Abstract:

This essay uses topographic map evidence to interpret landform origins in the Beaverhead County, Montana Tendoy Mountains between the north-northwest oriented Red Rock River and north oriented Medicine Lodge Creek. Medicine Lodge Creek flows along the Tendoy Mountains west flank while the Red Rock River flows along the Tendoy Mountains east flank with water in both drainage routes flowing to the north-northeast oriented Beaverhead River. A deep through valley links the north oriented Medicine Lodge Creek valley with the southeast oriented Cabin Creek valley with Cabin Creek flowing to southeast and north oriented Big Sheep Creek, which flows to the north-northwest oriented Red Rock River. Sourdough Creek and its southern extension Muddy Creek flow in a south-southeast direction between Medicine Lodge Creek and the Red Rock River to join north oriented Big Sheep Creek as a barbed tributary. The south-southeast oriented Sourdough Creek-Muddy Creek valley is linked by a through valley with the north of Medicine Lodge Creek valley. These major drainage routes combined with other evidence from secondary drainage routes including numerous through valleys crossing present day drainage divide and many barbed tributaries are remnants of what was once a large-scale complex of diverging and converging flood flow channels. Floodwaters were derived from a thick North American ice sheet’s western margin and were flowing from western Canada across western Montana to eastern Idaho and crossed the present day east-west continental divide in the Bannack Pass area, which is south of the study region (south-southeast oriented floodwaters on the present day north-northwest oriented Red Rock River alignment probably crossing the present day continental divide in the Monida Pass region, which south and east of the study region). Headward erosion of a deep south-southeast oriented flood flow channel on the present day Red Rock River beheaded a south oriented flood flow channel on the present day north oriented Big Sheep Creek alignment. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented Big Sheep Creek drainage route, which captured south and southeast oriented flood flow on the Sourdough Creek-Muddy Creek and Medicine Lodge Creek-Cabin Creek alignments. The deep Beaverhead River valley north of the region next beheaded south oriented flood flow to the south oriented Red Rock River and Medicine Lodge Creek flood flow channels. Floodwaters on the north ends of the beheaded flood flow reversed flow direction to create the north-northwest oriented Red Rock River and north oriented Medicine Lodge Creek drainage routes and the Medicine Lodge Creek-Cabin Creek drainage divide seen today. Flood flow reversals occurred as ice sheet related crustal warping raised mountain ranges and created topographic barriers to the south oriented melt water flood flow.

Preface

The following interpretation of detailed topographic map evidence is one of a series of essays describing similar evidence for all major drainage divides contained within the Missouri River drainage basin and for all major drainage divides with adjacent drainage basins. The research project is interpreting evidence in the context of a previously unexplored deep glacial erosion paradigm, which is fundamentally different from most commonly accepted North American glacial history interpretations. Project essays are listed on the sidebar category list under their appropriate Missouri River tributary drainage basin, Missouri River segment drainage basin (by state), and/or state in which the Missouri River drainage basin is located.

Introduction

The purpose of this essay is to use topographic map interpretation methods to explore the Red Rock River-Medicine Lodge Creek drainage divide area landform origins in the Tendoy Mountains in Beaverhead County, Montana and 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 a 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 Red Rock River-Medicine Lodge Creek drainage divide area landform evidence in the Tendoy Mountains in Beaverhead County, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Red Rock River-Medicine Lodge Creek drainage divide area location map

Figure 1: Red Rock River-Medicine Lodge 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 location map for the Red Rock River-Medicine Lodge Creek drainage divide in the Tendoy Mountains in Beaverhead County, Montana and illustrates in the east half a region in southwest Montana with Idaho west and south of Montana except in the south half of figure 1 where the western edge of Yellowstone National Park in the northwest corner of Wyoming can be seen along the east edge of figure 1. The Montana-Idaho border from near Lost Trail Pass (near northwest corner of figure 1) to near the Wyoming state line follows the east-west continental divide, which is located along the Beaverhead Mountains and Centennial Mountains crest ridge. The Red Rock River flows in a west direction north of the Centennial Mountains to near Lima, Montana where it turns to flow in a northwest direction and flows just east of the Tendoy Mountains to Clark Canyon Reservoir (not labeled in figure 1). At Clark Canyon Reservoir east oriented Horse Prairie Creek (not labeled in figure 1) joins the Red Rock River to form the north-northeast oriented Beaverhead River, which near Twin Bridges joins the south and northeast oriented Big Hole River to form the northeast and east oriented Jefferson River. North of figure 1 the Jefferson River joins the north oriented Madison and Gallatin Rivers (seen flowing on opposites side of the Madison Range in the east half of figure 1) to form the north oriented Missouri River, which eventually turns to flow in a northeast and east direction to enter North Dakota. Once in North Dakota the Missouri River turns again to flow in a southeast and south direction with water eventually reaching the Gulf of Mexico. The unlabeled north oriented stream west of the Tendoy Mountains, which flows to east oriented Horse Prairie Creek west of Clark Canyon Reservoir, is Medicine Lodge Creek. The Red Rock River-Medicine Lodge Creek drainage divide area investigated in this essay is located in the Tendoy Mountains east of north oriented Medicine Lodge Creek and west of the northwest oriented Red Rock River.

A brief look at the big picture erosion history is given here to assist in understanding discussions related to more detailed maps shown below. Large volumes of south and southeast oriented floodwaters once flowed across the region shown by figure 1, including across the present day continental divide from Montana into Idaho. Floodwaters were derived from the western margin of a rapidly melting thick North American ice sheet and were flowing in a south and southeast direction from southwest Alberta and southeast British Columbia to and across the figure 1 region. At that time the high mountain ranges and deep valleys and basins that exist today did not exist and floodwaters formed large anastomosing complexes of diverging and converging south oriented flood flow channels as they flowed freely across the region. The mountains ranges and basins emerged as crustal warping related to the presence of a huge continental ice sheet north and east of figure 1 generally raised the entire figure 1 region, which took place as floodwaters flowed across the region. In addition, deep flood water erosion of valleys and basins surrounding the rising mountain ranges contributed to the emergence of present day mountain ranges. North oriented rivers in figure 1 are generally flowing in valleys that originated as south oriented flood flow channels. The north oriented drainage system seen today formed during massive flood flow reversals that occurred as mountain ranges and high plateaus were uplifted by ice sheet related crustal warping. During these massive flood flow reversals south oriented flood flow along one route would be captured so as to flow in a north direction along an adjacent route. North and east of the present day east-west continental divide the reversed flood flow or north oriented flood flow was moving into space in a deep “hole” the melting ice sheet had previously occupied.

The northwest oriented Red Rock River valley located east of the Tendoy Mountains and the north oriented Medicine Lodge Creek valley located west of the Tendoy Mountains both originated as major south oriented flood flow channels. South oriented floodwaters on both routes at one time crossed the present day continental divide and then flowed in southeast and south-southeast directions across eastern Idaho where they were captured by headward erosion of the much deeper west and southwest oriented Snake River valley (south of figure 1). Today deep passes cross the continental divide on either side of Garfield Mountain. The western pass is Bannack Pass (not to be confused with Bannock Pass which is south of a north oriented Horse Prairie Creek segment seen further to the northwest) and is south of the Tendoy Mountains while the highway between Lima, Montana and Spencer, Idaho makes use of the eastern pass, which is known as Monida Pass. South of the Tendoy Mountains and of the present day continental divide are south-southeast oriented Birch Creek and an unlabeled southeast oriented stream south of Lima, Montana. The unlabeled southeast oriented stream is a different and southeast oriented Medicine Lodge Creek. Both Birch Creek and the Idaho Medicine Lodge Creek disappear as surface streams south of figure 1, but they are both headed toward the southwest oriented Snake River. The Snake River begins as a south oriented drainage route (Henrys Fork in the southeast corner of figure 1 is a south oriented Snake River tributary) and then turns to flow in a southwest and west direction south of figure 1 before turning again to flow in a north direction with water eventually reaching the west oriented Columbia River.

Detailed location map for Red Rock River-Medicine Lodge Creek drainage divide area

Figure 2: Detailed location map for Red Rock River-Medicine Lodge Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 2 provides a more detailed location map for the Red Rock River-Medicine Lodge Creek drainage divide area in the Tendoy Mountains in Beaverhead County, Montana and shows drainage routes not seen in figure 1. The Montana-Idaho state line follows the east-west continental divide, which follows the Beaverhead Mountains crest ridge in the west half of figure 2 from near Lemhi Pass (near northwest corner of figure 2) to the south edge of figure 2 (west of center). After dipping below the south edge of figure 2 the continental divide reenters figure 2 and extends in more of a west-to-east direction across the southeast quadrant of figure 2. Green shaded areas are National Forest lands, which generally are located in mountainous regions. Clark Canyon Reservoir is located near the north edge of figure 2 and the Red Rock River flows in a west and north-northwest direction from Lima Reservoir (in southeast quadrant of figure 2) to Clark Canyon Reservoir. The Tendoy Mountains are located south of Clark Canyon Reservoir and west of the north-northwest oriented Red Rock River segment. Medicine Lodge Creek is a north oriented drainage route west of the Tendoy Mountains and east of the Beaverhead Mountains and flows to east oriented Horse Prairie Creek just west of Clark Canyon Reservoir. Horse Prairie Creek originates west of Medicine Lodge Creek and flows in a northwest direction along the north side of the continental divide before turning to flow in a north direction (north of Bannock Pass) and then turns again to flow in an east direction to Clark Canyon Reservoir. Note how the northwest oriented Horse Prairie Creek headwaters are on the same alignment as a southeast oriented Medicine Lodge Creek tributary. Also note northwest oriented Medicine Lodge Creek tributaries originating in the Tendoy Mountains. South of the north oriented Medicine Lodge Creek headwaters is southeast oriented Cabin Creek, which is joined by north oriented Deadman Creek to form north and northeast oriented (Big) Sheep Creek, which flows to the north-northwest oriented Red Rock River. Muddy Creek is a south-southeast oriented stream joining north oriented (Big) Sheep Creek as a barbed tributary. Not shown in figure 2 is Bannack Pass, which crosses the continental divide south of where Cabin Creek joins north oriented (Big) Sheep Creek. Bannack Pass links the north oriented Deadman Creek and (Big) Sheep Creek valleys with the southeast oriented Divide Creek valley south of the continental divide. Divide Creek flows to the southeast oriented Medicine Lodge Creek south of figure 2. The barbed tributaries, elbows of capture, and abrupt drainage route direction changes provide evidence for the massive flood flow reversals described in the discussions of detailed maps seen below.

Medicine Lodge Creek-Sourdough Creek drainage divide area

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

Figure 3 provides a topographic map of the Medicine Lodge Creek-Sourdough Creek drainage divide area. The Red Rock River flows in a north-northwest direction near the northeast corner of figure 3. Medicine Lodge Creek flows in a north direction from near the southwest corner of figure 3 to the north edge of figure 3 (near northwest corner). Sourdough Cave in the Tendoy Mountains is located near the center of figure 3. Sourdough Creek originates between Sourdough Cave and Sourdough Point and flows in a south direction to the south center edge of figure 3.  South of figure 3 Sourdough Creek becomes south-southeast oriented Muddy Creek, which joins northeast oriented Big Sheep Creek, which then flows to the north-northwest oriented Red Rock River. Note how between Sourdough Point and Sourdough Cave a north-to-south oriented through valley links the south oriented Sourdough Creek valley with a north-west oriented valley draining to west oriented Rock Canyon, which drains to north oriented Medicine Lodge Creek. The map contour interval for figure 3 is 50 meters and the through valley floor elevation at the drainage divide is between 2450 and 2500 meters. Elevations on both sides of the through valley rise to more than 2800 meters suggesting the through valley is at least 300 meters deep. The through valley was eroded as a south oriented flood flow channel at a time when the Tendoy Mountains did not stand high above surrounding regions as they do today. At that time multiple diverging and converging south oriented flood flow channels were being eroded into a surface equivalent in elevation to the highest Tendoy Mountain elevations today, although the Tendoy Mountains may have been uplifted since. Other south oriented flood flow channels were located on the present day north oriented Red Rock River and Medicine Lodge Creek alignments. Evidence for still other flood flow channels can be found by studying other figure 3 drainage divides. For example, in the southwest quadrant of figure 3 the South Fork Kate Creek flows in a north direction east of Ellis Peak and to join north-northwest oriented Kate Creek, which then joins to north-oriented Medicine Lodge Creek. South of the South Fork Kate Creek headwaters are headwaters of southeast, south, southwest, and northeast oriented Law Creek, which joins north oriented Medicine Lodge Creek near the southwest corner of figure 3 (better seen in figures 5 and 6). A north-to-south oriented through valley between Ellis Peak and Graphite Mountain links the opposing drainage routes. The through valley floor elevation is also between 2450 and 2500 meters and Ellis Peak rises to 2958 meters while Graphite Mountain rises to 2865 meters suggesting the through valley is approximately 350 meters deep. The through valley provides evidence of a diverging and converging flood flow channel.

Detailed map of Medicine Lodge Creek-Sourdough Creek drainage divide area

Figure 4: Detailed map of Medicine Lodge Creek-Sourdough Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 provides a detailed topographic map of the Medicine Lodge Creek-Sourdough Creek drainage divide area seen is less detail in figure 3. Sourdough Point is located in section 23 and Sourdough Creek flows in a south-southeast direction in section 24 (east of Sourdough Point) to the south edge of figure 4 (east of center) with water eventually making an abrupt turn to flow to the north-northwest oriented Red Rock River east of figure 4. North of Sourdough Point is a north-northwest oriented valley draining to the north edge of figure 4 (west half) with water then turning to flow in west direction to north oriented Medicine Lodge Creek west of figure 4. Near the corner of section 13, 14, 23, and 24 a through valley links the north-northwest oriented valley with the south-southeast oriented Sourdough Creek valley. The map contour interval for figure 4 is 40 feet and the through valley floor elevation at the drainage divide is between 8120 and 8160 feet. West of Sourdough Point the high point in the northeast corner of section 22 is greater than 9280 feet. In section 7 near the northeast corner of figure 4 there is high point shown with an elevation of 9380 feet. These elevations suggest the through valley is approximately 1100 feet deep. The through valley, as discussed in the figure 3 discussion, was eroded by a south oriented flood flow channel, which was eroded into a surface as high as the highest elevations in figure 4 today. Headward erosion of a deeper west oriented flood flow channel from a deeper south oriented flood flow channel on the present day north oriented Medicine Lodge Creek alignment eventually beheaded and reversed the south oriented flood flow channel seen here in figure 4. Floodwaters on the north-northwest end of the beheaded flood flow channel reversed flow direction to create the north-northwest oriented drainage route seen today. The reversed flood flow may have captured significant flood flow from adjacent yet to be beheaded south oriented flood flow channels. Such captured flood water probably helped erode the deep north-northwest oriented valley.

Kate Creek-Medicine Lodge Creek drainage divide area

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

Figure 5 illustrates the Kate Creek-Medicine Lodge Creek drainage divide area south of figure 3 and includes a significant overlap area with figure 3. The north-northwest oriented Red Rock River can just barely be seen in the northeast corner of figure 5. Sourdough Creek originates just east of Sourdough Point (near north center edge of figure 5) and flows in a south direction to become south-southeast oriented Muddy Creek, which south of figure 5 joins northeast oriented Big Sheep Creek, which can be seen flowing across the southeast corner of figure 5. Medicine Lodge Creek originates near the south edge of figure 5 (west half) and flows in a north-northwest and north direction to the north edge of figure 5 (west half). The South Fork Kate Creek flows in a north direction east of Ellis Peak (in northwest quadrant of figure 5) and flows to north-northwest oriented Kate Creek, which joins north oriented Medicine Lodge Creek north of figure 5. South of the north oriented South Fork Kate Creek valley is the south and southwest oriented Law Creek valley. Note how Law Creek flows to the north oriented Medicine Lodge Creek as a barbed tributary. A deep through valley described in the figure 3 discussion links the north oriented South Fork Kate Creek valley with the south oriented Law Creek valley. Valleys on the present day north oriented Medicine Lodge Creek alignment and the Kate Creek-South Fork Kate Creek-Law Creek alignment were initiated by diverging and converging south oriented flood flow channels. Note other barbed tributaries in figure 5 providing additional evidence of south oriented flood flow channels prior to the reversals of flood flow in the present day north oriented Medicine Lodge Creek valley. Note also how the Sourdough Creek-Muddy Creek valley is oriented in a south direction while on either side are deeper north oriented valleys. The Sourdough Creek-Muddy Creek valley drainage was not reversed while drainage in the deeper valleys to the west and east was reversed. The flood flow reversals in the deeper valleys probably occurred because the south oriented flood flow channels in those valleys were beheaded by headward erosion of much deeper valleys further to the north. The south oriented flood flow channel on the Sourdough Creek-Muddy Creek alignment had not eroded its deep south oriented valley far enough north so that when it was beheaded and reversed as seen in figures 3 and 4 the reversal of flood flow on the north end of the valley was not able to capture south oriented flood flow from the deeper valley seen in figure 5 further to the south.

Detailed map of South Fork Kate Creek-Law Creek drainage divide area

Figure 6: Detailed map of South Fork Kate Creek-Law Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 provides a detailed topographic map of the South Fork Kate Creek-Law Creek drainage divide area seen in less detail in figures 3 and 5. The map contour interval for figure 6 is 40 feet. Ellis Peak is located in section 36 near the northwest corner of figure 6 and reaches an elevation of 9698 feet. Graphite Mountain is located near the north edge of section 10 north of the southeast corner of figure 6 and reaches an elevation of 9401 feet. The South Fork Kate Creek originates in section 6 south of Ellis Peak and flows in a southeast direction before making a U-turn to flow in a north-northeast direction to the north center edge of figure 6. North of figure 6 the South Fork flows to north-northwest oriented Kate Creek, which then flows to north oriented Medicine Lodge Creek. Law Creek originates in section 1 and flows in a southeast direction across the southwest corner of section 6 and then flows in a south and southwest direction to the south edge of figure 6. South of figure 6 Law Creek makes a U-turn to flow in a northeast direction across the southwest corner of figure 6 and then joins north oriented Medicine Lodge Creek. Note how in the region near the southeast corner of section 6 a deep through valley links the north oriented South Fork Kate Creek valley with the south oriented Law Creek valley. The through valley floor elevation at the drainage divide is between 8080 and 8120 feet suggesting the through valley is at approximately 1300 feet. A second and slightly higher through valley can be seen in the northwest quadrant of section 8 to the southeast and provides evidence of multiple south oriented flood flow channels. The southeast oriented South Fork Kate Creek valley alignment was established by south oriented flood that once moved to what was then the actively eroding Law Creek valley, which was probably eroding headward from what was then a south oriented flood flow channel on the present day north oriented Medicine Lodge Creek alignment. Evidence for through valleys crossing other drainage divides in figure 6 can be seen. These through valleys provide evidence of multiple diverging and converging flood flow channels that were probably being beheaded and reversed as deep valleys eroded headward into the region to capture what had begun as south oriented flood flow, but which was systematically being beheaded and reversed to create the north oriented drainage system seen today. The flood flow reversals were probably  aided by crustal warping that was raising the Tendoy Mountains and perhaps the entire region as floodwaters flowed across the region.

Medicine Lodge Creek-Cabin Creek drainage divide area

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

Figure 7 illustrates the Medicine Lodge Creek-Cabin Creek drainage divide area south of figure 5 and includes an overlap area with figure 5.  The east-west continental divide is located along the Beaverhead Mountains crest ridge and is shown with a dashed line near the west edge of figure 7. Muddy Creek flows in a south-southeast direction from the north edge of figure 7 (east half) and joins north and northeast oriented Big Sheep Creek near the east edge of figure 7 (south of center). East of figure 7 northeast oriented Big Sheep Creek joins north-northwest the Red Rock River, which eventually flows to the north-northeast oriented Beaverhead River. Medicine Lodge Creek flows in north-northwest direction in the northwest quadrant of figure 7 and north of figure 7 flows in a north direction to eventually flow to the north-northeast oriented Beaverhead River. Cabin Creek originates near the east-west continental divide and flows in an east-southeast and southeast direction to the south edge of figure 7 (east of center). South of figure 7 Cabin Creek joins north oriented streams to form north and northeast oriented Big Sheep Creek, which is seen flowing from the southeast corner of figure 7. Note the deep north-to-south oriented through valley between the Beaverhead Mountains to the west and the Tendoy Mountains to the east linking the north oriented Medicine Lodge Creek valley with the southeast oriented Cabin Creek valley. The map contour interval for figure 7 is 50 meters in the east and 40 meters in the west and the through valley floor elevation at the drainage divide is between 2400 and 2450 meters. Sourdough Peak in the Tendoy Mountains rises to 2917 meters and elevations greater than 3000 meters are found in the Beaverhead Mountains suggesting the through valley may be as much 450 meters deep. South and east of figure 7 is Bannack Pass, which crosses the east-west continental divide, and south of Bannack Pass is a south-southeast oriented drainage route. Bannack Pass is not seen in this essay, but can be seen in figure 10 of the Medicine Lodge Creek-Lemhi River drainage divide area landform origins along the continental divide essay. The north oriented Medicine Lodge Creek valley forms the north end of a dismembered flood flow channel that once moved floodwaters into eastern Idaho. The flood flow channel was first dismembered when south oriented flood flow on the present day north oriented Big Sheep Creek alignment reversed flow direction and captured southeast oriented flood flow on the Cabin Creek alignment. Next the flood flow channel was beheaded north of this essay’s study region and floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented Medicine Lodge Creek drainage route and also to create the Medicine Lodge Creek-Cabin Creek drainage divide.

Detailed map of Medicine Lodge Creek-Cabin Creek drainage divide area

Figure 8: Detailed map of Medicine Lodge Creek-Cabin Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 provides a detailed topographic map of the Medicine Lodge Creek-Cabin Creek drainage divide area seen in less detail in figure 7. The Beaverhead Mountains are located along the west edge of figure 8 while the Tendoy Mountains are located along the east edge of figure 8. Medicine Lodge Creek flows in a north-northwest direction to the north edge of figure 8 (west of center). Note south and west oriented Bear Canyon in sections 28 and 29 which drains to north oriented Medicine Lodge Creek as a barbed tributary and which provides evidence of former south oriented flood flow channels that once crossed the Tendoy Mountains. Cabin Creek originates near the west edge of figure 8 (south half) and flows in an east-southeast direction across section 2 to section 9 where it turns to flow in a south-southeast direction to the south edge of figure 8 (east half). A major north-to-south oriented through valley links the north-northwest oriented Medicine Lodge Creek valley with the south-southeast oriented Cabin Creek valley and a road is located in the through valley. The map contour interval for figure 8 is 40 feet and elevation where the road crosses the drainage divide is between 7880 and 7920 feet. Elevations in the Tendoy Mountains (north of figure 8) rise to 9871 feet while elevations in the Beaverhead Mountains (west of figure 8) rise to 10,773 feet suggesting the through valley may be as much as 2000 feet deep. While the through valley is probably a structural feature it is also a water-eroded feature and was eroded as a south-southeast oriented flood flow channel. Floodwaters were flowing across the region and then into eastern Idaho where they were captured by Snake River valley headward erosion. To reach eastern Idaho from the figure 8 location floodwaters had to cross the present day east-west continental divide. Evidence of such a crossing is found at Bannack Pass, which today crosses the continental divide in a south-southeast direction from the through valley seen in figure 8. The south-southeast oriented flood flow channel was dismembered as described in the figure 7 discussion when south oriented flood flow on the present day north oriented Big Sheep Creek alignment (east of figure 8) was beheaded and the floodwaters on the north end of that beheaded flood flow channel reversed flow direction and captured the south and southeast oriented flood flow on the Medicine Lodge Creek and Cabin Creek alignment seen in figure 8. Next south oriented flood flow on the Medicine Lodge Creek-Cabin Creek alignment was beheaded north of figure 8 and floodwaters on the north end of that beheaded flood flow channel reversed flow direction to create the north oriented Medicine Lodge Creek drainage system and Medicine Lodge Creek-Cabin Creek drainage divide. Crustal warping that raised the Beaverhead and Tendoy Mountains probably greatly aided the flood flow reversals.

Big Sheep Creek-Little Sheep Creek drainage divide area

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

Figure 9 illustrates the Big Sheep Creek-Little Sheep Creek drainage divide area east and slightly south of figure 7 and includes an overlap area with figure 7. The northwest oriented Red Rock River is just barely seen next to the highway in the northeast corner of figure 9. Cabin Creek flows in southeast direction from the west center edge of figure 9 and after joining several northeast and north oriented streams makes an abrupt turn to become north and northeast oriented Big Sheep Creek, which flows to the north center edge of figure 9 and then joins the Red Rock River north of figure 9. The southeast oriented stream flowing from the north edge of figure 9 (west half) to join Big Sheep Creek as a barbed tributary at the point where Big Sheep Creek changes from flowing in a north direction to flowing in a northeast direction is Muddy Creek, which has been seen in earlier figures. Big Sheep Creek has eroded deep water gaps across Tendoy Mountain ridges, one of which is seen in detail in figure 10 below. The northeast and north-northwest oriented stream in the east half of figure 9 is Little Sheep Creek, which is formed at the confluence of its northwest oriented East Fork and its north-northeast oriented West Fork. Gallagher Gulch is a southeast oriented valley draining to the West Fork Little Sheep Creek as a barbed tributary and is linked by a through valley with northwest oriented Shearing Pan Gulch, which drains to north oriented Big Sheep Creek. The map contour interval for figure 9 is 50 meters and the through valley floor elevation is given as 2412 meters. Elevations the south of the through valley rise to more than 2550 meters while elevations to the north rise to more than 2800 meters suggesting the through valley is at least 140 meters deep. Straight Creek is a southeast oriented stream flowing to Little Sheep Creek as a barbed tributary and is aligned with northwest oriented Deadwood Gulch, which drains to Big Sheep Creek. A northwest-to-southeast oriented through valley links the Deadwood Gulch valley with the Straight Creek valley providing evidence of an additional southeast oriented flood flow channel. These southeast oriented flood flow channels across the present day Big Sheep Creek-Little Sheep Creek drainage divide were first captured by headward erosion of a deep south-southwest and southwest oriented flood flow channel on the present day north oriented West Fork and Little Sheep Creek alignment. That flood flow channel eroded headward from the present day location of Bannack Pass, which is located near the West Fork Little Sheep Creek headwaters. Next headward erosion of a deep south oriented flood flow channel on the present day Big Sheep Creek-Deadman Creek alignment (also from the Bannack Pass area) captured the southeast oriented flood flow and beheaded the southeast oriented flood flow channels to the newly eroded south oriented Little Sheep Creek flood flow channel. Floodwaters on northwest ends of the beheaded flood flow channels reversed flow direction to erode the northwest oriented Deadwood Gulch and Shearing Pan Gulch valleys. Next headward erosion of a still deeper southeast oriented flood flow channel on the present day northwest oriented Red Rock River alignment beheaded the south oriented flood flow channels on the Little Sheep Creek and Big Sheep Creek alignments. Floodwaters on the north ends of the beheaded flood flow reversed flow direction to create the north oriented Little Sheep Creek and Big Sheep Creek drainage routes. Finally headward erosion of still deeper valleys north of this essay’s study area beheaded the southeast oriented flood flow channel on the Red Rock River alignment. Floodwaters on the northwest end of the beheaded flood flow channel reversed flow direction to create the northwest oriented Red Rock River.

Detailed map of Cabin Creek-Big Sheep Creek drainage divide area

Figure 10: Detailed map of Cabin Creek-Big Sheep Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 provides a detailed topographic map of the Cabin Creek-Big Sheep Creek drainage divide area seen in less detail in figure 9. Cabin Creek flows in an east-southeast direction from the west edge of figure 10 (near northwest corner) to join east oriented Meadow Creek and a north oriented stream near the south edge of section 4 and forms Big Sheep Creek, which then flows in a southeast and east direction to near the east edge of section 10 where it turns to flow in a north direction to the north edge of figure 10 (east of center). Deadman Creek is the north oriented stream flowing from the south center edge of figure 10 to join Big Sheep Creek in section 10. Four Eyes Canyon is a north-northwest oriented valley draining from near the southeast corner of figure 10 to north oriented Big Sheep Creek. The Big Sheep Creek elbow of capture in section 10 is remarkable because it occurs in the middle of a deep water gap. The map contour interval for figure 10 is 40 feet. Big Sheep Creek crosses the 6720-foot contour line in the water gap. Elevations directly to the north rise to 8026 feet while elevations directly to the south rise to 7909 feet suggesting the water gap is approximately 1200 feet deep. The deep water gap provides evidence of the amount of erosion that occurred as floodwaters flowed across the region. To create the water gap floodwaters at one time must have been flowing on a surface at least as high the highest points in figure 10 (although the region may have been uplifted since). At that time a southeast oriented flood flow channel on the Cabin Creek alignment converged with a south oriented flow channel on the present day north oriented Deadman Creek-Big Sheep Creek alignment. Also at that time a south oriented flood flow channel diverged from the southeast oriented Cabin Creek flood flow channel near the point where Cabin Creek joins Meadow Creek to form the southeast oriented Big Sheep Creek segment today. Floodwaters were flowing to the present day Bannack Pass region (south of figure 10) and then into eastern Idaho. These converging and diverging flood flow channels began to erode deep south-oriented valleys into what were then emerging Tendoy Mountain ridges. Headward erosion of the deep southeast oriented Cabin Creek valley beheaded the unnamed south oriented flood flow channel in section 9, which caused floodwaters on the north end of the beheaded flood flow to reverse flow direction and to create a north oriented tributary valley. Next headward erosion of the much deeper Red Rock River valley north of figure 10 beheaded the south oriented flood flow channel on the Big Sheep Creek-Deadman Creek alignment. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented Big Sheep Creek and Deadman Creek drainage route seen today. Headward erosion of a deeper north-oriented valley along this newly formed north oriented drainage system captured the southeast oriented flood flow moving on the Cabin Creek alignment, which resulted in the figure 10 drainage pattern seen today.

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.