Medicine Bow River-North Platte River drainage divide area landform origins in the Wyoming Medicine Bow Mountains, USA

Authors

 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the Medicine Bow River-North Platte River drainage divide area in the Wyoming Medicine Bow Mountains. The Medicine Bow Mountains extend in a north-northwest to south-southeast direction across the Wyoming-Colorado border and the North Platte River flows in a north-northwest direction along west side of the Wyoming Medicine Bow Mountains with southwest oriented streams flowing from the Medicine Bow Mountains to the North Platte River as barbed tributaries. The north and northeast oriented Laramie and Little Laramie River drain the east side of the Wyoming Medicine Bow Mountains and are joined by southeast oriented tributaries flowing from the Medicine Bow Mountains. The north end of the Medicine Bow Mountains is drained by the north oriented Medicine Bow River, which originates in the high Snowy Range and which north of the Medicine Bow Mountains turns to flow in a northeast, northwest, and west direction to join the north oriented North Platte River. Rock Creek is north, northeast, and northwest oriented Medicine Bow River tributary located east of the north oriented Medicine Bow River headwaters and Pass Creek is a north, northwest, west, north, and southwest oriented North Platte River tributary located west of the Medicine Bow River headwaters. A deep through valley links the north oriented Rock Creek headwaters valley with the south-southeast oriented North Fork Little Laramie River headwaters valley. A deep gap or through valley between the two highest peaks in the Snowy Range link the north oriented Medicine Bow River headwaters valley with a North Fork Little Laramie River tributary valley and with a south and southwest oriented North Platte River tributary valley. And a deep through valley links the north and northwest oriented Pass Creek headwaters valley with a southwest oriented North Platte River tributary valley. Further, Pass Creek has eroded a deep west oriented water gap across a high Medicine Bow Mountains ridge and is linked to the Medicine Bow River and North Platte River valleys by deep wind gaps or through valleys. These features are interpreted in the context of immense melt water floods that flowed from the western margin of a thick North American ice sheet in western Canada to and across the Medicine Bow Mountains region at a time when the Medicine Bow Mountains were emerging. At first floodwaters were able to flow across the emerging Medicine Bow Mountains, but later floodwaters were channeled into deep south oriented flood flow channels on either side of the emerging mountain mass. The Medicine Bow Mountains emerged as floodwaters deeply eroded surrounding regions and as ice sheet related crustal warping raised the mountains and the entire region. The north oriented North Platte River, Laramie River, Little Laramie River, Medicine Bow River, Rock Creek, Pass Creek, and tributary drainage routes were created by reversals of flood flow on north ends of south oriented flood flow channels beheaded by headward erosion of much deeper valleys. Crustal warping that was raising the Medicine Bow Mountains and the entire region contributed to the flood flow reversals.

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 Medicine Bow River-North Platte River 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 Medicine Bow River-North Platte River 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.

Medicine Bow River-North Platte River drainage divide area location map

Figure 1: Medicine Bow River-North Platte River drainage divide area location map (select and click on maps to enlarge). National Geographic Society map digitally presented using National Geographic Society TOPO software.

Figure 1 provides a location map for the Medicine Bow River-North Platte River 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. The Medicine Bow Mountains extend in a north-northwest direction from the south edge of figure 1 (east of center) into southern Wyoming. The Laramie Mountains extend in a southeast and south direction from near Casper (near north edge of figure 1-slightly east of center). The North Platte River flows from near Coalmont (near south center edge of figure 1) in a north and north-northwest direction along the west side of the Medicine Bow Mountains into southern Wyoming and then turns to flow in a northeast, north, and north-northeast direction to near Casper. From Casper the North Platte River flows in an east, south, and southeast direction to the east edge of figure 1 (slightly north of center). Pass Creek is a northwest and west oriented North Platte River tributary originating south of Elk Mountain near the north end of the Medicine Bow Mountains. The Laramie River originates near the south edge of figure 1 on the east side of the Medicine Bow Mountains and flows in a north direction to the state line and then turns to flow in a northeast direction to Laramie. From Laramie the Laramie River flows in a north-northwest and northeast direction to join the southeast oriented North Platte River near the town of Fort Laramie. The Laramie River crosses the Laramie Mountains in a deep water gap. The Medicine Bow River originates near the north end of the Medicine Bow Mountains and flows in a north direction to the town of Elk Mountain where it turns to flow in a northeast and northwest direction to the town of Medicine Bow. From Medicine Bow the Medicine Bow River flows in a northwest and west direction to join the north oriented North Platte River at Seminoe Reservoir. Rock Creek is an unlabeled stream originating north and east of Medicine Bow Peak and flowing in a north and northeast direction to the towns of McFadden and Rock River and then turning in a northwest direction to join the Medicine Bow River near the town of Medicine Bow. The Medicine Bow River-North Platte River drainage divide area in the Wyoming Medicine Bow Mountains investigated in this essay is located in the northern Medicine Bow Mountains and includes the Rock Creek, Medicine Bow River, and Pass Creek headwaters areas.

Wyoming drainage routes developed during immense melt water floods, which began before Wyoming mountain ranges had emerged. Floodwaters were derived from the western margin of a thick North American ice sheet and were flowing from western Canada to and across Wyoming. Wyoming mountain ranges emerged as floodwaters deeply eroded surrounding basins and valleys and as ice sheet related crustal warping raised the mountain ranges. What are today north oriented drainage routes, including the North Platte River (west of the Laramie Mountains), Laramie River, and the Medicine Bow River, Rock Creek, and Pass Creek headwaters originated as south oriented flood flow channels prior to reversals of flood flow that created the present day north oriented drainage routes. Flood flow reversals occurred as ice sheet related crustal warping raised mountain ranges and entire regions and as headward erosion of much deeper valleys beheaded the south oriented flood flow channels. For example, headward erosion of the southeast oriented North Platte River valley around the northwest end of the Laramie Mountains beheaded south oriented flood flow channels west of the Laramie Mountains. Floodwaters on the north ends of the beheaded flood flow channels reversed flow direction to flow to much deeper east and southeast oriented valley and to create the north, east, and southeast oriented North Platte River drainage route. The flood flow reversal, which took place in multiple steps, was greatly aided by crustal warping that was raising the North Platte River headwaters area. Previously headward erosion of deep west (and possibly east) oriented valleys north of the emerging Medicine Bow Mountains had beheaded south oriented flood flow channels crossing the present day Medicine Bow Mountains. Floodwaters on north ends of the beheaded flood flow channels reversed flow direction to flow to the much deeper west (and possibly east) oriented valleys with uplift of the Medicine Bow Mountains contributing to the flood flow reversals.

Detailed location map for Medicine Bow River-North Platte River drainage divide area

Figure 2: Detailed location map Medicine Bow River-North Platte River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 2 provides a detailed location map for the Medicine Bow River-North Platte River drainage divide area in the Wyoming Medicine Bow Mountains. The green colored area is National Forest land in the Medicine Bow Mountains. The North Platte River flows in a northwest direction from the south edge of figure 2 (just west of green colored area) to Saratoga and then to the west edge of figure 2. Named North Platte River tributaries from the Medicine Bow Mountains (from south to north) include southwest oriented Mullen Creek, South French Creek, North French Creek, Brush Creek, and Elk Hollow Creek. Cedar Creek has southwest oriented headwaters and Dry Creek flows in a northwest and south direction to join southwest oriented Lake Creek. Pass Creek flows in a northwest, west, and north direction to the north edge of figure 2 and north of figure 2 turns to flow in a southwest direction to join the northwest oriented North Platte River. This abundance of barbed tributaries provides evidence the present day north oriented North Platte River drainage route originated as a south oriented drainage route and collected significant south oriented flow from the present day high Medicine Bow Mountains. The Snowy Range is labeled and is today the highest region in the Wyoming Medicine Bow Mountains with Medicine Bow Peak being the highest peak in the Wyoming Medicine Bow Mountains. [Note: the northwest and southwest oriented stream originating north of Medicine Bow Peak and flowing to southwest oriented Brush Creek is mislabeled in figure 2 and should be labeled North Brush Creek.] On the east side of the Medicine Bow Mountains the Little Laramie River flows in a north and northeast direction from the south edge of figure 2 (east half) to the east edge of figure 2 (south of center) and east of figure 2 joins the north and northeast oriented Laramie River. The North Fork Little Laramie River (not labeled) originates east of the Snowy Range and flows in a south-southeast direction to near the town of Centennial and then makes a U-turn to join the north and northeast oriented Little Laramie River. The Middle Fork Little Laramie River (also not labeled) originates south of the Snowy Range and flows in a northeast, south, southeast and east direction to Deerwood and then joins the north and northeast oriented Little Laramie River. These south oriented tributaries to the present day north oriented Little Laramie River are evidence the Little Laramie River also originated as a south oriented drainage route and received significant south oriented flow from the present day Medicine Bow Mountains. The Medicine Bow River originates north of Medicine Bow Peak (in Snowy Range area) and flows in a north-northwest and north direction to the north center edge of figure 2. North of figure 2 the Medicine Bow River flows in a northeast, northwest, and west direction to join the north oriented North Platte River. Rock Creek originates north of the North Fork Little Laramie River headwaters and flows in a north, northwest, and northeast direction to Arlington and then to the north edge of figure 2 (east half). North of figure 2 Rock Creek turns to flow in a northwest direction to join the Medicine Bow River.

Rock Creek-North Fork Little Laramie River drainage divide area

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

Figure 3 provides a topographic map of Rock Creek-North Fork Little Laramie River drainage divide area. The map contour interval for figure 3 is 50 meters. The Snow Range extends in a northeast direction from the southwest corner of figure 3 and Medicine Bow Peak is located in the Snowy Range near the west edge of figure 3.  The Medicine Bow River originates on the north side of the Snowy Range and flows in a northwest direction to the west edge of figure 3 (north half). West and north of figure 3 the Medicine Bow River turns to flow in a north, northeast, northwest, and west directions to eventually reach the north oriented North Platte River. Rock Creek originates near the center of figure 3 and flows in a north direction on the west side of Rock Creek Ridge to the north center edge of figure 3. North of figure 3 Rock Creek flows in a north, northeast, and northwest direction to eventually join the Medicine Bow River. A close look reveals that Rock Creek originates as a southeast oriented stream and then makes a U-turn to flow in a north direction. North of the southeast oriented Rock Creek headwaters are the following northeast oriented Rock Creek tributaries: South Fork, Trail Creek, Middle Fork, North Fork, and Deep Creek with North Fork and Deep Creek joining Rock Creek north of figure 3. The North Fork Little Laramie River originates near North Twin Lakes (just south of the South Fork Rock Creek headwaters) and flows in a southeast and south-southeast direction to the south edge of figure 3 (east of center-just west of Corner Mountain). South of figure 3 the North Fork flows in a south-southeast direction before making a U-turn to join the north and northeast oriented Little Laramie River, which then flows to the north and northeast oriented Laramie River. The southeast and east-southeast oriented stream originating at Telephone Lakes and joining the North Fork Little Laramie River near Corner Mountain is Nash Fork. A north to south oriented through valley links the north oriented Rock Creek valley with the south-southeast oriented North Fork Little Laramie River valley. The through valley floor elevation at the drainage divide is between 3000 and 3050 meters. Rock Creek Point to the east rises to 3232 meters and Medicine Bow Peak to the west rises to 3652 meters. These elevations suggest the through valley is at least 183 meters deep. This deep north to south oriented through valley was eroded by south oriented flood flow moving from the present day north oriented Rock Creek alignment to the south-southeast oriented North Fork Little Laramie River valley. At that time elevations north of the through valley were at least as high as the through valley floor and the Medicine Bow Mountains had not emerged as the high mountain range they are today. Headward erosion of much deeper valleys north of the emerging mountains beheaded and reversed the south oriented flood flow route as ice sheet related crustal warping raised the Medicine Bow Mountains.

Detailed map of Rock Creek-North Fork Little Laramie River drainage divide area

Figure 4: Detailed map of Rock Creek-North Fork Little Laramie River 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 Rock Creek-North Fork Little Laramie River drainage divide area seen in less detail in figure 3. The map contour interval for figure 4 is 20 feet in the north and 40 feet near the south edge. Rock Creek originates in section 31 and flows in a southeast direction into section 32 where it turns to flow in a north direction to the north edge of figure 4 (east of center). North of figure 4 Rock Creek flows in a north, northeast, and northwest direction to join the Medicine Bow River. The North Fork Little Laramie River originates in the section 2 and flows in an east direction across the south margin of section 1 to the northwest corner of section 7 and then flows in an east-southeast direction into section 8 where it turns to flow in a south-southeast direction to the south edge of figure 4 (east of center). South of figure 4 the North Fork Little Laramie River flows in a south-southeast direction before making a U-turn to flow to the north and northeast oriented Little Laramie River, which then flows to the north and northeast oriented Laramie River. A north to south oriented through valley near the corner of sections 31, 32, 5, and 6 links the north oriented Rock Creek valley with the valley of a south-southeast oriented North Fork Little Laramie River tributary. The through valley floor elevation is shown as being 9942 feet. Rock Creek Point in section 28 (near northeast corner of figure 4) rises to 10,603 feet and Rock Creek Knoll in section 35 (near northwest corner of figure 4) rises to 11,125 feet suggesting the through valley is more than 650 feet deep. The through valley is a water-eroded valley and was eroded by south oriented flood flow moving from the present day north oriented Rock Creek valley to the much deeper south-southeast oriented North Fork Little Laramie River valley. At the time floodwaters flowed across the Medicine Bow Mountains regions to the north of the Medicine Bow Mountains had not been eroded and were at least as high as the through valley floor. Since that time regions north of the Medicine Bow Mountains have been deeply eroded and uplift of the Medicine Bow Mountains has probably raised the through valley floor elevation from what it was at the time floodwaters crossed the Rock Creek-North Fork Little Laramie River drainage divide.

Medicine Bow River-South French Creek drainage divide area

Figure 5: Medicine Bow River-South French Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Medicine Bow River-South French Creek drainage divide area west of figure 3 and there is an overlap area with figure 3. The map contour interval for figure 5 is 50 meters. The Snowy Range extends in a northeast direction across the south half of figure 5 and is the highest region in the Wyoming Medicine Bow Mountains (there are higher regions in the Colorado Medicine Bow Mountains to the south). Medicine Bow Peak is the highest peak with an elevation of 3652 meters and Browns Peak is the labeled mountain with an elevation of 3573 meters. The Medicine Bow River originates north of Browns Peak and flows in a northwest and north direction to the north edge of figure 5 (west of center). North of figure 5 the Medicine Bow River flows in a north, northeast, northwest, and west direction to eventually join the north oriented North Platte River. Rock Creek originates near the east center edge of figure 5 and flows in a north direction to the north edge of figure 5 (near northeast corner). North of figure 5 Rock Creek flows in a north, northeast, and northwest direction to eventually join the Medicine Bow River. The North Fork Little Laramie River flows in a southeast direction from North Twin Lakes (south of Rock Creek Knoll in the east center area of figure 5) to the east edge of figure 5 (south half). East and south of figure 5 the North Fork Little Laramie River flows in a south-southeast direction before making a U-turn to flow to the north and northeast oriented Little Laramie River, which then flows to the north and northeast oriented Laramie River. South Brush Creek originates west of Medicine Bow Peak and flows in a west-southwest direction to the west edge of figure 5 (near southwest corner) and west of figure 5 joins southwest oriented North Brush Creek to form southwest oriented Brush Creek, which then joins the north-northwest oriented North Platte River as a barbed tributary. North Brush Creek originates north of the South Brush Creek headwaters and flows in a northwest and west direction to the west edge of figure 5 (north of center). West of figure 5 North Brush Creek turns to flow in a southwest direction to join South Brush Creek and to form southwest oriented Brush Creek. The south oriented stream originating south of Medicine Bow Peak and flowing to the south center edge of figure 5 is South French Creek, which south of figure 5 turns to flow in a southwest direction to join west-southwest and south-southwest oriented North French Creek and to form southwest oriented French Creek, which joins the north-northwest oriented North Platte River as a barbed tributary. A gap or through valley between Medicine Bow Peak and Browns Peak links the northwest and north oriented Medicine Bow River drainage route with the south and southwest oriented South French Creek drainage route. The gap floor elevation is between 3350 and 3400 meters suggesting the gap is at least 173 meters deep. While the Snowy Range has been glaciated the gap is probably a water-eroded feature and was probably eroded as a south oriented flood flow channel at a time when the Snowy Range region did not stand high above surrounding areas as it does today. The floodwaters probably moved in a south direction along the present day north oriented Medicine Bow River alignment to the south and southwest oriented South French Creek and French Creek alignment and then to a south-southeast oriented flood flow channel on the present day north-northwest oriented North Platte River alignment. Since that time the Medicine Bow Mountains have been uplifted and regions north of the Medicine Bow Mountains have been deeply eroded. After flood flow across the Medicine Bow Mountains had ended and after the Medicine Bow Mountains had been uplifted to form the high mountain range they today the Snowy Range region was glaciated, which further modified the landscape.

Detailed map of Medicine Bow River-South French Creek drainage divide area

Figure 6: Detailed map of Medicine Bow River-South French 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 Medicine Bow River-South French Creek drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 40 feet in the south and 20 feet in the north. The Snowy Range extends in a southwest to northeast direction across figure 6. Medicine Bow Peak is located near the north edge of section 18 and reaches an elevation of 12,013 feet. Browns Peak is located in the northwest corner of section 9 and the northeast corner of section 8 and reaches an elevation of 11,722 feet. A deep gap or through valley between Medicine Bow Peak and Browns Peak is located in the north half of section 8. North Gap Lake on the north side of the gap drains in a north direction with water flowing to the northwest and north oriented Medicine Bow River north of figure 6. North of the Snowy Range area and of the Medicine Bow Mountains the Medicine Bow River flows in a north, northeast, northwest, and west direction to join the north oriented North Platte River. South Gap Lake is located on the south side of the gap and is drained in a south direction to Libby Lake, which is drained by east and southeast oriented Libby Creek, which flows to the south edge of figure 6 (east half). South and east of figure 6 Libby Creek flows in an east and southeast direction to join the south-southeast oriented North Fork Little Laramie River, which then joins the north and northeast oriented Little Laramie River to flow to the north and northeast oriented Laramie River. West of Libby Lake is Sugarloaf Mountain and south of Sugarloaf Mountain are headwaters of a south oriented stream flowing to the south edge of figure 6 (west of center). That south oriented stream is South French Creek, which south and west of figure 6 flows in a south and southwest direction in a deep valley to join west-southwest and south-southwest oriented North French Creek and to form southwest oriented French Creek, which flows to the north-northwest oriented North Platte River as a barbed tributary. Large volumes of water were required to erode the deep South French Creek valley south and west of figure 6. The water probably flowed in a south direction through the gap in the Snowy Range ridge from the present day north oriented Medicine Bow River alignment to the south and southwest oriented South French Creek valley and then to a south-southeast oriented flood flow channel on the present day north-northwest oriented North Platte River alignment. Headward erosion of the Libby Creek valley from the south-southeast oriented North Fork Little Laramie River valley (which was eroding headward from a south oriented flood flow channel on the present day north oriented Little Laramie River alignment) captured the south oriented flood flow and diverted the floodwaters to the east side of the emerging Medicine Bow Mountains. Medicine Bow Mountains uplift combined with headward erosion of deep valleys north of the emerging Medicine Bow Mountains next beheaded and reversed the flood flow channel on the Medicine Bow River alignment to create the present day north oriented Medicine Bow River drainage route. After all flood flow across the region had ended and after the Medicine Bow Mountains had been uplifted to create the high mountain range they are today the Snowy Range region was glaciated. The alpine glaciers further modified the landscape and may have altered drainage routes near the gap, however the glaciers did not significantly change valley orientations nor did the glaciers erode the gap.

Pass Creek-North Brush Creek drainage divide area

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

Figure 7 illustrates the Pass Creek-North Brush Creek drainage divide area north and west of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 7 is 50 meters. The Snowy Range is located in the southeast corner of figure 7. Medicine Bow Peak (elevation 3652 meters) and Browns Peak (elevation 3573 meters) are labeled. The Medicine Bow River originates near the east edge of figure 7 and north of the Snowy Range and then flows in a northwest and north direction to the north edge of figure 7 (east half). North of figure 7 the Medicine Bow River flows in a north, northeast, northwest, and west direction to eventually join the north oriented North Platte River. Turpin Creek originates north of Medicine Bow Peak and flows in a north-northwest direction to Turpin Reservoir and then in a north direction to the north edge of figure 7 (slightly east of center). North of figure 7 Turpin Creek joins the north oriented Medicine Bow River. North Brush Creek originates just west of the Turpin Creek headwaters and flows in a northwest and southwest direction to near the southwest corner of figure 7. South and west of figure 7 North Brush Creek joins South Brush Creek to form southwest oriented Brush Creek, which flows to the north-northwest oriented North Platte River as a barbed tributary. Kennaday Peak is a labeled high point in the west half of figure 7 and reaches an elevation of 3295 meters. Pass Creek originates on the east side of Kennaday Peak and flows in an east, northeast, and north direction to the north edge of figure 7 (west of center). North of figure 7 Pass Creek flows in a northwest, west, north, and southwest direction to join the north oriented North Platte River as a barbed tributary. A broad through valley located between Kennaday Peak and the Snowy Range links the north oriented Pass Creek valley with the southwest oriented North Brush Creek valley. The through valley floor elevation is between 2800 and 2850 meters, which based on the Kennaday Peak elevation suggests the through valley could be as much as 450 meters deep. To what extent the through valley is a water-eroded valley is difficult to determine from topographic map evidence alone, although it is a water-eroded valley at least to some extent and perhaps is entirely a water-eroded feature. Water eroding the through valley was south oriented flood flow moving to a southwest oriented flood flow channel on the southwest oriented North Brush Creek and Brush Creek alignment and then to a south-southeast oriented flood flow channel on the present day north-northwest oriented North Platte River alignment. Uplift of the Medicine Bow Mountains combined with headward erosion of a much deeper valley on the North Platte River alignment enabled the west oriented Pass Creek valley (north of figure 7) to erode headward across the south oriented flood flow channel and to divert the captured floodwaters to North Platte River alignment. Floodwaters on the north end of the beheaded flood flow route reversed flow direction to create the north and northwest oriented Pass Creek drainage route directly north of the through valley.

Detailed map of Pass Creek-North Brush Creek drainage divide area

Figure 8: Detailed map of Pass Creek-North Brush 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 Pass Creek-North Brush Creek drainage divide area seen in less detail in figure 7. The map contour interval for figure 8 is 20 feet. Kennaday Peak is located near the west edge of the northwest quadrant of figure 8 and rises to 10,819 feet. Pass Creek headwaters are located on the east slope of Kennaday Peak and flow in east and northeast directions to the north center edge area of figure 8 and north of figure 8 Pass Creek flows in a northwest, west, north, and southwest direction to join the north oriented North Platte River. North Brush Creek flows in a west and southwest direction from the east edge of figure 8 (near southeast corner) to the south edge of figure 8 (west of center) and south and west of figure 8 North Brush Creek flows to southwest oriented Brush Creek, which then flows to the north-northwest oriented North Platte River as a barbed tributary. South and east of figure 8 is the Snowy Range where Medicine Bow Peak rises to 12,015 feet. Fish Creek originates on the east slope of Kennaday Peak in section 16 (just south of the east oriented Pass Creek headwaters) and flows in an east and south direction to join southwest oriented North Brush Creek near the south edge of figure 8. A through valley in section 14 links the north oriented Pass Creek valley with the south oriented Fish Creek valley. The through valley floor elevation at the lowest point is between 9260 and 9280 feet. Elevations just south of the south edge of the southeast quadrant of figure 8 rise to more than 10,698 feet suggesting the through valley is at least 1400 feet deep. The through valley was eroded by south and southwest oriented flood flow moving from the present day north oriented Pass Creek alignment (north of figure 8) to the southwest oriented North Brush Creek valley and then to a south-southeast oriented flood flow channel on the present day north-northwest oriented North Platte River alignment. Flood flow across the region seen in figure 8 ended as Medicine Bow Mountains uplift raised the region and as the deep west oriented Pass Creek valley eroded headward across the south oriented flood flow channel north of figure 8. Floodwaters on the north end of the beheaded flow channel reversed flow direction to create the north and northwest oriented Pass Creek drainage route north of figure 8. Continued Medicine Bow Mountains uplift and headward erosion of a much deeper North Platte River valley to the west of figure 8 have probably significantly increased the local relief since flood flow across the region ended.

Pass Creek-Medicine Bow River drainage divide area

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

Figure 9 illustrates the Pass Creek-Medicine Bow River drainage divide area north and west of figure 7 and there is a small overlap area with figure 7. The map contour interval for figure 9 is 20 meters except near the south edge where the contour interval is 50 meters. The Medicine Bow River flows in a northwest and north direction from the east edge of figure 9 (south half) to the north edge of figure 9 (near northeast corner). North of figure 9 the Medicine Bow River flows in a north, northeast, northwest, and west direction to eventually join the north oriented North Platte River. Turpin Creek flows in a north direction from the south edge of figure 9 (near southeast corner) to join the Medicine Bow River. Pass Creek flows in a northwest direction from the south edge of figure 9 (east half) to a deep water gap between Coad Mountain and Elk Mountain and then in a west direction to the west edge of figure 9 (north half). West and north of figure 9 Pass Creek flows in a north and southwest direction to join the north oriented North Platte River as a barbed tributary. Oberg Pass is a deep wind gap located south of Coad Mountain and north of Pennock Mountain and links northwest oriented Oberg Creek with northeast oriented Fox Creek (both Pass Creek tributaries). The Oberg Pass elevation is shown as being 2501 meters. Coad Mountain rises to 2882 meters and Pennock Mountain rises to more than 3040 meters suggesting Oberg Pass is almost 400 meters deep. Pass Creek is flowing at an elevation of approximately 2240 meters as it flows through the water gap between Elk Mountain and Coad Mountain. Elk Mountain rises to 3400 meters suggesting the water gap could be as much as 800 meters deep. East of Elk Mountain a northeast to southwest oriented through valley links the northeast oriented O’Mara Creek drainage route (flowing to the Medicine Bow River) with the southwest oriented Thode Creek drainage route (flowing to Pass Creek). The through valley floor elevation is between 2280 and 2300 meters at its deepest point. The through valley links the north oriented Medicine Bow River valley with the west oriented Pass Creek valley, which means the through valley southeast wall is really in the Medicine Bow Mountains to the south of figure 9 and that the through valley may be as much as 700 meters deep. The Pass Creek water gap, the Oberg Pass wind gap, and the Medicine Bow River-Pass Creek through valley are all water-eroded features and were initiated at a time when floodwaters were flowing on an erosion surface equivalent in elevation to the tops of Elk Mountain, Coad, Mountain, Pennock Mountain, and to the Medicine Bow Mountains upland surface seen in earlier figures to the south of figure 9. The depth of the Pass Creek Basin below the present day mountaintops illustrates the depth of erosion that occurred as floodwaters deeply eroded the region. Headward erosion of the west oriented Pass Creek valley captured what had been a major south oriented flood flow channel a south oriented flood flow channel on the present day Medicine Bow River alignment, and diverted those floodwaters in a west direction to a deeper flood flow channel on the North Platte River alignment. Floodwaters on the north ends of the beheaded south oriented flood flow channels, which had been diverging south oriented flood flow channels crossing the high Medicine Bow Mountains, reversed flow direction to flow to the much deeper Pass Creek valley to create the north oriented Medicine Bow Creek, Turpin Creek, and Pass Creek drainage routes in the Medicine Bow Mountains to the south. Subsequently flood flow on the Medicine Bow River alignment north of figure 9 was reversed to create the Medicine Bow River-Pass Creek drainage divide seen in figure 9.

Detailed map of the Pass Creek Canyon water gap area

Figure 10: Detailed map of the Pass Creek Canyon water gap area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 provides a detailed topographic map of the Pass Creek Canyon water gap area seen in less detail in figure 9. The map contour interval for figure 10 is 20 feet. Pass Creek flows in a north and northwest direction from the south edge of figure 10 (in section 5 near southeast corner of figure 10) to the Pass Creek Canyon water gap in section 26 and then turns to flow in a west direction to the west edge of figure 10 (slightly south of center). West of figure 10 Pass Creek turns to flow in a north and southwest direction to join the north oriented North Platte River. Pass Creek crosses the 7400-foot contour line as it enters the Pass Creek Canyon water gap area and crosses the 7300-foot contour line as it leaves the Pass Creek Canyon water gap area. Coad Mountain to the south of the water gap rises to 9454 feet. Elk Mountain elevations to the north of the water gap and seen in figure 10 rise to more than 10,400 feet. These elevations suggest the water gap is almost 2100 feet deep. An argument could be made that the water gap is even deeper because south of figure 10 Pennock Mountain rises to 9959 feet. If the Pennock Mountain elevation is used the water gap is almost 2600 feet deep. Regardless of how deep the water gap is the region east of the water gap  (the present day Pass Creek Basin) had to be at least as high the top of Coad Mountain and possibly as high as the top of Pennock Mountain at the time erosion of the water gap began. In other words the water gap depth documents 2100 to 2600 feet (or more) of erosion in the Pass Creek Basin area to the east of the water gap. The evidence seen figures 9 and 10 demonstrates massive erosion of the region on the north end of the Medicine Bow Mountains and documents that at one time there was a much higher erosion surface to the north of the Medicine Bow Mountains on which south oriented floodwaters could flow. Probably in addition to the deep flood flow erosion crustal warping raised the entire region and perhaps more localized crustal warping raised the Elk Mountain-Coad Mountain-Pennock Mountain ridge as west oriented flood flow eroded the deep west oriented Pass Creek Canyon water gap and the deep Oberg Pass wind gap. There are many additional details not addressed here, but this brief essay provides a framework future researchers can use for a more detailed understanding the origin of the northern Medicine Bow Mountains drainage routes and drainage divides.

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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