Abstract:

This essay uses topographic map evidence to interpret landform origins in the Sybille Creek-Chugwater Creek drainage divide area in the Wyoming Laramie Mountains. Chugwater Creek headwaters originate on the west edge of the Laramie Mountains and flow in an east and northeast direction across the Laramie Mountains and then on the east side of the Laramie Mountains Chugwater Creek turns to flow in a north, north-northwest, and northeast direction to join the east and northeast oriented Laramie River, which flows to the southeast oriented North Platte River. Sybille Creek headwaters originate north of the Chugwater Creek headwaters and flow in a northwest direction to the west side of the Laramie Mountains and then flow for a short distance west of the Laramie Mountains before Sybille Creek turns to flow in a northeast direction across the Laramie Mountains and on the east side of the Laramie Mountains Sybille Creek turns to flow in a north direction to join the east and northeast oriented Laramie River. North oriented tributaries join Sybille Creek both in the Laramie Mountains and east of the Laramie Mountains and are linked by through valleys with Chugwater Creek tributary valleys. Drainage route orientations, through valleys, barbed tributaries, elbows of capture, and escarpments 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 to and across Wyoming at a time when the Laramie Mountains were just beginning to emerge. At first floodwaters flowed along the present day crest of the Laramie Mountains and on both sides of the emerging Laramie Mountains in complexes of diverging and converging south oriented flood flow channels, which eroded valleys into the emerging mountain mass. The deep southeast oriented North Platte River valley then eroded headward into the region east of the Laramie Mountains and the deep east and northeast oriented Laramie River valley eroded headward from the actively eroding North Platte River valley head to capture flood flow west of the North Platte River valley head. As the Laramie River valley eroded headward it beheaded flood flow channels in sequence from east to west. Floodwaters on north ends of beheaded flood flow channels reversed flow direction to create north oriented Laramie River tributary drainage routes. These reversed drainage routes often captured flood flow still moving in a south direction further to the west, which enabled northeast and east oriented valleys to erode headward from the newly reversed flood flow channels. Flood flow on the Chugwater Creek alignment was beheaded and reversed first and the east and northeast oriented Chugwater Creek valley eroded headward to capture flood flow still moving in a south direction in the emerging Laramie Mountains. Next headward erosion of the Laramie River valley beheaded and reversed flood flow on the Sybille Creek alignment and the northeast oriented Sybille Creek valley eroded headward across the Laramie Mountains and beheaded and reversed flood flow channels to the newly eroded Chugwater Creek and tributary valleys. Headward erosion of the northeast oriented Sybille Creek valley beheaded and reversed a flood flow channel west of the Laramie Mountains, which in turn beheaded and reversed a southeast oriented flood flow channel, which had supplied floodwaters to an actively eroding Chugwater Creek headwaters valley. Headward erosion of the deep Laramie River valley (north of the Sybille Creek valley) then captured all flood flow routes to the newly eroded Sybille Creek and tributary valleys.

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 Sybille Creek-Chugwater Creek 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 Sybille Creek-Chugwater Creek drainage divide area landform evidence in the Wyoming Laramie Mountains will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Sybille Creek-Chugwater Creek drainage divide area location map

Figure 1: Sybille Creek-Chugwater 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 Sybille Creek-Chugwater Creek drainage divide area in the Wyoming Laramie Mountains and illustrates a region in southeastern Wyoming. The Wyoming-Colorado border is located along the south edge of figure 1 and the Wyoming-Nebraska border is located along the east edge of figure 1. The Laramie Mountains extend in a north to south direction across the center of figure 1 and the Medicine Bow Mountains are located near the west edge of the south half of figure 1. The Laramie Basin is located between the Medicine Bow Mountains and the Laramie Mountains and the Great Plains are located east of the Laramie Mountains. The North Platte River flows in a north-northwest direction across the southwest corner of figure 1 and west and north of figure 1 flows in a north direction to the northwest end of the Laramie Mountains and then turns in an east and southeast direction to flow across the northeast corner of figure 1. The Laramie River flows in a north and northeast direction from the south edge of figure 1 (west half) to the city of Laramie and then flows in a north direction to just north of Wheatland Reservoir where it turns to flow in an east and northeast direction across the Laramie Mountains and then in an east and northeast direction to join the North Platte River near the town of Fort Laramie. Chugwater Creek originates in the Laramie Mountains (north and east of Laramie) and flows in an east and northeast direction to the town of Chugwater on the east side of the Laramie Mountains and then in a north direction to join the Laramie River (slightly north and east of Wheatland). Sybille Creek is the unlabeled northeast and north oriented stream flowing from near Morton Pass (north of Laramie) to join the Laramie River north and west of Wheatland. The Sybille Creek-Chugwater Creek drainage divide area investigated in this essay is located south and east of Sybille Creek and north and west of Chugwater Creek and includes regions in and east of the Laramie Mountains.

The North Platte River and tributary drainage routes, including all drainage routes in 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 to and across the region in figure 1 at a time when the Laramie Mountains were beginning to emerge. At first floodwaters flowed along, across, and adjacent to the emerging Laramie Mountains in anastomosing complexes of diverging and converging south oriented flood flow channels. As the Laramie Mountains emerged these flood flow channels eroded deep valleys into the emerging mountain mass while headward erosion of deeper valleys captured water from shallower flood flow channels. Often floodwaters on beheaded flood flow channels would reverse flow directions to flow toward the deeper beheading valley. The south oriented flood flow channels flowing along and near the present day crest of the Laramie Mountains were in this manner gradually captured by headward erosion of northeast and east oriented valleys eroding headward from the much deeper southeast oriented North Platte River valley, which was eroding headward in the region east of the emerging Laramie Mountains. Several northeast and east oriented valleys successfully eroded headward across the emerging Laramie Mountains and captured southeast and south oriented flood flow channels on the west side of the Laramie Mountains. The northeast and north oriented Sybille Creek valley was one of the first such valleys to capture flood flow on the west side of the Laramie Mountains, although headward erosion of the Laramie River valley subsequently captured all flood flow routes to the newly eroded Sybille Creek valley. For a period of time as these valleys were eroding headward across the emerging Laramie Mountains large volumes of south and southeast floodwaters from west of the Laramie Mountains moved across the Laramie Mountains to reach the much deeper North Platte River valley east of the Laramie Mountains, which means a northeast and east oriented anastomosing channel complex captured a south oriented anastomosing channel in what are today the Laramie Mountains. Headward erosion valleys from east of the Laramie Mountains into the Laramie Basin also beheaded south oriented flood flow routes in the Laramie Basin. Aided by ice sheet crustal warping that was raising mountain ranges at the south end of the Laramie Basin floodwaters on north ends of these beheaded flood flow routes reversed flow direction to create the present day north oriented Laramie River drainage route on the west side of the Laramie Mountains.

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

Figure 2: Detailed location map Sybille Creek-Chugwater 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 Sybille Creek-Chugwater Creek drainage divide area in the Wyoming Laramie Mountains. The Laramie Mountains extend in a north to south direction across the center of figure 2. The Great Plains are located east of the Laramie Mountains while the Laramie Basin is on the west side of the Laramie Mountains. Albany County is located in the west half of figure 2 and Platte County is located in the east half of figure 2. Laramie County is the county south of Platte County. The Laramie River flows in a north-northeast direction from south edge of figure 2 (west half) to just north of Wheatland Reservoir Number 2 and then turns to flow in an east, north-northeast, east, northeast, and east direction to the northeast corner of figure 2. A northeast oriented highway (#34) extends from Bosler Junction (near south edge of figure 2) to Wheatland and follows northeast oriented North Sybille Creek to where it joins north-northeast oriented Middle Sybille Creek and then north-northeast, north, and north-northeast South Sybille Creek to form Sybille Creek and then follows Sybille Creek to near Natwick (south and west of Wheatland). The highway is following the Sybille Creek valley across the Laramie Mountains. Mule Creek, Deadhead Creek, and Brush Creek are north oriented Sybille Creek tributaries in the southwest corner of Platte County. Farthing is a town in the northwest corner of Laramie County near the south center edge of figure 2. Chugwater Creek is formed at the confluence of South Chugwater Creek and Middle Chugwater Creek near Farthing and then flows in a northeast, north, north-northwest, and north direction to join the Laramie River north of Wheatland (the railroad follows the Chugwater Creek valley from Farthing to Wheatland). North Chugwater Creek is an east oriented tributary joining Chugwater Creek near the town of Diamond (near south edge of Platte County). The Richeau Hills are located in the southwest corner of Platte County. Richeau Creek originates on the south side of the Richeau Hills and flows in a east direction (just north of North Chugwater Creek) before turning to flow in a northeast direction to join Chugwater Creek near the town of Slater. Maxwell Creek is a southeast oriented (and barbed) tributary to Richeau Creek east of the Richeau Hills. Hunton Creek is an east and northeast oriented tributary joining Chugwater Creek near the town of Bordeau and South Hunton Creek is a northeast, east, and northeast oriented Hunton Creek tributary. Prior to headward erosion of the deep northeast oriented Sybille Creek valley floodwaters flowed in south directions along the present day Laramie Mountains crest to reach the east oriented North Chugwater Creek valley and further to the west to reach the east oriented Middle Chugwater Creek and tributary valleys. The north oriented Sybille Creek tributaries and headwaters were formed by reversals of flood flow on north ends of beheaded flood flow channels as the deep northeast oriented Sybille Creek valley eroded headward across what at that time were the emerging Laramie Mountains.

Middle Sybille Creek-Middle Chugwater Creek drainage divide area east end

Figure 3: Middle Sybille Creek-Middle Chugwater Creek drainage divide area east end. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of Middle Sybille Creek-Middle Chugwater Creek drainage divide area east end. The map contour interval for figure 3 is 20 meters. The western margin of the Laramie Mountains is located in the west half of figure 3 and the eastern margin of the Laramie Basin is located along the west edge of figure 3. Plumbago Creek flows in a northwest and north direction in the northwest quadrant of figure 3 and north of figure 3 becomes east and northeast oriented North Sybille Creek, which flows to northeast and north oriented Sybille Creek, which joins the Laramie River on the east side of the Laramie Mountains. Middle Sybille Creek originates south of the Plumbago Creek headwaters and flows in a northeast and north-northeast direction to the north edge of figure 3 (east of center) and north of figure 3 joins northeast oriented North Sybille Creek. South Sybille Creek (not labeled in figure 3) originates west of the east center edge of figure 3 and flows in a north, northeast, and north direction to the north edge of figure 3 (near northeast corner).  North of figure 3 South Sybille Creek joins northeast oriented North Sybille Creek to form northeast and north oriented Sybille Creek. Middle Chugwater Creek originates just south of figure 3 in the Laramie Mountains and flows in an east-northeast from the south edge of figure 3 (west of center and south of The Buttes) to the east edge of figure 3 (near southeast corner) and east of figure 3 flows to northeast and north oriented Chugwater Creek. Strong Creek originates near the west margin of the Laramie Mountains in the southwest quadrant of figure 3 and flows in an east and south direction to join Middle Chugwater Creek near the southeast corner of figure 3. North oriented Sybille Creek tributaries originated as south oriented flood flow channels, which were captured by headward erosion of the east oriented Middle Chugwater Creek valley and then by headward erosion of the east oriented Strong Creek valley. Headward erosion of the deep northeast oriented North Sybille Creek valley (north of figure 3) then beheaded the south oriented flood flow channels in sequence from east to west. First to be beheaded was flood flow on the present day north oriented South Sybille Creek alignment. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented South Sybille Creek drainage route. Next headward erosion of the deep North Sybille Creek valley beheaded and reversed flood flow on the Middle Sybille Creek alignment. The reversed flood flow captured south oriented flood flow still moving on the present day north oriented Plumbago Creek alignment and the captured flood flow moved in a southeast direction on the present day northwest oriented Plumbago Canyon alignment before moving in a north-northeast direction on the Middle Sybille Creek alignment. Continued headward erosion of the deep northeast oriented North Sybille Creek valley next beheaded and reversed flood flow on the north end of the Plumbago Creek alignment to create the present day northwest and north oriented Plumbago Creek drainage route.

Detailed map of South Sybille Creek-Strong Creek drainage divide area

Figure 4: Detailed map of South Sybille Creek-Strong 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 South Sybille Creek-Strong Creek drainage divide area seen in less detail in figure 3. The map contour interval for figure 4 is 20 feet. Strong Creek flows in an east direction from the west edge of figure 4 (south half) into section 22 where it turns to flow in a south-southeast direction to the south edge of figure 4. South of figure 4 Strong Creek joins east oriented Middle Chugwater Creek to flow to northeast and north oriented Chugwater Creek, which then flows to the east and northeast oriented Laramie River, which flows to the southeast oriented North Platte River. South Sybille Creek flows from the small lake in the southeast corner of section 10 into section 11 and then flows in a north direction to the north edge of figure 4 (east half). North of figure 6 South Sybille Creek flows in a north direction to join northeast oriented North Sybille Creek and to form northeast and north oriented Sybille Creek, which then joins the east and northeast oriented Laramie River. An unnamed east and southeast oriented stream originates in section 14 and flows to east edge of figure 4 (south half) and east of figure 4 flows to a south oriented Middle Chugwater Creek tributary. Through valleys in the west half of section 14 and the east half of section 15 link the north oriented South Sybille Creek valley with the east and southeast oriented stream valley in section 14 and with a south oriented Strong Creek tributary valley. The through valley in northwest quadrant of section 14 has a floor elevation of between 7240 and 7260 feet. Elevations on the ridge in section 11 to the northeast rise to 7601 feet and in section 17 to the west rise to 7626 feet. These elevations suggest the through valley is at least 340 feet deep. The through valley was eroded by south oriented flood flow, which first moved in a south direction to the south-southeast oriented Strong Creek valley and then to the east oriented Middle Chugwater Creek valley. Headward erosion of the east and southeast oriented valley into section 14 captured the south oriented flood flow and diverted floodwaters in an east, southeast, and south direction to the Middle Chugwater Creek valley. Probably for a time floodwaters flowed in diverging flood flow channels with the east, southeast, and south oriented channel eroding a deeper valley and capturing most, or all of the south oriented flood flow. Headward erosion of the deep northeast oriented North Sybille Creek valley north of figure 4 beheaded the south oriented flood flow channel and floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented South Sybille Creek drainage route. It is possible ice sheet related crustal warping was raising the Laramie Mountains as these flood flow movements, captures, and reversals were taking place and contributed to flood flow capture and reversal process.

Deadhead Creek-North Chugwater Creek drainage divide area

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

Figure 5 illustrates the Deadhead Creek-North Chugwater Creek drainage divide area north and east of figure 3 and there is an overlap area with figure 3. The map contour interval for figure 5 is 20 meters. North Sybille Creek flows from the west edge of figure 5 (north half) through North Sybille Canyon to the norh edge of figure 5 (west half) and north of figure 5 joins South Sybille Creek to form northeast and north Sybille Creek, which flows to the east and northeast oriented Laramie River, which flows to the southeast oriented North Platte River. South Sybille Creek flows in a north, northeast, north, and northeast direction from the south edge of figure 5 (west half) to the north edge of figure 5 (west of center) and north of figure 5 joins North Sybille Creek to form northeast and north oriented Sybille Creek. Mule Creek originates north of the south center edge of figure 5 and flows in an east and north direction to the north center edge of figure 5 (just west of Sheep Mountain) and north of figure 5 joins northeast and north oriented Sybille Creek. Sheep Mountain is located on a north to south oriented hogback ridge that extends into the south half of figure 5. Deadhead Creek originates east of the south end of that hogback ridge and flows in an east, northwest, and north direction to the north edge of figure 5 (east of Sheep Mountain) and north of figure 5 joins Sybille Creek. North Chugwater Creek originates north of the south center edge of figure 5 (and just south of the Mule Creek headwaters) and flows in an east direction to the east edge of figure 5 (south half). East of figure 5 North Chugwater Creek flows to northeast and north oriented Chugwater Creek, which then flows to the east and northeast oriented Laramie River. The north oriented Sybille Creek tributary drainage routes originated as south oriented flood flow channels prior to headward erosion of the northeast oriented Sybille-North Sybille Creek valley to the north. Headward erosion of east oriented valleys from a south oriented flood flow channel east of figure 5 or from the actively eroding northeast oriented Chugwater Creek valley (east of figure 5) may have captured south oriented flood flow on the Deadhead Creek and Mule Creek alignments and diverted the floodwaters in an east direction. Headward erosion of the deep northeast oriented Sybille-North Sybille Creek valley then beheaded the south oriented flood flow channels in sequence from east to west. Floodwaters on north ends of beheaded flood flow channels reversed flow direction to create north oriented Sybille Creek tributary drainage routes. The flood flow reversals captured some of the east oriented flood flow to create the east oriented Deadhead Creek and Mule Creek headwaters.

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

Figure 6: Detailed map of Mule Creek-North Chugwater 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 Mule Creek-North Chugwater Creek drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 20 feet. North Chugwater Creek flows in an east, northeast, and east direction from the south edge of figure 6 (west half) to the east edge of figure 6 (south half) and east of figure 6 flows to northeast and north oriented Chugwater Creek, which then flows to the east and northeast oriented Laramie River. Mule Creek flows in an east direction from the west edge of figure 6 (south half) into the northwest corner of section 24 and then turns to flow in a north and north-northwest direction to the north edge of figure 6 (west of center). Deadhead Creek flows in an east direction in the northeast quadrant of figure 6 to the east edge of figure 6 (north half). East of figure 6 Deadhead Creek turns to flow in a northwest and north direction to join northeast and north oriented Sybille Creek. A through valley in the north half of section 24 links the north oriented Mule Creek valley with the east oriented North Chugwater Creek valley. The through valley floor elevation at its lowest point is between 6600 and 6620 feet. Elevations in section 22 to the west (along west edge of figure 6) rise to 7128 feet and west of figure 2 rise to more than 7200 feet. Elevations in section 13 just to the east of the through valley rise to more than 6780 feet with an elevation of 6952 feet being found east of Mule Creek just north of figure 6. Using the nearby elevations the through valley is at least 160 feet deep and using more distant elevations the through valley could be as much as 330 feet deep. In either case the through valley was eroded by south oriented flood flow prior to headward erosion of the deep northeast oriented Sybille Creek valley north of figure 6. A north to south oriented through valley in section 12 links a north oriented Deadhead Creek tributary valley with a southwest oriented Mule Creek tributary valley. The floor elevation of this second through valley is between 6480 and 6500 feet. The high point immediately to the east rises to 6810 feet and the high point immediately to the west rises to 6812 feet suggesting the through valley is at least 310 feet deep. The through valley was initiated as a south oriented flood flow channel. However, headward erosion of deep Sybille Creek valley beheaded and reversed flood flow on the present day north oriented Deadhead Creek alignment before it beheaded and reversed flood flow on the Mule Creek alignment. Reversed flood flow on the Deadhead Creek alignment captured south oriented flow still moving on the Mule Creek alignment and the captured floodwaters made a U-turn in section 12 to flow around the south end of the north to south oriented ridge and then to flow in a north direction on the Deadhead Creek alignment to the Sybille Creek valley. Headward erosion of the deep northeast oriented Sybille Creek valley then beheaded and reversed flow on the Mule Creek alignment, which captured south and southeast oriented flood flow further to the west and this captured flood flow moved in an east direction on the present day east oriented Mule Creek headwaters alignment to reach the newly reversed Mule Creek flood flow channel and to flow to the much deeper Sybille Creek valley.

Brush Creek-Maxwell Creek drainage divide area

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

Figure 7 illustrates the Brush Creek-Maxwell Creek drainage divide area north and east of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 7 is 20 meters. Richeau Creek flows in a north-northeast and northeast direction from the south center edge of figure 7 to the east edge of figure 7 (north half) and east of figure 7 joins north oriented Chugwater Creek, which then flows to the east and northeast oriented Laramie River. Watergap Creek is located in the southwest quadrant of figure 7 and flows in a southeast direction to join Richeau Creek as a barbed tributary near the south center edge of figure 7. The Richeau Hills are located west of the center of figure 7. Maxwell Creek originates on the south side of the Richeau Hills and then flows in a southeast direction to join north-northeast oriented Richeau Creek as a barbed tributary. North Richeau Creek originates on the north side of the Richeau Hills and flows in an east-northeast and east direction to join Richeau Creek (near the east edge of figure 7). South Hunton Creek is located north of North Richeau Creek and flows in a northeast, east-northeast, and northeast direction to the north edge of figure 7 (east half) and north of figure 7 joins Hunton Creek, which then flows in an east and northeast direction to join a northwest oriented segment of Chugwater Creek. Brush Creek originates just south of the west end of the Richeau Hills and flows in a northwest and north direction to the north edge of figure 7 (west half) and north of figure 7 joins Sybille Creek, which then flows in a north direction to join the east and northeast oriented Laramie River. A northwest to southeast oriented through valley on the southwest side of the Richeau Hills links the northwest oriented Brush Creek headwaters valley with the southeast oriented Maxwell Creek valley. The through valley floor elevation is between 1900 and 1920 meters. Elevations on the southwest side of the through valley rise to more than 2100 meters while elevations in the Richeau Hills to the northeast rise to at least 2080 meters. These elevations suggest the through valley is 160 meters deep. The through valley was eroded by southeast oriented flood flow moving from the present day north oriented Brush Creek and Sybille Creek alignments to a south oriented flood flow channel on the present day north oriented Richeau Creek alignment, which was beheaded and reversed by headward erosion of the deep Laramie River valley (north of figure 7) prior to the beheading and reversal of flood flow on the Brush Creek-Sybille Creek alignment. The reversal of flood flow on the Brush Creek-Sybille Creek alignment ended south and southeast oriented flood flow to the southeast oriented Maxwell Creek valley. Other somewhat shallower through valleys and valley orientations seen in figure 7 provide evidence of additional flood flow movements as Richeau Hills landforms were eroded.

Detailed map of Brush Creek-Maxwell Creek drainage divide area

Figure 8: Detailed map of Brush Creek-Maxwell 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 Brush Creek-Maxwell Creek drainage divide area seen in less detail in figure 7. The map contour interval for figure 8 is 20 feet. Brush Creek originates in section 13 and flows in a west-northwest direction to the west edge of figure 8 (north of center). West of figure 8 Brush Creek turns to flow in a north direction to join Sybille Creek, which then flows in a north direction to join the east and northeast oriented Laramie River. Maxwell Creek originates in the northwest quadrant of section 18 and flows in a southeast direction to the east edge of figure 8 (near southeast corner). East and south of figure 8 Maxwell Creek joins northeast oriented Richeau Creek, which flows to north oriented Chugwater Creek, which then flows to the east and northeast oriented Laramie River, which flows to the southeast oriented North Platte River. A through valley near the north edge of section 13 links the west-northwest oriented Brush Creek valley with the southeast oriented Maxwell Creek valley. The through valley floor elevation at the drainage divide is between 6260 and 6280 feet. Elevations near the south edge of section 14 rise to more than 6900 feet and a high point in the Richeau Hills (near north center edge of figure 8) rises to more than 6800 feet. These elevations suggest the through valley is at least 500 feet deep. The through valley is a water-eroded valley and was eroded by southeast oriented flood flow moving from a south oriented flood flow channel on the present day north oriented Brush-Sybille Creek alignment west of figure 8 to a south oriented flood flow channel east of figure 8, although headward erosion of the deep east and northeast oriented Laramie River valley beheaded and reversed flood flow on the Richeau-Chugwater Creek alignment while south oriented flood flow was still moving on the Brush-Sybille Creek alignment. Subsequently headward erosion of the Laramie River valley beheaded and reversed flood flow on the Brush-Sybille Creek alignment and created the Brush Creek-Maxwell Creek drainage divide seen in figure 8.

Brush Creek-Chugwater Creek drainage divide area

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

Figure 9 illustrates the Brush Creek-Chugwater Creek drainage divide area north and east of figure 7 and there is a large overlap area with figure 7. The map contour interval for figure 9 is 20 meters. Chugwater Creek flows in a north and north-northwest direction from the east edge of figure 9 (south half) to the north edge of figure 9 (near northeast corner). North of figure 9 Chugwater Creek flows in a northwest and north-northeast direction to join the east and northeast oriented Laramie River, which then flows to the southeast oriented South Platte River. Richeau Creek flows in a northeast direction from the south center edge of figure 9 to join Chugwater Creek north of the town of Slater (Slater is located near the east center edge of figure 9). The Richeau Hills are located near the southwest corner of figure 9. North Richeau Creek originates north of the east end of the Richeau Hills and flows in a northeast, east-northeast, and east direction to join Richeau Creek. South Hunton Creek originates north of the Richeau Hills and flows in a northeast, east-northeast, and northeast direction to join east and northeast oriented Hunton Creek, which joins Chugwater Creek south of the town Bordeaux (near northeast corner of figure 9). Hunton Creek flows in an east-northeast direction north of the South Hunton Creek headwaters and after being joined by South Hunton Creek turns flows in an east northeast direction. Antelope Creek originates in the north center area of figure 9 (norh of Hunton Creek) and flows in a northeast direction to the north edge of figure 9 (east half) and joins Chugwater Creek north of figure 9. Brush Creek flows in a north-northeast and northwest direction from the west edge of figure 9 (south half) to the north edge of figure 9 (near northwest corner) and north of figure 9 joins north oriented Sybille Creek, which flows to the east and northeast oriented Laramie River. Chugwater Creek has a much better developed system of east and northeast oriented tributaries than Brush Creek has on the west  side of the drainage divide. The difference probably is because south oriented flood flow on the Chugewater Creek alignment was beheaded and reversed by headward erosion of the deep east and northeast oriented Laramie River valley while floodwaters were still flowing in a south direction on the Brush Creek alignment. The reversal of flood flow on the Chugwater Creek alignment captured south oriented flood flow still moving on the Brush Creek alignment and the captured flood flow moved in east and northeast directions to reach what was at that time the actively eroding north oriented Chugwater Creek valley. By the time headward erosion of the deep Laramie River beheaded and reversed flood flow on the Brush Creek alignment the Chugwater Creek valley had already been eroded so whatever north oriented flood flow was moving in the valley no longer could move in a west or northwest direction to the north oriented valley developing on the Brush Creek alignment. However south and west of figure 9 the reversed flood flow on the Brush Creek alignment captured south oriented flood flow still moving west of the actively eroding Laramie River valley head. This captured flood flow moved in a north direction and eroded the deep Brush Creek valley so there are few west and northwest oriented Brush Creek tributaries.

Detailed map of Brush Creek-Hunton Creek drainage divide area

Figure 10: Detailed map of Brush Creek-Hunton 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-Hunton Creek drainage divide area seen is less detail in figure 9. The map contour interval for figure 10 is 20 feet. Brush Creek flows in a north, north-northeast, and north direction from the southwest corner of figure 10 to the north edge of figure 10 (west half) and north of figure 10 joins north oriented Sybille Creek to flow to the east and northeast oriented Laramie River. Hunton Creek originates near the southwest corner of section 20 and flows in a northeast and east direction to the east edge of figure 10 (north of center) and east of figure 10 flows in an east and northeast direction to join north oriented Chugwater Creek, which then flows to the east and northeast oriented Laramie River. South Hunton Creek flows in a northeast and east direction from the south center edge of figure 10 to the east edge of figure 10 (south half) and east of figure 10 turns to flow in a northeast direction to join Hunton Creek. The Brush Creek-Chugwater Creek drainage divide follows the rim of a west and northwest-facing escarpment that extends from the south center edge of figure 10 to the north edge of figure 10 (east half). In sections 24 and 19 (near center of figure 10) the escarpment is approximately 400 feet high. A close look at the escarpment rim reveals the escarpment has truncated shallow west to east oriented valleys. Two or more contour lines on a side define the each of these truncated valleys as the escarpment rim elevation decreases in a north direction. The truncated valleys are evidence of what at one time were diverging and converging east oriented flood flow channels, which were probably moving floodwaters to a newly beheaded and reversed flood flow channel on the present day north oriented Chugwater Creek alignment. At that time the deep north oriented Brush Creek valley did not exist and the deep Laramie River valley (north of figure 10) was still being eroded headward across south oriented flood flow routes, which were being captured and diverted in an east direction to the actively eroding east and northeast oriented Chugwater Creek tributary valleys. Headward erosion of the deep Laramie River valley changed the situation by beheading and reversing flood flow to create the north oriented Brush Creek drainage route, which then captured south and southeast oriented flood flow from further to the west. The captured flood flow then moved in a north direction to the much deeper Laramie River valley and eroded the deep north oriented Brush Creek valley with the west and northwest-facing escarpment being the east wall of that valley. Erosional residuals such as those seen in and near section 23 may be composed of more resistant rock and/or they may be evidence the north oriented Brush Creek valley was eroded by a complex of north oriented diverging and converging flood flow channels.

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.