Abstract:

This essay uses topographic map evidence to interpret landform origins in the Muddy Creek-Medicine Bow River drainage divide area in the Wyoming Shirley and Freezeout Mountains. Muddy Creek is a an east, southeast, and south oriented stream flowing from the Shirley Mountains around the Freezeout Mountains to the southwest and west-northwest oriented Little Medicine Bow River, which flows to the northwest, west, and northwest oriented Medicine Bow River, which in turn flows to the north, north-northeast, and southeast oriented North Platte River, which flows around the northwest end of the Laramie Mountains. North to south oriented through valleys link north oriented Muddy Creek tributary valleys with south oriented Medicine Bow River tributary valleys and a west to east oriented through valley south of the Freezeout Mountains links the west oriented Medicine Bow River valley with the south oriented Muddy Creek valley and with a west-southwest oriented Little Medicine Bow River tributary valley, which is aligned with the northeast and east oriented North Laramie River valley, which eventually drains to the southeast oriented North Platte River valley east of the Laramie Mountains. Through valleys, the entire Freezeout Mountains region, and the Shirley Mountains were eroded by immense south oriented melt water floods from the western margin of a thick North American ice sheet. Floodwaters flowed from western Canada to and across Wyoming at a time when Wyoming mountain ranges were emerging. Mountain ranges emerged as ice sheet related crustal warping raised the mountain ranges and as floodwaters deeply eroded surrounding valleys and basins. The north oriented North Platte River drainage route west of the Laramie Mountains originated as south oriented flood flow channels while the northwest, west, and northwest oriented Medicine Bow River drainage route south of the Freezeout and Shirley Mountains originated as a southeast, east, and southeast oriented flood flow channel moving floodwaters to deep valley crossing the emerging Laramie Mountains  to reach the much deeper southeast oriented North Platte River valley east of the Laramie Mountains. Headward erosion of the deep southeast oriented North Platte River valley around the northwest end of the Laramie Mountains beheaded and reversed flood flow channels west of the Laramie Mountains in several steps to create the north, north-northeast, and southeast oriented North Platte River drainage route seen today. For a time after reversal of flood flow on the north-northeast oriented North Platte River segment floodwaters may have moved in a north direction on the present day south oriented Muddy Creek alignment. Reversal of flood flow on the north oriented North Platte River segment west of the Shirley Mountains next beheaded and reversed southeast, east, and southeast oriented flood flow on the Medicine Bow River alignment to create the present day northwest, west, and northwest oriented Medicine Bow River drainage route south of the Freezeout and Shirley Mountains, which beheaded and reversed any north oriented flood flow on the Muddy Creek alignment to create the south oriented Muddy Creek drainage route.

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 Muddy Creek-Medicine Bow River drainage divide area landform origins in the Wyoming Shirley and Freezeout 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 Muddy Creek-Medicine Bow River drainage divide area landform evidence in the Wyoming Shirley and Freezeout Mountains will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Muddy Creek-Medicine Bow River drainage divide area location map

Figure 1: Muddy Creek-Medicine Bow 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 Muddy Creek-Medicine Bow River drainage divide area in the Wyoming Shirley and Freezeout Mountains and illustrates a region in south central Wyoming. The Laramie Mountains extend in a southeast and south direction from near the north center edge of figure 1 to the south edge of figure 1 (east of Laramie). The Medicine Bow Mountains extend in a south-southeast direction from the south center region of figure 1 across the south edge of figure 1 and into northern Colorado. The North Platte River flows from the south edge of figure 1 on the west side of the Medicine Bow Mountains in a north-northwest direction and north of highway 80 turns in a northeast direction to enter Seminoe Reservoir. From Seminoe Reservoir the North Platte River flows in a north and north-northeast direction to Casper at the northwest end of the Laramie Mountains and then turns to flow in an east, south, and southeast direction around the Laramie Mountains to flow in a southeast direction to the east edge of figure 1 (north of center). The Medicine Bow River originates in the northern Medicine Bow Mountains and flows in a north direction to the town of Elk Mountain. From Elk Mountain the Medicine Bow River flows in a northeast and northwest direction to the town of Medicine Bow and then in a northwest, west, and northwest direction to join the north oriented North Platte River at Seminoe Reservoir. The Shirley Mountains are north of the west oriented Medicine Bow River segment and are located near the center of figure 1. Muddy Creek originates in the northern Shirley Mountains and flows in an east, southeast, and south direction to join the south and west oriented Little Medicine Bow River (not labeled in figure 1), which joins the northwest, west, and northwest oriented Medicine Bow River near the town of Medicine Bow. The Freezeout Mountains are not shown on figure 1, but are located between the Shirley Mountains and the town of Medicine Bow. The Laramie River flows in a northeast direction from the south edge of figure 1 (east of center) to the city of Laramie and then in a north direction to Wheatland Reservoir. North of Wheatland Reservoir the Laramie River turns to flow in a northeast direction across the Laramie Mountains (in a deep valley) and then in an east-northeast direction to east edge of figure 1 and joins the southeast oriented North Platte River east of figure 1. The North Laramie River is a south, northeast, and east oriented Laramie River tributary and also crosses the Laramie in a deep valley. The region between the Medicine Bow Mountains and the Laramie Mountains is known as the Laramie Basin. The Muddy Creek-Medicine Bow River drainage divide area investigated in this essay is primarily located south and west of Muddy Creek, east of the Shirley Mountains, and north of the Medicine Bow River.

The North Platte River drainage network evolved during immense melt water floods at a time when Wyoming mountain ranges were emerging. Floodwaters flowed from the western margin of a thick North American ice sheet in western Canada to and across Wyoming. Mountain ranges emerged as ice sheet related crustal warping raised the mountain ranges and as floodwaters deeply eroded surrounding basins and valleys. At first floodwaters flowed across what are today high mountain ranges, but later floodwaters were channeled into deep valleys crossing the mountain ranges and/or into deep flood flow channels surrounding the emerging mountain masses. The north oriented North Platte River drainage route west of the Laramie, Shirley, and Medicine Bow Mountains originated as south oriented flood flow channels while the north oriented Laramie River drainage route between the Medicine Bow and Laramie Mountains also originated as south oriented flood flow channels. A much deeper southeast oriented North Platte River valley on the east side of the emerging Laramie Mountains eroded headward to capture south oriented flood flow and to divert floodwaters to the evolving Mississippi River drainage system. Northeast oriented tributary valleys eroded headward from the actively eroding southeast oriented North Platte River valley head to capture south oriented flood flow west of the actively eroding valley head. Headward erosion of deep northeast valleys across the emerging Laramie Mountains captured south oriented flood flow in the Laramie Basin, which included south oriented flood flow moving between the emerging Shirley and Laramie Mountains. Floodwaters on north ends of beheaded flood flow channels reversed flow direction to flow to the deeper northeast oriented valleys and then to the newly eroded southeast oriented North Platte River valley and in the process created the north oriented Laramie River drainage route. Headward erosion of the deep southeast oriented North Platte River valley around the northwest end of the Laramie Mountains next began to behead and reverse flood flow channels on the present day north oriented North Platte River drainage route. This beheading and reversal process took place in multiple steps with flood flow on each segments of the North Platte River being beheaded and reversed in sequence, generally from north to south. The reversal of flood flow on the North Platte River alignment also reversed flood flow on the present day northwest, west, and northwest oriented Medicine Bow River alignment to create the north, northeast, northwest, west, and northwest oriented Medicine Bow River drainage route seen today. Crustal warping that was raising the mountain ranges and the entire region probably greatly aided in the flood flow reversal process.

Detailed location map for Muddy Creek-Medicine Bow River drainage divide area

Figure 2: Detailed location map for Muddy Creek-Medicine Bow 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 Muddy Creek-Medicine Bow River drainage divide area in the Wyoming Shirley and Freezeout Mountains. The North Platte River flows in a northeast direction from near the southwest corner of figure 2 into north oriented Seminoe Reservoir and then flows in a north direction to the north edge of figure 2 (near northwest corner). North of figure 2 the North Platte River turns to flow in a north-northeast direction to the northwest end of the Laramie Mountains and then flows around the Laramie Mountains in an east, south, and southeast direction. The Medicine Bow River flows in a north-northeast and west direction from the south edge of figure 2 to the town of Medicine Bow (near southeast corner of figure 2). From Medicine Bow the Medicine Bow River flows in a northwest, west, and northwest direction to join the north oriented North Platte River at Seminoe Reservoir. The Little Medicine Bow River flows in a south direction from the north edge of figure 2 (east half-near northeast corner) to the southeast quadrant of figure 2 and then turns to flow in a southwest and west-northwest direction (north of the town of Medicine Bow) to join the northwest oriented Medicine Bow River (south of the Freezeout Mountains). Muddy Creek originates on the north side of the Shirley Mountains and flows in an east, south-southeast, and south direction to join the southwest and west-northwest oriented Little Medicine Bow River, which flows to northwest, west, and northwest oriented Medicine Bow River. Most Muddy Creek tributaries shown in figure 2 are oriented in north or northeast directions. Labeled tributaries include northeast and north oriented First Ranch Creek and northeast and north-northeast oriented House Creek. Difficulty Creek is a southeast and south-southwest oriented Medicine Bow River tributary originating at the east end of the Shirley Mountains and then flowing along the west side of the Freezeout Mountains. West of the Muddy Creek headwaters the west oriented Sage Creek drainage system drains the northern Shirley Mountains to the north oriented North Platte River.

Muddy Creek-Difficulty Creek drainage divide area

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

Figure 3 provides a topographic map of Muddy Creek-Difficulty Creek drainage divide area. The map contour interval for figure 3 is 20 meters. The Shirley Mountains are the upland region in the west half of figure 3. Muddy Creek is formed near the north center edge of figure 3 at the confluence of northeast and east oriented Quealy Creek, north-northeast and east-northeast oriented Lisenby Creek, and north-northeast oriented Sullivan Creek and then flows in an east direction near the north edge of figure 3 to the east edge of figure 3 (near northeast corner). East of figure 3 Muddy Creek turns to flow in a south-southeast and south direction to join the southwest and west-northwest oriented Little Medicine Bow River, which then joins the northwest, west, and northwest oriented Medicine Bow River. First Ranch Creek originates on the most eastern end of the Shirley Mountains upland surface and flows in a northeast, north, and north-northeast direction to join Muddy Creek slightly west of Point of Rocks. Difficulty Creek originates south of the northeast oriented First Ranch Creek drainage route (just east of the east end of the Shirley Mountains upland surface) and flows in a southeast and south direction on the west side of Little Basin to the south edge of figure 3. South of figure 3 Difficulty Creek flows in south-southwest direction to join the west and northwest oriented Medicine Bow River, which flows to the north oriented North Platte River. A deep northwest to southeast oriented through valley between the Shirley Mountains to the west and Pine Hill to the east links the northeast oriented First Ranch Creek valley with the southeast oriented Difficulty Creek valley. The through valley orientation appears to be determined by the orientation of the regional geologic structures, but the through valley also appears to be a water-eroded valley. The through valley floor elevation is between 2280 and 2300 meters. The high point on Pine Hill to the east is shown as being 2526 meters and elevations in the Shirley Mountains to the west exceed 2600 meters suggesting the through is at least 226 meters deep. The through valley was eroded by south or southeast oriented flood flow moving to what was probably a southeast and east oriented flood flow channel on the present day northwest and west oriented Medicine Bow River alignment with water then moving across the northern Laramie Basin and the emerging Laramie Mountains to the much deeper southeast oriented North Platte River valley east of the Laramie Mountains. Initially floodwaters were flowing on an erosion surface equivalent in elevation to the present-day Shirley Mountains upland surface elevation, although the Shirley Mountains and the entire region may have been uplifted since that time. Headward erosion of the deep east oriented Muddy Creek valley beheaded and reversed south oriented flood flow on the present day north oriented First Ranch Creek alignment to create the north and north-northeast oriented First Ranch Creek drainage route and then the deeper northeast oriented First Ranch Creek valley eroded headward across the southeast oriented flood flow moving to the southeast oriented Difficulty Creek valley.

Detailed map of First Ranch Creek-Difficulty Creek drainage divide area

Figure 4: Detailed map of First Ranch Creek-Difficulty 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 First Ranch Creek-Difficulty Creek drainage divide area seen in less detail in figure 3. The map contour interval for figure 4 is 20 feet. First Ranch Creek originates in the north half of section 14 (near southwest corner of figure 4) and flows in an east-northeast and north-northeast direction to the north edge of figure 4 (slightly east of center). North of figure 4 First Ranch Creek flows in a north and north-northeast direction to join east oriented Muddy Creek. Difficulty Creek originates in the southeast quadrant of section 7 and flows in a southeast direction to the south edge of figure 4 in section 21. Southwest, south, and southwest oriented Rock Creek (a relatively short stream) joins Difficulty Creek south of figure 4 and Difficulty Creek then flows in a south, southeast, and south-southwest direction to join the west and northwest oriented Medicine Bow River. A southeast oriented Rock Creek tributary valley is located north and east of the southeast oriented Difficulty Creek valley and is bounded by northwest to southeast oriented hogback ridges. These hogback ridges suggest the Difficulty Creek and the Rock Creek tributary valley orientations are determined by the underlying geologic structures, but Rock Creek has also eroded a water gap across the southern hogback ridge near the corner of sections 15, 16, 21, and 22, which provides evidence the valleys are water-eroded valleys. The northeast oriented First Ranch Creek valley is linked in the northeast quadrant of section 7 by through valleys with the southeast oriented Difficulty Creek valley and with the southeast oriented Rock Creek tributary valley. The northeastern through valley floor elevation is between 7480 and 7500 feet while the southwestern through valley floor elevation is between 7520 and 7540 feet. The hogback ridge between the two the through valleys rises to between 7580 and 7600 feet, which suggests the two through valleys are really two deeper channels in what was a much broader southeast oriented valley. The east side of the broader through valley is defined by Pine Hill, which rises to 8288 feet just east of figure 4. The broader through valley west wall is defined by the Shirley Mountains, which rise to 8387 feet in section 18 and to much higher elevations further to the west. These elevations suggest the broader through valley at its deepest points is almost 800 feet deep. South-southwest oriented through valleys cross the Shirley Mountains upland surface west of figure 4 (see figure 3) and once crossed the region north and east of the Shirley Mountains northeast-facing escarpment in figure 4. Headward erosion of the much deeper southeast oriented flood flow channel (the broad through valley) on the Difficulty Creek alignment captured the south-southwest oriented flood flow and diverted the floodwaters in a southeast direction. Next headward erosion of the still deeper east oriented Muddy Creek valley beheaded and reversed south oriented flood routes to the newly eroded southeast oriented Difficulty Creek valley to create the north-northeast and north oriented First Ranch Creek drainage route.

Muddy Creek-Smith Creek drainage divide area

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

Figure 5 illustrates a topographic map of the Muddy Creek-Smith Creek drainage divide area east of figure 3 and includes an overlap area with figure 3. The map contour interval for figure 5 is 20 meters. The Freezeout Mountains are located in the south center area of figure 5. Smith Creek Rim is located along the west side of the north end of the Freezeout Mountains. Pine Hill is located along the west center edge of figure 5 and is west of Smith Creek Rim. Smith Creek originates in the basin just west of Smith Creek Rim and flows in a south and southwest direction to near the southwest corner of figure 5. South and west of figure 5 Smith Creek flows to south-southwest oriented Difficulty Creek, which then flows to the west and northwest oriented Medicine Bow River. Muddy Creek flows in an east and east-southeast direction from the west edge of figure 5 (near northwest corner) into the east half of figure 5 and then turns to flow in a south-southwest, south-southeast, and south direction to the south edge of figure 5 (near southeast corner). Cameron Creek originates in the region east of Pine Hill and north and west of the Smith Creek headwaters and flows in a north and northeast direction to join east oriented Muddy Creek in the north center region of figure 5. A north to south oriented through valley links the north oriented Cameron Creek headwaters valley with the south oriented Smith Creek valley. The through valley floor elevation is between 2240 and 2260 meters. Pine Hill to the west rises to 2526 meters and Windy Hill to the southeast (near south edge of figure 5) rises to 2540 meters. These elevations suggest the through valley is 260 meters deep. Hogback ridges bound the through valley and the valley orientation is structurally controlled, but the through valley is a water-eroded valley. Floodwaters in this region first flowed on an erosion surface at least as high if not higher than the tops of Pine Hill and Windy Hill. At that time there was no deep east oriented Muddy Creek valley to the north and floodwaters were still flowing in a south direction on the present day north oriented North Platte River alignment. The south oriented through valley was eroded headward from a deeper east or west oriented valley on the present day northwest, west and, northwest Medicine Bow River alignment to the south of figure 5. Next headward erosion of the deep east oriented Muddy Creek valley beheaded and reversed the south oriented flood flow to create the north oriented Cameron Creek drainage route. Other north to south oriented through valleys can be seen in figure 5. For example between Windy Hill and Battle Mountain near the south edge of figure 5 there is a 200-meter plus deep north to south oriented through valley, which was beheaded by headward erosion of the northeast oriented Shearing Pen Draw valley. Geologic structures in the Freezeout Mountains area complicated valley orientations, but the through valleys are all water-eroded and were eroded by south oriented flood flow.

Detailed map of Cameron Creek-Smith Creek drainage divide area

Figure 6: Detailed map of Cameron Creek-Smith 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 Cameron Creek-Smith Creek drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 20 feet. Pine Hill is located along the west edge of figure 6 and the Freezeout Mountains are located in the east half of figure 6. Cameron Creek originates in north half of section 7 (near center of figure 6) and flows in an east, northeast, and north direction to the north center edge of figure 6. North of figure 6 Cameron Creek turns to flow in a northeast direction to join east, southeast, and south oriented Muddy Creek. Smith Creek originates in the southeast quadrant of section 7 and flows in an east and south direction to the south edge of figure 6 (east of center). South of figure 6 Smith Creek turns to flow in a southeast direction to join south-southwest oriented Difficulty Creek, which then flows to the west and northwest oriented Medicine Bow River. A deep north to south oriented through valley extends across the center of figure 6 and is the eroded crest of a large north to south oriented anticline or elongated dome. Hogback ridges in the Freezeout Mountains dip to the east while the Pine Hill hogback ridge dips to the west. The through valley floor elevation at the Cameron Creek-Smith Creek drainage divide in section 7 is between 7360 and 7380 feet. The high point on the Pine Hill hogback ridge in section 1 is 8128 feet and the high point seen near the north edge of section 8 to the east is 7817 feet. South and east of figure 6 Windy Hill rises to 8332 feet. Depending on which elevations are used the Cameron Creek-Smith Creek through valley could be 420 or 750 feet deep or even deeper. The through valley is a water-eroded valley and was eroded by south oriented flood flow crossing the region prior to headward erosion of the deep east oriented Muddy Creek valley north of figure 6. Initially floodwaters flowed on an erosion surface equivalent in elevation to the highest points in figure 6, although crustal warping may have altered elevations of those highest points since that time. It is possible the anticline was being formed by crustal warping that occurred as floodwaters flowed across the region, and it is also possible the anticline was formed prior to the melt water flood flow. In either case the south oriented floodwaters eroded the north to south oriented through valley and then were captured by headward erosion of the deep east oriented Muddy Creek valley north of figure 6. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented Cameron Creek drainage route.

Cottonwood Creek-Sledge Creek drainage divide area

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

Figure 7 illustrates the Cottonwood Creek-Sledge Creek drainage divide area south of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 7 is 20 meters. Muddy Creek flows in a south-southeast and south direction from the north edge of figure 7 (east half) to the south edge of figure 7 (near south-east corner) and south of figure 7 joins the southwest and west-northwest oriented Little Medicine Bow River to flow to the northwest, west, and northwest oriented Medicine Bow River, which flows to the north and southeast oriented North Platte River. Cottonwood Creek originates near the center of figure 7 and flows in an east, south, and east direction to join Muddy Creek in the southeast quadrant of figure 7. Shearing Pen Draw originates in the north center area of figure 7 and drains in a northeast and north-northeast direction to the north edge of figure 7 (east half-west of Muddy Creek) and joins Muddy Creek as a barbed tributary north of figure 7. Difficulty Creek flows in a southeast and south-southwest direction from the west edge of figure 7 (north of center) to the west edge of figure 7 (south half) and west and south of figure 7 joins the west and northwest oriented Medicine Bow River. Smith Creek originates on the west side of Smith Creek Rim (west of the north center edge of figure 7) and flows in a south and southwest direction to join Difficulty Creek south of Little Basin. Red Draw originates in the Freezeout Mountains and drains in a southwest direction to join Difficulty Creek in the southwest quadrant of figure 7. Sledge Creek originates south of Windy Hill (near center of figure 7) and flows in a south, southwest, and south direction to the south edge of figure 7 (near southwest corner) and south of figure 7 joins the west and northwest oriented Medicine Bow River. Numerous through valleys, water gaps, and wind gaps can be seen in the Freezeout Mountains region of figure 7. These through valleys, water gaps, and wind gaps were eroded as south oriented floodwaters flowed across the region. Many of the present day drainage routes and through valley orientations were determined by the orientations of the Freezeout Mountains structures, but there are also through valleys, water gaps, and wind gaps eroded across the hogback ridges. Valleys eroded across the structures had to be initiated when the Freezeout Mountains structures did not stand high above surrounding regions. In other words the valleys were initiated by floodwaters flowing on an erosion surface at least as high, if not higher, than the highest points in the Freezeout Mountains today (although the Freezeout Mountains and/or the entire region may have been uplifted since that time). One of the deeper through valleys is located south of Windy Hill and links the east oriented Cottonwood Creek valley with the southwest and south oriented Sledge Creek valley. The through valley floor elevation is between 2240 and 2260 meters. Windy Hill to the north rises to 2540 meters and the hogback ridge to the south rises to at least 2460 meters suggesting the through valley is at least 200 meters deep. Pete’s Gap to the south is classic water gap as is the south oriented Sledge Creek valley near the southwest corner of figure 7.

Detailed map of Smith Creek-Sledge Creek drainage divide area

Figure 8: Detailed map of Smith Creek-Sledge 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 Smith Creek-Sledge Creek drainage divide area seen is less detail in figure 7. The map contour interval for figure 8 is 20 feet. Smith Creek flows in a west-southwest direction from near the north center edge of figure 8 to the west edge of figure 8 (north half) and west of figure 8 flows in a southwest direction to join south-southwest oriented Difficulty Creek, which flows to the west and northwest oriented Medicine Bow River. A west-northwest oriented Smith Creek tributary flows from near the corner of sections 21, 22, 27, and 28 to join Smith Creek in section 20. Shearing Pen Draw drains in an east direction from near the corner of sections 22, 23, 26, and 27 to the east edge of figure 8 (near northeast corner) and east and north of figure 8 turns to drain in a northeast and north-northeast direction to join southeast oriented Muddy Creek as a barbed tributary. Windy Hill is located in the west half of section 34 and a south oriented Sledge Creek tributary originates in section 33 to the west of Windy Hill. A south-southwest oriented through valley in section 28 links the south oriented Sledge Creek tributary valley with the west-northwest oriented Smith Creek tributary valley. The through valley orientation is located along the eroded crest of an anticline and adjacent through valleys appear to be located in synclinal troughs. Hogback ridges seen in figure 8 provide evidence of sedimentary strata that were eroded from the region. At one time those missing rock layers extended across the region and south oriented floodwaters flowed on an erosion surface as high, or higher, than the top of Windy Hill. Whether the geologic structures were buried beneath that erosion surface or were formed as floodwaters eroded the region does not matter. What matters is massive erosion took place and floodwaters responsible for the erosion were primarily flowing in a south direction to reach a deeper west (or east) oriented valley to the south of figure 8 on the present day northwest, west, and northwest oriented Medicine Bow River alignment. Floodwaters eroded the easiest to erode rock layers, which preserved the hogback ridges consisting of more resistant rock layers. A west to east oriented through valley near the northeast corner of figure 8 links the west-northwest oriented Smith Creek tributary valley with the east, northeast, and north-northeast oriented Shearing Pen Draw valley. The through valley floor elevation is 7696 feet. Elevations in section 22 to the north rise to 7896 feet suggesting the through valley is at least 200 feet deep. The through valley provides evidence of what may have been diverging and converging flood flow channels surrounding the high Windy Hill hogback ridge.

Little Medicine Bow River-Medicine Bow River drainage divide area

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

Figure 9 illustrates the Little Medicine Bow River-Medicine Bow River drainage divide area south and east of figure 7 and there is an overlap area with figure 7. The map contour interval for figure 9 is 20 meters. The Medicine Bow River flows in a north-northwest and west direction from the south edge of figure 9 (west half) to the west edge of figure 9 (south of center). West of figure 9 the Medicine Bow River flows in a west and northwest direction to join the north, north-northeast, and southeast oriented North Platte River. The Little Medicine Bow River flows in a south direction from the north edge of figure 9 (between TB Flats and the county line) and once in the southeast quadrant of figure 9 turns to flow in a southwest and west-northwest direction to join the north-northwest oriented Medicine Bow River (south of Oil Springs). Muddy Creek flows in a south direction from the north edge of figure 9 (east of center and west of TB Flats) to join the southwest oriented Little Medicine Bow River. Greasewood Creek is the west-southwest oriented stream joining the Little Medicine Bow River near the elbow of capture where the south oriented Medicine Bow River turns to flow in a southwest direction. East of figure 9 the west-southwest oriented Greasewood Creek valley is aligned with northeast oriented tributaries to the northeast and east oriented North Laramie River, which flows across the Laramie Mountains in a deep valley to join the Laramie River, which then joins the southeast oriented North Platte River. At one time south oriented floodwaters on the present day south oriented Little Medicine Bow River and Muddy Creek alignments probably joined an east oriented flood flow channel on the Greasewood Creek alignment to flow in an east-northeast, northeast, and east direction across the emerging Laramie Mountains to a much deeper southeast oriented North Platte River valley located east of the Laramie Mountains. Headward erosion of the deep southeast oriented North Platte River valley around the northwest end of the Laramie Mountains beheaded and reversed flood flow channels west of the Laramie Mountains including flood flow channels on the south oriented Muddy Creek and Little Medicine Bow River alignments. It is possible floodwaters flowed in an and east and north direction on what is today the south, southwest, and west-northwest oriented Little Medicine Bow River alignment to the newly reversed north-northeast oriented North Platte River segment prior to the reversal of flood flow on the north oriented North Platte River segment west of figure 9 (evidence supporting such a possibility is not shown in this essay). However when the North Platte River segment west of figure 9 was beheaded and reversed floodwaters on the Medicine Bow River alignment were also beheaded and reversed to create the present day northwest, west, and northwest oriented Medicine Bow River drainage route. If floodwaters were flowing in a north direction on the present day south oriented Little Medicine Bow River alignment the reversal of flood flow on the Medicine Bow River alignment beheaded and reversed those north oriented floodwaters to create the south oriented Little Medicine Bow River and Muddy Creek drainage routes seen today.

Detailed map of Muddy Creek-Medicine Bow River drainage divide area

Figure 10: Detailed map of Muddy Creek-Medicine Bow 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 Muddy Creek-Medicine Bow River drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 20 feet. The Little Medicine Bow River flows in a south-southwest direction across the southeast corner of figure 10. South and west of figure 10 the Little Medicine Bow River flows in a southwest, northwest, and west direction to join the northwest, west, and northwest oriented Medicine Bow River, which then joins the north, north-northeast, and southeast oriented North Platte River. Muddy Creek can be seen flowing in a south direction near the northeast corner of figure 10 and joins the Little Medicine River east of figure 10. The southwest and west oriented stream in the southwest quadrant of figure 10 and north of Pine Butte west of figure 10 flows to the northwest, west, and northwest oriented Medicine Bow River.  The west oriented stream in the northwest quadrant of figure 10 west of figure 10 turns in a southwest direction to join the Medicine Bow River. A large depression in sections 27, 28, 33, and 34 is probably a sinkhole, which suggests the underlying bedrock may be limestone. Flattop Mountain is a high point north of the south center edge of figure 10 and reaches an elevation of 7076 feet (Pine Butte to the west rises to 7162 feet). While complicated by the depression or sinkhole a west to east oriented through valley links the west oriented Medicine Bow River tributary valleys with the south oriented Muddy Creek valley. The through valley floor elevation is between 6820 and 6840 feet. North of figure 10 elevations in the Freezeout Mountains exceed 7500 feet suggesting the through valley depth may range from about 240 feet (if the Flattop Mountain elevation is used) to more than 320 feet if the Pine Butte elevation is used. The through valley was probably first eroded by east oriented flood flow moving in an east direction to and across the Laramie Mountains to reach what was at that time the much deeper southeast oriented North Platte River valley east of the Laramie Mountains. A reversal of flood flow on the north-northeast oriented North Platte River segment north of figure 10 beheaded and reversed the south oriented flood flow channels on the present day south oriented Muddy Creek and Little Medicine Bow River alignments east of figure 10. It is possible that for a time east oriented flood flow moving across figure 10 turned to flow in a north direction to reach the newly reversed north-northeast oriented North Platte River valley north of figure 10. Headward erosion of the deep north-northeast oriented North Platte River valley next beheaded and reversed flood flow on the North Platte River segment west of figure 10 to create a north oriented North Platte River segment. That reversal of flood flow reversed east oriented flood flow in figure 10, to create a west oriented flood flow channel. West and northwest oriented flood flow routes south of figure 10 were able to capture more floodwaters and to erode deeper valleys, which are today the southwest, northwest, and west oriented Little Medicine Bow River and northwest oriented Medicine Bow River valleys.

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.