Abstract:

This essay uses topographic map evidence to interpret landform origins in the region between Wind River and Sweetwater River tributaries along the Beaver Divide in Wyoming. The Beaver Divide is a major escarpment marking the boundary between the deeper Wind River Basin to the north and west and the higher elevation Sweetwater River drainage basin to the south and east. The Sweetwater River flows in a northeast and east direction south and east of the Beaver Divide rim. Deep north oriented indentations in the Beaver Divide escarpment are interpreted as abandoned north oriented headcuts eroded by north oriented flood flow moving into the Wind River Basin. The north oriented flood flow was a reversal of what had initially been south oriented flood flow across the region. The south oriented flood flow was derived from the western margin of a thick North American ice sheet and was flowing from western Canada to and across Wyoming. At that time mountain ranges had not emerged and mountain range emergence occurred as floodwaters deeply eroded surrounding regions and as ice sheet related crustal warping raised mountain ranges relative to adjacent areas. The massive flood flow reversal occurred when ice sheet melting opened up space at the south end of the deep “hole” the ice sheet had occupied and the deep northeast oriented Yellowstone River valley eroded headward from that newly opened up space across Montana to capture south oriented floodwaters in Montana. Flood flow routes to Wyoming were beheaded in sequence from east to west and floodwaters on north ends of beheaded flood flow routes reversed flow direction to flow in a north direction to the much deeper northeast oriented Yellowstone River valley. These newly formed north oriented drainage routes captured south oriented flood flow still moving west of the actively eroding Yellowstone River valley head. The north oriented abandoned headcuts, which today make up the Beaver Divide escarpment, were eroded by huge volumes of north oriented floodwaters moving to a newly beheaded and reversed flood flow channel on the Wind River Canyon-Bighorn River alignment. The north oriented flood flow deeply eroded the present day Wind River Basin. At least some of the north oriented flood flow responsible for eroding the Beaver Divide escarpment and Wind River Basin crossed the southeast end of the present day Wind River Mountains and then was captured by headward erosion of the Sweetwater River valley and Beaver Creek valley and diverted in southeast directions along the Wind River Range southwest margin before turning to flow in a northeast and north direction into what was at that time the rapidly eroding Wind River Basin. Wind River Range emergence and headward erosion of the deep southeast oriented Wind River valley beheaded all south oriented flood flow routes across the Wind River Range. At the same time headward erosion of the east oriented Sweetwater River valley from the North Platte River valley captured the northeast oriented flood flow moving in the southeast and northeast oriented Sweetwater River valley to the west and ended all north oriented flood flow movements across the Beaver Divide escarpment.

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 Wind River-Sweetwater River drainage divide area landform origins along the Beaver Divide, Wyoming, Fremont County, 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 Wind River-Sweetwater River drainage divide area landform evidence along the Beaver Divide will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Wind River-Sweetwater River drainage divide area location map

Figure 1: Wind River-Sweetwater 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 Wind River-Sweetwater River drainage divide area along Beaver Divide and illustrates a region in west-central Wyoming. Togwotee Pass is located near the northwest corner of figure 1. The Wind River originates near Togwotee Pass and flows in a southeast direction between the Owl Creek Mountains and Wind River Range into the Wind River Basin and at Riverton turns to flow in a northeast and north direction to Boysen Reservoir. At Boysen Reservoir the Wind River enters Wind River Canyon, which crosses the east end of the Owl Creek Mountains and flows in a north direction to enter the Bighorn Basin near Thermopolis. When the Wind River enters the Bighorn Basin the river name changes to become the Bighorn River, which then flows in a north direction to the north edge of figure 1 with water eventually reaching Montana and the northeast oriented Yellowstone River. Muskrat Creek is a north, northwest, and west oriented Wind River tributary originating near the Granite Mountains and joining the Wind River north of Riverton. Casper is a city located in the east center area of figure 1. The Laramie Mountains extend in a southeast and south direction from Casper to the southeast corner of figure 1. The North Platte River flows in a north direction from the south edge of figure 1 (east half and west of the Laramie Mountains) to Seminoe, Pathfinder, and Alcova Reservoirs and then flows in a north-northeast and northeast direction to Casper. At Casper the North Platte River turns to flow in an east direction along the Laramie Mountains north flank before turning to flow in a south and east direction to the east center edge of figure 1. East of figure 1 the North Platte River flows in a southeast direction into Nebraska and to the east oriented Platte River. The Sweetwater River originates near the southeast end of the Wind River Range and flows in a south direction to the Wind River Range southwest flank where it then flows in a southeast direction to near South Pass. From South Pass the Sweetwater River flows in an east-northeast direction to the Granite Mountains and then in an east direction to Pathfinder Reservoir, where the flooded Sweetwater River valley turns in a south direction to join the north oriented North Platte River as a barbed tributary. West of the north oriented North Platte River and south of the Sweetwater River are the Ferris and Green Mountains and further south is the Great Divide Basin. West of the Great Divide Basin is the south oriented Green River drainage basin with the Green River flowing to the Colorado River south of figure 1. The Wind River-Sweetwater River drainage divide area along Beaver Divide investigated in this essay extends from near the Wind River Range east end to near the Muskrat Creek headwaters.

Wyoming drainage routes seen in figure 1 developed during immense melt water floods, which initially flowed from the western margin of a thick North American ice sheet in western Canada to and across Wyoming. At first present day mountain ranges did not exist and floodwaters could freely across what are today massive mountain barriers. Mountain ranges emerged as floodwaters deeply eroded surrounding regions and as ice sheet related crustal warping raised the mountain ranges relative to the adjacent areas. Ice sheet related crustal warping combined with deep glacial erosion also created a deep “hole” in which the huge ice sheet was located. At first floodwaters flowed in a south directions and deep south oriented flood flow channels eroded headward on both sides of the emerging Laramie Mountains. The western flood flow channel was located between the emerging Laramie Mountains and the emerging Rattlesnake Hills while the eastern flood flow channel, which was deeper, eroded headward along the Laramie Mountains northeast flank and then along the Laramie Mountains north flank. Upon reaching the northwest end of the emerging Laramie Mountains uplift the deeper east and southeast oriented flood flow channel eroded headward in a northeast direction across the south and southeast oriented flood flow moving to the south oriented flood flow channel west of the Laramie Mountains and captured that flood flow. Floodwaters on the north end of the beheaded western flood flow channel reversed flow direction to create the north oriented North Platte River route west of the Laramie Mountains. Ice sheet related crustal warping that was raising Wyoming and Colorado mountain ranges also played a role in the reversal of flood flow in the North Platte River valley west of the Laramie Mountains. Prior to North Platte River reversal the east oriented Sweetwater River valley had begun to erode headward from the south oriented flood flow channel to capture south oriented flood flow moving across the emerging Rattlesnake Hills and the Granite Mountains. Following the reversal of flow direction in the North Platte River valley floodwaters from further west were captured by the Sweetwater River valley as it eroded headward to capture floodwaters west of the Granite Mountains.

West of the Rattlesnake Hills and Granite Mountains large volumes of south oriented flood flow were moving from the Bighorn Basin across the emerging Owl Creek Mountains and then southward across the present day Wind River Basin to the Great Divide Basin and then south into Colorado to the actively eroding Colorado River valley. While floodwaters flowed across all regions seen in figure 1 floodwaters became concentrated along the present day north oriented Wind River Canyon alignment and then further south in the region between the east end of the emerging Wind River Range and the west ends of the emerging Green Mountains and Granite Mountains. The present day north oriented Wind River-Bighorn River drainage route developed during a massive flood flow reversal triggered by headward erosion of the deep northeast oriented Yellowstone River valley from space at the south end of the deep “hole” the melting ice sheet had occupied and that was being opened up by ice sheet melting. Headward erosion of the deep Yellowstone River valley captured the south oriented flood flow routes to Wyoming in sequence from east to west. Floodwaters on north ends of beheaded flood flow routes reversed flow direction to flow to the much deeper Yellowstone River valley and in doing so captured floodwaters still moving in a south direction west of the actively eroding Yellowstone River valley head. When Yellowstone River valley headward erosion beheaded a south oriented flood flow channel supplying floodwaters to the concentrated south oriented flood flow channel moving floodwaters on the present day Wind River Canyon alignment there was a massive reversal of flood flow that created the north oriented Bighorn River and Wind River drainage route, which captured southeast oriented flood flow channels from further to the west including floodwaters still moving across the southeast end of the emerging Wind River Range. These captured floodwaters flowed in southeast and north directions around the Wind River Range east end and then into the Wind River Basin as they headed to the north oriented Wind River Canyon drainage route to reach the much deeper Yellowstone River valley. As these floodwaters flowed in a north direction into the Wind River Basin they deeply eroded the Wind River Basin floor and the Beaver Divide escarpment eroded headward as a series of  giant headcuts. Headward erosion of the deep southeast oriented Wind River valley (upstream from Riverton) and Wind River Range emergence beheaded the flood flow routes across the southeast end of the Wind River Range, which had been captured by headward erosion of the Sweetwater River valley. Today Beaver Divide is a giant abandoned headcut and  it exists as an erosional landform feature and can be explained in the context of massive flood flow reversal.

Detailed location map for Wind River-Sweetwater River drainage divide area

Figure 2: Detailed location map Wind River-Sweetwater 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 Wind River-Sweetwater River drainage divide area along Beaver Divide. The green colored area is National Forest land in the Wind River Range. The brown colored area is Wind River Indian Reservation land. Riverton is located near the east end of the Wind River Indian Reservation. The Wind River flows in a southeast direction from north edge of figure 2 (west half) to Riverton and then turns to flow in a northeast and north direction to Boysen Reservoir (straddling the north center edge of figure 2). North of Boysen Reservoir and north of figure 2 the Wind River enters north oriented Wind River Canyon to flow from the Wind River Basin to the Bighorn Basin. In the Bighorn Basin the Wind River name changes to become the Bighorn River with water eventually reaching the northeast oriented Yellowstone River. The Popo Agie River originates in the Wind River Range and flows in a northeast direction from Lander to Riverton to join the northeast oriented Wind River near Riverton. Beaver Creek originates near the east end of the Wind River Range and flows in an east-southeast direction near the town of Miners Delight and then turns to flow in a north and northwest direction to join the Poop Agie River south of Riverton. Sand Draw is a northwest oriented Beaver Creek tributary near the town of Sand Draw. East of Sand Draw Logan Gulch originates near Findlay Springs and flows in a north direction to join northwest oriented Muskrat Creek, which joins the north oriented Wind River at the Boysen Reservoir south end. Muskrat Creek originates north of the Granite Hills west end and flows in a north direction before turning to flow in a northwest and west direction to join the north oriented Wind River. Muskrat Creek has many north oriented tributaries originating at or near Beaver Divide. The Sweetwater River originates in the Wind River Range west of figure 2 and flows in a south and southeast direction to near the South Pass (near southwest corner of figure 2). At South Pass the Sweetwater River turns to flow in an east-northeast direction to near the town of Sweetwater Station and then turns to flow in an east direction to the Granite Mountains and then to the east edge of figure 2. East of figure 2 the Sweetwater River flows to the north, east, and southeast oriented North Platte River. Buffalo Creek is a south oriented Sweetwater River tributary located south of the Muskrat Creek headwaters and at the Granite Mountains west end. West of Buffalo Creek is Long Creek, which flows in a south direction south of the Logan Gulch headwaters near Findlay Springs. Beaver Divide is the drainage divide between north-oriented Wind River tributaries in the Wind River Basin and south-oriented Sweetwater tributaries. West of Sweetwater Station the east oriented Sweetwater River and  east and north oriented Beaver Creek are relatively close together, although they end up flowing in completely different directions.

Muskrat Creek-Sweetwater River drainage divide area

Figure 3: Muskrat Creek-Sweetwater River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of Muskrat Creek-Sweetwater River drainage divide area. The map contour interval for figure 3 is 20 meters. Muskrat Basin is located near the center of figure 3 and is where Muskrat Creek originates. Muskrat Creek flows in a northeast and north direction from Muskrat Basin to the north edge of figure 3 (slightly west of center). Cottonwood Draw in a northeast oriented drainage route in the north center area of figure 3 and drains to Muskrat Creek north of figure 3. North of figure 3 Muskrat Creek flows in a north, northwest, and west direction to join the north oriented Wind River with water eventually reaching the northeast oriented Yellowstone River. Beaver Divide is the drainage divide defined by the escarpment rimming Muskrat Basin and extends from the northwest corner of figure 3 in an east-southeast and south-southeast direction to Muskrat Basin and then in an east-northeast and north-northeast direction to the northeast corner of figure 5. Beaver Divide extends in a northeast direction from the northeast corner of figure 3 almost to the Rattlesnake Hills to the northeast and westward from the northwest corner of figure 3 in a southwest and west direction almost to the Wind River Range. The south oriented “Creek” originating west of the south-southeast oriented Beaver Divide segment is Buffalo Creek, which flows to the south edge of figure 3 (west half) and south of figure 3 Buffalo Creek flows to the east oriented Sweetwater River. Southeast oriented Tin Cup Creek near the southwest corner of figure 3 joins Buffalo Creek near the south edge of figure 3. Black Rock Draw is a south oriented Sweetwater River tributary flowing through Black Rock Gap near the south center edge of figure 3. Diamond Springs Draw is the south-southwest and southwest oriented Sweetwater River tributary near the east edge of figure 3. Note how a through valley links the north oriented Muskrat Creek valley with the south oriented Buffalo Creek valley. The through valley floor elevation at the drainage divide is between 2080 and 2100 meters. Beaver Divide elevations to the northwest rise to more than 2240 meters and to the northeast (near the northeast corner of figure 3) elevations rise to 2218 meters. These elevations suggest the through valley is approximately 120 meters deep. The through valley was probably initially eroded by south oriented flood flow, but the escarpment surrounded Muskrat Basin suggests the final flood flow movement was in a north direction. The best explanation for the escarpments surrounding Muskrat Basin is they were formed as large north oriented headcut by huge sheets of north oriented flood flow moving into the deeper Wind River Basin. The floodwaters came from south of figure 3 and the Sweetwater River may have delivered at least some of the flood flow. If so the floodwaters were coming from what is now the Wind River Range southeast end, which means the Wind River Range had not fully emerged at the time Muskrat Basin was eroded.

Detailed map of Muskrat Creek-Buffalo Creek drainage divide area

Figure 4: Detailed map of Muskrat Creek-Buffalo 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 Muskrat Creek-Buffalo Creek drainage divide area seen in less detail in figure 3. The map contour interval for figure 4 is 20 feet. Muskrat Basin is labeled and is surrounded by the east-facing Beaver Divide escarpment to the west and by the northwest-facing Beaver Divide escarpment to the south and east. Muskrat Creek originates in section 12 and flows in a northeast direction to the north edge of figure 4. North of figure 4 Muskrat Creek flows in a north, northwest, and west direction to the north oriented Wind River with water eventually reaching the northeast oriented Yellowstone River. Buffalo Creek can be seen flowing in a south-southwest, south-southeast and south direction near the west edge of figure 4 and south of figure 4 flows to the east oriented Sweetwater River with water eventually reaching the north, northeast, east, and southeast oriented North Platte River. Black Rock Draw flows in a south-southwest direction in the east half of figure 4 and south of figure 4 also flows to the east oriented Sweetwater River. The steep Beaver Divide escarpment surrounding Muskrat Basin is more than 100 feet high and elevations decrease although at a more gradual rate as one proceeds into Muskrat Basin. A (hanging) through valley links the northeast oriented Muskrat Creek headwaters valley with  south and south-southwest oriented Buffalo Creek tributary valleys and represents a low point on the crest of the Beaver Divide escarpment east of the corner of sections 11, 12, 13, and 14. The through valley floor elevation is between 6840 and 6860 feet. Elevations along the Beaver Divide escarpment crest rise in both directions with elevations near the north edge of figure 4 (west half) being greater than 7200 feet and elevations in section 8 (near east edge) being greater than 6900 feet. North and east of figure 4 elevations along the Beaver Divide escarpment rise to more than 7200 feet. Depending on how the through valley is viewed it could be anywhere from 40 to more than 340 feet deep. The through valley was eroded first by south and southeast oriented flood flow at a time when the deep Wind River Basin north of Beaver Divide did not exist. Next there was a massive reversal of flood flow to erode the Wind River Basin and the north oriented Beaver Divide headcut. Finally headward erosion of the Sweetwater River valley captured the north oriented flood flow and floodwaters south of the newly eroded Beaver Divide escarpment flowed in a south direction to the Sweetwater River valley.

Buffalo Creek-Sweetwater River drainage divide area

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

Figure 5 illustrates the Buffalo Creek-Sweetwater River drainage divide area south and west of figure 3 and there is an overlap area with figure 3. The map contour interval for figure 5 is 20 meters. The western end of the Granite Mountains is is seen in figure 5. The Sweetwater River flows from the west center edge of figure 5 in a southeast direction to near the south edge of figure 5 and then flows in an east direction to the east edge of figure 5 (near southeast corner). East of figure 5 the Sweetwater River flows to the north, northeast, east, and southeast oriented North Platte River. Long Creek is the southeast and west oriented stream joining the Sweetwater River near the west edge of figure 5. Buffalo Creek flows in a south direction from the north center edge of figure 5 to Stampede Meadow and then turns to flow to Stampede Bog and finally continues in a southeast and south direction toward the Sweetwater River. The Buffalo Creek route is shown with discontinuous lines suggesting Buffalo Creek rarely flows along those route segments. Black Rock Draw drains in a south direction from the north edge of figure 5 (east half) to Black Rock Gap and then turns to drain in southeast direction to the east center edge of figure 5. East of figure 5 Black Rock Draw drains to the Sweetwater River. Note how the Sweetwater River and Buffalo Creek have eroded valleys or water gaps across some of the Granite Mountains upland areas. An excellent Sweetwater River water gap can be seen in section 31 near the south edge of the southeast quadrant of figure 5. The Sweetwater River valley floor elevation in the water gap is between 1900 and 1920 meters. Elevations on either side of the water gap rise to more than 2040 meters suggesting the water gap is at least 120 meters deep. Quaking Asp Gap to the northeast of the water gap is one of many wind gaps seen in the Granite Mountains. Northeast to southwest oriented wind gaps link the Buffalo Creek valley at Stampede Meadow and at Stamped Bog with the Sweetwater River valley. These wind gaps are more than 140 meters deep and were eroded by parallel flood flow channels. Floodwaters could have first been moving in a southwest direction before the flood flow reversal, but then were reversed to flow in a northeast direction to the north oriented Buffalo Creek and Black Rock Draw valley and then north to erode the north oriented Muskrat Basin headcut. Headward erosion of the east oriented Sweetwater River valley captured the northeast oriented flood flow. The water gap in section 31 suggests there was more than 120 meters of erosion surrounding the Granite Mountains upland areas as the Sweetwater River valley eroded headward across the region to capture the north oriented flood flow, which resulted in a second reversal of the reversed flood flow to create the south oriented Buffalo Creek and Black Rock Draw drainage routes.

Detailed map of Buffalo Creek-Sweetwater River drainage divide area

Figure 6: Detailed map of Buffalo Creek-Sweetwater 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 Buffalo Creek-Sweetwater River drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 20 feet. The Sweetwater River flows in a southeast direction across the southwest corner of figure 6. Buffalo Creek flows in a southeast direction across the northeast corner of figure 6. Stampede Meadow is north of the north center edge of figure 6 and north of Stamped Meadow Buffalo Creek flows in a south direction (see figure 5). A through valley in the northwest corner of section 19 links a northeast oriented Buffalo Creek tributary valley with a south-southwest oriented Sweetwater River tributary valley. The through valley floor elevation is shown as being 6601 feet. Elevations in the southeast corner of section 19 rise to 7221 feet and elevations in the northwest quadrant of section 13 to the northwest rise to 7166 feet. These elevations suggest the through valley is at least 565 feet deep. South of figure 6 and not seen in this essay is Crooks Gap, which today is a deep north oriented water gap eroded between the Green Mountains to the east and Crooks Mountain to the west. Through valleys south of Crooks Mountain link a northwest oriented Sweetwater River tributary valley with north and northeast oriented Crooks Creek, which joins the Sweetwater River east of figure 6. The through valley and water gap suggest flood flow still moving in south and southeast directions west of Crooks Mountain was captured by the reversal of flood flow at Crooks Gap and diverted to flow in a north direction. At that time the Sweetwater River valley probably did not exist and the north oriented floodwaters flowed across the region in figure 6 to the Muskrat Basin and then flowed to the north oriented Wind River and Bighorn River with water flowing to space in the deep “hole” being opened up by ice sheet melting. Headward erosion of the deep Sweetwater River valley and northeast oriented tributary valleys next captured the north oriented flood flow and diverted the floodwaters in an east direction to the north, northeast, east, and southeast oriented North Platte River valley.

Logan Gulch-Long Creek drainage divide area

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

Figure 7 illustrates the Logan Gulch-Long Creek drainage divide area west and north of figure 3 and includes an overlap area with figure 3. The map contour interval for figure 7 is 20 meters in the east half and is 50 meters in the west half. Beaver Divide is located along the crest of a north-facing escarpment from Findlay Spring (near center of figure 7) to the east edge of figure 7. North of Findlay Spring Beaver Divide is the crest of an east-facing escarpment to near Rock Creek Mountain (in north center area of figure 7). West of Rock Creek Mountain the Beaver Divide orientation changes to become the crest of a north, west, and northwest-facing escarpment. Logan Gulch originates at Findlay Spring and drains in a north-northeast direction to the north edge of figure 7 (east of center) and north of figure 7 water in Logan Gulch If there is enough) eventually reaches Muskrat Creek and the north oriented Wind River. The West Fork Long Creek originates near the west edge of figure 7 (south half) and flows in an east-northeast and east direction almost to Findlay Spring where it turns to flow in a south-southwest and south-southeast direction to the south center edge of figure 7. The East Fork Long Creek flows in a southwest direction from near the east center edge of figure 7 to the south edge of figure 7 (south of Long Creek Mountain) and joins the West Fork Long Creek south of figure 7 to form Long Creek. South of figure 7 Long Creek flows in a southeast direction to join the east oriented Sweetwater River (as seen in figure 5). The indentation in the Beaver Divide escarpment near Findlay Spring appears to be another abandoned headcut. Flood flow responsible for eroding the north oriented headcut would have moved in a north direction on the present day north oriented West Fork Long Creek alignment and possibly in an east-northeast direction on the present day east-northeast oriented West Fork Long Creek alignment and would have been flowing to the reversed flood flow moving north through Wind River Canyon to eventually reach space at the south end of the deep “hole” that had been opened up by ice sheet melting (and which was being drained in a south direction across eastern Nebraska). Prior to the reversal of flood flow floodwaters had been flowing in a south direction across the region in figure 7, although at that time the Wind River Basin had not been eroded and elevations north of Beaver Divide were higher than elevations south of Beaver Divide. The 50-meter contour interval makes it difficult to determine whether a through valley links the north-northeast oriented Logan Gulch valley with the south oriented Long Creek valley. Figure 8 provides a more detailed topographic map of the Logan Gulch-Long Creek drainage divide area so we can check to make sure a through valley exists.

Detailed map of Logan Gulch-Long Creek drainage divide area

Figure 8: Detailed map of Logan Gulch-Long 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 Logan Gulch-Long Creek drainage divide seen in less detail in figure 7 above. The map contour interval for figure 8 is 20 feet. Findlay Spring is located north of the south center edge of figure 8 and at the head of the deep indentation into the Beaver Divide escarpment. The West Fork Long Creek flows from the west edge of figure 8 (near southwest corner) almost to Findlay Spring and then turns to flow in a south direction to the south edge of figure 8 (slightly west of center). A north-northeast oriented drainage route originates at Findlay Spring and drains to the north edge of figure 8 (east half). Logan Gulch is the north-northeast oriented drainage route immediately west of that Findlay Spring originated drainage route and also drains to the north edge of figure 8. Logan Gulch water eventually reaches Muskrat Creek and the north oriented Wind River. A well-defined through valley does link the east and south oriented Long Creek valley with the north-northeast oriented Findlay Spring originated drainage route valley. The through valley floor elevation is between 6860 and 6880 feet. Beaver Divide crest elevations east of the through valley and seen in figure 8 rise to more than 7120 feet and west and north of the through valley rise to 7353 feet. East of figure 8 Beaver Divide elevations rise to 7362 feet. These elevations suggest the through valley could be as much 470 feet deep with a 200-foot deep inner channel linking the West Fork Long Creek valley with the Logan Gulch valley. The west wall of the broader through valley representing the upper 270 feet of the through valley depth is the north-northeast to south-southwest upper escarpment extending from the north edge of figure 8 (just west of the Beaver Divide escarpment) to near the southwest corner of figure 8 (the West Fork Long Creek valley crosses this upper escarpment). The east wall of the broader through valley is located east of figure 8 and is not as sharply defined. The upper 270-foot deep through valley was probably eroded by south oriented flood flow moving from the Wind River Basin to the north to the Crooks Gap area to the south at a time before flood flow was reversed and when the deep Wind River Basin did not exist. The 200-foot deep inner and lower through valley was probably eroded by reversed flood flow moving into the Wind River Basin. This north oriented flood flow was responsible for eroding the Beaver Divide escarpment as seen on figure 8 and it eroded what is now the abandoned headcut seen in the Findlay Spring area. At least some of the flood flow responsible for eroding the headcut came from west of figure 8 along the West Fork Long Creek alignment. Headward erosion of the deeper east oriented Sweetwater River valley south of figure 8 captured the east oriented flood flow on the West Fork Long Creek alignment and ended flood flow to the north-northeast oriented Logan Gulch valley.

Beaver Creek-Sweetwater River drainage divide area

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

Figure 9 illustrates the Beaver Creek-Sweetwater River drainage divide area south and west of figure 7 and there is a small overlap area with figure 7. The map contour interval for figure 9 is 50 meters. Beaver Creek flows in a north and west direction around Schoettlin Mountain (in southwest corner of figure 9) and then in a north-northeast direction to the north edge of figure 9 (west half). North of figure 9 Beaver Creek flows to the northeast oriented Popo Agie River, which in turn flows to the northeast and north oriented Wind River with water eventually reaching the northeast oriented Yellowstone River. The Sweetwater River flows in an east-northeast direction across the southeast corner of figure 9 and east of figure 9 eventually reaches the north, northeast, east, and southeast oriented North Platte River. Beaver Divide extends in a northeast direction from near the southwest corner of figure 9 to the north edge of figure 9 and is at the crest of a northwest-facing escarpment. The Beaver Divide escarpment ends at the north oriented Beaver Creek valley near the southwest corner of figure 9, although it extends in a north and east direction from figure 9 almost to the Rattlesnake Mountains. West of figure 9 is the southeast end of the Wind River Range. Beaver Creek originates in the southeast Wind River Mountains and flows in an east-southeast direction to just south of Schoettlin Mountain where Beaver Creek turns to flow in a north direction into figure 9. Beaver Creek headwaters in the Wind River Range are linked by through valleys with east and northeast Popo Agie River tributary valleys. Those through valley floor elevations are today approximately 900 meters higher than the Beaver Creek valley floor elevation near the southwest corner of figure 9.  South of Schoettlin Mountain the south, southeast, and northeast oriented Sweetwater River emerges from the mouth of a 100-200-meter deep canyon. The Sweetwater River originates in the Wind River Range west of the Beaver Creek headwaters and is linked by even higher elevation through valleys with Popo Agie River headwaters valleys. Beaver Divide as seen in figure 9 is the east half of an abandoned headcut eroded by north or north-northeast oriented flood flow moving into the Wind River Basin. The flood flow appears to have been derived from the Beaver Creek and/or Sweetwater River headwaters areas in what is today the Wind River Range southeast end. Apparently at the time the Beaver Divide escarpment was eroded as flood flow across the Wind River Basin north of figure 9 was reversed to flow in a north direction through Wind River Canyon the Wind River Range had not emerged and/or the southeast oriented Wind River valley upstream from Riverton had not been eroded. South oriented flood flow west of the reversed flood flow route on the Wind River Canyon alignment was apparently able to flow across the Wind River Range southeast end where it was captured by headward erosion of the Sweetwater River valley and then by headward erosion of the east-southeast oriented Beaver Creek valley. The captured flood flow then flowed to south of Scheottlin Mountain and where the floodwaters turned to flow in a north direction to eventually reach Wind River Canyon. Again, prior to the north oriented flood flow the region seen in figure 9 was crossed by south oriented flood flow. The 50-meter contour interval hides many topographic details and figure 10 provides a detailed topographic map of the are north and east of Devils Gap and Dishpan Butte to better illustrate erosional features along Beaver Divide. Government Meadows Draw is the south and southwest oriented Sweetwater River tributary in the east half of figure 9.

Detailed map Beaver Creek-Government Meadows Draw drainage divide area

Figure 10: Detailed map of Beaver Creek-Government Meadows Draw 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 Beaver Creek-Government Meadows Draw drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 20 feet. The Beaver Divide escarpment extends from the south edge of figure 10 (west half) to the north edge of figure 10 (east half) and marks the boundary between the deeper Beaver Creek (Wind River) drainage basin to the west and the north and the higher elevation Sweetwater River drainage basin to the east and south. The south-southwest facing escarpment extending from Beaver Divide (at the north edge of figure 10) to the Cedar Rim Draw is Cedar Rim. Dishpan Butte is located in section 29 and stands more than 200 feet above the surrounding surface. The butte to the west along the Beaver Divide escarpment rises even higher and is almost 200 feet higher than Dishpan Butte. The west-facing Beaver Divide escarpment in section 24 is almost 1200 feet high. Devils Gap near the east margin of section 25 is a narrow and deep through valley eroded across the Beaver Divide crest. Devils Gap appears to have been eroded by southeast oriented flood flow moving from what is today the much deeper Beaver Creek drainage basin. A similar but broader through valley crossing the Beaver Divide crest is seen in section 36 to the south of Devils Gap. But, the most intriguing and broadest through valley crossing the Beaver Divide escarpment crest is located between Dishpan Butte and Cedar Rim. The Cedar Rim escarpment in sections 2 and 3 is approximately 250 feet high and marks the north-northeast wall of what was once a major flood flow channel. Government Meadows Draw on the floor of the former flood flow channel drains today in a south-southwest and southeast direction to the Sweetwater River valley south of figure 10 and indicates the final direction of flood flow movement. That final flood flow movement probably followed the reversal of flood flow in the Wind River Basin, which caused large volumes of flood flow to move in north direction on the Beaver Creek alignment and which eroded the deep north oriented Beaver Creek drainage basin so as to create the Beaver Divide escarpment as the west wall of huge north oriented headcut. During that flood flow reversal it is possible there was north oriented flood flow in the broad through valley between Dishpan Butte and Cedar Rim prior to a second flood flow reversal that reversed the north oriented floodwaters to create the south-southwest and southeast Government Meadows Draw drainage route.

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.