Abstract:

This essay uses topographic map evidence to interpret landform origins in the French Creek-Douglas Creek drainage divide area in the Wyoming Medicine Bow Mountains. The North Platte River flows in a north-northwest direction on the west side of the north to south oriented Medicine Bow Mountains. South French Creek is a south and southwest oriented stream originating high in the Medicine Bow Mountains and flowing to southwest oriented French Creek, which the flows to the north-northwest oriented North Platte River as a barbed tributary. Douglas Creek originates south of the south oriented South French Creek headwaters and flows in a south and southwest direction before turning (at the point where it is joined by west and northwest oriented Pelton Creek) to flow in a northwest direction to the north-northwest oriented North Platte River. Drainage routes in the French Creek-Douglas Creek divide area are predominantly oriented in south directions and join the north-northwest oriented North Platte River or the northwest oriented Douglas Creek segment and Pelton Creek segment as barbed tributaries. The Laramie River and its north and northeast oriented Little Laramie River tributary flow in north and northeast directions on the east side of the Medicine Bow Mountains and are also joined by south oriented tributaries originating near the Douglas Creek and French Creek headwaters. The predominantly south oriented drainage routes draining a high mountain region drained on both side by north oriented drainage systems is interpreted in the context of immense south oriented floods at a time when the Medicine Bow Mountains were just beginning to emerge. Floodwaters were derived from the western margin of thick North American ice sheet and flowed from western Canada to and across the Medicine Bow Mountains region. The Medicine Bow Mountains emerged as floodwaters deeply eroded surrounding valleys and basins and as ice sheet crustal warping raised the mountain range and the entire region. At first south oriented floodwaters flowed across the emerging mountain range including crossing what are today the highest regions in the Wyoming Medicine Bow Mountains (which are located in the Snowy Range), however as the Medicine Bow Mountains emerged floodwaters were channeled to deeper south oriented flood flow channels on either side on the alignments of the present day north oriented North Platte River and Laramie River (and its Little Laramie River tributary). Headward erosion of much deeper valleys north of the study area beheaded and reversed the deep south oriented flood flow channels on either side of the emerging Medicine Bow Mountains to create the north oriented Laramie River (and Little Laramie River) and North Platte River drainage routes. The Laramie River and North Platte River drainage reversals were greatly aided by crustal warping that was raising the Medicine Bow Mountains and the entire region.

Preface

The following interpretation of detailed topographic map evidence is one of a series of essays describing similar evidence for all major drainage divides contained within the Missouri River drainage basin and for all major drainage divides with adjacent drainage basins. The research project is interpreting evidence in the context of a previously unexplored deep glacial erosion paradigm, which is fundamentally different from most commonly accepted North American glacial history interpretations. Project essays are listed on the sidebar category list under their appropriate Missouri River tributary drainage basin, Missouri River segment drainage basin (by state), and/or state in which the Missouri River drainage basin is located.

Introduction

The purpose of this essay is to use topographic map interpretation methods to explore the French Creek-Douglas Creek drainage divide area landform origins in the Wyoming Medicine Bow 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 French Creek-Douglas Creek drainage divide area landform evidence in the Wyoming Medicine Bow Mountains will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

French Creek-Douglas Creek drainage divide area location map

Figure 1: French Creek-Douglas 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 French Creek-Douglas Creek drainage divide area in the Wyoming Medicine Bow Mountains and illustrates a region in southern Wyoming with a region in northern Colorado to the south of Wyoming. Rocky Mountain National Park is located near the south edge of figure 1 and the Medicine Bow Mountains extend in a north-northwest direction from the northwest corner of Rocky Mountain National Park into southern Wyoming. The North Platte River is formed near Coalmont (west of Rocky Mountain National Park) at the confluence of tributaries and then flows in a north and north-northwest direction to the north edge of figure 1 (west half). North of figure 1 the North Platte River flows in a north direction into central Wyoming where it flows around the northwest end of the Laramie Mountains and then turns to flow in a southeast direction into Nebraska. Douglas Creek is the unlabeled south and northwest oriented North Platte River tributary north of the state line in the Medicine Bow Mountains. French Creek is not shown in figure 1, but originates near the Douglas Creek headwaters (south of Medicine Bow Peak) and flows in a southwest direction to join the north-northwest oriented North Platte River as a barbed tributary. The Laramie River originates just east of Clarks Peak (north of Rocky Mountain National Park) and flows in a north and north-northwest direction into Wyoming where it turns to flow in a northeast direction to Laramie. From Laramie the Laramie River flows in a north and northeast direction to the north edge of figure 1 (east of center). North of figure 1 the Laramie River flows in a northeast direction to join the southeast oriented North Platte River. The unlabeled southeast and northeast oriented stream shown in figure 1 originating near the Douglas Creek headwaters (south of Medicine Bow Peak) and joining the Laramie River south of Bosler is the Little Laramie River (southeast oriented segment is the Middle Fork Little Laramie River). The French Creek-Douglas Creek drainage divide area in the Wyoming Medicine Bow Mountains investigated in this essay is located north of the Wyoming-Colorado state line, south of French Creek, east of the North Platte River, and generally west of the North Platte River-Laramie River drainage divide.

The Medicine Bow Mountains are today a high mountain range standing above the surrounding region, however at the time drainage routes were developed the Medicine Bow Mountains were just beginning to emerge. At that time immense melt water floods flowed from western Canada to and across the region seen in figure 1. Floodwaters were derived from the western margin of a thick North American ice sheet and initially were flowing in south directions across what are today high mountain ranges, including the Medicine Bow Mountains. The present day north oriented North Platte River and Laramie River drainage routes originated as south oriented flood flow channels on either side of the emerging Medicine Bow Mountains. The south oriented Douglas Creek headwaters route, which today is located in the high Medicine Bow Mountains, was eroded by a south oriented flood flow channel that converged with a southeast oriented flood flow channel on the present day northwest oriented Douglas Creek drainage route. The southeast oriented flood flow channel diverged from the south oriented flood flow channel on the present day north oriented North Platte River alignment and crossed the emerging Medicine Bow Mountains to reach the south oriented flood flow channel on the present day north oriented Laramie River alignment. The Medicine Bow Mountains emerged as floodwaters deeply eroded surrounding valleys and basins and as ice sheet related crustal warping raised the Medicine Bow Mountains and the entire region. Headward erosion of the deep southeast oriented North Platte River valley north and east of the emerging Laramie Mountains (and north and east of figure 1) beheaded south oriented flood flow channels supplying floodwaters to the region seen in figure 1. Flood flow channels were beheaded in sequence from east to west. Floodwaters on north ends of beheaded flood flow channels reversed flow direction to create north oriented drainage routes. South oriented flood flow on the Laramie River alignment was beheaded and reversed before south oriented flood flow on the North Platte River alignment was beheaded and reversed. Reversed flood flow on the Laramie River alignment captured south oriented flood flow from the North Platte River alignment and for a time floodwaters made a large U-turn around the south end of the emerging Medicine Bow Mountains near the northwest corner of Rocky Mountain National Park. Uplift of the Medicine Bow Mountains and of the entire region eventually ended all south oriented flood flow to the region.

Detailed location map for French Creek-Douglas Creek drainage divide area

Figure 2: Detailed location map French Creek-Douglas 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 French Creek-Douglas Creek drainage divide area in the Wyoming Medicine Bow Mountains. The west to east oriented Wyoming-Colorado state line extends across figure 2 near the south edge of figure 2. Green colored areas are National Forest lands, which in this region are usually located in mountainous areas. The Medicine Bow Mountains extend in a north to south direction from the north edge of figure 2 to the south edge of figure 2. The North Platte River flows in a north-northwest direction from near the south center edge of figure 2 to the northwest corner of figure 2. North of figure 2 the North Platte River flows in a north direction into central Wyoming where it flows around the northwest end of the Laramie Range and then flows in a southeast direction into Nebraska. Mountain Home is a town near the state line and east of the south center edge of figure 2. Pelton Creek flows in a west and northwest direction from Mountain Home to join Douglas Creek, which then flows in a northwest direction to join the North Platte River (south of the Savage Run Wilderness). Douglas Creek originates near the center of figure 2 (south of the Snowy Range) and flows in a south direction through Keystone before turning in a southwest direction to be joined by northwest oriented Pelton Creek and then to turn to flow in a northwest direction to join the North Platte River. Further north most streams flowing from the Medicine Bow Mountains to the North Platte River are oriented in southwest directions and join the north-northwest oriented North Platte River as barbed tributaries. These streams include southwest oriented Savage Run Creek, southwest oriented North Mullen Creek and Mullen Creek, and southwest oriented South Fork French Creek (and French Creek). West of the North Platte River most streams are oriented in northeast directions, although a southeast oriented North Fork can be seen south of Bear Mountain. The Laramie River flows in a north direction from the south edge of figure 2 (east half) to Woods Landing and then turns to flow in an east direction to the east edge of figure 2 (south of center). Note how an east oriented Laramie River tributary originates near Mountain Home (just east of the west oriented Pelton Creek segment). East of figure 2 the Laramie River flows in a northeast direction to Laramie, Wyoming and then continues in a north and northeast direction to eventually join the southeast oriented North Platte River. The Little Laramie River (Middle Fork) originates near the Douglas Creek headwaters and flows in a northeast, south, and east direction through Deerwood before turning in a north, northeast, and east direction to flow to the east edge of figure 2 (near northeast corner). East of figure 2 the Little Laramie River turns to flow in a northeast direction to join the Laramie River. The North Fork Little Laramie River flows in a south-southeast direction near Centennial before joining the north and northeast oriented Little Laramie River as a barbed tributary. The south oriented tributaries flowing to the north oriented Laramie and North Platte Rivers provide evidence the regional drainage direction has been reversed. The drainage reversal occurred after emergence of the Medicine Bow Mountains, which means higher elevation drainage routes reflect the original south oriented flood flow movements.

Pelton Creek-North Platte River drainage divide area

Figure 3: Pelton Creek-North Platte River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of Pelton Creek-North Platte River drainage divide area. The map contour interval for figure 3 is 50 meters. The west to east oriented Wyoming-Colorado state line is located near the south edge of figure 3. The North Platte River flows in a north-northwest direction from the south edge of figure 3 (west half) to near the northwest corner of figure 3. Douglas Creek flows in a south, southwest, and northwest direction from the north edge of figure 3 (east of center) to join the North Platte River near the northwest corner of figure 3. Mountain Home is a town near the southeast corner of figure 3. Pelton Creek flows in a south direction to Mountain Home and then turns to flow in a west and northwest direction to join Douglas Creek at the point where Douglas Creek turns to flow in a northwest direction. Heldrich Creek flows in a south direction west of Mountain Home to join east oriented Boswell Creek (not labeled in figure 3) near the southeast corner of figure 3. East of figure 3 Boswell Creek flows to the north oriented Laramie River. Through valleys in the Mountain Home area link the west and northwest oriented Pelton Creek valley with the east oriented Boswell Creek valley. The north-northwest oriented North Platte River valley has been eroded across the western margin of the Medicine Bow Mountains uplift even though a deeper north-northwest to south-southeast oriented through valley (used by the highway) is located just to the west. Streams flowing to the north-northwest oriented North Platte River fin southwest directions are barbed tributaries. Many streams flowing to northwest oriented Douglas Creek and to Pelton Creek segments are also barbed tributaries while the south and southwest oriented Douglas Creek segments also have south oriented tributaries. The predominance of south oriented drainage routes in what is today a north oriented drainage basin suggests a major reversal of drainage has taken place. The northwest oriented Pelton Creek and Douglas Creek alignment was initiated as a southeast oriented flood flow channel diverging from a south-southeast oriented flood flow channel on the present day north-northwest oriented North Platte River alignment. At least some of the southeast oriented flood flow on the Douglas-Pelton Creek alignment flowed in an east direction to the Mountain Home area where the water continued in an east direction to what was probably a south oriented flood flow channel on the present day north oriented Laramie River alignment. Emergence of the Medicine Bow Mountains by headward erosion of deeper valleys on either side and by crustal warping that raised the mountain range resulted in a beheading and reversal of the southeast and east oriented flood flow channel to create the present day west and northwest oriented Pelton Creek drainage route and the northwest oriented Douglas Creek drainage route, which captured the south and southwest oriented Douglas Creek headwaters drainage route. The Pelton Creek-Douglas Creek flood flow reversal may have occurred before the reversal of flood flow on the North Platte River alignment. This interpretation is suggested by the southwest turn Douglas Creek makes just before joining the north-northwest oriented North Platte River.

Detailed map of East Walbright Creek-Walbright Creek drainage divide area

Figure 4: Detailed map of East Walbright Creek-Walbright 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 East Walbright Creek-Walbright Creek drainage divide area seen in less detail in figure 3. The map contour interval for figure 4 is 20 feet. The north-northwest oriented North Platte River can just barely be seen near the southwest corner of figure 4. Walbright Creek flows in a southwest direction from section 26 to join the north-northwest oriented North Platte River as a barbed tributary near the southwest corner of figure 4. Douglas Creek flows in a west and northwest direction from the east edge of figure 4 to the north edge of figure 4 (west of center). Pelton Creek flows in a north-northwest direction from the east edge of figure 4 (south half) to join Douglas Creek near the east center edge of figure 4. East Walbright Creek flows in an east direction from the south half of section 24 to join Douglas Creek in the southeast quadrant of section 19. A through valley in the southwest quadrant of section 24 links the east oriented East Walbright Creek valley with a west and south oriented Walbright Creek tributary valley. The through valley floor elevation is between 8740 and 8760 feet. Platte Ridge to the north rises to more than 9040 feet and elevations to the south rise to 8938 feet suggesting the through valley is almost 200 feet deep. While not deep compared to the deeper valleys on either side the through valley is a water-eroded valley and was probably eroded by west oriented flood flow moving to what was then the actively eroding Walbright Creek valley, which had eroded headward from a south oriented flood flow channel on the present day north-northwest oriented North Platte River alignment. At that time the deep Douglas Creek and Pelton Creek valleys did not exist and floodwaters were flowing in shallow valleys no deeper than the through valley is today. The west oriented flood flow channel was probably captured by headward erosion of a deeper southeast oriented valley on the present day northwest oriented Pelton Creek-Douglas Creek alignment. Floodwaters on the east end of the beheaded west oriented flood flow channel reversed flow direction to create the east oriented Walbright Creek drainage route.

Douglas Creek-Douglas Creek drainage divide area

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

Figure 5 illustrates the Douglas Creek-Douglas Creek drainage divide area north and slightly west of figure 3 and there is an overlap area with figure 3. The map contour interval for figure 5 is 50 meters. The North Platte River flows in a north and northwest direction from the south edge of figure 5 (west half) to the west edge of figure 5 (north of center). Douglas Creek flows in a south and southwest direction from Rob Roy Reservoir (in northeast quadrant of figure 5) to near the south edge of figure 5 (east of center) where it turns to flow in a northwest direction to join the north oriented North Platte River. Note how Douglas Creek turns in a south direction to join the north oriented North Platte River. North Mullen Creek is the southwest and south oriented stream flowing across the northwest corner of figure 5 and joins southwest oriented South Mullen Creek east of Overlook Hill to form south-southwest oriented Mullen Creek, which then joins the north oriented North Platte River as a barbed tributary near the west edge of figure 5. Savage Run Creek and Cottonwood Creek are southwest oriented streams joining the North Platte River as barbed tributaries between Mullen Creek and Douglas Creek. The northwest oriented Douglas Creek segment has southwest and south-southwest oriented tributaries including Sheep Creek, Devils Gate Creek, Hans Creek, and Anderson Creek, all of which are barbed tributaries. The south oriented Douglas Creek segment in the east half of figure 5 has south oriented tributaries from both sides. From the west Horse Creek, Keystone Creek, Flume Creek, and Smith North Creek all flow in a southeast directions to join south oriented Douglas Creek as normal tributaries. From the east Little Beaver Creek, Muddy Creek, and Lake Creek all flow in southwest directions to join south oriented Douglas Creek as normal tributaries. In other words the secondary drainage routes seen in figure 5 are relics of a south oriented drainage pattern developed as south oriented flood flow moved across the emerging Medicine Bow Mountains. The northwest oriented Douglas Creek segment alignment originated as a southeast oriented flood flow channel diverging from a south oriented flood flow channel on the present day north oriented North Platte River alignment and then continuing in a southeast and east direction on the present day west and northwest oriented Pelton Creek alignment seen in figure 3. Uplift of the Medicine Bow Mountains and headward erosion of a much deeper (probably south oriented) valley on the North Platte River alignment beheaded the diverging southeast oriented flood flow channel. Floodwaters on the northwest end of the beheaded flood flow channel reversed flow direction to create the northwest oriented Douglas Creek drainage route segment and the northwest and west oriented Pelton Creek drainage route and to capture the south and southwest oriented Douglas Creek drainage route.

Detailed map of Douglas Creek-Spring Creek drainage divide area

Figure 6: Detailed map of Douglas Creek-Spring 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 Douglas Creek-Spring Creek drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 20 feet. Keystone is the small town in section 22 (in north center area of figure 6). Douglas Creek flows in a southeast direction from the north edge of figure 6 (west half) to Keystone and then flows in a south direction to the south edge of figure 6. Figure 6 shows tributaries not seen in figure 5 and all of the Douglas Creek tributaries seen in figure 6 flow in southeast or southwest directions to join Douglas Creek as normal tributaries. Muddy Creek flows in a south-southwest and south direction from the east center edge of figure 6 to the south edge of figure 6 (east half) and south of figure 6 joins south oriented Douglas Creek. Spring Creek is a south oriented Muddy Creek tributary originating near the northeast corner of figure 6 and joins Muddy Creek near the north edge of section 36. Near the northeast corner of figure 6 a shallow through valley links the southwest oriented Little Beaver Creek valley (draining to the south oriented Douglas Creek valley) with the south oriented Spring Creek valley. Shallow through valleys crossing the Douglas Creek-Spring Creek drainage divide also link the south oriented Spring Creek valley with southwest oriented Douglas Creek tributary valleys. In the southeast quadrant of section 20 (near west edge of figure 6) a shallow through valley links the Keystone Creek valley with the Flume Creek valley. These and other shallow through valleys provide evidence of flood flow channels that once existed prior to headward erosion of deeper valleys that beheaded them. For example, headward erosion of the deeper south oriented Spring Creek valley beheaded southwest oriented valleys eroding headward from the south oriented Douglas Creek valley. Or headward erosion of the southeast, east, and southeast oriented Keystone Creek valley beheaded south oriented flood flow routes to the newly eroded southeast oriented Flume Creek valley. In general the region seen in figure 6 was eroded by south oriented flood flow as south oriented valleys eroded headward into and across the region and as southeast and southwest oriented valleys eroded headward from those south oriented valleys.

South French Creek-Douglas Creek drainage divide area

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

Figure 7 illustrates the South French Creek-Douglas Creek drainage divide area north of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 7 is 50 meters. Rob Roy Reservoir is located in the southeast quadrant of figure 7. Douglas Creek flows in a southeast and southwest direction to Rob Roy Reservoir and then flows in a south direction to the south edge of figure. As seen in earlier figures Douglas Creek south and west of figure 7 flows in a south, southwest, and northwest direction to join the north-northwest oriented North Platte River. South French Creek flows from the north edge of figure 7 (east of center) in a south and southwest direction to the west edge of figure 7 (south half). North French Creek originates near the north edge of figure 7 (west of center) and flows in a west-southwest and south-southwest direction to join South French Creek near the west edge of figure 7 and to form southwest oriented French Creek, which west of figure 7 joins the North Platte River as a barbed tributary. West Mullen Creek flows in a southwest direction from the center of figure 7 to join southwest and south oriented North Mullen Creek, which flows to the south edge of figure 7 (near southwest corner) and which joins southwest oriented South Mullen Creek south of figure 7 to form south oriented Mullen Creek, which then joins the North Platte River as a barbed tributary. The Middle Fork Little Laramie River originates in Willow Park just north of the Douglas Creek headwaters and flows in an east and northeast direction almost to the east edge of figure 7 (north half). East of figure 7 the Middle Fork Little Laramie River turns in south-southwest direction to reenter figure 7 near the east center edge where it is joined by east and southeast oriented June Creek and then flows in a southeast direction to the east edge of figure 7 (just south of center). East of figure the Middle Fork Little Laramie River joins the South Fork Little Laramie River to form the north and northeast oriented Little Laramie River, which flows to the north and northeast oriented Laramie River. In other words the southeast oriented Douglas Creek headwaters are flowing along what is today the high North Platte River-Laramie River drainage divide in the high Medicine Bow Mountains. The high drainage divide along the Medicine Bow Mountains crest was created as south oriented flood flow was captured by headward erosion of deep valleys from south oriented flood flow channels on either side of the emerging mountain mass. Some south and southeast oriented flood flow to the southeast oriented Douglas Creek headwaters valley was captured by headward erosion of the east and northeast oriented Middle Fork Little Laramie River valley and southeast oriented flood flow to both the Douglas Creek and the Middle Fork Little Laramie River valleys was then beheaded by headward erosion of the much deeper south and southwest oriented South French Creek valley. South French Creek originates north of figure 7 at the base of the Snowy Range (see figure 8), which is the highest region in the Wyoming Medicine Bow Mountains today. If correctly interpreted at the time floodwaters crossed the region seen in figure 7 the Medicine Bow Mountains did not stand high above surrounding regions and floodwaters could at first cross what is today a high mountain region. Since that time ice sheet related crustal warping has raised the Medicine Bow Mountains and/or melt water flood erosion has deeply eroded the surrounding valleys and basins.

South French Creek- Little Laramie River drainage divide area

Figure 8: South French Creek- Little Laramie River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 provides a topographic map of the South French Creek- Little Laramie River drainage divide area north and east of figure 7 and includes an overlap area with figure 7. The map contour interval for figure 8 is 50 meters. The Snowy Range is located in the northwest quadrant of figure 8 and the labeled high points are Medicine Bow Peak (3652 meters) and Browns Peak (3573 meters). Snowy Range peaks are the highest elevations in the Wyoming Medicine Bow Mountains. South French Creek originates south of Medicine Bow Peak and flows in a south and southwest direction to the west edge of figure 8 (near southwest corner). West and south of figure 8 South French Creek flows to southwest oriented French Creek, which then joins the north-northwest oriented North Platte River as a barbed tributary. South oriented floodwaters that eroded the south and southwest oriented South French Creek valley must have flowed across the Snowy Range using the through valley (or pass) located between Medicine Bow Peak and Browns Peak. The through valley floor elevation is between 3350 and 3400 meters suggesting the through valley is at least 173 meters deep. Since that time, but after all flood flow across the region had ended and after the Medicine Bow Mountains had emerged as a high mountain range, the Snowy Range area was glaciated and glaciers modified the flood-eroded valleys. East oriented drainage routes in the east half of figure 8 flow to the north and northeast oriented Little Laramie River, which flows across the southeast corner of figure 8. The North Fork Little Laramie River originates near the north center edge of figure 8 and flows in a south-southeast direction to join the north and northeast oriented Little Laramie River just south of the southeast corner of figure 8. The Middle Fork Little Laramie River originates in Willow Park (in southwest quadrant of figure 8) and flows in an east, northeast, east, and south-southwest direction to the south edge of figure 8 (east of center) and south of figure 8 turns to flow in a southeast direction to join the north oriented Little Laramie River. Nash Creek is a southeast oriented North Fork Little Laramie River tributary originating near the east end of the Snowy Range. South oriented streams joining the north oriented Little Laramie River on the east side of the Medicine Bow Mountains are barbed tributaries just as the south oriented streams joining the north oriented North Platte River on the west side of the Medicine Bow Mountains are barbed tributaries. These barbed tributaries are evidence the Medicine Bow Mountains were eroded by multiple south oriented drainage routes delivering floodwaters to south oriented drainage routes on both the east and west sides of the emerging Medicine Bow Mountains and that the Little Laramie River and North Platte River drainage routes were not reversed until after the Medicine Bow Mountains had emerged (so drainage routes in the Medicine Bow Mountains were not affected by the flood flow reversals in the deeper valleys on either side of the newly uplifted mountain mass).

French Creek-North Platte River drainage divide area

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

Figure 9 illustrates the French Creek-North Platte 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 North Platte River flows in a northwest, west, and north-northwest direction from the south center edge of figure 9 to the west edge of figure 9 (north half). South French Creek flows in a southwest direction from the north edge of figure 9 (east half) to join south-southwest oriented North French Creek near a labeled Campground and to form southwest oriented French Creek, which then flows to the northwest oriented North Platte River as a barbed tributary. North Mullen Creek originates near the northeast corner of figure 9 and flows in a southwest and south direction to join southwest oriented South Mullen Creek (east of Overlook Hill) and to form south-southwest oriented Mullen Creek, which also flows to the northwest oriented North Platte River as a barbed tributary. A north to south oriented through valley links the south-southwest oriented North French Creek valley with the south-southwest oriented Mullen Creek valley. The through valley is defined by two contour lines on the west suggesting the through valley is at least 50 meters deep. While probably eroded along the strike of dipping strata the through valley is a water-eroded valley and was eroded by south oriented flood flow prior to headward erosion of the much deeper southwest oriented French Creek valley. South and west of the North Platte River a Landing Strip near the southwest corner of figure 9 is located in another interesting through valley. North of the Landing Strip Barcus Creek drains in a north and north-northeast direction. South of the Landing Strip Bull Creek flows in southeast direction to join north, west, and north oriented Big Creek as a barbed tributary. South of figure 9 the north oriented Big Creek valley is linked by a through valley with the north-northwest oriented North Platte River valley. The Barcus Creek-Bull Creek through valley floor elevation is between 2350 and 2400 meters. Elevations on the Big Creek-North Platte River drainage divide along the south edge of figure 9 exceed 2550 meters suggesting the Barcus Creek-Bull Creek through valley could be a deeper channel in a through valley almost 200 meters deep. The through valley was eroded by south-southeast oriented flood flow prior to the reversal of flood flow in the North Platte River valley. Crustal warping that was raising the area south of figure 9 not only reversed flood flow on the North Platte River alignment, but also reversed flood flow on the Big Creek alignment and today southeast oriented Bull Creek is a relic of a former south oriented flood flow channel.

Detailed map of French Creek-North Mullen Creek drainage divide area

Figure 10: Detailed map of French Creek-North Mullen 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 French Creek-North Mullen Creek drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 40 feet. French Creek flows in a southwest direction from the north center edge of figure 10 to the west center edge of figure 10. West of figure 10 French Creek flows in a southwest direction to join the northwest oriented North Platte River as a barbed tributary. North Mullen Creek flows in a southwest and south direction from the east edge of figure 10 (north of center) to the south edge of figure 10. South of figure 10 North Mullen Creek joins South Mullen Creek to form south-southwest oriented Mullen Creek, which flows to the northwest oriented North Platte River as a barbed tributary. South Mullen Creek flows in a south-southwest direction across the southeast corner of figure 10. South of figure 10 South Mullen Creek joins North Mullen Creek. A through valley extending from section 34 to section 11 links the French Creek valley with the south oriented North Mullen Creek valley. The through valley floor elevation is between 8120 and 8160 feet. Elevations near the southwest corner of section 11 rise to 8536 feet and much higher elevations are found east of the through valley. Based on these elevations an argument could be made the through valley is at least 370 feet deep. While the ridge west of the through valley is probably a hogback ridge the through valley was eroded by south oriented water flowing to the south oriented North Mullen Creek valley prior to headward erosion of the much deeper southwest oriented French Creek valley. Headward erosion of the deeper French Creek valley captured the south oriented flood flow and diverted the floodwaters in a southwest direction to a south oriented flood flow channel on the present day northwest oriented North Platte River alignment. Other interesting through valleys cross drainage divides in the region seen in figure 10. For example in the southwest quadrant of section 1 a through valley links the southwest oriented North Mullen Creek valley with a south-southwest valley draining to the south oriented North Mullen Creek valley near the south edge of section 11. This higher level through valley has a floor elevation of between 8440 and 8480 feet. Elevations on the ridge between North Mullen Creek and the south-southwest oriented tributary rise to 8542 feet suggesting the through valley is at least 80 feet deep. While not deep this through valley provides evidence of what at one time were diverging and converging flood flow channels prior to headward erosion of the much deeper southwest and south oriented North Mullen Creek valley.

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.