri River valley headward erosion captured all southeast-oriented flood flow to the Snow Creek headwaters area.

Figure 8a: Detailed map of Snow Creek-South Fork Snow Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Squaw Creek-Lodgepole Creek-Big Dry Creek drainage divide area

Figure 9 illustrates the Squaw Creek-Lone Tree Creek drainage divide west of the figure 8 map area and does not include overlap areas with previous figures. Squaw Creek is located in the figure 9 northwest quadrant and flows northwest to the northeast-oriented Missouri River (see figure 2). Indian Creek flows southwest from the figure 9 north edge to join Squaw Creek and Little Squaw Creek is the northwest-oriented Squaw Creek tributary joining Squaw Creek in the figure 9 northwest corner. Seven Blackfoot Creek flows northwest and then east-northeast before turning north in the figure 9 northeast quadrant. North of the figure 9 map area Seven Blackfoot Creek flows northwest to the northeast-oriented Missouri River (see figure 2). Clay Coulee is the southeast, northeast and northwest-oriented Seven Blackfoot Creek tributary located just south of Seven Blackfoot Creek. Lone Tree Creek flows southeast in the figure 9 east center area and is a tributary to northeast-oriented Big Dry Creek. South of Lone Tree Creek the southeast-oriented Steve Fork of Big Dry Creek flows to the figure 9 southeast corner. The southwest and west-oriented North Fork of Lodgepole Creek is located in the figure 9 south center. Lodgepole Creek flows in a northwest direction to the north-oriented Musselshell River (see figures 2 and 10). In many respects figure 9 evidence is similar to evidence in previous figures and illustrates how headward erosion of the deep Missouri River valley north of the figure 9 map area beheaded and reversed southeast-oriented flood flow routes to what was then the newly eroded northeast-oriented Big Dry Creek valley. However, the Squaw Creek-North Fork Lodgepole Creek drainage divide in the figure 9 south center area is asymmetric and suggests flood water moved north from the North Fork Lodgepole Creek valley into the Dry Fork Squaw Creek drainage basin. Figure 9a below illustrates the Dry Fork Squaw Creek-North-Fork Lodgepole Creek drainage divide in detail. This drainage divide was eroded by yet to be beheaded southeast-oriented flood flow moving on flood flow routes west of what was then the actively eroding Missouri River valley head and that had been captured by headward erosion of an east- and northeast-oriented valley that eroded southwest and west on the North Fork Lodgepole Creek alignment. The captured flood water moved east and northeast to join reversed flood flow that eroded the northwest-oriented Squaw Creek valley. Headward erosion of the deep Missouri River valley and the deep Musselshell River valley then beheaded and reversed the captured flood flow route to create the present day Squaw Creek-Lodgepole Creek drainage divide and to erode the southwest and west-oriented North Fork Lodgepole Creek valley.

Figure 9a: Dry Fork Squaw Creek-North Fork Lodgepole Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

South Fork Lodgepole Creek-Big Dry Creek drainage divide area

Figure 10: South Fork Lodgepole Creek-Big Dry Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 10 illustrates the South Fork Lodgepole Creek-Big Dry Creek drainage divide area south and west of the figure 9 map area and there are no overlap areas with previous figures. Big Dry Creek flows northeast from the figure 10 south center area to the figure 10 northeast corner. The northwest oriented South Fork Lodgepole Creek originates near Sand Springs and flows to the figure 10 west edge. Figure 10a below illustrates where the northwest oriented South Fork Lodgepole Creek joins northwest and west oriented Lodgepole Creek and west-oriented North Fork Lodgepole Creek and then flows to the north-oriented Musselshell River (the figure 10a map area is located north and west of the figure 10 map area and there are no overlap areas). Figure 10 evidence when viewed by itself can be explained by headward erosion of the northeast-oriented Big Dry Creek valley to capture 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. Subsequently headward erosion of the deep north-oriented Musselshell River valley beheaded southeast-oriented flood flow routes to the figure 10 map area and flood waters on the northwest ends of beheaded flood flow routes reversed direction to flow northwest to the newly eroded north-oriented Musselshell River valley (which had eroded south from the newly eroded Missouri River valley). Reversed flood flow then eroded the northwest-oriented South Fork Lodge Creek valley and created the Musselshell River-Big Dry Creek drainage divide. While basically correct this history leaves out interesting aspects of the Lodgepole Creek valley history. Figure 10a below illustrates the Lodgepole Creek valley system closer to the Musselshell River. The north-oriented Musselshell River is located along the figure 10a west edge. The northwest-oriented South Fork Lodgepole Creek valley extends from the figure 10a south center to the Musselshell River. The Middle Fork of Lodgepole Creek is northwest-oriented and extends from the figure 10a southeast corner area to join west-oriented North Fork Lodgepole Creek. Apparently flood water was flowing southeast in the Lodgepole Creek valley and then moving east and northeast along the North Fork Lodgepole Creek valley to the newly reversed flow in the present day northwest-oriented Squaw Creek valley at the same time flood flow was continuing to flow southeast on the South Fork Lodgepole Creek alignment to the newly eroded northeast-oriented Big Dry Creek valley. Headward erosion of the deep Missouri River-Musselshell River valley then beheaded and reversed what began as an east-oriented valley system.

Figure 10a: Lodgepole Creek at Musselshell River. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

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.