Chugwater Creek-Goshen Hole drainage divide area landform origins east of the Wyoming Laramie Mountains, USA

Authors

 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the Chugwater Creek-Goshen Hole drainage divide area east of the Wyoming Laramie Mountains. Goshen Hole is a large east-oriented escarpment-surrounded basin in eastern Wyoming and drains to the southeast oriented North Platte River in adjacent western Nebraska. Chugwater Creek originates in the Wyoming Laramie Mountains and flows in an east and northeast direction before turning to flow in a north direction immediately to the west of the deeper east-oriented Goshen Hole escarpment-surrounded basin. Chugugwater Creek then flows to the east and northeast oriented Laramie River, which north of Goshen Hole joins the southeast-oriented North Platte River. Between the north-oriented Chugwater Creek valley and the east-facing Goshen Hole escarpment rim are upland flats, which are interpreted to be underlain by thick erosion resistant materials. The erosional resistant materials either do not extend west of the Chugwater Creek valley or are much thinner west of the Chugwater Creek valley suggesting the north oriented Chugwater Creek valley eroded headward along or near the west edge of the erosion resistant material. The east-oriented Goshen Hole escarpment-surrounded basin is interpreted to be a giant abandoned headcut and to have been eroded by immense east oriented floods flowing across the present day Laramie Mountains to reach what at that time was an actively eroding and much deeper southeast oriented North Platte River valley head near the present day Wyoming-Nebraska border. Floodwaters were derived from the western margin of a thick North American ice sheet and were flowing from western Canada to and across Wyoming at a time when Wyoming mountain ranges were beginning to emerge. Floodwaters flowing in an east direction across the Laramie Mountains had flowed in a south direction on the present day north oriented North Platte River alignment west of the Laramie Mountains and then had turned in southeast and east directions to flow across the emerging Laramie Mountains to reach the much deeper North Platte River valley on the east side of the Laramie Mountains. The erosion resistant materials underlying the flats between the Chugwater Creek valley and the Goshen Hole basin significantly slowed headward erosion of the deep east-oriented Goshen Hole basin valley head and the somewhat shallower north oriented Chugwater Creek valley was able to erode headward across the east oriented flood flow moving to the deeper Goshen Hole valley. Headward erosion of the Chugwater Creek valley diverted floodwaters in a north direction to the newly eroded east and northeast oriented Laramie River valley. Headward erosion of the north oriented Chugwater Creek valley also captured flood flow still moving across the emerging Laramie Mountains and ended all flood flow movements to what is now the Goshen Hole basin. Headward erosion of the deep southeast oriented North Platte River valley around the northwest end of the Laramie Mountains then in several steps beheaded and reversed flood flow channels west of the Laramie Mountains to create the north oriented North Platte River drainage route on the west side of the Laramie Mountains and to end all southeast and east oriented flood flow from the southwest side of the Laramie Mountains to the east side of the Laramie Mountains in what is today an anastomosing complex of east and northeast oriented Laramie River and tributary valleys crossing 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 Chugwater Creek-Goshen Hole drainage divide area landform origins east of 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 Chugwater Creek-Goshen Hole drainage divide area landform evidence east of the Wyoming Laramie Mountains will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Chugwater Creek-Goshen Hole drainage divide area location map

Figure 1: Chugwater Creek-Goshen Hole 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 Chugwater Creek-Goshen Hole drainage divide area east the Wyoming Laramie Mountains and illustrates a region in southeastern Wyoming with a small region in western Nebraska east of Wyoming. The Laramie Mountains extend in a southwest and south direction from near Casper (near north edge of figure 1) to the south center edge of figure 1. The north end of the Medicine Bow Mountains can be seen in the southwest quadrant of figure 1. The Laramie Basin is located between the Medicine Bow Mountains and the Laramie Mountains while the region east of the Laramie Mountains is the Great Plains. The North Platte River flows from the south edge of figure 1 (on west side of Medicine Bow Mountains) to Casper and then after flowing around the northwest end of the Laramie Mountains flows in a southeast direction to the east edge of figure 1 (south if center). The Laramie River flows in a northeast direction from the south edge of figure 1 to the city of Laramie and then in a north direction to just north of Wheatland Reservoir where 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 North Platte River near Fort Laramie. Chugwater Creek originates in the Laramie Mountains (north and east of Laramie) and flows in an east, northeast, north-northwest, and north-northeast direction to join the Laramie River near Wheatland. The unlabeled northeast and north oriented Laramie River tributary located between the Laramie River and Chugwater Creek is Sybille Creek. Sybille Creek also flows across the Laramie Mountains. Goshen Hole is not labeled in figure 1, but is an escarpment-surrounded lowland opening in an east direction located directly east of the north-northwest oriented Chugwater Creek drainage route (between the towns of Chugwater and Wheatland). Topographic maps illustrated in this essay show regions along the Chugwater Creek-Goshen Hole drainage divide, although to understand the Goshen Hole origin it is necessary to understand the origin of drainage routes in and west of the Laramie Mountains.

All drainage routes seen in figure 1 developed during immense melt water floods from the western margin of a thick North American ice sheet. Floodwaters flowed from western Canada to and across Wyoming at a time when Wyoming mountain ranges were just beginning to emerge. At first floodwaters flowed in south directions across and along the present day crest of the Laramie Mountains as well as on both sides of the Laramie Mountains. The Laramie Mountains (and other Wyoming mountain ranges) emerged as floodwaters deeply eroded surrounding regions and as ice sheet related crustal warping raised the mountain masses. The north oriented North Platte River drainage route west of the Laramie Mountains originated as south oriented flood flow channels as did the north oriented Laramie River drainage route between the Medicine Bow and Laramie Mountains. Modern day valleys and landscape features began to develop when the deep southeast oriented North Platte River valley began to erode into the region east of the Laramie Mountains and to capture south oriented floodwaters on the east and northeast side of the emerging Laramie Mountains. At the same time floodwaters were being channeled in east, southeast, and south directions on the southwest side of the emerging Laramie Mountains into the Laramie Basin and then in a south direction into Colorado. However, ice sheet related crustal warping was raising mountains at the south end of Laramie Basin and the east and southeast oriented floodwaters moving into the Laramie Basin began to erode east and northeast oriented valleys across the emerging Laramie Mountains to reach the much deeper North Platte River valley, Today there is a large complex of east and northeast oriented diverging and converging valleys originating on the west side of the Laramie Mountains and extending across the Laramie Mountains towards the Goshen Hole location. These valleys are illustrated and discussed in the Laramie River-Sybille Creek and the North Laramie River-Laramie River essays.

What happened in the Laramie Mountains was headward erosion of an east oriented anastomosing complex of ever-changing flood flow channels captured what had been a south oriented anastomosing complex of constantly evolving flood flow channels (flowing along what is now the crest of the Laramie Mountains). At first these valleys directed the large volumes of floodwaters moving across the emerging Laramie Mountains in an east direction where the floodwaters flowed into Goshen Hole, which was being eroded headward by east oriented floodwaters moving to the deep North Platte River valley. Headward erosion of the deep southeast oriented North Platte River valley and the east and northeast oriented Laramie River valley from it then beheaded south oriented flood flow channels west of the actively eroding Goshen Hole escarpment. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to flow to the much deeper Laramie-North Platte River valley and created the north-northwest oriented Chugwater Creek drainage route. Next headward erosion of the Laramie River valley beheaded south oriented flood flow on the Sybille Creek alignment and floodwaters reversed flow direction to create the north oriented Sybille Creek drainage route. These reversed flood flow routes captured floodwaters moving across the Laramie Mountains in sequence from south to north. Headward erosion of the Laramie River valley beheaded and reversed flood flow channels in the Laramie Basin to create the present day north oriented Laramie River drainage route there, although east and southeast oriented flood flow from west of the Laramie Mountains continued to flow into the Laramie Basin and then east across the Laramie Mountains to the much deeper southeast oriented North Platte River valley. Headward erosion of the deep southeast oriented North Platte River valley around the northwest end of the Laramie Mountains then beheaded and reversed flood flow channels west of the Laramie Mountains. In a series of steps the north oriented North Platte River drainage route was created, which in turn beheaded and reversed southeast and east oriented flood flow routes into the Laramie Basin to create west and northwest oriented North Platte River tributary drainage routes.

Detailed location map for Chugwater Creek-Goshen Hole drainage divide area

Figure 2: Detailed location map Chugwater Creek-Goshen Hole 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 Chugwater Creek-Goshen Hole drainage divide area east of the Wyoming Laramie Mountains. County lines are shown with Goshen County in the east, Platte County in the middle, and Albany County in west. The Laramie Mountains extend in a north to south direction in Albany County along the western margin of figure 2. The North Platte River flows in a southeast direction across the northeast corner of figure 2. The Laramie River flows from the west center edge of figure 2 in an east, northeast, east, and northeast direction to join the North Platte River near Fort Laramie (near north edge of figure 2). Chugwater Creek flows in a northeast direction from the south edge of figure 2 (west half) to the town of Chugwater (north of south center edge of figure 2) and then turns to flow in a north-northwest direction to Wheatland before turning in a northeast direction to join the Laramie River. The railroad is located in the Chugwater Creek valley for much of the distance between the south edge of figure 2 and Wheatland. Goshen Hole is labeled in Goshen County, although boundaries are not shown and the western rim of Goshen Hole extends into Platte County (near the town of Slater-see figure 3). Slater Flats is the an upland region between the north oriented Chugwater Creek valley and the Goshen Hole basin with Chugwater Flats being located south of Slater Flats. Today the western Goshen Hole basin has few drainage routes and those few drainage routes end as surface streams in Goshen Hole. Box Elder Creek for example originates on Chugwater Flats (just east of the town of Chugwater) and flows in a northeast direction into Goshen Hole and then ends as a surface stream. Likewise Chugwater Creek has few tributaries from the east with Eagles Nest Canyon (east and north of Wheatland) being a west, northwest, and north oriented drainage route to the Laramie River just east of where Chugwater Creek joins the Laramie River. Chugwater Creek does have a well-developed network of east and northeast oriented tributaries and some of those tributaries have southeast oriented tributaries. This pattern of tributaries suggests the north oriented Chugwater Creek valley eroded headward across east and maybe southeast oriented flood flow and caused the east oriented flood flow to flow in northeast directions to reach the actively eroding a much deeper Chugwater Creek valley.

Sybille Creek- Goshen Hole drainage divide area

Figure 3: Sybille Creek-Goshen Hole 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 Sybille Creek-Goshen Hole drainage divide area. The map contour interval for figure 3 is 10 meters except near the west edge and near the north edge where the contour interval is 20 meters. Goshen Hole is the escarpment-surrounded basin in the east half of figure 3 and is bounded by the Goshen Hole Rim. The Goshen Hole Rim was formed as a large east oriented headcut as immense volumes of east oriented floodwaters moved across the Laramie Mountains (located west of figure 3) into Goshen Hole and then to the southeast oriented North Platte River valley. To the east of figure 3 the Goshen Hole basin becomes much wider and is drained east of figures1, 2, and 3 by north and northeast oriented Horse Creek, which flows to the southeast oriented North Platte River. The Laramie River flows in a north-northeast direction from the west edge of figure 3 (north half) into the northwest corner of figure 3 and then turns to flow in an east and northeast direction to the north edge of figure 3 (east of center). North of figure 3 the Laramie River flows in a northeast direction to join the southeast oriented North Platte River. Chugwater Creek flows in a north, northwest, and north-northeast direction to join the Laramie River just south of the north center edge of figure 3. Slater Flats is the low relief upland surface between Chugwater Creek and Goshen Hole. Chugwater Creek has almost no tributaries from the east, but in the south half of figure 3 has numerous northeast-oriented tributaries. The northeast oriented tributary drainage routes were developed as the deep north oriented Chugwater Creek valley eroded headward across east oriented flood flow routes leading to the actively eroding Goshen Hole headcut face. Headward erosion of the deep north oriented Chugwater Creek valley captured the east oriented flood flow and diverted floodwaters to the east and northeast oriented Laramie River valley and in the process ended east oriented flood flow across Slater Flats to the Goshen Hole basin. The Laramie River valley floor elevation near where Chugwater Creek joins the Laramie River is approximately 1350 meters. The Goshen Hole floor elevation at its deepest point along the north to south oriented Platte County-Goshen County line is also approximately 1350 meters. Elevations on Slater Flats (the upland between Chugwater Creek and the Goshen Hole Rim) range from about 1550 meters to 1580 meters. East oriented floodwaters moving across Slater Flats to Goshen Hole were flowing on a surface at least 200 meters higher than the floor of the Laramie River valley or the Goshen Hole floor. Had the north oriented Chugwater Creek valley not beheaded flood flow routes to the Goshen Hole Rim headcut the Goshen Hole Rim headcut probably would have continued to erode headward and the Laramie River would today flow through Goshen Hole rather than flowing in a north-northeast, east, and northeast direction to the North Platte River on the northwest side of Goshen Hole. Sybille Creek is a north-northeast and north oriented stream flowing from the west edge of figure 3 (south half) to join the Laramie River near the northwest corner of figure 3 (where the Laramie River turns from flowing in a north-northeast direction to flowing in an east direction). Headward erosion of the deep north oriented Sybille Creek and tributary valleys beheaded east oriented flood flow moving to what were then newly formed east and northeast oriented Chugwater Creek tributary valleys.

Detailed map of Chugwater Creek-Goshen Hole drainage divide area

Figure 4: Detailed map of Chugwater Creek-Goshen Hole 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 Chugwater Creek-Goshen Hole drainage divide area seen in less detail in figure 3. The map contour interval for figure 4 is 20 feet. Chugwater Creek flows in a north and north-northwest direction from the south edge of figure 4 (west half) to the west edge of figure 4 (north of center). Bordeaux is the name of the railroad siding near the west edge of figure 4. The Goshen Hole Rim can be seen bordering the extreme west end of the Goshen Hole basin in the east half of figure 4. Between the Chugwater Creek valley rim and the Goshen Hole Rim is Slater Flats, which extends both to the north and to the south of figure 4. Slater Flats is not completely flat and a shallow west to east oriented through valley extends from the Chugwater Creek valley rim near the east margin of section 30 to the west end of the Goshen Hole Rim in section 28. The through valley floor elevation at the drainage divide is between 5160 and 5180 feet. Elevations reach 5212 feet in section 20 the north and exceed 5220 feet in section 32 to the south. These elevations suggest the through valley is at least 32 feet deep. Compared to the 400-foot deep Chugwater Creek valley to the west and the almost 1000-foot high Goshen Hole escarpment to the east (not all of the escarpment is seen in figure 4) the through valley appears to be almost insignificant. However, the through valley provides evidence of what was once an east oriented flood flow channel crossing the Slater Flats surface to reach the Goshen Hole Rim as the Goshen Hole valley head was being eroded headward into the Slater Flats surface. At the time floodwaters flowed in an east direction across the Slater Flats surface there was no deep north oriented Chugwater Creek valley. Several shallow depressions are seen on the Slater Flats surface such as the depression in section 34. These depressions may be karst features and/or they may have been eroded as floodwaters scoured the relatively flat Slater Flats surface. In either case the Slate Flats surface must be underlain by some type of erosion resistant material, which if the depressions are karst features probably suggests the resistant material may be limestone or a related rock type. It is possible the erosion resistant material was deposited by east oriented floodwaters at an earlier time. Apparently the erosion resistant material is not located west of the north oriented Chugwater Creek valley (or at least is not as thick) and the Chugwater Creek valley eroded headward along the western margin of the erosion resistant material, which is probably why the shallower north oriented Chugwater Creek valley was able to behead east oriented flood flow moving to the much deeper Goshen Hole basin.

Eagles Nest Canyon-Goshen Hole drainage divide area

Figure 5: Eagles Nest Canyon-Goshen Hole drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Eagles Nest Canyon-Goshen Hole drainage divide area seen in reduced size in the north half of figure 3. The map contour interval for figure 5 is 20 meters except near the south edge where the contour interval is 10 meters. The east oriented Laramie River can just barely be seen in the northwest corner of figure 5. The Laramie River valley floor elevation near the northwest corner of figure 5 is approximately 1350 meters. Little Cottonwood Draw is a northwest oriented drainage route in the northwest quadrant of figure 5 and drains to the east oriented Laramie River as a barbed tributary. The Little Cottonwood Draw valley alignment probably was determined by a reversal of southeast oriented flood flow triggered by headward erosion of the much deeper east oriented Laramie River valley. Eagles Nest Canyon is the northwest and west drainage route originating near Eagles Nest and draining to the west edge of figure 5 (north of center). West of figure 5 Eagles Nest Canyon drains in a northwest and north-northeast direction to join the east oriented Laramie River. The Eagles Nest Canyon alignment probably originated as southeast and east oriented flood flow channels, which were beheaded and reversed by headward erosion of the deep north-northeast oriented Eagles Nest Canyon valley segment from the deep Laramie River valley. Eagles Nest is located on the northern end of the Slater Flats upland surface where elevations are approximately 200 meters higher than the Laramie River valley floor. The northwest end of the Goshen Hole basin is located in the southeast quadrant of figure 5 and is bounded west of the county line by the Goshen Hole Rim. Elevations near the southeast corner of figure 5 are between 1300 and 1350 meters or approximately 200 meters lower than on the Slater Flats upland surface. Cherry Creek in the east half of figure 5 flows in an east direction to the east edge of figure 5 (north of center). East of figure 5 most Cherry Creek flow is diverted to irrigation canals although Cherry Creek continues to flow in an east direction and eventually joins the southeast oriented North Platte River. East and slightly south of Eagles Nest there is an erosional residual where elevations exceed 1600 meters. This erosional residual is streamlined (at least to some extent) in a west-northwest to east-southeast direction and provides evidence of east-southeast oriented flood flow that once moved across the north end of the Slater Flats upland surface to the Cherry Creek headwaters and to southeast oriented drainage routes flowing down the southeast-facing Goshen Hole escarpment face.

Detailed map of Eagles Nest Canyon-Goshen Hole drainage divide area

Figure 6: Detailed map of Eagles Nest Canyon-Goshen Hole 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 Eagles Nest Canyon-Goshen Hole drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 20 feet. Eagles Nest is located in section 14 in the northwest quadrant of figure 6 and Eagles Nest Canyon drains in a northwest direction from near Eagles Nest to the west edge of figure 6 (near northwest corner). West and north of figure 6 Eagles Next Canyon drains in a west, northwest, and north-northeast direction to join the east and northeast oriented Laramie River. The northwest oriented stream flowing to the north edge of figure 6 in section 12 is an Eagles Nest Canyon tributary. Cherry Creek originates in the south half of section 17 and flows in an east-northeast direction to the east edge of figure 6. East of figure 6 Cherry Creek turns to flow in a southeast direction into the Goshen Hole basin and then turns to flow in more of an east and northeast direction and joins the southeast oriented North Platte River. The northeast oriented stream originating north of Cherry Creek and flowing to the north edge of figure 6 (near northeast corner) is a Deer Creek tributary, which north and east of figure 6 flows in a northeast, north, and northeast direction to join the Laramie River just before the Laramie River joins the southeast oriented North Platte River.  The south-facing escarpment in the southeast corner of figure 6 is the northwest rim of the Goshen Hole escarpment. A northwest to southeast oriented erosional residual is located in sections 13, 18, 19, and 20 and reaches a high elevation of 5389 feet. Elevations on the Eagles Nest Canyon-Deer Creek drainage divide as seen in figure 6 decrease in north direction and are less than 5100 feet north of figure 6. In the south half of section 26 there is a northwest to southeast oriented through valley crossing the Eagles Nest Canyon-Goshen Hole drainage divide where elevations are less than 5100 feet. Slightly south and west of figure 6 at least some elevations on the Slater Flats upland surface exceed 5200 feet suggesting the through valley is as much as 100 feet deep. The through valley floor elevation on the southwest side and the elevations on the north side suggest the erosional residual in sections 13, 18, 19, and 20 is at least 289 feet high. The erosional residual provides evidence the Slater Flats upland surface was once higher than it is today and marks the northern boundary of the Slater Flats upland surface. The northwest to southeast oriented through valley provides evidence of southeast oriented flood flow across the Slater Flats upland surface on the southwest side of the erosional residual while southeast oriented flood flow on the northeast side of the erosional was captured first by headward erosion of the east-northeast oriented Cherry Creek valley and subsequently by headward erosion of the deeper northeast oriented Deer Creek valley.

Richeau Creek-Goshen Hole drainage divide area

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

Figure 7 illustrates the Richeau Creek-Goshen Hole drainage divide area seen in reduced size in figure 3 and also includes a region south of figure 3. The map contour interval for figure 7 is 10 meters. Chugwater Creek flows in a north and north-northwest direction from the south center edge of figure 7 to the north edge of figure 7 (west half). North of figure 7 Chugwater Creek turns to flow in a north-northeast direction to join the east and northeast oriented Laramie River, which then flows to the southeast oriented North Platte River. Elevations in the Chugwater Creek valley near the north edge of figure 7 are approximately 1470 meters. Slater Flats is located east of the Chugwater Creek valley and the Goshen Hole Rim extends in a south and southeast direction from the north edge of figure 7 (east of center) to the east center edge of figure 1. The Goshen Hole basin is located to the north and east of the Goshen Hole Rim. Elevations in Goshen Hole basin near the northeast corner of figure 7 are 1350 meters while elevations on Slater Flats range from about 1580 meters in the north to more than 1620 meters in the south. With one exception Chugwater Creek has no tributaries from the east, but there are several well-developed northeast oriented tributaries from the west. From south to north the named northeast oriented tributaries are Richeau Creek, Hunton Creek, and Antelope Creek. While not seen in figure 7 these streams all have east or southeast oriented headwaters or tributaries further to the west. The difference between landforms on the two sides of the Chugwater Creek valley is probably related to underlying geology with some type of erosion resistant material underlying Slater Flats and either absent or much thinner (or easier to erode) on the east side of the Chugwater Creek valley. East oriented flood flow moving into the deep Goshen Hole basin was eroding the Goshen Hole Rim headcut face headward in a west direction from the deep southeast oriented North Platte River valley, but headward erosion of the North Platte River valley and its Laramie River valley to the north of the Slater Flats erosion resistant material created a situation where the deep north oriented Chugwater Creek valley could erode headward in a south direction along the west side of the Slater Flats erosion resistant materials to capture the east oriented flood flow. Captured flood flow routes then turned in northeast directions to flow to what was then the actively eroding and north oriented Chugwater Creek valley head and created northeast oriented Chugwater Creek tributary drainage routes in the process. Headward erosion of the north oriented Chugwater Creek valley ended all east oriented flood flow across Slater Flats and into the Goshen Hole basin

Detailed map of Slater Flats-Chugwater Creek drainage divide area

Figure 8: Detailed map of Slater Flats-Chugwater 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 Slater Flats-Chugwater Creek drainage divide seen in less detail in figure 7. The map contour interval for figure 8 is 20 feet. Chugwater Creek flows in a north direction from near the southwest corner of figure 8 to the west center edge of figure 8. West and north of figure 8 Chugwater Creek flows in a north-northwest and north-northeast direction to join the east and northeast oriented Laramie River, which then flows to the southeast oriented North Platte River. East of the north oriented Chugwater Creek valley is the Slater Flats upland surface and in the northeast corner of figure 8 is the Goshen Hole Rim and a small section of the northeast-facing Goshen Hole escarpment. Small depressions can be seen on the Slater Flats upland surface with the deepest depressions being defined by three contour lines. These depressions suggest the Slater Flats upland surface is underlain by limestone or a similar rock type, which is subject to the development of karst features. Another possible origin for the depressions is erosion as floodwaters scoured the Slater Flats upland surface. In either case cliffs along the Goshen Hole Rim suggest Slater Flats upland surface is underlain by more than 200 feet of erosion resistant material while cliffs along the Chugwater Creek east wall suggest the upland surface is underlain by less than 100 feet of erosion resistant material. This difference in the thickness of the erosion resistant material probably played a major role in the ability of the deep north oriented Chugwater Creek valley to erode headward across east oriented floodwaters flowing across the Slater Flats upland surface to reach the much deeper Goshen Hole Basin. The Goshen Hole Rim headcut could not erode headward as fast as the Chugwater Creek valley nd as a result headward erosion of the north oriented Chugwater Creek valley captured the east oriented flood flow that had been moving to the Goshen Hole Rim headcut and then into Goshen Hole. A short southwest oriented Chugwater Creek tributary valley in sections 16, 17, and 20 suggests headward erosion of the deep north oriented Chugwater Creek valley may have occurred rapidly enough that floodwaters were left stranded on the Slater Flats surface and then drained in a southwest direction to the newly eroded Chugwater Creek valley. The southwest oriented tributary valley may have originated as a northeast oriented flood flow route leading to the Goshen Hole Rim and escarpment face and then was beheaded and reversed by headward erosion of the deeper Chugwater Creek valley.

Chugwater Creek-Box Elder Creek drainage divide area

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

Figure 9 illustrates the Chugwater Creek-Box Elder Creek drainage divide area south and east of figure 7 and there is overlap with figure 7. The map contour interval for figure 9 is 10 meters. Chugwater Creek flows in a northeast direction to the town of Chugwater (near southwest corner of figure 9) and then turns to flow in a north direction to the northwest corner of figure 9. North of figure 9 Chugwater Creek flows in a north-northwest and north-northeast direction to the east and northeast oriented Laramie River, which then flows to the southeast oriented North Platte River. Chugwater Creek crosses the 1500-meter contour near the north edge of figure 9 and crosses the 1600-meter contour line near the town of Chugwater. The Goshen Hole Rim extends in a southeast direction from the north edge of figure 9 (west of center) to the east edge of figure 9 (south half) and a small area on the Goshen Hole basin floor can be seen near the northeast corner of figure 9 at the base of the northeast-facing escarpment slope. The 1350-meter contour line crosses the northeast corner of figure 9. Slater Flats is located between the Chugwater Creek valley and the Goshen Hole Rim in the north half of figure 9. Further south Chugwater Flats is the upland surface name near Chugwater Creek while Iowa Central Flats is the upland surface name closer to the Goshen Hole Rim. Elevations on Slater Flats are generally less than 1600 meters and elevations on Chugwater Flats are generally greater than 1650 meters while elevations on Iowa Central Flats are generally between 1600 and 1650 meters. A few small depressions are found on all three of the surfaces suggesting the three surfaces have similar origins. Box Elder Creek originates near the north edge of the Chugwater Flats surface in the southwest quadrant of figure 9 and flows in a northeast direction to a deep northeast oriented canyon carved into the Goshen Hole Rim and then to Glomill Reservoir at the base of the northeast-facing escarpment slope. From Glomill Reservoir Box Elder Creek flows in a north direction toward east and northeast oriented Cheery Creek (which flows to the North Platte River), but Box Elder Creek ends as a surface stream before reaching Cherry Creek (Box Elder Creek water appears to be used for irrigation in the Goshen Hole Basin). The northeast oriented Box Elder Creek canyon suggests significant northeast oriented flood flow moved across the Goshen Hole Rim at this location after most flood flow to the Goshen Hole Rim had ended. West and south of figure 9 Chugwater Creek originates near the west margin of the Laramie Mountains and flows in an east and northeast direction to the town of Chugwater. Apparently east and northeast oriented floodwaters flowed from the Laramie Mountains on the Chugwater Creek alignment (although at elevation as high as the Chugwater Flats elevation) to and across the Goshen Hole Rim as the deep north oriented Chugwater Creek valley was eroding headward near the west edge of figure 9. When headward erosion of the deep north oriented Chugwater Creek valley reached the present day location of the town of Chugwater it captured the northeast oriented flood flow and diverted floodwaters in a north direction to the Laramie River valley. At the same time the deep Chugwater Creek knick point eroded headward along the present day northeast oriented Chugwater Creek valley south and west of figure 9 and probably along east oriented Chugwater Creek headwaters valleys in the Laramie Mountains. This evidence suggests floodwaters were still moving across the Laramie Mountains after all flood flow to the deep Goshen Hole basin had ended.

Richeau Creek-Chugwater Creek drainage divide area

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

Figure 10 provides a topographic map of the Richeau Creek-Chugwater Creek drainage divide area south and west of figure 9 and includes a small overlap area with figure 9. The map contour interval for figure 10 is 10 meters in the eastern two-thirds and 20 meters in the western third. Chugwater Creek flows in a northeast direction from near the southwest corner of figure 10 to near the northeast corner of figure 10. As seen in earlier figures north of figure 10 Chugwater Creek turns to flow in a north, north-northwest, and north-northeast direction to join the east and northeast oriented Laramie River, which then joins the southeast oriented North Platte River. South and west of figure 10 Chugwater Creek originates near the west edge of the Laramie Mountains and Chugwater Creek headwaters flow in an east direction before turning to flow in a northeast direction (see Sybille Creek-Chugwater Creek drainage divide area essay). North Chugwater Creek (“Creek” in figure 10) flows from the west edge of figure 10 (south of center) in an east and southeast direction to join northeast oriented Chugwater Creek near the small community of Diamond. Richeau Creek flows from the west center edge of figure 10 in an east and north-northeast direction to the north edge of figure 10 (west of center) and north of figure 10 flows in a northeast direction to join north oriented Chugwater Creek. Watergap Canyon Creek is the southeast oriented Richeau Creek tributary flowing from near the northwest corner of figure 10. The Chugwater Flats upland surface is located east of figure 10 and does not appear to continue westward into figure 10 where stream valleys have been eroded into most regions. The northeast oriented Chugwater Creek valley alignment probably originated as a northeast oriented flood flow channel moving floodwaters from the Laramie Mountains to the west of figure 10 to the Goshen Hole basin as seen in figure 9, although at that time the flood flow was moving on a surface at least as high as the Chugwater Flats elevation to the northeast. Southeast oriented tributary valleys probably originated as southeast oriented flood flow channels captured by the northeast oriented flood flow channel. Headward erosion of the deep north oriented Chugwater Creek valley to near the northeast corner of figure 10 captured the northeast oriented flood flow channel and diverted the floodwaters to the Laramie River valley and ended the final flood flow into the Goshen Hole basin. Headward erosion of the northeast-northeast and northeast oriented Richeau Creek valley from the newly eroded north oriented Chugwater Creek valley captured southeast oriented flood flow moving to the northeast oriented Chugwater Creek flood flow channel, although further to the west in the Laramie Mountains enough floodwaters still entered the Chugwater Creek valley and tributary valleys to erode the deep north oriented Chugwater Creek knick point headward across the region seen in figure 10.

Additional information and sources of maps studied

This essay has provided only a sample of the detailed topographic map evidence supporting the flood erosion interpretation. Many additional illustrations could be provided. Readers are encouraged to look at mosaics of detailed topographic maps to see the abundance of available data. Maps used in this study were created and published by the United States Geologic Survey and can be obtained directly from the United States Geological Survey and/or from dealers offering United States Geological Survey maps. Hard copy maps can also be observed at United States Geological Survey map depositories, which are located throughout the United States and elsewhere. Illustrations used here were created using National Geographic Society TOPO software and digital map data. TOPO software and map data can be obtained from the National Geographic Society and/or dealers offering National Geographic Society digital map data.

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