Wind River-Powder River drainage divide area landform origins south of the Bighorn Mountains, Wyoming, USA

Authors

 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the region between the Wind River and the Powder River south of the Bighorn Mountains. A broad low relief west-to-east oriented through valley between the Bighorn Mountains to the north and the Rattlesnake Hills to the south links the north-northeast oriented South Fork Powder River valley with northwest and west oriented tributary valleys draining to the north oriented Wind River, which flows through Wind River Canyon to the Bighorn Basin where the Wind River becomes the north oriented Bighorn River. The South Fork Powder River flows to the north oriented Powder River in the Powder River Basin, which is east of the Bighorn Mountains. The Bighorn Basin is located west of the Bighorn Mountains. The north oriented Powder and Bighorn River both flow into Montana where they join the northeast oriented Yellowstone River. Topographic map evidence illustrated and discussed in this essay is interpreted in the context of immense south and southeast oriented melt water floods that once crossed central Wyoming to reach what at that time was the actively eroding southeast oriented North Platte River valley. At that time the Bighorn Mountains, Rattlesnake Hills, and other regional mountain ranges had not emerged and floodwaters could freely flow across what are today major mountain barriers. Floodwaters were derived from the western margin of a thick North American ice sheet and were flowing from western Canada to and across Wyoming. Wyoming mountain ranges emerged as floodwaters deeply eroded surrounding valleys and basins and as ice sheet related crustal warping raised mountain ranges relative to adjacent valleys and basins. Ice sheet related crustal warping and deep glacial erosion also created a deep “hole” in which the ice sheet was located. The Platte and North Platte River valley eroded headward from the actively eroding Missouri River valley to capture the south and southeast oriented flood flow moving across Nebraska and Wyoming. Over time ice sheet melting opened up space at the south end of the deep “hole”, which drained in south directions to the actively eroding Missouri River and tributary valleys. The deep northeast oriented Yellowstone River valley then eroded headward across Montana to capture the south and southeast oriented melt water floods and beheaded flood flow routes to the actively eroding North Platte River valley. Floodwaters on north ends of the beheaded flood flow routes reversed flow direction to create much deeper north oriented valleys, which then captured south and southeast oriented flood flow from west of the actively eroding Yellowstone River valley head. Flood flow routes to Wyoming were beheaded in sequence from east to west, which meant flood flow routes in the Powder River Basin were beheaded and reversed while flood flow was still moving in south and southeast directions across the Bighorn Basin to the west of the emerging Bighorn Mountains. Headward erosion of the much deeper north oriented Powder River valley and its north-northeast oriented tributary South Powder River valley then captured the south and southeast oriented flood flow routes moving floodwaters across central Wyoming to the actively eroding North Platte River valley. Headward erosion of the deep northeast oriented Yellowstone River valley subsequently beheaded and reversed flood flow routes in the Bighorn Basin and created the north oriented Bighorn River drainage route, which captured southeast oriented flood flow entering the Wind River Basin and which ended flood flow to the newly eroded north-northeast oriented South Fork Powder River valley. Floodwaters on west ends of beheaded flood flow routes to the newly eroded South Fork Powder River valley reversed flow direction to create west oriented Wind River tributary drainage routes.

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-Powder River drainage divide area landform origins south of the Bighorn Mountains, 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 Wind River-Powder River drainage divide area landform evidence south of the Bighorn Mountains will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Wind River-Powder River drainage divide area location map

Figure 1: Wind River-Powder 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-Powder River drainage divide area south of Bighorn Mountains and illustrates a region in central Wyoming. Casper is the largest city shown and is located near the southeast corner of figure 1. The North Platte River flows in a northeast and east direction across the southeast corner of figure 1 and is the river flowing through Casper. East of figure 1 the North Platte River flows in a southeast direction to eventually join the South Platte River and to form the Platte River, which flows across Nebraska to the Missouri River. North Platte River tributaries shown include Casper Creek and Poison Spider Creek, which originate in the Rattlesnake Hills, and the Sweetwater River, which flows in an east direction south of the Granite Mountains. North of Casper Creek are headwaters of the north oriented Powder River drainage system. The South Fork Powder River originates at the northwest end of the Rattlesnake Hills and flows in a northeast and north-northeast direction to join the northeast oriented Middle Fork Powder River and southeast oriented North Fork Powder River east of Kaycee and to form the Powder River. Once formed the Powder River flows in an east and north direction to the northeast corner of figure 1 and north of figure 1 flows into Montana where it joins the northeast oriented Yellowstone River, which joins the Missouri River near the Montana-North Dakota border. The mountain range where the North and Middle Forks Powder River originate is the Bighorn Mountains. The Powder River Basin is east of the Bighorn Mountains and the Bighorn Basin is located west of Bighorn Mountains. The Bighorn Basin is drained by the north oriented Bighorn River, which in Montana (north of figure 1) joins the northeast oriented Yellowstone River. The Bighorn River originates as the southeast oriented Wind River west of the Owl Creek Mountains. The Wind River flows in a southeast direction from the west center edge of figure 1 between the Owl Creek Mountains and the Wind River Range into the Wind River Basin (south of the Owl Creek Mountains) and at Riverton turns to flow in a northeast and north direction to flow through Wind River Canyon (between Boysen Reservoir and Thermopolis) into the Bighorn Basin. Once in the Bighorn Basin the Wind River becomes the Bighorn River. Poison Creek in a north-northeast and west-northwest oriented Wind River tributary originating at the northwest end of the Rattlesnake Hills and joining the Wind River at Boysen Reservoir. North of Poison Creek the unnamed stream flowing from Arminto to Lyesite is Alkali Creek, which joins west oriented Badwater Creek at Lyesite. Badwater Creek originates at the south end of the Bighorn Mountains and flows in a southwest direction to Lyesite and then in a west direction to join the Wind River at Boysen Reservoir. The Wind River-Powder River drainage divide area investigated in this essay extends from the south end of the Bighorn Mountains to the northwest end of the Rattlesnake Hills and looks specifically at the drainage divide between west oriented Wind River tributaries (Badwater Creek, Alkali Creek, and Poison Creek) and the northeast and north-northeast oriented South Fork Powder River.

Wyoming drainage systems evolved during immense melt water floods from the western margin of a thick North American ice sheet. Floodwaters initially flowed in south and southeast directions from western Canada to and across Wyoming. When the massive south and southeast oriented flood flow began mountain ranges seen in figure 1 had not emerged and floodwaters could freely flow across the entire region. The mountain ranges emerged as floodwaters deeply eroded surrounding basins and as ice sheet related crustal warping raised the mountain ranges as a deep “hole” was created in which the ice sheet was located. Headward erosion of the southeast oriented North Platte River valley (from the deep Missouri River and Platte River valleys, which had eroded headward from the deep Mississippi River valley) and its tributary valleys (Poison Spider Creek, Casper Creek, and Sweetwater River valleys) captured the south and southeast oriented floodwaters flowing across the region seen in figure 1 and diverted floodwaters in an east and southeast direction to the Missouri River valley. At that time southeast oriented floodwaters flowing into the Wind River Basin and south oriented floodwaters crossing the Bighorn Basin flowed in an east direction in the region south of the emerging Bighorn Mountains to the newly eroded and much deeper North Platte River valley.

Eventually ice sheet melting opened up space at the south end of the deep “hole” the melting ice sheet had occupied and that space was initially drained in a south direction along south oriented flood flow channels which eroded the Missouri River and Mississippi River valleys east of figure 1. Elevations on the deep “hole” floor were much lower than elevations along the deep “hole” southwest rim in Montana and the deep northeast oriented Yellowstone River valley was able to erode headward across Montana to capture the south and southeast oriented melt water floods flowing across the deep “hole” southwest rim to Wyoming. Headward erosion of the deep northeast oriented Yellowstone River valley beheaded flood flow routes to Wyoming in sequence from east to west. Flood flow routes crossing the Powder River Basin were beheaded before flood flow routes crossing the Bighorn Basin were beheaded. Floodwaters on north ends of beheaded flood flow routes reversed flow direction and created much deeper north and northeast oriented valleys, which then captured south, southeast, and east oriented floodwaters moving west of the actively eroding Yellowstone River valley head. Headward erosion of the newly formed and deep north oriented Powder River valley captured southeast oriented flood flow still crossing the emerging Bighorn Mountains (see southeast oriented North Fork Powder River) and then headward erosion of the north-northeast oriented South Fork Powder River valley captured east oriented flood flow moving south of the emerging Bighorn Mountains to the newly eroded North Platte River valley.

Yellowstone River valley headward erosion subsequently beheaded south oriented flood flow routes to the Bighorn Basin and floodwaters on north ends of the beheaded flood flow routes reversed flow direction to create the much deeper and north oriented Bighorn River drainage route. Reversed flow on the Bighorn River drainage route captured southeast oriented flood flow still entering the Wind River Basin from the west and headward erosion of the deeper north oriented Bighorn (Wind) River valley then deeply eroded the Wind River Basin and beheaded east oriented flood flow routes to the newly eroded north-northeast oriented South Fork Powder River valley. Floodwaters on west ends of the beheaded flood flow routes reversed flow direction to create west oriented Wind River drainage routes. These flood flow reversals and captures were taking place as the mountain ranges were emerging and were greatly influenced by the mountain range emergence.

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

Figure 2: Detailed location map Wind River-Powder 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-Powder River drainage divide area south of the Bighorn Mountains. The south end of the Bighorn Mountains is located near the north center edge of figure 2. Badwater is a town at the south end of the Bighorn Mountains. Badwater Creek flows in a southwest direction to Badwater and then turns to flow in a northwest and southwest direction to Lyesite and then in a west direction to the west edge of figure 2 (north half). Alkali Creek is the west-northwest oriented stream originating near Arminto and joining Badwater Creek near Lyesite. The northwest end of the Rattlesnake Hills is located near the south center edge of figure 2. The Ervay Basin is located just north of the Rattlesnake Hills near the south center edge of figure 2. Poison Creek originates just north of the Ervay Basin and flows in a north-northeast and northwest direction to Hiland where it turns to flow in a west and west-northwest direction to the west edge of figure 2 (north of center). West of figure 2 Badwater Creek and Poison Creek both flow to the north oriented Wind River (which becomes the Bighorn River once it enters the Bighorn Basin). The South Fork Powder River originates in the Ervay Basin and flows in a northeast direction to the town of Powder River and then in a northeast direction to the east edge of figure 2 (north half). East and north of figure 2 the South Fork Powder River flows to the north oriented Powder River. Wallace Creek is a northeast oriented tributary originating near the town of Ervay and joining the South Fork Powder River a short distance west of the town of Powder River. East and south of Wallace Creek are northeast oriented headwaters of Casper Creek, which flows in a northeast and east direction to the town of Natrona and then to the east edge of figure 2. East of figure 2 Casper Creek flows to the east and southeast oriented North Platte River. The northwest end of the Rattlesnake Hills and Ervay Basin area is drained today by three different river systems in three different directions, yet those three different river systems are all components of the Missouri River drainage basin. As described in the figure 1 discussion headward erosion of the deep North Platte River valley first captured southeast and east oriented flood flow crossing the region. Next a massive flood flow reversal in the Powder River Basin to the north and east of figure 2 enabled the northeast oriented South Fork Powder River valley to erode headward into the region and to capture the southeast and east oriented flood flow routes to the newly eroded North Platte River and tributary valleys. Finally a massive flood flow reversal in the Bighorn Basin (north and west of figure 2) captured the southeast oriented flood flow entering the Wind River Basin (west of figure 2) and ended east oriented flood flow to the newly eroded northeast oriented South Fork Powder River valley. Floodwaters on west ends of the beheaded flood flow routes reversed flow direction to create the west oriented Wind River tributary drainage routes.

Baker Creek-E K Creek drainage divide area

Figure 3: Baker Creek-E K Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of Baker Creek-E K Creek drainage divide area. The map contour interval for figure 3 is 20 meters. The region is located along the Bighorn Mountains south margin and southeast dipping hogback ridges are located along the south and southeast sides of several stream valleys. The west and south-southwest oriented stream in the northwest corner of figure 3 is the headwaters of Badwater Creek. South of the west oriented Badwater Creek headwaters are headwaters of southeast and south oriented Willow Creek, which flows to west-southwest oriented Dry Fork (Badwater Creek). West of figure 3 after making a northwest and southwest jog Badwater Creek flows in a west direction to join the north oriented Wind River (which in the Bighorn Basin becomes the Bighorn River). Deadman Butte is located south of the center of figure 3. The south oriented stream flowing near Deadman Butte to the south edge of figure 3 (east of Jackpot Reservoir) is E K Creek, which south of figure 3 (near Arminto) turns to flow in a west-northwest direction as Alkali Creek, which then joins west oriented Badwater Creek near Lyesite. The northeast oriented stream flowing to the northeast corner of figure 3 is Baker Creek. North and east of figure 3 Baker Creek joins northeast and north oriented Buffalo Creek, which flows to the northeast oriented Middle Fork Powder River. Sanchez Creek is a southeast oriented stream located east of Willow Creek and at first glance appears to be flowing to northeast oriented Baker Creek, but a close look reveals Sanchez Creek joins southeast, east-northeast, and southeast oriented North Fork Cottonwood Creek, which in the east center edge area of figure 3 joins east-southeast oriented Cottonwood Creek, which then turns to flow in a south-southeast direction to the east edge of figure 3 (south of center). The South Fork Cottonwood Creek flows to the east edge of figure 3 (south of Cottonwood Creek). South and east of figure 3 Cottonwood Creek joins the north-northeast oriented South Fork Powder River. What has happened here is southeast and east oriented flood flow was moving across the region and was captured by headward erosion of the northeast oriented Baker Creek valley and then by headward erosion of the southeast oriented Cottonwood Creek valley and its tributary North Fork Cottonwood Creek and Sanchez Creek valley. The flood flow across the region was subsequently beheaded by headward erosion of the much deeper and north oriented Wind River (and Bighorn River) valley west of figure 3. Floodwaters on west ends of the beheaded flood flow routes reversed flow direction to create the west oriented Badwater Creek drainage system. Evidence supporting this interpretation can be found in the through valleys linking the Dry Fork Badwater Creek and E K Creek headwaters valleys with southeast, east-northeast, and southeast oriented North Fork Cottonwood Creek valley, and also with the northeast oriented Baker Creek valley. Study of the figure 3 drainage divides reveals many other similar through valleys. The through valleys were eroded by floodwaters moving from the present day Wind River and Bighorn River drainage basins to the present day Powder River drainage basin.

Alkali Creek-Branch Cave Gulch drainage divide area

Figure 4: Alkali Creek-Branch Cave Gulch drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 provides a topographic map of the Alkali Creek-Branch Cave Gulch drainage divide area south and slightly west of figure 3 and includes a small overlap area with figure 3. The map contour interval for figure 4 is 20 meters. Arminto is the town located near the center of figure 4. E K Creek flows in a south direction from the north edge of figure 4 (just east of Jackpot Reservoir) to near Arminto and then turns to become Alkali Creek and to flow in a west-northwest direction to the west edge of figure 4 (near the railroad). West of figure 4 Alkali Creek joins west oriented Badwater Creek to flow to the north oriented Wind River (and Bighorn River). East of Arminto is south-southeast and southeast oriented North Branch Cave Gulch, which joins east and northeast oriented South Branch Cave Gulch near the east edge of figure 4 (south of center) to form east oriented Branch Cave Gulch, which east of figure 4 joins the north-northeast oriented South Fork Powder River. The railroad just east of Arminto makes use of a broad through valley linking the west-northwest oriented Alkali Creek valley with the east oriented Branch Cave Gulch valley. The through valley floor elevation is between 1840 and 1860 meters. Highest elevations south of the through valley and seen in figure 4 are more than 1920 meters, although elevations in the Rattlesnake Hills to the south of figure 4 rise to more than 2500 meters. Highest elevations north of the through valley and seen in figure 4 are more than 2000 meters and much higher elevations are found further north in the Bighorn Mountains. Depending on how the through valley is viewed its depth could be considered to be anywhere from 60 meters to more than 600 meters. Prior to the reversal of south oriented flood flow on the present day Wind River Canyon alignment the through valley was used by east oriented floodwaters flowing from the present day Wind River Basin region to what at that time was the newly eroded and deeper north-northeast oriented South Fork Powder River valley. At that time the Wind River Basin to the west of figure 4 had not been deeply eroded and Wind River Basin elevations were higher than elevations in the South Fork Powder River valley to the east of figure 4. East oriented floodwaters deeply eroded the region between the Bighorn Mountains to the north and the Rattlesnake Hills to the south and created broad and relatively low relief erosion surfaces on the through valley floor seen in figure 4. The reversal of flood flow on the Wind River Canyon alignment beheaded the east oriented flood flow and diverted the floodwaters in a north direction into the Bighorn Basin and then to the newly eroded northeast oriented Yellowstone River valley. Continued flood flow from northwest of the Wind River Basin deeply eroded the Wind River Basin so today Wind River Basin floor elevations west of figure 4 are much lower than the South Fork Powder River valley floor elevations. The west-northwest oriented Alkali Creek drainage route was created by a reversal of floodwaters to flow into the deeper Wind River basin west of figure 4.

Poison Creek-Sand Draw drainage divide area

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

Figure 5 illustrates the Poison Creek-Sand Draw drainage divide area south and slightly west of figure 4 and there is an overlap area with figure 4. The map contour interval for figure 5 is 20 meters. The South Fork Powder River flows in a northeast and east direction across the southeast corner of figure 5 and east of figure 5 turns to flow in a north-northeast direction to the north oriented Powder River. Sand Draw is the southeast oriented tributary joining the South Fork Powder River south and east of Waltman. Poison Creek flows in a northeast direction from near the southwest corner of figure 5 to near the abandoned railroad grade and then turns to flow in a northwest direction to Hiland and then continues in a northwest and west direction to near the northwest corner of figure 5. West of figure 5 Poison Creek flows to the north oriented Wind River (which becomes the north oriented Bighorn River). The highway and abandoned railroad grade make use of a through valley linking the northwest oriented Poison Creek valley with the southeast oriented Sand Draw valley. The through valley floor elevation is between 1880 and 1900 meters. Elevations seen in figure 5 both north and south of the through valley are more than 1940 meters and as described previously elevations in the Bighorn Mountains to the north and the Rattlesnake Hills to the south reach more than 2500 meters. In the local context the through valley is at least 40 meters deep. In the broader regional context the through valley is simply a deeper channel eroded into the floor of a much larger through valley that is more than 600 meters deep. In either context the through valley was eroded by east oriented flood flow moving from the present day Wind River Basin location west of figure 5 to the northeast and north-northeast oriented South Fork Powder River valley. The east oriented flood flow lowered the region between the Bighorn Mountains and the Rattlesnake Hills probably initially as floodwaters flowed to the east and southeast oriented North Platte River valley east and south of figure 5. Headward erosion of the north-northeast oriented South Fork Powder River valley then captured the east oriented flood flow and diverted floodwaters in a north direction to space in the deep “hole” the melting ice sheet was opening up. Headward erosion of the deep northeast oriented Yellowstone River valley next beheaded and reversed flood flow in the Bighorn Basin and created the north oriented Bighorn River, which then captured the southeast oriented Wind River in the Wind River Basin. Capture of the Wind River by the much deeper north oriented north oriented Bighorn River valley deeply eroded the Wind River Basin west of figure 5 and beheaded and reversed east oriented flood flow routes to the north-northeast oriented South Fork Powder River valley. The northwest and west oriented Poison Creek drainage route was established during that flood flow reversal and captured northeast oriented flood flow along the northwest side of the northeast and north-northeast oriented South Fork Powder River valley to create the northeast oriented Poison Creek headwaters drainage route seen in figure 5.

Detailed map of Poison Creek-Sand Draw drainage divide area

Figure 6: Detailed map of Poison Creek-Sand Draw 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 Poison Creek-Sand Draw drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 20 feet. The tiny town of Waltman is located in section 30 near the east center edge of figure 6. Waltman Spring is located near the highway in the southwest corner of section 23 (west of Waltman). Sand Draw headwaters are located slightly south and west of Waltman Spring and Sand Draw drains in an east direction across the south margins of sections 26 and 25 before turning to drain in a southeast direction to the east edge of figure 6 (south of Waltman). South and east of figure 6 Sand Draw joins the northeast oriented South Fork Powder River as a barbed tributary. Adobe Reservoir is located in the west half of section 28 (near the Sand Draw headwaters). South of Adobe Reservoir are headwaters of a north and northwest oriented stream, which flows to the west edge of figure 6 (near highway). West of figure 6 the unnamed stream joins northwest and west oriented Poison Creek, which flows to the north oriented Wind River (and Bighorn River). The abandoned railroad grade north of Adobe Reservoir is located in a through valley linking the northwest and west oriented Poison Creek valley with the southeast oriented Sand Draw valley. The elevation of the road intersection on the through valley floor is shown as 6168 feet. The high point on the hill or butte south of Adobe Reservoir is shown as 6419 feet. Highest elevations north of the through valley and seen in figure 6 are at least 6340 feet, although higher elevations can be found further to the north. These elevations suggest the through valley when viewed locally is at least 172 feet deep. As described in previous discussions much higher elevations are found to the south in the Rattlesnake Hills and even higher elevations are found to the north in the Bighorn Mountains. Elevations in the Rattlesnake Hills approach 8000 feet while Bighorn Mountains elevations exceed 10,000 feet. Looking at the through valley using a big picture regional context the through valley could be considered to be almost 2000 feet deep. Some of that depth may be the result of crustal warping that raised the Bighorn Mountains and Rattlesnake Hills relative to the “valley” between them, although east oriented flood flow was responsible for at least some of that depth prior to the capture of the east oriented flood flow by the reversal of flood flow that created the much deeper north oriented Wind River-Bighorn River drainage route.

Poison Creek-South Fork Powder River drainage divide area

Figure 7: Poison Creek-South Fork Powder River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Poison Creek-South Fork Powder River drainage divide area south and west of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 7 is 20 meters. The Ervay Basin is located near the south edge of figure 7 (slightly west of center). The South Fork Powder River originates in the Ervay Basin and flows in an east direction to the Coalbank Hills and then at Hoff Gap turns to flow in a northeast direction to the northeast corner of figure 7. North and east of figure 7 the South Fork Powder River flows to the north oriented Powder River. Near the center of figure 7 there is well and the north-northeast and northeast oriented stream originating near that well is Poison Creek. North of figure 7 Poison Creek turns to flow in a northwest and west direction and eventually joins the north oriented Wind River, which flows into the Bighorn Basin to become the north oriented Bighorn River. The north oriented stream flowing near the west edge of figure 7 is Deer Creek. North of figure 7 Deer Creek turns to flow in a northwest direction to join west oriented Poison Creek with water eventually reaching the Bighorn River. The east oriented stream flowing along the south edge of the southeast quadrant of figure 7 is Cow Camp Creek, which flows to northeast oriented Wallace Creek (which flows across the southeast corner of figure 7) and east and north of figure 7 Wallace Creek joins the South Fork Powder River. Note how the South Fork Powder River has eroded a valley or water gap (Hoff Gap) across the Coalbank Hills. South Fork Powder River valley floor elevations in that water gap are between 1900 and 1920 meters. Elevations in the Coalbank Hills on either side of the water gap are more than 2020 meters suggesting the water gap is at least 100 meters deep. South of the north oriented Poison Creek headwaters is a north-to-south oriented through valley linking the north oriented Poison Creek valley with the east oriented South Fork Powder River valley. The through valley floor elevation is between 1980 and 2000 meters. The high point in the Coalbank Hills to the east is 2058 meters and Maverick Butte to the west reaches 2123 meters suggesting the through valley is approximately 60 meters deep. Additional through valleys can be seen south and west of Maverick Butte linking the east oriented South Fork Powder River valley with the north oriented Deer Creek valley. The deepest of these through valley has a floor elevation of between 2020 and 2040 meters. Buttes with elevations exceeding 2100 meters can be seen south of the through valley in figure 7 and even higher elevations are located south of figure 7. These elevations suggest the Deer Creek-South Fork Powder River through valley is at least 80 meters deep. These through valleys were eroded by south oriented flood flow moving into the Ervay Basin where it was captured by headward erosion of the east and northeast oriented South Fork Powder River valley. Prior to headward erosion of the South Fork Powder River valley headward erosion of the Wallace Creek valley and tributary valleys had captured the flood flow. Prior to Wallace Creek valley headward erosion the flood flow had been moving to North Platte River tributary valleys.

Detailed map of Poison Creek-South Fork Powder River drainage divide area

Figure 8: Detailed map of Poison Creek-South Fork Powder River 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 Poison Creek Creek-South Fork Powder River drainage divide area seen in less detail in figure 7 above. The map contour interval for figure 8 is 20 feet. The South Fork Powder River flows in an east direction across the Ervay Basin near the south edge of figure 8 from the southwest corner of figure 8 to Hoff Gap (on border between sections 9 and 10) and then turns to flow in a northeast direction to the east center edge of figure 8. Hoff Gap is a water gap cut across the Coalbank Hills. The South Fork Powder River crosses the 6300-foot contour line in Hoff Gap. North and west of Hoff Gap in section 9 elevations rise to 6631 feet. South and east of figure 8 elevations in the Coalbank Hills exceed 6700 feet. These elevations suggest Hoff Gap is at least 331 feet deep. At the one time elevations on both sides of Hoff Gap were as high, if not higher, than the highest Coalbank Hills elevations and the South Fork Powder River valley was able to erode a deep northeast oriented valley headward into the region to capture the south and east oriented flood flow. At least some of the lood flow was moving in south direction to Ervay Basin along the alignment of the present day north oriented Poison Creek headwaters valley seen in figure 8. The Wagner Well is located in the northwest corner of section 32 and north oriented Poison Creek flows in a northwest direction to near the Wagner Well and then turns to flow in a north or north-northeast direction to the north edge of figure 8 (slightly west of center). North of figure 8 Poison Creek turns to flow in a northeast direction before turning to flow in a northwest and west direction to join the north oriented Wind River. A north-to-south oriented through valley links the north oriented Poison Creek valley near the Wagner Well with a south oriented tributary flowing to the east oriented South Fork Powder River in the Ervay Basin. The through valley floor elevation at the road intersection is shown as 6544 feet. Elevations in the Coalbank Hills in section 5 to the east of the through valley rise to 6751 feet. Elevations on Maverick Butte in the southwest quadrant of section 1 rise to 6995 feet. These elevations show the north-to-south oriented through valley is at least 200 feet deep. The through valley was eroded by south oriented flood flow that was captured by headward erosion of the deeper east oriented South Fork Powder River valley. Apparently floodwaters also flowed in a southeast direction from the Wagner Well region to the northeast oriented South Fork Powder River valley on the northeast side of the Coalbank Hills. Northwest-to-southeast oriented through valleys in sections 4 and 33 link the northwest oriented Poison Creek headwaters valley with southeast oriented South Fork Powder River tributary valleys. Floor elevations of these northwest-to-southeast oriented through valleys exceed 6620 feet, which is approximately 80 feet higher than the north-to-south oriented through valley floor elevation to the west. Apparently the deeper north-to-south oriented through captured the southeast oriented flood flow before the reversal of flood flow in the Wind River Canyon beheaded and reversed flood flow routes to the figure 8 region to create the north oriented Poison Creek headwaters drainage route.

Deer Creek-South Fork Powder River drainage divide area

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

Figure 9 illustrates the Deer Creek-South Fork Powder River drainage divide area west and slightly south of figure 7 and includes a large overlap area with figure 7. The map contour interval for figure 9 is 20 meters. The Coalbank Hills and Hoff Gap are located north and east of the Ervay Basin. Maverick Butte is located north of the Ervay Basin. The South Fork Powder River flows in a south and then east direction from the southwest margin of Maverick Butte to Hoff Gap and then turns to flow in a northeast direction to the north edge of figure 9 (east half). North and east of figure 9 the South Fork Powder River joins the north oriented Powder River. Cyclone Ridge is located along the southwest rim of the Ervay Basin. The northwest-to-southeast oriented ridge located south and east of Cyclone Ridge is the northwest end of the Rattlesnake Hills. Deer Creek flows in a northwest and north-northwest direction along and from the southwest margin of the Rattlesnake Hills to the north edge of figure 9 (near northwest corner) and north of figure 9 turns to flow in a northwest direction to join west oriented Poison Creek, which flows to the north oriented Wind River-Bighorn River. Note in the region south and west of Maverick Butte a broad through valley linking the north-northwest oriented Deer Creek valley with the east oriented South Fork Powder River valley. The through valley is defined on the north by Maverick Butte and on the south by Cyclone Ridge. Lowest points on the through valley floor have elevations of between 2020 and 2040 meters. The high point on Maverick Butte is 2123 meters and high points on Cyclone Ridge exceed 2160 meters with much higher elevations located south and east of Cyclone Ridge. These elevations suggest the through valley is at least 80 meters deep. Elevations in the Rattlesnake Hills generally exceed 2300 meters and some elevations exceed 2500 meters. If the Deer Creek-South Fork Powder River through valley is looked as simply a deeper channel eroded into the floor of a much broader and deeper through valley between the Bighorn Mountains to the north and the Rattlesnake Hills to the south the through valley depth in the Deer Creek-South Fork Powder River through valley area could be as much as 500 meters. However the through valley is viewed it was eroded by southeast and east oriented flood flow moving from the present day north oriented Wind River Basin location (although at that time the Wind River Basin had not been eroded) to what at that time was the deeper northeast and north-northeast oriented South Fork Powder River valley.

Detailed map of Deer Creek-South Fork Powder River drainage divide area

Figure 10: Detailed map of Deer Creek-South Fork Powder 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 Deer Creek-South Fork Powder River drainage divide area seen in less detail in figure 9 and shows the west end of the Ervay Basin. The map contour interval for figure 10 is 20 feet. Maverick Butte is located near the north center edge of figure 10. The South Fork Powder River originates near the south edge of section 2 (west of the south end of Maverick Butte) and flows in a south direction to the southeast corner of section 11 where it turns to flow in an east direction across the Ervay Basin (with a jog to the northeast in section 7). The northwest, west, and north oriented stream originating on Maverick Butte and flowing into section 2 and then to the north edge of figure 10 (directly north of the south oriented South Fork Powder River headwaters) is a north oriented tributary to the north oriented Poison Creek headwaters. In section 2 this north oriented Poison Creek tributary valley is linked by a through valley with the south oriented South Fork Powder River headwaters valley. The through valley provides evidence of a south oriented flood flow channel to the east oriented South Fork Powder River valley prior to the reversal of flood flow that created the north oriented Poison Creek headwaters drainage route. In the northwest quadrant of section 11 are the deepest of several through valleys linking west oriented Deer Creek tributary valleys with the east oriented South Fork Powder River valley. The floor elevation of the deepest through valley at the road intersection is 6682 feet. Maverick Butte to the northeast rises to 6995 feet and the highest elevations on Cyclone Ridge near the south edge of figure 10 exceed 7000 feet. These elevations suggest the through valley is at least 300 feet deep. Again the through valley could be viewed from a much bigger viewpoint with the Bighorn Mountains forming the north wall and the Rattlesnake Hills forming the south wall. If so elevations in the Rattlesnake Hills south and east of figure 10 approach 8000 feet and elevations in the Bighorn Mountains are even higher suggesting the through valley could be as deep as 1300 feet. How much of that depth should be attributed to crustal warping that raised the Bighorn Mountains and Rattlesnake Hills relative to the valley floor between them and how much of the through valley depth should be attributed to flood flow erosion that stripped great thicknesses of sedimentary strata from the valley floor is hard to determine. Regardless of how the through valley depth is attributed there is no question large volumes of south, southeast, and east oriented floodwaters flowed from north and west of the figure 10 area to the east and northeast oriented South Fork Powder River 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.

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