South Fork Shoshone River-Snake River drainage divide area landform origins, along continental divide, Absaroka Range, Wyoming, USA

Authors


Abstract:

This essay uses topographic map evidence to interpret landform origins in the region between the South Fork Shoshone River and Snake River along the continental divide in the Wyoming Absaroka Range,. The South Fork Shoshone River originates in the Absaroka Range Shoshone Plateau area near the east-west continental divide and flows in a north-northeast and northeast direction to join the east oriented North Fork Shoshone River and to form the northeast oriented Shoshone River with water reaching the Yellowstone River and eventually the Gulf of Mexico. West of South Fork Shoshone River headwaters are headwaters of west oriented Buffalo Fork, which flows from the Buffalo Plateau area to the Snake River with water eventually reaching the Pacific Ocean.  North of Buffalo Fork headwaters and west of the South Fork Shoshone River headwaters are west and northwest oriented Yellowstone River headwaters in the Thorofare Plateau area and south of the South Fork Shoshone River headwaters and east of the Buffalo Fork headwaters are headwaters of streams flowing to the southeast oriented Wind River. Drainage divides between these four independent river systems are crossed by through valleys linking the opposing drainage routes. The through valleys when viewed as extensions of adjacent valleys can be used to reconstruct a south oriented anastomosing complex that was eroded by south and southeast oriented floods into what is today a high-level surface of which the Shoshone Plateau, Buffalo Plateau, and Thorfare Plateau are remnants. Floodwaters are interpreted to have been derived from the western margin of a thick North American ice sheet and were flowing in south and southwest directions from western Canada to and across the present day Absaroka Range. Initially the Absaroka Range had not emerged as a mountain range and over time floodwaters flowed across the emerging Absaroka Range. Absaroka Range emergence was probably caused by ice sheet related crustal warping and by headward erosion of deep valleys into the developing mountain mass. At first deep southeast and southwest oriented flood flow channels eroded headward into the rising mountain mass to systematically capture south and southeast flood flow channels. Floodwaters on north and northwest ends of beheaded flood flow channels then reversed flow direction to create north and northwest drainage routes. Subsequently a massive flood flow reversal reversed flood flow in the South Fork Shoshone River valley and still later a massive flood flow reversal created the northwest and north oriented Yellowstone River drainage route (in northwest Wyoming). Regional uplift probably continued after flood flow across the region ended and still later the high mountain valleys were glaciated and were further modified by glacial erosion.

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 South Fork Shoshone River-Snake River drainage divide area landform origins along the continental divide, Absaroka Range, Wyoming. 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 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 South Fork Shoshone River-Snake River drainage divide area landform evidence along the continental divide, Absaroka Range, Wyoming will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

South Fork Shoshone River-Snake River drainage divide area location map

Figure 1: South Fork Shoshone River-Snake River drainage divide area location map (select and click on maps to enlarge). National Geographic Society map digitally presented using National Geographic Society TOPO software.

Figure 1 provides a location map for the South Fork Shoshone River-Snake River drainage divide area along the continental divide in the Absaroka Range, Wyoming and illustrates a region in northwest Wyoming. The Montana-Wyoming state line is located along the north edge of figure 1 and the Wyoming state line is located along the west edge of figure 1. Yellowstone National Park is located in the northwest corner of Wyoming. The Absaroka Range extends from north of figure 1 along the eastern boundary of Yellowstone National Park to the Owl Creek Mountains. The Wind River flows in a southeast direction from Togwotee Pass (in southwest quadrant of figure 1) to the south center edge of figure 1 and south of figure 1 turns to flow in a north direction to Boysen Reservoir (near southeast corner of figure 1) and then through Wind River Canyon (not seen in figure 1, but eroded across the Owl Creek Mountains) to near Thermopolis where the river changes its name to become the Bighorn River.  The Bighorn River then flows in a north direction from Thermopolis to the north edge of figure 1 (near northeast corner). North of figure 1 the Bighorn River flows in a north-northeast direction to join the northeast oriented Yellowstone River. The Yellowstone River originates south and east of the southeast corner of Yellowstone National Park and flows in north-northwest direction to Yellowstone Lake. From Yellowstone Lake the Yellowstone River flows in a northwest, northeast, north and northwest direction to the north edge of figure 1. North of figure 1 (in southern Montana) the Yellowstone River turns to flow in an east, southeast, and then northeast direction to eventually join the Missouri River and water ultimately reaches the Gulf of Mexico. The Shoshone River is formed at Buffalo Bill Reservoir at the confluence of the east oriented North Fork Shoshone River and the north-northeast oriented South Fork Shoshone River and then flows in a northeast direction to join the Bighorn River near the north edge of figure 1. The Snake River is formed south of Yellowstone Lake and flows in a northwest, southwest, and south direction to Jackson Lake in Grand Teton National Park. From Jackson Lake the Snake River flows in a south direction to the south edge of figure 1 (near southwest corner). South of figure 1 the Snake River turns to flow in a northwest direction into eastern Idaho and eventually joins the Columbia River with water ultimately reaching the Pacific Ocean. Buffalo Fork is a west-southwest and west oriented Snake River tributary originating south of the Yellowstone River headwaters. The South Fork Shoshone River-Snake River drainage divide area investigated in this essay is located south and east of the southeast corner of Yellowstone National Park and is the in the region where the Yellowstone River, South Fork Shoshone River, Wind River, and Buffalo Fork (Snake River) all originate.

Before and while present day drainage systems were formed the region in figure 1 was crossed by massive south and southeast oriented melt water floods from the western margin of a thick North American ice sheet. At least initially the Absaroka Range and the Owl Creek Mountains had not emerged as high mountain ranges and melt water floods flowed across what are today high mountain ridges. The mountains emerged as ice sheet related crustal warping raised them and as deep valleys eroded headward into them to capture massive south and southeast oriented flood flow flowing across the region. The present day Bighorn River is located on the alignment of what began as a major south oriented flood flow channel, which converged with the southeast oriented Wind River flood flow channel (south of figure 1). Flood flow on the Bighorn River alignment was reversed when headward erosion of the much deeper northeast oriented Yellowstone River valley (from space in the deep “hole” the melting ice sheet had once occupied) beheaded the south oriented Bighorn River flood flow channel. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented Bighorn River drainage route, which then captured the southeast oriented Wind River flood flow channel. Deep northeast oriented valleys also eroded headward from the newly reversed Bighorn River flood flow channel to capture south and southeast oriented flood flow still moving west of the actively eroding Yellowstone River valley head. The deep north-northeast oriented South Fork Shoshone River valley eroded headward to capture southeast and south oriented flood flow to the southeast oriented Wind River flood flow channel. The south oriented Snake River valley was initiated as a south oriented flood flow channel. Headward erosion of the west oriented Buffalo Fork valley captured south oriented flood flow moving from the present day South Fork Shoshone River drainage basin  to the present day Wind River drainage basin. Through valleys (or passes across ridge mountain drainage divides) record former flood flow channels and provide evidence of flood flow capture events.

Detailed location map for South Fork Shoshone River-Snake River drainage divide area

Figure 2: Detailed location map South Fork Shoshone River-Snake 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 South Fork Shoshone River-Snake River drainage divide area along the continental divide in the Wyoming Absaroka Range. Red-brown areas are National Park lands with Yellowstone National Park being located along the north edge of figure 2 and Grand Teton National Park being located along the west edge of figure 2. Green shaded areas are National Forest lands and are generally located in mountainous regions. Green shaded areas in the east half of figure 2 are located in the Absaroka Range. The Snake River flows in a southwest and south direction from the north edge of figure 2 (west half) to Jackson Lake and then in an east direction to near the town of Moran where it turns to flow in a south-southwest direction to the southwest corner of figure 2. Terrace Mountain is a labeled high point near the center of figure 2. South Buffalo Fork flows in west-southwest and west direction to join west and south oriented North Buffalo Fork near Terrace Mountain and to form west oriented Buffalo Fork, which joins the Snake River near Moran. The Yellowstone River originates in the Thorofare Plateau area just north of the South Buffalo Fork headwaters and flows in a west, northwest, and north direction to the north center edge of figure 2. Crescent Mountain is a labeled high point located east of Terrace Mountain and is near the headwaters of South Buffalo Fork tributaries and headwaters. The South Fork Shoshone River originates in the region east of Crescent Mountain and flows in a north-northeast direction to the north edge of figure 2 (near the small town of Valley which is near northeast corner of figure 2). The Wind River originates near Togwotee Pass (south of Terrace Mountain) and flows in a southeast direction to the south edge of figure 2 (east half). South of Crescent Mountain are headwaters of south-southeast oriented DuNoir Creek, which flows to the southeast oriented Wind River. Note how four major river systems have headwaters in a small region along the east-west continental divide near Crescent Mountain. The Wind River, South Fork Shoshone River, and Yellowstone River today flow in opposite directions from their points of origin, but ultimately end up converging where the Bighorn River joins the Yellowstone River north and east of figure 2. The Snake River and the Yellowstone River (and the Yellowstone River tributaries) flow to oceans on opposite sides of the continent. This situation deserves an explanation and this essay attempts to provide that explanation.

Thorofare Creek-Younts Creek drainage divide area

Figure 3: Thorofare Creek-Youngs 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 Thorofare Creek-Younts Creek drainage divide area. The east-west continental divide follows the well-marked county line in the southwest quadrant of figure 3. South and west of the continental divide streams drain to Buffalo Fork and then the Snake River with water eventually reaching the Pacific Ocean. Thorofare Mountain is a labeled high point near the center of figure 3. The North Fork Yellowstone River originates west of Thorofare Mountain and flows in a north and southwest direction to join the southwest and north oriented South Fork Yellowstone River and to form the west and west-northwest oriented Yellowstone River, which flows to the west center edge of figure 3. West and north of figure 3 the Yellowstone River flows in a north-northwest direction into Yellowstone National Park. The South Fork Shoshone River flows in a north-northeast direction from the south edge of figure 3 (east half) to the east center edge of figure 3 and north and east of figure 3 joins the east oriented North Fork Shoshone River to form the northeast oriented Shoshone River. Note southeast oriented streams flowing to the South Fork Shoshone River as barbed tributaries including east-northeast and southeast oriented Robinson Creek, northeast and southeast oriented Younts Creek, and east and east-southeast oriented Marston Creek. North oriented streams flowing to the north edge of figure 3 are tributaries to the east oriented North Fork Shoshone River, which is located north of figure 3. Through valleys or mountain passes cross drainage divides and link valleys of streams flowing today in opposite directions. For example west of Thorofare Mountain and east of Younts Peak a through valley links the north oriented North Fork Yellowstone River valley with the southwest oriented South Fork Yellowstone River valley. The map contour interval for figure 3 is 50 meters and through valley floor elevation is between 3300 and 3350 meters. Thorofare Mountain rises to 3675 meters and Younts Peak rises to 3705 meters suggesting the through valley could be 325 meters deep. A similar through valley east of Thorofare Mountain links a northeast and southeast oriented Robinson Creek tributary valley with the southeast oriented Younts Creek valley and is linked by through valleys with the north oriented Thorofare Creek valley. Study of figure 3 drainage divides reveals many additional passes or through valleys crossing drainage divides. The through valleys (or mountain passes) are evidence of south oriented flood flow channels that once crossed the region. Headward erosion of the east oriented North Fork Shoshone River valley (north of figure 3) beheaded the south oriented flood flow channels in sequence from east to west. Floodwaters on north ends of the beheaded flood flow channels reversed flow direction to create north oriented North Fork Shoshone River tributary drainage routes. These newly form north oriented drainage routes often captured flood flow west of the actively eroding North Fork Shoshone River valley head and the captured floodwaters helped erode deep valleys seen today.

Detailed map of Thorofare Creek-Younts Creek drainage divide area

Figure 4: Detailed map of Thorofare Creek-Youtgs 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 Thorofare Creek-Younts Creek drainage divide area seen in less detail in figure 3.The Yellowstone River-South Fork Shoshone River drainage divide serves as the ranger district boundary with the Yellowstone River drainage basin in the west. Thorofare Mountain is located in section 5 and Younts Peak is located in section 6 (in southwest quadrant of figure 4). The North Fork Yellowstone River originates east of Younts Peak and flows in a north and west-southwest direction to the west edge of figure 4 (north half). The South Fork Yellowstone River originates south of Thorofare Mountain and flows in west-southwest direction to the south edge of figure 4 (near southwest corner). Near the west edge of section 5 a north-to-south oriented pass or through valley links the north oriented North Fork Yellowstone River valley with the a south oriented tributary valley draining to the South Fork Yellowstone River. The map contour interval is 40 feet and the pass elevation is shown as 10,980 feet. Younts Peak has an elevation of 12,156 feet and Thorofare Mountain has an elevation of 12,058 feet suggesting the pass is more than 1000 feet deep. While the region has been glaciated the pass is a water-eroded feature and was eroded by south oriented flood flow prior to headward erosion of the west-southwest oriented North Fork Yellowstone River. Headward erosion of the North Fork Yellowstone River valley beheaded and reversed the south oriented flood flow channel to create the north oriented North Fork Yellowstone River drainage route. Younts Creek flows in a northeast and southeast direction from the south center area of figure 4 to near the southeast corner of figure 4. South and east of figure 4 Younts Creek joins the north-northeast oriented South Fork Shoshone River as a barbed tributary. The north and northeast oriented stream originating in section 34 and flowing to the east edge of figure 4 turns to flow in a southeast direction east of figure 4 and joins southeast oriented Robinson Creek, which then joins the north-northeast oriented South Fork Shoshone River. In section 34 a well-defined north-to-south oriented through valley links the north and northeast oriented Robinson Creek tributary valley with the southeast oriented Younts Creek valley. The through valley elevation is between 10,000 and 10,080 feet. Elevations in section 36 to the rise to more than 11,480 feet and Thorofare Mountain to rises even higher. These elevations suggest the through valley is at least 1400 feet deep. The north oriented stream flowing to the north center edge of figure 4 is Thorofare Creek, which north of figure 4 flows to the east oriented North Fork Shoshone River. In the north half of section 34 and along the boundary between sections 26 and 27 passes link the Thorofare Creek valley with the north and northeast oriented Robinson Creek tributary valley. Elevations of these passes are between 10,560 and 10,600 feet and the drainage divide elevation near the north edge of figure 4 rises to 11,485 suggesting the passes are approximately 900 feet. The passes were eroded by south oriented flood flow moving from the present day north oriented Thorofare Creek alignment to what was then the actively eroding Robinson Creek valley. At that time topography in the region looked very different from it does today and floodwaters were eroding deep flood flow channels into a surface as high, if not higher, than the highest elevations seen in figure 6 today. In addition to headward erosion of deep valleys the region has probably been significantly uplifted since that time. After all flood flow ceased and the region was uplifted glaciers formed in some of the valleys and further shaped those valleys.

South Fork Shoshone River-South Buffalo Fork drainage divide area

Figure 5: South Fork Shoshone River-South Buffalo Fork drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the South Fork Shoshone River-South Buffalo Fork drainage divide area south of figure 3 and includes an overlap area with figure 3. The east-west continental divide serves as the county line and ranger district boundary and extends from the west edge of figure 5 (north half) to the south center edge of figure 5. South and west of the continental divide streams drain to Buffalo Fork and Snake River with water eventually reaching the Pacific Ocean. South Buffalo Fork flows in a north and west-northwest direction in the southwest quadrant of figure 5 and is joined by south-southwest oriented Lake Creek near the west edge of figure 5 (south half). Lost Creek is a southwest oriented Lake Creek tributary originating near Marston Pass. Note the high level Buffalo Plateau surface drained by South Buffalo Fork and its tributaries. North of the continental divide in the northwest quadrant of figure 5 is the southwest and north oriented South Fork Yellowstone River. East of the continental the South Fork Shoshone River flows in a north-northeast direction from the south edge of figure 5 to the northeast corner of figure 5. Younts Creek flows in a northeast and southeast direction in the northeast quadrant of figure 5 and is joined by its east and northeast oriented West Fork, which originates near Marston Pass. Also originating near Marston Pass is east-southeast oriented Marston Creek, which has a north-northeast oriented tributary west of Wall Mountain. Bliss Creek is a northeast and southeast oriented stream south of Wall Mountain, which joins the north-northeast oriented South Fork Shoshone River as a barbed tributary. Southwest and south-southwest oriented South Buffalo Fork tributaries are linked by passes or through valleys across the continental divide with northeast oriented South Fork Shoshone River tributary valleys. The Shoshone Plateau is located in the southeast quadrant of figure 5. The map contour interval for figure 5 is 50 meters and some of the passes are defined by five or more contour lines on a side. Shoshone Plateau elevations are approximately 3400 meters and Buffalo Plateau elevations to the west are approximately 100 meters lower. These plateaus are probably remnants of the surface on which south oriented floodwaters flowed as deep valleys eroded headward into the region, although the entire region has probably been uplifted since that time. The passes are evidence of flood flow channels that crossed what is today the east-west continental divide. Figure 6 below illustrate passes in the Marston Pass region.

Detailed map of Lost Creek-Marston Creek drainage divide area

Figure 6: Detailed map of Lost Creek-Marston 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 Lost Creek-Marston Creek drainage divide area seen in less detail in figure 5. The east-west continental divide extends from the west center edge of figure 6 to the ranger district boundary in the north center area of figure 5 and then in a south direction to the south center edge of figure 6. Marston Pass is located in the southeast quadrant of section 18. Lost Creek originates in section 18 west of Marston Pass and flows in a southwest and west-southwest direction to the west edge of figure 6 (south of center). East of Marston Pass the West Fork Younts Creek flows in an east direction from section 17 to the east edge of figure 6 (north half). The map contour interval for figure 6 is 40 feet and the Marston Pass elevation is between 10,240 and 10,280 feet. Elevations in the northeast corner of section 18 rise to 11,050 feet and elevations in the northwest quadrant of section 29 rise to 11,317 feet. These elevations suggest Marston Pass may be as much as 800 feet deep. South of Marston Pass in section 19 a deeper unnamed pass links the east oriented Marston Creek valley (not labeled in figure 6) with a north-northwest oriented Lost Creek tributary valley. The floor of this deeper pass has an elevation of between 10,120 and 10,160 feet. Elevations drop much faster on the east side of these passes suggesting floodwaters flowed in an east direction from the Buffalo Fork drainage basin to South Fork Shoshone River drainage basin before being reversed to flow in a west direction to the south oriented Snake River valley. The South Fork Yellowstone River flows in a southwest direction parallel to Lost Creek, but on the north side of the continental divide suggesting both drainage route alignments were established under similar conditions. Near the east edge of figure 6 there is a 1000-foot deep notch in the continental divide just south of the point where the South Fork Yellowstone River turns from flowing in a southwest direction to flowing in a north direction. At one time a south oriented flood flow channel converged with a southwest oriented flood flow channel and flowed into the present day Lost Creek drainage basin. At first these floodwaters spilled in an east direction to a deeper flood flow channel on the South Fork Shoshone River alignment. However, headward erosion of the deeper southwest oriented Lost Creek valley from the Lake Creek valley, which had eroded headward from the South Buffalo Fork valley, captured the east oriented flood flow and diverted the floodwaters westward to the developing Snake River drainage basin. A reversal of flood flow in the Yellowstone River drainage basin ended south oriented flood flow into the region. Prior to the east oriented flood flow southwest oriented flood flow channels crossed the region, although headward erosion of a much deeper flood flow channel on South Fork Shoshone River alignment led to the east oriented flood channels, which then captured by Lost Creek valley headward erosion.

Detailed map of Marston Creek-South Buffalo Fork drainage divide area

Figure 7: Detailed map of Marston Creek-South Buffalo Fork drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 provides a detailed topographic map of the Marston Creek-South Buffalo Fork drainage divide area seen in less detail in figure 5 and includes an overlap area with figure 6. The east-west continental extends from the north edge of figure 7 (west of center) to the south edge (east of center). The upland region west of the continental divide is known as the Buffalo Plateau. Marston Creek is the east oriented stream flowing along the north edge of the northeast quadrant of figure 7 and east of figure 7 joins the north-northeast oriented South Fork Shoshone River. A north-northeast oriented Marston Creek tributary originates in section 32 near the continental divide. The southwest oriented stream on the southwest side of the continental divide and flowing through sections 5 and 7 to the south edge of figure 7 is a South Buffalo Fork tributary as are other streams west of the continental divide. In the northeast quadrant of section 5 a through valley or pass links the southwest oriented South Buffalo Fork tributary valley with the north-northeast oriented Marston Creek tributary valley. The map contour interval for figure 7 is 40 feet and the through valley elevation is 10,218 feet. The continental divide in the northeast corner of section 6 rises to 10,908 feet and the ridge in section 8 rises to 10,830 feet suggesting the through valley is approximately 600 feet deep. The through valley was eroded by southwest oriented flood flow moving from the present day north oriented South Fork Shoshone River drainage basin to the South Buffalo Fork drainage basin. Subsequently a flood flow reversal created the north-northeast oriented Marston Creek tributary drainage route and captured south oriented flood flow still moving west of the flood flow reversal region. The captured flood flow then eroded the much deeper Marston Creek valley leaving the Buffalo Plateau upland surface as a relic surface from the time when floodwaters were still flowing in a southwest and south direction to the actively eroding west oriented Buffalo Fork valley and its tributary valleys. How much erosion occurred in the Buffalo Plateau region prior to headward erosion of the Buffalo Fork valley and its tributary valleys is difficult to determine.

South Fork Shoshone River-DuNoir Creek drainage divide area

Figure 8: South Fork Shoshone River-DuNoir Creek) drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates the South Fork Shoshone River-DuNoir Creek drainage divide area and is located south of figure 5 and includes a significant overlap area with figure 5.  The continental divide is shown with a marked line extending from the west edge of figure 8 (south half) to Crescent Mountain (near center of figure 8) and then in a north direction along the ranger district boundary to the north center edge of figure 8. South Buffalo Fork originates west of Crescent Mountain and flows in a north-northeast and west-northwest direction to the west edge of figure 8 (near northwest corner). Cub Creek is a west oriented stream originating south of the South Buffalo Fork headwaters and flows to the west edge of figure 8 before turning to flow in a northwest direction to join South Buffalo Fork. Note how a through valley or pass links the north-northeast oriented South Buffalo Fork headwaters valley with the Cub Creek valley. The map contour interval for figure 8 is 50 meters and the through valley is defined by at least four contour lines on each side. The South Fork Shoshone River originates near Shoshone Pass (on the ranger district boundary east and south of Crescent Mountain) and flows in a north-northeast direction to the north edge of figure 8 (east half). Note southwest oriented South Buffalo Fork tributaries originating along the continental divide and linked by through valleys or passes with northeast oriented headwaters of southeast oriented streams flowing to the north-northeast oriented South Fork Shoshone River as barbed tributaries. South oriented streams south of the continental divide in the southwest quadrant of figure 8 and south of the ranger district boundary in the southeast quadrant of figure 8 are tributaries to the southeast oriented Wind River, which is located south of figure 8. The south oriented stream flowing from near Shoshone Pass to the south center edge of figure 8 is DuNoir Creek, which south of figure 8 flows to the Wind River. Shoshone Pass is a through valley linking the north-northeast oriented South Fork Shoshone River valley with the south oriented DuNoir Creek valley. The Shoshone Pass elevation is difficult to read on figure 8, but appears to be between 2850 and 2900 meters. Crescent Mountain to the west rises to 3456 meters and the unnamed mountain on the drainage divide to the east rises to 3472 meters suggesting Shoshone Pass may be as much as 550 meters deep. Shoshone Pass was eroded by south oriented flood flow moving from the present day north-northeast oriented South Fork Shoshone River valley to what was then an actively eroding south oriented DuNoir Creek valley, which had eroded headward from an actively eroding southeast oriented Wind River valley. A massive flood flow reversal north of Shoshone Pass created the present-day north-northeast oriented South Fork Shoshone River drainage system and the Shoshone River-Wind River drainage divide. The flood flow reversal was probably greatly aided by ice sheet related crustal warping that raised the Absaroka Range as immense melt water floods flowed across it.

Detailed map of South Buffalo Fork-Perry N Boday Creek drainage divide area

Figure 9: Detailed map of South Buffalo Fork-Perry N Boday Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 provides a detailed topographic map of the South Buffalo Fork-Perry N Boday drainage divide area seen in less detail in figure 8. The continental divide serves as a National Forest and Wilderness Area boundary and extends from the east edge of figure 9 to Crescent Mountain and then to near the south center edge of figure 9 before continuing along and across the south edge of the southwest quadrant of figure 9. Perry N Boday Creek is a southeast, east, and southeast oriented stream south of Crescent Mountain flowing to the south edge of figure 9 (east half). South and east of figure 9 Perry N Boday Creek flows to DuNoir Creek, which then flows to the southeast oriented Wind River. East of the continental divide Crescent Creek flows in a southeast direction to the east edge of figure 9 (north of center) and has a north-northwest and north-northeast oriented tributary. East of figure 9 Crescent Creek flows to the north-northeast oriented South Fork Shoshone River. West of the continental divide in the southwest quadrant of figure 9 Cub Creek flows in a southwest and west direction to the west edge of figure 9 (near southwest corner). West of figure 9 Cub Creek turns to flow in a northwest direction to join South Buffalo Fork. South Buffalo Fork originates in the center of figure 9 and flows in a north-northeast direction in section 25 before turning in section 24 to flow in a northwest direction to the north edge of figure 9 (west half). A west and southwest oriented tributary joins South Buffalo Fork at the South Buffalo Fork elbow of capture (the point where South Buffalo Fork turns from flowing in a north-northeast direction to flowing in a northwest direction). Through valleys link the north-northeast oriented South Fork Buffalo Creek valley with the southwest oriented Cub Creek headwaters valley and also with the southeast oriented Perry N Boday Creek valley. The map contour interval for figure 9 is 40 feet. The South Buffalo Fork-Cub Creek through valley elevation is between 9880 and 9920 feet while the South Buffalo Fork-Perry N Boday Creek through valley floor elevation is between 10,080 and 10,120 feet. Elevations in the northeast corner of section 26 rise to 10,961 feet and Crescent Mountain rises to 11,370 feet suggesting the through valleys may be more than 700 feet deep. The through valleys are water-eroded valleys and were eroded by diverging south oriented flood flow channels prior to headward erosion of a much deeper southwest oriented flood flow channel on the present day southwest oriented South Buffalo Fork valley (west of figure 9). The deeper southwest oriented flood flow channel beheaded a southeast oriented flood flow channel that converged with a southwest oriented flood flow channel at the present day South Buffalo Fork elbow of capture. Floodwaters on the northwest end of the beheaded flood flow channel reversed flow direction to create the northwest oriented South Buffalo Fork drainage route segment, which then captured the southwest oriented flood flow channel and beheaded and reversed the south-southwest oriented flood flow channel on the present day north-northeast oriented South Buffalo Fork headwaters alignment. Flood flow to the Perry N Boday Creek valley may have been beheaded prior to the South Buffalo Fork flood flow reversal as floodwaters moving to the southwest oriented Cub Creek headwaters valley eroded a deeper and deeper channel. Uplift of the Absaroka Range probably greatly aided the flood flow reversals as immense melt water floods flowed across the region.

Detailed map of South Fork Shoshone River-DuNoir Creek drainage divide area

Figure 10: Detailed map of South Fork Shoshone River-DuNoir 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 South Fork Shoshone River-DuNoir Creek drainage divide area seen in less detail in figure 8 and includes an overlap area with figure 9. The east-west continental divide extends from the west edge of figure 10 to Crescent Mountain and then in a north direction to the north edge of figure 10 (west half). Perry N Boday Creek flows in a southeast direction from the west edge of figure 10 (south of the continental divide) to join south oriented East DuNoir Creek in section 9 (near south edge of figure 10). South of figure 10 East DuNoir Creek joins southeast oriented West DuNoir Creek to form south-southeast oriented DuNoir Creek, which then flows to the southeast oriented Wind River. Shoshone Pass is at the north end of the south oriented East DuNoir Creek valley. East and north of Shoshone Pass is the north-northeast oriented South Fork Shoshone River valley. Shoshone Pass is a deep through valley linking the South Fork Shoshone River valley with the south oriented East DuNoir Creek valley. The map contour interval for figure 10 is 40 feet and the Shoshone Pass elevation is between 9640 and 9680 feet. Shoshone River-Wind River drainage divide elevations east of Shoshone Pass rise to more 11,400 feet while elevations on Crescent Mountain to the west rise to 11,370 feet. These elevations suggest Shoshone Pass is approximately 1600 feet deep. Shoshone Pass is a water-eroded feature and was eroded by south oriented flood flow moving from the present day north oriented South Fork Shoshone River valley to what was then the actively eroding south oriented East DunNoir Creek valley and that converged with a southeast oriented flood flow channel on the Perry N Boday Creek alignment near the south edge of figure 10. The diverging and converging flood flow channels that once crossed the Buffalo and Shoshone Plateau regions were components of a large-scale anastomosing channel complex that had eroded into a high level surface equivalent in elevation to the highest present day Absaroka Range elevations seen today. This anastomosing channel complex was formed before the Absaroka Range emerged as a high mountain range and was dismembered as much deeper valleys eroded headward into the region to capture the immense south and southeast oriented flood flow and as ice sheet related crustal warping was raising the Absaroka Range as floodwaters flowed across it.

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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