Laramie River-Horse Creek drainage divide area landform origins in the Wyoming Laramie Mountains, USA

Authors

 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the Laramie River–Horse Creek drainage divide area in the Wyoming Laramie Mountains. The Laramie River flows in a north direction on the west side of the Laramie Mountains and then turns to flow in an east and northeast direction across the Laramie Mountains before flowing in an east and northeast direction to the southeast oriented North Platte River. Horse Creek originates in the high Laramie Mountains just east of the city of Laramie and flows in a north-northeast, east-northeast, and north direction to join the southeast oriented North Platte River. Just north of the Horse Creek headwaters and in the high Laramie Mountains are headwaters of east, northeast, and north oriented Chugwater Creek, which joins the Laramie River on the east side of the Laramie Mountains. Just south of the Horse Creek headwaters in the high Laramie Mountains are headwaters of east oriented Lodgepole Creek, which eventually joins the northeast oriented South Platte River. Through valleys or notches in the high west ridge of the Laramie Mountains link the east oriented Chugwater, Horse, and Lodgepole Creek headwaters valleys with poorly developed west oriented valleys draining to the north oriented Laramie River. Through valleys in the high Laramie Mountains and on the east side of the Laramie Mountains also link the Chugwater, Horse, and Lodgepole Creek valleys. The through valleys and drainage divides 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 Wyoming mountain ranges were beginning to emerge. At first floodwaters flowed in south directions along the crest the present day Laramie Mountains and then were captured by headward erosion of east oriented valleys first from the actively eroding South Platte River valley and then from the actively eroding North Platte River valley. At that time the Laramie Mountains did not stand high above the Laramie Basin to the west and floodwaters were able to flow in east directions from the present day Laramie Basin location across the emerging Laramie Mountains. Headward erosion of the Horse Creek valley captured south oriented flood flow moving to the Lodgepole Creek valley and headward erosion of the Chugwater Creek valley beheaded and reversed flood flow channels to the newly eroded Horse Creek valley. Deep erosion of the Laramie Basin and/or uplift of the Laramie Mountains ended east oriented flood flow to the Lodgepole, Horse, and Chugwater Creek headwaters valleys, however a reversal of flood flow in the Laramie Basin created the north oriented Laramie River drainage route, which north of the study region was captured by a deeper east and northeast oriented valley, which had eroded headward 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 Laramie River-Horse Creek 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 Laramie River-Horse Creek drainage divide area landform evidence in the Wyoming Laramie Mountains will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Laramie River-Horse Creek drainage divide area location map

Figure 1: Laramie River-Horse Creek 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 Laramie River-Horse Creek drainage divide area in the Wyoming Laramie Mountains and illustrates a region in southeast Wyoming with a thin slice of western Nebraska along the east edge. The Laramie Mountains extend in a north and northwest direction from near the south center edge of figure 1 to the north edge of figure 1 (west half) and end slightly north of figure 1. The Medicine Bow Mountains are located in the southwest quadrant of figure 1 and extend south of figure 1 into Colorado. The Laramie Basin is located between the Medicine Bow Mountains and the Laramie Mountains. The North Platte River flows in a north-northwest direction along the west side of the Medicine Bow Mountains and then in a northeast, north, and north-northeast direction to the north edge of figure 1. North of figure 1 the North Platte River flows around the northwest end of the Laramie Mountains and then turns to flow in a southeast direction from the north edge of figure 1 (east of center) to the east center edge of figure 1. The Laramie River flows in a north and northeast direction from the south center edge of figure 1 to the city of Laramie. From Laramie the Laramie River flows in a north direction and just north of Wheatland Reservoir turns to flow in an east and northeast direction across the Laramie Mountains and then flows in an east and northeast direction to join the North Platte River near Fort Laramie. Chugwater Creek originates in the Laramie Mountains (north and east of Laramie) and flows in an east, northeast, and north direction to join the Laramie River slightly north and east of Wheatland. Horse Creek originates in the Laramie Mountains (just east of Laramie) and flows in a northeast and east-northeast direction almost to the Nebraska border and then turns to flow in a north and northeast direction to join the southeast oriented North Platte River near the east center edge of figure 1. Lodgepole Creek originates just south of the Horse Creek headwaters in the Laramie Mountains and flows in an east direction to the east edge of figure 1 and east of figure 1 joins the northeast oriented South Platte River. The Laramie River-Horse Creek drainage divide area investigated in this essay is located in and adjacent to the Laramie Mountains and is east of the north oriented Laramie River (near the city of Laramie), south of Chugwater Creek, and north of Lodgepole Creek.

Today the Laramie Mountains are crossed by numerous valleys, at least eight of which serve as drainage routes with water flowing from the west or southwest side of the Laramie Mountains to the east or northeast side of the Laramie Mountains. Other valleys are through valleys and are drained by two or more drainage routes sometimes flowing in opposite directions. Valleys crossing the Laramie Mountains and throughout the region seen in figure 1 were eroded 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 regional mountain ranges, including the Laramie Mountains, were just beginning to emerge. Mountain ranges emerged as floodwaters deeply eroded surrounding regions and as ice sheet related crustal warping raised the mountain masses. Initially floodwaters flowed in anastomosing complexes of diverging and converging flood flow channels in south directions across and along the present day crest of the Laramie Mountains as well as on both sides of the emerging mountain mass. Many segments of the north oriented North Platte River drainage route near the west edge of figure 1 are located along the alignments former south oriented flood flow channels as are many segments of the north oriented Laramie River drainage route in the Laramie Basin. As the Laramie Mountains began to emerge flood flow channels eroded deeper and deeper valleys into and adjacent to the emerging mountain mass. At the same time the deep southeast oriented North Platte River valley began to erode headward into the region east of the Laramie Mountains and mountains in Colorado to the south of figure 1 were being uplifted, which was blocking the south oriented flood flow in the Laramie Basin. Floodwaters flowing in a south and southeast directions in the Laramie Mountains and from west of the emerging Laramie Mountains were the captured by headward erosion of deep east and northeast oriented valleys, which eroded headward from the deep southeast oriented North Platte River valley into and across the emerging Laramie Mountains mass. Headward erosion of these deep east and northeast oriented valleys beheaded south oriented flood flow channels east and west of the emerging Laramie Mountains. Floodwaters on north ends of the beheaded flood flow channels in the Laramie Basin reversed flow direction to create the north oriented Laramie River drainage route. Headward erosion of the deep southeast oriented North Platte River valley around the northwest end of the Laramie Mountains then beheaded and reversed flood flow channels west of the Laramie Mountains and in a series of steps created the present day north oriented North Platte River drainage route west of the Laramie Mountains. Throughout this entire process numerous flood flow captures and reversals were taking place as ice sheet related crustal warping was uplifting mountain masses and was also raising the entire region.

Detailed location map for Laramie River-Horse Creek drainage divide area

Figure 2: Detailed location map Laramie River-Horse Creek 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 Laramie River-Horse Creek drainage divide area in the Wyoming Laramie Mountains. The Laramie Mountains extend in a north to south direction from the north center edge of figure 2 to the south center edge of figure 2. The Laramie River flows in a north direction (with northeast and northwest jogs) from near the southwest corner of figure 2 to near the northwest corner of figure 2. North of figure 2 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. Tributaries to the north oriented Laramie River from the east (or from the Laramie Mountains) are few and short, although northwest oriented Wallrock Creek in the northwest quadrant of figure 2 is named and is referred to in this essay. Streams flowing from the Laramie Mountains are almost all oriented in east directions, which suggests headward erosion of the Laramie River valley beheaded east oriented flood flow channels. Today it is difficult to imagine how east oriented flood flow channels crossed the Laramie Mountains as the Laramie River is flowing in the Laramie Basin and the Laramie Mountains form a major barrier to the east. Apparently uplift of the Laramie Mountains and/or deep erosion of the Laramie Basin beheaded an east oriented complex of diverging and converging flood flow channels, which once crossed what is today the Laramie Mountains. Horse Creek originates near the west edge of the Laramie Mountains (east of the city of Laramie) and flows in a northeast and east direction to the town of Horse Creek and then in an east-northeast direction to the east edge of figure 2 (south of center). East of figure 2 Horse Creek turns to flow in a north and northeast direction to join the southeast oriented North Platte River. Spring Creek is an east oriented Horse Creek tributary originating near the west edge of the Laramie Mountains and joining Horse Creek in the Laramie Mountains. Mill Creek also originates near the west edge of the Laramie Mountains and flows in an east direction across the Laramie Mountains and then turns to flow in a south-southeast direction to join Horse Creek near the town of Horse Creek. North of Mill Creek is South Chugwater Creek, which also originates near the west edge of the Laramie Mountains and which flows in an east-northeast, east, and north-northeast direction to join Middle Chugwater Creek and then to flow as Chugwater Creek in an east direction to near the town of Farthing and then in a northeast direction to the north edge of figure 2 (near northeast corner). North and east of figure 2 Chugwater Creek turns to flow in a north direction to join the Laramie River, which then flows to the southeast oriented North Platte River. South of the Horse Creek headwaters are headwaters of east-northeast and east-southeast oriented Lodgepole Creek, which flows to the east edge of figure 2. East of figure 2 Lodgepole Creek flows in an east and southeast direction to eventually join the northeast oriented South Platte River.

Wallrock Creek-South Chugwater Creek drainage divide area east end

Figure 3: Wallrock Creek-South Chugwater Creek drainage divide area east end. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of Wallrock Creek-South Chugwater Creek drainage divide area. The map contour interval for figure 3 is 20 meters. The 300-400 meter high west-facing escarpment labeled “Mountains” is a high hogback ridge located along the west margin of the Laramie Mountains and also marks the east margin of the Laramie Basin. The Laramie River flows in a north direction in the region west of figure 3. Wallrock Creek originates on the east side of the high western ridge in the Laramie Mountains and flows in a west and northwest direction to the northwest corner of figure 3. North and west of figure 3 Wallrock Creek flows towards the north oriented Laramie River, but ends in Long Lake, which appears to have no surface outlet. Other streams draining the west slope of the Laramie Mountains flow to the west edge of figure 3 and then to the north oriented Laramie River or end as surface drainage routes. East oriented drainage routes originate near the high west ridge of the Laramie Mountains and flow in east directions to the east edge of figure 3. In the southeast quadrant of figure 3 South Chugwater Creek flows in a north direction from the south center edge of figure 3 and then turns to flow in an east-northeast and east direction to the east edge of figure 3. East of figure 3 South Chugwater Creek turns to flow in a northeast direction to join Middle Chugwater Creek on the east side of the Laramie Mountains and to form northeast and north oriented Chugwater Creek, which then joins the east and northeast oriented Laramie River to join the southeast oriented North Platte River. Middle Chugwater Creek originates on the east side of Baldy Mountain and flows in an east-northeast direction to the east edge of figure 3 (north of center). East of figure 3 and on the east side of the Laramie Mountains Middle Chugwater Creek joins South Chugwater Creek to form northeast and north oriented Chugwater Creek. Shanton Creek is a southeast, east, and northeast oriented Middle Chugwater Creek tributary originating on the west side of Baldy Mountain. Strong Creek originates near the Wallrock Creek headwaters and flows in an east, east-northeast, and southeast direction to the east edge of figure 3 (north half) and east of figure 3 joins Middle Chugwater Creek. Today the Laramie River valley elevation west of figure 3 is between 2140 and 2160 meters and the east oriented Chugwater Creek headwaters are generally located at elevations greater than 2450 meters. Yet a close look a the high west ridge of the Laramie Mountains reveals through valleys (or notches) linking west and northwest oriented Laramie River tributary valleys with the east oriented Chugwater Creek headwaters valleys. For example a notch or through valley links the northwest oriented Wallrock Creek valley with the east oriented Middle Chugwater Creek valley. The through valley (or notch) floor elevation is between 2460 and 2480 meters. Elevations on the north side of the Wallrock Creek canyon reach more than 2540 meters and elevations on Baldy Mountain to the south reach more than 260 meters suggesting the notch or through valley is at least 60 meters deep. Near the south edge of figure 3 a notch or through valley links a west oriented Laramie River tributary valley with the east-northeast oriented South Chugwater Creek valley and is at least 80 meters deep. These notches or through valleys were eroded by east oriented flood flow channels at a time when the steep west-facing Laramie Mountains escarpment did not exist. Since that time either the Laramie Mountains have been uplifted and/or the Laramie Basin to the west has been deeply eroded. In either case the east oriented flood flow channels were beheaded and the floodwaters were diverted in a north direction on the Laramie River alignment and then in an east and northeast direction across the Laramie Mountains to reach the much deeper southeast oriented North Platte River valley.

Detailed map of South Chugwater Creek-North Fork Horse Creek drainage divide area

Figure 4: Detailed map of South Chugwater Creek-North Fork Horse 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 South Chugwater Creek-North Fork Horse Creek drainage divide area just south of figure 3 and is seen in less detail in figure 5. The map contour interval for figure 4 is 40 feet except near the west edge where the contour interval is 20 feet. King Mountain is located south of the center of figure 4. A north oriented stream originates on the west side of King Mountain and near the south edge of section 27 joins a north and east-northeast oriented stream to form a northeast oriented stream, which flows to the north edge of figure 4 (east half). North of figure 4 the stream becomes South Chugwater Creek, which flows to east side of the Laramie Mountains to join Middle Chugwater Creek and to form northeast and north oriented Chugwater Creek. The southeast oriented stream originating in section 9 and flowing south of King Mountain to the south center edge of figure 4 is the North Fork Horse Creek, which south and east of figure 4 flows in an east direction to the east side of the Laramie Mountains and then in a southeast direction to join east-northeast and north oriented Horse Creek, which flows to the southeast oriented North Platte River. A north to south oriented through valley on the west side of King Mountain links the north oriented South Chugwater Creek tributary headwaters valley with the southeast oriented North Fork Horse Creek valley. The through valley floor elevation is between 8240 and 8280 feet. King Mountain exceeds 8560 feet in elevation and the high west ridge of the Laramie Mountains in section 9 reaches an elevation of 8600 feet suggesting the through valley is at least 280 feet deep. The through valley is a water eroded valley and was eroded by south oriented flood flow prior to headward erosion of the deeper northeast oriented South Chugwater Creek tributary valley to the north. Headward erosion of the deeper northeast oriented South Chugwater Creek tributary valley beheaded the south oriented flood flow channel and floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented drainage route west of King Mountain. A different through valley is located near the south edge of section 29 (near northwest corner of figure 4) and links a southwest and northwest valley draining to the west edge of figure 4 with the valley of the east-northeast and northeast oriented South Chugwater Creek tributary. The through valley floor elevation is between 8200 and 8240 feet. Elevations north of the through valley in section 29 exceed 8640 feet while the west ridge of the Laramie Mountains in section 9 to the south rises to more than 8600 feet. These elevations suggest this west to east oriented through valley could be as much as 360 feet deep. This through valley was also eroded by water flowing across what is today the Laramie River-Chugwater Creek drainage divide. Probably the through valley was eroded by east oriented flood flow at a time when the Laramie Mountains did not stand high above the Laramie Basin as they do today.

Laramie River-Schoolhouse Creek drainage divide area

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

Figure 5 illustrates the Laramie River-Schoolhouse Creek drainage divide area south 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 north-northwest direction across the southwest corner of figure 5. West and north of figure 5 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 the southeast oriented North Platte River. The high west ridge of the Laramie Mountains extends in a north to south direction across the center of figure 5. King Mountain (seen in detail in figure 4) is located slightly north and east of the center of figure 5. The north oriented stream originating west of King Mountain flows to east-northeast and east oriented South Chugwater Creek, which flows to the east edge of figure 5 (near northeast corner) and east and north of figure 5 and on the east side of the Laramie Mountains joins Middle Chugwater Creek to form northeast and north oriented Chugwater Creek, which flows to the east and northeast oriented Laramie River. Ragged Top Mountain is located near the east edge of figure 5. The east and east-northeast oriented stream flowing to the east edge of figure 5 just north of Ragged Top Mountain is North Fork Horse Creek, which east of figure 5 flows in an east direction to the east side of the Laramie Mountains and then in a southeast direction to join east-northeast and north oriented Horse Creek, which joins the southeast oriented North Platte River. Roger Canyon is located just north of the south center edge of figure 5 and is drained by a west and northwest oriented stream eventually flowing to the Laramie River. Just east of Roger Canyon are headwaters of east oriented Schoolhouse Creek, which flows to the east edge of figure 5 (south half). East of figure 5 Schoolhouse Creek flows in an east-northeast and east direction and joins Horse Creek on the east side of the Laramie Mountains. A west to east oriented through valley links the west oriented Roger Canyon valley with the east oriented Schoolhouse Creek valley. The through valley floor elevation is between 2440 and 2460 meters or approximately 300 meters higher than the Laramie River valley floor to the west. Elevations on Sherman Hill near the south edge of figure 5 reach 2597 meters and elevations greater than 2620 meters are located just south of figure 5. North of Roger Canyon the high west ridge elevation of the Laramie Mountains exceeds 2620 meters suggesting the through valley is at least 160 meters deep. This deep west to east oriented through valley was eroded by water at a time when the Laramie Mountains did not stand high above the Laramie Basin as they do today. Southeast and east oriented flood flow from the present day north oriented Laramie River alignment flowed from the present day Laramie Basin location to the east oriented Schoolhouse Creek valley. Since that time uplift of the Laramie Mountains and/or deep erosion of the Laramie Basin beheaded and reversed the south, southeast, and east oriented flood flow channel to create the west, northwest oriented Roger Canyon drainage route and the north oriented Laramie River drainage route.

Detailed map of Roger Canyon-Schoolhouse Creek drainage divide area

Figure 6: Detailed map of Roger Canyon-Schoolhouse Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 provides a detailed topographic map of the Roger Canyon-Schoolhouse Creek 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. The Roger Canyon drainage route originates in section 3 (south of the center of figure 6) and flows in a west direction through sections 4, 5, and 6 to the west edge of figure 6 (slightly south of center) and west of figure 6 eventually reaches the north oriented Laramie River. The Laramie River elevation west of figure 6 is approximately 7100 feet. Schoolhouse Creek originates in section 2 and flows in a northwest direction into the east half of section 3 before turning to flow in an east-northeast direction to the east edge of figure 6 (slightly north of center). A west to east oriented through valley in section 3 links the east oriented Schoolhouse Creek valley with the west oriented Rogers Canyon valley. The through valley floor elevation at the road intersection is shown as being 8073 feet or almost 1000 feet higher than the Laramie River valley floor elevation to the west. South of the through valley in section 11 elevations reach more than 8600 feet while north of the through valley and just north of figure 6 elevations on the high west ridge of the Laramie Mountains also exceed 8600 feet suggesting the Roger Canyon-Schoolhouse Creek through valley is at least 525 feet deep. This through valley is a water-eroded valley and was eroded by water flowing from one side of the Laramie Mountains to the other side of the Laramie Mountains. Probably the through was eroded by east oriented floodwaters flowing from the present day Laramie Basin location to the east oriented Schoolhouse Creek valley at a time when the Laramie Mountains did not stand high above the Laramie Basin to the west as is the case today. The through valley provides evidence of approximately 1000 feet of uplift and/or of deep erosion in the Laramie Basin since the time when floodwaters crossed the Laramie Mountains in the present day Roger Canyon-Schoolhouse Creek through valley. Dry Gulch is a north-northwest drainage route flowing from the south edge of figure 6 (west half) and joining Roger Canyon in section 5 and is seen in figures 7 and 8 below.

Dry Gulch-Horse Creek drainage divide area

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

Figure 7 illustrates the Dry Gulch-Horse Creek drainage divide area south of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 7 is 20 meters. The Laramie River flows in a northeast direction from the west edge of figure 7 (south of West Laramie) and then flows between West Laramie and Laramie in a north direction to the north edge of figure 7 (near northwest corner). The high west ridge of the Laramie Mountains extends in a north to south direction across the center of figure 7. The city of Laramie is located at the base of the Laramie Mountains and has an elevation of approximately 2200 meters. Pilot Hill, which is located east of Laramie on the high west ridge of the Laramie Mountains, reaches an elevation of 2705 meters and is approximately 500 meters higher than the city of Laramie. Horse Creek originates on the south side of Pilot Hill and flows in an east, north-northeast, and northeast direction to the northeast corner of figure 7. North and east of figure 7 Horse Creek turns to flow in more of an east direction to the east side of the Laramie Mountains and then in an east-northeast and north direction to eventually join the southeast oriented North Platte River. Roger Canyon is located south of the north center edge of figure 7 and drains in a west and northwest direction to the north edge of figure 7 (west half). Schoolhouse Creek originates east of the Roger Canyon headwaters and flows in an east-northeast and east direction to join Horse Creek (near the northeast corner of figure 7). Dry Gulch headwaters are north of Pilot Hill and drain in a north-northwest direction to join drainage from Roger Canyon (on north side of The Spur). East oriented streams flowing to the east edge of figure 7 (south half) are Lodgepole Creek tributaries. East of figure 7 Lodgepole Creek flows in an east direction for a considerable distance before turning in a southeast direction to join the South Platte River, which then joins the North Platte River to form the Platte River. South of Pilot Hill a west to east oriented through valley links the east oriented Horse Creek headwaters valley with a west oriented Laramie River tributary valley. The through valley floor elevation is between 2580 and 2600 meters and elevations both north and south of the through valley rise to more than 2700 meters suggesting the through valley is at least 100 meters deep. Today the through valley floor is approximately 400 meters higher than the Laramie Basin floor elevation to the west, yet the through valley is evidence that at one time water flowed from the Laramie Basin to the Horse Creek valley. A northwest to southeast oriented through valley located east and south of where the east oriented Horse Creek headwaters turn to flow in a north-northeast direction links the west to east oriented through valley with an east oriented Lodgepole Creek headwaters valley. This northwest to southeast oriented through valley is defined by at least four contour lines on the northeast side and by 9 contour lines on the southwest side and is more than 60 meters deep. Drainage history told by these through valleys is floodwaters first flowed in an east direction across the emerging Laramie Mountains to the east oriented Lodgepole Creek valley, which had eroded headward from what was probably an actively eroding South Platte River valley. Next headward erosion of the deeper Horse Creek valley captured the flood flow and diverted the floodwaters in a northeast, east, and north direction to what was probably an actively eroding North Platte River valley. Shortly after the Horse Creek valley capture of the east oriented flood flow, either uplift of the Laramie Mountains and/or deep erosion in the Laramie Basin to the west ended east oriented flood flow to the through valley south of Pilot Hill.

Detailed map of Horse Creek-North Branch Lodgepole Creek drainage divide area

Figure 8: Detailed map of Horse Creek-North Branch Lodgepole Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 provides a detailed topographic map of the Horse Creek-North Branch Lodgepole Creek drainage divide seen in less detail in figure 7. The map contour interval for figure 8 is 40 feet. The high west ridge of the Laramie Mountains extends in a north to south direction across figure 8. Pilot Hill is located in section 34 near the north edge of figure 8 (west of center). Horse Creek flows in a south direction from the southeast quadrant of section 34 and then in an east direction into section 2 where it turns to flow in a north-northwest direction to the north center edge of figure 8. North of figure 8 Horse Creek turns to flow in a north-northeast direction and then in more of an east direction to the east side of the Laramie Mountains before turning in an east-northeast and north direction to eventually join the southeast oriented North Platte River. The North Branch Lodgepole Creek originates in section 11 (near south center edge of figure 8) and flows in an east direction to the east edge of figure 8. East of figure 8 Lodgepole Creek flows in an east direction between the southeast oriented North Platte River and the northeast oriented South Platte River before finally turning to flow in a southeast direction to join the South Platte River. The unnamed east oriented stream in section 1 (near east center edge of figure 8) is the headwaters on North Lodgepole Creek. East of figure 8 Lodgepole Creek tributaries join to form east oriented Lodgepole Creek. A west-northwest oriented stream originating in the northeast corner of section 10 flows to the west center edge of figure 8 and then flows into the Laramie Basin and to the north oriented Laramie River. The region seen in figure 8 is a triple drainage divide with water flowing to three different rivers, although eventually water in all three of the different rivers ends up in the Nebraska Platte River. A through valley in section 3 links the Horse Creek valley with the west oriented Laramie River tributary valley. The through valley floor elevation is between 8480 and 8520 feet. Pilot Hill rises to 8859 feet while an unnamed hill near the southwest corner of section 2 rises to more than 8840 feet. These elevations suggest the section 3 through valley is at least 320 feet deep. A through valley along the north edge of section 1 links the north oriented Horse Creek valley with the east oriented North Lodgepole Creek headwaters valley. This section 1 through valley has a floor elevation of between 8320 and 8360 feet. The unnamed hill in section 36 to the north rises to more than 8600 feet suggesting the through valley is at least 240 feet deep. These through valleys provide evidence that water once flowed across the drainage divides separating the three different river basins in the high Laramie Mountains just east of the city of Laramie, Wyoming. Water first flowed from the present day Laramie Basin location (now almost 1100 feet lower than the through valley floor elevations) eastward to the Lodgepole Creek valley and also flowed in a south direction on the present day north oriented Horse Creek alignment in figure 8 (probably from a south-southeast oriented flood flow channel on the present day north-northwest oriented Dry Gulch alignment-see figure 7). Headward erosion of the deep north-northeast oriented Horse Creek valley beheaded and reversed the south oriented flood flow while uplift of the Laramie Mountains and/or deep erosion in the Laramie Basin beheaded and reversed the east oriented flood flow from the Laramie Basin.

Chugwater Creek-Horse Creek drainage divide area

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

Figure 9 illustrates the Chugwater Creek-Horse Creek drainage divide area east and slightly north of figure 5 and there is an overlap area with figure 5. The map contour interval for figure 9 is 20 meters. Horse Creek Hogback extends in a south-southeast direction from near the center of figure 9 to the south edge of figure 9. Horse Creek flows in an east-northeast and east direction from near the southwest corner of figure 9 to the east edge of figure 9. East of figure 9 Horse Creek flows in an east-northeast and north direction to join the southeast oriented North Platte River. North Fork Horse Creek flows from the west edge of figure 9 in an east direction (north of Ragged Top Mountain) to Horse Creek Hogback and then in a southeast direction to join Horse Creek. South Chugwater Creek flows in an east-southeast, northeast, and north direction from the west edge of figure 9 (near northwest corner) to the north edge of figure 9 and north of figure 9 joins Middle Chugwater Creek to form northeast and north oriented Chugwater Creek, which flows to the east and northeast oriented Laramie River, which then flows to the southeast oriented North Platte River. Ricker Creek flows in a northeast, east and north direction from the west center edge of figure 9 to join South Chugwater Creek just east of the county line. Sand Creek originates near the north end of Horse Creek Hogback and flows in a northeast and north direction to the north center edge of figure 9 and north of figure 9 joins northeast and north oriented Chugwater Creek. The highway and railroad are located in a north to south oriented through valley along the east margin of the Laramie Mountains. This north to south oriented strike valley is a major through valley and in figure 9 links the north oriented Sand and Chugwater Creek drainage routes with east oriented Horse Creek drainage route. The through valley continues in a south direction south of figure 9 and is crossed by the east oriented Lodgepole Creek valley and then further to the south is drained by a south and southeast oriented Crow Creek tributary with Crow Creek being a South Platte River tributary. The Sand Creek-North Fork Horse Creek through valley floor elevation near the railroad siding of Altus has an elevation of between 2040 and 2060 meters. Elevations east of the through valley exceed 2160 meters suggesting the through valley is at least 100 meters deep. The through valley was probably eroded by south oriented flood flow and initially eroded headward from the deep South Platte River valley, which was eroding headward into northeast Colorado (south of figure 9). Headward erosion of the east oriented Lodgepole Creek valley captured the south oriented flood flow and diverted at least some of the floodwaters in an east direction. Next headward erosion of the east-northeast and north oriented Horse Creek valley captured at least some of the south oriented flood flow and diverted the floodwaters to what was then the actively eroding southeast oriented North Platte River valley. Subsequently headward erosion of the North Platte River valley and its east and northeast oriented Laramie River tributary valley enabled the northeast and north oriented Chugwater Creek valley to behead and reverse the south oriented flood flow and to create the north oriented Sand Creek drainage route. The history described here involves drainage divide areas illustrated and described in other essays in this series, but is consistent with the sequence of flood flow captures and reversals expected as valleys eroded headward across the region.

Detailed map of Sand Creek-North Fork Horse Creek drainage divide area

Figure 10: Detailed map of Sand Creek-North Fork Horse 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 Sand Creek-North Fork Horse Creek drainage divide area seen is less detail in figure 9. The map contour interval for figure 10 is 20 feet except near the west edge where the contour interval is 40 feet. Horse Creek Hogback extends in a south-southeast direction from at least the southeast corner of section 32 (near northwest corner of figure 10) to the south edge of figure 10 (west of center). Sand Creek originates near the west edge of section 4 and flows in an east-northeast direction to near the railroad and then flows in a north direction to the north center edge of figure 10. North of figure 10 Sand Creek flows to northeast and north oriented Chugwater Creek, which flows to the east and northeast oriented Laramie River, which then flows to the southeast oriented North Platte River. The North Fork Horse Creek flows in an east-northeast direction from the west edge of figure 10 to Horse Creek Hogback and then after flowing through a deep water gap crossing Horse Creek Hogback North Fork Horse Creek turns to flow in a southeast direction to the south center edge of figure 10. South of figure 10 North Fork Horse Creek joins east-northeast and north oriented Horse Creek, which flows to the southeast oriented North Platte River. Mill Creek is a northeast stream flowing from the south edge of figure 10 (west of Horse Creek Hogback) and after flowing through the deep Baker Canyon across Horse Creek Hogback turning to flow in a southeast direction to join North Fork Horse Creek south of figure 10. Both North Fork Horse Creek and Mill Creek have eroded 500-foot deep or deeper water gaps across Horse Creek Hogback, which means there has been at least 500 feet of erosion and/or of uplift since those drainage routes were established. The railroad crosses the Sand Creek-North Fork Horse Creek drainage divide at Altus in section 3 where the elevation is 6722 feet. Horse Creek Hogback in section 9 to the west rises to 7375 feet and elevations at the corner of sections 7, 12, 13, and 18 (near southeast corner of figure 10) rise to 7141 feet. These elevations suggest the Sand Creek-North Fork Horse Creek through valley is at least 400 feet deep. The through valley was eroded by south oriented flood flow prior to headward erosion of the northeast and north oriented Chugwater Creek valley to the north of figure 10. Headward erosion of the northeast and north oriented Chugwater Creek valley beheaded the south oriented flood flow channel and floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented Sand Creek drainage route.

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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