Abstract:

This essay uses topographic map evidence to interpret landform origins in the La Prele Creek-North Platte River drainage divide area in the Wyoming Laramie Mountains. The North Platte River flows in a north, northeast, east, and southeast direction around the north and northwest end of the Laramie Mountains. La Prele Creek is a north-northeast oriented stream originating on the southwest side of the Laramie Mountains and flowing in a deep valley across the Laramie Mountains to join the east oriented North Platte River just before it turns to flow in  southeast direction on the east side of the Laramie Mountains. La Bonte Creek is a north, east-northeast, and north-northeast stream flowing in deep valleys across the Laramie Mountains to join the southeast oriented North Platte River as a barbed tributary. Through valleys link the La Prele Creek, La Bonte Creek, and other north and northeast oriented North Platte River tributary valleys with each other and with southwest and west oriented valleys draining to the north oriented North Platte River located west of the Laramie Mountains. Through valleys, barbed tributaries, valleys orientations, elbows of capture, deep water gaps, and other similar evidence are interpreted in the context of immense melt water floods from the western margin of a thick North American ice sheet. Floodwaters flowed from western Canada across Montana and then to and across Wyoming at a time when the Laramie Mountains were beginning to emerge. At first floodwaters were able to flow across the emerging Laramie Mountains and created south and southwest oriented drainage routes. The Laramie Mountains emerged as ice sheet related crustal warping raised the mountains and as floodwaters deeply eroded surrounding regions. Deeper and deeper south and southwest oriented valleys were eroded as the Laramie Mountains emerged until headward erosion of the much deeper southeast oriented North Platte River valley on the east side of the Laramie Mountains systematically beheaded the south and southwest oriented flood flow channels in sequence from east to west. Floodwaters on north and north-northeast ends of the beheaded flood flow channels reversed flow direction to flow to the much deeper southeast oriented North Platte River. The reversed flood flow also captured floodwaters still moving in a south direction west of the Laramie Mountains and the captured floodwaters then moved in east, northeast, and north-northeast directions across the Laramie Mountains in the newly reversed flood flow channels. Headward erosion of the deep North Platte River valley around the northwest end of the Laramie Mountains then in a series of steps beheaded and reversed south oriented flood flow channels west of the Laramie Mountains to create the north oriented North Platte River drainage route west of the Laramie Mountains and to end east and north-northeast oriented flood flow across the Laramie Mountains.

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 La Prele Creek-North Platte River drainage divide area landform origins in the Wyoming Laramie Mountains. 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 La Prele Creek-North Platte River drainage divide area landform evidence in the Wyoming Laramie Mountains will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

La Prele Creek-North Platte River drainage divide area location map

Figure 1: La Prele Creek-North Platte 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 La Prele Creek-North Platte River drainage divide area in the Wyoming Laramie Mountains and illustrates a region in east-central Wyoming. The Laramie Mountains extend in a southeast and south direction from south of Casper to the south center edge of figure 1. The North Platte River flows in a north, north-northeast, northeast, east, south, east, and southeast direction from the southwest corner of figure 1 around the northwest end of the Laramie Mountains to the east edge of figure 1 (south half). East of figure 1 the North Platte River flows into Nebraska. Box Elder Creek is a labeled north-northeast oriented North Platte River tributary flowing across the Laramie Mountains near the center of figure 1. La Prele Creek is the unlabeled north-northeast oriented North Platte River tributary located east of Box Elder Creek. South and east of La Prele Creek the unlabeled east, north, and east oriented North Platte River tributary is Wagon Hound Creek, which joins the southeast oriented North Platte River south of Douglas.  Also joining the North Platte River south of Douglas is La Bonte Creek, which is another unlabeled north-northeast oriented North Platte River tributary. Horseshoe Creek is the labeled northeast oriented North Platte River tributary south of La Bonte Creek. The North Laramie River flows in a south, east-northeast, and east direction south of Horseshoe Creek to join the northeast and east-northeast oriented Laramie River, which joins the southeast oriented North Platte River near the east edge of figure 1. West of the North Laramie River headwaters is south and southwest oriented Sheep Creek, which flows to the south oriented Little Medicine Bow River. South of figure 1 the Little Medicine Bow River turns to flow in a west direction to join the northwest, west, and northwest oriented Medicine Bow River, which then flows to the north oriented North Platte River at Seminoe Reservoir (in southwest corner of figure 1). The La Prele Creek-North Platte River drainage divide area investigated in this essay emphasizes the region east of La Prele Creek and south and west of the southeast oriented North Platte River.

The North Platte River drainage system on both sides of the Laramie Mountains developed during immense melt water floods from the western margin of a thick North American ice sheet. Floodwaters flowed from western Canada across Montana to and across Wyoming at a time when Wyoming mountain ranges were beginning to emerge. Mountain ranges, including the Laramie Mountains, emerged as floodwaters flowed across them and as floodwaters deeply eroded surrounding valleys and basins and as ice sheet related crustal warping raised the mountain ranges and the entire region (especially regions south and west of figure 1). The north oriented North Platte River drainage route west of the Laramie Mountains and north oriented North Platte River tributary drainage routes crossing the Laramie Mountains originated as south oriented flood flow channels. Headward erosion of a deep southeast oriented North Platte River valley captured south oriented floodwaters east of the emerging Laramie Mountains while the east-northeast and northeast oriented Laramie River valley and tributary valleys eroded headward across the emerging Laramie Mountains to capture south oriented flood flow west of the actively eroding North Platte River valley head. Some of the flood flow moving in south directions west of Laramie Mountains was captured by headward erosion of the deep northeast and east-northeast oriented Laramie River valley and tributary valleys and was then diverted in southeast and east directions on the southwest side of the Laramie Mountains (on the alignment of present day streams such as northwest oriented Bates Creek and the northwest, west, and northwest oriented Medicine Bow River, among others) before flowing in east and northeast directions across the Laramie Mountains to the much deeper southeast oriented North Platte River valley.

Headward erosion of the deep North Platte River valley around the emerging Laramie Mountains beheaded the south oriented flood flow channels crossing the Laramie Mountains in sequence from east to west. Floodwaters on north ends of the beheaded flood flow channels reversed flow direction to flow to the much deeper southeast oriented North Platte River valley and to create what are today north oriented North Platte River tributary drainage routes, which originate on the southwest side of the Laramie Mountains. The reversal of flood flow on these former south oriented flood flow channels captured southeast oriented flood flow moving along the southwest side of the emerging Laramie Mountains and diverted the captured floodwaters in north directions across the Laramie Mountains to the newly eroded and deep southeast oriented North Platte River valley. Eventually the deep North Platte River eroded headward around the northwest end of the emerging Laramie Mountains and began to behead south oriented flood flow channels west of the Laramie Mountains. Floodwaters on north ends of beheaded flood flow channels reversed flow direction to flow to the much deeper North Platte River valley. The present day north oriented North Platte River drainage route west of the Laramie Mountains was created by a series of such beheading of flood flow channels and their resulting flood flow reversals. The reversals of flood flow west of the Laramie Mountains also reversed flood flow on flood flow routes on the southwest side of the Laramie Mountains to create the present day northwest oriented Bates Creek and northwest, west, and northwest oriented Medicine Bow River drainage routes (among others) and ended flood flow to deep valleys crossing the Laramie Mountains such as the Laramie River, North Laramie River, and tributary valleys and the north-northeast oriented Horseshoe Creek, La Bonte Creek, La Prele Creek,  and Box Elder Creek valleys.

Detailed location map for La Prele Creek-North Platte River drainage divide area

Figure 2: Detailed location map La Prele Creek-North Platte River 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 La Prele Creek-North Platte River drainage divide area in the Wyoming Laramie Mountains. The North Platte River flows in an east, south, east, and southeast direction from the northwest corner of figure 2 to the east edge of figure 2 (south half) and east of figure 2 continues in a southeast direction into Nebraska. La Prele Creek originates near the southwest corner of figure 2 and flows in a north-northeast direction to join the east oriented North Platte River just before the North Platte River turns to flow in a south direction. Rabbit Creek is a north oriented La Prele Creek tributary in the southwest quadrant of figure 2. Little La Prele Creek is a north and northwest oriented La Prele Creek tributary located east and north of Rabbit Creek. [The south end of Little La Prele Creek shown in figure 2 should be shown as the headwaters of Wagon Hound Creek and does not drain to Little La Prele Creek.] Sheep Mountain is a labeled mountain near the center of figure 2. Bed Tick Creek and Little Bed Tick Creek are east and southeast oriented North Platte River tributaries north of Sheep Mountain. Wagon Hound Creek flows in a northeast and east direction to join the North Platte River south of Sheep Mountain. Corral Creek is a northeast oriented Wagon Hound Creek tributary. Manning Ridge is a labeled landform south of Sheep Mountain. La Bonte Creek flows in an east-northeast and north-northeast direction in the region south and east of Manning Ridge and the West Fork La Bonte Creek drains the region west and north of Manning Ridge. Horseshoe Creek flows in a east-northeast direction from the south edge of figure 2 (east half-east of Esterbrook) to join the North Platte River just east of the east edge of figure 2 (near southeast corner). North and north-northeast oriented drainage routes in figure 2 probably oriented as south and south-southwest oriented flood flow channels and were beheaded by headward erosion of the much deeper North Platte River valley and/or by headward erosion of much deeper east and northeast oriented North Platte River tributary valleys. Floodwaters on north ends of the beheaded flood flow channels reversed flow direction to flow to the much deeper beheading valley and to create north oriented drainage routes. In addition the reversed flood flow often captured flood flow still moving in south and southeast directions west of the actively eroding beheading valley head.

La Prele Creek-Wagon Hound Creek drainage divide area

Figure 3: La Prele Creek-Wagon Hound Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of La Prele Creek-Wagon Hound Creek drainage divide area. The map contour interval for figure 3 is 20 meters. The North Platte River flows in an east direction north of figure 3 and north of the northeast corner of figure 3 turns to flow in a south direction to flow in a south direction along the east edge of figure 3 before flowing to the east edge of figure 3 (slightly north of center). La Bonte Creek flows in a north-northeast direction across the southeast corner of figure 3 and joins the North Platte River east of figure 3. Rattlesnake Hill is located near the center of figure 3 and Sheep Mountain is located north and east of Rattlesnake Hill. Wagon Hound Creek flows in an east-northeast and north direction from the south edge of figure 3 (west half-near east edge of forested area) to a deep water gap east of Rattlesnake Hill and then turns to flow in a southeast direction along the southwest side of Sheep Mountain before turning to flow to the east center edge of figure 3 and to join the North Platte River east of figure 3. The La Prele Creek-Wagon Hound Creek drainage divide is a well-defined north-northeast oriented ridge with Tomahawk Peak being a labeled high point on the ridge. West of the ridge La Prele Creek tributaries are generally oriented in northwest directions while east of the ridge Wagon Hound Creek tributaries are generally oriented in southeast and east directions and include Sheep Creek, Krazer Creek, and King Creek. Study of the drainage divide ridge reveals northwest to southeast oriented through valleys linking the northwest oriented La Prele Creek tributary valleys with the southeast and east oriented Wagon Hound Creek tributary valleys. Based on adjacent high points these through valleys range in depth with the deepest through valleys being approximately 80 meters deep. The through valleys were eroded by southeast oriented flood flow probably moving along the northeast flank of the emerging Laramie Mountains to reach what was at that time the actively eroding southeast oriented North Platte River valley head (which at that time was probably located south and east of figure 3). Headward erosion of the deeper Wagon Hound Creek valley captured the southeast oriented flood flow and diverted the floodwaters to the actively eroding North Platte River valley. The southeast oriented flood flow eroded southeast oriented valleys that beheaded and reversed earlier south-southwest oriented south oriented flood flow channels crossing the Laramie Mountains. Headward erosion of the deep east oriented North Platte River valley north of figure 3 resulted in headward erosion of a deeper north-northeast oriented La Prele Creek valley, which beheaded and reversed the southeast oriented flood flow to create the northwest oriented La Prele Creek tributary drainage routes and to create the La Prele Creek-Wagon Hound Creek drainage divide. Flood flow movements in this region were complex and kept changing as deeper and deeper valleys eroded headward into the region. Erosion destroyed considerable evidence although my description here leaves out many details that can be determined from remaining evidence, but hopefully provides enough information to guide interested researchers in deciphering those additional details.

Detailed map of La Prele Creek-King Creek drainage divide area

Figure 4: Detailed map of La Prele Creek-King 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 La Prele Creek-King Creek drainage divide area seen in less detail in figure 3. The map contour interval for figure 4 is 20 feet. La Prele Creek flows in a north direction along the north half of the west edge of figure 4. Labeled northwest oriented La Prele Creek tributaries in figure 4 (from north to south) include Semino Creek, Hart Draw and its Cross Draw tributary, and Sand Creek. Tomahawk Peak is located near the northeast corner of figure 4. Southeast and east oriented streams south of Tomahawk Peak are tributaries to north, southeast, and east oriented Wagon Hound Creek, with the labeled North and Middle Forks being tributaries to King Creek, which flows in an east direction to north oriented Wagon Hound Creek. A broad northwest to southeast oriented through valley extending from the northeast corner of section 16 to the center of section 20 links northwest oriented La Prele Creek tributary valleys with the southeast North Fork King Creek valley. The through valley floor elevation at its deepest point is between 5920 and 5940 feet. Elevations in the northwest corner of section 15 to the northeast rise to 6313 feet and elevations on the La Prele Creek-Wagon Hound Creek drainage divide south of figure 4 rise to much higher elevations as the Laramie Mountains are approached. These elevations suggest the through valley is at least 373 feet deep. The through valley was eroded by southeast oriented flood flow moving along the northeast flank of the Laramie Mountains prior to headward erosion of the much deeper North Platte River valley to the east and north of figure 4. The southeast oriented flood flow probably eroded a deep southeast oriented flood flow channel that had beheaded and reversed south and south-southwest oriented flood flow channels crossing the Laramie Mountains. The southeast oriented flood flow channel was then dismembered as north, northeast, and east oriented valleys eroded headward from the actively eroding North Platte River valley to capture the southeast oriented flood flow and to divert the captured floodwaters to the much deeper North Platte River valley.

Little La Prele Creek-Wagon Hound Creek drainage divide area

Figure 5: Little La Prele Creek-Wagon Hound Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Little La Prele Creek-Wagon Hound Creek drainage divide area south and west of figure 3 and there is an overlap area with figure 3. The map contour interval for figure 5 is 20 meters. La Prele Creek flows in a north-northeast direction from the southwest corner of figure 5 to the north center edge of figure 5. North of figure 5 La Prele Creek flows in a north-northeast direction to join the east oriented North Platte River just before it turns to flow in a south direction. Little La Prele Creek originates near the center of figure 5 and flows in a north and northwest direction to join north-northeast oriented La Prele Creek. Rabbit Creek flows in north and northwest direction from the south edge of figure 5 (west of center) to join north-northeast oriented La Prele Creek. Wagon Hound Creek originates near the south center edge of figure 5 and flows in a north direction along the west side of a high north to south oriented ridge before turning to flow across the ridge in north-northeast oriented Wagon Hound Gorge and then in a northeast and east direction to the east edge of figure 5 (north half). East of figure 5 Wagon Hound Creek turns to flow in a north, southeast, and east direction to join the east and southeast oriented North Platte River. Wagon Hound Gorge is a water gap and is approximately 200 meters deep. Several passes labeled in figure 5 identify north-northeast oriented wind gaps crossing the same north to south oriented mountain ridge. These passes include Virden Pass (north of Wagon Hound Gorge), Redenbaugh Pass (south of Wagon Hound Gorge), and Latham Pass (still further to the south). These passes link north-northeast oriented Wagon Hound Creek tributary valleys with the north oriented Wagon Hound Creek headwaters valley. The north oriented Wagon Hound Creek headwaters is located west of the high north to south oriented mountain ridge in a deep north to south oriented through valley drained on the west side by La Prele Creek and Rabbit Creek and north of where Wagon Hound Creek turns to flow through Wagon Hound Gorge by the north oriented headwaters of Little La Prele Creek. Depending on where it is measured this large north to south oriented through valley is as much as 200 meters deep and was eroded as a south oriented flood flow channel prior to the flood flow reversals that created the present day north oriented La Prele Creek and Wagon Hound Creek drainage routes. Wagon Hound Gorge, Virden Pass, Redenbaugh Pass, and Latham Pass were probably initiated as diverging and converging south-southwest oriented flood flow channels prior to the reversals of flood flow that created the north oriented Wagon Hound Creek drainage route.

Detailed map of Little La Prele Creek-Wagon Hound Creek drainage divide area

Figure 6: Detailed map of Little La Prele Creek-Wagon Hound 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 Little La Prele Creek-Wagon Hound Creek drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 20 feet. Wagon Hound Creek flows in a north, north-northeast, and northeast direction from the south center edge of figure 6 through Wagon Hound Gorge to the east edge of figure 6 (near Wagon Hound Falls). East and north of figure 6 Wagon Hound Creek flows in a northeast, east, northeast, north, southeast, and east direction to join the east and southeast oriented North Platte River. Wagon Hound Gorge is more than 600 feet deep in section 25 and is a deep water gap. To the north Virden Pass is a northeast to southwest oriented wind gap eroded across the same ridge and is at least 200 feet deep. The north oriented stream located near the west edge of figure 6 is Blue Nose Creek, which north of figure 6 flows to north-northeast La Prele Creek, which then flows in a north-northeast direction to join the east oriented North Platte River just before it turns to flow in a south, east, and southeast direction. The north oriented stream in section 23 flowing to the north center edge of figure 6 is Little La Prele Creek, which north of figure 6 turns to flow in a northwest direction to join north-northeast oriented La Prele Creek. A north to south oriented through valley near the center of section 26 links the north oriented Little La Prele Creek valley with the north and north-northeast oriented Wagon Hound Creek valley. The through valley floor elevation is between 7120 and 7140 feet. Elevations to the east of the through valley (on northwest side of Wagon Hound Gorge) rise to more than 7600 feet while west of figure 6 and west of the north-northeast oriented La Prele Creek drainage routes elevations in the Laramie Mountains rise much higher. In other words the through valley is simply a deeper channel in what was once a 500-foot deep south-oriented flood flow channel. The north-northeast oriented Wagon Hound Gorge water gap and the Virden Pass wind gap were probably initially eroded by south-southwest oriented flood flow that converged with the south oriented flood flow in the large south oriented flood flow channel. Headward erosion of the deep southeast oriented flood channel seen in figures 3 and 4 beheaded and reversed the south oriented flood flow routes across figure 6 to create the present day north oriented drainage routes.

West Fork La Bonte Creek-La Bonte Creek drainage divide area

Figure 7: West Fork La Bonte Creek-La Bonte Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the West Fork La Bonte Creek-La Bonte Creek drainage divide area south and slightly west of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 7 is 20 meters. The Cloverdale Basin is located near the west edge of figure 7 (south half). La Prele Creek originates near Cloverdale Basin and flows in a north-northeast direction to the north edge of figure 7 (west half) and north of figure 7 continues to flow in a north-northeast direction to join the east oriented North Platte River just before it turns to flow in a south, east, and southeast direction. The southwest oriented stream labeled “Creek” near the southwest corner of figure 7 is Sheep Creek, which south and west of figure 7 eventually joins the south and west oriented Little Medicine Bow River, which flows to the west and northwest oriented Medicine Bow River, which flows to the north oriented North Platte River drainage route on the west side of the Laramie Mountains. La Bonte Creek flows in an east-northeast direction from the south center edge of figure 7 through La Bonte Canyon to the east edge of figure 7 (south half). East and north of figure 7 La Bonte Creek flows in a north-northeast direction to join the east and southeast oriented North Platte River on the east side of the Laramie Mountains. South of figure 7 La Bonte Creek flows in a north direction to the south center edge of figure 7 (see figure 9). Downey Park is a north to south oriented lowland located near the center of figure 7 and is drained in the north by north oriented Wagon Hound Creek, which flows to the north edge of figure 7 (east of center). North of figure 7 Wagon Hound Creek turns to flow a north-northeast and northeast direction and eventually joins the east and southeast oriented North Platte River (east of the Laramie Mountains). The center section of Downey Park is drained by east and east-northeast oriented Gould Creek and east and north oriented Rocky Ford Creek, which flow to east and east-northeast oriented West Fork La Bonte Creek, which east of figure 7 flows in a north-northeast direction to join north-northeast oriented La Bonte Creek. The south end of the Downey Park lowland is drained by northeast, southeast, east, and south oriented Corduroy Creek, which flows to La Bonte Creek (near the south center edge of figure 7). Several streams seen in figure 7 have eroded deep water gaps across significant mountain ridges. The La Prele Creek valley near the west center edge of figure 7 is almost 400 meters deep. La Bonte Canyon is also approximately 400 meters deep while West Fork Canyon is more than 300 meters deep. Yet as seen in figure 7 these drainage routes are all linked by through valleys in the Downey Park area. The evidence in figure 7 suggests drainage routes were established at a time when the mountain ridges did not stand high above the surrounding valleys and floodwaters could flow across what are today high mountain ridges. Initially floodwaters flowed in a south and southwest directions across the region, but as the deep North Platte River valley eroded headward across the region (east of figure 7) floodwaters were reversed to flow in east, east-northeast, northeast, and north-northeast directions to reach the much deeper North Platte River valley.

Detailed map of Rocky Ford Creek-Corduroy Creek drainage divide area

Figure 8: Detailed map of Rocky Ford Creek-Corduroy Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 provides a detailed topographic map of the Rock Ford Creek-Corduroy Creek drainage divide seen in less detail in figure 7. The map contour interval for figure 8 is 40 feet. Corduroy Creek flows in a southeast and east direction from the west edge of figure 8 (south half) to the south center edge of figure 8. South of figure 8 Corduroy Creek flows in a south direction to join east-northeast and north-northeast oriented La Bonte Creek, which flows to the southeast oriented North Platte River. Rocky Fork Creek flows in an east and north direction from the west edge of figure 8 (near northwest corner) to the north edge of figure 8 (east of center). North of figure 8 Rocky Ford Creek flows in a north direction to join Gould Creek and to form east and east-northeast oriented West Fork La Bonte Creek, which then joins north-northeast oriented La Bonte Creek. A north to south oriented through valley along the west margin of section 2 and the east margin of section 3 links the south oriented Corduroy Creek valley with the north oriented Rocky Fork Creek valley. The through valley floor elevation is between 7560 and 7600 feet. The mountain ridge to the east rises to at least 8370 feet and to west (and west of figure 8) elevations rise much higher suggesting the through valley is at least 700 feet deep. The through valley was probably initiated as a south oriented flood flow channel, which continued in a south direction on the present day north oriented La Bonte Creek alignment (south of figure 7 and seen in figure 9). East-northeast oriented La Bonte Canyon may have been initiated as a west-southwest oriented flood flow channel that converged with the south oriented flood flow on the present day north oriented La Bonte Creek alignment. Headward erosion of the much deeper southeast oriented North Platte River valley to the east of figure 8 systematically beheaded and reversed the south and southwest oriented flood flow channels converging on this south oriented flood flow channel to create the present day east-northeast and north-northeast oriented La Bonte Creek drainage route and the east, east-northeast, and north-northeast oriented West Fork La Bonte Creek drainage route. South oriented flood flow from west of the emerging Laramie Mountains then was captured and flowed in northeast and north directions to the much deeper North Platte River valley and helped erode the deep La Bonte Canyon and West Fork Canyon valleys as well as the Downey Park lowland. Uplift (or at least emergence) of the Laramie Mountains was taking place as floodwaters flowed across the region and probably as headward erosion of the deep North Platte River valley around the northwest end of the Laramie Mountains beheaded and reversed flood flow channels west of the Laramie Mountains and ended all flood flow across the region seen in figure 8.

Sheep Creek-La Bonte Creek drainage divide area

Figure 9: Sheep Creek-La Bonte Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Sheep Creek-La Bonte Creek drainage divide area south and west of figure 7 and there is an overlap area with figure 7. The map contour interval for figure 9 is 20 meters. The Cloverdale Basin is located near the northwest corner of figure 9 and is on the northwest side Chimney Ridge. La Prele Creek originates north of the Cloverdale Basin and flows in a north-northeast direction to the north edge of figure 9 (west half). Sheep Creek originates on the south side of Chimney Ridge and flows in a south direction to the south edge of figure 9 (west half). South of figure 9 Sheep Creek flows in a south and southwest direction to join the south and west oriented Little Medicine Bow River, which then joins the west and northwest oriented Medicine Bow River, which then flows to the north oriented North Platte River on the west side of the Laramie Mountains. Manse Creek is a south and west oriented tributary joining Sheep Creek in the southwest quadrant of figure 9. La Bonte Creek originates near the south center edge of figure 9 and flows in a northeast direction into Fortymile Flat and then in a north direction before turning in an east-northeast direction to flow through La Bonte Canyon to reach the east edge of figure 9 (north of center). East of figure 9 La Bonte Creek turns to flow in a north-northeast direction to join the southeast oriented North Platte River as a barbed tributary. The south end of Fortymile Flat (south of figure 9) is drained by the south oriented North Laramie River headwaters. Brush Creek is an east oriented La Bonte Creek tributary located in the south center region of figure 9. The east oriented Brush Creek valley is linked by a through valley with the west oriented Manse Creek valley. The through valley floor elevation at the road intersection is shown as being 2396 meters. Fortymile Peak to the south of Brush Creek rises to 2673 meters and Camelback Mountain to the north of Brush Creek rises to 2756 meters suggesting the Brush Creek-Manse Creek through valley is at least 275 meters deep. This through valley links the north, east-northeast, and north-northeast oriented La Bonte Creek valley with the south and southwest oriented Sheep Creek valley. Today the La Bonte Creek valley drains to the southeast oriented North Platte River valley on the east side of the Laramie Mountains and the Sheep Creek valley eventually drains to the north oriented North Platte River valley on the west side of the Laramie Mountains. The through valley probably was initiated by southwest oriented flood flow moving across the emerging Laramie Mountains. Later as headward erosion of the deep southeast oriented North Platte River valley on the east side of the Laramie Mountains beheaded and reversed south oriented flood flow channels in sequence from east to west floodwaters in the through valley were reversed to flow in a northeast direction to the much deeper southeast oriented North Platte River valley. Headward erosion of the deep North Platte River valley around the northwest end of the Laramie Mountain eventually beheaded and reversed flood flow channels west of the Laramie Mountains to create the north oriented North Platte River drainage route in that region. Creation of the north oriented North Platte River drainage route west of the Laramie Mountains ended all flood flow in the Manse Creek-Brush Creek through valley and created the present day Manse Creek-Brush Creek drainage divide. This description of generalized flood flow movements omits many details, which can be determined from numerous other through valleys, elbows of capture, barbed tributaries, and similar evidence found throughout the region.

Detailed map Brush Creek-Manse Creek drainage divide area

Figure 10: Detailed map of Brush Creek-Manse 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 Brush Creek-Manse Creek drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 20 feet. Manse Creek flows from the north edge of figure 10 (west of center) in a south direction into section 1 where it turns to flow in a west direction to the west edge of figure 10. West of figure 10 Manse Creek joins south and southwest oriented Sheep Creek, which flows to the south and west oriented Little Medicine Bow River, which in turn flows to the west and northwest oriented Medicine Bow River, which flows to the north oriented North Platte River west of the Laramie Mountains. Badger Creek originates near the south center edge of figure 10 and flows in a north and west direction to join Manse Creek in section 1. Brush Creek flows in a south direction from the north edge of figure 10 (east of center) into section 6 where it turns to flow in an east direction to the east edge of figure 10 (north half). East of figure 10 Brush Creek joins north, east-northeast, and north-northeast oriented La Bonte Creek, which flows to the southeast oriented North Platte River east of the Laramie Mountains. A deep west to east oriented through valley in sections I and 6 links the east oriented Brush Creek valley with the west oriented Manse Creek valley. The through valley floor elevation at the road intersection near the west margin of section 6 is 7861 feet. Fortymile Peak in the southeast corner of figure 10 rises 8789 feet and Camelback Mountain north of the northeast quadrant of figure 10 rises to 9047 feet suggesting the through valley is approximately 900 feet deep. The through valley is a water-eroded valley, although its orientation may have been influenced by geologic structures. The through valley links drainage routes to the north oriented North Platte River valley west of the Laramie Mountains with drainage routes to the southeast oriented North Platte River east of the Laramie Mountains. Probably the through valley was first eroded by southwest oriented flood flow moving across the emerging Laramie Mountains prior to headward erosion of the southeast oriented North Platte River valley east of the Laramie Mountains. Headward erosion of the deep southeast oriented North Platte River valley beheaded and reversed the southwest oriented flood flow channel to create a northeast oriented flood flow channel, which captured south oriented flood flow from west of the Laramie Mountains and diverted the floodwaters in an east and northeast direction to the much deeper North Platte River valley east of the Laramie Mountains. Headward erosion of the deep North Platte River valley around the northwest end of the Laramie Mountains beheaded and reversed flood flow channels west of the Laramie Mountains to create the north oriented North Platte River drainage route west of the Laramie Mountains, which then beheaded and reversed flood flow routes moving in east and northeast directions to and across the Laramie Mountains to reach the deep southeast oriented North Platte River valley east of the Laramie Mountains and which also created the Manse-Brush Creek drainage divide.

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.