Abstract:

This essay uses topographic map evidence to interpret landform origins in the Lodgepole Creek-South Platte River drainage divide area near the Wyoming-Nebraska-Colorado corner. The South Platte River flows in a north direction just east of the Colorado Front Range into northern Colorado and then turns in an east-southeast, east, and northeast direction to flow into western Nebraska where it joins the southeast oriented North Platte River to form the Nebraska Platte River. Lodgepole Creek originates near the west edge of the Laramie Mountains in southern Wyoming and flows in an east direction across the Laramie Mountains and into western Nebraska before turning in a southeast direction to join the northeast oriented South Platte River near the northeast corner of Colorado. Crow Creek originates in the Wyoming Laramie Mountains just south of the Lodgepole Creek headwaters and flows in an east direction toward the Wyoming southeast corner before turning to flow in a southeast, south, and south-southwest direction to join the east-southeast oriented South Platte River. Multiple east and east-southeast oriented Lodgepole Creek and Crow Creek tributary drainage routes are interpreted to have originated as flood flow channels in an east and east-southeast oriented anastomosing channel complex, which once flowed across the present day Laramie Mountains and which was captured by headward erosion of the deeper northeast oriented South Platte River valley. Floodwaters were next captured by headward erosion of the deep south oriented Crow Creek valley, probably from a south oriented flood flow channel that was later captured by continued headward erosion of the deep east-southeast, east, and northeast South Platte River valley (floodwaters on the north end of the beheaded flow channel probably reversed flow direction to flow in a north direction to the deeper South Platte River valley and created the north oriented South Platte River and tributary drainage routes). At the same time as the deep south oriented Crow Creek valley was capturing east and east-southeast oriented flood flow channels near the southeast corner of Wyoming headward erosion of deeper valleys along the east oriented Lodgepole Creek, Sand Draw, and Sidney Draw valleys (from the newly eroded and deep South Platte River valley) were capturing southeast oriented flood flow which had been moving to the actively eroding South Platte River valley with the east oriented Lodgepole Creek valley and the south oriented Crow Creek valley competing with each other to capture floodwaters in the region just west of the west-facing Pine Bluffs escarpment. Headward erosion of the deep valleys from the actively eroding southeast oriented North Platte River valley and Laramie Mountains uplift and/or deep erosion in the Laramie Basin ended then flood flow across southeast Wyoming. Present day drainage routes reflect final flood flow movements as floodwaters drained from the region. Floodwaters are interpreted to have been derived from the western margin of a thick North American ice sheet and were flowing from western Canada to and across Wyoming, Nebraska, and Colorado at a time when Wyoming and Colorado mountain ranges were beginning to emerge.

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 Lodgepole Creek-South Platte River drainage divide area landform origins near the Wyoming-Nebraska-Colorado corner. 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 Lodgepole Creek-South Platte River drainage divide area landform evidence near the Wyoming-Nebraska-Colorado corner will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Lodgepole Creek-South Platte River drainage divide area location map

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

Figure 1 provides a location map for the Lodgepole Creek-South Platte River drainage divide area near the Wyoming-Nebraska-Colorado corner and illustrates a region in northeast Colorado in the south half with the southeast corner of Wyoming in the northwest quadrant and western Nebraska in the northeast quadrant. Rocky Mountain National Park is located in the southwest corner of figure 1. The Laramie Mountains extend in a north to south direction from the north edge of figure 1 (near northwest corner) and are located just east of Laramie, Wyoming before continuing into Colorado where the Laramie Mountains merge into the Colorado Front Range, which continues to the southwest corner of figure 1.  The South Platte River flows on the Colorado Piedmont, just east of the Front Range, in a north and northeast direction from the south edge of figure 1 (west half) to Greeley, Colorado and then turns in an east-southeast, east, and northeast direction to flow to the east edge of figure 1 (near Nebraska-Colorado border). Pawnee Creek is a southeast oriented stream originating near Pawnee Buttes (just south of the center of figure 1) and joining the northeast oriented South Platte River near Atwood, Colorado. The North Platte River flows in a southeast direction across the northeast corner of figure 1 and east of figure 1 joins the South Platte River to form the Nebraska Platte River, which then flows to the Missouri River. Lodgepole Creek originates near the west edge of the Laramie Mountains (just east of Laramie, Wyoming) and flows in an east direction to the east center edge of figure 1 and east of figure 1 turns in a southeast direction to join the northeast oriented South Platte River. Lodgepole Creek tributaries from the north are oriented in east-southeast and southeast directions and an east oriented tributary with several northeast oriented tributaries is shown in Nebraska. Figure 1 shows no Lodgepole Creek tributaries from the south in Wyoming. Also originating in the Laramie Mountains (south of the Lodgepole Creek headwaters) is Crow Creek, which flows in an east direction to Cheyenne and then in an east, southeast, south, and south-southwest direction to join the east-southeast oriented South Platte River near Greeley. Also originating near the Lodgepole Creek headwaters in the Laramie Mountains is Horse Creek, which flows in an east-northeast and north direction to the north center edge of figure 1 (near Wyoming-Nebraska border). The Lodgepole Creek-South Platte River drainage divide area near the Wyoming-Nebraska-Colorado corner investigated in this essay addresses drainage divide areas in the vicinity of the Wyoming-Nebraska-Colorado corner.

Drainage routes in Wyoming, Colorado, and Nebraska developed during immense melt water floods from the western margin of a thick North American ice sheet at a time when Wyoming and Colorado mountain ranges were just beginning to emerge. Floodwaters flowed from western Canada to and across Wyoming, Nebraska, and Colorado from western Canada and were captured in a systematic sequence by headward erosion of deep valleys from what at that time was an evolving Mississippi River drainage system. At the same time ice sheet related crustal warping was raising mountain ranges and plateau areas as floodwaters flowed across them. At first flood flow was in south and southeast direction, although headward erosion of deep valleys and crustal warping subsequently caused flood flow diversions and even reversals. Present day drainage routes in most regions reflect flood flow directions at the time final floodwaters drained from those regions, which varied from region to region. The east oriented Crow, Lodgepole, and Horse Creek drainage routes in southeast Wyoming were formed by east oriented floodwaters flowing from west of the emerging Laramie Mountains to much deeper east oriented valleys eroding headward across Nebraska. These east oriented floodwaters were moving in a large east oriented anastomosing channel complex. At the same time deeper south oriented flood flow channels were eroding headward in the present day Colorado Piedmont region (east of the what was then the emerging Front Range). These south oriented flood flow channels were probably eroding headward from the southeast oriented Arkansas River valley (south of figure 1), although previously the south oriented floodwaters had been moving to southeast and south oriented valleys still further to the south. The south oriented flood flow channels were eroding a south oriented anastomosing channel complex that was capturing the east oriented anastomosing channel complex. Headward erosion of the even deeper east-southeast, east, and northeast oriented South Platte River valley from western Nebraska into northeast Colorado then captured the north end of the actively eroding south oriented anastomosing channel complex and beheaded south oriented flood flow channels on the Colorado Piedmont. Floodwaters on north ends of beheaded flood flow channels reversed flow direction to flow in a north direction to the deeper South Platte River valley and to create north oriented South Platte River tributary drainage routes and the present day north oriented South Platte River route east of the Front Range. At about the same time crustal warping that was raising the Laramie Range (faster than floodwaters could erode valleys across it) and/or headward erosion of deep south oriented flood flow channels west of the emerging Laramie Mountains (flow in those valleys was later reversed to create the north oriented Laramie River drainage system) ended flood flow to the east oriented Crow, Lodgepole, and Horse Creek headwaters valleys. The end of east oriented flood flow halted the capture of the east oriented anastomosing channel complex by the deeper south oriented anastomosing channel complex and today some of evidence of the halted capture process is preserved in landforms found near the Wyoming-Nebraska-Colorado corner.

Detailed location map for Lodgepole Creek-South Platte River drainage divide area

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

Figure 2 provides a detailed location map for the Lodgepole Creek-South Platte River drainage divide area near the Wyoming-Nebraska-Colorado corner. The west to east oriented Colorado northern boundary is located just south of the center of figure 2. North of the Colorado state line Kimball County is in Nebraska and Laramie County is in Wyoming. Lodgepole Creek flows in an east-southeast direction from the northwest corner of figure 2 almost to the Nebraska state line where it turns in a northeast direction to Pine Bluffs, Wyoming and then in an east-northeast and east direction to Bushnell, Nebraska and the east edge of figure 2 (north half). Tributaries to Lodgepole Creek from the north are oriented in southeast and east-southeast directions and include Chivington Draw and Spring Creek (north). Muddy Creek is an east, southeast, and north-northeast oriented tributary joining Lodgepole Creek near Pine Bluffs. Spring Creek (south) is an east and north-northeast tributary to Muddy Creek tributary. The northeast and east oriented drainage system originating in the Kimball County southwest corner is Sand Draw, which east of figure 2 drains to Sidney Draw, which then drains to Lodgepole Creek. The northeast and east oriented drainage routes south and east of the Sand Draw headwaters are Sidney Draw headwaters. East of figure 2 Sand Draw and Sidney Draw drain in east oriented valleys parallel to the Lodgepole Creek valley until Sand Draw joins Sidney Draw and then Sidney Draw joins Lodgepole Creek. Southeast oriented streams in the southeast corner of figure 2 flow to the northeast oriented South Platte River (south and east of figure 2). Lone Tree Creek flows in a south-southeast direction across the southwest corner of figure 2. South of figure 2 Lone Tree Creek flows to the east-southeast, east, and northeast oriented South Platte River. The east, southeast, and south oriented stream flowing from Cheyenne, Wyoming to the south edge of figure 2 (slightly west of center) is Crow Creek. South of figure 2 Crow Creek flows in a south-southwest direction to join the east-southeast, east, and northeast oriented South Platte River. Porter Creek originates south of Cheyenne and north of the state line and flows in an east direction to Chalk Bluffs and then turns to flow in a southeast direction to join south-southeast oriented Little Crow Creek, which flows to Heart Reservoir (near south edge of figure 2-west of Crow Creek) and which joins Crow Creek south of figure 2. Other south-southeast and southeast oriented streams in the southwest quadrant of figure 2 are either Crow Creek tributaries or Lone Tree Creek tributaries with water flowing to the east-southeast, east, and northeast oriented South Platte River. The Crow Creek and Porter Creek elbows on capture (or direction changes) illustrate how headward erosion of the deeper south oriented Crow Creek valley captured two separate east oriented flood flow channels in the east oriented anastomosing channel complex. The Spring Creek and Muddy Creek elbows of capture south of Pine Bluffs illustrate how headward erosion of a deeper valley on the Lodgepole Creek alignment beheaded and reversed southeast oriented flood flow moving to the actively eroding northeast oriented South Platte River valley.

Lodgepole Creek-Crow Creek drainage divide area

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

Figure 3 provides a reduced size topographic map of Lodgepole Creek-Crow Creek drainage divide area and is located in Wyoming east of Cheyenne. The map contour interval for figure 3 is 10 meters. Lodgepole Creek (not labeled in figure 3) flows in an east-southeast and southeast direction from near the northwest corner of figure 3 to the east edge of figure 3 (north of center). East of figure 3 Lodgepole Creek makes a northeast jog and then flows in an east direction into western Nebraska and eventually turns in a southeast direction to join the northeast oriented South Platte River. Crow Creek flows in an east, east-southeast, and southeast direction from the west edge of figure 3 (south half) through the towns of Campstool and Arcola to the south center edge of figure 3. South of figure 3 Crow Creek turns to flow in a south and south-southwest direction to eventually join the east-southeast, east, and northeast oriented South Platte River. Multiple east and east-southeast oriented streams between Lodgepole Creek and Crow Creek flow from the west edge of figure 3 to converge in the east half of figure 3 so as to form east oriented Muddy Creek, which flows to the east edge of figure 3 (south half). East of figure 3 Muddy Creek flows in an east-southeast and north-northeast direction to join east oriented Lodgepole Creek. The east and east-southeast oriented streams flowing across the west half of figure 3 are located in valleys that originated as flood flow channels in an east oriented anastomosing channel complex. The diverging and converging flood flow channels crossed what were at that time the emerging Laramie Mountains to the west of figure 3 and floodwaters were flowing to deep east oriented valleys eroding headward into western Nebraska. Topographic map evidence does not usually permit a distinction between erosion surfaces and deposition surfaces and the surface seen in figure 3 could be either, but in either case the surface seen in figure 3 was produced by the east oriented floodwaters. The Crow Creek turn to the south illustrates where headward erosion of a deep south-oriented valley captured east oriented flood flow on the Crow Creek alignment. The capture affected Crow Creek and east oriented flood flow channels south of the east oriented Crow Creek flood flow channel. Flood flow channels further to the north were in the process of being captured when headward erosion of a valley on the Lodgepole Creek alignment captured those flood flow channels to create the present day east-southeast and north-northeast oriented Muddy Creek route.

Crow Creek-Simpson Creek drainage divide area

Figure 4: Crow Creek-Simpson Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 provides a topographic map of the Crow Creek-Simpson Creek drainage divide area south and slightly west of figure 3 and includes an overlap area with figure 3. The map contour interval for figure 4 is 10 meters. Crow Creek flows in an east-southeast, southeast, south, and southeast direction from the north edge of figure 4 (west of center) to the east edge of figure 4 (near southeast corner). East and south of figure 4 Crow Creek turns to flow in a south and south-southwest direction to join the east-southeast, east, and northeast oriented South Platte River. Multiple east oriented streams flow from the west edge of figure 4 to join Crow Creek or turn to flow in southeast and south directions to the south edge of figure 4. The streams flowing to the south edge of figure 4 converge south of figure 4 to form south-southeast and south oriented Little Crow Creek, which then joins south-southwest oriented Crow Creek. Streams seen in figure 4 are flowing across a south and southeast-facing escarpment known as Chalk Bluffs and illustrate how headward erosion of a deep south oriented valley captured east oriented flood flow channels in an east oriented anastomosing channel complex. Elevations on the upland surface north of the Chalk Bluffs escarpment along the west edge of figure 4 rise to more than 1800 meters. Elevations near the southeast corner of figure 4 are less than 1600 meters. These elevations suggest the south oriented valley was approximately 200 meters deeper than the surface on which the east oriented anastomosing channel complex was located. Every east oriented flood flow channel south of east oriented Crow Creek alignment was captured and diverted in a south direction. As seen in figure 3 and in subsequent figures every east oriented flood flow channel north of Crow Creek was captured by the east oriented Lodgepole Creek valley and was not diverted in a south direction. The deep south oriented valley was eroding headward from a south oriented anastomosing channel complex that was eroding headward along the Colorado Piedmont just east of what was at that time the emerging Colorado Front Range. Headward erosion of the deeper east-southeast, east, and northeast oriented South Platte River valley (south of figure 4) captured the north end of the south oriented anastomosing channel complex. Floodwaters on north ends of the beheaded flood flow channels reversed flow direction to flow to the deeper South Platte River valley and to create the north oriented South Platte River drainage route (east of the Front Range) and north oriented South Platte River tributary drainage routes (south of the east-southeast, east, and northeast oriented South Platte River valley).

Crow Creek-Sidney Draw drainage divide area

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

Figure 5 illustrates the Crow Creek-Sidney Draw drainage divide area east and south of figure 4 and there is an overlap area with figure 3. The map contour interval for figure 5 is 10 meters. Crow Creek flows in a southeast, south, and south-southwest direction from Hereford (near northwest corner of figure 5) to the south edge of figure 5 (near southwest corner). South of figure 5 Crow Creek flows in a south-southwest direction to join the east-southeast, east, and northeast oriented South Platte River. A south-facing step in the Chalk Bluffs escarpment extends in an east-southeast direction across the south half of the northwest quadrant of figure 5 to join a west-facing escarpment, which extends almost to the south edge of figure 5 and which also extends in a north direction to the north edge of figure 5 (east of center). The south end of this west-facing escarpment is also known as Chalk Bluffs, while north of figure 5 (and seen in figure 6) the west-facing escarpment is known as Pine Bluffs. The west-facing escarpment is the east wall of the deep south-oriented Crow Creek valley that eroded headward across the east oriented anastomosing channel complex. The southeast-facing basin on the east side of the southern end of the upland in the southeast quadrant of figure 5 is drained by southeast oriented North Pawnee Creek with water flowing to the northeast oriented South Platte River. Pawnee Buttes are a labeled high point in the southeast-facing basin located near the southeast corner of figure 5. Sidney Draw is a northeast and east oriented drainage route originating on the upland region in the southeast quadrant of figure 5 and draining to the east edge of figure 5 (north half). East of figure 5 Sidney Draw drains in roughly an east direction along the rim the deep northeast oriented South Platte River valley before draining in an east direction to eventually join east and southeast oriented Lodgepole Creek. East and northeast oriented Sidney Draw headwaters drainage routes probably captured east-southeast oriented flood flow channels flowing to the actively eroding and much deeper southeast oriented North Pawnee Creek valley, which was eroding headward from the deep and actively eroding northeast oriented South Platte River valley. Headward erosion of the deep south-oriented Crow Creek valley next beheaded the east-southeast oriented flood flow channels to the northeast and east oriented Sidney Draw tributary drainage routes. This interpretation suggests the east oriented Lodgepole Creek valley (and its tributary Sidney Draw valley) and the deeper, but more distant northeast oriented South Platte River valley were competing with each other to capture the east oriented flood flow in the east half of figure 5. Headward erosion of the deep south oriented Crow Creek  valley complicated the competition by capturing all east oriented flood flow routes south of the east oriented flood flow channel on the present day east oriented Crow Creek alignment. .

Muddy Creek-Spring Creek (south) drainage divide area

Figure 6: Muddy Creek-Spring Creek (south) drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 provides a topographic map of the Muddy Creek-Spring Creek (south) drainage divide area north and slightly west of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 6 is 10 meters. Crow Creek flows in a southeast direction across the southwest corner of figure 6 (Hereford is the town near Crow Creek). Muddy Creek flows in an east-southeast and north-northeast direction from the northwest corner of figure 6 to the north edge of figure 6 (east half). North of figure 6 Muddy Creek joins Lodgepole Creek, which makes a jog to the northeast and then flows in an east direction before turning in a southeast direction to join the northeast oriented South Platte River. The west-facing escarpment just east of the north-northeast oriented Muddy Creek segment is Pine Bluffs and extends to south edge of figure 6. South of figure 6 (as seen in figure 5) the west-facing Pine Bluffs escarpment merges with the west-facing Chalk Bluffs escarpment. Spring Creek (south) is an east and north oriented tributary originating near the center of figure 6 and joining Muddy Creek at the Muddy Creek elbow of capture (where Muddy Creek turns to flow in a north-northeast direction). A north oriented tributary joins Spring Creek at the point where Spring Creek turns to flow in a north direction. Northeast and east oriented streams on the upland east of the west-facing Pine Bluffs escarpment are headwaters of east oriented Sand Draw, which east of figure 6 drains in an east direction between east oriented Lodgepole Creek and east oriented Sidney Draw before joining Sidney Draw to then drain to Lodgepole Creek. The west-facing Pine Bluffs escarpment is the east wall of the south oriented valley that eroded headward to capture the east oriented anastomosing channel complex. Headward erosion of the south oriented valley successfully beheaded most east oriented flood flow channels to what are today east and northeast oriented Sand Draw and Sidney Draw headwaters drainage routes. However, there was competition between the newly eroded south oriented valley and the east oriented Lodgepole Creek valley for floodwaters entering the north end of the newly eroded south oriented valley. Some of the captured floodwaters moved in a south direction while some of the floodwaters moved in a north-northeast direction to the east oriented Lodgepole Creek valley. Floodwaters flowing into the newly eroded and deeper south oriented valley eroded the west wall of the valley so today the there is a gradual east-southeast oriented slope as seen in figure 6.

Spring Creek (north)-Muddy Creek drainage divide area

Figure 7: Spring Creek (north)-Muddy Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Spring Creek (north)-Muddy Creek drainage divide area north and slightly east of figure 5 and includes an overlap area with figure 6. The map contour interval for figure 7 is 10 meters. The west-facing Pine Bluffs escarpment is located south of the town of Pine Bluffs in the east half of figure 7. Lodgepole Creek flows from the west edge of figure 7 (north half) in a southeast, east and northeast direction to near the town of Pine Bluffs. Lodgepole Creek then flows in a north and east direction from Pine Bluffs to the east edge of figure 7 (north half). Muddy Creek flows in an east and southeast direction from the west edge of figure 7 (south half) to the south edge of figure 7 (east half) and south of figure 7 turns to flow in a north-northeast direction along the base of the Pine Bluffs escarpment to near the town of Pine Bluffs where it joins northeast and east oriented Lodgepole Creek. Spring Creek (north) flows in a southeast direction from the northwest corner of figure 7 to Wisroth Reservoir and then turns in an east-northeast direction to join Lodgepole Creek at the point where Lodgepole Creek turns to flow in an east direction to the east edge of figure 7. What has happened here is the east oriented flood flow channel east of the town of Pine Bluffs is probably the eastern extension of a flood flow channel on the Spring Creek (north) alignment, although in flood formed anastomosing channel complexes the flood flow channels are often constantly changing. Headward erosion of a deeper valley along the base of the west-facing Pine Bluffs escarpment captured enough of the flood flow moving on the east and east-southeast oriented Lodgepole Creek, Muddy Creek, and Spring Creek (south) alignments. Apparently when flood flow in the east oriented Spring Creek (south), Muddy Creek, and Lodgepole Creek flood flow channels ended the east oriented flood flow channel captured the final flood flow movements and ended any flood flow spilling in a south direction to the south oriented Crow Creek drainage route.

Muddy Creek-Sand Draw drainage divide area

Figure 8: Muddy Creek-Sand Draw drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 provides a topographic map of the Muddy Creek-Sand Draw drainage divide area east and slightly south of figure 7 and includes an overlap area with figure 7. The map contour interval for figure 8 is 10 meters. The west-facing Pine Bluffs escarpment is located south of the town of Pine Bluffs in the west half of figure 8. Lodgepole Creek flows in an east, northeast, and north direction from the west edge of figure 8 (north half) to the north edge of figure 8 (north of Pine Bluffs) and then turns to flow in an east direction to the north center edge of figure 8. North and east of figure 8 Lodgepole Creek flows in an east-northeast and east direction and eventually turns in a southeast direction to join the northeast oriented South Platte River. Spring Creek (north) is the east oriented stream flowing from the northwest corner of figure 8 to join Lodgepole Creek north of Pine Bluffs. Muddy Creek flows in an east direction from the west edge of figure 8 (south half) and at the base of the Pine Bluffs escarpment turns in a north-northeast direction to join Lodgepole Creek near the town of Pine Bluffs. Spring Creek (south) is the north oriented Muddy Creek tributary flowing from the southwest corner of figure 8. Northeast oriented drainage routes draining to the east edge of figure 8 are tributaries to east oriented Sand Draw, which east of figure 8 drains in an east direction between east oriented Lodgepole Creek and east oriented Sidney Draw before finally joining Sidney Draw, which then joins Lodgepole Creek. These northeast oriented Sand Draw headwaters valleys probably eroded headward across east and southeast oriented flood flow prior to the erosion of the deep valley west of the Pine Bluffs escarpment. One northeast oriented stream originates near the escarpment crest a short distance east of the Muddy Creek elbow of capture (where Muddy Creek turns to flow in a north-northeast direction). This unnamed stream flows in a northeast direction to the north edge of figure 8 (east of center) and north of figure 8 joins Lodgepole Creek. A shallow through valley links the north-northeast headwaters valley of this stream with the north oriented Spring Creek (south) valley. The through valley is defined by two contour on the northwest side suggesting the through valley is at least 10 meters deep. The through valley provides evidence of a former flood flow channel. Water in this through valley could have been flowing in a south-southwest direction or in a north-northeast direction. While I am uncertain as to the direction of flow in that through valley the direction of flow is more obvious in through valleys crossing the escarpment crest south of figure 8 and also near the town of Pine Bluffs. East of the Lodgepole Creek elbow of capture (where east oriented Lodgepole Creek turns in a northeast direction) there is a shallow through valley crossing the crest of the Pine Bluffs escarpment and leading to a northeast and north oriented Lodgepole Creek tributary valley. Figure 9 provides a detailed topographic map of that shallow through valley to demonstrate evidence floodwaters once flowed in an east and northeast direction across what is now the west-facing Pine Bluffs escarpment (which means the escarpment did not exist at that time).

Detailed map of Lodgepole Creek-Muddy Creek drainage divide area

Figure 9: Detailed map of Lodgepole Creek-Muddy Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 is a detailed topographic map of the Lodgepole Creek-Muddy Creek drainage divide area seen in less detail in figure 8. The map contour interval for figure 9 is 10 feet.  Pine Bluffs is the town straddling the north edge of figure 9. Lodgepole Creek flows in an east, northeast, and north direction from the west edge of figure 9 (south half) to the north edge of figure 9 (just west of Pine Bluffs). North of figure 9 Lodgepole Creek turns to flow in an east, east-northeast, and east direction and eventually turns to flow in a southeast direction to join the northeast oriented South Platte River. The west-facing Pine Bluffs escarpment is located south of the town of Pine Bluffs. Muddy Creek flows in a north-northeast and north direction from the south edge of figure 9 along the base of the Pine Bluffs escarpment to join north oriented Lodgepole Creek near the southeast corner of section 16. An unnamed northeast oriented stream originates south of the town of Pine Bluffs near the west edge of section 26 and flows to the north edge of figure 9 (near northeast corner). North of figure 9 the unnamed stream joins east oriented Lodgepole Creek. An east-northeast oriented through valley eroded into the crest of the Pine Bluffs escarpment in sections 27 and 26 links the unnamed northeast oriented stream valley with an east oriented Muddy Creek tributary valley. The through valley floor elevation is between 5290 and 5300 feet. Elevations north and south of the through valley rise to at least 5335 feet suggesting the through valley is at least 35 feet deep. The through valley is aligned with the east oriented Lodgepole Creek drainage route at the west edge of figure 9, which suggests the through valley originated as on one of two or more east oriented diverging and converging flood flow channels on the present day east oriented Lodgepole Creek drainage route. Headward erosion of a deeper east oriented valley on the present day Lodgepole Creek route captured the east oriented flood flow channels and beheaded the diverging flood flow channels. Floodwaters on the west end of the beheaded flood flow channel reversed flow direction to create the west oriented Muddy CReek tributary drainage route.

Horse Creek-Lodgepole Creek drainage divide area

Figure 10: Horse Creek-Lodgepole Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 provides a greatly reduced size topographic map of the Horse Creek-Lodgepole Creek drainage divide area north and west of figure 8 and includes an overlap area with figures 8 and 9. The map contour interval for figure 10 is 10 meters. The town of Pine Bluffs is located near the southeast corner of figure 10. The north to south oriented Wyoming-Nebraska state line is located just east of Pine Bluffs. Lodgepole Creek flows in an east-southeast direction from the west edge of figure 10 (south half) to the south edge of figure 10 (east of center) and then turns to flow back into figure 10 in a northeast, north, and east direction around the town of Pine Bluffs to the east edge of figure 10. East of figure 10 Lodgepole Creek flows in an east-northeast and east direction before eventually turning in a southeast direction to join the northeast oriented South Platte River. The north-facing escarpment near the west half of the north edge of figure 10 is the south wall of the deep east-northeast, east, and north oriented Horse Creek valley. Horse Creek originates near the west edge of the Laramie Mountains (just north of the Lodgepole Creek headwaters) and flows in an east-northeast direction across the Laramie Mountains and almost to the Nebraska state line before turning in a north direction to join the southeast oriented North Platte River. Between the Horse Creek valley near the northwest corner of figure 10 and the northeast, north, and east oriented Lodgepole Creek valley near the southeast corner of figure 10 are multiple east and east-southeast oriented streams, all of which flow to Lodgepole Creek either in figure 10 or east of figure 10. Headward erosion of the deep east-northeast oriented Horse Creek valley beheaded several of these east-southeast oriented Lodgepole Creek tributaries. Tributaries not beheaded by headward erosion of the deep Horse Creek valley are west of figure 10 and are oriented in east directions. These closely spaced east and east-southeast oriented drainage routes originated as an east oriented anastomosing channel complex, which was captured by headward erosion of the much deeper northeast oriented South Platte River valley, which diverted floodwaters in a southeast direction toward the actively eroding North Pawnee Creek valley (seen in figure 5). Headward erosion of deep east oriented valleys along the Lodgepole Creek, Sand Draw, and Sidney Draw alignments captured the southeast oriented flood flow and then eroded headward along the west side of the present day Pine Bluffs escarpment to capture east-southeast oriented flood flow moving toward the deep south oriented Crow Creek valley. Subsequently headward erosion of the deep Horse Creek valley from the actively eroding and deep southeast oriented North Platte River valley beheaded some of the east-southeast oriented flood flow channels. Events further to the west in the Laramie Mountains and/or in the Laramie Basin ended flood across the Horse Creek-Lodgepole Creek drainage divide and present day drainage routes reflect how final floodwaters drained from the region.

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.