A geomorphic history based on topographic map evidence

The Smith River-Belt Creek drainage divide area in the Little Belt Mountains region discussed here is located in Montana, USA. Although detailed topographic maps of the Smith River-Belt 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 Smith River-Belt 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 Smith River-Belt Creek drainage divide area landform origins in the Little Belt Mountains region of 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 and/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 comment here.

• This essay is also exploring a new geomorphology 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 other Missouri River drainage basin landform origins research project essays is a thick North American ice sheet, comparable in thickness to the Antarctic ice sheet, occupied the North American region usually recognized to have been glaciated, and through its weight and erosive actions created a deep North American “hole”. The southwestern rim of that deep “hole” is today preserved in the high Rocky Mountains. The ice sheet 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 Smith River-Belt Creek drainage divide area landform evidence in the Little Belt Mountains area will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm. This essay is included in the Missouri River drainage basin landform origins research project essay collection.

Smith River-Belt Creek drainage divide area location map

Figure 1: Smith River-Belt 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 Smith River-Belt Creek drainage divide area in the Little Belt Mountains location map and illustrates a region in central Montana. The Little Belt Mountains are located east of Great Falls and are labeled in figure 1 with Big Baldy Mountain being the highest point. Southwest of the Little Belt Mountains are the Big Belt Mountains. The Smith River flows northwest between the Big Belt and Little Belt Mountains and joins the Missouri River near Great Falls. The Missouri River is located southwest of the Big Belt Mountains and flows  through Canyon Ferry Lake and Holter Lake and then turns northeast from Wolf Creek to flow to Great Falls, Fort Benton, and Loma before turning southeast, east-northeast, and southeast to flow to the figure 1 east edge. Belt Creek is shown on figure 1, but is not labeled, and flows northwest from near Big Baldy Mountain to Armington and Belt before joining the northeast-oriented Missouri River northeast of Great Falls. The Smith River-Belt Creek drainage divide area considered in this essay is located in the Little Belt Mountains, however the northeast-oriented Missouri River valley played an important in developing the present day Smith River and Belt Creek drainage systems. Also important to this discussion are the east-southeast oriented Musselshell River located in the figure 1 southeast quadrant and the northeast-oriented Judith River in the Judith Basin.

• Landform evidence in this essay is interpreted in the context of an immense southeast-oriented flood that crossed the entire figure 1 map area. Prior to Missouri River valley headward erosion the deep Musselshell River valley eroded headward into the figure 1 map area to capture southeast-oriented flood waters that had been moving to the newly eroded Yellowstone River valley (located south of figure 1) and to divert the captured flood waters further to the north and northeast. Initially the Little Belt Mountains were not obstacles to southeast-oriented flood flow (the Little Belt Mountains may have been surrounded by easily eroded sediments and/or ice, which flood waters removed, or the Little Belt Mountains may have been uplifted above the surrounding region as flood waters eroded the area). As flood waters deeply eroded the figure 1 map area the Little Belt Mountains emerged as significant obstacles to flood movements, especially after the deep east-oriented Missouri River valley eroded headward into the region north of the present day Judith Basin. At first southeast-oriented flood waters eroded valleys into the emerging Little Belt Mountains. Later flood waters were channeled around the Little Belt Mountains. Headward erosion of the northeast-oriented Missouri River valley north of the Little Belt Mountains subsequently captured all southeast-oriented flood waters.

• Important to understanding what happened are northwest-oriented Missouri River tributaries to the northeast-oriented Missouri River valley in the Great Falls area. These northwest-oriented Missouri River tributary valleys were initiated as southeast-oriented flood flow routes that supplied significant water to help erode what are today through valleys separating the Little Belt Mountains, Castle Mountains (not labeled in figure 1, but Elk Peak is the labeled high point), and Crazy Mountains, among others. Southeast-oriented flood flow in what were then southeast-oriented valleys was reversed when headward erosion of the northeast-oriented Missouri River valley beheaded the southeast-oriented flood flow routes across the Little Belt Mountains region. Reversal of flow may have also been aided by Little Belt Mountains uplift as flood waters were eroding the figure 1 map area. Other essays describe landform evidence in the nearby Missouri River-Arrow Creek drainage divide area, the Arrow Creek-Judith River drainage divide area, the North Fork Smith River-North Fork Musselshell River drainage divide area, and the South Fork Smith River-South Fork Musselshell River drainage divide area, all located near the Smith River-Belt Creek drainage divide areas discussed here (essays can be found under appropriate river names on the sidebar category list, for example Judith River drainage divide essays are found under  Judith River.

Smith River-Belt Creek drainage divide area detailed location map

• Figure 2 illustrates a somewhat more detailed map of the Smith River-Belt Creek drainage divide area discussed in this essay. Cascade, Fergus, and Judith Basin Counties are located in Montana. Chouteau County is the unlabeled county located north of Judith Basin County. Meagher County is the unnamed county located in the figure 2 south center area. The Missouri River flows northwest in the figure 2 southwest corner and then flows northeast from the figure 2 west edge to Great Falls and then to the figure 2 north edge. Green areas are National Forest lands, which usually are located in mountainous areas. The smaller green area in the figure 2 northeast quadrant is located in the Highwood Mountains. The green area in the figure 2 southwest quadrant is located in the Big Belt Mountains. The larger green area dominating the figure 2 south center area and southeast quadrant is located in the Little Belt Mountains. The county boundary in the Little Belt Mountains (northeast of the red highway) is the Smith River-Belt Creek drainage divide. Belt Creek originates in the Little Belt Mountains and flows north-northwest near the red highway to Armington and Belt. Belt Creek flows north from Belt to the Cascade-Chouteau County boundary and then turns to flow northwest along the county border to the northeast-oriented Missouri River. The Smith River originates south of figure 2 and flows north to and along the west edge of the National Forest land boundary in the figure 2 southwest quadrant before turning to flow north-northwest to join the northeast-oriented Missouri River. Sheep Creek is an important Smith River tributary, which flows south and west along the red highway from the Belt Creek headwaters and then flows northwest and west to the north-northwest oriented Smith River. West-oriented Tenderfoot Creek, located in northern Meagher County (in the figure 2 center south area) is another important Smith River tributary. Also note northwest-oriented Ming Coulee and Sand Coulee, both located between the Smith River and Belt Creek in the area between the Little Belt Mountains and the northeast-oriented Missouri River.

• Evidence presented in this essay suggests the Smith River, Ming Coulee, Sand Coulee and Belt Creek valley alignments and the alignments of their northwest-oriented tributaries originated as southeast-oriented flood flow channels that were first captured by headward erosion of what was then an actively eroding Yellowstone River valley located south of the figures 1 and 2 map areas. Later headward erosion of the southeast-oriented Musselshell River valley and the northeast-oriented Judith River valley captured the southeast-oriented flood flow and diverted the flood waters to what was then the actively eroding Missouri River valley northeast of the figure 2 map area. Evidence presented here demonstrates southeast-oriented flood flow moved across the present day Little Belt Mountains. Based on this evidence the Little Belt Mountains are interpreted to have emerged as flood waters eroded the region. Emergence of the Little Belt Mountains may have occurred as flood waters removed easily eroded sediments and/or ice that had buried the Little Belt Mountains and/or as the Little Belt Mountains were uplifted while flood waters eroded the region. In either case southeast-oriented flood flow across the figure 2 map area ended when headward erosion of the northeast-oriented Missouri River valley northwest of the Little Belt Mountains captured the southeast-oriented flood flow routes.

• The immense quantities of flood water required to erode the Figure 2 map region probably came from a rapidly melting North American ice sheet located in a deep “hole”. Why would such an ice sheet generate immense southeast-oriented floods that deeply eroded central and western Montana mountain ranges? The massive southeast-oriented floods and deep erosion in central and western Montana mountain ranges makes sense if the deep “hole” was eroded into a topographic surface equivalent in elevation to the crests of highest central and western Montana mountain ranges today. In other words, central and western Montana mountain ranges were located along the deep “hole” rim and initially melt water from the rapidly melting ice sheet flowed southeast along the ice sheet margin. As the ice sheet melted flood waters were captured by headward erosion of deep northeast-oriented valleys so as to divert flood waters into space being opened up by the rapidly melting ice sheet. To visualize what happened think in terms of an Antarctica-sized ice sheet developing on a North American topographic surface at least as high as the high Rocky Mountain peneplain defined by crests of high Rocky Mountain peaks today. The ice sheet through its weight and deep glacial erosion created a deep “hole” in that topographic surface. Then the ice sheet began to melt faster than it was being formed. Essays in this Missouri River drainage basin landform origins research project collectively build a strong case the Missouri River drainage basin landforms evolved during the resulting melt water floods.

Smith River-Belt Creek drainage divide area north of Little Belt Mountains

Figure 3: Smith River-Belt Creek drainage divide area north of Little Belt Mountains. 

United States Geological Survey map digitally presented using National Geographic Society TOPO software.

• Figure 3 illustrates the Smith River-Belt Creek drainage divide along the north flank of the Little Belt Mountains. The Smith River flows north from the figure 3 southwest corner area and then turns northwest to flow to the figure 3 west center edge. Belt Creek flows northwest from the figure 3 east center edge and then turns north to flow to the figure 3 northeast corner area. The East Fork of Sand Coulee is the north-oriented stream flowing from west of Tiger Butte to the figure 3 north edge. Sand Coulee is the northwest-oriented stream flowing through Evans to the figure 3 north center area. Ming Coulee is the northwest-oriented stream west of Sand Coulee flowing through Calvert to the figure 3 north edge. Deep Creek is the major northwest-oriented Smith River tributary in the figure 3 southwest quadrant. Logging Creek is the northeast-oriented Belt Creek tributary in the figure 3 southeast quadrant.

• Some of the most remarkable landform features observable in figure 3 and better observed on more detailed maps are the numerous through valleys linking the present day drainage routes. The through valleys range from well-defined deep valleys to notches eroded into what are today high drainage divides. Each of those through valleys provides evidence of a former drainage route. In the case of the well-defined deep valleys reconstruction of the former drainage route is usually simple. However, in the case of notches eroded into present day high drainage divides most evidence of the former drainage route has been removed.

• What are some of through valleys visible in figure 3. Starting in the east there are well-defined through valleys north and west of Tiger Butte (these are illustrated in detail in figure 4 below). Several through valleys link the northwest oriented Sand Coulee valley with the north-oriented East Fork Sand Coulee valley. Through valleys also cross the Ming Coulee-Sand Coulee drainage divide and the Smith River-Ming Coulee drainage divide. Somewhat more subtle through valleys can be seen linking the heads of north-oriented drainage routes with other north-oriented drainage routes. For example, note the higher level through valley linking the headwaters area of Sand Coulee with the head of northeast-oriented Sawmill Gulch (in the figure 3 southeast quadrant). Sawmill Gulch flows to northeast-oriented Logging Creek, which flows to northwest and north-oriented Belt Creek. Similar through valleys can be found at the heads of virtually all figure 3 valleys.

• What do these through valleys mean? The large number of through valleys can best be explained in the context of an immense southeast-oriented flood that flowed across the figure 3 map area initially in an ever-changing anastomosing (or interconnected) channel complex. Ever changing means as flood waters eroded one channel deeper it captured flood flow from adjacent channels, sometimes causing flood flow reversals. Southeast-oriented flood flow across the figure 3 map area was then beheaded by headward erosion of the deep northeast-oriented Missouri River valley to the north of figure 3 (see figures 1 and 2). Headward erosion of the Missouri River valley beheaded the southeast-oriented flood flow routes one route at a time from east to the west. Because the newly eroded Missouri River valley was much deeper flood waters on the northwest ends of the newly beheaded southeast-oriented flood flow routes reversed flow direction to flow north and northwest into the new Missouri River valley. Also, because flood flow channels were anastomosing or interconnected, reversed flood flow on a newly beheaded flood flow route usually captured yet to be beheaded southeast-oriented flood flow from flood flow routes further to the west. Captures of such yet to beheaded flood flow eroded east and northeast-oriented valleys. The previously cited high level Sand Coulee-Sawmill Gulch through valley for example was eroded by yet to be beheaded southeast-oriented flood flow using the Sand Coulee alignment that had been captured by newly beheaded and reversed flood flow moving north on the Belt Creek alignment. Not only does this interpretation explain the east and northeast-oriented through valleys the process also provides a source for the large volumes of water required to erode the north-oriented valleys.

Detailed map of East Fork Sand Coulee-Belt Creek drainage area

Figure 4: East Fork Sand Coulee-Belt Creek drainage area.

United States Geological Survey map digitally presented using National Geographic Society TOPO software.

• Figure 4 illustrates the East Fork Sand Coulee-Belt Creek drainage divide area near Tiger Butte seen in less detail in figure 3 above. East Fork Sand Coulee is the north oriented drainage route originating immediately west of Tiger Butte. North of figure 4 the East Fork Sand Coulee turns to flow northwest to join Sand Coulee. Lick Creek is the south oriented drainage route immediately south of the Sand Coulee headwaters. South of figure 4 Lick Creek flows southeast to northeast-oriented Logging Creek, which flows to the north oriented Belt Creek. Tiger Creek is the southeast and northeast-oriented drainage route immediately north of Tiger Butte. Tiger Creek joins the north-northwest and north-northeast oriented Belt Creek at the figure 4 east edge. Half Breed Creek is the northwest oriented stream in the figure 4 northwest quadrant. Half Breed Creek flows to northwest oriented Sand Coulee. Multiple through valleys are present in figure 4 and provide evidence of multiple southeast-oriented flood flow channels that were captured and diverted to flow east or northeast and/or that were reversed to flow northwest or north. For example, a through valley links the north and northwest oriented East Fork Sand Coulee valley with south and southeast-oriented Lick Creek valley. That through valley provides evidence that southeast-oriented flood waters once flowed from the present day Sand Coulee drainage basin area to the present day Lick Creek drainage basin. The higher level through valley linking the northwest-oriented Half Breed Creek headwaters valley with the head of the north-oriented East Fork Sand Coulee valley provides evidence southeast-oriented flood waters also moved southeast in the Half Breed Creek valley to the Lick Creek valley prior to reversal of flow in the present day East Fork Sand Coulee valley. An unnamed northwest- and west-oriented Sand Coulee tributary valley (draining to the figure 4 west edge and then to northwest-oriented Sand Coulee west of figure 4) is also linked with the south-oriented Lick Creek valley. This unnamed Sand Coulee tributary valley provides evidence of still another flood flow route between the present day Sand Coulee valley and the Lick Creek valley. These through valleys and others (such as the through valley linking the East Fork Sand Coulee valley with Tiger Creek headwaters) provide evidence of a southeast-oriented anastomosing channel complex that was systematically beheaded and reversed to create the present day north-oriented drainage system.

Tenderfoot Creek-Sheep Creek drainage divide area

Figure 5: Tenderfoot Creek-Sheep Creek drainage divide area. 

United States Geological Survey map digitally presented using National Geographic Society TOPO software.

• Figure 5 illustrates the Tenderfoot Creek-Sheep Creek drainage divide area south of the figure 3 map area and there are no overlap areas with figure 3. The Smith River flows northwest in the figure 5 southwest quadrant to the figure 5 west edge and then flows north to the figure 5 northwest corner. Tenderfoot Creek flows west-northwest and west across the top of figure 5 from the figure 5 east edge to join the Smith River in the figure 5 northwest corner area. Sheep Creek flows northwest from the figure 5 southeast corner and then turns to flow southwest and west to join the northwest-oriented Smith River in the figure 5 southwest quadrant.  Eagle Creek flows southwest from the Williams Mountain area (figure 5 northeast quadrant) to join the northwest-oriented Smith River in the figure 5 southeast quadrant. Black Butte Creek flows northwest to join southwest and west-oriented Sheep Creek in the figure 5 south center area. Note the through valley north of where Black Butte Creek joins Sheep Creek linking the Eagle Creek and Sheep Creek valleys. Figure 6 below provides a detailed map of that through valley. Woods Creek and North Fork Eagle Creek flow south from the figure 5 center north area to join southwest-oriented Eagle Creek in the figure 5 center south area. Note how Woods Creek headwaters are linked by a well-defined through valley south of Woods Mountains with the west- and northwest-oriented South Fork Tenderfoot Creek valley. This through valley was initially eroded by southeast-oriented flood flow that moved south and southeast to what is today the northwest-oriented Sheep Creek valley in the figure 5 southeast quadrant. Numerous other through valleys can be seen in the figure 5 map area, some well-defined and some subtle notches eroded into high ridges.

• These through valleys again provide evidence of earlier drainage routes, just as the present day drainage routes are located in valleys initiated by the earlier drainage. My best interpretation for development of the figure 5 valleys is the region was initially eroded by southeast-oriented flood flow moving in anastomosing channels over the entire figure 5 map area. Flood waters initially moved on a topographic surface at least as high as the highest figure 5 elevations today. As flood waters were eroding the region the Little Belt Mountains began to emerge as an upland region and the anastomosing channels eroded valleys into the emerging upland surface. Headward erosion of the deep Missouri River valley and deep tributary valleys then systematically began to behead and reverse flood flow in those anastomosing channels. Because the channels were interconnected this capture and reversal process resulted in numerous secondary captures and flow reversals until headward erosion of the deep Missouri River valley had beheaded and reversed all southeast-oriented flood flow routes moving water into the figure 5 map area and the present day drainage system had evolved.

Detailed map of Eagle Creek-Sheep Creek drainage divide area

Figure 6: Detailed map of Eagle Creek-Sheep Creek drainage divide area. 

United States Geological Survey map digitally presented using National Geographic Society TOPO software.

• Figure 6 provides a detailed map of the Eagle Creek-Sheep Creek through valley seen in less detail in figure 5 above. Eagle Creek flows northwest and southwest in the figure 6 northeast quadrant and northwest and southwest to the figure 6 west edge. Black Butte Creek in the figure 6 southeast quadrant flows northwest to join southwest-oriented Sheep Creek, which flows southwest to the figure 6 south center edge. The northwest-southeast oriented through valley is located in the figure 6 center area and links a short northwest-oriented Eagle Creek valley segment with the northwest-oriented Black Butte Creek valley. The through valley, like numerous other through valleys in the figure 5 map area, provides evidence that water once flowed between the present day Eagle Creek and Sheep Creek valleys. The through valley orientation may also be related to the underlying geologic units (e.g. Sheep Creek Bar may be an east-oriented hogback), however the valley is a water eroded feature. By itself this through valley is not evidence of an immense southeast-oriented flood flowing across the region. However, when combined with the other parallel present day valleys (e.g. Smith River valley and the Eagle Creek-Jack Creek-Sheep Creek through valley seen in the figure 5 southeast quadrant) this through valley is best explained in the context of a channel in an evolving anastomosing channel complex. The anastomosing channel complex evolved as flood waters eroded deeper channels into the region and also as headward erosion of the deep Missouri River valley (and its deep tributary valleys) eroded headward to behead and reverse southeast-oriented flood flow routes crossing the region.

Tenderfoot Creek-Belt Creek drainage divide area

Figure 7: Tenderfoot Creek-Belt Creek drainage divide area. 

United States Geological Survey map digitally presented using National Geographic Society TOPO software.

• Figure 7 illustrates the Tenderfoot Creek-Belt Creek drainage divide area east and north of the figure 5 map area and includes overlap areas with figure 5. Tenderfoot Creek flows northwest from the figure 7 south center area to the figure 7 west edge. The red highway follows north-northwest oriented Belt Creek in the figure 7 east half. Tillinghast Creek is the north-northwest and north-northeast oriented stream west of Belt Creek (and west of Keegan Peak). North of figure 7 Tillinghast Creek turns north-northwest and north-northeast to flow to northwest oriented Belt Creek. The present day Tillinghast Creek-Belt Creek valley arrangement appears to have originated in an anastomosing channel complex, where the reversal of flood flow in the Belt Creek valley eroded the north-northeast oriented Tillinghast Creek valley which beheaded and reversed south-southeast-oriented flood flow in the southern Tillinghast Creek channel. Headward erosion of the Tillinghast Creek valley apparently captured significant southeast-oriented flood flow that moved along the present day northwest oriented Tenderfoot Creek valley alignment. However, headward erosion of the north-northwest oriented Belt Creek valley and northeast-oriented tributary valleys, such as the Harley Creek valley and Graveyard Gulch valley (in the figure 7 southeast quadrant) captured flow to the Tillinghast Creek valley and diverted the flow to the Belt Creek valley. The Pack Trail west of Thunder Mountain follows northwest oriented Pilgrim Creek headwaters. North of figure 7 Pilgrim Creek turns north-northeast to flow to southeast-oriented Logging Creek, which flows to Belt Creek. The northwest oriented “Gulch” in the figure 7 northwest corner area is Timber Gulch, which flows to northeast and southeast oriented Logging Creek, which flows to Belt Creek, Note how Timber Gulch headwaters are linked by a shallow through valley notched into the present day high level drainage divide. That shallow through valley links the northwest oriented Timber Gulch valley with the southeast-oriented Placer Creek valley. Placer Creek today flows to southwest-oriented Balsinger Creek, which flows to northwest and southwest-oriented Tenderfoot Creek, which flows to north and northwest oriented Smith River. Headward erosion of the deep Logging Creek valley beheaded southeast-oriented flood flow on the Timber Gulch-Placer Creek valley alignment and created the high level Timber Gulch-Placer Creek drainage divide seen today. Reversal of southeast-oriented flood flow on the beheaded southeast-oriented flood flow routes that created the present day northwest- and north-oriented Smith River drainage system reversed flood flow in the Tenderfoot Creek drainage basin.

Detailed map of Tenderfoot Creek-Harley Creek drainage divide area

Figure 8: Detailed map of Tenderfoot Creek-Harley Creek drainage divide area. 

United States Geological Survey map digitally presented using National Geographic Society TOPO software.

• Figure 8 provides a detailed map of the Tenderfoot Creek-Harley Creek drainage divide area seen in less detail in figure 7 above. Tenderfoot Creek flows west-northwest from the figure 8 south center area to the figure 8 west edge. Harley Creek flows northeast and east from the figure 8 center area to the figure 8 east edge. East of figure 8 Harley Creek joins north-northwest oriented Belt Creek. Graveyard Creek flows northeast from the figure 8 southeast quadrant to the figure 8 east edge and east of figure 8 joins Harley Creek. Tillinghast Creek is the unnamed north-oriented stream in the figure 8 north center (east) area. Headwaters of northeast-oriented Wilson Creek can be seen west of the Tillinghast Creek headwaters along the figure 8 north edge (northeast of Dry Park). Wilson Creek is a Tillinghast Creek tributary. Note the through valley at Dry Park linking the northeast-oriented Wilson Creek valley with an unnamed south-southwest oriented Tenderfoot Creek tributary valley. Also note the through valley at Harley Park linking the north-oriented Tillinghast Creek headwaters with the east-oriented headwaters of Harley Creek and also with headwaters of west-northwest oriented Tenderfoot Creek. These through valleys and other similar through valleys provide evidence that water once flowed across the drainage divides now separating the different drainage basins. The through valleys probably were initiated by south- and southeast-oriented flood flow, but probably were used by reversed flood flow as southeast-oriented flood flow routes were systematically beheaded and reversed. Flood flow on the Belt Creek valley alignment (east of figure 8) would have been reversed first and the northeast-oriented Harley Creek and Graveyard Creek valleys probably eroded southwest from that reversed flood flow route to capture yet to be reversed flood flow further to the west. Flood flow in the Tillinghast Creek valley was probably reversed next and flood flow moved from the Tenderfoot Creek valley to the newly reversed Tillinghast Creek valley in the Dry Park through valley and in the Harley Park through valley. The Harley Park through valley carried more water and eroded deeper, with the Harley Creek capturing much or all of the east-oriented flood flow. Finally, south-oriented flood flow on the Smith River valley alignment was beheaded and reversed causing a reversal of flood flow in the Tenderfoot Creek drainage basin and creating the present day drainage routes.

Sheep Creek-Belt Creek headwaters area

Figure 9: Sheep Creek-Belt Creek headwaters area. 

United States Geological Survey map digitally presented using National Geographic Society TOPO software.

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• Figure 9 illustrates the Sheep Creek-Belt Creek drainage divide area south and east of the figure 7 map area and includes overlap areas with figure 7. Kings Hill Pass is located on the red highway in the figure 9 center area. Belt Creek originates in the Kings Hill Pass area and the highway north of Kings Hill Pass is located in the Belt Creek valley. Sheep Creek originates on the south side of Kings Hill Pass and the highway is located in the Sheep Creek all the way to the figure 9 southeast corner, where Sheep Creek flows west-northwest and the highway turns south. West of the figure 9 map area Sheep Creek flows northwest, southwest, and west to join northwest-oriented Smith River (see figure 5 above). East oriented drainage to the figure 9 east edge flows to the northeast-oriented Judith River. South-oriented drainage south of Lost Fork Ridge along the figure 9 south edge in the figure 9 southeast corner area includes the headwaters of the North Fork Smith River and the headwaters of the North Fork Musselshell River (the North Fork Smith River-North Fork Musselshell River drainage divide area essay illustrates and discusses the Lost Fork Ridge area). Southeast-oriented flood flow along the Belt Creek valley alignment was flowing to what was then the newly eroded southeast-oriented North Fork Musselshell River valley and was captured south of Lost Fork Ridge by headward erosion of the southwest-oriented North Fork Smith River valley (which at that time was probably eroding headward from the deep Yellowstone River valley). Headward erosion of Judith River tributary valleys captured southeast-oriented flood flow moving on the Belt Creek alignment north of Lost Fork Ridge and diverted the flood flow northeast to what was then the newly eroded east-oriented Missouri River valley north of the Judith Basin (see figure 1). When headward erosion of the Missouri River valley beheaded and reversed southeast-oriented flood flow using the Belt Creek alignment southeast-oriented flood flow continued to move on the Smith River-Sheep Creek alignment and was captured by reversed flood flow on the Belt Creek alignment. In other words the southwest-oriented flood flow moved east and north on the present day Sheep Creek valley alignment and then northwest on the Belt Creek valley alignment. Headward erosion of the Missouri River valley then beheaded and reversed flood flow in the Smith River drainage basin. These flood flow reversals may have been greatly aided by “emergence” of the Little Belt Mountains as flood waters eroded the figure 9 map region.

Detailed map of Sheep Creek-Belt Creek headwaters area

Figure 10: Detailed map of Sheep Creek-Belt Creek headwaters area.

United States Geological Survey map digitally presented using National Geographic Society TOPO software.

• Figure 10 provides a detailed map of the Sheep Creek-Belt Creek drainage divide area at Kings Hill Pass  illustrated in less detail in figure 9 above. Sheep Creek flows south in the figure 10 south center area and south of figure 10 turns to flow west as seen in figure 9 above. Belt Creek flows northeast from the Kings Hill Pass area to the figure 10 north edge and north of figure 10 flows northwest as seen in figure 9 above. Northeast-oriented Weatherway Creek and Cleveland Creek are in the Judith River drainage basin, which drains northeast to the east-oriented Missouri River. Headward erosion of Judith River tributaries into the present day Little Belt Mountains region captured southeast-oriented flow that had been moving to the actively eroding Musselshell River valley (and prior to that to the actively eroding Yellowstone River valley). The through valley at Kings Hill Pass was probably initiated by southeast-oriented flood flow, although as described in the figure 9 discussion it probably was also used by north-oriented flood flow when flood flow in the Belt Creek drainage basin was beheaded and reversed. The drainage divide was created when southeast-oriented flood flow in the Smith River drainage basin (including the Sheep Creek drainage basin) was beheaded and reversed. Flood flow reversals were probably greatly aided by Little Belt Mountains uplift (or at least emergence) as flood waters deeply eroded the Little Belt Mountains region. Why would a mountain region emerge as an immense flood was eroding the region? Emergence of the 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. Why would a mountain range be uplifted while an immense southeast-oriented flood was rapidly eroding the adjacent region? 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 mountain regions 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.

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.