Separation Creek-Little Sage Creek drainage divide area landform origins along the Great Divide Basin east rim, Wyoming, USA

Authors

 

Abstract:

Topographic map evidence in the Separation Creek-Little Sage Creek drainage divide area along the Wyoming Great Divide Basin east rim is illustrated and interpreted to determine erosional landform origins. The Great Divide Basin is a large region of internal drainage along the east-west continental divide in south central Wyoming and Separation Creek is a southwest, north, and south oriented stream in the eastern Great Divide Basin. East of the Great Divide Basin and of Separation Creek is the north oriented North Platte River, which further to the north flows around the northwest end of the Laramie Mountains and then flows in a southwest direction into Nebraska with water eventually reaching the Gulf of Mexico. South of the eastern Great Divide Basin and of the Separation Creek headwaters is west and south oriented Muddy Creek, which flows to the west and southwest oriented Little Snake River with water then flowing to the Yampa, Green, and Colorado Rivers and eventually reaching the Pacific Ocean. Little Sage Creek is a south and east oriented North Platte River tributary. Through valleys in the eastern Great Divide Basin link the North Platte River valley and tributary valleys with the Muddy Creek and tributary valleys. These through valleys were eroded as a complex of south oriented flood flow channels at a time when Wyoming mountain ranges were beginning to emerge. At that time immense melt water floods flowed in a south direction from the western margin of a thick North American ice sheet in western Canada to and across Wyoming. Mountain ranges and other geologic structures emerged as floodwaters deeply eroded surrounding basins and valleys and as ice sheet related crustal warping raised mountain ranges and geologic structures and the entire Separation Creek and North Platte River headwaters areas. Headward erosion of a deep southeast oriented valley around the northwest end of the Laramie Mountains beheaded south oriented flood flow on the present day north oriented north oriented North Platte River alignment. Floodwaters on the north end of the beheaded flood flow route reversed flow direction to flow in a north direction to the much deeper east and southeast oriented valley and to create the north, east, and southeast oriented North Platte River drainage route. A similar flood flow reversal created the north oriented Separation Creek drainage route. The North Platte River flood flow reversal and headward erosion of the deep east oriented Sweetwater River valley north of the Great Divide Basin ended south oriented flood flow across the eastern Great Divide Basin. Topographic map evidence supporting this flood origin interpretation includes the through valleys, barbed tributaries, and elbows of capture, which today include U-turns made by numerous 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 Separation Creek-Little Sage Creek drainage divide area landform origins along the Wyoming Great Divide Basin east rim. 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 Separation Creek-Little Sage Creek drainage divide area landform evidence along the Wyoming Great Divide Basin east rim will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Separation Creek-Little Sage Creek drainage divide area along the Great Divide Basin east rim location map

Figure 1: Separation Creek-Little Sage Creek drainage divide area along the Wyoming Great Divide Basin east rim 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 Separation Creek-Little Sage Creek drainage divide area along the Wyoming Great Divide Basin east rim and illustrates a region in south central Wyoming with Colorado and Utah being located south of Wyoming (Utah is in the southwest corner of figure 1). The Great Divide Basin is labeled and is a large region of internal drainage located in southern Wyoming. West of the Great Divide Basin is the south oriented Green River drainage basin, which south of figure 1 drains to the southwest oriented Colorado River with water eventually reaching the Pacific Ocean. East of the Great Divide Basin is the North Platte River drainage basin. The North Platte River flows in a north-northwest direction between the Medicine Bow and Sierra Madre Mountains from northern Colorado to slightly north of Fort Steele, Wyoming. From the Fort Steele area the North Platte River makes a jog to the northeast and then flows in a north and northeast direction to the northwest end of the Laramie Mountains near Casper. At Casper the North Platte River turns to flow in an east and southeast direction to the east edge of figure 1 (north half) and east of figure 1 flows into Nebraska with water eventually reaching the Mississippi River and the Gulf of Mexico. The Sweetwater River originates in the Wind River Range (in northwest quadrant of figure 1) and flows in a south-southeast direction to near South Pass. At South Pass the Sweetwater River turns to flow in an east-northeast and east direction (north of the Great Divide Basin) to make a final turn in a south direction to join the north oriented North Platte River at Pathfinder Reservoir as a barbed tributary. South of the Great Divide Basin Muddy Creek originates along the northwest edge of the Sierra Madre Mountains and flows in a northwest, southwest, and south direction to Baggs where it joins the west and southwest oriented Little Snake River, which south of figure 1 flows to the west oriented Yampa River, which in turn flows to the Green River. Little Sage Creek is shown in figure 1, but is not labeled, and originates just north of the Muddy Creek headwaters and then flows in an east direction (north of the Sierra Madre Mountains) to join the north oriented North Platte River. Separation Creek is also shown, but not labeled, in figure 1 and originates just north of the Little Sage Creek headwaters and then flows in a north direction west of Rawlins before making a U-turn north of Rawlins and then ending. The Separation Creek-Little Sage Creek drainage divide area along the Great Divide Basin east rim is located in the Rawlins, Wyoming region and is primarily east and south of Separation Creek, north of Little Sage Creek, and west of the North Platte River.

Wyoming drainage routes developed during immense melt water floods originating along the western margin of a thick North American ice sheet and which were flowing from western Canada to and across Wyoming. At least at first Wyoming mountain ranges and other geologic structures had not emerged and floodwaters could freely flow across what are today major topographic barriers. Mountain ranges and other structures emerged as floodwaters deeply eroded surrounding basins and valleys and as ice sheet related crustal warping raised the mountain ranges and structures and the entire region seen in figure 1. The present day north oriented North Platte River drainage route west of the Laramie Mountains originated as a south oriented flood flow channel (actually multiple south oriented flood flow channels, but to keep this discussion brief they will be referred to in this essay as a single flood flow channel). Headward erosion of the much deeper southeast and east oriented North Platte River valley around the Laramie Mountains northwest end beheaded the south oriented flood flow channel west of the Laramie Mountains. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to flow in a north direction to the much deeper east and southeast oriented North Platte River valley and to create the north, east, and southeast oriented North Platte River drainage route. The east oriented Sweetwater River valley had eroded headward from the south oriented flood flow channel on the present day north oriented North Platte River alignment to capture south oriented flood flow routes crossing the present day Great Divide Basin to reach what was then the actively eroding Muddy Creek valley and tributary valleys, which had eroded headward from the Little Snake River valley. The flood flow reversal on the North Platte River alignment probably took place as the Sweetwater River valley was still eroding headward toward the Wind River Mountains. Subsequently headward erosion of the deep northeast oriented Yellowstone River valley across Montana (north of figure 1) beheaded and reversed south oriented flood flow routes to the newly eroded Sweetwater River valley. The deep Yellowstone River valley was eroding headward across the ice-marginal melt water flood flow from space at the south end of the deep “hole” the ice sheet had occupied and that was being opened up by ice sheet melting.

Detailed location map for Separation Creek-Little Sage Creek drainage divide area

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

Figure 2 provides a more detailed location map for the Separation Creek-Little Sage Creek drainage divide area. The North Platte River flows in a northwest, north-northeast, north-northwest, northeast, and north direction from the southeast corner of figure 2 to near the northeast corner of figure 2. North of figure 2 the North Platte River flows in a north, northeast, east, and southeast direction around the Laramie Mountains northwest end with water eventually reaching the Gulf of Mexico. The southern end of Seminoe Reservoir floods the North Platte River valley near the north edge of figure 2. The Great Divide Basin east rim is shown with a labeled dashed line that extends from the north edge of figure 2 (east half) to and around Rawlins and then south to near Bridger Pass (north of south center edge of figure 2). The Great Divide Basin west rim extends westward from near Bridger Pass to the west edge of figure 2 (south half). The dashed line extending in an east and south direction from near Bridger Pass is the east-west continental divide. West of the continental divide and south of the Great Divide Basin west rim are Muddy Creek headwaters. McKinney Creek is a Muddy Creek tributary located south of Bridger Pass. Little Sage Creek headwaters are located near Bridger Pass and flow in an east-northeast, east-southeast, and east direction to join the north oriented North Platte River. Sugar Creek originates north of Separation Peak (near Bridger Pass) and flows in a northeast direction to Rawlins and then in an east and northeast direction to join the North Platte River. In the Severson Flats area (north of Little Sage Creek) northeast oriented Iron Springs Creek and its northeast oriented tributaries drain to the North Platte River. West of Bridger Pass and inside the Great Divide Basin are southwest oriented headwaters of Separation Creek. After flowing in a southwest direction Separation Creek makes a U-turn to flow in a north, west, and north-northeast direction to Daleys Ranch and then in a north-northwest direction along Separation Flats before turning in an east-northeast direction and then in a south and southeast direction to Separation Lake. The northern Separation Creek U-turn is around the north end of Rendle Hill. Dry Lake is located south of Separation Lake and today no drainage route links the two lakes. East of Separation Lake and Dry Lake are the Haystack Mountains, which are located along the Great Divide Basin eastern rim. A northwest and west oriented Separation Creek tributary in the Separation Flats area is Indian Springs Creek. Fillmore Creek is an interesting Separation Creek tributary and originates near the Separation Creek southern U-turn (west of Bridger Pass) and flows in a northwest, north, and northeast direction through the town of Cherokee to join Separation Creek north of Daleys Ranch. As will be seen in the topographic maps below Fillmore Creek and Separation Creek headwaters valleys are linked by through valleys with Muddy Creek headwaters valleys providing evidence of what were once south oriented anastomosing flood flow channels crossing the eastern Great Divide Basin.

Separation Creek-Separation Lake drainage divide area

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

Figure 3 provides a reduced size topographic map of the Separation Creek-Separation Lake drainage divide area. The map contour interval for figure 3 is 20 meters. Rendle Hill is the upland in the center of figure 3 and extends in a south direction to the south edge of figure 3. Separation Creek flows in a north direction from near the southwest corner of figure 3 to near the west center edge of figure 3 and then turns in an east-northeast direction to the Separation Flats area north of Rendle Hill, before turning in a south and southeast direction to end in Separation Lake. In other words Separation Creek makes a U-turn around the north end of Rendle Hill. South of Separation Lake, but not linked by a drainage route to Separation Lake, is Dry Lake. Dry Lake and Separation Lake are located in a north to south oriented through valley bounded on the east by the Haystack Mountains and on the west by Rendle Hill. South and east of figure 3 the Separation Lake-Dry Lake through valley continues and converges with the present day north oriented North Platte River valley (seen in figure 4). West of Rendle Hill north oriented Cold Spring Draw and Shamrock Draw drain to the east-northeast oriented Separation Creek drainage segment. North of figure 3 is the low relief Boggy Meadows area, which is linked by through valleys with the North Platte River and Sweetwater River tributary valleys. At one time large volumes of floodwaters flowed in a south direction from the Boggy Meadows area to the region north of Rendle Hill where the floodwaters split into two diverging flood flow channels. The eastern flood flow channel moved in a south and southeast direction along the through valley between Rendle Hill and the Haystack Mountains to a south oriented flood flow channel on the present day north oriented North Platte River drainage route. The other flood flow channel moved in a southwest and south direction to the west of Rendle Hill and then flowed in a south direction on the present day north oriented Separation Creek alignment. South of figure 3 (and seen in figures 8 and 9) the floodwaters flowed to actively eroding Muddy Creek headwaters and tributary valleys. The present day north oriented Shamrock Draw and Cold Spring Draw valleys also originated as south oriented flood flow channels. Headward of the deeper east oriented Sweetwater River valley north of figure 3 and the reversal of flood flow on the North Platte River alignment ended all south oriented flood flow to and across the figure 3 region. The reversal of flood flow on the present day north oriented Separation Creek alignment may have been related to the North Platte River flood flow reversal and was probably greatly aided by ice sheet related crustal warping that was raising the Separation Creek and North Platte River headwaters areas.

Dry Lake-North Platte River drainage divide area

Figure 4: Dry Lake-North Platte River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 provides a topographic map of the Dry Lake-North Platte River drainage divide area south and west of figure 4 and includes an overlap area with figure 4. The map contour interval for figure 4 is 20 meters. The North Platte River flows in a north-northwest direction from the southeast corner of figure 4 to a deep water gap across the Fort Steele Breaks (or the Haystack Mountains south end) and then turns to flow in east and east-northeast direction to the east edge of figure 4. The North Platte River water gap is approximately 300 meters deep. Dry Lake is located near the north edge of the northwest quadrant of figure 4 and is located in the through valley between Rendle Hill to the west and the Haystack Mountains to the east. The through valley floor elevation is everywhere less than 2000 meters while high points on Rendle Hill and in the Haystack Mountains exceed 2300 meters. These elevations suggest the through valley is at least 300 meters deep. The through valley orientation follows the regional geologic structure orientations, but the through valley is also a water eroded valley. The North Platte River water gap is evidence the North Platte River course began with south oriented floodwaters flowing on an erosion surface as high if not higher than the tops of Rendle Hill and the Haystack Mountains today. The south oriented floodwaters eroded the deep through valley linking the Separation Lake area with the present day north oriented North Platte River valley south of figure 4. The flood flow reversal on the North Platte River alignment occurred in multiple steps and it is possible south and southwest oriented flood flow continued to move between Rendle Hill and the Haystack Mountains to the newly reversed North Platte River drainage route seen in figure 4. If so floodwaters would have made a U-turn around the south end of the Haystack Mountains. Relief on the through valley floor is so low that by using only evidence seen in figures 3 and 4 a case could be made for the opposite situation so other interpretations are also possible. Regardless of flood flow movements as the North Platte River direction reversal took place the valleys were originally eroded as a complex of anastomosing south oriented flood flow channels and all flood flow in the valley between Rendle Hill and the Haystack Mountains was eventually beheaded, which ended all flow in the through valley.

Indian Spring Creek-Fourmile Draw drainage divide area

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

Figure 5 illustrates the Indian Spring Creek-Fourmile Draw drainage divide area east and slightly south of figure 3 and there is an overlap area with figure 3. The map contour interval for figure 5 is 20 meters. Separation Creek flows in a north-northeast and north direction from the southwest corner of figure 5 to the north edge of figure 5 (west half). Indian Spring Creek is the north-northwest and west oriented stream joining Separation Creek near the north edge of figure 5. Fillmore Creek is unlabeled northeast oriented stream flowing from the west edge of figure 5 (just north of highway) to join Separation Creek in the west center region of figure 5. Hadsell Draw (“Draw” in figure 5) is the north-northeast oriented drainage route flowing from the south edge of figure 5 (west half) to the town of Hadsell and then turning in west direction to join north oriented Separation Creek. Sugar Creek flows from the south edge of figure 5 (east of center) along the east side of Hogback Lake and then turns in an east direction to flow to the east center edge of figure 5 and east of figure 5 turns in a northeast direction to join the North Platte River. Cherokee Creek is a south-southeast oriented stream joining Sugar Creek west of Rawlins. Cherokee Peak is west of Cherokee Creek and Fourmile Draw drains in a south-southeast, southeast, and south-southwest direction from west of Cherokee Peak to west of Hogback Lake. A north to south oriented through valley links the north-northwest oriented Indian Spring Creek headwaters valley with the south-southeast oriented Fourmile Draw valley. The through valley is defined by two contour lines on the west side and is at least 20 meters deep. An even deeper through valley links the Indian Spring Creek headwaters valley with the Cherokee Creek headwaters valley and while not completely seen in figure 5 is almost 100 meters deep. These through valleys are on the west side of Rendle Hill and were eroded by south oriented flood flow moving into the region north of Hogback Lake. At one time the floodwaters then flowed in a southwest direction along the present day northeast oriented Hadsell Draw and Sugar Creek alignments. However, the southwest oriented flood flow was beheaded and reversed so the floodwaters flowed in an east direction in diverging and converging flood flow channels to the North Platte River valley. The Sugar Creek valley through Rawlins was one of the diverging flood flow channels and the State Penitentiary is located in another diverging flood flow channel. The Great Divide Basin east rim in the Hogback Lake-Hadsell area is crossed by a subtle west to east oriented through valley. Hogback Lake drains to Sugar Creek and then to the North Platte River. Hadsell Draw drains to Separation Creek, which is a Great Divide Basin drainage route and which never reaches an external drainage route. The railroad follows the through valley route and crosses almost no contour lines. Depending on how the through valley depth is measured the through valley could be as much as 200 meters deep. The through valley provides evidence of more diverging and converging flood flow channels linking the present day Separation Creek and North Platte River valleys.

Separation Creek-Sugar Creek drainage divide area

Figure 6: Separation Creek-Sugar Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 provides a topographic map of the Separation Creek-Sugar Creek drainage divide area south and west of figure 3 and includes an overlap area with figure 3. The map contour interval for figure 6 is 20 meters. Atlantic Rim is the southeast-facing escarpment crossing the southeast corner of figure 6. Little Sage Creek originates in the Beckman Canyon area on Atlantic Rim and then flows in an east direction to near the southeast corner of figure 6. East of figure 6 Little Sage Creek flows to the North Platte River. Ram Canyon is located west of the Beckman Canyon headwaters and of Separation Peak and is where Sugar Creek originates. Sugar Creek then flows in a north-northeast and northeast direction from Ram Canyon to the northeast corner of figure 6. North and east of figure 6 Sugar Creek turns to flow in an east direction through Rawlins and then in a northeast direction to join the North Platte River. Scotty Canyon is located south of Ram Canyon and a Separation Creek tributary originates in Scotty Canyon and then flows in a northwest and west-southwest direction to join Separation Creek. Separation Creek flows in a northeast direction from the south edge of figure 6 (west half) to join the west oriented tributary originating in Scotty Canyon and then turns to flow in a west, north-northwest, and north-northeast direction to the north edge of figure 6 (west half). As seen in earlier figures north of figure 6 Separation Creek flows in a north, east-northeast, and south direction to Separation Lake where Separation Creek ends. Fillmore Creek is the northeast oriented Separation Creek tributary flowing across the northwest corner of figure 6. A well-defined through valley near the mouths of Ram Canyon and Scotty Canyon links the present day northeast oriented Sugar Creek valley with the present day northeast oriented Separation Creek valley south of figure 6. The through valley floor elevation is shown as being 2206 meters. Elevations west of the through valley rise to at least 2280 meters and much higher elevations are found to the east. These elevations suggest the through valley is at least 74 meters deep. The through valley was probably initially eroded by southwest oriented flood flow, although later in its history it may have been eroded by northeast oriented flood flow. Some of the northeast oriented flood flow may have been moving in a south-southwest direction on the Separation Creek alignment to west and then making a U-turn to flow in a northeast direction on the Sugar Creek alignment.

Sugar Creek-Little Sage Creek drainage divide area

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

Figure 7 illustrates the Sugar Creek-Little Sage Creek drainage divide area east and slightly south of figure 6 and includes an overlap area with figure 6. The map contour interval for figure 7 is 20 meters. Atlantic Rim extends in a northeast direction from near the southwest corner of figure 7. Ram Canyon is located north of the southwest corner of figure 7 and Sugar Creek originates at Ram Canyon. Sugar Creek flows in a north-northeast and northeast direction from Ram Canyon to the north edge of figure 7 (west half-just west of Coal Mine Ridge). North of figure 7 Sugar Creek turns to flow in an east and northeast direction to join the North Platte River. Separation Peak is near Ram Canyon and Beckman Canyon is located south and east of Separation Peak. Little Sage Creek originates in Beckman Canyon and then flows in an east direction near the south edge of figure 7 to the southeast corner of figure 7 and then to join the North Platte River. Eightmile Lake Basin is a north to south oriented basin or through valley in the center of figure 7 and links the east oriented Little Sage Creek valley with valleys of north oriented Sugar Creek tributaries. Eightmile Lake Basin appears to be located in the eroded core of an anticlinal structure. The Atlantic Rim escarpment forms the Eightmile Lake Basin west wall while high points on the east wall include Sheep Mountain and Chokecherry Knob. A through valley near Fivemile Hole (near north center edge of figure 7) has an elevation between 2200 and 2220 meters. Elevations on Atlantic Rim rise in a south direction to more than 2500 meters. Elevations on Sheep Mountain rise to more than 2420 meters. These elevations suggest the Eightmile Lake Basin through valley is at least 200 meters deep. The Eightmile Lake Basin orientation is determined by the anticline orientation, however the Eightmile Lake Basin is also an erosional landform and was eroded by south oriented flood flow. At the time the Eightmile Lake Basin was eroded there was no deep east oriented Sugar Creek valley north of figure 7 and floodwaters were flowing on an erosion surface at least as high, if not higher, than the Fivemile Hole through valley floor elevation. Floodwaters initially flowed through the Eightmile Lake Basin in a south direction to Miller Hill, which is south of figure 7 (see figure 8) where some floodwaters flowed in a southwest direction to actively eroding Muddy Creek tributary valleys while other floodwaters flowed in a southeast direction to a south oriented flood flow channel on the present day north oriented North Platte River alignment. Headward erosion of the east oriented Little Sage Creek valley from the North Platte River valley captured the southwest, southeast, and south oriented flood flow. Erosion of the Eightmile Lake Basin on the Atlantic Rim east or southeast side probably occurred before floodwaters deeply eroded the Sugar Creek valley and the region to the northwest. Beckman Canyon was probably eroded by floodwaters spilling in a south or southeast direction across Atlantic Rim into the deeper Eightmile Lake Basin and east-oriented Little Sage Creek valley.

Separation Creek-Muddy Creek drainage divide area

Figure 8: Separation Creek-Muddy Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 provides a topographic map of the Separation Creek-Muddy Creek drainage divide south and west of figure 7 and includes an overlap area with figure 7. The map contour interval for figure 8 is 20 meters. Atlantic Rim extends in a southwest direction from the north edge of figure 8 (near northeast corner). Beckman Canyon is located near the northeast corner of figure 8 and Little Sage Creek flows in an east direction from the mouth of Beckman Canyon to the east edge of figure 8 and east of figure 8 joins the North Platte River. The northeast oriented stream flowing between the Atlantic Rim and Miller Hill is Emigrant Creek, which east of figure 8 joins Little Sage Creek. Miller Hill is the north end of the Sierra Madre Mountains and the east-west continental divide extends across Miller Hill. Drainage north and east of the continental divide is to the North Platte River with water eventually reaching the Gulf of Mexico. Drainage south and west of the continental divide is to Muddy Creek, which flows to the Little Snake River with water eventually reaching the Green and Colorado Rivers and the Pacific Ocean. Bridger Pass is located on the continental divide and is west of Miller Hill and east of the Atlantic Rim ridge. South of Bridger Pass is McKinney Creek, which flows to northwest and west-southwest oriented Muddy Creek with Muddy Creek flowing to the southwest corner of figure 8. South and west of figure 8 Muddy Creek turns in a south direction to join the west and southwest oriented Little Snake River. The Bridger Pass elevation is shown as being 2286 meters. Elevations on Miller Hill exceed 2560 meters and high points on the Atlantic Rim ridge to the west exceed 2540 meters in elevation. These elevations suggest Bridger Pass is a 280-meter deep northeast to southwest oriented through valley linking the North Platte River valley with the Muddy Creek valley. The through valley was eroded by southwest oriented flood flow prior to headward erosion of the east oriented Little Sage Creek valley and the reversal of flood flow on the North Platte River alignment. Jep Canyon is west of Bridger Pass. Separation Creek originates south of Scotty Canyon (west of Beckman Canyon) and flows in a south and south-southwest direction through Jep Canyon before turning in a north and northeast direction to join the northwest and southwest oriented stream emerging from Scotty Canyon and then to flow in a west and north direction to the north edge of figure 8 (west half). North of figure 8 as seen in earlier figures Separation Creek eventually flows around the north end of Rendle Mountain and then ends in Separation Lake. West of the Separation Creek U-turn (at the south end of Jep Canyon) is a north to south oriented through valley linking the north oriented Separation Creek valley with the south oriented Alamosa Gulch valley (with Alamosa Gulch draining to west-southwest oriented Muddy Creek) and an east to west oriented through valley linking the north oriented Separation Creek valley and the south oriented Alamosa Gulch valley with the west, northwest, and west oriented Fillmore Creek valley (with Fillmore Creek flowing to the west edge of figure 8 and then turning in a north and northeast direction to join Separation Creek north of figure 8).  These through valleys provide evidence of what were once south oriented diverging and converging flood flow channels in a giant anastomosing channel complex that was eroded into the region. Other through valleys can be found in the region and can be used to describe many additional drainage history details.

Detailed map of Fillmore Creek-Alamosa Gulch drainage divide area

Figure 9: Detailed map of Fillmore Creek-Alamosa Gulch drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 provides a detailed topographic map of the Fillmore Creek-Alamosa Gulch drainage divide area seen in less detail in figure 8. The map contour interval for figure 9 is 20 feet. Separation Creek flows in a southwest direction from the east edge of figure 9 (north half) into the southeast corner of section 11 and then makes a U-turn to flow in a north-northwest direction to the north edge of figure 9 (east half). North of figure 9 Separation Creek eventually ends in Separation Lake. Fillmore Creek originates near the corner of sections 3, 4, 9, and 10 and then flows in a west and northwest direction to the north edge of figure 9 (near northwest corner). North and west of figure 9 Fillmore Creek eventually turns to flow in a northeast direction and eventually joins Separation Creek. A southwest to northeast oriented through valley crossing the section 3 and 4 boundary links the north oriented Separation Creek valley with the west oriented Fillmore Creek valley. The through valley floor elevation is between 7160 and 7180 feet. Elevations in the southwest corner of section 33 to the northwest rise to more than 7540 feet and elevations to the west rise much higher suggesting the through valley is at least 360 feet deep. A north to south oriented through valley in the northwest corner of section 10 crosses the continental divide and links the west oriented Fillmore Creek valley with the south oriented Alamosa Gulch valley, which drains to west-southwest oriented Muddy Creek (south of figure 9). This north to south oriented through valley is interesting because appears to be one channel in what may have been a north to south oriented anastomosing channel complex in the east half of section 9 and near the west edge of section 10. Today the continental divide extends in a south direction along the divide between what were probably diverging and converging south oriented flood flow channels. The drainage history in this region probably began with south oriented flood flow moving to the actively eroding west oriented Muddy Creek valley south of figure 9. At that time the geologic structure along the east edge of figure 9 was probably still emerging and floodwaters were flowing on an erosion surface that looked very different from the surface seen today. The south oriented Alamosa Gulch valley eroded headward from the Muddy Creek valley. A reversal of flood flow on the north end of the flood flow channel supplying floodwaters to the actively eroding Alamosa Gulch valley captured southeast and east oriented flood flow moving in the present day west and northwest oriented Fillmore Creek valley and beheaded the south oriented flood flow route to Alamosa Gulch. The captured flood flow on the Fillmore Creek alignment then made a U-turn to flow in a north direction on the newly reversed Separation Creek alignment. Subsequently flood flow on the Fillmore Creek alignment was beheaded and reversed to create the west and northwest oriented Fillmore Creek drainage route seen in figure 9.

Detailed map of Emigrant Creek-McKinney Creek drainage divide area

Figure 10: Detailed map of Emigrant Creek-McKinney Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 provides a detailed topographic map of the Emigrant Creek-McKinney Creek drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 20 feet. Separation Creek flows in a south-southwest direction in Jep Canyon across the northwest corner of figure 10 and west of figure 10 turns to flow in a north direction as seen in figures 8 and 9. Atlantic Rim is the ridge extending from near the southwest corner of figure 10 to the north center edge of figure 10. Miller Hill is located in the southeast quadrant of figure 10 and marks the north rim of the Sierra Madre Mountains. A deep northeast to southwest oriented through valley is located between the Atlantic Rim and Miller Hill and extends from the northeast quadrant of figure 10 to the south edge of figure 10 (west half). The north end of the through valley is drained by northeast oriented Emigrant Creek, which flows to the north edge of figure 10 (east half) and north of figure 10 flows to east oriented Little Sage Creek, which then flows to the north oriented North Platte River with water eventually reaching the Gulf of Mexico. The through valley south end is drained by south oriented streams flowing to south oriented McKinney Creek, which flows to west and south oriented Muddy Creek with water eventually flowing to the Pacific Ocean. Bridger Pass in the northeast quadrant of section 8 (north and west of center of figure 10) is the deepest point on the through valley floor. The elevation at Bridger Pass is shown as being 7532 feet. The continental divide is shown with a labeled dashed line and can be seen crossing the through valley at Bridger Pass. To the east continental divide elevations rise to more than 8400 feet on Miller Hill. To the west continental divide elevations rise to more than 8340 feet in section 7. These elevations suggest Bridger Pass is approximately 800 feet deep. This 800-foot deep northeast to southwest oriented through valley was eroded by southwest oriented flood flow moving to the actively eroding Muddy Creek valley, which had eroded headward from the Little Snake River valley with the floodwaters then flowing to the Yampa, Green, and Colorado River valleys. The through valley orientation was determined by the orientations of the regional geologic structures, but the valley is a water-eroded valley. At the time floodwaters were flowing in southwest direction in the through valley floodwaters were also flowing in a south direction on the present day north oriented North Platte River alignment east of figure 10. The reversal of flood flow on the North Platte River alignment ended southwest oriented flood flow in the through valley. Floodwaters on the northeast end of the through valley reversed flow direction to create the northeast oriented Emigrant Creek drainage basin.

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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