Chugwater Creek-Horse Creek drainage divide area landform origins in the Wyoming and Nebraska Goshen Hole region, USA

Authors

 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the Chugwater Creek-Horse Creek drainage divide area in the Wyoming and Nebraska Goshen Hole region. Goshen Hole is a large and deep east oriented escarpment surrounded basin located between the southeast oriented North Platte River valley and the north to south oriented Laramie Mountains. Horse Creek originates on the west edge of the Laramie Mountains and flows across the Laramie Mountains and then in an east-northeast direction on the south side of the Goshen Hole basin before turning to flow in a north and northeast direction across the Goshen Hole Basin floor to reach the North Platte River. Chugwater Creek headwaters are north of the Horse Creek headwaters and originate on the west edge of the Laramie Mountains and flow in east directions to the east side of the Laramie Mountains and then turn to flow in a northeast and north direction between the Laramie Mountains and the Goshen Hole Rim to join the east and northeast oriented Laramie River. The Laramie River originates in Colorado and flows in a north direction on the west side of the Laramie Mountains before turning to flow in an east and northeast direction across the Laramie Mountains and then in an east and northeast direction to join the southeast oriented North Platte River north of Goshen Hole. Multiple east and northeast oriented valleys cross the Laramie Mountains in the region west of the east-facing Goshen Hole escarpment. A north to south oriented through valley on the east side of the Laramie Mountains links the northeast and north oriented Chugwater Creek valley with the east-northeast oriented Horse Creek valley and with south and east oriented South Platte River tributary valleys further to the south. Goshen Hole is interpreted to have been eroded by east oriented flood flow moving from west of the Laramie Mountains to the deep North Platte River valley prior to headward erosion of the Laramie River valley. Floodwaters were derived from the western margin of a thick North American ice sheet and flowed from western Canada to and across Wyoming at a time when the Laramie Mountains were still emerging. At that time the Laramie Mountains did not stand high above the Laramie Basin to the west and floodwaters could easily flow from the Laramie Basin in east directions to what were then actively eroding and deep South and North Platte River valleys. Headward erosion of the deep east oriented Goshen Hole valley was slowed when it encountered a region of erosion resistant bedrock, which enabled the north oriented Chugwater Creek valley to erode headward (from the east and northeast oriented Laramie River valley) along the west margin of the erosion resistant bedrock region as it captured the east oriented flood flow and also captured a newly formed northeast oriented flood flow channel leading to deep the Goshen Hole valley. Capture of the northeast oriented flood flow channel enabled the deep north oriented Chugwater Creek valley to behead and reverse a south oriented flood flow channel, which had eroded headward from the South Platte River valley. Headward erosion of the deep north oriented Horse Creek valley from the deep east oriented Goshen Hole valley captured east oriented flood flow routes south of Goshen Hole and also the south oriented flood flow channel that had eroded headward from the South Platte River valley. Headward erosion of the deep Laramie River valley and other deep valleys across the Laramie Mountains captured flood flow in the Laramie Basin to create the north oriented Laramie River drainage route there. The Laramie Mountains emerged as floodwaters deeply eroded the region and as ice sheet related crustal warping raised the mountain mass and the entire region.

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 Chugwater Creek-Horse Creek drainage divide area landform origins in the Wyoming and Nebraska Goshen Hole region. 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 Chugwater Creek-Horse Creek drainage divide area landform evidence in the Wyoming and Nebraska Goshen Hole region will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Chugwater Creek-Horse Creek drainage divide area location map

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

Figure 1 provides a location map for the Chugwater Creek-Horse Creek drainage divide area in the Wyoming and Nebraska Goshen Hole region and illustrates a region in southeastern Wyoming with a region in western Nebraska east of Wyoming and with Colorado located immediately to the south of figure 1. The Laramie Mountains extend in a southeast and south direction from the northwest corner of figure 1 to the south edge of figure 1. The North Platte River originates in Colorado and flows in a north direction west of figure 1 and then around the northwest end of the Laramie Mountains before flowing in a southeast direction from the north edge of figure 1 (west half) to the east edge of 1 (south half). The Laramie River flows in a north and northeast direction from the south edge of figure 1 (near southwest corner) to the city of Laramie and then in a north direction before turning in an east and northeast direction to flow across the Laramie Mountains. Once east of the Laramie Mountains the Laramie River flows in an east and northeast direction to join the North Platte River near Fort Laramie. Chugwater Creek originates near the west edge of the Laramie Mountains (north and east of Laramie) and flows in an east, northeast, and north direction to join the Laramie River near Wheatland. Horse Creek originates near the west edge of the Laramie Mountains (east of Laramie and south of the Chugwater Creek headwaters) and flows in a northeast, east-northeast, north, and northeast direction to join the North Platte River just east of the Wyoming-Nebraska border. Bear Creek is a northeast and east oriented Horse Creek tributary east of the Laramie Mountains. Lodgepole Creek originates just south of the Horse Creek headwaters and flows in an east, east-southeast, east-northeast, and east-southeast direction to the east edge of figure 1 and east of figure 1 turns to flow in a southeast direction to join the northeast oriented South Platte River. Goshen Hole is not labeled in figure 1, but is a large and deep east-facing escarpment-surrounded basin located east of the north oriented Chugwater Creek segment between the towns of Chugwater and Wheatland, Wyoming. The Goshen Hole basin extends eastward to the Wyoming-Nebraska border and the north and northeast oriented Horse Creek segments north of La Grange, Wyoming drain across the eastern end of the Goshen Hole basin floor. The Chugwater Creek-Horse Creek drainage divide area in the Goshen Hole region investigated in this essay is located east of the Laramie Mountains, north and west of Horse Creek, south and east of Chugwater Creek, and south of the Laramie and North Platte Rivers.

The Horse Creek, Chugwater Creek, Laramie River, and North Platte River drainage routes all developed during immense melt water floods from the western margin of a thick North American ice sheet. Floodwaters flowed from western Canada to and across Wyoming at a time when the Laramie Mountains and other mountain ranges were just beginning to emerge. The mountain ranges emerged as ice sheet crustal warping raised the mountain masses and the much of the Wyoming and Colorado region and as floodwaters deeply eroded regions surrounding the emerging mountain ranges. At first floodwaters flowed in giant complexes of diverging and converging flood flow channels in south directions across and along the crests of what are today high mountain ranges. As mountain ranges emerged floodwaters were channeled into deeper valleys and/or along the margins of the emerging mountain masses. In the case of the Laramie Mountains the deep southeast oriented North Platte River valley eroded headward to and then along the east and northeast flank of the emerging mountain mass. At the same time headward erosion of deep east and northeast oriented valleys from the actively eroding and deep North Platte River valley into and across the emerging Laramie Mountains captured south and southeast oriented flood flow channels in the Laramie Mountains and also west of the Laramie Mountains. These east and northeast oriented valleys eroded headward into the Laramie Mountains in sequence from south to north and from east to west. Headward erosion of the Lodgepole Creek valley from the actively eroding South Platte River valley captured floodwaters in the Laramie Mountains first. Flood flow to the newly eroded Lodgepole Creek valley was beheaded by headward erosion of the Horse Creek valley, which eroded headward from the deep east oriented Goshen Hole basin, which was eroding headward from the actively eroding southeast oriented North Platte River valley. Next headward erosion of the Chugwater Creek valley from the actively eroding Laramie River valley (which was eroding headward from the actively eroding southeast oriented North Platte River valley) captured east oriented flood flow to the actively eroding Goshen Hole basin headcut and also to the newly eroded Horse Creek valley. Headward erosion of the Laramie River valley across the Laramie Mountains also captured flood flow west of the Laramie Mountains. Floodwaters on the north ends of beheaded flood flow channels in the Laramie Basin (west of the Laramie Mountains) reversed flow direction to create the north oriented Laramie River drainage route south of Wheatland Reservoir. These flood flow captures and flood flow reversals were aided by uplift of the Laramie Mountains and of the entire region as floodwaters flowed across the region.

Detailed location map for Chugwater Creek-Horse Creek drainage divide area

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

Figure 2 provides a detailed location map for the Chugwater Creek-Horse Creek drainage divide area in the Wyoming and Nebraska Goshen Hole region. The north to south oriented dark dashed line near the east edge of figure 2 is the Wyoming-Nebraska border. Goshen and Platte are Wyoming county names and Scottsbluff is a Nebraska county name. The Laramie Mountains extend in a south direction from northwest corner of figure 2 to the south edge of figure 2 (west half). The east margin of the Laramie Basin is located west of the Laramie Mountains and is near the west edge of figure 2 (except in the northwest corner region). The North Platte River flows in a southeast direction from the north center edge of figure 2 to the east center edge of figure 2. The Laramie River flows in a north-northeast direction from the west edge of figure 2 (south of center) to just north of Wheatland Reservoir Number 2 and then turns to flow in an east and northeast direction across the Laramie Mountains before flowing in an east and northeast direction to join the North Platte River near Fort Laramie. Horse Creek originates near the west edge of the Laramie Mountains and just north of the south edge of figure 2 and then flows in an east-northeast direction into the southeast quadrant of figure 2 where Horse Creek then turns to flow in a north-northwest, north, east, and northeast direction to join the North Platte River near the Wyoming-Nebraska border. Bear Creek is an east-northeast oriented Horse Creek tributary originating east of the Laramie Mountains and joining Horse Creek in southern Goshen County. Little Bear Creek is an east-northeast oriented Bear Creek tributary and has east-northeast oriented tributaries. Chugwater Creek headwaters are located along the west edge of the Laramie Mountains (just north of the Horse Creek headwater) and flow in east directions across the Laramie Mountains to converge and then to flow in a northeast and north-northwest direction adjacent to the railroad line (which follows the Chugwater Creek valley) almost to the town of Wheatland where Chugwater Creek turns in a north-northeast direction to join the Laramie River. Goshen Hole is labeled in Goshen County and is bounded on the south by Diamond Flat and on the west by Slater Flats and Chugwater Flats. The Chugwater Creek and Horse Creek headwaters all begin near the west edge of the Laramie Mountains at an elevation that is today 300-400 meters higher than the elevation of the Laramie Basin floor just to the west. This situation is discussed in the Laramie River-Horse Creek drainage divide area in the Laramie Mountains essay. The Chugwater Creek-Goshen Hole drainage divide area essay focuses on the Chugwater Creek-Goshen Hole Rim region (especially the Slater Flats area), which is also addressed in this essay, but in less detail.

Sand Creek- Little Bear Creek drainage divide area

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

Figure 3 provides a topographic map of Sand Creek-Little Bear Creek drainage divide area. The map contour interval for figure 3 is 20 meters except near the east edge where the contour interval is 10 meters. Horse Creek flows in an east and east-northeast direction from the southwest corner of figure 3 to the east edge of figure 3 (south half). East of figure 3 Horse Creek flows in an east-northeast, north, east, and northeast direction to join the southeast oriented North Platte River. Horse Creek Hogback is the high ridge crossing the southwest corner of figure 3 and Horse Creek flows through a 200-meter deep water gap crossing Horse Creek Hogback. The southeast oriented stream just east of Horse Creek Hogback is North Fork Horse Creek. The northeast and north oriented stream flowing from the west edge of figure 3 (slightly south of center) to Farthing and the north edge of figure 3 (near northwest corner) is Sand Creek. North of figure 3 Sand Creek joins northeast and north oriented Chugwater Creek to flow to the east and northeast oriented Laramie River, which then flows to the southeast oriented North Platte River. Just east of Horse Creek Hogback is a north to south oriented through valley linking the north oriented Sand Creek valley with the southeast oriented North Fork Horse Creek valley. The through valley continues in a south direction and south of figure 3 is crossed by east oriented Lodgepole Creek and further south is drained by tributaries to Crow Creek, which flows to the northeast oriented South Platte River. The through valley floor elevation at Altus (a railroad siding on the drainage divide) is between 2040 and 2060 meters. Elevations on Horse Creek Hogback rise to more than 2200 meters while elevations on the ridge east of the through valley rise to more than 2160 meters. These elevations suggest the through valley is at least 100 meters deep. East oriented streams originating near the east wall of the through valley in the south half of figure 3 and flowing to the east edge of figure 3 include the South Fork and North Branch of Little Bear Creek, which east of figure 3 join to form northeast oriented Little Bear Creek, which then joins east oriented Bear Creek, which flows to north oriented Horse Creek. East and northeast oriented streams in the northeast quadrant of figure 4 are Bear Creek tributaries. The east-oriented Little Bear Creek tributary valleys originated as diverging and converging east oriented flood flow channels coming from the Laramie Mountains (west of figure 3) prior to headward erosion of the deeper north to south oriented through valley. The through valley was eroded headward as a south oriented valley probably from the actively eroding South Platte River valley and captured east oriented flood flow moving across the Laramie Mountains and also south oriented flood flow along the eastern margin of the emerging Laramie Mountains. Headward erosion of the east oriented Lodgepole Creek valley (from the South Platte River valley) then captured the south oriented flood flow and diverted floodwaters in an east direction. Headward erosion of the east-northeast oriented Horse Creek valley from the actively eroding North Platte River valley (actually from the actively eroding Goshen Hole valley) next captured the south oriented flood flow and diverted the floodwaters in an east-northeast direction. Next headward erosion of the east and northeast oriented Laramie River valley from the actively eroding North Platte River valley beheaded and reversed flood flow routes east of the Laramie Mountains, which enabled the deep Chugwater Creek valley to erode headward across east oriented flood flow to the actively eroding Goshen Hole valley and also to behead the south oriented flood flow channel in the through valley. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to flow to the deeper northeast and north oriented Chugwater Creek valley and to create the north oriented Sand Creek drainage route.

Detailed map of Sand Creek-Little Bear Creek drainage divide area

Figure 4: Detailed map of Sand Creek-Little Bear Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 provides a detailed topographic map of the Sand Creek-Little Bear Creek drainage divide area seen in less detail in figure 3. The map contour interval for figure 4 is 20 feet. Horse Creek Hogback extends in a south-southeast direction across the southwest corner of figure 4. Sand Creek originates near the west center edge of figure 4 (near north end of Horse Creek Hogback) and flows in an east, northeast, and north direction to the north edge of figure 4 (west half-the railroad is located in the Sand Creek valley). North of figure 4 Sand Creek flows to northeast and north oriented Chugwater Creek, which then flows to the east and northeast oriented Laramie River, which then flows to the southeast oriented North Platte River. North Fork Horse Creek flows from the west edge of figure 4 (south half) through a deep water gap eroded across Horse Creek Hogback (in section 9) to McLaughlin Reservoir number 2 and then meanders in a southeast direction to the south edge of figure 4 (west half). South of figure 4 North Fork Horse Creek joins east-northeast, north, and northeast oriented Horse Creek to flow to the southeast oriented North Platte River. A deep north to south oriented through valley links the north oriented Sand Creek valley with the southeast oriented North Fork Horse Creek valley. The through valley floor elevation at Altus is 6722 feet. Horse Creek Hogback elevations rise to 7375 feet and elevations at the corner of sections 7, 12, 13, and 18 on the east side of the through valley rise to at least 7141 feet. These elevations suggest the north to south oriented through valley is at least 400 feet deep. A different set of truncated through valleys links the north to south oriented through valley with the east and east-northeast oriented stream valleys draining to the east edge of figure 4. These east and east-northeast oriented streams are headwaters of northeast oriented Little Bear Creek, which flows to east oriented Bear Creek, which then flows to north oriented Horse Creek. For example, the North Branch Little Bear Creek originates in section 6 and flows in an east-northeast direction to the east edge of figure 4 (north of center). A truncated west to east oriented through valley in section 6 links the east-northeast oriented North Branch Little Bear Creek valley with a southwest oriented North Fork Horse Creek tributary valley. The through valley floor elevation is between 6920 and 6940 feet. Elevations in section 36 to the north rise to more than 7060 feet and in section 7 to the south elevations rise to more than 7080 feet. These elevations suggest the truncated west to east oriented through valley is at least 120 feet deep. The west to east oriented through valley was eroded by an east oriented flood flow channel prior to headward erosion of the deeper north to south oriented through valley. What this sequence of valley formation suggests in that east oriented flood flow was captured by headward erosion of a south oriented flood flow channel, which was subsequently beheaded and reversed by headward erosion of an even deeper east oriented flood flow channel further to the north.

Chugwater Creek-North Bear Creek drainage divide area

Figure 5: Chugwater Creek-North Bear Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Chugwater Creek-North Bear Creek drainage divide area north of figure 3 and includes an overlap area with figure 3. The map contour interval for figure 5 is 20 meters. Farthing is located near the southwest corner of figure 5. Chugwater Creek flows in a northeast direction from the west edge of figure 5 (just north of Farthing) to the north edge of figure 5 (near northeast corner). North and east of figure 5 Chugwater Creek turns to flow in a north direction to join the east and northeast oriented Laramie River, which then joins the southeast oriented North Platte River. Sand Creek flows from the south edge of figure 5 (near southwest corner) to join Chugwater Creek north of Farthing. The Laramie Mountains are located west of figure 5 and east oriented tributaries flow from the Laramie Mountains to join northeast oriented Chugwater Creek. North Bear Creek originates near the south center edge of figure 5 and flows in a northeast and east direction to the east edge of figure 5 (south half). East of figure 5 North Bear Creek flows in an east-northeast direction to east oriented Bear Creek, which eventually joins north oriented Horse Creek, which then flows to the southeast oriented North Platte River. Spring Creek is located north of North Bear Creek and originates on the southeast side of the Chugwater Creek valley and then flows in an east, northeast, and north-northeast direction to join Chugwater Creek near the railroad siding of Diamond (near northeast corner of figure 5). Spring Creek headwaters valleys are truncated by the deeper northeast oriented Chugwater Creek valley, which suggests Spring Creek originated as an east oriented flood flow channel probably converging with flood flow channels eroding the east oriented Bear Creek valley east of figure 5. Headward erosion of the deep east and northeast oriented Laramie River valley from the actively eroding southeast oriented North Platte River valley north of figure 5 enabled the deep northeast and north oriented Chugwater Creek valley to erode headward into the region and the north-northeast oriented Spring Creek valley eroded headward from the actively eroding Chugwater Creek valley head to capture east oriented flood flow on the east oriented Spring Creek alignment. Headward erosion of deep northeast oriented Chugwater Creek valley then captured the east oriented Spring Creek flood flow channel, which beheaded the east oriented flood flow channel leading to the newly eroded north-northeast oriented Spring Creek valley. Next headward erosion of the deep northeast oriented Chugwater Creek valley beheaded south oriented flood flow to the east-northeast and north oriented Horse Creek valley flowing on the present day north oriented Sand Creek alignment. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to flow to the deeper northeast and north oriented Chugwater Creek valley and to create the north oriented Sand Creek drainage route.

Detailed map of Chugwater Creek-North Bear Creek drainage divide area

Figure 6: Detailed map of Chugwater Creek-North Bear Creek 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 Chugwater Creek-North Bear Creek drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 20 feet. Chugwater Creek joins north-northeast oriented Sand Creek in the northwest corner of figure 6 and then flows in a northeast direction to the north edge of figure 6. North of figure 6 Chugwater Creek flows in a northeast direction and then north direction to join the east and northeast oriented Laramie River, which then flows to the southeast oriented North Platte River. The Chugwater Creek valley floor elevation in the northwest corner of figure 6 is between 6200 and 6220 feet. Elevations on the Chugwater Creek valley rim in section 6 exceed 6900 feet suggesting the Chugwater Creek and Sand Creek valleys are almost 700 feet deep. North Bear Creek originates along the Sand Creek valley rim in section 18 and then flows in an east-northeast and northeast direction to the east center edge of figure 6. East of figure 6 North Bear Creek flows to east oriented Bear Creek, which eventually joins north and northeast oriented Horse Creek, which then flows to the southeast oriented North Platte River. East oriented streams originating on the Sand Creek valley rim in the south half of figure 6 flow to North Bear Creek, while east and northeast oriented streams originating on the valley rim in the north half of figure 6 flow to northeast and north-northeast oriented Spring Creek, which joins northeast and north oriented Chugwater Creek north and east of figure 6. Study of the Sand-Chugwater Creek valley rim reveals through valleys linking west oriented Sand Creek tributary valleys with east oriented North Bear Creek and Spring Creek headwaters valleys. For example near the southeast corner of section 7 a west to east oriented through valley links a west oriented Sand Creek tributary valley with an east oriented North Bear Creek tributary valley. The through valley floor elevation at the valley rim is between 6760 and 6780 feet. Elevations in section 6 to the north rise to more than 6900 feet. Elevations in section 18 to the south also rise to more than 6900 feet suggesting the through valley is at least 120 feet deep. This 120-foot deep truncated east oriented valley was eroded by east oriented flood flow prior to headward erosion of a deep south oriented valley on the present day north oriented Sand Creek alignment. Headward erosion of the south oriented valley captured diverging and converging east oriented flood flow channels and diverted the floodwaters in a south direction along the east side of what were then the emerging Laramie Mountains. The short west oriented Sand Creek tributary drainage route was created by a flood flow reversal on the west end of the beheaded east oriented flood flow channel. Headward erosion of the deep northeast oriented Chugwater Creek valley then captured east flood flow channels leading to the newly eroded south oriented flood flow channel on the Sand Creek alignment (one of these captured east oriented flood flow channels is today Middle Chugwater Creek, which originates near the west edge of the Laramie Mountains). Floodwaters on the north end of the beheaded flood flow channel (on the Sand Creek alignment) reversed flow direction to flow to the deeper northeast oriented Chugwater Creek valley and to create the north oriented Sand Creek drainage route.

Chugwater Creek-Horse Creek drainage divide area

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

Figure 7 uses a reduced size topographic map to illustrate the Chugwater Creek-Horse Creek drainage divide area north and east of figure 5 and there is no overlap area with figure 5. The map contour interval for figure 7 is 10 meters. The North Platte River flows in a southeast direction across the northeast corner of figure 7. Chugwater Creek flows in a north direction from the southwest corner of figure 7 to the west center edge of figure 7 and west and north of figure 7 flows in a north direction to the east and northeast oriented Laramie River, which then flows to the southeast oriented North Platte River. Horse Creek flows in a north and northeast direction across the southeast corner of figure 7 and east of figure 7 flows in a southeast and northeast direction to join the southeast oriented North Platte River. Goshen Hole is the large east-facing escarpment-surrounded basin bounded on the west by Slater Flats, which are the upland region between the north oriented Chugwater Creek valley and the east-facing Goshen Hole escarpment. Horse Creek crosses the 1300-meter contour line near the southeast corner of figure 7. Elevations on Slater Flats are generally in the 1550 to 1600 meter range (there is a slight decrease in elevations in a north direction). The Goshen Hole basin floor is approximately 250 meters lower in elevation than the Slater Flats upland surface elevation. Chugwater Creek crosses the 1500-meter contour line near the southwest corner of figure 7 suggesting the Chugwater Creek valley is approximately 100 meters deep and 100 to 150 meters higher than the Goshen Hole basin floor. The Goshen Hole escarpment-surrounded basin is a giant abandoned headcut, which was eroded by large volumes of east oriented floodwaters flowing across the present day Laramie Mountains (west of figure 7). Several deep valleys cross the Laramie Mountains, some of which are illustrated in the Laramie River-Sybille Creek and the North Laramie River-Laramie River essays). At the time east oriented flood flow moved from the Laramie Mountains to the actively eroding Goshen Hole headcut face and then into Goshen Hole the north oriented Chugwater Creek valley did not exist.  The east oriented Goshen Hole headcut eroded headward from the actively eroding North Platte River valley head and encountered a zone of erosion resistant bedrock in the Slater Flats area that did not exist to the north of Slater Flats (and north of figure 6). Had the actively eroding Goshen Hole headcut not encountered the erosion resistant bedrock the Laramie River would today flow through Goshen Hole and not flow to the north of figure 6. However, the actively eroding Goshen Hole valley rate of headward erosion was greatly slowed by the erosion resistant bedrock underlying Slater Flats and north of figure 7 the east and northeast oriented Laramie River valley was able to erode headward from the actively eroding southeast oriented North Platte River valley. The north oriented Chugwater Creek valley then eroded headward from the actively eroding Laramie River valley along the western margin of the Slater Flats erosion resistant material to capture the east oriented floodwaters moving to and across Slater Flats and then to Goshen Hole. Headward erosion of the north oriented Chugwater Creek valley ended all east oriented flood flow across Slater Flats. The north oriented Horse Creek drainage route in the southeast corner of figure 7 was created in a similar manner and the north oriented Horse Creek valley eroded headward to capture east oriented flood flow south of the newly eroded and deep east oriented Goshen Hole valley.

Chugwater Creek-Box Elder Creek drainage divide area

Figure 8: Chugwater Creek-Box Elder 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 Chugwater Creek-Box Elder Creek drainage divide area south and west of figure 7 and includes an overlap area with figure 7. The map contour interval for figure 8 is 10 meters. Chugwater Creek flows in a northeast and north direction from the southwest corner of figure 8 to the north edge of figure 8 (west half-north of the town of Slater). The escarpment rim extending in a southeast and south-southeast direction across the northeast corner of figure 8 is the Goshen Hole Rim. Slater Flats is the upland region between the Chugwater Creek valley and the Goshen Hole Rim in the north half of figure 8. Iowa Center Flats is located south and west of the Goshen Hole Rim in the southeast quadrant of figure 8 and Chugwater Flats is located south of Slater Flats in the southwest quadrant of figure 8. The northeast oriented stream flowing from the north end of Chugwater Flats across the Goshen Hole Rim in a deep canyon and then to the east edge of figure 8 (near northeast corner) is Box Elder Creek. The Box Elder Creek alignment is approximately the same as the northeast oriented Chugwater Creek alignment upstream from the town of Chugwater. The deep northeast oriented Box Elder Creek canyon suggests northeast oriented flood flow crossed the Goshen Hole Rim at this location and was at least to some degree independent of the east oriented flood flow eroding the Goshen Hole valley headward further to the north. The northeast oriented Chugwater Creek valley upstream from the town of Chugwater was probably initiated as a northeast oriented valley draining into the newly eroded and deep Goshen Hole valley or basin along the Box Elder Creek alignment. Headward erosion of that northeast oriented Chugwater-Box Elder Creek valley captured east oriented flood flow from the Laramie Mountains and diverted those floodwaters into newly eroded and deep Goshen Hole, although that early northeast oriented valley floor was at least as high as the present day Chugwater Creek-Box Elder Creek drainage divide elevation today. When the deeper north oriented Chugwater Creek valley eroded headward along the west margin of the erosion resistant bedrock material underlying the Slater Flats area it captured the northeast oriented flood flow that had been moving to the actively eroding Box Elder Creek canyon and diverted the floodwaters in a north direction to the newly eroded east and northeast oriented Laramie River valley. An interesting comparison on both sides of Slater Flats can be made in figure 8 of the Slater Flats cap rock thickness near the north edge of figure 8. On the Goshen Hole side the steep cliff face is more than 100 meters high while on the Chugwater Creek side the steep cliff face is about 50 meters high and is even thinner on the west side of the Chugwater Creek valley. This difference in the cap rock thickness probably explains why the north oriented Chugwater Creek valley was able to erode headward along the east margin of Slater Flats to capture large volumes of east oriented flood flow that had been flowing into the much deeper Goshen Hole basin just to the east.

Iowa Center Flats-Horse Creek drainage divide area

Figure 9: Iowa Center Flats-Horse Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates a reduced size topographic map of the Iowa Center Flats-Horse Creek drainage divide area south and east of figure 7 and there is an overlap area with figure 7. The map contour interval for figure 9 is 10 meters. The northeast-facing escarpment extending in a southeast direction from the northwest corner of figure 9 is the southwest wall of the Goshen Hole basin or valley. Iowa Center Flats are located between the west edge of figure 9 and the Goshen Hole Rim. The northeast oriented Box Elder Creek canyon can be seen in the northwest corner of figure 9.  La Grange is a small town near the southeast corner of figure 9 and Hawk Springs is the small town located east of the center of figure 9. Horse Creek flows in a north-northwest direction from the south edge of figure 9 (south of La Grange) to Hawk Springs and then in a north direction to the north edge of figure 9 (east half). North of figure 9 Horse Creek turns to flow in a northeast, southeast, and northeast direction to join the southeast oriented North Platte River. Sixtysix Mountain is large butte located north of La Grange on the east side of the north oriented Horse Creek valley. Bear Mountain is the butte located on the west side of the Horse Creek valley at the southeast end of the Goshen Hole Rim and Castle Rocks is the name for the butte immediately to the northwest of Bear Mountain. Bear Creek is the east and east-northeast oriented stream flowing from the southwest corner of figure 9 to Bear Mountain and then flowing in a southeast and north direction around the Bear Mountain southeast end before joining Horse Creek north of La Grange. Fox Creek is an east-southeast oriented tributary flowing from Iowa Center Flats to join Bear Creek on the south side of Bear Mountain. The east and east-northeast oriented Bear Creek and east-southeast oriented Fox Creek valleys provide evidence the north oriented Horse Creek valley captured east oriented flood flow from west of figure 9. As seen in figure 2 the northeast oriented Chugwater Creek valley is today located west of figure 9 so at the time the Bear Creek and Fox Creek valleys were eroded the northeast oriented Chugwater Creek valley did not exist. Headward erosion of the northeast oriented Chugwater Creek valley ended east oriented flood flow to the Bear Creek and Fox Creek valleys and as seen in figure 8 for a short time flood flow was diverted to the northeast oriented Box Elder Creek alignment, but was subsequently diverted in a north direction to the newly eroded and deeper Laramie River valley. Sixtysix Mountain is an erosional residual standing approximately 200 meters above the surrounding Goshen Hole surface and provides evidence that floodwaters removed at least 200 meters of bedrock material from the Goshen Hole basin region.

Detailed map of Fox Creek-Horse Creek drainage divide area

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

Figure 10 provides a reduced size topographic map of the Fox Creek-Horse Creek drainage divide located south of figure 9 and includes an overlap area with figure 9, although figure 10 has not been reduced as much as figure 9 was reduced. The map contour interval for figure 10 is 10 meters. The north to south oriented Wyoming-Nebraska state line is located near the east edge of figure 10. La Grange is the town located in the northeast quadrant of figure 10. Meriden is a smaller town located in the southwest quadrant of figure 10. Horse Creek flows in an east-northeast and southeast direction from the west edge of figure 10 (south of center) to Meriden and then in a southeast, east-northeast, and north direction to La Grange. Horse Creek flows in a north-northwest direction from La Grange to the north edge of figure 10 (east of center). Bear Creek flows in an east direction from the northwest corner of figure 10 along the north edge of figure 10 and south of Bear Mountain turns to flow in a southeast and north direction to the north center edge of figure 10 and then to join north oriented Horse Creek north of figure 10. Fourmile Draw is an east-oriented drainage route near the center of figure 10 and drains to north oriented Horse Creek. The north oriented Horse Creek valley eroded from the newly eroded Goshen Hole valley to capture east oriented flood flow route south of the Goshen Hole valley. Escarpments surrounding the Horse Creek elbow of capture (where Horse Creek turns to flow in a north direction) are approximately 200 meters high and provide more evidence of the deep erosion caused by east and north oriented floodwaters flowing along the Horse Creek alignment. The east oriented Fourmile Draw valley was eroded by east oriented flood flow moving into the deep north oriented Horse Creek valley, although headward erosion of the northeast oriented Dater Creek valley from the Bear Creek valley captured the east oriented flood flow and beheaded the Fourmile Draw flood flow channel. As seen in figures 3, 4, 5, and 6 east oriented floodwater from the Laramie Mountains cross what is now the deep north and northeast oriented Sand Creek-Chugwater Creek valley to flow to the east, east-northeast, and northeast oriented Little Bear Creek and Bear Creek headwaters (Little Bear Creek joins Bear Creek west of figure 10) and then to flow to the north oriented Horse Creek valley as seen here. Floodwaters that eroded the region seen in figure 10 came from the Laramie Mountains and probably from west of the Laramie Mountains at a time when the Laramie Mountains did not stand high above the Laramie Basin (on west side of the Laramie Mountains) as they do today (see Laramie River-Horse Creek essay).

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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