Abstract:

This essay uses topographic map evidence to interpret landform origins in the region between Popo Agie River and the Sweetwater River at the Wind River Range southeast end, Wyoming. The Popo Agie River flows in a northeast direction from the Wind River Range to the Wind River Basin where it joins the north oriented Wind-Bighorn River, which flows to Montana and the northeast oriented Yellowstone River. The Sweetwater River originates in the Wind River Range and flows in a south, south-southeast, and southeast direction before turning to flow in an east-northeast and east direction to join the north, northeast, east, and southeast oriented North Platte River. A north to south oriented through valley links the north oriented Middle Popo Agie River headwaters valley with the south oriented Sweetwater River headwaters valley. Other Wind River through valleys link Popo Agie River tributary valleys with south oriented Sweetwater River tributary valleys. Valley orientations, through valleys, and elbows of capture are interpreted in the context of immense south oriented floods, which flowed across the Wind River Range when the Wind River Range was emerging. Initially regions north of the Wind River Range were at least as high as the Wind River Range and floodwaters could flow across what is today a high mountain range. Floodwaters were flowing from the western margin of a thick North American ice sheet in western Canada to and across Wyoming. The Wind River Range and other mountain ranges emerged as floodwaters deeply eroded surrounding regions and as ice sheet related crustal warping raised the mountain ranges relative to adjacent areas. Initially floodwaters flowed across the Wind River Range to south oriented flood flow channels leading to the actively eroding Green and Colorado River valleys. Headward erosion of the southeast and south-southeast oriented Sweetwater River valley captured south oriented flood flow channels crossing the Wind River Range southeast end. The south oriented flood flow eroded the Wind River Range south flank. Quite independently of what was happening in the Wind River Range area an east oriented valley eroded headward between the emerging Rattlesnake Hills and Ferris Mountains to capture south oriented flood flow west of the North Platte River valley. Headward erosion of this east oriented Sweetwater River valley continued and eventually captured the newly eroded south and southeast oriented Sweetwater River headwaters valley segment about the same time as a major flood flow reversal occurred in the Wind River Basin when headward erosion of the deep northeast oriented Yellowstone River valley in Montana beheaded a south oriented flood flow channel to the present day Bighorn and Wind River Basins. The Yellowstone River valley was eroding headward from space at the south end of the deep “hole” the ice sheet had formed and occupied and which was being opened up by ice sheet melting. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to flow to the much deeper northeast oriented Yellowstone River valley. The northeast oriented Popo Agie River valley then eroded headward from this reversed flood flow channel to capture south oriented flood flow still moving west of the reversed flood flow channel. Headward erosion of the Popo Agie River valley and tributary valleys beheaded south oriented flood flow channels to the south oriented Sweetwater River headwaters and tributary valleys. Subsequently headward erosion of the deep southeast oriented Wind River valley and tributary valleys beheaded all south oriented flood flow routes to the emerging Wind River Range as ice sheet related crustal warping raised the Wind River Range to create the high mountain range seen today.

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 Popo Agie River-Sweetwater River drainage divide area landform origins at the Wind River Range southeast end, Wyoming, 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 Popo Agie River-Sweetwater River drainage divide area landform evidence at the Wind River Range southeast end will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Popo Agie River-Sweetwater River drainage divide area location map

Figure 1: Popo Agie 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 Popo Agie River-Sweetwater River drainage divide area at the Wind River Range southeast end and illustrates a region in west-central Wyoming. Grand Teton National Park is located near the northwest corner of figure 1. The Snake River flows in a south direction through Grand Teton National Park with water eventually reaching the Pacific Ocean. Togwotee Pass is located east of Grand Teton National Park. The Wind River originates near Togwotee Pass and flows in a southeast direction between the Wind River Range and the Owl Creek Mountains to Riverton in the Wind River Basin. At Riverton the Wind River turns to flow in a northeast and north direction across the Owl Creek Mountains eastern end and to enter the Bighorn Basin near Thermopolis. Once in the Bighorn Basin the river name changes to become the Bighorn River. The Bighorn River flows in a north direction through the Bighorn Basin and north of figure 1 enters Montana where it joins the northeast oriented Yellowstone River with water ultimately reaching the Gulf of Mexico. The Popo Agie River is the northeast oriented drainage route shown in figure 1 (but not labeled) originating in the Wind River Range west and south of Lander and flowing to the towns of Lander, Hudson, and Arapahoe in the Wind River Basin before joining the Wind River at Riverton. The North Platte River flows in a north direction from the south edge of figure 1 (east half) to Seminoe, Pathfinder, and Alcova Reservoirs before turning to flow in a northeast direction to Casper at the Laramie Mountains northwest end. At Casper the North Platte River turns to flow in an east direction and east of figure 1 turns again to flow in southeast direction to eventually reach the east oriented Platte River in Nebraska with water eventually reaching the Gulf of Mexico. The Sweetwater River originates in the Wind River Range (south of the Popo Agie River headwaters) and flows in a south and southeast direction to South Pass where the Sweetwater River turns to flow in an east-northeast and east direction to join the North Platte River at Pathfinder Reservoir. West of the Sweetwater River headwaters are headwaters of south-southwest oriented Little Sandy Creek (River in figure 2), which flows to the southwest oriented Big Sandy River. The Big Sandy River flows to the south-southeast oriented Green River, which flows to the south edge of figure 1 (near the town of Green River). South of figure 1 the Green River flow across the Uinta Mountains and eventually joins the southwest oriented Colorado River with water ultimately reaching the Pacific Ocean. The Popo Agie River-Sweetwater River drainage divide area investigated in this essay is north of the southeast oriented Sweetwater River headwaters (upstream from South Pass) and south of the Popo Agie River headwaters in the Wind River Range.

The Popo Agie River and Sweetwater River drainage routes developed during immense melt water floods that flowed across Wyoming. Floodwaters flowed from the western margin of a thick North American ice sheet from western Canada at a time when Wyoming and other regional mountain ranges were emerging. When floodwaters first crossed Wyoming floodwaters were flowing across what are today massive mountain barriers. The mountain ranges, including the Wind River Range, emerged as floodwaters deeply eroded surrounding regions and as ice sheet related crustal warping raised the mountain ranges relative to 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 that time floodwaters were flowing in a south direction across the emerging Owl Creek Mountains and a major south oriented flood flow channel developed between the emerging Wind River Range and the emerging Granite and Green Mountains. Further to the west floodwaters flowed in a south direction across the southeast end of the emerging Wind River Range to the south and southeast oriented Sweetwater River valley, which had eroded headward from the south oriented flood flow channel with water probably flowing to the what was then the actively eroding Colorado River valley south of figure 1. Headward erosion of the southeast oriented Sweetwater River headwaters valley and of the Green River valley and its tributary valleys deeply eroded the Wind River Range southwest flank as south oriented floodwaters flowed across the emerging Wind River mountain range.

A massive flood flow reversal took place when ice sheet melting began to open up space at the south end of the deep “hole” the ice sheet had occupied and which at first was being drained in south direction across eastern Nebraska. Deep northeast oriented valleys including the northeast oriented Yellowstone River valley, eroded headward from that newly opened up deep “hole” space to capture the south oriented flood flow moving across Montana and into Wyoming. The deep northeast oriented Yellowstone River valley beheaded flood flow routes in sequence from east to west and floodwaters on north ends of the beheaded flood flow routes reversed flow direction to flow in north directions to the much deeper Yellowstone River valley. Northeast and east oriented valleys then eroded headward from these newly formed north oriented drainage routes to capture south oriented flood flow still moving west of the actively eroding Yellowstone River valley head. The north oriented Wind-Bighorn River drainage route was created when headward erosion of the deep northeast oriented Yellowstone River valley beheaded a south oriented flood flow channel supplying floodwaters to the flood flow channel eroding a deep canyon (today Wind River Canyon) across the Owl Creek Mountains east end. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction and soon captured all south oriented flood flow flowing to Wind River Canyon flood flow channel and reversed flood flow on the Wind River Canyon alignment. The northeast oriented Popo Agie River valley then eroded headward from this newly reversed flood flow channel to capture south oriented flood flow west of the newly reversed flood flow channel on the present day north oriented Wind-Bighorn River alignment. At that time the Wind River Basin had not been eroded and there was no deep southeast oriented Wind River valley between the emerging Owl Creek Mountains and Wind River Range and floodwaters could still flow across the emerging Wind River Range. Headward erosion of the northeast oriented Popo Agie River valley (and its tributary valleys) beheaded south oriented flood flow channels to the newly eroded south and southeast oriented Sweetwater River valley (and its tributary valleys) and also began to deeply erode the Wind River Range northeast flank. Subsequently headward erosion of the deep southeast Wind River valley (and its tributary valleys) beheaded all flood flow routes to the newly eroded Popo Agie River drainage system and further eroded the Wind River Range northeast flank. Owl Creek Mountains emergence ended all south oriented flood flow to the newly eroded southeast oriented Wind River drainage system, although southeast oriented flood flow across Togwotee Pass continued until beheaded by headward erosion of the deep Snake River valley.

Detailed location map for Popo Agie River-Sweetwater River drainage divide area

Figure 2: Detailed location map Popo Agie 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 Popo Agie River-Sweetwater River drainage divide area at the Wind River Range southeast end. The green colored area is National Forest land in the Wind River Range. The east-west continental extends from the northwest corner of figure 2 along the Wind River Range crest to Wind River Peak and then in a south direction to the Prospect Mountains where it turns in a southeast to cross the south edge of figure 2 near South Pass. The Little Sandy River (Creek is figures 1 and 3) originates near Wind River Peak and flows in south direction west of the continental divide to the south edge of figure 2. South of figure 2 the Little Sandy River flows to the Big Sandy River, which flows to the Green River with water eventually reaching the Pacific Ocean. The Sweetwater River originates between the continental divide and Atlantic Peak and flows in a south and south-southeast direction to South Pass where it turns to flow in an east-northeast direction to the east edge of figure 2 (south half). East of figure 2 the Sweetwater River turns to flow in an east direction to join the North Platte River with water flowing to Nebraska and eventually reaching the Gulf of Mexico. Labeled south oriented Sweetwater River tributaries of interest in this essay include the East Sweetwater River, Gold Creek, Willow Creek, and Rock Creek. The south and southeast oriented Sweetwater River headwaters and tributary valleys were eroded by south oriented flood flow that moved across what was at that time the emerging Wind River Range. At that time the deep Wind River Basin to the north did not exist and the Wind River Range did not stand high above regions to the north as it does today. Deep south oriented valleys eroded headward to the emerging Wind River Range mass and deeply eroded the regions to the south and east. The Middle Fork Popo Agie River originates in the Wind River Range near Wind River Peak and flows in an east and northeast direction to the north center edge of figure 2. The Little Popo Agie River originates east of Atlantic Peak and flows in an east, northeast, and north-northwest direction to the north edge of figure 2 (east of the Popo Agie River) and joins the Popo Agie River north of figure 2. Beaver Creek originates west of the town of Miners Delight and flows in an east-southeast and east direction (near Miners Delight) before turning to flow in a north-northeast direction to the northeast corner of figure 2. North of figure 2 Beaver Creek turns to flow in a north-northwest direction to join the northeast oriented Popo Agie River, which then flows to the northeast and north oriented Wind River with water eventually reaching the northeast oriented Yellowstone River in Montana and ultimately the Gulf of Mexico. Headward erosion of the Little Popo Agie River valley beheaded south oriented flood flow routes to the East Sweetwater River valley and other Sweetwater River tributary valleys and to the Beaver Creek valley. Headward erosion of the Middle Popo Agie River valley beheaded south oriented flood flow routes to the newly eroded Little Popo Agie River valley and to south oriented Sweetwater River headwaters valleys (and also to the Little Sandy River headwaters valley). North oriented Middle Popo Agie River tributaries drainage routes were created by reversals of flood flow on north ends of beheaded flood flow routes. Subsequently headward erosion of the North Popo Agie River valley (seen in the northwest corner area of figure 2) beheaded south oriented flood flow routes to the newly eroded Middle Popo Agie River valley.

Middle Popo Agie River-Sweetwater River drainage divide area

Figure 3: Middle Popo Agie River-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 Middle Popo Agie River-Sweetwater River drainage divide area. The map contour interval for figure 3 is 50 meters. The east-west continental divide is shown with a dashed line and extends from the southwest corner of figure 3 to the north edge of figure 3 (west half). Little Sandy Creek flows in south and southwest direction just west of the continental divide with water eventually reaching the Big Sandy, Green, and Colorado Rivers and ultimately the Pacific Ocean. Roaring Fork Mountain is a labeled mountain in the north center area of figure 3. The Sweetwater River originates between Roaring Fork Mountain and the continental divide and flows in a south direction to the south edge of figure 3. South and east of figure 3 the Sweetwater River turns to flow in a south-southeast, southeast, east-northeast, and east direction to join the North Platte River with water eventually reaching the Platte, Missouri, and Mississippi River and ultimately the Gulf of Mexico. The Middle Popo Agie River originates just north of the Sweetwater River headwaters and flows in a north and northeast direction to the north center edge of figure 3. North and east of figure 3 the Middle Popo Agie River flows to the Popo Agie, Wind, Bighorn, Yellowstone, Missouri, and Mississippi Rivers. A north to south oriented through valley links the north oriented Middle Popo Agie River headwaters valley with the south oriented Sweetwater River headwaters valley. The through valley floor elevation is between 3150 and 3200 meters. Elevations on Roaring Fork Mountain to the east rise to more than 3700 meters. Elevations on the unnamed mountain to the west also rise to more than 3700 meters. These elevations suggest the through valley is at least 500 meters deep. This 500-meter deep through valley was eroded by south oriented flood flow moving to the actively eroding south oriented Sweetwater River valley. At that time there was no Middle Popo Agie River valley nor was a deep Wind River Basin further to the north. Headward erosion of the deeper northeast oriented Middle Popo Agie River valley beheaded the south oriented flood flow route and floodwaters on the north end of the beheaded flood flow route reversed flow direction to create the north oriented Middle Popo Agie River headwaters drainage route. After the Wind River Range had emerged alpine glaciers formed and made minor modifications in the drainage routes and valley shapes. Another intriguing and much shallower through valley is south of Little Sandy Lake and links the south oriented Little Sandy Creek valley with southeast and south oriented Larsen Creek, which is a Sweetwater River tributary. This shallower through valley crosses the continental divide and provides evidence of diverging and converging flood flow channels in an anastomosing channel complex that crossed the present day east-west continental divide.

Detailed map of Middle Popo Agie River-Sweetwater River drainage divide area

Figure 4: Detailed map of Middle Popo Agie River-Sweetwater 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 Middle Popo Agie River-Sweetwater River drainage divide area seen in less detail in figure 3. The map contour interval for figure 4 is 40 feet. The east-west continental divide crosses the southwest corner of figure 4 with areas in the southwest corner draining to the Pacific Ocean. Sweetwater Gap is located near the center of figure 4 and has an elevation of 10,327 feet. The Sweetwater River originates on the south side of Sweetwater Gap and flows in a south direction to the south center edge of figure 4. South of figure 4 the Sweetwater River turns to flow in a south-southeast direction and subsequently turns to flow in an east-northeast and east direction to join the North Platte River, which flows into Nebraska. The Middle Popo Agie River originates at the small lake west of Sweetwater Gap and then flows in a northeast and north direction to the north center edge of figure 4. North of figure 4 the Middle Popo Agie River turns to flow in an east and northeast direction with water eventually flowing to the Yellowstone River in Montana. Tayo Creek is the northeast oriented Middle Popo Agie River tributary flowing across the northwest corner of figure 4. The unnamed mountain west of Sweetwater Gap reaches 12,366 feet just south of the south edge of figure 4. Roaring Fork Mountain achieves an elevation of 12,239 feet also just south of the south edge of figure 4. These elevations suggest Sweetwater Gap is more than 1900 feet deep (using elevations seen in figure 4 Sweetwater Gap is only 1600 feet deep). Regardless of its depth Sweetwater Gap is a major through valley linking a present day north oriented drainage route with a present day south oriented drainage route and was eroded by south oriented flood flow crossing the present day high Wind River Range. At the time floodwaters flowed through Sweetwater Gap the deep Middle Popo Agie River valley north of figure 4 did not exist and the Wind River Range did not stand high above regions to the north. Headward erosion of the east and northeast oriented Middle Popo Agie River valley north of figure 4 beheaded the south oriented flood flow route through Sweetwater Gap. Floodwaters on the north end of the beheaded flood flow route reversed flow direction to create the north oriented Middle Popo Agie River drainage route. The region seen in figure 4 was subsequently modified by alpine glaciation, although the glaciation did not occur until after the Wind River Range had emerged as a high mountain range. Further, the alpine glaciation only modified existing valleys that had been eroded during the much earlier flood events.

Little Popo Agie River-East Sweetwater River drainage divide area

Figure 5: Little Popo Agie River-East Sweetwater River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Middle Popo Agie River-East Sweetwater River drainage divide area south and east of figure 3 and there is an overlap area with figure 3. The map contour interval for figure 5 is 50 meters. The Little Popo Agie River originates at Christina Lake (in west half of figure 5) and flows in an east-northeast direction to the north edge of figure 5 (near northeast corner). North and east of figure 5 the Little Popo Agie River flows into the Wind River Basin and joins the northeast oriented Popo Agie River with water eventually reaching the northeast oriented Yellowstone River. Louis Creek originates near the center of figure 5 and flows in an east and northeast direction through Louis Lake to join the Little Popo Agie River in the Maxon Basin (in northeast quadrant of figure 5). Pass Creek is located east of Louis Creek and flows in a northeast and northwest direction to join the Little Popo Agie River near the northeast corner of figure 5. The Little Sweetwater River originates south and west of Christina Pass (south and west of Christina Lake) and flows in a southwest, south, and southwest direction to the southwest corner of figure 5 and south and west of figure 5 joins the south-southeast oriented Sweetwater River. The East Sweetwater River originates south of Sioux Pass and flows in a southwest and south-southwest direction to the south edge of figure 5 (west half) and south of figure 5 flows in a south and west direction to join the south-southeast oriented Sweetwater River. Pine Creek is a south oriented stream originating south of the East Sweetwater River headwaters and flowing to the south center edge of figure 5. South of figure 5 Pine Creek turns to flow in a southeast direction and eventually joins the east-northeast oriented Sweetwater River. Sioux Pass is a through valley linking the northeast oriented Louis Creek valley with the southwest oriented East Sweetwater Creek valley. The Sioux Pass elevation is between 2950 and 3000 meters. Granite Peak to the east rises to 3171 meters and elevations to the west rise to more than 3250 meters suggesting the Sioux Pass is at least 171 meters deep. Sioux Pass was eroded by south oriented flood flow moving from the present day northeast oriented Little Popo Agie River drainage basin to the East Sweetwater River headwaters valley, which probably beheaded a south oriented flood flow channel to the south and southeast oriented Pine Creek valley. Headward erosion of the northeast oriented Louis Creek valley followed by headward erosion of the east-northeast oriented Little Popo Agie River valley beheaded the south oriented flood flow route across Sioux Pass. Christina Pass links the Christina Lake basin with the southwest and south oriented Little Sweetwater River headwaters. The 50-meter contour interval does not do justice to the Christina Pass depth, which on more detailed maps with a 40-foot contour interval s shown as being almost 200 feet. Christina Pass was eroded by south oriented flood flow moving to the Little Sweetwater River valley prior to headward erosion of the deeper east-northeast oriented Little Popo Agie River.

Detailed map of Louis Creek-East Sweetwater River drainage divide area

Figure 6: Detailed map of Louis Creek-East 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 Louis Creek-East Sweetwater River drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 40 feet. The well-marked National Forest boundary line extends from the west edge of figure 6 (near northwest corner) to the south edge of figure 6 (east half). Pabst Peak and Granite Peak are two labeled mountain peaks on the National Forest boundary line in the southeast quadrant of figure 6. Sioux Pass is located on the National Forest boundary in section 22 (north and west of Granite Peak). Louis Creek originates as an east oriented stream in section 16 and in section 15 (north of Sioux Pass) turns to flow in a northeast direction to the north edge of figure 6. North and east of figure 6 Louis Creek joins the east-northeast oriented Little Popo Agie River with water eventually reaching the Yellowstone River in Montana. The East Sweetwater River originates in section 21 (south and west of Sioux Pass) and flows in a southwest, west, and southwest direction to the southwest corner of figure 6. South and west of figure 6 the East Sweetwater River turns to flow in south and west direction to join the south-southeast oriented Sweetwater River with water eventually reaching the Platte River in Nebraska. The Sioux Pass floor elevation is between 9720 and 9760 feet. Granite Peak reaches an elevation of 10,404 feet and elevations along the drainage divide in section 17 to the northwest rise to more than 10,600 feet. These elevations suggest Sioux Pass is at least 640 feet deep. Sioux Pass is another water-eroded valley, although the flood flow channel history probably is more complex than the Sweetwater Gap history. Figures 7 and 8 will illustrate the East Sweetwater River-Pine Creek drainage divide area south of figure 6. Probably Sioux Pass was initially eroded by floodwaters flowing to the south and southeast oriented Pine Creek valley and that were subsequently captured by headward erosion of the deeper southwest oriented East Sweetwater River valley. At that time the region north of the Wind River Range was as high as the Wind River Range and floodwaters could freely flow across what is today a high mountain region. Still later headward erosion of the deeper east and northeast oriented Louis Creek valley captured the south oriented flood flow and diverted the floodwaters in a northeast direction to space at the south end of the deep “hole” the melting ice sheet was opening up. This reversal of flood flow helped erode the Wind River Basin and the Wind River Range northeast flank, although ice sheet crustal warping probably has raised the Wind River Range since that time as well.

East Sweetwater River-Pine Creek drainage divide area

Figure 7: East Sweetwater River-Pine Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the East Sweetwater River-Pine Creek drainage divide area south and slightly west of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 7 is 50 meters. The Sweetwater River flows in a south-southeast direction from the northwest corner of figure 7 to the south edge of figure 7 (west half). South of figure 7 the Sweetwater River turns to flow in an east-northeast and east direction to eventually join the North Platte River with water flowing to the Platte River in Nebraska. Sioux Pass is located slightly east of the north center edge area of figure 7. The East Sweetwater River originates south of Sioux Pass and flows in a southwest, south, and west direction to join the south-southeast oriented Sweetwater River near the south edge of figure 7. Pine Creek originates south of the East Sweetwater River headwaters and west of Rennecker Peak and flows in a south and south-southeast direction to the south edge of figure 7 (east half) and south of figure 7 joins the east-northeast oriented Sweetwater River. A north to south oriented through valley links the East Sweetwater River headwaters area with the south and south-southeast oriented Pine Creek valley. The through valley floor elevation is between 2750 and 2800 meters. Rennecker Peak to the east rises to 3064 meters. The unnamed ridge to the west rises to at least 2900 meters suggesting the through valley is at least 100 meters deep. The through valley was eroded by south oriented flood flow moving to what was at that time the actively eroding Pine Creek valley. At that time the deeper southwest oriented East Sweetwater River valley did not exist nor did the Louis Creek or Little Popo Agie River valleys north of figure 7 exist. Further, at that time the Wind River Range did not stand high above the regions to the north as it does today. Floodwaters were flowing across what is today a high mountain range and eroding what is today that mountain range’s southern flank as the mountain range emerged. Figure 8 provides a detailed topographic map to better illustrate the East Sweetwater River-Pine Creek drainage divide area.

Detailed map of East Sweetwater River-Pine Creek drainage divide area

Figure 8: Detailed map of East Sweetwater River-Pine 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 East Sweetwater River-Pine Creek drainage divide area seen in less detail in figure 7 above. The map contour interval for figure 8 is 40 feet. Granite Peak is located near the northeast corner of figure 8. East Sweetwater River flows from the north edge of figure 8 (east of center) in a southwest, west, and southwest direction to the west edge of figure 8 (south of center) and west and south of figure 8 joins the south-southeast oriented Sweetwater River. Rennecker Peak is located in section 34 south of Granite Peak. Pine Creek originates on the west side of Rennecker Peak and flows in a west, south-southwest and south-southeast direction to the south edge of figure 8 (east half) and south and east of figure 8 joins the east-northeast oriented Sweetwater River.  A north to south oriented through valley in the west half of section 33 links a northwest oriented East Sweetwater River tributary valley with a south-southeast oriented Pine Creek tributary valley. The through valley floor elevation is between 9160 and 9200 feet. The Rennecker Peak elevation is 10,053 feet. The high point in section 32 to the west of the through valley is 9656 feet suggesting the through valley is at least 456 feet deep. The through valley is a water-eroded valley and was eroded by south-southeast oriented flood flow prior to headward erosion of the deeper southwest oriented East Sweetwater River valley. Headward erosion of the southwest oriented East Sweetwater River valley is difficult to explain unless south oriented flood flow was moving along at least two diverging flood flow channels such as found in anastomosing channel complexes. One of the diverging flood flow channels led to the actively eroding Pine Creek valley while the other diverging flood flow channel led to the actively eroding East Sweetwater River valley. The deeper East Sweetwater Creek valley is evidence the south-southeast oriented Sweetwater River valley west of figure 8 at that time did not flow to the east-northeast oriented Sweetwater River valley south and east of figure 8. Instead the south-southeast oriented Sweetwater River valley at that time was probably eroding headward from a south oriented flood flow channel moving floodwaters to the Colorado River basin. Headward erosion of the east-northeast oriented Sweetwater River valley subsequently captured the south-southeast and southeast oriented Pine Creek flood flow channel and then the south-southeast oriented Sweetwater River flood flow and diverted the floodwaters to the North Platte River drainage basin.

Pine Creek-Sweetwater River drainage divide area

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

Figure 9 illustrates the Pine Creek-Sweetwater River drainage divide area south and slightly east of figure 7 and there is an overlap area with figure 7. The map contour interval for figure 9 is 20 meters. The Sweetwater River flows in a south-southeast and southeast direction from the northwest corner of figure 9 to the south center area of figure 9 and then turns to flow in an east and east-northeast direction to the east edge of figure 9 (south half). East of figure 9 the Sweetwater River flows in an east-northeast and east direction to the North Platte River with water eventually reaching the Gulf of Mexico. The East Sweetwater River flows in a south and west direction from the north edge of figure 5 (west half) to join the south-southeast oriented Sweetwater River in the northwest quadrant of figure 9. Pine Creek flows in a south-southeast and southeast direction from the north center edge of figure 9 to join the east-northeast oriented Sweetwater River in the southeast quadrant of figure 9. The east-west continental divide is labeled and is located almost adjacent to the southeast oriented Sweetwater River valley in the west half of figure 9. South and west of the continental divide drainage is to the Pacific Ocean. Monument Draw drains to Hay Creek, which drains to Dry Sandy Creek with water eventually reaching the Green and Colorado Rivers. Elkhorn Draw drains to West Pacific Creek with water flowing to Pacific Creek, with water also eventually reaching the Green and Colorado Rivers. A shallow through valley links the south oriented East Sweetwater River valley with a south and southwest oriented Sweetwater River tributary valley. The through valley is defined by only one contour line on the west side so is relatively shallow. However the through valley provides evidence floodwaters once flowed directly south to the Sweetwater Creek valley.  A somewhat deeper through valley along the west edge of figure 9 links the south-southeast oriented Sweetwater River valley with the south oriented Monument Draw and Hay Creek valleys. The floor of this through valley across the continental divide has an elevation of between 2340 and 2360 meters. Elevations along the continental divide to the southeast rise to more than 2420 meters. While not seen in figure 9 elevations along the continental divide to the west rise even higher. This north to south oriented through valley across the continental divide was eroded by south oriented flood flow moving from the south-southeast oriented Sweetwater River alignment. Further to the southeast at South Pass (where the highway crosses the continental divide) an even better defined through valley crosses the continental divide, although Oregon Buttes on the through valley south side are not seen in figure 9. Elevations along the continental divide in the South Pass area are approximately 2300 meters. Elevations in the Oregon Buttes rise to 2624 meters. Continental divide elevations rise to 2630 meters a short distance west of figure 9. In other words the entire continental divide stretch seen in figure 9 is lower in elevation than elevations to the west of figure 9 and to the south of figure 9 and was eroded as the floor of a broad 300-meter deep through valley linking the south-southeast and south oriented Sweetwater River headwaters and tributary valleys with south oriented Green River tributary valleys. Headward erosion of the southeast oriented Sweetwater River valley first captured many of the south and south-southeast oriented flood flow channels, although it may have originally headward from a south oriented flood flow channel in the South Pass area. Subsequently headward erosion of the east-northeast and east oriented Sweetwater River valley captured the newly eroded southeast oriented Sweetwater River flood flow channel and diverted the floodwaters to the North Platte River, although by that time flood flow across the emerging Wind River Range was probably ending.

Detailed map East Sweetwater River-Sweetwater River drainage divide area

Figure 10: Detailed map of East Sweetwater River-Sweetwater River 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 Sweetwater River-Sweetwater River drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 20 feet. The Sweetwater River flows in a south-southeast and southeast direction from the north edge of figure 10 (slightly west of center) to the south edge of figure 10 (near southeast corner). South and east of figure 10 the Sweetwater River turns to flow in an east-northeast and east direction to join the North Platte River with water eventually reaching the Gulf of Mexico. Lander Creek is the southeast oriented Sweetwater River tributary flowing from the northwest corner of figure 10. The East Sweetwater River flows in a south and west direction from the north edge of figure 19 (east half) to join the south-southeast oriented Sweetwater River near the line between sections 34 and 35. Palmer Draw is a south and southwest oriented Sweetwater River tributary located in section 3. A north to south oriented through valley in the southwest quadrant of section 36 links a north oriented East Sweetwater River tributary valley with the south oriented Palmer Draw headwaters valley. The through valley floor elevation is between 7900 and 7920 feet. Elevations west of the through valley rise to more than 7980 feet and elevations east of the through valley are greater than 8000 feet. These elevations suggest the through valley is at least 60 feet deep. A similar through valley in the southwest quadrant of section 2 links the Palmer Draw valley with a south and southwest oriented Sweetwater River tributary valley. The floor of this second through valley has an elevation of between 7840 and 7860 feet. Elevations in the northeast quadrant of section 10 to the southwest rise to more than 7980 feet suggesting this second through valley is at least 120 feet deep. These through valleys were eroded by south oriented flood flow from the south oriented East Sweetwater Creek alignment flowing to what was at that time the actively eroding Sweetwater River valley. Headward erosion of the deep southwest oriented Palmer Draw valley beheaded flood flow moving across the second through valley. Headward erosion of the west oriented East Sweetwater Creek valley next beheaded south oriented flood flow to the newly eroded Palmer Draw valley. The higher elevation of the East Sweetwater River-Palmer Draw through valley floor may be the result of crustal warping that has raised the Wind River Range to the north since the flood flow ended. The east-west continental divide extends in an east direction from the west center edge of figure 10 almost to the southeast oriented Sweetwater River valley and then extends in a southeast direction along the Sweetwater River valley southwest wall to the south edge of figure 10. The high point on the continental divide seen in figure 10 is located along the Sweetwater River valley southwest wall in section 10 and has an elevation of 7990 feet. Continental divide elevations west of figure 10 rise much higher. Further to the west Lander Creek and the continental divide cross a through valley in section 33 and 5 linking the south-southeast oriented Sweetwater River valley (the through valley diverges from the Sweetwater River valley north of figure 10) with the south oriented Hay Creek headwaters valley in the southwest corner of figure 10. The floor of this through valley has an elevation of between 7680 and 7700 feet suggesting the through valley is almost 200 feet deep. The through valley was eroded by south oriented flood flow moving to the Green River drainage basin prior to headward erosion of the southeast oriented Sweetwater River valley and its southeast oriented Lander Creek tributary valley.

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.