North Fork Shoshone River-South Fork Shoshone River drainage divide area landform origins in the Absaroka Mountains, northwest Wyoming, USA

Authors


 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the region between the North Fork Shoshone River and the South Fork Shoshone River in the Absaroka Range located in northwest Wyoming. The North Fork Shoshone River flows in an east direction to join the northeast oriented South Fork Shoshone River at Buffalo Bill Reservoir and to form the northeast oriented Shoshone River, which flows to the north and north-northeast oriented Bighorn River. Numerous southeast oriented tributaries join the northeast oriented South Fork Shoshone River as barbed tributaries while north and north-northeast oriented North Fork Shoshone River tributaries have northwest oriented tributaries. Passes or through valleys cross the high North Fork Shoshone River-South Fork Shoshone River drainage divide and link northwest oriented tributary valleys with southeast oriented tributary valleys. The barbed tributaries and passes are evidence of former southeast and south oriented flood flow channels, which were first captured by headward erosion of the much deeper northeast oriented South Fork Shoshone River valley and which were subsequently captured by headward erosion of the deep east oriented North Fork Shoshone River valley. Floodwaters on north and northwest ends of beheaded flood flow channels reversed flow direction to create north and northwest oriented tributary drainage routes. Reversed flood flow in newly beheaded flood flow channels captured yet to be beheaded flood flow from west of the North Fork Shoshone River valley head creating flood flow U-turns as south oriented floodwaters were diverted to flow in north directions to the newly eroded and much deeper North Fork Shoshone River valley. Floodwaters were derived from the western margin of a thick North American ice sheet and were flowing from western Canada to and across the present day Absaroka Mountain region. The Absaroka Range is located on the southwest rim of the deep “hole” in which the ice sheet was located with the rim being uplifted as south and southeast oriented floodwaters flowed across it. Headward erosion of the deep Yellowstone River valley from space in the deep “hole” being opened up by ice sheet melting captured southeast and south oriented flood flow channels in eastern and south central Montana. Floodwaters on north ends of beheaded flood flow channels reversed flow direction to create north oriented Yellowstone River tributary routes including the north oriented Bighorn River, which then captured south and southeast oriented flood flow from west of the actively eroding Yellowstone River valley head. The northeast oriented South Fork Shoshone River valley and the east oriented North Fork Shoshone River valley eroded headward to capture south and southeast oriented flood flow from west of the actively eroding Yellowstone River valley head.

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 North Fork Shoshone River-South Fork Shoshone River drainage divide area landform in the Absaroka Range of northwest 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 North Fork Shoshone River-South Fork Shoshone River drainage divide area landform evidence in the Absaroka Range located in northwest Wyoming will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

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

Figure 1: North Fork Shoshone River-South Fork Shoshone 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 North Fork Shoshone River-South Fork Shoshone River drainage divide area in the Absaroka Mountains and illustrates a region in northwest Wyoming with Yellowstone National Park located in the Wyoming northwest corner. The Absaroka Range is located along the Yellowstone National Park eastern boundary and extends in a southeast direction to the Owl Creek Mountains. The North Fork Shoshone River originates east of Yellowstone National Park (east of the Park boundary) and flows in an east direction to Buffalo Bill Reservoir where it is joined by the north-northeast and northeast oriented South Fork Shoshone River to form the northeast oriented Shoshone River, which joins the north oriented Bighorn River near the northeast corner of figure 1, North of figure 1 the Bighorn River flows to the northeast oriented Yellowstone River. The region east of the Absaroka Range and north of the Owl Creek Mountains seen in figure 1 is the Big Horn Basin. East of figure 1 are the Big Horn Mountains, which form the Big Horn Basin eastern boundary. West of the Shoshone River headwaters is the north-northwest oriented Yellowstone River, which flows to Yellowstone Lake. North of Yellowstone Lake the Yellowstone River flows in a northwest direction to Canyon, Wyoming and then in a northeast, north, and northwest direction to the north edge of figure 1. North of figure 1 the Yellowstone River gradually turns to flow in an east and even southeast direction before finally turning to flow in a northeast direction to where it is joined by the north oriented Bighorn River and then continues to flow in a northeast direction to join the Missouri River. South of Yellowstone Lake are headwaters of the south oriented Snake River, which flows to the south edge of figure 1 (near southwest corner). South and west of figure 1 the Snake River turns to flow in a northwest and then southwest, west, and north direction across Idaho with water eventually reaching the Pacific Ocean. South of the South Fork Shoshone River headwaters are headwaters of the southeast oriented Wind River, which flows to the south center edge of figure 1. South of figure 1 the Wind River makes an abrupt turn to flow in a north direction from Boysen Reservoir (near southeast corner of figure 1) through a deep canyon in the Owl Creek Mountains where it becomes the north oriented Bighorn River. The North Fork Shoshone River-South Fork Shoshone River drainage divide area investigated in this essay is generally located south of the North Fork Shoshone River, north and west of the South Fork Shoshone River, and east of the Yellowstone River drainage basin, although a small region downstream from Buffalo Bill Dam is also included.

Many of the north oriented drainage routes seen in figure 1 are on alignments of former south oriented flood flow channels. Floodwaters were derived from the western margin of a thick North American ice sheet and were flowing in south and southeast directions from western Canada to and across the region seen in figure 1. At that time the Absaroka Range, the Owl Creek Mountains, and other regional mountain ranges did not stand high above surrounding regions and floodwaters could freely flow across what are today high mountain ranges. These and other mountain ranges were uplifted as floodwaters flowed across them with the uplifted being related to the thick ice sheet presence. The ice sheet created a deep “hole” in which it became embedded by a combination of deep glacial erosion and of crustal warping. The crustal warping depressed regions under the ice sheet and raised regions along the ice sheet margin and elsewhere on the continent. The region seen in figure 1 could be considered to be part of the deeply eroded deep “hole” southwest rim. As long as the thick ice sheet stood higher than the deep “hole” southwest rim melt water floods flowed in south and southeast directions across the rim, although headward erosion of deeper and deeper valleys into the emerging mountain ranges resulted in systematic captures of flood flow and created an ever-changing flood flow pattern. In time ice sheet melting began to open up space in the deep “hole”, especially in the south, and south oriented flood flow channels east of the region seen in figure 1 drained those early open spaces. Deep valleys then eroded headward from the newly opened up space in the deep “hole” to capture the south and southeast oriented flood flow in eastern and central Montana (north of figure 1). One such valley was the Yellowstone River valley (north of figure 1), which beheaded the south oriented flood flow channels crossing the region in figure 1 in sequence from east to west. Floodwaters on north ends of the beheaded flood flow channels reversed flow direction to create north oriented drainage routes, which in turn captured south and southeast oriented still moving west of the actively eroding Yellowstone River valley head. Some these captures were made by headward erosion of northeast oriented tributary valleys while other captures were of well-developed southeast oriented flood flow channels. These massive flood flow reversals created the north oriented Bighorn River drainage system and the north and northwest oriented Yellowstone River headwaters drainage system seen in figure 1.

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

Figure 2: Detailed location map North Fork Shoshone River-South Fork Shoshone 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 North Fork Shoshone River-South Fork Shoshone River drainage divide area in the Wyoming Absaroka Mountains. Cody, Wyoming is located near the northeast corner of figure 2 and Buffalo Bill Reservoir is located near Cody. Yellowstone National Park is the red-brown area in the west half of figure 2.The Yellowstone River originates near the south edge of figure 2 (west half) and flows in a north-northwest direction to Yellowstone Lake and continues in a north direction at the northwest corner of figure 2.  The North Fork Shoshone River flows in a south direction from the north edge of figure 2 (just east of the Yellowstone National Park east boundary) to Pahaska and then turns to flow in a southeast and east direction to Buffalo Bill Reservoir where it is joined by the northeast oriented South Fork Shoshone River to form the northeast oriented Shoshone River, which flows to the northeast corner of figure 2. Labeled North Fork Shoshone River tributaries of interest in this essay from east to west are northeast and north oriented Breteche Creek, north-northeast oriented Whit Creek, north-northeast oriented Elk Fork with its tributary northeast oriented Borron Creek (Rampart Creek is the unlabeled northeast oriented Elk Fork tributary north and west of Borron Creek), and north-northeast oriented Fishhawk Creek. Labeled South Fork Shoshone River tributaries of interest in this essay are southeast, east-northeast, and south-southeast oriented Hardpan Creek and east-northeast oriented Ishawooa Creek. Note the labeled and unlabeled southeast oriented tributaries flowing to the northeast oriented South Fork Shoshone River as barbed tributaries and also the northwest oriented tributaries. These tributaries provide evidence the South Fork Shoshone River valley eroded headward across southeast oriented flood flow channels with the northwest oriented tributary valleys being initiated by flood flow reversals on northwest ends of beheaded flood flow channels. Also note the southeast and south oriented tributaries flowing to the east oriented North Fork Shoshone River and the north and north-northeast oriented tributaries from the south. Following headward erosion of the deep South Fork Shoshone River valley headward erosion of the deep North Fork Shoshone River captured the south and southeast oriented flood flow and floodwaters on north ends of the beheaded flood flow channels reversed flow direction to create the north oriented North Fork Shoshone River tributary routes.

East end of the North Fork-South Fork Shoshone River drainage divide area

Figure 3: East end of the North Fork-South Fork Shoshone River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of the east end of the North Fork-South Fork Shoshone River drainage divide area. Cody, Wyoming is located near the northeast corner of figure 3. The North Fork Shoshone River flows from the west edge of figure 3 (north half) to Buffalo Bill Reservoir where it joins the northeast oriented South Fork Shoshone River to form the east-northeast oriented Shoshone River, which flows to the north edge of figure 3 (near Cody). The South Fork Shoshone River flows in a northeast direction from the south edge of figure 3 (west half) to Buffalo Bill Reservoir. Note how downstream from Buffalo Bill Reservoir the Shoshone River flows through Shoshone Canyon, which has been carved into a high mountain ridge. The map contour interval for figure 3 is 50 meters and the Buffalo Bill Reservoir pool elevation is shown as 1636 meters. Cedar Mountain (on south side of Shoshone Canyon) rises to more than 2350 meters and Rattlesnake Mountain (the mountain north of Shoshone Canyon) rises much higher suggesting Shoshone Canyon is more than 700 meters deep. South of Cedar Mountain is a broad west-to-east oriented through valley linking the northeast oriented South Fork Shoshone River valley with north oriented Sulphur Creek, which flows to the Shoshone River near Cody. The floor of this through valley at the drainage divide has an elevation of between 1650 and 1700 meters. A classic question is how do major water gaps like Shoshone Canyon get formed, especially when an alternate route is readily available? One typical answer is the mountain was buried by debris when the river course was established and the river eroded its valley downward into the underlying mountain mass. However, this answer does not explain how the adjacent through valley was formed. The alternate explanation is the river course was established before the mountain mass was uplifted and the river eroded a deeper and deeper valley as the mountain mass rose around it.  This alternate answer also fails to explain the through valley south of Cedar Mountain. The evidence seen in figure 3 can only be explained by massive flood erosion, which originated on a surface as high, if not higher, than the highest points on Cedar Mountain, and which was flowing in multiple channels, such as in an anastomosing channel complex. As floodwaters eroded deeper and deeper flood flow channels into that early high level surface the region probably was uplifted and over time deeper flood flow channels captured floodwaters from less deep flood flow channels. In this case initially the flood flow channels were moving floodwaters in an east and perhaps southeast direction to a south oriented flood flow channel on the present day north oriented Bighorn River alignment. When headward erosion of the much deeper northeast oriented Yellowstone River valley (north of figure 3 and from space in the deep “hole” the melting ice sheet had occupied) beheaded the south oriented Bighorn River flood flow channel a massive flood flow reversal in the Big Horn Basin took place. That flood flow reversal created a situation where the northern flood flow channel through present day Shoshone Canyon had a much shorter route to the much deeper Yellowstone River valley and was able to capture the floodwaters which were flowing in southeast and east directions to reach the what had become the north oriented Bighorn River.

Detailed map of the Shoshone Canyon area

Figure 4: Detailed topographic map of the Shoshone Canyon area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 provides a detailed topographic map of the Shoshone Canyon area seen in less detail in figure 3 above. Buffalo Bill Reservoir can be seen in the southwest quadrant of figure 4. Buffalo Bill Dam is at the east end of Buffalo Bill Reservoir and the Shoshone River flows in an east-northeast direction through Shoshone Canyon and then in a north-northeast direction to the east center edge of figure 4. Cedar Mountain is south of Shoshone Canyon and Rattlesnake Mountain is north and west of Shoshone Canyon. The two mountains are segments of the same geologic structure, which were separated by headward erosion of the deep Shoshone Canyon. The map contour interval for figure 4 is 40 feet and the Buffalo Bill Reservoir elevation is shown as 5369 feet. The Shoshone River channel at the east end of Shoshone Canyon has an elevation of less than 5000 feet. The high point on Cedar Mountain south of Buffalo Bill Dam is more than 8080 feet. Elevations greater than 8600 feet can be seen on Rattlesnake Mountain in figure 4 and north and west of figure 4 elevations exceed 9000 feet. These elevations suggest Shoshone Canyon is at least 2700 feet deep. For purposes of this essay the Shoshone Canyon depth documents a minimum amount for flood flow erosion that took place between the time floodwaters in the Big Horn Basin were reversed to flow in a north and northeast direction (to the deep “hole” the ice sheet had occupied) and the present. Floodwaters at the time the massive flood flow reversal first occurred were flowing on a high level surface at least as high as the top of Cedar Mountain and as will be seen in subsequent figures, probably on a much higher surface. During the flood flow reversal process Shoshone Canyon was just one of several flood flow channels eroded into that high level surface, but because it provided a much shorter route to the deep “hole” it was able to capture floodwaters from the flood flow channels located south of Cedar Mountain. However, for a significant period of time floodwaters were eroding flood flow channels located south of Cedar Mountain at the same time floodwaters were eroding Shoshone Canyon.

Breteche Creek-Bear Creek drainage divide area

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

Figure 5 illustrates the Breteche Creek-Bear Creek drainage divide area west and slightly south of figure 3 and includes a significant overlap area with figure 3. The North Fork Shoshone River flows in an east direction along the north edge of figure 5 before turning to flow north of the northeast corner of figure 5. Wapiti is a small town located near the north center edge of figure 5. Sheep Mountain is a labeled upland in the northeast corner of figure 5 and Table Mountain is a labeled upland south of Wapiti. Whit Creek is northeast, north, and north-northwest oriented stream originating south and west of Table Mountain and joins the North Fork Shoshone River near Wapiti. Breteche Creek is a northeast and north oriented North Fork tributary east of Whit Creek. The South Fork Shoshone River flows in a northeast direction from the south edge of figure 5 (east of center) to the east center edge of figure 5. Note the southeast oriented streams flowing to the northeast oriented South Fork Shoshone River as barbed tributaries. Bear Creek is a northeast and southeast oriented tributary south of Sheep Mountain and Deer Creek is a southeast oriented tributary south and west of Bear Creek. Note the passes or through valleys eroded into drainage divide linking the Bear Creek and Deer Creek valleys with the north oriented Breteche Creek valley. The map contour interval for figure 5 is 50 meters and the pass elevations are between 2550 and 2600 meters. North and east of the passes elevations rise to at least 2700 meters and south and west of the passes elevations rise to more than 2800 meters. These elevations suggest the passes are at least 100 meters deep. The passes were eroded as south or southeast oriented flood flow channels at a time when the deep east oriented North Fork Shoshone River valley did not exist. Headward erosion of the deep North Fork Shoshone River valley into a high level surface at least as high as the pass elevations beheaded the south and southeast oriented flood flow channels. Floodwaters on the north ends of the beheaded flood flow channels reversed flow direction to create the north oriented Breteche Creek drainage route. Hardpan Creek originates near the southwest corner of figure 5 and flows in an east, northeast, and south-southeast direction to join the South Fork Shoshone River as a barbed tributary. A shallow north-to-south oriented through valley links the northeast oriented Whit Creek headwaters valley with the south-southeast oriented Hardpan Creek valley segment. South oriented flood flow probably crossed the drainage divide and was probably responsible for eroding the much deeper south-southeast oriented Hardpan Creek valley segment. However, it is possible the northeast oriented Hardpan Creek valley segment was initiated at a time when floodwaters flowed to both the actively eroding North Fork Shoshone River and the actively eroding South Fork Shoshone River valleys with the northeast oriented Hardpan Creek valley supplying captured south and southeast oriented floodwaters from west of the actively eroding North Fork Shoshone River valley head.

Detailed map of Breteche Creek-Bear Creek drainage divide area

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

Figure 6 illustrates a detailed topographic map of the Breteche Creek-Bear Creek drainage divide area seen in less detail in figure 5. The South Fork Shoshone River flows in a northeast direction across the southeast corner of figure 6. Bear Creek originates in the southwest corner of section 3 and flows in a southeast, northeast, and southeast direction to join the South Fork Shoshone River near the east edge of figure 6. Deer Creek (unlabeled in figure 6) originates in section 9 (west and south of Bear Creek headwaters) and flows in a southeast direction to the south center edge of figure 6 and south of figure 6 joins the northeast oriented South Fork Shoshone River as a barbed tributary. Breteche Creek flows from the west edge of figure 6 (near southwest corner) in a north-northeast and north direction to the north edge of figure 6 (west half) and north of figure 6 joins the east oriented North Fork Shoshone River. Note through valleys or passes in section 9 and the southeast corner of section 4 crossing the Breteche Creek-Bear Creek and the Breteche Creek-Deer Creek drainage divide. The map contour interval for figure 6 is 40 feet and the deepest through valley or pass between Breteche Creek and Bear Creek has an elevation of between 7600 and 7640 feet. Elevations in section 3 to the northeast rise to 8011 feet while elevations to the southwest rise much higher. These elevations suggest the through valley or pass is almost 400 feet deep. The through valley or pass was eroded as a southeast oriented flood flow channel moving floodwaters from the present day north oriented Breteche Creek alignment to the actively eroding Bear Creek valley. At that time the deep North Fork Shoshone River valley to the north did not exist. Headward erosion of the deep North Fork Shoshone River valley beheaded the south and southeast oriented flood flow channel and floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented Breteche Creek drainage route. Other through valleys or passes crossing the drainage divide provide evidence of multiple south and southeast oriented flood flow channels such as might be found in an anastomosing channel complex, which describe the channel complex that once crossed the region.

Elizabeth Creek-Ishawooa Creek drainage divide area

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

Figure 7 illustrates the Elizabeth Creek-Ishawooa Creek drainage divide area south and west of figure 5 and includes an overlap area with figure 5. The South Fork Shoshone River flows in a northeast direction across the southeast corner of figure 7. Ishawooa Creek originates near the southwest corner of figure 7 and flows in an east and east-northeast direction to the east edge of figure 7 and joins the South Fork Shoshone River east of figure 7. Rampart Creek flows in a northeast direction from the west edge of figure 7 (south half) to join northeast and north-northeast oriented Borron Creek to form north-northeast oriented Elk Fork, which flows to the north center edge of figure 7 and then to the east oriented North Fork Shoshone River. Wapiti Ridge is the high drainage divide separating the Ishawooa Creek drainage basin from the Elk Fork drainage basin. Note how Wapiti Ridge is crossed by deep passes or through valleys linking north and northwest oriented Elk Fork tributary valleys with south and southeast oriented Ishawooa Creek tributary valleys. For example near the center of figure 7 a deep pass or through valley links the north, northwest, south, and northwest oriented Elizabeth Creek valley with an unnamed south oriented Ishawooa Creek tributary valley. The map contour interval for figure 7 is 50 meters and the pass or through valley elevation is between 3300 and 3350 meters. Wapiti Ridge elevations on either side rise to more than 3500 meters suggesting the pass or through valley is at least 150 meters deep. A somewhat shallower pass or through valley crosses Wapiti Ridge to the northeast of the Elizabeth Creek pass or through valley and links the northwest oriented Lake Creek valley with the southeast oriented Yellow Creek valley. These and other similar passes or through valleys were eroded as southeast oriented flood flow channels at a time when the deep north-northeast oriented Elk Fork valley did not exist (and when the deep North Fork Shoshone River valley did not exist north and west of figure 7). Headward erosion of the deep north-northeast oriented Elk Fork valley beheaded the southeast and south oriented flood flow channels. Floodwaters on the northwest and north ends of beheaded flood flow channels reversed flow direction to create northwest and north oriented drainage routes.

Detailed map of Elizabeth Creek-Cut Coulee drainage divide area

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

Figure 8 illustrates a detailed topographic map of the Elizabeth Creek-Cut Coulee drainage divide area seen in less detail in figure 7. Wapiti Ridge extends from near the southwest corner to near the northeast corner of figure 8 and is the Elk Fork-Ishawooa Creek drainage divide. Borron Creek flows in a northeast direction across the northwest corner of figure 8 and joins Rampart Creek north of figure 8 to form north-northeast oriented Elk Fork. Elizabeth Creek originates in section 24 and flows in a north, northwest, south, and northwest direction to join Borron Creek near the north edge of figure 8. Cut Coulee is located south of the north oriented Elizabeth Creek headwaters and drains in a south and south-southeast direction to the south center edge of figure 8 and joins east and east-northeast oriented Ishawooa Creek south of figure 8. Note how in the southeast quadrant of section 24 there is a pass or through valley crossing Wapiti Ridge, which links the north oriented Elizabeth Creek valley with the south oriented Cut Coulee valley. The map contour interval for figure 8 is 40 feet and the pass or through valley elevation is given as 10,935 feet. The high point near the southwest corner of section 24 is shown as 11,454 feet and the high point in section 19 is shown as 11,645 feet suggesting the pass or through valley may be as much as 500 feet deep. The pass or through valley is a water eroded feature and was eroded by south oriented flood flow at a time when the deep Borron Creek valley to the north did not exist. The flood flow channel was eroded into a high level surface equivalent in elevation, if not higher, to the highest points seen on Wapiti Ridge today. At that time the Absaroka Range was just beginning to emerge and south oriented melt water floods could freely flow across what is today a high mountain range. Absaroka Range uplift occurred as floodwaters flowed across the region and as deep valleys eroded headward into the region to systematically capture the immense south and southeast oriented flood flow. Evidence such as this pass or through valley documents that flood flow once moved across the region where the Absaroka Range now stands.

Fishhawk Creek-Rampart Creek drainage divide area

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

Figure 9 illustrates the Fishhawk Creek-Rampart Creek drainage divide area north and west of the figure 7 and includes a significant overlap area with figure 7. Wapiti Ridge extends in a northeast direction across the southeast corner of figure 9. Except in the region south and east of Wapiti Ridge and a small region in the southwest corner of figure 9 the entire figure 9 region shown drains to the east oriented North Fork Shoshone River, which is located north of figure 9. Rampart Creek flows in a northeast direction from the south center edge of figure 9 to join northeast and north-northeast oriented Borron Creek and to form north-northeast oriented Elk Fork in the southeast quadrant of figure 9. Elk Fork then flows in a north-northeast direction to the northeast corner of figure 9. Seclusion Creek is an east and northeast oriented Elk Fork tributary located north of Rampart Creek. Sheep Mesa is a highland north of the center of figure 9, Blackwater Creek, West Fork Blackwater Creek, and Sheep Creek flow in north and north-northeast directions from Sheep Mesa to the north edge of figure 9. The north oriented stream west of Sheep Mesa is Fishhawk Creek, which originates in Glacier Basin (which straddles south edge of figure 9). Note how the high mountain ridge, which forms the Fishhawk Creek-Elk Fork drainage divide, is crossed by deep passes or through valleys linking west and northwest oriented Fishhawk Creek tributary valleys with east and southeast oriented tributary valleys to the east and northeast oriented Elk Fork tributary valleys. For example in the south center area of figure 9 a pass or through valley links an east-northeast and north oriented Seclusion Creek tributary valley with a west oriented Fishhawk Creek tributary valley. The map contour interval for figure 9 is 50 meters and the pass elevation is between 3250 and 3300 meters. Elevations immediately to the south rise to more than 3600 meters, as do elevations on Sheep Mesa to the north. These elevations suggest the pass may be as much as 300 meters deep. The pass was eroded by flood flow, which moved south on the present day north oriented Fishhawk Creek alignment and which was captured by reversed flood flow on the north-northeast oriented Elk Fork alignment so as to make a giant U-turn. South oriented flood flow channels east of Sheep Mesa were beheaded and reversed by headward erosion of the much deeper east oriented North Fork Shoshone River valley. The newly reversed flood flow channels east of Sheep Mesa then captured flood flow still moving in a south direction west of the actively eroding North Fork Shoshone River valley head. The captured flood flow moved in southeast, east, and northeast directions to the much deeper north-northeast oriented Elk Fork valley, which was being eroded headward from the deep east oriented North Fork Shoshone River valley. Other passes provide evidence of multiple captures of south oriented flood flow, which in each case made a U-turn to flow to the actively eroding north-northeast oriented Elk Fork valley. In time headward erosion of the deep North Fork Shoshone River valley beheaded and reversed flood flow on the Fishhawk Creek alignment and the actively eroding north oriented Fishhawk Creek valley then began to capture south oriented flood flow from west of the actively eroding North Fork Shoshone River valley head’s new position.

Detailed map of Glacier Creek-Seclusion Creek drainage divide area

Figure 10: Detailed map of Glacier Creek-Seclusion 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 Glacier Creek-Seclusion Creek drainage divide area seen in less detail in figure 9. Rampart Creek flows in a northeast direction from the south center edge of figure 10 to the east edge of figure 10 (just south of center) and east of figure 10 joins north-northeast oriented Elk Fork. Seclusion Creek originates in section 14 (north of Battlement Mountain) and flows in an east direction to the east edge of figure 10 (north of center) and east of figure 10 turns to flow in a northeast direction to join north-northeast oriented Elk Fork. Glacier Creek originates near the south edge of figure 10 (in Glacier Basin) and flows in a north and north-northwest direction to join north oriented Fishhawk Creek, which then flows to the north edge of figure 10 (near northwest corner). Near the center of figure 10 (just north of Battlement Mountain) is a pass or through valley linking an east-northeast and north oriented Seclusion Creek tributary valley with a west oriented Glacier Creek tributary valley. The map contour interval for figure 10 is 40 feet and the pass elevation is shown as 10,705 feet. Battlement Mountain to the south rises to 11,813 feet and an unnamed peak in the south half of section 11 rises to 11,690 feet suggesting the pass may be almost 1000 feet deep. While the region seen in figure 10 has been glaciated the pass is probably a water-eroded feature and was eroded by floodwaters that moved south on the present day north oriented Fishhawk Creek alignment and that were captured by reversed flow in an east direction to the north-northeast Elk Fork alignment and then to newly eroded and much deeper east oriented North Fork Shoshone River valley (north and east of figure 10). At that time the deep north oriented Fishhawk Creek and Glacier Creek valleys did not exist and floodwaters were flowing south in channels at least as high as the floor of the pass north of Battlement Mountain. Headward erosion of the deep east oriented North Fork Shoshone River valley north of figure 10 next beheaded and reversed the south oriented flood flow channel on the Fishhawk Creek alignment to create the north oriented Fishhawk Creek drainage route. Reversed flood flow on the Fishhawk Creek route captured south oriented floodwaters from further west and that captured flood flow helped erode the deep north oriented Fishhawk Creek valley. Glaciation of the region occurred after flood flow across the region had ended and the glaciation probably further modified and deepened at least some valleys seen in figure 10.

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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