Boulder Creek-Clear Creek drainage divide area landform origins in the Colorado Front Range, USA

Authors

 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the Boulder Creek-Clear Creek drainage divide area in the Colorado Front Range. Clear Creek originates near the east-west continental divide and south of Berthoud Pass and then flows in an east direction to Golden at the eastern flank of the Colorado Front Range and then in an east-northeast direction to join the north-northeast, north, northeast, southeast, and northeast oriented South Platte River. South Boulder Creek is located north of Clear Creek and originates near the continental divide and then flows in a northeast and east direction onto the Colorado Piedmont where it turns to flow in a north direction to join northeast oriented Boulder Creek, which flows to northeast oriented St Vrain Creek, which then flows to the north, northeast, southeast, and northeast oriented South Platte River. Deep north-to-south oriented through valleys cross the South Boulder Creek-Clear Creek drainage divide and link north oriented South Boulder Creek tributary valleys with south oriented Clear Creek tributary valleys. The through valleys are interpreted to have been eroded by south oriented flood flow channels prior to headward erosion of the east oriented South Boulder Creek valley. Floodwaters are interpreted to have flowed from the western margin of a thick North American ice sheet (probably in western Canada) to and across Colorado at a time when the Colorado Front Range was beginning to emerge. The Front Range emerged as floodwaters were flowing across it, as ice sheet related crustal warping raised mountain masses, and as deep valleys eroded headward into Colorado to capture the massive south oriented melt water flood flow. Initially floodwaters flowed in south directions, but flood flow directions changed as crustal warping raised mountain areas and entire regions and as deep valleys beheaded diverging and converging south oriented flood flow channels. In Colorado east oriented valleys eroded headward (in sequence from south to north) from south oriented flood flow channels on the Colorado Piedmont to capture south oriented flood flow in the emerging Colorado Front Range with headward erosion of the east oriented South Boulder Creek valley beheading flood flow routes to what was at that time the newly eroded east oriented Clear Creek valley. As these east oriented valleys were capturing flood flow in the emerging Front Range headward erosion of the deep southeast and northeast oriented South Platte River valley from western Nebraska beheaded south oriented flood flow channels on the Colorado Piedmont (in sequence from east to west). Floodwaters on north ends of the beheaded flood flow channels reversed flow direction to create north oriented South Platte River tributary drainage routes and the north oriented South Platte River drainage route and captured the flood flow, which the east oriented valleys were capturing in the emerging Colorado Front Range.

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 Boulder Creek-Clear Creek drainage divide area landform origins in the Colorado Front Range. 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 Boulder Creek-Clear Creek drainage divide area landform evidence in the Colorado Front Range will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Boulder Creek-Clear Creek drainage divide area location map

Fig1 locmap

Figure 1: Boulder Creek-Clear 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 Boulder Creek-Clear Creek drainage divide area in the Colorado Front Range and illustrates a region in north central Colorado. The Colorado Front Range is the mountain area located west of the cities of Loveland, Longmont, Boulder, and Lakewood. Rocky Mountain National Park is shown and labeled. The South Platte River flows in a north-northeast direction from the south edge of figure 1 to Denver, Fort Lupton, and Milliken and then turns to flow in a northeast and southeast direction to the east edge of figure 1 (north half). East of figure 1 the South Platte River turns to flow in a northeast direction to flow into western Nebraska to join the Nebraska Platte River with water eventually reaching the Gulf of Mexico. Streams near the east edge of figure 1 are north oriented South Platte River tributaries. The Big Thompson River originates in Rocky Mountain National Park and flows in a southeast, northeast, and east-southeast direction to join the North Platte River near Milliken. The unlabeled southeast and northeast oriented stream flowing from Lyons to Longmont and then to join the South Platte River is St Vrain Creek. The east and northeast oriented St Vrain Creek tributary flowing near the city of Boulder and joining St Vrain Creek east of Longmont is Boulder Creek. Berthoud Pass is located south of Rocky Mountain National Park. Clear Creek, which is not labeled and which is poorly shown in figure 1, originates south of Berthoud Pass and flows in an east direction to Golden and then continues in an east-northeast direction to join the South Platte River north of Denver. A separate essay addresses the Fraser River-Boulder Creek drainage divide area along the east-west continental divide and illustrates and discusses the Berthoud Pass region. The Boulder Creek-Clear Creek drainage divide area in the Colorado Front Range investigated in this essay is located south of Boulder Creek, north of Clear Creek, east of the continental divide, and west of Golden.

Drainage routes in Colorado developed during immense melt water floods from a thick North American ice sheet at a time when Colorado mountain ranges were beginning to emerge. Floodwaters flowed from western Canada to and across Colorado as Colorado mountain ranges emerged. Colorado mountain ranges emerged as floodwaters flowed across them, as ice sheet related crustal warping raised the mountain masses and the entire state of Colorado, and as deep valleys eroded headward into Colorado from the Gulf of Mexico and the Pacific Ocean to capture the massive south oriented flood flow. Initially floodwaters flowed in south directions, but flood flow directions changed and were sometimes reversed as crustal warping raised mountain regions and as deep valleys captured diverging and converging south oriented flood flow channels in sequence with floodwaters on north ends of beheaded flood flow channels reversing flow direction to flow to the deeper beheading valley. For example, headward erosion of the deep southeast and northeast oriented South Platte River valley from western Nebraska beheaded south oriented flood flow channels east of the emerging Colorado Front Range. Because floodwaters were beheaded in sequence from east to west and because the flood flow channels diverged and converged reversed flood flow on newly beheaded flood flow channels could capture south oriented flood flow from yet to be beheaded flood flow channels further to the west. Such captures of yet to be beheaded floodwaters created significant north oriented drainage routes, which today form the north oriented South Platte River and tributary drainage routes on the Colorado Piedmont east of the Colorado Front Range. At least some of the captured floodwaters had been moving in south directions across what is today the Colorado Front Range.

Before the South Platte River flood flow reversal east oriented valleys eroded headward from south oriented flood flow channels on the Colorado Piedmont to capture south oriented flood flow in the emerging Colorado Front Range. These east oriented valleys eroded headward in sequence from south to north in southeast directions along southeast oriented flood flow channels and in northeast directions across southeast oriented flood flow. Headward erosion of these deep valleys also beheaded and reversed south and southeast oriented flood flow channels to create north and northwest tributary drainage routes. The South Platte River flood flow reversal on the Colorado Piedmont probably took place as these east oriented valleys were still actively eroding headward into the emerging mountain mass. At about the same time headward erosion of the deep southwest oriented Colorado River valley was capturing south oriented flood flow west of the present day east-west continental divide. Floodwaters on north ends of beheaded flood flow routes were reversed to create north and northwest oriented Colorado River drainage routes and to create the present day east-west continental divide. Today evidence for the former south oriented flood flow channels abounds in the form of through valleys or passes crossing drainage divides between east oriented drainage routes.

Detailed location map for Boulder Creek-Clear Creek drainage divide area

Fig2 detlocmap

Figure 2: Detailed location map of Boulder Creek-Clear 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 Boulder Creek-Clear Creek drainage divide area in the Colorado Front Range. Green colored areas are National Forest lands located in mountain regions. The red-brown area in the northwest quadrant of figure 2 is the south end of Rocky Mountain National Park. The east-west continental divide serves as a county line and is shown with a dashed line extending from near the southwest corner of figure 2 to the north edge of figure 2 (west half). Areas west of the continental divide drain to the Colorado River and the Pacific Ocean. Areas east of the continental divide drain to the South Platte River and eventually to the Gulf of Mexico. The Colorado River flows in a southwest direction across the northwest corner of figure 2. The South Platte River flows in a north-northeast and north direction a short distance east of figure 2. Clear Creek flows in a northeast, east, northeast and east direction from near the southwest corner of figure 2 to Idaho Springs and Golden before flowing in an east-northeast direction to the east edge of figure 2 (south half) and then joining the South Platte River east of figure 2. The West Fork Clear Creek originates near the southwest corner of figure 2 and flows in an east direction from Berthoud Falls to Empire before joining east oriented Clear Creek. Berthoud Pass is located north of Berthoud Falls and is where the north, north-northwest, and west-northwest oriented Fraser River originates. Before headward erosion of the deep southwest oriented Colorado River valley south oriented floodwaters flowed in a south direction on the Fraser River alignment to reach what at that time was the newly eroded east oriented West Fork Clear Creek valley. Headward erosion of the much deeper southwest oriented Colorado River valley beheaded and reversed that south oriented flood flow channel to create the present day Fraser River drainage route. Other Clear Creek River tributaries of interest include southeast oriented Fall Creek and North Clear Creek in addition to east and south oriented Ralston Creek, which flows through Golden Gate Canyon State Park. South Boulder Creek originates at the west end of Gilpin County and flows in a northeast direction to East Portal and then in an east direction to Eldorado Springs at the Front Range’s eastern flank. Once on the Colorado Piedmont South Boulder Creek turns to flow in a north direction on the east side of Boulder to join northeast oriented Boulder Creek, which then flows to the east edge of figure 2 (near northeast corner). North and east of figure 2 Boulder Creek joins northeast oriented St Vrain Creek, which then joins the northeast, southeast, and northeast oriented South Platte River. No named South Boulder Creek tributaries are shown in figure 2 and more detailed topographic maps are needed to observe those important drainage routes.

South Boulder Creek-North Clear Creek drainage divide area

Fig3 SBoulderNClear

Figure 3: South Boulder Creek-North Clear Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of South Boulder Creek-North Clear Creek drainage divide area. The map contour interval for figure 3 is 50 meters. The east-west continental divide is shown with a labeled dashed line extending from near the southwest corner of figure 3 along the high mountain ridge to the north edge of figure 3 (west half). Areas west of the continental divide drain to the Colorado River. Rogers Pass is located on the continental divide near the center of figure 3. South Boulder Creek originates east and north of Rogers Pass and flows in a northeast direction to East Portal and then turns to flow in an east direction to Rollinsville before turning in a northeast direction to flow to east edge of figure 3 (near northeast corner). East and north of figure 3 South Boulder Creek flows in an east direction to the east flank of the mountains and then in a north direction to join northeast oriented Boulder Creek. Colorado Mountain is a labeled high point near the center of figure 3. The southeast and south oriented stream south of Colorado Mountain is North Clear Creek, which south of figure 3 flows to east oriented Clear Creek. East of Colorado Mountain is Dakota Hill and Apex is a small town located between Colorado Mountain and Dakota Hill. The south oriented stream flowing from near Apex to North Clear Creek is Pine Creek. The north oriented South Boulder Creek tributary originating north of Apex is Jenny Lind Gulch. The gap or through valley between Colorado Mountain and Dakota Hill just north of Apex has an elevation of between 3000 and 3050 meters. Colorado Mountain and Dakota Hill both rise to more than 3300 meters suggesting the gap or through valley is at least 150 meters deep. The gap or through valley is a water-eroded landform and was eroded by south oriented flood flow moving to the actively eroding Pine Creek valley prior to headward erosion of the east oriented South Boulder Creek valley. Headward erosion of the South Boulder Creek valley beheaded and reversed the flood flow to create the north oriented Jenny Lind Gulch drainage route. Further east Missouri Creek is a south oriented North Clear Creek tributary originating near Wideawake, which is between Oregon Hill and Fairburn Mountain. North of the Missouri Creek headwaters are headwaters on northeast and north oriented Lump Gulch, which drains to South Boulder Creek near Rollinsville. The gap or through valley linking the north oriented Lump Gulch valley with the south oriented Missouri Creek valley has an elevation of between 2950 and 3000 meters. Fairburn Mountain rises to at least 3150 meters suggesting the gap is at least 150 meters deep. The Lump Gulch-Missouri Creek through valley or gap was also eroded by south oriented flood flow prior to headward erosion of the east oriented South Boulder Creek valley. These two examples illustrate evidence for multiple south oriented flood flow channels in the Colorado Front Range that were progressively captured as east oriented valleys eroded headward into the emerging Colorado Front Range from flood flow channels on the Colorado Piedmont (east of figure 3).

Detailed map of Colorado Creek-Missouri Creek drainage divide area

Fig4 detColoradoMissouri

Figure 4: Detailed map of Colorado Creek-Missouri 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 Colorado Creek-Missouri Creek drainage divide area seen in less detail in figure 5. The map contour interval for figure 4 is 40 feet. The small town of Wideawake is located near the center of figure 4. Missouri Creek flows from near Wideawake to the south center edge of figure 4. South of figure 4 Missouri Creek flows to southeast oriented North Clear Creek, which flows to east oriented Clear Creek. Colorado Creek originates a short distance east of Wideawake and flows in a north-northeast direction to join northeast oriented Lump Gulch at Snowline Lake (near the small town of Gilpin). North of figure 4 Lump Gulch drains in a north direction to join east and north oriented South Boulder Creek. A pair of through valleys or gaps near Wideawake link the north oriented Colorado Creek valley with the south oriented Missouri Creek valley. The deeper of the two through valleys or gaps has a floor elevation of between 9600 and 9640 feet. Fairburn Mountain to the east rises to 10,390 feet and Dakota Hill to the west rises to 10,929 feet suggesting the through valley or gap is approximately 750 feet deep. The other through valley or gap is approximately 80 feet shallower or about 670 feet deep. These two through valleys or gaps were eroded by diverging and converging flood flow channels prior to headward erosion of the east oriented South Boulder Creek valley to the north of figure 4. At the time the south oriented flood flow flowed to the actively eroding south oriented Missouri Creek valley elevations north of the gaps or through valleys were at least as high as the floors of those through valleys or gaps. Headward erosion of the east oriented South Boulder Creek valley and its northeast oriented tributary valleys beheaded and reversed flood flow channels in sequence from east to west and caused flood flow reversals that created north oriented tributary drainage routes and generally eroded the north side of the present day South Boulder Creek-Clear Creek drainage divide. An even deeper north-to-south oriented through valley can be seen along the east edge of figure 4 and is better seen in figures 5 and 6.

South Boulder Creek-Ralston Creek drainage divide area

Fig5 SBoulderRalston

Figure 5: South Boulder Creek-Ralston Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the South Boulder Creek-Ralston Creek drainage divide area east and slightly south of figure 3 and there is an overlap area with figure 3. The map contour interval for figure 5 is 50 meters. The east flank of the Colorado Front Range can be seen along the edge of figure 5. North Clear Creek flows in a southeast direction across the southwest corner of figure 5. Rollinsville is located near the northwest corner of figure 5. South Boulder Creek flows from the west edge of figure 5 in an east direction to Rollinsville and then in a northeast direction to the north edge of figure 5 (west half). North of figure 3 South Boulder Creek turns to flow in an east direction just north of figure 5 and can be seen crossing the north edge into figure 5 near the north center edge and northeast corner of figure 5. Fairburn Mountain is located in the west center area of figure 5 and Tremont Mountain is east of Fairburn Mountain. A deep north-to-south oriented through valley between Fairburn Mountain and Tremont Mountain links the north oriented South Beaver Creek valley with the south and southeast oriented headwaters of Ralston Creek. Ralston Creek flows in a south and southeast direction before turning in a northeast and east direction to flow to the east flank of the mountains and then turns to flow in a south-southeast direction to the east edge of figure 5 (south half). East and south of figure 5 Ralston Creek turns in an east and southeast direction to join Clear Creek, which then joins the South Platte River. The South Beaver Creek-Ralston Creek through valley has a floor elevation of between 2750 and 2800 meters. Tremont Mountain rises to more than 3100 meters and Fairburn Mountain rises to more than 3150 meters suggesting the through valley is at least 300 meters deep. South of the through valley and of the Ralston Creek headwaters area is another north-to-south oriented through valley linking the south and southeast oriented Ralston Creek headwaters valley with the south oriented Macy Gulch and south-southwest oriented Smith Gulch valleys. This second through valley has a floor elevation of between 2700 and 2750 meters. Ely Hill to the east of the through valley rises to 3062 meters suggesting this second through valley may be as much as 300 meters deep (based on the Fairburn Mountain elevation). If Fairburn Mountain is the west wall of the through valley then the through valley floor is also drained by south oriented Fourmile Gulch. A northwest-to-southeast oriented through valley between Black Hawk Mountain and Centralia Mountain links the southeast-northeast oriented Ralston Creek elbow of capture with the southeast oriented Guy Gulch valley, which drains to south edge of figure 5 and south of figure 5 to east oriented Clear Creek. This complex of diverging valleys was eroded by diverging and converging flood flow channels as deep valleys eroded headward into what at that time was the emerging mountain mass. Headward erosion of the deeper Ralston Creek valley beheaded southeast oriented flood flow to the southeast oriented Guy Gulch valley and then beheaded south oriented flood flow to the south oriented Macy Gulch valley. Subsequently South Boulder Creek valley headward erosion beheaded and reversed flood flow to the Ralston Creek valley to create the north oriented South Beaver Creek drainage route.

Detailed map of South Beaver Creek-Ralston Creek drainage divide area

Fig6 detSBeaverRalston

Figure 6: Detailed map of South Beaver Creek-Ralston 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 South Beaver Creek-Ralston Creek drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 40 feet. Lump Gulch drains in a northeast direction across the northwest corner of figure 6. North of figure 6 Lump Gulch turns to drain in a north direction to east oriented South Boulder Creek. Ellsworth Creek is the north and north-northeast oriented Lump Gulch tributary flowing from the west center edge of figure 6. Ralston Creek originates near the center of figure 6 and flows in a south and south-southeast direction to the south center edge of figure 6. South of figure 6 Ralston Creek flows in a southeast direction before turning in a northeast direction. South Beaver Creek originates in the northwest quadrant of figure 6 and flows in an east and northeast direction to the north center edge of figure 6. North of figure 6 South Beaver Creek turns to flow in a north and northwest direction to join a northeast oriented section of east oriented South Boulder Creek. The north oriented stream originating east of the Reverends Ridge Campground and flowing to the north edge of figure 6 (slightly east of center) is a South Beaver Creek tributary. Thors Lake is located on the north side of a north-to-south oriented through valley linking the north oriented South Beaver Creek valley with the south oriented Ralston Creek headwaters valley. The through valley floor elevation is between 9040 and 9080 feet. Tremont Mountain to the east rises to 10,388 feet and Fairburn Mountain to the west (just west of figure 6) rises to 10,390 feet. These elevations suggest the through valley is at least 1300 feet deep. The through valley is a water-eroded valley and was eroded by south oriented flood flow prior to headward erosion of the east oriented South Boulder Creek valley north of figure 6. Headward erosion of the South Boulder Creek valley beheaded and reversed the south oriented flood flow to create the north oriented South Beaver Creek drainage route. The reversal of flood flow on the South Beaver Creek alignment captured south oriented flood flow (moving west of the actively eroding South Boulder Creek valley head) on the Lump Gulch alignment. The captured flood flow made a U-turn in the northwest corner of figure 6 and was responsible for erosion of the east and northeast oriented South Beaver Creek headwaters valley.

Ralston Creek-Clear Creek drainage divide area

Fig7 RalstonClear

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

Figure 7 illustrates the Ralston Creek-Clear Creek drainage divide area south of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 7 is 50 meters. Clear Creek flows in an east direction near the south edge of figure 7. North Clear Creek flows in a southeast direction from the west edge of figure 7 (north half) to join Clear Creek near the Jefferson County line. Black Hawk Mountain is located near the center of figure 7. Guy Gulch originates north of Black Hawk Mountain and drains in a southeast direction to join Clear Creek in the southeast quadrant of figure 7. Ralston Creek flows in a south direction from the north edge of figure 7 (west half-between Fairburn Mountain and Tremont Mountain) and then turns in a southeast, northeast, and east direction to flow into the northeast corner of figure 7 before turning in a south-southeast direction to cross the east edge of figure 7 (north half). East of figure 7 Ralston Creek flows in an east and southeast direction to join Clear Creek, which then joins the north-northeast oriented South Platte River. A northwest-to-southeast oriented through valley north of Black Hawk Mountain links the southeast-northeast Ralston Creek elbow of capture with the southeast oriented Guy Gulch valley. The through valley floor elevation is between 2600 and 2650 meters. Black Hawk Mountain rises to 3045 meters and Mount Tom to the east rises to 2967 meters suggesting the through valley is approximately 300 meters deep. The through valley is remarkably straight suggesting it may be located along a fault line, however the through valley is also a water-eroded valley and was eroded by southeast oriented floodwaters flowing to the east oriented Clear Creek valley prior to headward erosion of the deeper northeast and east oriented Ralston Creek valley. Headward erosion of the northeast and east oriented Ralston Creek valley captured the southeast oriented flood flow and beheaded the Guy Gulch valley. Floodwaters on the northwest end of the beheaded flood flow channel reversed flow direction to create a northwest oriented Ralston Creek tributary drainage route. West of Ely Hill (which is west of Black Hawk Mountain) a shallower through valley links a northeast oriented Ralston Creek tributary valley with the south-southwest oriented Smith Hill Gulch valley, which drains to southeast oriented North Clear Creek. A north-to-south oriented through valley links the south oriented Ralston Creek headwaters valley with south-southwest oriented Smith Hill Gulch valley providing evidence headward erosion of the southeast oriented Ralston Creek valley also captured south oriented flood flow moving to the Smith Hill Gulch valley.

Detailed map of Ralston Creek-Guy Gulch drainage divide area

Fig8 detRalstonGuyGulch

Figure 8: Detailed map of Ralston Creek-Guy Gulch 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 Ralston Creek-Guy Gulch drainage divide area seen in less detail in figure 7. The map contour interval for figure 8 is 40 feet. Ralston Creek flows in a southeast direction from near the northwest corner of figure 8 into section 35 and then turns to flow in a northeast direction to the north edge of figure 8 (west half). North of figure 8 Ralston Creek turns to flow in an east and then south-southeast direction to reach the Colorado Piedmont before turning in an east direction to join Clear Creek. Guy Gulch originates in section 1 and drains in a southeast direction to the southeast corner of figure 8. South and east of figure 8 Guy Gulch drains to east oriented Clear Creek, which flows to the north oriented South Platte River. A northwest-to-southeast oriented through valley in section 1 links the southeast oriented Guy Gulch valley with the valley of a northwest oriented Ralston Creek tributary. The through valley floor elevation is between 8720 and 8760 feet. Ely Hill in section 11 to the west rises to 10,045 feet and Centralia Mountain in the southeast corner of section 31 to the east rises to 9795 feet suggesting the through valley is more than 1000 feet deep. A northeast-to-southwest oriented through valley in the south half of section 3 near the west center edge of figure 8 links a northeast oriented Ralston Creek tributary valley with the south-southwest Smith Hill Gulch valley, which west of figure 8 drains to the southeast oriented North Clear Creek valley. The Ralston Creek-Guy Gulch through valley was eroded by southeast oriented flood flow moving to the east oriented Clear Creek valley prior to headward erosion of the northeast and east oriented Ralston Creek valley. Headward erosion of the deeper northeast and east oriented Ralston Creek valley then captured the southeast oriented flood flow and floodwaters on the northwest end of the beheaded flood flow channel reversed flow direction to create the northwest oriented Ralston Creek tributary drainage route. At the same time the much deeper Ralston Creek knick point eroded headward along the captured southeast oriented flood flow channel (the present day southeast oriented Ralston Creek segment) and captured south oriented flood flow that had been moving to the Smith Hill Gulch valley (west of figure 8). The northeast-to-southwest oriented through valley in section 3 was probably eroded by a diverging and converging flood flow channel, which was also beheaded and reversed by headward erosion of the much deeper northeast and east oriented Ralston Creek valley to create a northeast oriented Ralston CReek tributary drainage route.

Van Bibber Creek-Clear Creek drainage divide area

Fig9 VanBibberClear

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

Figure 9 illustrates the Van Bibber Creek-Clear Creek drainage divide area east of figure 7 and there is an overlap area with figure 7. The map contour interval for figure 9 is 50 meters. The eastern flank of the Colorado Front Range is located west of Golden. East of the Front Range is the Colorado Piedmont. The South Platte River flows in a north-northeast direction east of figure 9. Clear Creek flows in an east direction from near the southwest corner of figure 9 to near Golden and then flows in an east-northeast direction to the east edge of figure 9 (south of center). East of figure 9 Clear Creek joins the South Platte River. Ralston Buttes are located in the northeast quadrant of figure 9 and Ralston Reservoir is south of Ralston Buttes. Ralston Creek flows in an east direction from the west edge of figure 9 (north half) toward Ralston Buttes and then turns to flow in a south-southeast direction to Ralston Reservoir. Ralston Creek flows in an east and east-southeast direction from Ralston Reservoir to the east center edge of figure 9 and joins Clear Creek east of figure 9. Van Bibber Creek originates near the west center edge of figure 9 and flows in an east, southeast, and east direction (south of Belcher Hill) and then in an east direction on the north side of North Table Mountain to join east-northeast oriented Clear Creek. North Table Mountain is an erosional residual north and east of Golden. A north-to-south oriented through valley on the west side of North Table Mountain links the east oriented Van Bibber Creek valley with the east-northeast oriented Clear Creek valley. Golden Gate Canyon is located west of North Table Mountain and is drained by east, southeast, and east-northeast oriented Tucker Gulch, which drains into the through valley and then in a southeast and south direction to Clear Creek. Crawford Gulch is a south-southeast oriented tributary to Tucker Gulch located south of Belcher Hill and is linked by a through valley with the southeast oriented Van Bibber Creek segment west of Belcher Hill. The Van Bibber Creek-Tucker Gulch through valley south of Belcher Hill has a floor elevation of between 2250 and 2300 meters while the Van Bibber Creek-Tucker Gulch through valley west of North Table Mountain has a floor elevation of between 1800 and 1850 meters and is approximately 450 meters lower in elevation. Both through valleys were eroded by south-southeast oriented flood flow moving to the actively eroding Tucker Gulch valley, which was eroding headward from the actively eroding Clear Creek valley. South-southeast oriented flood flow channels eroded the two through valleys and based on present day elevations it is difficult to explain a 450-meter elevation difference between two adjacent and parallel flood flow channels. While erosion of the through valleys may not have been simultaneous there probably was not a geologically significant time gap between the erosion of the two through valleys, which suggests the Front Range was emerging as the two through valleys were eroded. If so the elevation difference between the flood flow channels was much less at the time the through valleys were eroded than it is today.

Detailed map of Van Bibber Creek-Clear Creek drainage divide area

Fig10 detVanBibberClear

Figure 10: Detailed map of Van Bibber Creek-Clear 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 Van Bibber Creek-Clear Creek drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 10 feet. The eastern flank of the Colorado Front Range is located near the west margin of figure 10. Clear Creek flows in an east, northeast, and east-northeast direction from the south center edge of figure 10 to the east edge of figure 10 (south half) and east of figure 10 flows to the north-northeast oriented South Platte River. Tucker Gulch drains in an east, southeast, and south direction from the west edge of figure 10 (south half) to join Clear Creek at Golden. North Table Mountain is the large erosional residual located north of Clear Creek. South Table Mountain is located south of Clear Creek and is another large erosional residual. The highest elevation on North Table Mountain is 6566 feet. The highest elevation on South Table Mountain and seen in figure 10 is between 6330 and 6340 feet. Elevations on the tops of North and South Table Mountains decrease in a south and/or southeast direction. Elevations in the Clear Creek valley between North and South Table Mountains are difficult to read, but appear to be between 5600 and 5650 feet suggesting Clear Creek has eroded a 680-foot deep valley between the two erosional residuals. The north-to-south oriented through valley west of North Table Mountain links the south oriented Tucker Gulch and northeast oriented Clear Creek valleys with the east oriented Van Bibber Creek valley (north of figure 10). The through valley floor elevation at the drainage divide is between 5990 and 6000 feet, which is 660 feet lower than the highest point on North Table Mountain. The through valley on the west side of South Table Mountain is not seen in figure 10, but has a floor elevation of less than 6000 feet. The history of these valleys probably begins with diverging and converging south oriented flood flow channels along the east flank of the emerging Colorado Front Range. Initially these flood flow channels flowed on a surface at least as high as the tops of North and South Table Mountains. Headward erosion of east oriented valleys (in sequence from south to north) from these south oriented flood flow channels captured south oriented flood flow moving across the emerging mountain mass and diverted the floodwaters to south oriented flood flow channels on the Colorado Piedmont. The northeast oriented Clear Creek valley segment between North and South Table Mountains probably was initiated as a southwest oriented flood flow channel converging with a south oriented flood flow channel (on the west side of North Table Mountain) and with the east oriented Clear Creek valley flood flow channel to flow in a south direction on the west side of South Table Mountain. South oriented flood flow channels on the Colorado Piedmont were then beheaded and reversed by headward erosion of the deep southeast and northeast oriented South Platte River valley from western Nebraska (north of figure 10-see figure 1). The resulting reversal of flood flow created the north oriented South Platte River drainage route (east of figure 10) and probably reversed flood flow in the Clear Creek valley between North and South Table Mountains and ended south oriented flood flow west of South Table Mountain. Headward erosion of a deeper east oriented flood flow channel on the Van Bibber Creek alignment (north of figure 10) then beheaded the south oriented flood flow channel on the west side of North Table Mountain.

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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