Abstract:

This essay uses topographic map evidence to interpret landform origins in the Laramie River–North Fork Cache la Poudre River drainage divide area along the Wyoming-Colorado border. The Laramie River flows in a north direction between the Medicine Bow Mountains and the Colorado Laramie Mountains and then in a northeast and north direction in the Wyoming Laramie Basin before turning to flow in an east and northeast direction across the Wyoming Laramie Mountains and finally to the southeast oriented North Platte River. The North Fork Cache la Poudre River originates in the Colorado Laramie Mountains and flows in a northeast, east, and southeast direction to join the south and southeast oriented Cache la Poudre River, which then flows to the east-southeast and northeast oriented South Platte River. A northwest to southeast oriented through valley between the Colorado Laramie Mountains and the Wyoming Laramie Mountains links north oriented Laramie River tributaries with southeast and south oriented North Fork Cache la Poudre River tributaries. The through valley , drainage route and drainage divide orientations, and other landforms in the Laramie River-North Fork Cache la Poudre River drainage divide area 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 the present day Laramie River-North Fork Cache la Poudre drainage divide at a time when the Laramie Mountains and other regional mountain ranges were just beginning to emerge. At first floodwaters flowed across the emerging mountains, but as the mountains emerged floodwaters were systematically channeled into deeper and deeper south oriented flood flow channels. The Laramie Mountains and other mountain ranges emerged as ice sheet related crustal warping raised the mountain masses and as floodwaters deeply eroded surrounding regions. Headward erosion of the deep east and northeast oriented Laramie River valley across the emerging Wyoming Laramie Mountains from the deep southeast oriented North Platte River valley beheaded south oriented flood flow channels in the Laramie Basin. Floodwaters on north ends of the beheaded flood flow channels reversed flow direction to flow to the deeper east and northeast oriented Laramie River valley and to create north oriented Laramie River and tributary drainage routes and also to create the present day Laramie River-North Fork Cache la Poudre River drainage divide. The newly reversed Laramie River valley probably captured flood flow moving in a south direction west of the Medicine Bow Mountains and the captured floodwaters flowed around the south end of the Medicine Bow Mountains and in a north direction in the Laramie River valley, although that captured flood flow route ended when floodwaters west of the Medicine Bow Mountains were beheaded and reversed. Crustal warping that was raising mountain masses as floodwaters flowed across them probably aided greatly in the Laramie River flow reversal.

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 Laramie River-North Fork Cache la Poudre River drainage divide area landform origins along the Wyoming-Colorado border. 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 Laramie River-North Fork Cache la Poudre River drainage divide area landform evidence along the Wyoming-Colorado border will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Laramie River-North Fork Cache la Poudre River drainage divide area location map

Figure 1: Laramie River-North Fork Cache la Poudre 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 Laramie River-North Fork Cache la Poudre River drainage divide area along the Wyoming-Colorado border and in the south half illustrates a region in northern Colorado with the southeast corner of Wyoming to the north and western Nebraska in the northeast corner. The South Platte River flows in a north and northeast direction from the south center edge of figure 1 to Greeley, Colorado and then in an east-southeast, east, and northeast direction to the east edge of figure 1 (south half).  The North Platte River flows in a southeast direction across the northeast corner of figure 1 and east of figure 1 joins the South Platte River to form the Nebraska Platte River. The Laramie Mountains are the north to south oriented mountain range immediately east of Laramie, Wyoming and extend in a south direction into Colorado where the Laramie Mountains become the Front Range. The Medicine Bow Mountains extend in a north-northwest to south-southeast direction from the northwest corner of figure 1 to near Rocky Mountain National Park in Colorado. The region in Wyoming between the Medicine Bow Mountains and the Laramie Mountains is known as the Laramie Basin. The Laramie River originates north of Rocky Mountain National Park and flows in a north and northeast direction to Laramie, Wyoming and then in a north direction to the north edge of figure 1. North of figure 1 the Laramie River turns to flow in an east and northeast direction across the Laramie Mountains and then to the southeast oriented North Platte River. The Cache la Poudre River originates in northern Rocky Mountain National Park (near the Laramie River headwaters) and flows in a north, east, and southeast direction to join the South Platte River near Greeley, Colorado. The North Fork Cache la Poudre River is shown, but is not labeled in figure 1 and flows in an east direction just south of the Wyoming-Colorado border to Halligan Reservoir and then in a south direction to join the Cache la Poudre River. The unlabeled south oriented tributary originating in Wyoming and joining the North Fork Cache la Poudre River at Halligan Reservoir is Dale Creek. The unlabeled north oriented stream originating just west of the North Fork Cache la Poudre River headwaters and joining the Laramie River in Wyoming is Sand Creek. The Laramie River-North Fork Cache la Poudre River drainage divide area investigated in this essay is primarily located north of the east oriented North Fork Cache la Poudre River segment, east of Sand Creek, and west of Dale Creek.

The Laramie River, North Fork Cache la Poudre River, and tributary drainage routes developed during immense melt water floods from the western margin of a thick North American ice sheet. Floodwaters flowed from western Canada to and across Wyoming and Colorado at a time when the Laramie Mountains and other regional mountain ranges were just beginning to emerge. The Laramie Mountains and other mountain ranges emerged as floodwaters flowed across them and deeply eroded surrounding regions and as ice sheet related crustal warping raised mountain masses and entire regions of the continent. At first floodwaters flowed in diverging and converging south oriented flood flow channels along and across the emerging Laramie Mountains and other mountain ranges, but were diverted in other directions by headward erosion of deeper valleys. Some floodwaters west of the Laramie Mountains flowed in east directions across the emerging mountain mass to reach deep east oriented valleys eroding headward into Nebraska, although significant flood flow west of the Laramie Mountains moved in south direction to deep south oriented valleys on either side of the emerging Front Range. Floodwaters flowing to the west side of emerging Front Range moved on the present day north oriented Laramie River alignment to the actively eroding southwest oriented Colorado River valley. Floodwaters flowing to the east side of the emerging Front Range flowed to south oriented flood flow channels on the alignment of the present day north oriented South Platte River (south of Greeley) and south oriented Cache la Poudre River and tributary valleys eroded headward from those flood flow channels. The south oriented floodwaters east of the Front Range at one time flowed to the southeast oriented Arkansas River valley, although earlier floodwaters had flowed to actively eroding valley systems further to the south. The south oriented flood flow channels east of the emerging Front Range were first beheaded by headward erosion of the deep east-southeast and northeast oriented South Platte River valley. Floodwaters on north ends of beheaded flood flow channels reversed flow direction to create the present day north oriented South Platte River drainage route and parallel north oriented South Platte River tributary drainage routes. This massive reversal of flood flow was probably greatly aided by crustal warping that was raising large areas of Colorado. A similar reversal of flood flow occurred in the Laramie Basin when headward erosion of deep east and northeast oriented valleys eroded headward across the emerging Laramie Mountains from the deep North Platte River valley and beheaded south oriented flood flow channels in the Laramie Basin. Floodwaters on north ends of beheaded flood flow channels reversed flow direction to create the north oriented Laramie River and tributary drainage routes and to create the Laramie River-North Fork Cache la Poudre River drainage divide. The Laramie Basin flood flow reversal was also aided by crustal warping that was raising the Laramie Mountains as floodwaters flowed across them.

Detailed location map for Laramie River-North Fork Cache la Poudre River drainage divide area

Figure 2: Detailed location map Laramie River-North Fork Cache la Poudre 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 Laramie River-North Fork Cache la Poudre River drainage divide area along the Wyoming-Colorado border. The Wyoming-Colorado border extends in a west to east direction across figure 2 (south of center). Green colored areas are National Forest lands, which in this region are usually located in mountainous regions. The Laramie River flows in north-northwest direction across the southwest corner of figure 2 and then flows in an east and northeast direction from the west edge of figure 2 (north half) to the city of Laramie. North of Laramie the Laramie River flows in a north direction before turning to flow in an east and northeast direction across the Laramie Mountains and then to the southeast oriented North Platte River.  The north-northwest oriented Laramie River segment is located in the Colorado Laramie Mountains while the northeast oriented Laramie River segment to the north is located in the Laramie Basin. Sand Creek originates in the Laramie Colorado Mountains and flows in a north-northeast direction to join the northeast oriented Laramie River in the Laramie Basin. Other named north oriented Laramie River tributaries seen in figure 2 include Antelope Creek, Lone Tree Creek, Willow Creek, and Hermosa Creek. The North Fork Cache la Poudre River originates in the Colorado Laramie Mountains (near the Sand Creek headwaters) and flows in an east-northeast and east direction to Halligan Reservoir and then a southeast and south direction to the south edge of figure 2 (east of center). South of figure 2 the North Fork Cache la Poudre River joins the south and southeast oriented Cache la Poudre River, which flows to the east-southeast, east, and northeast oriented South Platte River. Named tributaries to the North Fork Cache la Poudre River seen in figure 2 include northeast, east, and southeast oriented Sheep Creek, east-northeast and southeast oriented Trail Creek, southeast oriented Fish Creek, and south oriented Dale Creek. Dale Creek is interesting because it originates in the Wyoming Laramie Mountains. Today the South Platte River drainage basin is a north oriented drainage basin yet many of the northern Colorado streams seen in figure 2 are oriented in south directions. These south oriented drainage routes are relics of south oriented flood flow channels that once crossed the region and which were in the process of capturing east oriented flood flow channels in southeast Wyoming (flowing across what were at that time the emerging Wyoming Laramie Mountains to deep valley eroding headward into western Nebraska). The east oriented flood flow ended because of uplift in the Wyoming Laramie Mountains and/or because of the massive flood flow reversal in the Laramie Basin. South oriented drainage routes east of the Colorado Laramie Mountains and east oriented drainage routes east of the Wyoming Laramie Mountains preserve routes of flood flow channels at the time flood flow across those regions ended. North oriented drainage routes south of the northeast oriented Laramie River segment in the Laramie Basin probably reflect drainage routes established when south oriented flood flow channels in the Laramie Basin were beheaded and reversed.

Willow Creek-Dale Creek drainage divide area

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

Figure 3 provides a topographic map of Willow Creek-Dale Creek drainage divide area. The map contour interval for figure 3 is 20 meters. The Wyoming Laramie Mountains are located in the east half of figure 3. Boulder Ridge is the high area in the southwest corner of figure 3 and the southeast end of the Laramie Basin is located between Boulder Ridge and the Wyoming Laramie Mountains. Willow Creek is the north, northwest, north, and northwest oriented stream flowing from the south edge of figure 3 (west of center) to the northwest corner of figure 3. North of figure 3 Willow Creek joins north oriented Fivemile Creek, which then joins the northeast and north oriented Laramie River. Grant Creek is a northwest oriented Willow Creek tributary on the west side of the highway near Tie Siding (a small town in the south center area of figure 3). Harney Creek is the north-northwest oriented stream on the east side of the highway near Red Buttes (near northwest corner of figure 3) and north of figure 3 flows in a north direction to join the north oriented Laramie River. Dry Creek is a northwest oriented Harney Creek tributary north of Tie Siding. Dale Creek originates a short distance north of figure 3 in the Wyoming Laramie Mountains and flows across the north edge of figure 3 (just west of the highway in the northeast quadrant of figure 3). From the small lake near the north edge of figure 3 Dale Creek flows in a south and southeast direction to the south edge of figure 3 (near southeast corner). South of figure 3 Dale Creek flows in a southeast and south direction into Colorado to join the southeast oriented North Fork Cache la Poudre River at Halligan Reservoir. Remember the North Fork Cache la Poudre River flows to the south and southeast oriented Cache la Poudre River. The southeast oriented stream originating just north of the south edge of figure 3 and east of the highway near Tie Siding flows to the West Fork Dale Creek (south of figure 3), which then flows to Dale Creek. In other words the highway crosses the Laramie River-North Fork Cache la Poudre River drainage divide between Tie Siding and the south edge of figure 3. Elevations where the highway crosses the drainage divide are between 2440 and 2460 meters. Elevations on the same drainage divide near the north edge of figure 3 (west of Dale Creek) exceed 2640 meters and elevations on Boulder Ridge near the south edge of figure 3 also exceed 2640. These elevations suggest there is a 180-meter deep or deeper through valley in the Tie Siding area linking the north oriented Laramie River valley with the south and southeast oriented Cache la Poudre River valley. At least to some extent this large through valley is a water-eroded feature and was eroded by south-southeast oriented flood flow moving from the present day north oriented Laramie River alignment to a south oriented flood flow channel on the present day north oriented South Platte River alignment (south of where the Cache la Poudre River joins the South Platte River near Greeley, Colorado-see figure 1). Flood flow on the present day north oriented South Platte River alignment was beheaded and reversed by headward erosion of the deeper east-southeast, east, and northeast oriented South Platte River valley. Flood flow in the Laramie Basin was beheaded by headward erosion of the deeper east and northeast oriented Laramie River valley across the Laramie Mountains.

Detailed map of Grant Creek-Dale Creek drainage divide area

Figure 4: Detailed map of Grant Creek-Dale 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 Grant Creek-Dale Creek drainage divide area just south of figure 3 and seen in less detail in figures 3 and 5. The map contour interval for figure 4 is 40 feet except near the west margin where the contour interval is 20 feet. Willow Creek flows in a north-northeast and north-northwest direction from the west edge of figure 4 (south half) to the west edge of figure 4 (north of center) and then flows in a north direction just west of figure 4. North of figure 4 Willow Creek flows to north oriented Fivemile Creek, which then flows to the northeast and north oriented Laramie River. A northwest to southeast oriented highway extends from near the northwest corner of figure 4 to the south edge of figure 4 (slightly east of center). Tie Siding is a small town located on that highway. Grant Creek originates in the north half of section 33 (near south center edge of figure 4) and flows in a northwest direction along and across the highway to Tie Siding and then to the west edge of figure 4 (north half) and joins Willow Creek just west of figure 4. The south oriented stream originating in the south half of section 33 is a tributary to southeast oriented Fish Creek, which flows to south oriented Dale Creek, which then flows to the southeast oriented North Fork Cache la Poudre River. The Beacon where the highway crosses the drainage divide in section 33 has an elevation of 8106 feet, but is not located at the lowest point on the drainage divide. Dale Creek flows in a southeast and south-southeast direction from the north edge of figure 4 (east half) to the east center edge of figure 4 and east and south of figure 4 flows in a southeast and south direction to join the southeast oriented North Fork Cache la Poudre River. Johnson Creek is an east oriented Dale Creek tributary originating near the west edge of section 34 and flowing to the east edge of figure 4 (south half). Woodard Creek is an east oriented Dale Creek tributary originating in section 27 and is located north of Johnson Creek. Still further north is an unnamed Dale Creek tributary. West of Tie Siding is a small town of Hermosa located on the railroad. The railroad crosses the Grant Creek-Dale Creek drainage divide near Hermosa at a point where elevations are between 8000 and 8040 feet. While not seen in figure 4 elevations on the Willow Creek-Dale Creek drainage divide rise to more than 9720 feet to the north of figure 4. Also, while not seen in figure 4, elevations on the Willow Creek-Fish Creek drainage south and west of figure 4 exceed 8700 feet. These elevations suggest the large through valley seen in figure 4 is almost 700 feet deep. This broad through valley is at least to some extent a water-eroded valley and was eroded by immense volumes of south-southeast oriented flood flow prior to the massive flood flow reversal in the Laramie Basin to the north.

Willow Creek-Fish Creek drainage divide area

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

Figure 5 illustrates the Willow Creek-Fish 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. The west to east oriented Wyoming-Colorado state line is located just south of the south edge of figure 5. Dale Creek flows in south and southeast direction from the north edge of figure 5 (near northeast corner) to the east edge of figure 5 (north of center) and east and south of figure 5 flows in a southeast and south direction to join the southeast oriented North Fork Cache la Poudre River. Boulder Ridge is the prominent ridge in the west half of figure 5. Fish Creek originates on Boulder Ridge and flows in an east and southeast direction to the south edge of figure 5 (east half). South of figure 5 Fish Creek flows in a southeast direction to join south oriented Dale Creek, which then flows to the southeast oriented North Fork Cache la Poudre River. Willow Creek originates in the south center area of figure 5, east of Boulder Ridge and north of Fish Creek, and flows in a north-northeast, north, northwest, and north direction to the north edge of figure 5 (west of center). North of figure 5 Willow Creek flows to north oriented Fivemile Creek, which then flows to the northeast and north oriented Laramie River. Lone Tree Creek originates on the west side of Boulder Ridge and flows in a north-northwest and north-northeast direction to the north edge of figure 5 (west half). North of figure 5 Lone Tree Creek flows to north oriented Fivemile Creek, which then flows to the northeast and north oriented Laramie River. The Willow Creek-Fish Creek drainage divide just east of Boulder Ridge is remarkable because it is almost the same elevation (between 2420 and 2440 meters) as the Grant Creek-Dale Creek drainage divide elevation further to the east and because near Boulder Ridge the two streams are flowing almost parallel to each other in shallow valleys. The size of the northwest to southeast oriented through valley located east of Boulder Ridge is remarkable. While Boulder Ridge appears to be an uplifted block the large through valley is at least to some extent a water-eroded valley and was eroded by southeast and south-southeast oriented flood flow moving from the present day Laramie Basin to south oriented flood flow channels on the east side of the Laramie Mountains and Front Range. The large valley west of Boulder Ridge is drained (west of figure 5) by north-northeast oriented Sand Creek (seen in figures 7, 8, 9,  and 10), which flows to the northeast and north oriented Laramie River. The north and northeast oriented Laramie River valley is located west of the north-northeast oriented Sand Creek valley (see figures 1,2, and 9).

Detailed map of Willow Creek-Fish Creek drainage divide area

Figure 6: Detailed map of Willow Creek-Fish 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 Willow Creek-Fish Creek drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 20 feet. Boulder Ridge is the upland located in the west half of figure 6. Fish Creek flows from the west edge of figure 6 (south of center) in an east-southeast, east, and southeast direction to the east edge of figure 6 (near southeast corner). South and east of figure 6 Fish Creek flows to south oriented Dale Creek, which flows to the southeast oriented North Fork Cache la Poudre River, which flows to the south and southeast oriented Cache la Poudre River. Little Fish Creek originates near the west center edge of figure 6 and flows in an east and south-southeast direction to join east oriented Fish Creek in section 10. Willow Creek originates in sections 10 and 3 along the east edge of Boulder Ridge and just north of Fish Creek and  flows in a northeast and north-northeast direction to the north edge of figure 6 (east of center). North of figure 6 Willow Creek flows in a north, northwest, and north direction to join north oriented Fivemile Creek, which flows to the northeast and north oriented Laramie River. Boulder Creek originates on Boulder Ridge just north of the Little Fish Creek headwaters and flows in an east direction to the base of Boulder Ridge and then turns to flow in a north-northeast direction to the north edge of figure 6. North of figure 6 Boulder Creek flows to north oriented Willow Creek. A low point on the Willow Creek-Fish Creek drainage divide in sections 11 has an elevation of 7970 feet. Elevations on the drainage divide near the northeast corner of figure 6 rise to more than 8100 feet suggesting there is a 130-foot deep or deeper north to south oriented through valley in sections 11 and 12 linking the north-northeast oriented Willow Creek valley with the southeast oriented Fish Creek valley. The through valley is a water-eroded feature and was eroded by south oriented flood flow moving to the southeast oriented Fish Creek valley. Flood flow across the drainage divide ended when flood flow in the Laramie Basin was beheaded and reversed to create the north oriented Laramie River and Willow Creek drainage routes. What is intriguing about the Willow Creek-Fish Creek drainage divide is that Willow Creek headwaters originate in section 10 near the point where Little Fish Creek joins Fish Creek. This evidence suggests the north oriented Willow Creek valley was eroded by floodwaters coming from Boulder Ridge. Apparently the flood flow reversal that reversed flood flow on the Willow Creek alignment did not reverse flood flow crossing the much higher Boulder Ridge, which suggests valleys were eroded in sequence from east to west and also that flood flow channels were beheaded and reversed in sequence from east to west. While this concept requires massive quantities of floodwaters and very deep erosion and is contrary to what most geologists have been taught the evidence is difficult to explain in other ways.

Sand Creek-Sheep Creek drainage divide area

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

Figure 7 illustrates the Sand Creek-Sheep Creek drainage divide area south and west of figure 5 and includes an overlap area with figure 5. The Wyoming-Colorado border extends in a west to east direction across the north half of figure 7. The map contour interval for figure 7 is 50 meters in Colorado and 20 meters in Wyoming. Boulder Ridge extends in a northeast direction from the southwest quadrant of figure 7 to the north edge of figure 7 (east half). Fish Creek flows in an east direction from Boulder Ridge to the east edge of figure 7 (near northeast corner). East of figure 7 Fish Creek flows in a southeast direction to join south oriented Dale Creek, which flows to the southeast oriented North Fork Cache la Poudre River. The North Fork Cache la Poudre River flows in a northeast and east direction across the southeast corner of figure 7 and east of figure 7 turns to flow in a southeast direction to join the south and southeast oriented Cache la Poudre River. Green Mountain is a southwest to northeast oriented ridge east of the center of figure 7. Trail Creek flows in a northeast direction from north of Green Mountain before turning in a south-southeast and east direction to the east center edge of figure 7. East of figure 7 Trail Creek flows in a southeast direction to join the east and southeast oriented North Fork Cache la Poudre River. Most Trail Creek tributaries seen in figure 7 are oriented in southeast and south directions. Sheep Creek flows in a north and northeast direction from the south edge of figure 7 (west half) to Eaton Reservoir and then in an east and southeast direction to join the North Fork Cache la Poudre River near the southeast corner of figure 7. Sand Creek flows in a north and north-northeast direction along the northwest side of Boulder Ridge before turning in a northwest direction to near Chimney Rock and then flowing in a north-northeast direction to the north edge of figure 7. North of figure 7 Sand Creek flows to the northeast and north oriented Laramie River. North oriented streams west of Sand Creek are Laramie River tributaries. Sheep Creek and Sand Creek are intriguing because Sheep Creek originates near the north oriented Sand Creek valley (just south of figure 7 and seen in detail in figure 8) and then the two streams flow parallel to each other, although at very different elevations, before Sheep Creek turns to flow to the south oriented Cache la Poudre River drainage basin while Sand Creek continues in a north direction to reach the north oriented Laramie River drainage basin. A northeast oriented Sand Creek tributary flows from near the southwest corner of figure 7 to join north and north-northeast oriented Sand Creek and is located in a deep north-northeast oriented valley, which is seen in detail in figures 9 and 10. The northeast oriented Sheep Creek headwaters and tributaries seen in figure 7 probably are flowing in strike valleys, which were eroded initially by southwest oriented flood flow moving to a deeper south oriented flood flow channel west of figure 7. Headward erosion of the east and southeast oriented Sheep Creek valley beheaded and reversed the southwest oriented flood flow to create the present day northeast oriented Sheep Creek headwaters drainage route and the northeast oriented Sheep Creek tributary drainage routes. The north-northeast oriented Sand Creek tributary valley in the southwest corner of figure 7 was likewise eroded by south-southwest oriented flood flow to a deeper south oriented flood flow channel west of figure 7, but flood flow in that valley was beheaded and reversed by the massive reversal of flood flow in the Laramie Basin that created the present day north oriented Laramie River drainage system.

Detailed map of Sand Creek-Sheep Creek drainage divide area

Figure 8: Detailed map of Sand Creek-Sheep 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 Sand Creek-Sheep Creek drainage divide area seen in less detail in figure 7. The map contour interval for figure 8 is 40 feet. Sand Creek flows in a north direction from the south edge of figure 8 (west of center) to the north edge of figure 8 (west of center). North of figure 8 Sand Creek flows in a north direction to join the north oriented Laramie River. A north-northeast oriented Sand Creek tributary flows on the floor of a deep north-northeast oriented valley from the west edge of figure 8 (south half) to join Sand Creek near the north edge of figure 8. Sheep Creek originates in section 23 and flows in a north, northeast, and east direction to the east edge of figure 8. East of figure 8 Sheep Creek flows in a northeast, east, and southeast direction to join the east and southeast oriented North Fork Cache la Poudre River, which then flows to the south and southeast oriented Cache la Poudre River. An irrigation ditch in section 23 links the north oriented Sand Creek valley with the northeast oriented Sheep Creek headwaters valley and is located in a through valley linking the two valleys. The through valley is only defined by one or two contour lines on the north side and appears minor compared to the much deeper north-northeast oriented Sand Creek tributary valley just to the west. But the through valley provides evidence of what were probably diverging north oriented drainage routes, with one of the north oriented drainage routes flowing into the deep north-northeast oriented valley and to a north oriented drainage basin while the other diverging drainage route flowed in a northeast direction before turning to flow in a southeast direction to join a south oriented drainage basin. These two drainage routes diverged on what is today the east wall of a deep north-northeast oriented valley. Cow Creek is the northwest and northeast oriented stream seen near the east center edge of figure 8 and east and north of figure 8 flows to northeast, east, and southeast oriented Sheep Creek. Drainage routes in figure 8 probably originated as south-southwest oriented flood flow channels at a time when the Laramie Mountains were emerging. Floodwaters flowed in south-southwest directions to the present day north oriented Laramie River valley and then to actively eroding south oriented valleys in the present day Laramie River headwaters area including the southwest oriented Colorado River valley. Diverging and converging south-southwest oriented flood flow channels on the Laramie Mountain upland region in the east half of figure 8 were beheaded and reversed by headward erosion of the east and southeast oriented Sheep Creek valley (north and east of figure 8-see figure 7), although the east and southeast oriented Sheep Creek valley was not deep enough to behead and reverse south-southwest oriented flow in the present day deep north-northeast oriented valley now draining to Sand Creek. Flood flow in that deeper valley was beheaded and reversed by the reversal of flood flow in the Laramie Basin that created the north oriented Laramie River drainage system. The reversal of flood flow in the deeper valley combined with Laramie Mountains uplift resulted in the capture of the north oriented Sand Creek headwaters.

Sand Creek-Laramie River drainage divide area

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

Figure 9 illustrates the Sand Creek-Laramie River 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 50 meters. The Laramie River flows in a north-northwest direction from the south edge of figure 9 to the northwest corner of figure 9. North of figure 9 the Laramie River turns to flow in a north, northeast, and north direction in the Laramie Basin before turning in an east and northeast direction to flow across the Wyoming Laramie Mountains and then to join the southeast oriented North Platte River. South of figure 9 the north oriented Laramie River valley is linked by through valleys (or passes) with the west and northwest oriented Michigan River, which flows to the north oriented North Platte River headwaters and is also linked with the Cache la Poudre River and Colorado River valleys. The Medicine Bow Mountains are located west of the Laramie River valley in figure 9 and the Colorado Laramie Mountains are located east of the Laramie River valley. Sand Creek flows in a north and north-northeast direction across the Colorado Laramie Mountains from the south edge of figure 9 (east of center) and then in a north and northeast direction to enter the deep north-northeast oriented valley located east of Bull Mountain to the north edge of figure 9 (near northeast corner). North of figure 9 Sand Creek flows in a north direction to join the northeast and north oriented Laramie River. Sand Creek Pass is located near the center of figure 9 and links the deep north-northeast oriented Sand Creek valley with the deeper north-northwest oriented Laramie River valley. Sand Creek Pass has an elevation of 2736 meters. Bull Mountain to the west rises to 3073 meters and Little Bald Mountain to the east rises to 3179 meters suggesting Sand Creek Pass is at least 330 meters deep. Sand Creek is a water-eroded valley and was initially eroded by a southwest oriented flood flow channel that converged south of Bull Mountain with a south-southeast oriented flood flow channel on the present day north-northwest oriented Laramie River alignment. South oriented flood flow on the Sand Creek and Laramie River alignments was subsequently reversed to create the present day north oriented drainage routes. Crustal warping that raised regions to the south and headward erosion of the deep east and northeast oriented Laramie River valley across the emerging Wyoming Laramie Mountains that beheaded and reversed south oriented flood flow channels in the Laramie Basin were responsible for the flood flow reversal. Probably the reversal of flood flow in the Laramie River valley captured flood flow still moving in a south direction on the west side of the Medicine Bow Mountains. The captured floodwaters moved in a southeast and east direction on the present day west and northwest oriented Michigan River alignment to the newly reversed Laramie River valley (and also to the Cache la Poudre River valley) and then in a north direction into the Laramie Basin. Subsequently flood flow west of the Medicine Bow Mountains was beheaded and reversed to create the north oriented North Platte River west and northwest oriented Michigan River drainage routes.

Detailed map of Sand Creek-Laramie River drainage divide area

Figure 10: Detailed map of Sand Creek-Laramie River 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 Sand Creek-Laramie River drainage divide area seen is less detail in figure 9. The map contour interval for figure 10 is 40 feet. The Colorado Laramie Mountains are located in southeast quadrant of figure 10. The south end of Bull Mountain is the upland region seen in section 19. The Laramie River flows in a north and northwest direction across the southwest corner of figure 10. West and north of figure 10 the Laramie River flows in a north-northwest, north, northeast, and north direction into and across the Laramie Basin before turning in an east and northeast direction to flow across the Wyoming Laramie Mountains and then to the southeast oriented North Platte River. Sand Creek flows in a northeast direction across the southeast corner of figure 10 and east of figure 10 turns to flow in a north direction to enter the Laramie Basin and to join the northeast and north oriented Laramie River. Sand Creek Pass is located in the north half of section 29 and has an elevation of 8976 feet. Jimmy Creek originates on the southwest side of Sand Creek Pass and flows in southwest direction into section 36 where it turns to flow in an east direction into section 35 where it turns again to flow in a northwest direction to the west edge of figure 10. West of figure 10 Jimmy Creek joins the north-northwest oriented Laramie River. A northeast oriented Sand Creek tributary originates in section 29 south of Sand Creek Pass and flows to the northeast corner of figure 10 and north and east of figure 10 joins north oriented Sand Creek. Bull Mountain achieves an elevation just north of figure 10 of 10,082 feet. Elevations in the Colorado Laramie Mountains in the southeast corner of section 32 exceed 10,240 feet. These elevations suggest Sand Creek Pass is at least 1100 feet deep. Sand Creek Pass is a water-eroded through valley and was eroded by a southwest oriented flood flow channel that converged with a south-southeast oriented flood flow channel on the present day north-northwest oriented Laramie River alignment. The south oriented flood flow was beheaded and reversed by headward erosion of the much deeper east and northeast oriented Laramie River valley across the Wyoming Laramie Mountains, which diverted flood flow to the much deeper southeast oriented North Platte River valley. The reversal of flood flow in the Laramie River valley probably captured flood flow still moving in a south direction on the west side of the Medicine Bow Mountains (west of figure 10) and the captured flood flow moved around the south end of the Medicine Bow Mountains to reach the newly reversed Laramie River drainage route. The Laramie River valley floor elevation near the southwest corner of figure 10 is less than 8020 feet suggesting there was almost 900 feet of erosion in the Laramie River valley after the reversal of flood flow, suggesting significant captured floodwaters flowed in a north direction, although some the elevation difference could be the result of crustal warping.

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.