Medicine Bow River-Laramie River drainage divide area landform origins between the Wyoming Medicine Bow and Laramie Mountains, USA

Authors

 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the Medicine Bow River-Laramie River drainage divide area between the Wyoming Medicine Bow and Laramie Mountains. The Laramie Mountains extends in a southeast and south direction from central Wyoming to the Wyoming-Colorado state line. The Laramie Basin is located west and south of the Laramie Mountains. The Medicine Bow Mountains are located west of the Laramie Basin and extend in a south-southeast direction across state line into northern Colorado. The North Platte River flows in a north-northwest direction west of the Medicine Bow Mountains and then in a north and northeast direction to the Laramie Mountains northwest end where the North Platte River turns to flow in an east and southeast direction. The Laramie River originates near the south end of the Medicine Bow Mountains and flows in a north and northeast direction on the east side of the Medicine Bow Mountains into and across the Laramie Basin before turning in an east and northeast direction to flow in a deep valley across the Laramie Mountains to join the southeast oriented North Platte River. The Medicine Bow River originates high in the Medicine Bow Mountains and flows in a north direction to the north end of Medicine Bow Mountains and then turns in a northeast and northwest direction to join the north oriented North Platte River. Rock Creek is a north, northeast, and northwest oriented Medicine Bow River tributary located east of the Medicine Bow River and which almost joins the Laramie River in the Laramie Basin before turning to flow in a northwest direction to join the Medicine Bow River. Drainage routes in the Medicine Bow River-Laramie River drainage divide area north of the Medicine Bow Mountains developed during immense melt water floods from the western margin of a thick North American ice sheet with floodwaters flowing from western Canada to and across Wyoming at a time when Wyoming mountain ranges were just beginning to emerge. South oriented floodwaters on the present day north oriented North Platte River alignment split in the region north of the emerging Medicine Bow Mountains with one of the diverging flood flow channel continuing in a south-southeast direction on the present day north-northwest oriented North Platte River alignment and another diverging flood flow channel leading in a southeast direction into the Laramie Basin where at least some of the floodwaters flowed in an east direction across the emerging Laramie Mountains to reach the much deeper southeast oriented North Platte River valley, which was eroding headward along the east side of the Laramie Mountains. Headward erosion of the that deep southeast oriented valley around the northwest end of the Laramie Mountains beheaded south oriented flood flow channels west of the Laramie Mountains. Floodwaters on north ends of the beheaded flood flow channels reversed flow direction to flow to the much deeper east and southeast oriented valley and to create the present day north, east, and southeast oriented North Platte River drainage route. The North Platte River flood flow reversal beheaded the southeast oriented flood flow route to the Laramie Basin and then eastward across the emerging Laramie Mountains.  Floodwaters on the northwest end of  the beheaded flood flow channel reversed flow to flow to the newly reversed North Platte River drainage route and to create the northwest oriented Medicine Bow River and Rock Creek drainage routes. Flood flow reversals were probably greatly aided by ice sheet related crustal warping that was raising the emerging mountain ranges and the entire southeast Wyoming region as floodwaters flowed across Wyoming.

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

Medicine Bow River-Laramie River drainage divide area location map

Figure 1: Medicine Bow 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 Medicine Bow River-Laramie River drainage divide area between the Medicine Bow and Laramie Mountains and illustrates a region in southeast Wyoming. The Laramie Mountains extend in a southeast and south direction from the north edge of figure 1 (west of center) to the south edge of figure 1 (slightly east of center). The Medicine Bow Mountains extend in a south-southeast direction across the south edge of the southwest quadrant of figure 1. The North Platte River flows in a north-northwest direction along the west side of the Medicine Bow Mountains into the west center area of figure 1 and then flows in a northeast, north, and north-northeast direction to the north edge of figure 1 (west half). North of figure 1 the North Platte River flows around the northwest end of the Laramie Mountains and then enters figure 1 again to flow in a southeast direction from the north edge of figure 1 (east of center) to the east edge of figure 1 (north of center). The Medicine Bow River originates at 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 direction to join the north oriented North Platte River at Seminoe Reservoir. Rock Creek (unlabeled in figure 1) originates east of the Medicine Bow River headwaters and flows in a north and northeast direction to the towns of McFadden and Rock River before turning to flow in a north and northwest direction to join the Medicine Bow River near the town of Medicine Bow. The Laramie River flows in a north and northeast direction from the south edge of figure (west half-but on east side of Medicine Bow Mountains) to Laramie and then flows in a north-northwest and north-northeast direction to Wheatland Reservoir. North of Wheatland Reservoir the Laramie River turns to flow in an east and northeast direction across the Laramie Mountains and continues in a northeast direction to join the southeast oriented North Platte River near the town of Fort Laramie. The Medicine Bow River-Laramie River drainage divide between the Medicine Bow Mountains and the Laramie Mountains investigated in this essay is located primarily west of the Laramie River and east of Rock Creek and extends from the northeast end of the Medicine Bow Mountains to where the Laramie River begins to cross the Laramie Mountains and is located at the northwest end of the Laramie Basin, which is located between the Medicine Bow Mountains and the Laramie Mountains.

The North Platte River and Laramie River drainage systems developed during immense melt water floods at a time when the Medicine Bow and Laramie Mountains were just beginning to emerge. Floodwaters were derived from the western margin of a thick North American ice sheet and flowed from western Canada to and across the emerging Laramie and Medicine Bow Mountains. The mountain ranges emerged as floodwaters deeply eroded the surrounding valleys, basins, and other regions and as ice sheet related crustal warping raised the mountain ranges. At first floodwaters flowed across the emerging mountain ranges, but as the mountain ranges emerged floodwaters were channeled into deeper south oriented flood flow channels on either side of the emerging mountain masses. The present day north oriented North Platte River drainage route west of the Medicine Bow Mountains (and west of the northwest end of the Laramie Mountains) originated as south oriented flood flow channels while a much deeper southeast oriented flood flow channel eroded headward along the east and northeast side of the emerging Laramie Mountains.

In time headward erosion of the much deeper southeast oriented flood flow channel valley around the northwest end of the Laramie Mountains beheaded south oriented flood flow channels west of the Laramie Mountains and floodwaters on the north ends of the beheaded flood flow channels reversed flow direction to flow in a north direction to the much deeper east and southeast oriented valley and to create (in multiple steps) the north, east, and southeast oriented North Platte River drainage route. The reversal of flood flow on the North Platte River drainage alignment caused a reversal of flood flow on what had been east and southeast oriented flood flow channels diverging from the south oriented flood flow channels on the North Platte River alignment and moving floodwaters into the Laramie Basin. Reversals of flood flow on these east and southeast oriented flood flow channels created the northwest oriented Medicine Bow River drainage route. The north and northeast oriented Medicine Bow River and Rock Creek drainage routes had been established as the east and southeast oriented flood flow channels had eroded deep valleys north of the Medicine Bow Mountains and had beheaded and reversed what had been south oriented flood flow channels crossing the Medicine Bow Mountains (see Medicine Bow River-North Platte River drainage divide area landform origins in the Medicine Bow Mountains essay).

At least some of the east and southeast oriented flood flow diverging from south oriented flood flow channels on the North Platte River alignment flowed to across the emerging Laramie Mountains to the actively eroding and much deeper southeast oriented North Platte River valley. Before the North Platte River flood flow reversal west of the Laramie Mountains an anastomosing complex of diverging and converging crossed the emerging Laramie Mountains. As the Laramie Mountains emerged these anastomosing flood flow channels eroded deeper and deeper valleys into the emerging mountain mass. Reversal of flood flow on the North Platte River alignment (west of the Laramie Mountains) ended flood flow to the Laramie Basin and to the flood flow channels crossing the Laramie Mountains and caused reversals of flood flow that created the northwest and west oriented Medicine Bow River and Rock Creek drainage routes. The North Platte River flood flow reversal almost captured the north oriented Laramie River drainage route, however the Laramie River water gap across the Laramie Mountains had been eroded deep enough to prevent a capture of the north oriented Laramie River drainage route.

Detailed location map for Medicine Bow River-Laramie River drainage divide area

Figure 2: Detailed location map Medicine Bow 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 Medicine Bow River-Laramie River drainage divide area between the Wyoming Medicine Bow and Laramie Mountains. Green colored areas are National Forest lands, which are generally located in mountain areas. The green colored area near the southwest corner of figure 2 is in the Medicine Bow Mountains while the green colored area near the northeast corner of figure 1 is located in the Laramie Mountains. The Medicine Bow River flows in a north direction from the south edge of figure 2 (near southwest corner) to the town of Elk Mountain and then in a northeast and northwest direction to the town of Medicine Bow. From Medicine Bow the Medicine Bow continues in a northwest direction to the west edge of figure 2 (near northwest corner) and west of figure 2 joins the north oriented North Platte River. Rock Creek flows from the south edge of figure 2 (west half, but east of the Medicine Bow River) in a north and northeast direction to the towns of McFadden and Rock River before turning to flow in a northwest direction to join the northwest oriented Medicine Bow River near the town of Medicine Bow. Meiser Creek is a labeled north-northeast and northwest oriented Rock Creek tributary originating east of the town of Rock River. Sevenmile Creek is a labeled southwest oriented stream flowing to the northwest oriented Rock Creek segment. The Laramie River flows in a north direction from the south center edge of figure 2 to the town of Bosler and then along the west side of Wheatland Reservoir No. 2 before turning to flow in an east and northeast direction into the Laramie Mountains and to the east edge of figure 2 (near northeast corner). East and north of figure 2 the Laramie River flows to the southeast oriented North Platte River.  East of Wheatland Reservoir No. 2 are north and northeast oriented headwaters of Bluegrass Creek, which turs to flow in an east direction into the Laramie Mountains and to the east edge of figure 2 (north half-south of Squaw Mountain). East of figure 2 Bluegrass Creek joins northeast and north oriented Sybille Creek, which east of the Laramie Mountains joins the northeast oriented Laramie River. Unlike the Laramie River Bluegrass Creek has no extensive drainage basin west of the Laramie Mountains, yet today Bluegrass Creek flows in a deep water gap across the Laramie Mountains. Another stream of significance in this essay is Dutton Creek, which originates near the south edge of figure 2 (just east of where Rock Creek crosses the south edge) and which flows in a northeast direction to Cooper Lake (north of the south center edge of figure 2). Cooper Lake is an intermittent lake with no apparent outlet, although it is located in a basin adjacent to the Laramie River valley. For purposes of this essay Dutton Creek is treated as a Laramie River tributary, although today Dutton Creek ends at Cooper Lake and does not make it to the Laramie River.

Rock Creek-Dutton Creek drainage divide area

Figure 3: Rock Creek-Dutton Creek 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-Dutton Creek drainage divide area at the northeast end of the Medicine Bow Mountains. The map contour interval for figure 3 is 20 meters. Rock Creek flows in a northwest direction from the south edge of figure 3 across the southwest corner of figure 3 and then turns to flow in a north-northeast and northeast direction to the north center edge of figure 3. North of figure 3 Rock Creek turns to flow in a northwest direction to join the northwest oriented Medicine Bow River, which then flows to the north oriented North Platte River. South of figure 3 Rock Creek originates in the high Medicine Bow Mountains as a north oriented stream and is linked by a deep through valley with headwaters of the south-southeast oriented North Fork Little Laramie  River, which flows to north and northeast oriented Little Laramie River as a barbed tributary. Threemile Creek is a north-northeast oriented Rock Creek tributary originating near the south edge of figure 3 (just north of where northwest oriented Rock Creek crosses the south edge). Deer Mountain is a labeled high point located near the south edge of figure 3 (west of center and east of the Threemile Creek headwaters). The East Fork Dutton Creek flows in a north-northeast direction on the east side of Deer Mountain while the West Fork Dutton Creek flows on the west side of Deer Mountain and then turns in an east direction north of Deer Mountain to join the East Fork and to form northeast and east oriented Dutton Creek, which flows to the east edge of figure 3 (north half). East of figure 3 Dutton Creek flows to Cooper Lake, which is adjacent to the Laramie River. Jimmie Creek is a northeast oriented Dutton Creek tributary located between Dutton Creek and Threemile Creek and north of Deer Mountain. Today water in Rock and Threemile Creeks flows around the northwest end of the Laramie Mountains to reach the southeast oriented North Platte River east of the Laramie Mountains while water in Dutton Creek (assuming it reaches the Laramie River) flows across the Laramie Mountains in a deep valley to join the southeast oriented North Platte River valley east of the Laramie Mountains. Through valleys link the Threemile Creek headwaters valley and the Dutton Creek valley. Ridges are hogback ridges along the Medicine Bow Mountains margin, but the valleys between them are water-eroded valleys and provide evidence that at one time water flowed freely between the Threemile Creek valley and the Dutton Creek valley. What happened here is deep northeast oriented valleys beheaded and reversed south oriented flood flow channels crossing the emerging Medicine Bow Mountains to create the north and northeast oriented Rock Creek drainage route. The northeast oriented valleys initially all converged with southeast and east oriented flood flow channels diverging from the south oriented flood flow channel west of the Laramie Mountains and that were flowing across the emerging Laramie Mountains to reach the much deeper southeast oriented North Platte River valley east of the Laramie Mountains. Later the reversal of flood flow on the North Platte River alignment west of the Laramie Mountains caused a reversal of the flood flow moving towards the Laramie Mountains (north and east of figure 3) to create the northwest oriented Medicine Bow River and Rock Creek segments (north of figure 3), which captured the northeast oriented Rock Creek drainage route, but which did not capture the northeast oriented Dutton Creek drainage route.

Detailed map of Threemile Creek-Dutton Creek drainage divide area

Figure 4: Detailed map of Threemile Creek-Dutton 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 Threemile Creek-Dutton Creek drainage divide area seen in less detail in figure 3. The map contour interval for figure 4 is 20 feet. Threemile Creek flows in a northeast, north-northeast, and north direction from the west edge of figure 4 (near southwest corner) to the north edge of figure 4 (west half). North of figure 3 Threemile Creek joins northeast and northwest oriented Rock Creek, which flows to the northwest oriented Medicine Bow River, which in turn flows to the north oriented North Platte River. The West Fork Dutton Creek flows in a north direction from the south edge of figure 4 (west half-in section 16) and then turns to flow in an east direction across the south margin of section 10 before joining the East Fork in section 11 to form northeast oriented Dutton Creek, which flows to the east edge of figure 4 (near northeast corner). East and north of figure 4 Dutton Creek flows to Cooper Lake, which is adjacent to the north oriented Laramie River valley. Downstream from the Cooper Lake area the Laramie River flows in a north direction and then turns to flow in an east and northeast direction to flow across the Laramie Mountains (in a deep valley) to reach the southeast oriented North Platte River. The Threemile Creek and Dutton Creek valleys are linked by two well-defined through valleys seen in figure 4. The first through valley is located in section 9 (near southwest corner of figure 4) and has a floor elevation of between 8360 and 8380 feet. The ridge to the east rises to 8654 feet and the ridge to the west rises even higher suggesting the through valley is at least 275 feet deep. The through valley probably was eroded by south oriented flood flow moving from the present north oriented Threemile Creek alignment to the northeast oriented Dutton Creek valley and was probably eroded at the time headward erosion of deep northeast oriented valleys was beginning to behead and reverse south oriented flood flow channels crossing the emerging Medicine Bow Mountains. The second through valley is in the north half of figure 4 and is today drained by northeast and east-northeast oriented Seepage Creek with east oriented Canon Ditch located further to the north. This second through valley was probably eroded after the first through valley and probably captured south oriented flood flow moving on the Threemile Creek valley alignment and diverted the floodwaters in an east direction to the Dutton Creek valley. Headward erosion of additional northeast oriented valleys north of figure 4 further beheaded and reversed flood flow on the Threemile Creek alignment to create the north oriented Threemile Creek drainage route seen in figure 4.

Rock Creek-Laramie River drainage divide area

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

Figure 5 illustrates the Rock Creek-Laramie River drainage divide area north and east of figure 3 and there is an overlap area with figure 3. The map contour interval for figure 5 is 20 meters. The Laramie River flows in a northwest, north, and north-northeast direction from the east edge of figure 5 (south half) to the east edge of figure 5 (north half). East and north of figure 5 the Laramie River flows in a north and east direction to a deep east and northeast water gap across the Laramie Mountains and then to the southeast oriented North Platte River. Dutton Creek flows in a northeast and east-southeast direction from the southwest corner of figure 5 to Cooper Lake, which has no outlet, but which is located near the Laramie River. Rock Creek flows in a northeast direction across the northwest corner of figure 5 and north of figure 5 turns to flow in a northwest direction to join the northwest oriented Medicine Bow River, which then flows to the north oriented North Platte River, which flows around the northwest end of the Laramie Mountains before turning to flow in a southeast direction on the east side of the Laramie Mountains and to be joined by the Laramie River. Meiser Creek flows in a north-northeast direction from near the highway to the north edge of figure 5 (east of center) and north of figure 5 turns to flow in a northwest direction to join northeast oriented Rock Creek. Figure 5 illustrates how Rock Creek and Laramie River are located near each other, are separated by a relatively low relief drainage divide, and are flowing in approximately the same directions while further to the north they diverge and flow in very different directions. This situation developed because Rock Creek at one time flowed in a northeast direction to join southeast oriented flood flow that had diverged from a south oriented flood flow channel on the North Platte River alignment west of the Laramie Mountains (and west of figure 5) to flow in an east and northeast direction across the emerging the Laramie Mountains to reach the much deeper southeast oriented North Platte River valley on the east side of the emerging Laramie Mountains. Headward erosion of that much deeper southeast oriented North Platte River valley around the northwest end of the emerging Laramie Mountains beheaded and reversed the south oriented flood flow channels on the present day North Platte River alignment, which in turn reversed the southeast oriented flood flow routes to the maze of east and northeast oriented valleys being eroded across the emerging Laramie Mountains. That reversal of the southeast oriented flood flow created the northwest oriented Medicine Bow River and Rock Creek drainage routes north of figure 5, which captured the northeast oriented Rock Creek drainage route seen in figure 5, but which did not capture the north oriented Laramie River drainage route.

Detailed map of Meiser Creek-Laramie River drainage divide area

Figure 6: Detailed map of Meiser Creek-Laramie River 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 Meiser Creek-Laramie River drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 20 feet. The Laramie River flows in a north direction across the southeast corner of figure 6. East and north of figure 6 the Laramie River flows in a north, east, and northeast direction to and across the Laramie Mountains to join the southeast oriented North Platte River east of the Laramie Mountains. Note southeast oriented streams joining the Laramie River as barbed tributaries in and near section 18. Meiser Creek flows in a north-northeast direction across the northwest corner of figure 6. North of figure 6 Meiser Creek turns to flow in a northwest direction to join northeast and northwest oriented Rock Creek, which flows to the northwest oriented Medicine Bow River, which in turn flows to the north oriented North Platte River west of the Laramie Mountains and west of figure 6. The north oriented North Platte River west of the Laramie Mountains flows in a north and northeast direction to the northwest end of the Laramie Mountains and then turns to flow in an east and southeast direction on the east side of the Laramie Mountains. Figure 6 illustrates that the drainage divide between west oriented Meiser Creek and the northeast oriented Laramie River is only about 100 feet high. Closed depressions seen in figure 6, such as the depression at the corner of sections 10, 11, 14, and 15, may or may not be flood-eroded features. The region seen in figure 6 was a region where floodwater erosion was intense as two opposing drainage routes competed with each to drain floodwaters from the region. An alternative explanation for the closed depressions is they were formed by wind erosion after flood flow across the region had ended. The southeast oriented Laramie River tributaries suggest southeast oriented flood flow was moving to the Laramie River valley prior to the reversal of flood flow that created the north-northeast and northwest oriented Meiser Creek drainage route.

Rock Creek-Wheatland Reservoir drainage divide area

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

Figure 7 illustrates the Rock Creek-Wheatland Reservoir drainage divide area north and east of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 7 is 20 meters. Wheatland Reservoir No. 3 straddles the north edge of figure 7 (east half) and Wheatland Reservoir No. 2 straddles the east edge of figure 7 (north half). The Laramie River flows in a north direction from the south edge of figure 7 (east half) to the south end of Wheatland Reservoir No. 2 and near the west margin of section 31 flows in a north direction from Wheatland Reservoir No. 2 to the north edge of figure 7 (near northeast corner). North and east of figure 7 the Laramie River turns to flow in an east and northeast direction across the Laramie Mountains (in a valley) and joins the southeast oriented North Platte River on the east side of the Laramie Mountains. Rock Creek flows in a northeast and northwest direction from the west edge of figure 7 (north of center) to the west edge of figure 7 (near northwest corner). West and north of figure 7 Rock Creek flows to the northwest oriented Medicine Bow River, which then flows to the north oriented North Platte River, which then flows in a north and northeast direction around the northwest end of the Laramie Mountains before turning to flow in a southeast direction on the east side of the Laramie Mountains. Meiser Creek flows in a north-northeast and northwest direction from the south edge of figure 7 (west half) to join northeast oriented Rock Creek in section 1 (near west edge of figure 7). Spring Creek originates north of the center of figure 7 and flows in a west and northwest direction to join Rock Creek near the elbow of capture where Rock Creek turns to flow in a northwest direction. Figure 7 illustrates how close the northeast and northwest Rock Creek drainage route comes to the Laramie River before the Laramie River crosses the Laramie Mountains. However, the Laramie River is not the only drainage route flowing in a deep valley across the Laramie Mountains. Study of the Laramie Mountains in the Laramie River region reveals a complex of diverging and converging east and northeast valleys, which have eroded deep valleys into the Laramie Mountains. These valleys are much better illustrated and discussed in essays dealing with the Laramie Mountains drainage divide areas and are only briefly illustrated and discussed in this essay. However, it is important to remember an east and northeast anastomosing complex of flood flow channels crossed the Laramie Mountains in the region just to the north and east of figure 7.

Sevenmile Creek-Laramie River drainage divide area

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

Figure 8 provides a topographic map of the Sevenmile Creek-Laramie River drainage divide north of figure 7 and there is an overlap area with figure 7. The map contour interval for figure 8 is 20 meters. The Laramie River flows in a north and east direction across the southeast corner of figure 8. East of the figure 8 the Laramie River enters begins to flow in an east and northeast direction across the Laramie Mountains (in a deep valley) and east of the Laramie Mountains flows in a northeast direction to join the southeast oriented North Platte River. Rock Creek flows in a northwest direction across the southwest corner of figure 8. West of figure 8 Rock Creek joins the northwest oriented Medicine Bow River, which then flows to the north oriented North Platte River. The north oriented North Platte River then flows in a north and northeast direction around the northwest end of the Laramie Mountains before turning in a southeast direction to flow east of the Laramie Mountains. Sevenmile Creek originates in the northeast quadrant of figure 8 and flows in a southwest direction to join northwest oriented Rock Creek near the west edge of figure 8. A through valley in the northeast corner of figure 8 links the southwest oriented Sevenmile Creek valley with the headwaters of east oriented Duck Creek, which flows in a deep valley across the Laramie Mountains to join the northeast oriented Laramie River on the east side of the Laramie Mountains. The east oriented Duck Creek valley was eroded by a northeast and east oriented flood flow channel that diverged from a southeast oriented flood flow channel on the Rock Creek alignment. The southeast oriented flood flow channel on the Rock Creek alignment probably also supplied floodwaters to help erode the Laramie River valley (seen in figures 9 and 10), but the Sevenmile Creek-Duck Creek flood flow channel may have diverted much of the flood flow along the Duck Creek route. In any case the reversal of flood flow on the North Platte River alignment west of the Laramie Mountains caused the reversal of southeast oriented flood flow on the present day northwest oriented Medicine Bow River and Rock Creek alignments, which caused a reversal of flood flow on the Sevenmile Creek alignment to create the drainage routes seen today. Diverging and converging valleys crossing the Laramie Mountains were eroded deeper and deeper as the Laramie Mountains emerged. Emergence of the Laramie Mountains occurred as floodwaters deeply eroded the Laramie Basin to the west and south and the Great Plains region to east and as ice sheet related crustal warping raised the mountain mass.

Laramie River-Bluegrass Creek drainage divide area

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

Figure 9 illustrates the Laramie River-Bluegrass Creek drainage divide area north 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 Laramie Mountains are located in the east half of figure 9. The Laramie Mountains are lower in elevation (generally less than 2200 meters) in this region than the Laramie Mountains are to the north and to the south suggesting much greater erosion of the Laramie Mountains in the vicinity of the deep Laramie River valley. The Laramie River flows in a northeast and east direction (with some jogs in other directions) from the west edge of figure 9 (south of center) to the east edge of figure 9 (near northeast corner). As the Laramie River enters the Laramie Mountains it is flowing in a valley ranging from 100 to 200 meters in depth. East of figure 9 the depth of the Laramie River valley increases. West Bluegrass Creek flows in a north, northeast direction from the south edge of figure 9 (west of center) to join north-northeast oriented East Bluegrass Creek (west of Guide Rock) and to form northeast and east oriented Bluegrass Creek, which flows to the east edge of figure 9 (north of center) and east of figure 9 turns in a southeast and east direction to join north-northeast and north oriented Sybille Creek, which then flows to the northeast oriented Laramie River. East Bluegrass Creek flows from the south center edge of figure 9 to form Bluegrass Creek. West Bluegrass Creek and East Bluegrass Creek, unlike the Laramie River, originate south of figure 9 near the Laramie Mountains west flank, yet Bluegrass Creek flows in a deep east oriented valley comparable to the Laramie River valley. Halleck Creek originates near the south edge of figure 9 (east of center) and flows in a northeast and east direction in Halleck Canyon to the east edge of figure 9 (south of center). East of figure 9 Halleck Creek flows in a northeast direction to join southeast and east oriented Bluegrass Creek, which flows to north-northeast and north oriented Sybille Creek. Sybille Creek originates on the west side of the Laramie Mountains and south of figure 9 flows in a northeast direction as it crosses the Laramie Mountains in a deep northeast oriented valley. As seen in figure 8 Duck Creek has eroded a deep water gap across the Laramie Mountains to the north of figure 9. These and other east oriented valleys crossing the Laramie Mountains in this region originated as an east and/or northeast oriented anastomosing channel complex eroded by east and/or northeast oriented diverging and converging flood flow channels into the emerging Laramie Mountains. The floodwaters diverged from south oriented flood flow channels on the present day north oriented North Platte River alignment to the west of the Laramie Mountains. The amount of erosion documented by the multiple valleys crossing the Laramie Mountains in this region suggests immense volumes of east oriented floodwaters once crossed the emerging Laramie Mountains.

Detailed map of the Laramie River-Bluegrass Creek drainage divide area

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

Figure 10 provides a detailed topographic map of the Laramie River-Bluegrass Creek drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 20 feet. The Laramie River flows in an east direction (with numerous twists and bends) from the west edge of figure 10 (north half) to the east edge of figure 10 (north half). East of figure 10 the Laramie River turns to flow in a northeast, north, and east direction as it flows to the east side of the Laramie Mountains. Bluegrass Creek flows in a north and northeast direction from the south edge of figure 10 (west half) to the mouth of south oriented Tunnel Creek and then turns to flow in a southeast and east-northeast direction to the east edge of figure 10 (south half). East of figure 10 Bluegrass Creek turns to flow in a southeast and east direction to join north-northeast oriented Sybille Creek near the east margin of the Laramie Mountains. The Adam Boyd Ranch is located near where Bluegrass Creek crosses the east edge of figure 10 and an east-southeast oriented tributary joins Bluegrass Creek near the Adam Boyd Ranch. A through valley in section 36 links the headwaters of that east-southeast oriented Bluegrass Creek tributary valley with the Laramie River valley. The Laramie Dell Road in sections 31, 32, and 33 follows the valley of an east oriented stream, which east of figure 10 turns to flow in a north direction to join the Laramie River.  The Laramie Dell Road in the northwest corner of section 31 is located in a through valley linking that east oriented Laramie River tributary valley with the Laramie River valley to the west. These two through valley examples begin to outline what were diverging and converging flood flow channels in an east oriented anastomosing channel complex that deeply eroded this region of the Laramie Mountains. The landscape seen in figure 10 illustrates the effects of intense erosion as immense volumes of east oriented floodwaters flowed across the region. This region is a classic flood-eroded scabland regions in what many observers would consider to be a most unlikely location. Immense volumes of floodwater flowed across this region from the Laramie Basin to reach the much deeper southeast oriented North Platte River valley, which was eroding headward in the region east of the emerging Laramie Mountains.

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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