North Laramie River-Laramie River drainage divide area landform origins in the Laramie Mountains, USA

Authors

 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the North Laramie River-Laramie River drainage divide area in the Wyoming Laramie Mountains. The Laramie River flows in a north direction in the Laramie Basin between the Laramie Mountains to the east and north and the Medicine Bow Mountains to the west and upon approaching the Laramie Mountains southwest margin the Laramie River turns to flow in an east and northeast direction across the Laramie Mountains and then in an east and northeast direction to join the southeast oriented North Platte River. The North Laramie River originates in the Laramie Mountains and flows in a south direction to the southwest margin of the Laramie Mountains and then turns to flow in an east-northeast and east-southeast direction across the Laramie Mountains to join the east and northeast oriented Laramie River on the east side of the Laramie Mountains. West of the North Laramie River valley across the Laramie Mountains are southwest and west oriented streams draining to the northwest, west, and northwest oriented Medicine Bow River, which flows to the north oriented North Platte River west of the Laramie Mountains. North to south oriented through valleys in the Laramie Mountains link the east oriented North Laramie River valley with the east oriented Duck Creek valley (which drains to Laramie River) and the east oriented Duck Creek valley with the Laramie River valley to the south. A through valley west of the Laramie Mountains links the east-northeast and east-southeast oriented North Laramie River valley with southwest oriented Medicine Bow River tributary valleys. Valley orientations, through valleys, elbows of capture, barbed tributaries, and similar features are interpreted in the context of immense melt water floods from the western margin of a thick North American ice sheet. Floodwaters flowed from western Canada to and across Wyoming at a time when the Laramie Mountains were just beginning to emerge. Headward erosion of the Laramie River valley from the actively eroding southeast oriented North Platte River valley head captured south oriented flood channels in the Laramie Mountains and beheaded south oriented flood flow channels just west of the Laramie Mountains. Floodwaters on the north end of the beheaded flood flow channels reversed flow direction to create the north oriented Laramie River drainage route in the Laramie Basin. Headward erosion of the east oriented Duck Creek valley next captured flood flow moving to the newly eroded Laramie River valley and headward erosion of the North Laramie River valley then beheaded and reversed flood flow channels to the newly eroded Duck Creek valley. South and southeast oriented flood flow west of the Laramie Mountains was captured by these east oriented valleys and diverted across the emerging Laramie Mountains to the much deeper North Platte River valley. Headward erosion of the deep southeast oriented North Platte River valley around the northwest end of the Laramie Mountains then beheaded and reversed flood flow channels west of the Laramie Mountains and in several steps created the north oriented North Platte River drainage route west of the Laramie Mountains,. The reversal of flood flow on the present day north oriented North Platte River drainage route ended south and southeast oriented flood flow to the deep east oriented North Laramie River, Duck Creek, and Laramie River valleys across the Laramie Mountains.

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 North Laramie River-Laramie River drainage divide area landform origins in the Wyoming Laramie 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 North Laramie River-Laramie River drainage divide area landform evidence in the Wyoming Laramie Mountains will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

North Laramie River-Laramie River drainage divide area location map

Figure 1: North Laramie River-Laramie 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 North Laramie River-Laramie River drainage divide area in the Wyoming Laramie Mountains and illustrates a region in east-central Wyoming. The Laramie Mountains extend from just south of Casper in a southeast and south direction to the south center edge of figure 1. The North Platte River flows in a north, north-northeast, and northeast direction from Seminoe Reservoir (near southwest corner of figure 1) to Casper and then in an east, south, east, and southeast direction as it flows around the northwest end of the Laramie Mountains to the east edge of figure 1 (south of center). The Laramie River flows in a north-northeast direction from the south center edge of figure 1 to just north of Wheatland Reservoir where it turns to flow in an east, northeast, and east-northeast direction to join the North Platte River near the east edge of figure 1. The North Laramie River originates near the center of figure 1 and flows in a south direction to near the town of Garret where it turns to flow in an east-northeast and east-southeast direction to join the Laramie River on the east side of the Laramie Mountains. The Laramie River and the North Laramie River flow across the Laramie Mountains in deep valleys. The Medicine Bow River flows in a northeast direction from the south edge of figure 1 (west half-near town of Elk Mountain) to near the town of Medicine Bow and then turns to flow in a northwest, west, and northwest direction to join the north oriented North Platte River at Seminoe Reservoir. Rock Creek (unlabeled in figure 1) flows in a northeast direction from the south edge of figure 1 (west half) to the town of Rock River and then in a north and west direction to join the Medicine Bow River near the town of Medicine Bow. Sheep Creek originates near the center of figure 1 and flows in a south and southwest direction to join the south and west oriented Little Medicine Bow River (unlabeled in figure 1), which joins the Medicine Bow River near the town of Medicine Bow. The North Laramie River-Laramie River drainage divide area investigated in this essay is located south of the North Laramie River and north of the Laramie River and includes the Sheep Creek-North Laramie River drainage divide area and the north end of the Rock Creek-Laramie River drainage divide.

The Laramie River, North Laramie River, North Platte River, and tributary drainage routes developed during immense melt water floods from the western margin of a thick North American ice sheet. Floodwaters flowed from western Canada to and across Wyoming at a time when Wyoming mountain ranges were beginning to emerge. Wyoming mountain ranges emerged as floodwaters flowed across them and as ice sheet crustal warping raised the mountain ranges. Deep erosion of surrounding regions contributed significantly to the mountain range emergence. At first floodwaters could flow across the emerging mountain ranges and floodwaters did cross the emerging Laramie Mountains first in complexes of diverging and converging south oriented flood flow channels while deeper south oriented flood flow channels began to develop on either side of the emerging mountains. Headward erosion of the deep southeast oriented North Platte River valley captured south oriented flood flow along the east and northeast side of the emerging Laramie Mountains while headward erosion of deep east and northeast oriented tributary valleys into the emerging Laramie Mountains captured south oriented flood flow flowing along what is now the crest of the Laramie Mountains and subsequently captured flood flow moving along the southwest side of the emerging Laramie Mountains. Tributary valleys eroded headward across the emerging mountain mass in sequence from the south to the north. Floodwaters on north ends of beheaded flood flow channels reversed flow direction to flow to the much deeper beheading valleys. Headward erosion of the deep Laramie River valley across the emerging Laramie Mountains beheaded and reversed a major south oriented flood flow channel on the west side of the Laramie Mountains to create the north oriented Laramie River drainage route in the Laramie Basin. Headward of the North Laramie River valley across the Laramie Mountains captured south oriented flood flow moving to the newly eroded Laramie River valley and its actively eroding tributary valleys. Both the deep Laramie River and the deep North Laramie River valleys (and several of their tributary valleys) captured southeast and east oriented flood flow moving along the southwest side of the Laramie Mountains. Headward erosion of the deep southeast oriented North Platte River valley around the northwest end of the Laramie Mountains then beheaded and reversed flood flow channels west of the Laramie Mountains northwest end. In a series of steps the reversed flood flow created the north oriented North Platte River drainage route west of the Laramie Mountains and beheaded and reversed southeast and east oriented flood flow routes along the southwest side of the Laramie Mountains to create the northwest, west, and northwest oriented Medicine Bow River drainage route and other northwest and west oriented North Platte River tributary drainage routes.

Detailed location map for North Laramie River-Laramie River drainage divide area

Figure 2: Detailed location map North Laramie River-Laramie 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 North Laramie River–Laramie River drainage divide area in the Wyoming Laramie Mountains. Green colored areas are National Forest lands located in the Laramie Mountains. The North Platte River flows in a southeast direction across the northeast corner of figure 2. The Laramie River flows in a north-northeast direction to near the north end of Wheatland Reservoir and then turns to flow in an east, northeast, east, and northeast direction to the east edge of figure 2 (slightly north of center) and joins the North Platte River east of figure 2. Duck Creek originates in the region north of Wheatland Reservoir and flows in an east direction to join the northeast oriented Laramie River. Rabbit Creek and Luman Creek are east-southeast and southeast oriented Laramie River tributaries near the center of figure 2 while Marble Quarry Creek, Collins Creek, the Dry Laramie River, and Landis Creek are east oriented Laramie River tributaries just to the north. Toltec is a small community near the northwest corner of figure 2. The North Laramie River originates near Toltec and flows in a southwest and south direction to near the west center edge of figure 2 and then turns to flow in a northeast, south, east, and east-southeast direction to join the Laramie River near the small town of Uva (north of Wheatland). Sturgeon Creek is a north-northeast oriented tributary to the northeast oriented North Laramie River. South oriented tributaries to the North Laramie River from the north provide evidence headward erosion of the North Laramie River valley captured multiple south oriented drainage routes in the Laramie Mountains. North-northeast oriented North Laramie River tributary drainage routes were formed by reversals of flood flow on north ends of beheaded flood flow channels. The predominantly east orientation of the Laramie River and its tributaries as they cross the Laramie Mountains is the result of large volumes of east oriented flood flow moving to the much deeper southeast oriented North Platte River valley. The deep east and northeast oriented Laramie River and tributary valleys across the emerging Laramie Mountains captured larges volumes of flood flow moving along the southwest margin of the emerging Laramie Mountains. Uplift of mountains in Colorado south of the Laramie basin (on west side of the Laramie Mountains) was preventing floodwaters on the west side of the Laramie Mountains from moving in south directions, which enabled the deep east and northeast oriented Laramie River valley to behead and reverse flood flow channels in the Laramie Basin, which created the north oriented Laramie River drainage route south of figure 2.

Owen Creek-Ashley Creek drainage divide area

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

Figure 3 provides a topographic map of Owen Creek-Ashley Creek drainage divide area. The map contour interval for figure 3 is 20 meters. The North Laramie River flows in a northeast direction across the northwest corner of figure 3 and then flows in a south direction between Indian Head Rocks and Chimney Rock (near north edge of figure 3-east half) before turning to flow in an east direction to the east edge of figure 3 (near northeast corner). East of figure 3 the North Laramie River flows to the east and northeast oriented Laramie River. Davidson Flats is located near the west edge of figure 3 and Siebolt Creek flows in a north-northeast direction from Davidson Flats to join north-northeast and north oriented Sturgeon Creek, which joins the North Laramie River north of figure 3. Owen Creek originates west of Britania Mountain and flows in a north-northeast direction to the north center edge of figure 3 and joins the North Laramie River north of figure 3. Ashley Creek originates south of the Owen Creek headwaters and flows to the south edge of figure 3 (west of center) and south of figure 3 joins east oriented Duck Creek, which then flows to the northeast oriented Laramie River. A north to south oriented through valley on the west side of Britania Mountain links the north oriented Owen Creek valley with the south oriented Ashley Creek valley. The through valley floor elevation is between 2200 and 2220 meters. Elevations on the unnamed mountain to the west rise to more than 2400 meters while elevations on Britania Mountain rise to more than 2440 meters suggesting the through valley is approximately 200 meters deep. The through valley was eroded by a south oriented flood channel prior to headward erosion of the deeper North Laramie River valley north of figure 3. Headward erosion of the deep North Laramie River valley beheaded the south oriented flood flow channel causing floodwaters on the north end of the beheaded flood flow channel to reverse flow direction and to flow in a north direction to the much deeper North Laramie River valley. Tops of the mountains on either side of the through valley may represent the level of the erosion surface on which the south oriented floodwaters first flowed prior to the emergence of the Laramie Mountains. If so deep erosion on both the east and west sides of figure 3 has occurred since that time although the north to south oriented Laramie Mountains crest ridge in the center of figure 3 may also have been uplifted since that time. East oriented streams flowing to the east edge of figure 3 are flowing in valleys eroded by diverging and converging east oriented flood flow channels that once crossed the emerging Laramie Mountains. Headward erosion of the deeper North Laramie River valley in a series of steps captured flood flow routes supplying floodwaters to those east oriented valleys.

Detailed map of Owen Creek-Ashley Creek drainage divide area

Figure 4: Detailed map of Owen Creek-Ashely 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 Owen Creek-Ashley Creek drainage divide area seen in less detail in figure 3. The map contour interval for figure 4 is 40 feet. Owen Creek originates in section 31 and flows in a north-northeast direction to the north center edge of figure 4. North of figure 4 Owen Creek flows to the east oriented North Laramie River. Sturgeon Creek flows from section 36 (near west center edge of figure 4) to the north edge of figure 4 and north of figure 4 joins the North Laramie River. The Dry Laramie River originates in section 33 on the east side of Britania Mountain and flows in a north-northeast direction to the north edge of figure 4 (near northeast corner). North and east of figure 4 the Dry Laramie River turns to flow in a southeast, northeast, east, and southeast direction to join the east and northeast oriented Laramie River. Ashely Creek originates in section 32 and flows in a southwest and south direction to the south center edge of figure 4. South of figure 4 Ashley Creek flows to east oriented Duck Creek, which then flows to the east and northeast oriented Laramie River. A north to south oriented through valley in section 32 links the north oriented Owen Creek valley with the south oriented Ashley Creek valley. The through valley floor elevation is 7252 feet. The high point in section 31 to the west is 7969 feet and the high point on Britania Mountain to the east is more than 8080 feet suggesting the through valley is at least 700 feet deep. An even deeper north to south oriented through valley is located west of figure 4 and is seen in figures 5 and 6. These through valleys were eroded by south oriented flood flow prior to headward erosion of the deep east oriented North Laramie River valley to the north of figure 4. Headward erosion of the deep North Laramie River valley beheaded the south oriented flood flow channels and floodwaters on the north ends of the beheaded flood flow channels reversed flow direction to create north oriented North Laramie River tributary drainage routes.

North Laramie River-Duck Creek drainage divide area

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

Figure 5 illustrates the North Laramie River-Duck Creek drainage divide area south and west of figure 3 and there is an overlap area with figure 3. The map contour interval for figure 5 is 20 meters. The North Laramie River flows in a southeast and east direction from the northwest corner of figure 5 to the small community of Garrett and then flows in a northeast direction to the north edge of figure 5 (west of center). North and east of figure 5 the North Laramie River joins the east and northeast oriented Laramie River. Duck Creek flows in an east-northeast, southeast, northeast, and east-southeast direction from the southwest corner of figure 5 to the east edge of figure 5 (near southeast corner) and east of figure 5 joins the east and northeast oriented Laramie River. Davidson Flats is located in the east half of figure 5. Siebolt Creek flows in a north-northeast direction from Davidson Flats to the north edge of figure 5 (near northeast corner) and north of figure 5 joins the North Laramie River. Wallace Draw drains the south end of Davidson Flats to south oriented Mertz Draw, which drains to east-southeast oriented Duck Creek. Davidson Flats is located in a large north to south oriented through valley linking the north oriented Siebolt Creek valley with the south oriented Wallace Draw and Mertz Draw valleys. The through valley floor elevation in Davidson Flats is between 2160 and 2180 meters. Elevations to the west exceed 2420 meters at Pinto Rocks and as seen in figure 3 elevations to the east rise to more than 2440 meters. These elevations suggest the Davidson Flats through valley is at least 240 meters deep. This large through valley was eroded by south or south-southwest oriented flood flow prior to headward erosion of the deeper east oriented North Laramie River valley to the north. Headward erosion of the deep North Laramie River valley beheaded and reversed the flood flow to create the north oriented Siebolt Creek drainage route. The Davidson Flats through valley is located between two north to south oriented ridges that form the Laramie Mountains crest in this region. The Laramie Mountains crest ridges are lower in elevation in this region than to the south and in the north probably because large volumes of east oriented flood flow moved across the emerging Laramie Mountains in this region from the southwest side of the Laramie Mountains to reach the much deeper southeast oriented North Platte River valley east of the Laramie Mountains.

Detailed map of Siebolt Creek-Wallace Draw drainage divide area

Figure 6: Detailed map of Siebolt Creek-Wallace Draw 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 Siebolt Creek-Wallace Draw drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 40 feet except near the west edge where the contour interval is 20 feet. Brandel Mountain is a southeast to northeast oriented mountain straddling the west center edge of figure 6. Davidson Flats is located near the center of figure 6. Siebolt Creek flows in a north and north-northeast direction from near the center of figure 6 to the north center edge of figure 6 and north of figure 6 flows to the east oriented North Laramie River, which then flows to join the east and northeast oriented Laramie River. Wallace Draw originates in section 15 and drains in a west direction into section 16 where it turns to drain in a south direction to the south edge of figure 6 (west half). South of figure 6 Wallace Draw drains to south oriented Mertz Draw, which then drains to east oriented Duck Creek, which flows to the east and northeast oriented Laramie River. McFarlane Creek originates in the west half of section 1 and flows in a southwest direction into section 2 where it turns to flow in a south direction into section 11 where it turns again to flow in a southeast direction to the east edge of figure 6 (south half). East of figure 6 McFarlane Creek joins south oriented Ashley Creek to flow to east oriented Duck Creek. Through valleys in the Davidson Flats area link the north oriented Siebolt Creek valley with the south and southeast oriented McFarlane Creek and the south oriented Wallace Draw valley. The through valley floor elevations are between 7040 and 7080 feet. Elevations on Brandel Mountain to the west rise to more than 7740 feet. West of figure 6 elevations reach 8010 feet on Pinto Rocks. Elevations in section 31 near the northeast corner of figure 6 rise to 7989 feet. These elevations suggest the through valley could as much as 900 feet deep. The through valleys were eroded by two south oriented flood flow channels diverging from a south oriented flood flow channel on the present day north oriented Siebolt Creek alignment. Headward erosion of the deeper east oriented North Laramie River valley to the north of figure 6 beheaded and reversed the south oriented flood flow channel to create the north oriented Siebolt Creek drainage route.

Duck Creek-Laramie River drainage divide area

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

Figure 7 illustrates the Duck Creek-Laramie River drainage divide area south and east of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 7 is 20 meters. Duck Creek flows in an east-northeast, southeast, northeast, east-southeast, and east direction from the west edge of figure 7 (slightly north of center) to the east edge of figure 7 (north of center). Ashley Creek flows from near the northeast corner of figure 7 in a south direction in a 400-meter or deeper canyon between Reese Mountain to the east and Split Rock to the west from to join Duck Creek near the east edge of figure 7. This deep valley was eroded by south oriented flood flow prior to headward erosion of the deeper east oriented North Laramie River valley further to the north. Wallace Draw drains from the north edge of figure 7 (east of center) to Mertz Draw, which drains to east-southeast and east oriented Duck Creek. Further west south oriented North Fork flows to the southeast oriented Duck Creek segment and is linked by a north-south oriented through valley (north of figure 7 and seen in figure 5) with a north, west, and northwest oriented North Laramie River tributary valley. The Laramie River flows in a north direction from the south edge of figure 7 (west half) and once in figure 7 turns to flows in an east direction near the south edge of figure 7 to the east edge of figure 7. Wheatland Reservoir is located just south of the south edge of figure 7 and is located just east of the north oriented Laramie River. Duck Creek and the Laramie River flow from the west side of the Laramie Mountains in east directions to cross the Laramie Mountains in deep valleys or water gaps. The Laramie River, Duck Creek, and North Laramie River valleys across the Laramie Mountains are several hundred meters deep, with the exact depths depending on how and where the measurements are made. A north to south oriented through valley follows the south oriented North Fork valley from the north edge of figure 7 and continues in a south direction to the Laramie River and then to the south edge of figure 7. The road is located in the north to south oriented through valley, which in figure 7 links the southeast oriented Duck Creek valley segment with a southeast and northeast oriented Laramie River jog (and which south of figure 7 includes the Wheatland Reservoir location). Between Duck Creek and the Laramie River the through valley floor elevation is between 2160 and 2180 meters. Elevations west of the through valley rise to more than 2300 meters and much higher elevations are found in the Laramie Mountains to the east. In other words the through valley is at least 120 meters deep. The through valley was eroded by south oriented flood flow prior to headward erosion of the deeper east oriented Laramie River, Duck Creek, and North Laramie River valleys. Headward erosion of the deep Laramie River valley beheaded and reversed the flood flow channel to create the north and east oriented Laramie River drainage route in the Wheatland Reservoir region. Next headward erosion of the deep east oriented Duck Creek valley captured the south oriented flood flow. Headward erosion of the deep east oriented North Laramie River valley beheaded and reversed the south oriented flood flow routes to the newly eroded Duck Creek valley and this process continued as east and northeast oriented valleys eroding headward from the much deeper North Platte River valley beheaded and reversed south oriented flood flow channels flowing along the emerging Laramie Mountains’ crest.

Detailed map of Duck Creek-Laramie River drainage divide area

Figure 8: Detailed map of Duck Creek-Laramie River 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 Duck Creek-Laramie River drainage divide seen in less detail in figure 7. The map contour interval for figure 8 is 20 feet. The Laramie River flows in an east direction just south of figure 8, but crosses the south edge of figure 8 for a short distance (east of center). Duck Creek flows in an east direction north of figure 8, but crosses the north edge of figure 8 for a short distance (east of center). A north to south oriented through valley extends from near the north center edge of figure 8 to the south edge of figure 8 (west of center) and Wheatland Reservoir is located a short distance south of where the through valley crosses the south edge of figure 8. The Duck Creek-Laramie River drainage divide in the through valley is located in the north half of section 11 and has an elevation of between 7080 and 7100 feet. Elevations near the west edge of figure 8 (south half) rise to 7542 feet and much higher elevations are found in the Laramie Mountains to the east of figure 8 indicating the through valley is at least 440 feet deep. Many of the small hills or erosional residuals seen in figure 8 appear to have been streamlined by water erosion suggesting flood flow deeply eroded the entire region. The south oriented flood flow was first captured by headward erosion of the deep east and northeast oriented Laramie River valley from the actively eroding southeast oriented North Platte River valley on the east side of what were then the emerging Laramie Mountains. Next headward erosion of the east oriented Duck Creek valley from the actively eroding Laramie River valley captured the south oriented flood flow and diverted the floodwaters more directly to the newly eroded Laramie River valley. Floodwaters on the north end of the beheaded flow route reversed flow direction to create the short east and north oriented Duck Creek tributary drainage route seen is section 2.

Medicine Bow River-North Laramie River drainage divide area

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

Figure 9 illustrates the Medicine Bow River-North Laramie River drainage divide area north and west of figure 7 and there is an overlap area with figure 7. The map contour interval for figure 9 is 20 meters. The region seen in figure 9 is west of the Laramie Mountains and could be considered to be in the Laramie Basin. The North Laramie River flows in a south and east direction from the north edge of figure 9 (east half) to the east edge of figure 9 (north half) and east of figure 9 flows in an east-northeast and east-southeast direction across the Laramie Mountains to join the east and northeast oriented Laramie River. East and northeast oriented streams in the east half of figure 9 are tributaries to the North Laramie River. Bone Creek is the labeled south and southwest oriented stream in the west half of figure 9 and flows from the northwest quadrant of figure 9 to the west edge of figure 9 (south half). West of figure 9 Bone Creek joins west-southwest oriented Greasewood Creek, which then joins the south and west oriented Little Medicine Bow River to flow to the northwest, west, and northwest oriented Medicine Bow River, which then flows to the north oriented North Platte River on the west side of the Laramie Mountains. A broad through valley links the southwest oriented Bone Creek valley with east oriented Twentytwo Mile Draw valley, which drains to the east oriented North Laramie River valley. The through valley at its deepest point has an elevation of between 2140 and 2160 meters (compare this with elevations greater than 2400 meters along the Laramie Mountains crest ridge seen in earlier figures to the east). Elevations to the north and south of the through valley rise to more than 2220 meters suggesting the through valley is at least 60 meters deep. The through valley was eroded by northeast and east oriented flood flow moving from the present day northwest, west, and northwest oriented Medicine Bow River alignment to the east-northeast and east-southeast oriented North Laramie River valley. At that time floodwaters were still flowing in a south direction on the present day north oriented North Platte River alignment west of the Laramie Mountains and headward erosion of the deep North Laramie River valley across the emerging Laramie Mountains captured some of the south oriented flood flow from flood flow channels west 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 and in several steps created the north oriented North Platte River drainage route. The reversal of flood flow on the North Platte River alignment west of the Laramie Mountains also reversed flow directions on the northwest, west, and northwest oriented Medicine Bow River alignment, which in turn led to the reversal of flow on the Bone Creek alignment, which created the Bone Creek-North Laramie River drainage divide.

Sheep Creek-North Laramie River drainage divide area

Figure 10: Sheep Creek-North Laramie River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 provides a topographic map of the Sheep Creek-North Laramie River drainage divide area north of figure 9 and includes an overlap area with figure 9. The map contour interval for figure 10 is 20 meters. The North Laramie River flows in a south direction from the north edge of figure 10 (east half) and turns near the south edge of figure 10 to flow in an east-southeast direction to the southeast corner of figure 10. East of figure 10 the North Platte River flows in an east-northeast and east-southeast direction across the Laramie Mountains to join the east and northeast oriented Laramie River, which then joins the southeast oriented North Platte River. Sheep Creek flows in a south and southwest direction from the north edge of figure 10 (west half) to the west edge of figure 10 (south of center) and west of figure 10 flows to the south and west oriented Little Medicine Bow River, which then flows to the northwest, west, and northwest oriented Medicine Bow River, which in turn flows to the north oriented North Platte River on the west side of the Laramie Mountains. Mule Creek flows in a south, south-southwest, and west direction from the north center edge of figure 10 to join Sheep Creek near the point where sheep Creek turns to flow in a southwest direction. The south oriented North Laramie River, Mule Creek, and Sheep Creek drainage routes originated as south oriented flood flow channels, which at that time crossed the emerging Laramie Mountains to the north. At that time there was no deep North Platte River valley on the north and northeast flank of the Laramie Mountains and diverging and converging flood flow channels crossed the emerging mountain range. Headward erosion of the east oriented Laramie-North Laramie River valley across the emerging Laramie Mountains from the actively eroding and deep southeast oriented North Platte River valley on the east side of the Laramie Mountains captured the south oriented flood flow channels and diverted floodwaters in an east direction to the much deeper southeast oriented North Platte River valley. Headward erosion of the deep North Platte River valley around the northwest end of the emerging Laramie Mountains beheaded and reversed flood flow channels crossing the Laramie Mountains and then beheaded and reversed flood flow channels west of the northwest end of the Laramie Mountains to create the north oriented North Platte River drainage route. The reversal of flood flow on the North Platte River alignment west of the Laramie Mountains also reversed flood flow on the present day northwest, west, and northwest oriented Medicine Bow River alignment, which then captured south oriented flood flow on the Little Medicine Bow River alignment, which in turn captured the south oriented Sheep Creek and Mule Creek drainage routes to create the Sheep Creek-North Laramie River drainage divide seen in figure 10.

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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