Tongue River-Goose Creek drainage divide area landform origins in Wyoming Bighorn Mountains, USA

· Bighorn Mountains, Tongue River, Wyoming
Authors

 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the region between the Tongue River and Goose Creek in the Wyoming Bighorn Mountains. The Bighorn Mountains are a north to south oriented mountain range in north central Wyoming and are located between the Powder River Basin to the east and the Bighorn Basin to the west. Steep east and west slopes bound a deeply eroded and rugged Bighorn Mountains upland surface, which stands 1000 to 2000 meters above the adjacent basin floors. Mountains and other high areas rise several hundred meters above the uneven upland surface. The Tongue River is formed on the Bighorn Mountains upland surface at the confluence of the north oriented South Tongue River and the more easterly North Tongue River, both of which originate on and flow across the Bighorn Mountains upland surface. Goose Creek headwaters flow in north and northeast directions across the Bighorn Mountains upland surface before flowing in a northeast direction to the eastern base of the Bighorn Mountains and then in a north direction to join the east and northeast oriented Tongue River. Through valleys eroded across Bighorn Mountain upland surface drainage divides link Tongue River tributary valleys and provide evidence of south and southeast oriented flood flow channels that once crossed what is now the Bighorn Mountains upland surface. Floodwaters are interpreted to have been derived from the western margin of a thick North American ice sheet and were flowing from western Canada to and across the Bighorn Mountain upland surface. At that time the Bighorn Mountains upland surface did not stand high above the surrounding region as it does today and floodwaters could freely flow across what is today an erosion surface capping a high mountain range. The Bighorn Mountains emerged as flood water erosion deeply eroded the surrounding region and as ice sheet related crustal warping raised North American mountain ranges to create a deep “hole” in which the ice sheet was located. As the ice sheet melted south oriented flood flow across the emerging Bighorn Mountains was systematically captured and diverted in north and northeast directions to space in the deep “hole” being opened up by the ice sheet melting. This essay illustrates through valleys on the Bighorn Mountains upland surface that were eroded by south oriented flood flow prior to and during the reversal of flood flow. The Bighorn Mountains upland surface may have been significantly uplifted since flood flow across the region ended.

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 Tongue River-Goose Creek drainage divide area landform origins in the Wyoming Bighorn Mountains, USA. Map interpretation methods can be used to unravel many geomorphic events leading up to formation of present-day drainage routes and development of other landform features. While each detailed topographic map feature provides detailed evidence to be explained, the solution must be consistent with explanations for adjacent area map evidence as well as solutions to big picture map evidence puzzles. I invite readers to improve upon my solutions and/or to propose alternate solutions that better explain evidence and are also consistent with adjacent map area and big-picture evidence. Readers may do so either by making comments here or by writing and publishing their own essays and then by leaving a link to those essays in 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 Tongue River-Goose Creek drainage divide area landform evidence in the Wyoming Bighorn Mountains will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Tongue River-Goose Creek drainage divide area location map

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

Figure 1 provides a location map for the Tongue River–Goose Creek drainage divide area in Wyoming Bighorn Mountains. The west to east oriented Montana-Wyoming state line extends across the center of figure 1 with Montana north of Wyoming. The Yellowstone River is the northeast oriented river flowing between Laurel and Billings in the northwest corner of figure 1. The Bighorn Mountains extend in a south-southeast direction from just north of the state line to the south center edge of figure 1. The Bighorn Basin is west of the Bighorn Mountains in Wyoming and is drained by the north and north-northeast oriented Bighorn River, which flows to the northeast oriented Yellowstone River north of figure 1. The Powder River Basin is east of the Bighorn Mountains and in the southeast corner of figure 1 the north and northeast oriented Powder River drains the Powder River Basin with the Powder River flowing to the northeast oriented Yellowstone River east and north of figure 1. The Tongue River (not well labeled in figure 1) originates in the Bighorn Mountains south of the state line and flows in an east-northeast direction to the towns of Dayton, Ranchester, and Acme, Wyoming before turning to flow in a northeast direction to Decker, Montana and Tongue River Reservoir. From Tongue River Reservoir the Tongue River flows in a northeast direction to Ashland, Montana and then in a north and north-northeast direction to the north edge of figure 1 and finally joins the northeast oriented Yellowstone River north of figure 1. Not shown in figure 1 is the north oriented South Tongue River, which flows in a north direction from near Dome Peak to join the east-northeast oriented North Tongue River and to form the east-northeast oriented Tongue River (more detailed maps show many North Tongue River and Tongue River twists and turns not shown in figure 1). Goose Creek is a Tongue River tributary and joins the Tongue River near Acme, Wyoming. Goose Creek originates in the Bighorn Mountains east of Dome Peak and flows in a north and northeast direction to Sheridan, Wyoming before turning to flow in a north direction to join the Tongue River. The Tongue River-Goose Creek drainage divide area investigated in this essay is located west and north of Goose Creek, east of the north oriented South Tongue River, and south of the east-northeast oriented Tongue River and North Tongue River and is primarily located in the Bighorn Mountains.

Almost all drainage routes seen in figure 1 are today oriented in north directions, although these north oriented drainage routes originated during the reversal of immense south oriented melt water floods. The floods were derived from the western margin of a thick North American ice sheet and were flowing from western Canada to and across the region in figure 1. At that time the Bighorn Mountains had not emerged as a high mountain range and/or were just beginning to emerge and floodwaters could freely flow across what is today a high mountain range. The Bighorn Mountains emerged as deep south-oriented flood flow channels eroded headward into the adjacent Powder River and Bighorn Basins and as floodwaters stripped great thickness of bedrock from those basin areas. At the same time ice sheet related crustal warping was uplifting the Bighorn Mountains (and perhaps the entire region) as the ice sheet created a deep “hole” in which the ice sheet was located. The Bighorn Mountains and the entire region in figure 1 could be considered to be a segment of the deep “hole’s” deeply eroded and warped southwest rim. The reversal of flood flow occurred when the deep northeast oriented Yellowstone River valley eroded headward across Montana to capture immense the south and southeast oriented melt water floods and to divert floodwaters into space at the south end of the deep “hole” being opened up by ice sheet melting. At first space at the south end of the deep “hole” drained in a south direction using flood flow channels east of figure 1. Headward erosion of the deep Yellowstone River valley and its northeast oriented tributary valleys beheaded south and southeast oriented flood flow routes in sequence from east to west. Floodwaters on north ends of the beheaded flood flow routes reversed flow direction to create north oriented drainage systems, which then captured south and southeast oriented flood flow from west of the actively eroding Yellowstone River valley head. Generally north oriented drainage routes seen in figure 1 are located on the alignments of south oriented flood flow channels that were beheaded and reversed to create the north oriented drainage route.

Detailed location map for Tongue River-Goose Creek drainage divide area

Figure 2: Detailed location map Tongue River-Goose Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 2 provides a more detailed location map for the Tongue River-Goose Creek drainage divide area in the Wyoming Bighorn Mountains. The green colored area is National Forest land in the Bighorn Mountains. The dashed line extending from the northwest corner of figure 2 to the south center edge of figure 2 is the Bighorn Mountains drainage divide, which also serves as a county line, and drainage west of the line flows to the Bighorn River in the Bighorn Basin. Burgess Junction is a highway intersection located in the Bighorn Mountains. The North Tongue River originates near the county line west of Burgess Junction and flows in a southeast and northeast direction to be joined by northeast and east oriented Fool Creek north of Burgess Junction. At the point where Fool Creek joins it the North Tongue River makes an abrupt turn to flow in an east-southeast direction to join the north oriented South Tongue River and to form the Tongue River. Once formed the Tongue River flows in an east, northeast, east, and northeast direction to Dayton, Ranchester, Acme, and the east edge of figure 2 (near northeast corner). The South Tongue River originates in the south center area of figure 1 and flows in a northwest and north direction to join the North Tongue River and to form the east oriented Tongue River. The Little Tongue River is a north-northeast and north oriented tributary joining the Tongue River near Dayton. Wolf Creek is a northeast, north, north-northeast, and north oriented tributary joining the Tongue River near Ranchester. Goose Creek is formed near Sheridan at the confluence of Big Goose Creek and Little Goose Creek and then flows in a north direction to join the Tongue River near Acme. Of greatest interest in this essay is the West Fork Big Goose Creek , which originates near the south center edge of figure 2 (just east of the county line) and which then flows in a north and northeast direction to join north oriented East Fork Big Goose Creek and to form Big Goose Creek, which then flows in a northeast and east direction to near Sheridan where it joins north-northeast and north oriented Little Goose Creek. North of the North Tongue River headwaters are headwaters of the north and north-northeast oriented Little Bighorn River, which flows to the north edge of figure 2 (west half) and north of figure 2 turns to flow in a north and northwest direction to join the north-northeast oriented Bighorn River (see figure 1). North-northeast oriented Lick Creek and Lake Creek (east of the Little Bighorn River headwaters) flow to the northwest oriented Dry Fork Little Bighorn River (unlabeled in figure 2). The area investigated in this essay is in the Bighorn Mountains and begins with the Dry Fork Little Bighorn River-North Tongue River drainage divide and proceeds in south and southeast direction to north and northeast oriented West Fork Big Goose Creek and is bounded on the west by the north oriented South Tongue River.

Dry Fork Little Bighorn River-North Tongue River drainage divide area

Figure 3: Dry Fork Little Bighorn River-North Tongue River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of Dry Fork Little Bighorn River-North Tongue River drainage divide area and is located in the high Bighorn Mountains. The map contour interval for figure 3 is 20 meters. The Bighorn Mountains northeast flank can be seen in the northeast quadrant of figure 3. Elevations near the northeast corner of figure 3 are less than 1400 meters while elevations near the southwest corner of figure 3 are greater than 2600 meters. As can be seen in figure 3 the Bighorn Mountains have a deeply eroded upland surface surrounded by steep slopes leading down to the Powder River Basin surface to the northeast. While not seen in figure 3 steep slopes lead down to the Bighorn Basin surface in the west. Twin Buttes is a labeled high point slightly west of the south center of figure 3. Fool Creek flows in an east-northeast from the southwest corner of figure 3 to join south oriented Camp Creek (north and east of Twin Buttes) and then turns to flow in a southeast direction to almost immediately join the northeast and east-southeast oriented North Tongue River (not labeled in figure 3).  The North Tongue River flows in a northeast direction from the south edge of figure 3 (south of Twin Buttes) to where it is joined by Fool Creek and then turns to flow in an east-southeast direction to be joined by the north oriented South Tongue River and to form the Tongue River. Once formed the Tongue River flows in an east and northeast direction through Box Canyon to the east edge of figure 3 (slightly south of center). The South Tongue River (not labeled in figure 3) flows in a north direction from the south center edge of figure 3 to join the North Tongue River and to form the east and northeast oriented Tongue River, which then flows down the steep Bighorn Mountains northeast flank. The Dry Fork Little Bighorn River originates a short distance north and west from where Camp Creek joins Fool Creek and then flows in a northwest direction to the west edge of figure 3 (near northwest corner) and joins the north-northeast oriented Little Bighorn River north and west of figure 3. Note how the northwest oriented Dry Fork valley is aligned with the east-southeast oriented North Tongue River valley segment and that the two valleys are linked by a northwest to southeast oriented through valley. The through valley floor elevation at the Dry Fork-Camp Creek drainage divide is 2280 meters. Elevations on Dry Fork Ridge and Skull Ridge to the north and east of the through valley at several points rise to more than 2600 meters suggesting the ridge top was once an erosion surface equivalent in elevation to those high points. South and west of the through valley elevations rise to more than 2600 meters in the southwest corner of figure 3. These elevations suggest the Dry Fork-Tongue River through valley is at least 220 meters deep. The through valley is a water-eroded valley and was eroded by southeast oriented flood flow moving to what at that time was the actively eroding Tongue River valley. At that time elevations north and west of the Bighorn Mountains were at least as high as the present day Bighorn Mountains upland surface elevation, which means the Bighorn Mountains were still emerging as a high mountain range. Probably at that time the Tongue River valley was eroding headward from a deep south oriented flood flow channel in the Powder River Basin to the east. Flood flow in the Dry Fork valley was reversed when it was beheaded by headward erosion of the much deeper north-northeast oriented Little Bighorn River valley.

Detailed map of Dry Fork Little Bighorn River-North Tongue River drainage divide area

Figure 4: Detailed map of Dry Fork Little Bighorn River-North Tongue River 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 Dry Fork Little Bighorn River-North Tongue River drainage divide area seen in less detail in figure 3. The North Tongue River flows in a northeast direction from the south edge of figure 4 (west of center) to section 17 where it is joined by Fool Creek and turns to flow in a southeast and east direction to the east edge of figure 4 (south half). The unlabeled north-northeast oriented stream joining the North Tongue River near the west edge of section 22 (near southeast corner of figure 4) is the South Tongue River and the east oriented drainage route in section 22 is the Tongue River. Fool Creek flows in a north-northeast, east-northeast, and east-southeast direction from the southwest corner of figure 4 and joins the North Tongue River in section 17. Camp Creek originates in section 8 and flows in a south-southwest and southeast direction to join Fool Creek near the east edge of section 18. The Dry Fork Little Bighorn River originates near the north edge of section 18 and flows in a northwest direction to the northwest corner of figure 4. North and west of figure 4 the Dry Fork joins the north-northeast oriented Little Bighorn River. Figure 4 better illustrates the Dry Fork-North Tongue River through valley and the deepest point in the through valley is located in the south half of section 7, although the through valley is broader and extends south and west into adjacent sections. The map contour interval for figure 4 is 40 feet and the Dry Fork-Camp Creek drainage divide elevation at its lowest point is 7480 feet. Skull Ridge to the east rises to 8321 feet. The high point at Twin Buttes to the south is 8235 feet. These elevations suggest the through valley is at least 750 feet deep. Note how north of Twin Buttes the Fool Creek-North Tongue River drainage divide is crossed by additional through valleys and east of Twin Buttes several through valleys link the North Tongue River valley with the South Tongue River valley. These additional though valleys provide evidence of anastomosing flood flow channels that once crossed the region. While the northwest to southeast oriented through valley was eroded by southeast oriented flood flow on the present day northwest oriented Dry Fork alignment some of the other through valley were eroded by floodwaters coming from west of figure 4 on the Fool Creek and North Tongue River alignments. Flood flow on the Dry Fork alignment was beheaded and reversed before flood flow on western flood flow channels was captured as the deep north-northeast oriented Little Bighorn River valley eroded headward.

South Tongue River-Wolf Creek drainage divide area

Figure 5: South Tongue River-Wolf Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the South Tongue River-Wolf Creek drainage divide area south and east of figure 3 and includes an overlap area with figure 3. The map contour interval for figure 5 is 20 meters. Elevations near the northeast corner of figure 5 are less than 1300 meters while elevations on the Bighorn Mountains upland surface are generally greater than 2400 meters except in the deeper valleys and reach 2892 meters at Black Mountain in the southeast quadrant of figure 5. The North Tongue River flows in an east and northeast direction from the west edge of figure 5 (west of Burgess Junction) to join Fool Creek (west of Skull Ridge) and then turns to flow in a southeast direction to join the north oriented South Tongue River and then to flow as the Tongue River in an east direction to Box Canyon. From Box Canyon the Tongue River flows in a northeast direction to east oriented Tongue Canyon and then turns to flow in a northeast direction to the north edge of figure 5 (near northeast corner). The South Tongue River flows in a north direction from the south edge of figure 5 (west of center) to join the North Tongue River south and west of Skull Ridge. The Little Tongue River originates west of Black Mountain and flows in a north direction to near the highway and then turns to flow in an east and northeast direction to the deep valley between Herdick Ridge and Steamboat Point. The valley turns in a southeast direction although the Little Tongue River disappears as a surface stream until it emerges as a northeast oriented stream and flows to the east edge of figure 5. Disappearance of the Little Tongue River as a surface stream suggests the steep slope is composed of dipping limestone strata. The South Fork Little Tongue River originates east of Black Mountain and flows in a north-northeast direction to join the northeast oriented Little Tongue River near the gaging station at the base of the Bighorn Mountains east flank. Wolf Creek flows in an east and northeast direction from south of Black Mountain to near and around Big Mountain near the southeast corner of figure 5. Study of the Bighorn Mountains upland surface reveals numerous through valleys linking various drainage routes. Some of the most obvious through valleys are located near the crest of the Bighorn Mountains east flank and probably follow the strike of the dipping strata. For example, south and west of Steamboat Point a through valley links a north oriented Tongue River tributary valley with the Little Tongue River valley. This through valley is at least 180 meters deep. West of Herdick Ridge and Horseshoe Mountain a through valley links the Little Tongue River valley with the South Fork Tongue River valley. This through valley is more than 120 meters deep. West of Elephant Foot a 140-meter deep through valley links the South Fork Little Tongue River valley with the Wolf Creek valley. While the orientation of these through valleys was probably determined by the strike of the dipping strata the through valleys are water-eroded features and were eroded by south-southeast oriented flood flow prior to headward erosion of deeper Wolf Creek, South Fork Little Tongue River, and Little Tongue River valleys. Another through valley south of Black Mountain links the north oriented Little Tongue River headwaters valley with the east oriented Wolf Creek headwaters valley. These and other through valleys provide evidence of flood flow channels that once crossed the Bighorn Mountains upland surface. Floodwaters came from north and west of the Bighorn Mountains, which at that time had not emerged as a high mountain range.

Detailed map of Little Tongue River-South Fork Little Tongue River drainage divide area

Figure 6: Detailed map of Little Tongue River-South Fork Little Tongue River 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 Little Tongue River-South Fork Little Tongue River drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 40 feet. The Little Tongue River flows in a north direction from the southwest corner of figure 6 to section 31 (near west center edge of figure 6) and then turns to flow in an east and northeast direction to the north end of Herdick Ridge (near north center edge of figure 6). From the north end of Herdick Ridge the Little Tongue River turns in a southeast direction and then disappears as a surface stream. The Little Tongue River then emerges as a surface stream in section 26 and flows in a northeast direction to the north edge of figure 6 (near northeast corner). The South Fork Little Tongue River flows in a north-northeast direction from the south center edge of figure 6 to join the Little Tongue River near the north edge of figure 6 and does not disappear as a surface stream. Wolf Creek flows in a northeast direction across the southeast corner of figure 6. A through valley west of Herdick Ridge and Horseshoe Mountain links a north-northwest oriented Little Tongue River tributary valley with a southeast oriented South Fork Little Tongue River tributary valley. The through valley floor elevation is between 7440 and 7480 feet. Horseshoe Mountain rises to more than 7920 feet suggesting the through valley is approximately 440 feet deep. Another through valley west of Elephant Foot links a north oriented South Fork Little Tongue River tributary valley with the southeast oriented Sibley Creek valley with Sibley Creek being a barbed Wolf Creek tributary. The floor elevation of this second through valley is between 7480 and 7520 feet. Elephant Rock rises to 8028 feet suggesting this second through valley is approximately 500 feet deep. These two through valleys provide evidence of what was once a south-southeast oriented flood flow channel along the east crest of the present day Bighorn Mountains. As previously stated the flood flow channel orientation in this case was probably governed by the strike of dipping strata. The south-southeast oriented flood flow channel was captured by headward erosion of an east oriented valley along the south side of Tongue Butte and then was captured by headward erosion of the deeper northeast oriented Wolf Creek valley. Next headward erosion of the deep north-northeast South Fork Little Tongue River valley captured the flood flow and beheaded the flood flow to the actively eroding Sibley Creek valley. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented South Fork Little Tongue River valley. The process was repeated again when headward erosion of the deep Little Tongue River valley beheaded the south-southeast oriented flood flow channel. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north-northwest oriented Little Tongue River tributary drainage route. The east-southeast oriented Little Tongue River valley segment (where the Little Tongue River disappears as a surface stream) may reflect a segment of what was once a east-southeast oriented flood flow channel that existed prior to headward erosion of the northeast oriented Little Tongue River valley segments.

Wolf Creek-Big Goose Creek drainage divide area

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

Figure 7 illustrates the Wolf Creek-Big Goose Creek drainage divide area south and east of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 7 is 20 meters. The Bighorn Mountains east flank can be seen near the east edge of figure 7. Elevations near the northeast corner of figure 7 are less than 1400 meters. Except in the deeper valleys elevations on the rugged Bighorn Mountains upland surface are 2500 meters or greater with the highest elevations on Lookout Mountain exceeding 3000 meters. Black Mountain rises to 2892 meters. West Fork South Tongue River flows from near the southwest corner of figure 7 in a north and north-northeast direction to join the north-northwest oriented East Fork and to form the north-northwest oriented South Tongue River, which flows to the north edge of figure 7 (near northwest corner). The Little Tongue River originates west of Black Mountain and flows in a north direction to the north edge of figure 7 (west of center). Wolf Creek originates south of Black Mountain and flows in an east and northeast direction to the north edge of figure 7 (close to northeast corner). Quartz Creek is the north-northeast and north-northwest oriented stream joining Wolf Creek west of Big Mountain. Big Goose Creek flows in a north and northeast direction across the southeast corner area of figure 7. Walker Creek originates at the north end of Walker Prairie and flows in a southeast direction to join Big Goose Creek as a barbed tributary. Note the through valley west of Walker Mountain linking the north-northwest oriented Quartz Creek valley with the southeast oriented Walker Creek valley. The through valley floor elevation is between 2380 and 2400 meters, Walker Mountain to the east rises to 2624 meters and elevations to the west rise much higher suggesting the through valley is approximately 225 meters deep. Other through valleys in the region separate Big Mountain, Little Mountain, Walker Mountain, and She-Bear Mountain and link other Wolf Creek and Big Goose Creek tributary valleys. These through valleys provide additional evidence of southeast oriented flood flow along what is today the eastern edge of the Bighorn Mountains upland surface. Through valleys paralleling the Bighorn Mountains eastern flank are probably following the strike of dipping strata, which probably defined these through valley orientations. However, the through valleys are water-eroded features and were eroded as anastomosing flood flow channels. Through valleys not related to the dipping strata are found further west on the Bighorn Mountains upland surface. One obvious through valley links the north oriented Little Tongue River headwaters valley with the east oriented Wolf Creek headwaters valley and is located on the southwest side of Black Mountain.  The through valley floor elevation is between 2640 and 2660 meters. Black Mountain to the north rises to 2892 meters and the hill immediately south of the through valley rises to more than 2740 meters, but Lookout Mountain further to the south rises to 3093 meters. Depending on which elevations are used and how the through valley is defined the through valley could be anywhere from 80 to 230 meters deep. The latter depth assumes the through valley was eroded into an erosion surface at least as high as the tops of Lookout Mountain and Black Mountain.

Detailed map of Little Tongue River-Wolf Creek drainage divide area

Figure 8: Detailed map of Little Tongue River-Wolf 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 Little Tongue River-Wolf Creek drainage divide seen in less detail in figure 7. The map contour interval for figure 8 is 40 feet. Black Mountain is the labeled high point in the north center area of figure 8 and rises to 9489 feet. The Little Tongue River originates in section 18 on the southwest side of Black Mountain and flows in a north-northwest and north direction to the north edge of figure 8 (west of center). North of figure 8 the Little Tongue River turns to flow in an east and northeast direction. Wolf Creek originates near the corner of sections 17, 18, 19, and 20 south of Black Mountain and flows in an east direction to the east center edge of figure 8. A northwest to southeast oriented through valley in the southeast corner of section 18 links the north-northwest oriented Little Tongue River headwaters valley with the east oriented Wolf Creek headwaters valley. The through valley floor elevation is between 8680 and 8720 feet. Elevations along the south center edge of figure 8 rise to almost 9200 feet and south of figure 8 rise to more than 9600 feet. These elevations suggest the Little Tongue River-Wolf Creek through valley is more than 750 feet deep. The through valley is a water-eroded valley and was eroded by south oriented flood flow moving from the present day north oriented Little Tongue River valley to what at that time was the actively eroding east oriented Wolf Creek valley. The south oriented flood flow channel was beheaded by headward erosion of the much deeper east and northeast oriented Little Tongue River valley (north of figure 8). Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented Little Tongue River headwaters drainage route. Other somewhat shallower and less obvious through valleys can be seen in figure 8 linking other present day drainage routes. These other through valleys define what was once a maze of anastomosing flood flow channels that was systematically dismembered as deeper valleys eroded headward into the region to capture the south oriented flood flow.

East Fork South Tongue River-Big Goose Creek drainage divide area

Figure 9: East Fork South Tongue River-Big Goose Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the East Fork South Tongue River-Big Goose Creek drainage divide area south of figure 7 and includes a significant overlap area with figure 7. The dashed line in the southwest quadrant of figure 9 is the present day Tongue River-Bighorn River drainage divide and is also a county line. In the southwest corner of figure 9 streams flow to northwest and west-southwest oriented Shell Creek (not seen in figure 9), which joins the north oriented Bighorn River in the Bighorn Basin. The East Fork Big Goose Creek flows from Park Reservoir (near southeast corner of figure 9) in a north direction to the northeast quadrant of figure 9 where it joins the north and northeast oriented West Fork Big Goose Creek to form northeast oriented Big Goose Creek, which flows to the north edge of figure 9 (near northeast corner). The West Fork Big Goose Creek flows in a north direction from the south edge of figure 9 (near center) to Dome Lake and Dome Lake Reservoir, and then flows in a north and northeast direction to join north oriented East Fork Big Goose Creek. Sawmill Creek is a southeast and east oriented tributary to West Fork Big Goose Creek and is located near the center of figure 9. Lookout Mountain is located north of the southeast oriented Sawmill Creek headwaters. The East Fork South Tongue River originates immediately west of an east-oriented Sawmill Creek tributary headwaters and flows in a west and north-northwest direction to join the northeast oriented West Fork South Tongue River near the northwest corner of figure 9 and to form the north oriented South Tongue River, which then flows to the north edge of figure 9 (near northwest corner). A well-defined west to east oriented through valley links the west oriented East Fork South Tongue River headwaters valley with the east oriented Sawmill Creek tributary valley. The map contour interval for figure 9 is 20 meters and the through valley floor elevation is between 2920 and 2940 meters. The unnamed ridge immediately to the north of the through valley rises to more than 3100 meters. Dome Peak to the south rises to 3300 meters. These elevations suggest the through valley is approximately 160 meters deep. Note directly north of the unnamed ridge north of the through valley there additional through valleys linking the west oriented Mohawk Creek and west-northwest oriented Graves Creek valley with the southeast oriented Sawmill Creek headwaters valley. Also note Rock Chuck Pass south of the East Fork South Tongue River-Sawmill Creek through valley. These through valleys are what remains today of anastomosing flood flow channels that were eroded into a high level erosion surface as what is now the Bighorn Mountains upland surface was formed. Floodwaters were flowing in a south direction on the present day north oriented East Fork South Tongue River alignment and were captured by headward erosion of the east oriented Sawmill Creek tributary valley. Prior to being captured the south oriented flood flow had been moving across Woodchuck Pass (between Bruce Mountain and Dome Peak) to a southeast oriented flood flow channel on the present day northwest oriented Shell Creek alignment (south and west of figure 9). It is possible floodwaters crossed Woodchuck Pass after flood flow on the Shell Creek alignment had been beheaded and reversed to create the northwest oriented Shell Creek drainage route.

Detailed map of East Fork South Tongue River-Sawmill Creek drainage divide area

Figure 10: detailed map of East Fork South Tongue River-Sawmill 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 East Fork South Tongue River-Sawmill Creek drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 40 feet. Lookout Mountain in the northeast corner of section 18 has an elevation of 10,147 feet. The East Fork South Tongue River originates in the northeast corner of section 30 (near south center edge of figure 10) and flows in a west, northwest and north-northwest direction to the north edge of figure 10 (near northwest corner). Sawmill Creek originates in the southeast corner of section 18 (south of Lookout Mountain) and flows in a southeast direction to the east edge of figure 10 (near southeast corner). An east oriented Sawmill Creek tributary originates in the north half of section 29 (directly east of the west oriented East Fork South Tongue River headwaters) and flows in an east direction to join Sawmill Creek in the southwest corner of section 22. A through valley near the corner of sections 19, 20, 29, and 30 links the east oriented Sawmill Creek tributary valley with the west oriented East Fork South Tongue River headwaters valley. The through valley elevation is shown as being 9358 feet. Elevations south of figure 10 are higher than the top of Lookout Mountain, which means the through valley is at least 800 feet deep. Other somewhat shallower through valleys in figure 10 include a northwest to southeast oriented through valley in section 18 linking the northwest oriented Graves Creek valley with the southeast oriented Sawmill Creek valley and a through valley near the corner of sections 17, 18, 19, and 20 linking the west oriented Mohawk Creek valley with the Sawmill Creek valley. Graves Creek and Mohawk Creek are East Fork South Tongue River tributaries. The through valleys were eroded by south and east oriented flood flow moving on the present day north oriented East Fork South Tongue River and South Tongue River alignment to an actively eroding southeast oriented valley on the Sawmill Creek alignment. Headward erosion of the much deeper east and northeast oriented Tongue River valley north of figure 10 beheaded the south oriented flood flow channel. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented South Tongue River and East Fork South Tongue River drainage routes and ended flood flow across the region 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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