The South Fork Smith River-South Fork Musselshell River drainage divide area discussed here is located in Montana, USA and includes areas in the Castle Mountains. Although detailed topographic maps of the South Fork Smith River-South Fork Musselshell River drainage divide area have been available for more than fifty years detailed map evidence has not previously been used to interpret the region’s geomorphic history. The interpretation provided here is based entirely on topographic map evidence. The South Fork Smith River-South Fork Musselshell 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 South Fork Smith River-South Fork Musselshell River drainage divide ended when headward erosion of the Missouri River valley captured all southeast-oriented flood flow.

Preface:

introduction:

• The purpose of this essay is to use topographic map interpretation methods to explore South Fork Smith River-South Fork Musselshell River drainage divide area landform origins, 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 the South Fork Smith River-South Fork Musselshell River drainage divide area landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

South Fork Smith River-South Fork Musselshell River drainage divide area location map

Figure 1: South Fork Smith River-South Fork Musselshell 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 location map for the South Fork Smith River-South Fork Musselshell River drainage divide area. Figure 1 illustrates an area in central Montana. The South Fork Smith River and the South Fork Musselshell River both begin north of the Crazy Mountains. The South Fork Smith River (not labeled on figure 1) flows northwest to near White Sulphur Springs, where it joins the southwest-oriented North Fork Smith River (not labeled) to form the northwest-oriented Smith River, which joins the northeast-oriented Missouri River near Great Falls. The South Fork Musselshell River (not labeled on figure 1) flows in a northeast direction to join the North Fork Musselshell River near Martinsdale, and then to flow as the Musselshell River east-southeast and northeast to the figure 1 east edge. East of figure 1 the Musselshell River turns to flow north to join the Missouri River (in figure 1 northeast corner). The Missouri River originates at Three Forks (located near the figure 1 south edge, west half) and flows north and northwest through Canyon Ferry Lake (a large reservoir) and the Gates of the Rocky Mountains before turning to flow northeast to Great Falls. Northeast of Great Falls the Missouri River turns to flow southeast and east-northeast and southeast and is just barely visible in the figure 1 northeast corner. The Yellowstone River flows northwest and northeast from the figure 1 south center edge to Livingston and Big Timber and then southeast and northeast to Billings.

• Elk Peak (located southeast of White Sulphur Springs) is the highest point in the Castle Mountains (not labeled on figure 1). The southern Castle Mountains are located along the South Fork Smith River-South Fork Musselshell River drainage divide. Essays describing regions north and east of the South Fork Smith River-South Fork Musselshell River drainage divide area, including the North Fork Smith River-North Fork Musselshell River drainage divide area landform origins essay, have interpreted landform evidence in the context of immense southeast-oriented flood events (essays can be found under appropriate river names on the sidebar category list). Those essays suggest mountain ranges such as the Castle Mountains did not present obstacles to the flood movements and suggest the mountains ranges emerged as flood waters crossed the region. Such emergence could have occurred if the mountains were buried in easily eroded sediments and/or ice, which the flood waters removed, and/or if the mountain ranges emerged as flood waters eroded the region. South Fork Smith River-South Fork Musselshell River drainage divide evidence is interpreted the same way. Flood waters initially moved across a topographic surface where the present day Castle Mountains were not obstacles to southeast-oriented flood flow.

• Headward erosion of the deep Yellowstone River valley and subsequently the deep Musselshell River valley captured southeast-oriented flood flow as the Little Belt Mountains, Castle Mountains, and Crazy Mountains began to emerge. Southeast oriented flood water was channeled west of the Little Belt Mountains as the water flowed south to what was then the newly eroded Yellowstone River valley. At the same time flood waters were channeled between the Little Belt Mountains and the Castle Mountains and between the Castle Mountains and the Crazy Mountains as they flowed to the actively eroding Musselshell River valley. Headward erosion of the deep Missouri River valley then beheaded a major southeast-oriented flood flow moving flood waters southeast along the west flanks of the Little Belt and Castle Mountains. Flood waters on the northwest end of that beheaded flood flow route reversed flow direction to erode the northwest and north oriented Smith River valley. Reversed flood flow probably captured yet to be beheaded southeast-oriented flood flow moving on flood flow routes further to the south. With the aid of that captured flood water a significant north and northwest-oriented Smith River drainage basin evolved and the South Fork Smith River-South Fork Musselshell River drainage divide was created.

South Fork Smith River-South Fork Musselshell River drainage divide area detailed location map

Figure 2: South Fork Smith River-South Fork Musselshell River drainage divide area detailed location map. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 2 provides a somewhat more detailed map of the South Fork Smith River-South Fork Musselshell River drainage divide area. Meagher and Wheatland Counties are located in central Montana. The Castle Mountains are located in Meagher County, southeast of White Sulphur Springs. The South Fork Smith River and the South Fork Musselshell River both originate south of the Castle Mountains between the towns of Ringling and Loweth. The South Fork Musselshell River begins south of Loweth and flows northeast and joins the northeast-oriented North Fork Musselshell River near Martinsdale to form the southeast-oriented Musselshell River. The South Fork Smith River begins north of Ringling and flows northwest to join the southwest-oriented North Fork Smith River near White Sulphur Springs. The Smith River then flows northwest and north to the figure 2 northwest corner area. Note the south-oriented drainage routes south of Ringling and west of the Crazy Mountains. Those streams flow to the south-oriented Shields River, which joins the Yellowstone River near Livingston. The southwest-oriented stream at Ringling is Sixteenmile Creek, which flows to the figure 2 southwest corner area and then turns west to join the northwest-oriented Missouri River (west of figure 2).

• The discussion in this essay begins south of the Castle Mountains where both the South Fork Musselshell River and the South Fork Smith River originate. Drainage divides with Sixteenmile Creek and the south-oriented Shields River tributaries are illustrated and discussed. The essay concludes by looking at evidence in the Castle Mountain area. The entire figure 2 region was deeply eroded by an immense southeast-oriented flood at a time when flood waters initially could move on a topographic surface where the present day mountain ranges did not interfere with flood flow. As flood waters eroded the figure 2 map region the Little Belt, Castle, and Crazy  Mountains emerged (perhaps by a combination of deep erosion of the surrounding materials and of uplift occurring as flood waters eroded the region). Flood waters were channeled to flow southeast along the present day Smith River alignment to the present day Shields River drainage basin and then to what was then the newly eroded Yellowstone River valley. The deep Musselshell River valley eroded headward into the figure 2 map region with the South Fork eroding into the region south of the Castle Mountains and the North Fork eroding into the region north of the Castle Mountains. The northwest oriented Smith River valley and northwest oriented Smith River tributary valleys were initiated as southeast-oriented flood flow channels. Flood flow direction in those channels was systematically beheaded from north to south by headward erosion of the deep Missouri River valley to the northwest. Flood waters on the northwest ends of the beheaded flood flow routes reversed flow direction to erode the northwest and north-oriented Smith River drainage basin. Erosion of the Smith River drainage basin was aided by capture of yet to be beheaded flood flow from flood flow routes still south of what was then the actively eroding Missouri River valley head. The South Fork Smith River-South Fork Musselshell River drainage divide was created when headward erosion of the Missouri River valley beheaded and reversed southeast-oriented flood flow on the Smith River alignment.

South Fork Smith River and South Fork Musselshell River headwaters area

Figure 3: South Fork Smith River and South Fork Musselshell River headwaters area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the South Fork Smith River-South Fork Musselshell River drainage divide area. The south end of the Castle Mountains is located in the figure 3 north center edge area. The northwest end of the Crazy Mountains is located along the figure 3 east edge (south half). The South Fork Musselshell River originates east of Reservation Mountain (located west of Rimrock Reefs) and flows north and northeast through Bruno to the figure 3 northeast corner. The South Fork Smith River originates as a southeast-oriented stream on the south flank of the Castle Mountains and in the figure 3 center area turns southwest and then northwest to flow through Moss Agate to the figure 3 northwest corner. Sixteenmile Creek is the northwest and southwest oriented stream located in the figure 3 south center edge area and flowing southwest through Ringling. Note southeast-oriented South Fork Musselshell River tributaries flowing from the Castle Mountains area. These tributaries along with the southeast-oriented South Fork Smith River headwaters provide evidence southeast-oriented flood waters once flowed across the present day Castle Mountains. This evidence is explored in figures 7, 8, 9 and 10 below. Note also the well-defined through valleys linking the South Fork Smith River valley with the South Fork Musselshell River valley and also with the Sixteenmile Creek valley. These through valleys are explored in more detail in figures 4 and 5 below. Using the interpretation given in figures 1 and 2 above figure 3 evidence can be explained in the context of an immense southeast-oriented flood, which flowed across the entire figure 3 map area (including the Castle Mountains and Crazy Mountains areas shown). Flood waters originally flowed on a topographic surface at least as high as the highest figure 3 elevations today and as flood waters moved over the region they deeply eroded the landscape to produce the topographic surface seen today. It is possible the Castle Mountains and the Crazy Mountains were also uplifted as flood erosion occurred. As seen in figures 1 and 2 a large through valley extends south along the Crazy Mountains west flank from the figure 3 map area to the Yellowstone River valley near Livingston. As the Crazy Mountains and Castle Mountains emerged much of the southeast-oriented flood water moved south in that through valley to the Yellowstone River valley. However, some of the flood water was captured by headward erosion of the South Fork Musselshell River valley (and tributary valleys) and was diverted northeast between the Castle Mountains and the Crazy Mountains. Flood flow across the figure 3 map area ended when the deep northeast-oriented Missouri River beheaded southeast-oriented flood flow routes to this figure 3 map area. Flood waters on the northwest end of the those flood flow routes reversed flow direction to create the northwest-oriented Smith River drainage basin. Probably soon after headward erosion of the northeast-oriented Missouri River valley beheaded a major southeast-oriented flood flow route near Wolf Creek (see figure 1). Flood waters on the northwest end of that beheaded flood flow route reversed flow direction to create the present day northwest-oriented Missouri River valley between Three Forks and Wolf Creek (and also west of the Big Belt Mountains). That reversal of flood flow reversed flood flow in the present day Sixteenmile Creek valley and was the final flood flow reversal responsible for creating present day figure 3 drainage divides.

Detailed map of South Fork Smith River and South Fork Musselshell River headwaters area at Loweth

Figure 4: Detailed map of South Fork Smith River and South Fork Musselshell River headwaters area at Loweth. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 provides a detailed map of the South Fork Smith River-South Fork Musselshell River drainage divide area near Loweth at the Castle Mountains south end. Southeast-oriented South Fork Smith River headwaters flow from the figure 4 west edge (north half) through a maze of hogbacks and then turn to flow south to the figure 4 south edge (near the red highway). The east-oriented Dry Fork of the Musselshell River is located near the red highway and drains to the figure 4 east center edge (and joins the northeast-oriented South Fork Musselshell River east of figure 4). Sourdough Creek flows southeast from the Castle Mountains in the figure 4 north center area to join the Dry Fork. Southeast-oriented Warm Springs Creek (not labeled in figure 4) is located in the figure 4 northeast corner and also flows from the Castle Mountains to join the South Fork Musselshell River (see figure 3 above). Many of the ridges in figure 4 appear to be hogbacks left after flood waters deeply eroded the region. Flood waters originally flowed on a topographic surface higher than any present day figure 4 elevations and were responsible for eroding the entire figure 4 region. The southeast-oriented streams coming from the Castle Mountains highland areas provide evidence southeast-oriented flood flow originally moved to what was then the newly eroded and deep South Fork Musselshell River valley (and its tributary Dry Fork valley). Headward erosion of a deeper south-oriented valley then captured southeast-oriented flood flow moving on the South Fork Smith River headwaters alignment and the south-oriented escarpment surrounded basin located in the figure 4 southwest quadrant is a large abandoned headcut eroded as flood waters moved south (probably to what is today the Shields River valley). Through valleys in sections 10 and 15 linking the South Fork Smith River valley and the Dry Fork Musselshell River valleys provide evidence flood waters once flowed freely between the two drainage basins. Probably, the valleys were initially used by southeast-oriented flood water moving to the east-oriented Dry Fork valley. However, after headward erosion of the deeper south-oriented valley (in the figure 4 southwest quadrant), the through valley at Loweth was probably used by southeast-oriented flood water moving across the present day Sourdough Creek drainage basin that was captured by the deeper south-oriented valley (although flood flow moving across the Sourdough Creek drainage basin probably ended before a deeper and larger valley could be eroded).

Detailed map of South Fork Smith River and South Fork Musselshell River headwaters area at Reservation Mountain

Figure 5: Detailed map of South Fork Smith River and South Fork Musselshell River headwaters area at Reservation Mountain. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 provides a detailed map of the South Fork Smith River-South Fork Musselshell River drainage divide area south of the figure 4 map area and includes a thin overlap area with figure 4. Southwest oriented South Fork Smith River is located in the figure 5 northwest corner. The South Fork Musselshell River begins in the figure 5 east center area between Reservation Mountain and Rimrock Reefs and flows north to the figure 5 northeast corner area. Also beginning in the same area is south-oriented Woodson Creek, which south of figure 5 turns to flow west and to join Sixteenmile Creek (see figure 3 above). Southwest and south-oriented Durst Creek begins north of Reservation Mountain and flows to Hamen Reservoir (and then to Woodson Creek south of the figure 5 map area). Ridges are hogbacks, although valleys between the ridges are water eroded valleys. Note the high level through valley in section 25 linking Durst Creek headwaters with the north-oriented South Fork Musselshell River valley. That through valley and others like it provide evidence flood waters once flowed on a topographic surface at least as high as the Reservation Mountain Ridge. The through valleys are water eroded features and the presence of multiple through valleys suggests the water was flowing in multiple channels, such as might be expected in an anastomosing channel complex. What was happening in the figure 5 map area probably was an anastomosing channel complex eroded by southeast-oriented flood water was being captured by an anastomosing complex of south-oriented channels, where the largest and deepest channel was located in the figure 5 east half. The South Fork Smith River-South Fork Musselshell River drainage divide was probably created when southeast-oriented flood flow on the Smith River alignment was beheaded and reversed and the Sixteenmile Creek-South Fork Musselshell River drainage divide was created when east-oriented flood flow on the Sixteenmile Creek was beheaded and reversed to create the west-oriented Sixteenmile Creek drainage basin. It is possible these flow reversals and capture events were significantly aided by uplift of surrounding mountain areas as flood waters eroded the region.

South Fork Smith River-Shields River drainage divide area

Figure 6 illustrates the South Fork Smith River-Sixteenmile Creek-Shields River drainage divide area south of the figure 3 map area and includes overlap areas with figure 3. The South Fork Smith River is located in the figure 6 north center edge area and flows southwest and then northwest following the red highway using  the same route. The Bozeman Fork of the Musselshell River originates as a northwest-oriented stream between Box Canyon and Bald Ridge in the figure 6 northeast quadrant and then turns north to flow to the figure 6 north edge and then to join the South Fork Musselshell River. The northwest-oriented headwaters of the Bozeman Fork provide evidence the deep Musselshell River valley eroded headward around the Crazy Mountains north end and beheaded and reversed a southeast oriented flood flow route that had been moving flood waters across what are today the high Crazy Mountains. Sixteenmile Creek originates south of Bald Ridge and flows west, northwest, and southwest to Ringling and then southwest to the figure 6 west edge. Sixteenmile Creek headwaters are linked by a deep through valley with south-oriented Smith Creek, which flows to the west, southwest, and south-oriented Shields River. East of figure 6 the west oriented Shields River has several west and northwest oriented tributaries, which originate in the high Crazy Mountains, but which are also linked by high level through valleys with southeast, east, and northeast oriented Musselshell River and Yellowstone River tributaries. While those high level through valleys will be illustrated and described in a different essay, they provide evidence southeast oriented flood water once moved across what are today the high Crazy Mountains and that the west oriented Shields River valley eroded headward into the present day Crazy Mountains area to capture southeast oriented flood flow. Potter Creek is the south-oriented Shields River tributary located in the figure 6 south center near the red highway. Potter Creek joins the south-oriented Shields River south of the figure 6 map area and the Shields River then flows south to join the Yellowstone River near Livingston (see figure 1). Figure 6 illustrates the north-south through valley linking the northwest-oriented South Fork Smith River valley with the south oriented Shields River valley. This through valley was eroded by immense quantities of southeast and south oriented flood water channeled between what must have been emerging mountain ranges on both sides. South oriented flood waters shortly before being beheaded and reversed by Missouri River valley headward erosion were moving to what was then the newly eroded Yellowstone River valley. However, prior to headward erosion of the Yellowstone River valley the south-oriented flood waters may have continued south and southeast across what is today the Yellowstone Plateau.

South Fork Smith River-South Fork Musselshell River drainage divide area in Castle Mountains

Figure 7: South Fork Smith River-South Fork Musselshell River drainage divide area in Castle Mountains. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the South Fork Smith River-South Fork Musselshell River drainage divide in the Castle Mountains and is located north of figure 3. Figure 7 includes overlap areas with figure 3. The northwest-oriented South Fork Smith River is located near the red highway in the figure 7 southwest corner. Southeast-oriented South Fork Smith River headwaters are located in the figure 7 south center edge area. The northeast-oriented South Fork Musselshell River flows from Bruno to Lennep (along the figure 7 east edge) in the figure 7 southeast quadrant. The Dry Fork Musselshell River flows from Loweth to Bruno near the figure 7 south edge. Note the multiple southeast-oriented South Fork Musselshell River tributaries flowing  from the Castle Mountains. Also note how South Fork Smith River tributaries are either northwest oriented or have northwest-oriented valley segments. Figures 8, 9 and 10 below provide detailed maps to illustrate high level through valleys crossing what are today high drainage divides in the Castle Mountains. The northwest-southeast oriented drainage alignment and the high level through valleys provide evidence of multiple southeast-oriented flood flow channels eroded into what was then an emerging Castle Mountains upland region. Why would the Castle Mountains emerge while an immense southeast-oriented flood was rapidly eroding the adjacent region? Emergence of the Castle Mountains may have been as flood waters removed easily eroded materials, such as easily eroded sediments and/or ice, from around the mountains and/or as the mountains were uplifted. While the source of the southeast-oriented flood waters described in this essay cannot be determined from evidence presented here, 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 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 Castle Mountains, during an immense southeast-oriented flood. A thick North American ice sheet, in a deep “hole” created in part by the ice sheet’s weight, would probably cause crustal warping elsewhere on the continent, especially along ice sheet margins. Rapid erosion of significant amounts of overlying bedrock material might also trigger localized uplift.

South Fork Smith River-South Fork Smith River drainage divide area

Figure 8 provides a detailed map of the South Fork Smith River-South Fork Smith River drainage divide area south of the Castle Mountains. The northwest-oriented South Fork Smith River is located in the figure 8 southwest corner area. Southeast-oriented South Fork Smith River headwaters are located in sections 7 and 8 in the figure 8 northeast quadrant. The high ridge separating the southeast-oriented South Fork Smith River headwaters from the northwest-oriented South Fork Smith River is a mostly likely a large hogback composed of erosion resistant rock. However, the southeast-oriented headwaters basin is a water-eroded feature and probably is a large southeast-oriented abandoned headcut, eroded by southeast-oriented flood waters. A prominent high level through valley in section 7 provides evidence flood waters once flowed across the ridge (or hogback), although probably at time when the regional topography looked very different from it does today. Several less obvious through valleys can also be seen. The prominent through valley in section 7 suggests final flood water movement was to the west, which suggests the headwaters basin or valley may have been filled with water at the time southeast-oriented flood flow in the present day northwest-oriented South Fork Smith River valley was beheaded and reversed. If so much of the erosion of the South Fork Smith River valley was done by flood waters moving northwest, which means the South Fork Smith River valley was being fed by large quantities of yet to be beheaded southeast-oriented flood flow further to the south. Based on evidence seen in this essay one route such flood waters might have used would have been east and northeast along what is today the Sixteenmile Creek alignment. Flood flow moving east and northeast on that Sixteenmile Creek alignment would not have been beheaded and reversed until after southeast-oriented flood flow on the South Fork Smith River alignment was beheaded and reversed. Another interpretation, although not necessarily different, is large volumes of flood waters “sloshed” back and forth as deep valleys eroded headward into the region between what were then emerging mountain ranges.

Cottonwood Creek-Warm Springs Creek drainage divide area

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

Figure 9 provides a detailed map of the Cottonwood Creek-Warm Springs Creek drainage divide area in the high Castle Mountains and this region was shown in less detail in figure 7 above. Drainage divides along high ridges in mountain range may appear to be unlikely places to look for flood evidence, yet if the “thick ice sheet that melted fast” paradigm being tested by this essay series is correct, multiple through valleys eroded across such high level mountain ridges provide evidence of former anastomosing channel complexes. The West Fork Cottonwood Creek flows south in sections 14 and 23 and joins the southwest-oriented East Fork Cottonwood Creek in section 23. From section 23 Cottonwood Creek flows southwest to the figure 9 west edge and then turns to flow northwest and southwest to the northwest-oriented South Fork Smith River. The East Fork Cottonwood Creek flows southwest from section 18 through sections 13 and 24 to reach the West Fork in section 23. Warm Springs Creek originates southwest of Elk Peak and flows south through section 19 and then southeast through the northeast corner of section 30 and the southwest corner of section 29 to the figure 9 south edge. Note how other than in its headwaters area, Warm Springs Creek is southeast-oriented and has southeast-oriented tributaries. Follow the drainage divide southeast of Cottonwood Creek and East Cottonwood Creek starting in the figure 9 southwest corner. In section 26 there is a through valley (or saddle) linking the Cottonwood Creek valley with the southeast-oriented headwaters of a South Fork Smith River tributary (see figure 7). In the northwest corner of section 30 there is a shallow through valley (or saddle) linking headwaters of a northwest-oriented East Fork Cottonwood Creek tributary with a headwaters of a southeast-oriented Warm Springs Creek tributary. In the west center of section 19 is another shallow through valley (or saddle) linking headwaters of another northwest-oriented East Fork Cottonwood Creek tributary with headwaters of another southeast-oriented Warm Springs Creek tributary. And another shallow through valley (or saddle) is located in the figure 19 northwest quadrant linking headwaters of a west and southwest-oriented East Fork Cottonwood Creek tributary with the same southeast-oriented Warm Springs Creek tributary. These through valleys are water eroded features and provide evidence of a former drainage pattern. The multiple through valleys suggest that former drainage pattern was an anastomosing channel complex supplying flood water to erode what must have been an actively eroding deep Warm Springs valley complex. Headward erosion of the deep Cottonwood Creek valley and tributary valleys then captured the southeast-oriented flood flow to the newly eroded Warm Springs Creek valley. Uplift (or at least emergence) of the Castle Mountains as flood waters eroded the region may have greatly aided this flood capture event.

Willow Creek-Boulder Creek drainage divide area

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

Figure 10 provides a detailed map of the Willow Creek-Boulder Creek drainage divide area located north of the figure 9 map area and includes overlap areas with figure 9. Wapiti Peak located in the figure 10 center and Elk Peak located in the figure 10 south center are the two highest points in the Castle Mountains. Willow Creek flows northwest from the Wapiti Peak area to the figure 10 northwest corner. From the figure 10 map area Willow Creek flows northwest, north, and northwest to reach the North Fork Smith River. Boulder Creek flows southeast in the figure 10 southeast quadrant to the figure 10 southeast corner. From figure 10 Boulder Creek flows southeast to join southeast-oriented Alabaugh Creek, which flows to join the northeast-oriented South Fork Musselshell River at Lennep (see figure 7). Note the through valley (or saddle) between Wapiti Peak and Elk Peak. While today it is just a saddle eroded between two high mountain peaks, that landscape feature originated as a water eroded valley. The interpretation presented here is the valley was eroded by southeast-oriented flood flow moving across the Castle Mountain area at a time when the Castle Mountains did not stand high above the surrounding region. Further, the interpretation presented here suggests the northwest-oriented Willow Creek valley alignment and the southeast oriented Boulder Creek alignment were established by that same southeast oriented flood channel alignment. This interpretation requires immense quantities of water to erode the valleys seen in figure 10 and also requires that the Castle Mountains emerged as a significant obstacle to flood movements as flood waters were eroding the region. As previously mentioned emergence of the Castle Mountains may have occurred as flood waters removed easily eroded sediments and/or ice surrounding the Castle Mountain region and/or as the Castle Mountains were uplifted. The immense quantities of water can be explained in the context of the “thick ice sheet that melted fast” paradigm, especially if the thick ice sheet was located in a deep North American “hole”. However, the interpretation presented here is not possible in the context of commonly accepted continental ice sheet paradigms.

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.