Beaverhead River-Red Rock River drainage divide area landform origins Beaverhead County, Blacktail Mountains, Montana, USA

Authors


Abstract:

This essay uses topographic map evidence to interpret landform origins between the Beaverhead River and the Red Rock River in Beaverhead County, Montana. The Red Rock River flows in a west and north-northwest direction to the north-northeast oriented Beaverhead River. The Blacktail Mountains are an upland region located between the north-northwest oriented Red Rock River and Blacktail Deer Creek, a north-northwest oriented Beaverhead River tributary located north and east of the north-northwest oriented Red Rock River segment. The Blacktail Mountains northwest flank is drained by relatively short Beaverhead River tributaries including northwest oriented Clark Canyon while much of the Blacktail Mountains upland region drains to southeast, south, west, and northwest oriented Sage Creek, which flows to the north-northeast Red Rock River. Barbed tributaries and through valleys crossing drainage divides are common in the Blacktail Mountains region and provide evidence of southeast and south oriented flood flow channels that preceded the present day north oriented drainage system. Floodwaters are interpreted to have been derived from the western margin of a melting North American ice sheet and were flowing from western Canada across Montana to and across the study region. At that time Montana mountain ranges did not exist and floodwaters flowed freely across western Montana. Mountain ranges emerged as ice sheet related crustal warping raised mountain masses and as floodwaters eroded deep valleys into and around the rising mountain masses. The north oriented Red Rock River, Beaverhead River, and Blacktail Deer Creek drainage routes originated as south oriented flood flow channels, which beheaded southeast and south oriented flood flow channels crossing the Blacktail Mountains. Floodwaters on north and northwest ends of the beheaded flood flow channels reversed flow direction to create north and northwest oriented Beaverhead River and Blacktail Deer Creek tributary drainage routes. Headward erosion of a deep northeast oriented valley from space in the deep “hole” the melting ice sheet occupied and which was being opened up by the ice sheet melting next beheaded south oriented flood flow channels supplying floodwaters to the south-southwest and south-southeast oriented flood flow channel on the present day north oriented Beaverhead and Red Rock River alignment. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the present day Red Rock River-Beaverhead River drainage system.

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 Beaverhead River-Red Rock River drainage divide area landform origins 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 Beaverhead River-Red Rock River drainage divide area landform evidence in Beaverhead County, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Beaverhead River-Red Rock River drainage divide area location map

Figure 1: Beaverhead River-Red Rock 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 Beaverhead River-Red Rock River drainage divide in Beaverhead County, Montana and illustrates in the north a region in southwest and south central Montana with Yellowstone National Park in the northwest corner of Wyoming in the southeast quadrant of figure 1 and an area in eastern Idaho located west of Yellowstone National Park. The Montana-Idaho state line west of Yellowstone National Park follows the east-west continental divide, which is located on the crest of the Beaverhead and Centennial Mountains from the west edge of figure 1 to the Wyoming state line. Upper Red Rock Lake is located north of the Centennial Mountains and drains in a west direction to Lower Red Rock Lake and then to the Red Rock River, which flows in a west direction to Lima, Montana where it turns to flow in a north-northwest direction to join the north-northeast-oriented Beaverhead River. The Beaverhead River joins the north, southeast, south, and northeast oriented Big Hole River near Twin Bridges, Montana to form the north-northeast, east, and northeast oriented Jefferson River. The Jefferson River flows to Three Forks, Montana where it joins the north oriented Madison and Gallatin Rivers to form the north and north-northwest oriented Missouri River. Blacktail Deer Creek is the north-northwest stream joining the Beaverhead River near Dillon, Montana.  The Beaverhead River-Red Rock River drainage divide area investigated in this essay is located west and south of Blacktail Deer Creek, east and south of the Beaverhead River, and north and east of the Red Rock River.

A brief look at the big picture erosion history will help understand discussions related to detailed maps shown below. Large volumes of south and southeast oriented floodwaters once flowed across the region shown by figure 1. Floodwaters were derived from the western margin of a 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. North oriented rivers in figure 1, including the north-northwest oriented Red Rock River and Blacktail Deer Creek and the north-northeast oriented Beaverhead and Jefferson Rivers are generally flowing in valleys that originated as south oriented flood flow channels. The west oriented Red Rock River alignment was at one time used by an east oriented flood flow channel. When floodwaters first flowed across the region the mountain ranges, deep river valleys, and basins between the mountains did not exist and floodwaters could freely flow in south and southeast directions across the region. Mountain ranges emerged as floodwaters flowed across the region and initially floodwaters flowed across what are today high mountain ranges including mountain ranges, which today form the east-west continental divide. Over time the more successful, or deeper, flood flow channels captured floodwaters from adjacent less successful flood flow channels and floodwaters became concentrated along major flood flow routes. North-to-south oriented through valleys eroded across the present-day east-west continental divide by south and southeast oriented flood flow channels are today preserved as mountain passes. South-southeast oriented flood flow between Blacktail Deer Creek the north-northwest oriented Red Rock River was beheaded prior to the reversal of flood flow on the Red Rock River and Blacktail Deer Creek alignments.

The present day north-northwest oriented Blacktail Deer Creek and the north-northwest oriented Red Rock River segment originated as a south oriented flood flow channels, which were subsequently reversed to form the north oriented drainage route seen today. The flood flow reversal was probably indirectly caused by crustal warping that occurred as melt water floods flowed across the region with the crustal warping being related to the thick ice sheet presence north and east of figure 1, although the direct cause was headward erosion of a deep northeast oriented valley across Montana (north of figure 1), which beheaded south oriented flood flow channels supplying floodwaters to a south oriented flood flow channel on the present-day north oriented Missouri River alignment. At Three Forks, Montana this south oriented flood flow channel split into several diverging south oriented flood flow channels. The deep northeast oriented valley (now northeast oriented Missouri River valley north of figure 1) was eroding headward from space in the deep “hole” the melting ice sheet had occupied and that was being opened by ice sheet melting and was capturing the south and southeast oriented ice-marginal melt water floods and diverting the captured floodwaters into space in the deep “hole” where the melting the ice sheet had been located. This northeast oriented valley was much deeper than the beheaded south oriented flood flow channels and floodwaters on north ends of the beheaded flood flow channels reversed flow direction to create the north oriented Missouri River drainage route seen north of Three Forks in figure 1.The reversal of flow in the Missouri River flood flow channel also reversed flood flow in flood flow channels on the Gallatin and Madison River alignments to create the north oriented Madison and Gallatin River drainage routes seen today. Headward erosion of the deep northeast and east Jefferson River valley from this reversed Missouri River flood flow channel next beheaded flood flow channels further to the west and floodwaters on north ends of those beheaded flood flow channels reversed flow direction to create north oriented drainage routes, including the north-northeast oriented Beaverhead and Jefferson Rivers and the north-northwest oriented Red Rock River (which then reversed the east oriented flood flow north of the Centennial Mountains to create the west oriented Red Rock River headwaters segment seen in figure 1).

Detailed location map for Beaverhead River-Red Rock River drainage divide area

Figure 2: Detailed location map Beaverhead River-Red Rock River 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 Beaverhead River-Red Rock River drainage divide area in Beaverhead County, Montana and shows drainage routes not seen in figure 1. Green shaded areas are National Forest lands, which generally are located in mountainous regions. The continental divide serves as the Montana-Idaho state line and follows the crest of the Beaverhead Mountains in the southwest corner of figure 2 and then follows the crest of the west-to-east oriented Centennial Mountains near the south edge of figure 2. All areas in Idaho drain to the Snake River with water eventually reaching the Pacific Ocean. Upper and Lower Red Rock Lakes are located north of the Centennial Mountains in the southeast corner of figure 2. The Red Rock River originates at Lower Red Rock Lake and flows in a west direction in the Centennial Valley to Lima, Montana where it turns to flow in a north-northwest direction to Clark Canyon Reservoir where it joins other streams to form the north-northeast Beaverhead River, which north of figure 2 joins the Big Hole River and Ruby River to form the north-northeast, east, and northeast oriented Jefferson River. Northwest and north-northwest oriented Blacktail Deer Creek originates north of the Centennial Valley and has an East Fork, Middle Fork, and West Fork. East Fork headwaters at the south end of the Snowcrest Range are oriented in a southwest direction and then make a U-turn to flow in a northwest direction. The West Fork originates near Antone Peak and flows in a west and southwest direction before making a U-turn to flow in a north-northwest direction. Between north-northwest oriented Blacktail Deer Creek and the north-northwest oriented Red Rock River segment is southeast and south oriented Sage Creek, which also makes a large U-turn to flow in a west and northwest direction to join the north-northwest oriented Red Rock River. Basin Creek is northwest tributary to the south oriented Sage Creek segment. Note  the unnamed northwest oriented stream joining the north-northeast oriented Beaverhead River near Clark Canyon Reservoir and the unnamed south oriented tributary to the northwest oriented Sage Creek segment (just before Sage Creek joins the north-northwest oriented Red Rock River). The barbed tributaries and U-turns seen in the Blacktail Deer Creek-Red Rock River drainage divide area provide evidence of flood flow reversals that created the present day north oriented drainage routes. North and northwest oriented drainage routes seen in figure 2 generally are located on alignments of former south and southeast oriented flood flow channels. The south and southeast oriented flood flow channels were systematically beheaded by headward erosion of much deeper valleys and floodwaters on north and northwest ends of the beheaded flood flow channels reversed flow direction to create the north and northwest oriented drainage routes seen today. Flood flow channels were beheaded one channel at a time and usually from east to west. These systematic flood flow reversals were greatly aided by ice sheet related crustal warping that raised the regional mountain ranges as immense south and southeast oriented melt water floods flowed across the region.

Clark Canyon-Divide Creek drainage divide area

Figure 3: Clark Canyon-Divide 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 Clark Canyon-Divide Creek drainage divide area. In the southwest corner of figure 3 the Red Rock River flows in a north direction to Clark Canyon Reservoir. The north-northeast river flowing from Clark Canyon Reservoir to the north edge of figure 3 is the Beaverhead River. Blacktail Deer Creek can just barely be seen flowing in a northwest direction across the northeast corner of figure 3. Between Clark Canyon Reservoir and Blacktail Deer Creek are the Blacktail Mountains. Northwest oriented Beaverhead River tributaries, which include Clark Canyon, Henneberry Gulch, and Gallagher Creek, originate along the Blacktail Mountains northwest flank. Maurer Creek originates just south of Poison Gulch and Whisky Draw (the Clark Canyon headwaters) before turning to flow in a south and west direction to Clark Canyon Reservoir. Divide Creek is the labeled southeast oriented stream located directly to the southeast from northwest oriented Clark Canyon. The unlabeled southeast oriented stream south and west of Divide Creek is Sage Creek, which flows to the south center edge of figure 3 and which is seen better in figure 5. South of figure 3 Divide Creek joins Sage Creek, which then makes a U-turn to flow to the north-northwest oriented Red Rock River. North of Divide Creek is east and north oriented Sheep Creek, which near the north edge of figure 3 turns to flow in a northeast direction to join northwest oriented Blacktail Deer Creek. North and northeast oriented West Fork Sheep Creek is located west of Sheep Creek. While it is subtle a shallow northwest-to-southeast oriented through valley can be seen on the uplifted Blacktail Mountains’ northwest edge. The map contour interval for figure 3 is 50 meters and two high points can be seen on the Blacktail Mountains northwest edge. The first high point is located at the Radio Facility south of the northwest oriented Maurer Creek and the north-northwest oriented Whisky Draw headwaters and reaches 2816 meters. The second high area is located near the words “Blacktail Mountains” in the northeast corner of figure 3 and reaches 2796 meters (further south near the east center edge another high area reaches 2889 meters). Elevations along the ridge between the first and second high points drop to less than 2600 meters on the drainage divide between northwest oriented Poison Gulch and the east oriented Sheep Creek headwaters. These lower elevations suggest large volumes of southeast oriented flood flow once moved across the Blacktail Mountains to the southeast oriented Divide Creek and Sage Creek valleys. South oriented flood flow also moved to the southeast oriented Sage Creek valley on the present day north oriented Sheep Creek and West Fork Sheep Creek alignments. The south oriented flood flow was beheaded and reversed by headward erosion of a much deeper southeast oriented flood flow channel on the present day northwest oriented Blacktail Deer Creek alignment. Headward erosion of the deeper north oriented Sheep Creek valley captured some of the southeast oriented flood flow before a much deeper valley on the present day north-northeast oriented Beaverhead River alignment beheaded the southeast oriented flood flow and diverted floodwaters in a south-southeast direction on the present day north-northwest oriented Red Rock River alignment. Floodwaters on northwest ends of the beheaded southeast oriented flood flow channels reversed flow direction to create the northwest oriented drainage routes flowing to the Beaverhead River today. Ice sheet related crustal warping that raised the Blacktail Mountains probably contributed to these flood flow reversals and the emergence of the Blacktail Mountains as a high mountain mass.

Detailed map of Poison Gulch-Divide Creek drainage divide area

Figure 4: Detailed map of Poison Gulch-Divide 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 Poison Gulch-Divide Creek drainage divide area seen is less detail in figure 3. North-northwest oriented Whisky Draw and northwest oriented Poison Gulch meet near the northwest corner of figure 4 and then drain to northwest oriented Clark Canyon. The north-northwest oriented stream in section 10 (near north center edge of figure 4) is the headwaters of Clark Canyon, which is oriented in a west direction (north of figure 4) until northwest oriented Poison Gulch joins it. Divide Creek flows in an east and southeast direction across sections 21, 22, and 23 to the southeast corner of figure 4. The southeast oriented stream flowing across the southwest corner of section 21 is Sage Creek and the northwest oriented stream originating in the northwest quadrant of section 20 and flowing to the west center edge of figure 4 is Maurer Creek. The map contour interval for figure 4 is 40 feet. Note how the northwest oriented Maurer Creek valley is linked by a through valley in section 20 with the southeast oriented Sage Creek valley. The through valley floor elevation at the drainage divide is 8891 feet. The high point near the south edge of section 17 rises to more than 9000 feet and even higher elevations can be found in the southwest quadrant of section 20 suggesting the through valley is approximately 110 feet deep. In the south half of section 16 another through valley links the northwest oriented Poison Gulch valley with the east and southeast oriented Divide Creek valley. This second through valley is defined by only two contours on the east so based on adjacent elevations may be less than 80 feet deep. A much deeper through valley in the south half of section 10 links the north-northwest oriented Clark Canyon headwaters valley with the east oriented Sheep Creek headwaters valley. This deeper through valley has an elevation of 8381 feet at the drainage divide. The high point in section 10 to the north is 8667 feet and elevations higher than 8800 feet can be seen in section 16 to the southwest suggesting this through valley is at least 280 feet deep. Not seen in figure 4 is the high point at the Radio Facility, which is south of section 20 (south of southwest corner of figure 4) and which reaches 9240 feet. Also not seen in figure 4 is the high point north and east of the northeast corner of figure 4, which reaches an elevation of 9477 feet. These much higher elevations suggest the previously described through valleys (and others like them) are merely channels eroded into the floor of what was once a much broader northwest-to-southeast oriented valley. These former southeast-oriented valleys provide evidence of southeast oriented flood flow that once moved across the high Blacktail Mountains at a time when the Blacktail Mountains did not stand high above the Beaverhead River valley to the northwest.

Red Rock River-Sage Creek drainage divide area

Figure 5: Red Rock River-Sage Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Red Rock River-Sage Creek drainage divide area south and east of figure 3 and does not include an overlap area with figure 3. The Red Rock River flows in a north-northwest direction from the south edge of figure 5 (west half) to the northwest corner of figure 5. Sage Creek flows in a south direction from the north edge of figure 5 (east of center) and then south of center in figure 5 Sage Creek turns to flow in a west and northwest direction to the north-northwest oriented Red Rock River. Note the multiple barbed tributaries seen in figure 5. For example, in addition to south oriented Sage Creek Ashbough Creek and Little Ashbough Creek flow in south-southwest directions to join the north-northwest oriented Red Rock River. Big Spring Gulch drains in a south direction and Spring Gulch drains in a southeast direction to join south and west oriented Sage Creek, which then turns in a northwest direction to join the north-northwest oriented Red Rock River. These multiple south oriented streams originating in an upland region in what is today a north oriented drainage basin provide evidence the entire region was once crossed by multiple south and southeast oriented flood flow channels and that the present day north-northwest oriented Red Rock River valley was at one time a south-southeast oriented flood flow channel. Note also northwest oriented tributaries to south and west oriented Sage Creek, which provide evidence of reversed drainage on what originated as southeast oriented flood flow channels. Basin Creek flows in a northwest direction from the east edge of figure 5 (south half) to join south oriented Sage Creek. An unnamed northwest oriented tributary further to the west joins Sage Creek at the point where it turns from flowing in a south direction to flowing in a west direction. Note how that unnamed Sage Creek tributary is linked by a northwest-to-southeast oriented through valley with a southeast oriented stream in the region named Antelope Flat (in southeast quadrant of figure 5). The map contour interval for figure 5 is 50 meters and the through valley floor elevation at the drainage divide is between 2000 and 2050 meters. Elevations to the west rise to 2211 meters and to the east elevations rise to 2428 meters suggesting the through valley is at least 160 meters deep. The through valley provides still further evidence of a southeast oriented flood channel moving floodwaters from the present day Sage Creek drainage basin to the Antelope Flat valley, which today drains to the west oriented Red Rock River south of figure 5.

Detailed map of Sage Creek-Antelope Flat drainage divide area

Figure 6: Detailed map of Sage Creek-Antelope Flat 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 Sage Creek-Antelope Flat drainage divide area seen in less detail in figure 5. Sage Creek flows in a south and west direction near the northwest corner of figure 6. Note how a northwest oriented tributary joins Sage Creek in section 3. Basin Creek flows in a north-northwest direction across the northeast corner of figure 3 and joins south oriented Sage Creek as a barbed tributary north of figure 6. Antelope Flat is labeled and drains in a south-southeast direction to the south edge of figure 6 (east of center). In the west half of section 13 a northwest-to-southeast oriented through valley links the unnamed northwest oriented Sage Creek tributary valley with the south-southeast oriented Antelope Flat valley. The map contour interval for figure 6 is 20 feet and the through valley floor elevation at the drainage divide is 6572 feet. Elevations in section 15 to the west rise to 7216 feet while elevations in section 19 east of Antelope Flat rise to 7283 suggesting the through valley is at least 640 feet deep. The through valley was eroded as a southeast oriented flood flow channel prior to headward erosion of the west oriented Sage Creek valley, which beheaded the southeast oriented flood flow channel. Floodwaters on the northwest end of the beheaded flood flow channel reversed flow direction to create the northwest oriented Sage Creek tributary drainage route. Note how landforms in the region surrounding the through valley have been streamlined in a northwest-to-southeast direction. These streamlined landforms were shaped by southeast oriented flood flow that once moved across the region prior to the erosion of the deep northwest-to-southeast oriented through valley. Floodwaters were flowing in a southeast direction probably to the actively eroding Snake River valley in Idaho and were crossing the present-day Beaverhead Mountains-Centennial Mountains topographic barrier to the south at the location of Monida Pass, which is today a gap between the Beaverhead and the Centennial Mountains. See Red Rock River-Medicine Lodge Creek (South) drainage divide essay for maps and discussions related to Monida Pass.

Blacktail Deer Creek-Sage Creek drainage divide area

Figure 7: Blacktail Deer Creek-Sage Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Blacktail Deer Creek-Sage Creek drainage divide area north and east of figure 5 and includes a very small overlap area with figure 5. Sage Creek flows in an east-southeast and south direction from the west center edge of figure 7 to the south half of figure 7 (west half). Crooked Creek and Divide Creek are the southeast oriented streams flowing from the west edge of figure 7 (north of center) to join Sage Creek and Little Sage Creek is the southwest oriented stream flowing to the south center edge of figure 7 and joining Sage Creek south of figure 7. Blacktail Deer Creek is the north-northwest oriented stream flowing across the northeast corner region of figure 7. Price Creek is an east and north-northeast oriented tributary joining Blacktail Deer Creek near the northeast corner of figure 7 and Teddy Creek is a north-northwest and north oriented Price Creek tributary in the east half of figure 7. Note how the north-northeast oriented Price Creek valley is linked by through valleys with the southwest oriented Little Sage Creek valley and also with a west oriented stream flowing to south-southwest oriented East Creek, which then flows south oriented Sage Creek. The map contour interval for figure 7 is 50 meters and the through valley elevations at the drainage divides are between 2200 and 2250 meters. The adjacent hills all rise to at least 2400 meters suggesting the through valleys are at least 150 meters deep. The through valleys provide evidence of diverging and converging flood flow channels in what was at one time a south or southeast oriented anastomosing channel complex. At that time floodwaters were flowing in south and southeast directions across the region seen in figure 7 and headward erosion of deeper flood flow channels was capturing flood flow from adjacent less deep flood flow channels. Note also Cottonwood Creek near the word “MOUNTAINS”, which flows in an east-southeast, northeast, and north direction to join Blacktail Deer Creek north of figure 7. At the point where Cottonwood Creek turns from flowing in an east-southeast to northeast direction a through valley across the Blacktail Mountains links the Cottonwood Creek valley with the south-southwest oriented East Creek valley (and south oriented Sage Creek valley). The through valley floor at the drainage divide is between 2500 and 2550 meters. Elevations on either side rise to at least 2650 meters suggesting the through valley is at least 100 meters deep and may be deeper. The through valley provides evidence the south oriented flood flow once moved across Blacktail Mountain, although at that time the Blacktail Mountains were probably still emerging as an upland region. A combination of ice sheet related crustal warping that raised the Blacktail Mountains and of deep flood flow erosion was responsible for the emergence of the Blacktail Mountains as the topographic feature we see today.

Detailed map of Price Creek-Little Sage Creek drainage divide area

Figure 8: Price Creek-Little Sage 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 Price Creek-Little Sage Creek drainage divide area seen in less detail in figure 7. Price Creek flows in an east direction from near the north center edge of figure 8 to the northeast corner of section 22 and then turns to flow in a north-northeast direction to the north edge of figure 8 and joins north-northwest oriented Blacktail Deer Creek north of figure 8. The north oriented stream flowing along and across the east edge of figure 8 is Teddy Creek, which joins Price Creek north of the northeast corner of figure 8. Little Sage Creek originates in the northwest quadrant of section 26 (near east edge of figure 8) and flows in a north, west, and southwest direction to the south edge of figure 8 and joins south, west, and northwest oriented Sage Creek south and west of figure 8. A west oriented stream originates in the northwest corner of section 21 (west of the Price Creek headwaters) and flows to the west edge of figure 8 and joins south-southwest oriented East Creek west of figure 8 with water then flowing to south, west, and northwest oriented Sage Creek. Note the through valleys linking the Price Creek valley with the southwest oriented Little Sage Creek valley and the west oriented East Creek tributary valley. The map contour interval for figure 8 is 40 feet and both through valleys have elevations at their drainage divides of between 7400 and 7440 feet. Elevations in section 26 to the southeast rise to 7982 feet while elevations in the Blacktail Mountains to the north of figure 8 rise much higher suggesting the through valleys are at least 540 feet deep. The through valleys are water-eroded features and were eroded by south-southwest oriented flood flow on the present day north-northeast oriented Price Creek alignment, which was moving to a south oriented flood flow channel on the present day south oriented Sage Creek alignment. The south-southwest oriented flood flow channel was beheaded and reversed by headward erosion of a much deeper flood flow channel on the present day north-northwest oriented Blacktail Deer Creek alignment. Initially that deeper flood flow channel was probably oriented in a south-southeast direction, although it was later beheaded and reversed by headward erosion of a much deeper flood flow channel on the present day north-northeast oriented Beaverhead River alignment. The flood flow channel on the Beaverhead River alignment probably originated as a south-southwest oriented flood flow, which was subsequently beheaded and reversed by headward erosion of a much deeper valley on the Jefferson River alignment.

Basin Creek-Red Rock River drainage divide area

Figure 9: Basin Creek-Red Rock River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Basin Creek-Red Rock River drainage divide area south and east of figure 7 and does not includes an overlap area with figure 7. The Red Rock River flows in a west direction (near the south edge of the southwest quadrant of figure 9) and is located south of the south edge of the southeast quadrant of figure 9. Note southeast oriented streams flowing to the south edge of the southeast quadrant of figure 9, which south of figure 9 join the west oriented Red Rock River as barbed tributaries. Trail Creek is the southeast oriented Red Rock River tributary near the south center edge of figure 9 and Clover Creek is the southeast oriented Red Rock River tributary flowing to the east edge of figure 9 (south half) and joining the Red Rock River south and east of figure 9. Basin Creek is a south, southwest, and northwest oriented stream in the northwest quadrant of figure 9 and flows to the west edge of figure 9 (north half). West of figure 9 Basin Creek joins south, west, and northwest oriented Sage Creek as a barbed tributary. Little Basin Creek is a west-southwest and northwest oriented tributary to the southwest oriented Basin Creek segment and is located near the center of figure 9. The West Fork Blacktail Deer Creek flows in southwest and north-northwest direction in the northeast quadrant of figure 9 and is formed at the confluence of several tributaries near the northeast corner of figure 9. Note how at Clover Divide the West Fork Blacktail Deer Creek U-turn is linked by a through valley with the southeast oriented Clover Creek valley. The map contour interval for figure 9 is 50 meters and the through valley elevation at the drainage divide is between 2250 and 2300 meters. Elevations to the west rise to more than 2650 meters while elevations to the east rise even higher suggesting the through valley is at least 350 meters deep. The through valley was eroded by southeast oriented flood flow moving toward what at that time was probably an east oriented flood flow channel on the present day west oriented Red Rock River alignment. Other deep through valleys seen in figure 9 link the southeast oriented Clover Creek valley with west-southwest oriented Little Basin Creek valley and the Little Basin Creek valley with the southeast oriented Trail Creek valley. The Little Basin Creek-Trail Creek through valley floor elevation at the drainage divide is between 2200 and 2250 meters. Elevations to the west rise to more than 2500 meters and elevations to east rise even higher suggesting the through valley is at least 250 meters deep. The through valley was eroded by a southeast oriented flood flow on the present day northwest oriented Little Basin Creek segment alignment and was beheaded by headward erosion of the much deeper southwest Basin Creek valley segment. Floodwaters on the northwest end of the beheaded flood flow channel reversed flow direction to create the northwest oriented Little Basin Creek drainage route and northwest oriented Little Basin Creek tributaries.

Detailed map of Little Basin Creek-Trail Creek drainage divide area

Figure 10:Detailed map of Little Basin Creek-Trail 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 Little Basin Creek-Trail Creek drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 40 feet. Little Basin Creek flows is a west-southwest direction north of figure 10 and north oriented streams flowing to the north edge of figure 10 are Little Basin Creek tributaries. Trail Creek flows in a southeast direction from section 29 to the south edge of figure 10 (near southeast corner) and then flows to the west oriented Red Rock River. Note in the northwest quadrant of section 29 and the southwest quadrant of section 21 a through valley linking the southeast oriented Trail Creek valley with north and northwest oriented Little Basin Creek tributary valleys. The through valley floor elevation at the drainage divide is between 7280 and 7320 feet (the through valley in section 19 has an elevation of between 7320 and 7360 feet). Elevations in section 21 to the northeast rise to 8651 feet and elevations in section 25 to the southwest rise to 8263 feet suggesting the through valley is at least 940 feet deep. The through valley is a water-eroded landform and was eroded by a southeast oriented flood flow channel probably moving floodwaters to the present day Monida Pass locality (south of figure 10) and then to what was probably an actively eroding Snake River valley. Probably a southeast oriented flood flow channel converged with a south oriented flood flow channel in the swamp area of the southwest quadrant of section 21 to form the southeast oriented flood flow channel on the Trail Creek alignment. Headward erosion of the west-southwest oriented Little Basin Creek valley (north of figure 10) beheaded the converging south and southeast oriented flood flow channels and floodwaters on the north ends of the beheaded flood flow channels reversed flow direction to create the north and northwest and north oriented Little Basin Creek tributary drainage routes 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.

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