North Platte River-Little Snake River drainage divide area landform origins along the continental divide in the Wyoming and Colorado Sierra Madre Mountains, USA

Authors

 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the North Platte River-Little Snake River drainage divide in the Wyoming and Colorado Sierra Madre Mountains. The Sierra Madre Mountains are a northwest to southeast oriented mountain range straddling the Wyoming-Colorado border. The North Platte River flows in a north-northwest direction on the northeast side of the Sierra Madre Mountains and then continues in a north, east, and southeast direction around the northwest end of the Laramie Mountains into Nebraska with water eventually reaching the Gulf of Mexico. The Encampment River flows in a north direction to join the North Platte River and is joined several barbed tributaries. Further, through valleys link Encampment River tributary valleys with each other suggesting they originated as anastomosing flood flow channels. Little Snake River headwaters drain the southwest side of the Sierra Madre Mountains with the Little Snake River then flowing in a west and southwest direction with water eventually reaching the Pacific Ocean. Through valleys or mountain passes link headwaters valleys of northeast oriented North Platte River tributaries with each other and with headwaters valleys of Little Snake River tributaries. Through valleys crossing present day drainage divides, including the continental divide, the barbed tributaries, and the evidence of former anastomosing channels is interpreted in the context of immense south oriented floods that flowed across the region at a time when the Sierra Madre Mountains were beginning to emerge and which at first were able to flow across the emerging mountain range. Emergence of the Sierra Madre Mountains and other regional mountain ranges occurred as floodwaters deeply eroded the surrounding valleys and basins and as ice sheet related crustal warping raised the mountain ranges. Floodwaters are interpreted to have flowed from the western margin of a thick North American ice sheet in western Canada to and across Wyoming. South oriented flood flow on the present day north oriented North Platte River alignment was reversed when headward erosion of a much deeper southeast oriented valley eroded headward around the northwest end of the Laramie Mountains. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to flow in a north direction to the much deeper east and southeast oriented valley and to create the north, east, and southeast oriented North Platte River drainage route. The reversal of flood flow on the North Platte River alignment was greatly aided by ice sheet related crustal warping that raised the Sierra Madre Mountains and the entire North Platte River headwaters area.

Preface

The following interpretation of detailed topographic map evidence is one of a series of essays describing similar evidence for all major drainage divides contained within the Missouri River drainage basin and for all major drainage divides with adjacent drainage basins. The research project is interpreting evidence in the context of a previously unexplored deep glacial erosion paradigm, which is fundamentally different from most commonly accepted North American glacial history interpretations. Project essays are listed on the sidebar category list under their appropriate Missouri River tributary drainage basin, Missouri River segment drainage basin (by state), and/or state in which the Missouri River drainage basin is located.

Introduction

The purpose of this essay is to use topographic map interpretation methods to explore the North Platte River-Little Snake River drainage divide area landform origins in the Wyoming and Colorado Sierra Madre Mountains. Map interpretation methods can be used to unravel many geomorphic events leading up to formation of present-day drainage routes and development of other landform features. While each detailed topographic map feature provides detailed evidence to be explained, the solution must be consistent with explanations for adjacent area map evidence as well as solutions to big picture map evidence puzzles. I invite readers to improve upon my solutions and/or to propose alternate solutions that better explain evidence and are also consistent with adjacent map area and big-picture evidence. Readers may do so either by making comments here or by writing and publishing their own essays and then by leaving a link to those essays in a comment here.

This essay is also exploring a new geomorphology paradigm in which erosional landforms are interpreted as evidence left by immense glacial melt water floods. Implied in that interpretation is the immense floods were derived from a thick North American ice sheet that created a deep “hole” in the North American continent and also melted fast. The previously unexplored paradigm being tested in this and other Missouri River drainage basin landform origins research project essays is a thick North American ice sheet, comparable in thickness to the Antarctic ice sheet, occupied the North American region usually recognized to have been glaciated, and through its weight and erosive actions created a deep North American “hole”. The southwestern rim of that deep “hole” is today preserved in the high Rocky Mountains. The ice sheet through its weight and deep erosion (and perhaps deposition along major south-oriented melt water flow routes) caused significant crustal warping and tectonic change, through its action of melting fast produced immense floods that flowed across the continent, and through its action of melting fast systematically opened up space in the ice sheet created “hole” so headward erosion of newly developed north-oriented drainage systems captured immense south-oriented melt water floods and diverted immense melt water floods north into space the ice sheet had once occupied.

If this previously unexplored paradigm is correct the geographic region explored by this essay should contain evidence of immense floods that were captured by headward erosion of new valley systems so as to cause the floods to flow in a different direction. Ability of this previously unexplored paradigm to explain North Platte River-Little Snake River drainage divide area landform evidence in the Wyoming and Colorado Sierra Madre Mountains will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

North Platte River-Little Snake River drainage divide area location map

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

Figure 1 provides a location map for the North Platte River-Little Snake River drainage divide area in the Wyoming and Colorado Sierra Madre Mountains and illustrates a region in southern Wyoming with Colorado and Utah south of Wyoming (Utah is in the southwest corner of figure 1). The North Platte River originates west of Rocky Mountain National Park (near southeast corner of figure 1) and flows in a north-northwest direction between the Medicine Bow Mountains and the Sierra Madre Mountains into Wyoming and then in a north 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 in a southeast direction across the northeast corner of figure 1 (at Glendo) to enter Nebraska with water eventually reaching the Gulf of Mexico. The Encampment River is the unlabeled north oriented stream originating at the south end of the Sierra Madre Mountains and joining the north-northwest oriented North Platte River north of the town of Encampment. Jack Creek is the unlabeled northeast oriented stream originating in the Sierra Madre Mountains and joining the North Platte River near the town of Saratoga. The Green River is the south oriented river flowing through the Flaming Gorge National Recreation Area and Dinosaur National Monument on its way to the southwest corner of figure 1. South and west of figure 1 the Green River joins the Colorado River with water eventually reaching the Pacific Ocean. The Yampa River is the west oriented river flowing from Steamboat Springs, Colorado to join the Green River in Dinosaur National Monument. The Little Snake River is a northwest, west, and southwest oriented tributary joining the Yampa River near the east border of Dinosaur Nation Monument and the west oriented segment is located along the Wyoming-Colorado border near the towns of Savery, Dixon, and Bagga. Little Snake River headwaters drain the west side of the Sierra Madre Mountains. Muddy Creek is a northwest, west, and south oriented tributary joining the Little Snake River near Baggs. South of the north oriented Encampment River headwaters are headwaters of the southwest and south oriented Elk River that flows to the west oriented Yampa River near Steamboat Springs. The Elk River flows in a southwest and south direction from the south end of the Sierra Madre Mountains to join the Yampa River near Steamboat Springs. The North Platte River-Little Snake River drainage divide area along the continental divide in the Wyoming and colorado Sierra Madre Mountains investigated in this essay is located in the region between the Jack Creek headwaters and the Encampment River headwaters (just south of the Wyoming border). A separate essay addresses landform evidence along the North Platte River-Little Snake River drainage divide in the Wyoming northern Sierra Madre Mountains.

Drainage routes in Wyoming, Colorado, and Utah developed during immense melt water floods from the western margin of a thick North American ice sheet which flowed from western Canada to and across Wyoming at a time when Wyoming and other regional mountain ranges were emerging. Mountain ranges, including the Sierra Madre Mountains, emerged as floodwaters deeply eroded surrounding basins and valleys and as ice sheet related crustal warping raised the mountain ranges and entire regions in Wyoming, Colorado, and Utah. The present day north oriented North Platte River alignment west of the Laramie Mountains originated as a south oriented flood flow route (actually many south oriented flood flow routes, although for purposes of brevity this essay only refers to a single route on the North Platte River alignment). Diverging flood flow channels moved floodwaters from the south oriented North Platte River flood flow route in southwest and south directions across the emerging Sierra Madre Mountain to actively eroding Little Snake River tributary and headwaters valleys and also to the actively eroding southwest and south oriented Elk River valley. Emergence of the Sierra Madre Mountains systematically ended flood flow across the rising mountain mass and also contributed to a massive reversal of flood flow on the North Platte River alignment. The North Platte River flood flow reversal west of the Laramie Mountains was triggered by headward erosion of the much deeper southeast oriented North Platte River valley, which eroded headward on the east side of the Laramie Mountains. That deep  southeast oriented North Platte River valley eroded headward around the northwest end of the Laramie Mountains and beheaded the south oriented flood flow channel(s) west of the Laramie Mountains. Floodwaters on the north end(s) of the beheaded flood flow channel(s) reversed flow direction to flow in a north direction to the much deeper east and southeast oriented valley and to create the present day north, east, and southeast oriented North Platte River drainage route. Ice sheet related crustal warping that was raising the Sierra Madre Mountains and the North Platte River headwaters area greatly aided in this North Platte River flood flow reversal, which also ended all flood flow movements across the emerging Sierra Madre Mountains from the North Platte River alignment to what had been actively eroding Little Snake River and Elk River headwaters and tributary valleys.

Detailed location map for North Platte River-Little Snake River drainage divide area

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

Figure 2 provides a more detailed location map for the North Platte River-Little Snake River drainage divide area in the Wyoming and Colorado Sierra Madre Mountains. The west to east oriented Wyoming-Colorado state line is located in the south half of figure 2. The east-west continental divide is shown with a labeled dashed line extending from the north edge of figure 2 (west half) to the south edge of figure 2 (east half). The green colored areas are National Forest lands, which are usually located in mountain areas. The green colored area along the east edge of figure 2 is located in the Medicine Bow Mountains and the green colored in the center and south center areas of figure 2 is located in the Sierra Madre Mountains. The North Platte River flows in a northwest and north-northwest direction from the east edge of figure 2 (south half) along the northeast side of the Beaver Creek Hills to the towns of Cow Creek, Davis, and Saratoga with water eventually reaching the Gulf of Mexico. The Encampment River originates near where the continental divide crosses the south edge of figure 2 and flows in a north direction to the town of Encampment and then joins the North Platte River south of Cow Creek. The northeast oriented North Fork joins the Encampment River near the town of Encampment. Cow Creek is a northeast oriented tributary joining the North Platte River near the town of Cow Creek. Northeast oriented South and North Spring Creeks meet south of Saratoga to form northeast oriented Spring Creek, which then joins the North Platte River. West of the continental divide the North and East Forks of Savery Creek originate near Divide Peak (at north end of green colored area) and the meet to form southwest and south oriented Savery Creek, which flows to the west oriented Little Snake River near the town of Savery. East and south of Savery Creek is southwest oriented Battle Creek, which joins the west oriented Little Snake River near Battle Mountain. Further to the south and east is the southwest oriented North Fork Little Snake River, which joins the northwest oriented Middle Fork and north oriented South Fork to form the west oriented Little Snake River near the Wyoming-Colorado state line. West of figure 2 the Little Snake River turns to flow in a southwest direction to join the west oriented Yampa River with water eventually reaching the Pacific Ocean. South of figure 2 and south of the Encampment River headwaters are headwaters of southwest and south oriented Elk River, which also flows to the west oriented Yampa River.

North Spring Creek-South Spring Creek drainage divide area

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

Figure 3 provides a topographic map of North Spring Creek-South Spring Creek drainage divide area. The map contour interval for figure 3 is 20 meters in the west and 50 meters in the east. Divide Peak is located near the northwest corner of figure 3. The east-west continental divide extends in a southeast direction from Divide Peak along the Sierra Madre Mountains crest to the south edge of figure 3 (east of center). Bridger Peak is a high point on the continental divide north of the south center edge of figure 3. South Spring Creek Lake is located north of Bridger Peak and South Spring Creek flows in a northeast direction from South Spring Creek Lake to the northeast corner of figure 3. North Spring Creek Lake is located west and north of South Spring Creek Lake. North Spring Creek flows in a north-northwest and northeast direction from North Spring Creek Lake to the north edge of figure 3 (west of center). North of figure 3 North and South Spring Creek join to form northeast oriented Spring Creek, which then flows to the north-northwest oriented North Platte River with water eventually reaching the Gulf of Mexico. The unlabeled north-northwest and north oriented stream west of North Spring Creek is Jack Creek, which north of figure 3 also flows to the North Platte River. East of South Spring Creek Lake is Vulcan Mountain and south of Vulcan Mountain are headwaters of southeast oriented Cow Creek, which is joined by northeast oriented Nellie Creek and which then turns to flow in a northeast direction to the east edge of figure 3 (south half). East of figure 3 Cow Creek flows to the north-northwest oriented North Platte River. A northwest to southeast oriented through valley links the north-northwest oriented Jack Creek and North Spring Creek valleys with the South Spring Creek Lake Basin and the southeast oriented Cow Creek headwaters. Between North and South Spring Creek Lakes the through valley floor elevation is between 3000 and 3020 meters. Mowry Peak to the north reaches 3149 meters and much higher elevations are found along the continental divide to the southwest suggesting the through valley is at least 120 meters deep. Between South Spring Creek Lake and the Cow Creek valley the through valley floor elevation is between 3060 and 3080 meters. Vulcan Mountain rises to 3287 meters and Bridger Peak reaches 3344 meters suggesting the through valley is at least 200 meters deep. These through valleys are water-eroded features and were eroded by a southeast oriented flood flow channel flowing along the northeast flank of the emerging Sierra Madre Mountains. West of the continental divide streams flowing to the west edge of figure 3 are tributaries of south oriented Savery Creek and streams flowing to the south edge of figure 3 are tributaries of southwest oriented Battle Creek. Savery Creek and Battle Creek both flow to the west and southwest oriented Lake Snake River with water eventually reaching the Pacific Ocean.

Detailed map of North Spring Creek-South Spring Creek drainage divide area

Figure 4: Detailed map of North Spring Creek-South Spring 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 North Spring Creek-South Spring Creek drainage divide area seen in less detail in figure 3. The map contour interval for figure 4 is 40 feet. North Spring Creek Lake is located in section 4 and North Spring Creek flows in a north direction from North Spring Creek Lake to the north edge of figure 4. North of figure 4 North Spring Creek turns to flow in a northeast direction to join South Spring Creek and to form northeast oriented Spring Creek, which flows to the north-northwest oriented North Platte River. South Spring Creek Lake is located in the northwest corner of section 11 and the southwest corner of section 2 and South Spring Creek flows in a north-northeast direction from South Spring Creek Lake to the north edge of figure 4 (near northeast corner). Cow Creek originates in the southeast quadrant of section 12 and flows in a southeast direction to the southeast corner of figure 4. South and east of figure 4 Cow Creek turns to flow in a northeast direction to join the North Platte River. A northwest to southeast oriented through valley (or pass) links the South Spring Creek Lake basin with the southeast oriented Cow Creek headwaters valley. The through valley floor elevation is between 10,040 and 10,080 feet. Vulcan Mountain in section 1 rises to 10,784 feet. Elevations greater than 10,800 feet are found along the south edge of figure 4 (south of South Spring Creek Lake). These elevations suggest the through valley is at least 700 feet deep. A through valley also links the North Spring Creek Lake basin with the South Spring Creek Lake basin and has a floor elevation of between 9840 and 9880 feet. Elevations in section 35 reach 10,203 feet and Mowry Peak (north of figure 4) reaches 10,313 feet in elevation. Based on these elevations the through valley is at least 420 feet deep.  The through valleys were eroded by southeast oriented flood flow moving along the northeast flank of the emerging Sierra Madre Mountains. Headward erosion of the deeper north-northeast oriented South Spring Creek valley captured the southeast oriented flood flow and diverted the floodwaters in a north direction to the deeper North Platte River valley. Next a reversal of flood flow on the present day north oriented North Spring Creek alignment captured the southeast oriented flood flow. The sequence of captures suggest the South and North Spring Creek valleys eroded headward from a deeper south oriented flood flow channel on the present day north oriented North Platte River alignment. If correctly interpreted the reversal of flood flow on the North Platte River alignment took place after the flood flow capture events illustrated and discussed here.

Nellie Creek-Battle Creek drainage divide area

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

Figure 5 illustrates the Nellie Creek-Battle 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 in the western section and 50 meters in the eastern section. The east-west continental divide is located along the crest of the Sierra Madre Mountains and is shown with a labeled line extending from the north edge of figure 5 (west half) to the south edge of figure 5 (near southeast corner). South Spring Creek Lake is located south of north center edge of figure 5 and Cow Creek originates south and east of South Spring Creek Lake. Cow Creek flows in a southeast direction until it is joined by northeast oriented Nellie Creek and then turns to flow in a northeast direction to near the northeast corner of figure 5. North and east of figure 5 Cow Creek joins the north-northwest oriented North Platte River with water eventually reaching the Gulf of Mexico. Bridger Peak is located south of South Spring Creek Lake. Battle Lake is located south and east of Bridger Peak. Battle Creek originates near Battle Lake and flows in a southwest direction to near the southwest corner of figure 5. West of figure 5 Battle Creek flows to the west and southwest oriented Little Snake River with water eventually reaching the Pacific Ocean. A through valley (or pass) is located on the Nellie Creek-Battle Creek drainage divide near the place-name “Battle”. The through valley floor elevation is between 3000 and 3050 meters. Red Mountain to the south rises to 3203 meters and elevations to the northwest rise much higher suggesting the through valley (or pass) is at least 150 meters deep. While today this through valley appears insignificant compared to the much deeper valleys in either direction the through valley was eroded by water at a time when those surrounding valleys did not exist and the Sierra Madre Mountains did not stand high above surrounding regions. Probably the through valley was eroded by southwest oriented flood flow moving to what at that time was an actively eroding Battle Creek valley from a south oriented flood flow channel on the present day north oriented North Platte River alignment. The Sierra Madre Mountains emerged as floodwaters deeply eroded the surrounding valleys and as ice sheet related crustal warping raised the Sierra Madre Mountains above surrounding regions.

Detailed map of Nellie Creek-Battle Creek drainage divide area

Figure 6: Detailed map of Nellie Creek-Battle 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 Nellie Creek-Battle Creek drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 40 feet. The east-west continental divide is shown with a labeled dashed line extending from near the northwest corner of figure 6 to the south center edge of figure 6. Cow Creek flows from the north center edge of figure 6 in a southeast direction to the northeast corner of section 21 and then turns to flow in a northeast direction to the east edge of figure 6 (near northeast corner). East and north of figure 6 Cow Creek joins the North Platte River with water eventually reaching the Gulf of Mexico. Nellie Creek originates near the former Battle town site and flows in a northeast direction to join Cow Creek. Battle Creek originates near the south center edge of figure 6 (just west of the continental divide) and flows in a north-northwest direction into the northeast quadrant of section 25 where it turns to flow in a southwest direction to the west edge of figure 6. West of figure 6 Battle Creek flows to the west and southwest oriented Little Snake River with water eventually reaching the Pacific Ocean. The former town of Battle is located near the northwest corner of section 29 and Battle Pass is located in the southwest corner of section 20 immediately to the north (near center of figure 6). Battle Pass has an elevation of between 9800 and 9840 feet. Red Mountain located just south of figure 6 rises to 10,508 feet. Bridger Peak to the north of figure 6 rises to 11,004 feet. These elevations suggest Battle Pass is almost 700 feet deep if not deeper. Battle Pass was eroded at a time when the Sierra Madre Mountains did not stand high above surrounding regions and it was possible for floodwaters to flow across what is today a high mountain range. Based on figure 6 evidence alone it is difficult to say which way the water was moving when the Battle Pass valley was eroded, although based on evidence from a larger region my interpretation is the water was moving in a southwest direction from the present day northeast oriented Nellie Creek and Cow Creek alignment to the present day southwest oriented Battle Creek alignment. If correctly interpreted the southwest oriented flood flow helped erode the Sierra Madre Mountains southwest side. After the Battle Pass valley had been eroded and abandoned large volumes of southeast oriented flood flow on the southeast oriented Cow Creek headwaters alignment was captured by headward erosion of the deeper northeast oriented (and reversed) Cow Creek valley. This southeast and northeast oriented flood flow on the Cow Creek alignment helped erode the northeast side of the Sierra Mountains.

North Fork Encampment River-North Fork Little Snake River drainage divide area

Figure 7: North Fork Encampment River-North Fork Little Snake River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the North Fork Encampment River-North Fork Little Snake River drainage divide area east and slightly south of figure 5 and includes a large overlap area with figure 5. The map contour interval for figure 7 is 50 meters except near the west edge where the contour interval is 20 meters. The continental divide is shown with a labeled line extending from the west edge of figure 7 (north half) to the south edge of figure 7 (west of center). The Encampment River flows in a north direction from the south edge of figure 7 (east half) to the north edge of figure 7 (east half). North of figure 7 the Encampment River joins the North Platte River with water eventually reaching the Gulf of Mexico. There are several south oriented streams flowing as barbed tributaries to the north oriented Encampment River near the south edge of figure 7. These barbed tributaries provide evidence the Encampment River may have originated as a south oriented drainage route with the direction of drainage later being reversed to create the north oriented drainage route seen today. Battle Pass and the site of Battle are located near the northwest corner of figure 7. Red Mountain is located south of Battle. The North Fork Encampment River originates near the continental divide south and west of Red Mountain and then flows in a northeast direction to the north edge of figure 7 (west half) and joins the north oriented Encampment River north of figure 7. The Roaring Fork Little Snake River originates near the Standard Mine (just east of west center edge of figure 7) and flows in a southwest direction to the west edge of figure 7. West of figure 7 the Little Snake River flows in a west and southwest direction to join the Yampa River with water eventually reaching the Pacific Ocean. The west and south-southwest oriented stream flowing to the southwest corner of figure 7 is the West Branch North Fork Little Snake River. Further east, but west of the continental divide, are west and south-southwest oriented headwaters of the North Fork Little Snake River with south-southeast oriented Deadman Creek being a tributary. Shallow north to south oriented through valleys link north oriented North Fork Encampment River tributary valleys with south oriented North Fork Little Snake River tributary and headwaters valleys. These through valleys are generally defined by a single 50-meter contour interval on a side, so are much better seen on more detailed topographic maps. The through valleys do however provide evidence of what were multiple south oriented flood flow channels that once crossed the present day Sierra Madre Mountains prior to the emergence of the Sierra Madre Mountains as a high mountain range.

Detailed map of North Fork Encampment River-North Fork Little Snake River drainage divide area

Figure 8: Detailed map of North Fork Encampment River-North Fork Little Snake River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 provides a detailed topographic map of the North Fork Encampment River-North Fork Little Snake River drainage divide seen in less detail in figure 7. The map contour interval for figure 8 is 40 feet. The east-west continental divide is shown with a labeled dashed line extending from the north edge of figure 8 (east of center) to Red Mountain and then to north of Standard Park and across Huston Park before continuing to the east edge of figure 8 (near southeast corner). The North Fork Encampment River originates near the continental divide in the region north and east of Standard Park and then flows in a north direction to Long Park where it turns to flow in an east-northeast direction to the east edge of figure 8 (near northeast corner) and east and north of figure 8 joins the north oriented Encampment River which then flows to the North Platte River with water eventually reaching the Gulf of Mexico. The Roaring Fork Little Snake River originates in Standard Park and flows in a southwest direction to the south edge of figure 8 (west half) and south and west of figure 8 joins the west and southwest oriented Little Snake River with water eventually reaching the Pacific Ocean. The West Branch North Fork Little Snake River originates in section 8 (east of Standard Park) and flows in a southwest and south direction to the south center edge of figure 8 and south of figure 8 joins the west and southwest oriented Little Snake River. A north to south oriented through valley in the west half of section 8 links the north oriented North Fork Encampment River headwaters valley with the southwest and south oriented West Branch North Fork Little Snake River valley. The through valley floor elevation is between 10,160 and 10,200 feet. Elevations along the continental divide to the southeast rise to 10,515 in section 16 near the southeast corner of figure 8 and to the west elevations rise to 10,444 feet in section 12. These elevations suggest the through valley is at least 244 feet deep. The through valley is a water-eroded valley and was eroded by south oriented flood flow moving from the present day North Platte River drainage basin to the present day Little Snake River drainage basin. At the time floodwaters crossed the region the Sierra Madre Mountains did not stand high above the surrounding region and there was no deep North Platte River valley to the north and east, nor was there a deep Encampment River valley to the east. Probably there was a south oriented flood flow channel at that time on the present day north oriented Encampment River alignment. Further north in the north half of section 6 there is a through valley linking the west-southwest oriented Baby Lake Creek valley with North Fork Encampment River valley. The floor elevation of this second through valley is between 9960 and 10,000 feet. Red Mountain to the northeast rises to 10,508 feet and elevations in section 12 to the southwest rise to 10,444 feet suggesting this second through valley is at least 444 feet deep. West of figure 8 Baby Lake Creek flows to southwest oriented Battle Creek, which then flows to the Little Snake River. Similar through valleys can be found crossing the high Sierra Madre Mountains upland surface and provide evidence of anastomosing flood flow channels that had been eroded into the erosion surface now preserved by the present day high Sierra Madre Mountains upland surface.

Hog Park Creek-Encampment River drainage divide area

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

Figure 9 illustrates the Hog Park Creek-Encampment River drainage divide area south of figure 7 and there is an overlap area with figure 7. The map contour interval for figure 9 is 50 meters. The west to east oriented Wyoming-Colorado state line is located south of center in figure 9. The east-west continental divide is shown with a labeled dashed line extending from the north edge of figure 9 (west half) to the state line and then follows the Jackson-Routt County line in Colorado. The Middle Fork Little Snake River flows in a northwest direction across the southwest corner of figure 9. West of figure 9 the Middle Fork flows to the west and southwest oriented Little Snake River with water eventually reaching the Pacific Ocean. Whiskey Creek is a south-southwest oriented tributary joining the Middle Fork near the southwest corner of figure 9. East of the continental divide the Encampment River flows in a north, northwest, north, northeast, and north direction from the south edge of figure 9 (east of center) to the north center edge of figure 9. North of figure 9 the Encampment River flows to the North Platte River with water eventually reaching the Gulf of Mexico. The West Fork Encampment River flows in a north direction from the south center edge of figure 9 to join the northwest oriented Encampment River. The South Fork Hog Park Creek flows in a north direction from the south edge of figure 9 (west half) and joins southeast oriented Hog Park Creek near the point where Hog Park Creek turns to flow in a northeast direction to join the Encampment River at the point where the Encampment River turns to flow in a northeast direction. Other southeast oriented tributaries joining the north oriented Encampment River as barbed tributaries include Miller Creek and Olsen Creek. The East Fork Encampment River flows in a south-southwest, west and northwest direction to join the Encampment River as a barbed tributary from the east. Southwest oriented Conn Creek is a tributary to the south-southwest oriented East Fork segment. Damfino Creek is a west and northwest oriented tributary to the northwest oriented East Fork segment. Along the Wyoming-Colorado River state line a maze of through valleys link the South Fork Hog Park Creek valley with the Encampment River valley and with the East Fork valley and the Damfino Creek valley. These through valleys are defined by two or more contour lines on each side. The pattern of through valleys when combined with the present day drainage routes can best be described as the remains of what was once a south oriented anastomosing channel complex. South of figure 9 (and not illustrated in this essay) a through valley links the north oriented South Fork Hog Park Creek valley with the northwest oriented Middle Fork Little Snake River valley, which is linked by a through valley with a south oriented Elk River tributary valley. Also through valleys link the north oriented West Fork and Encampment River valleys with each and with south oriented Elk River tributary valleys with the Elk River flowing to the Yampa River and with water eventually reaching the Pacific Ocean. These additional through valleys provide further evidence supporting the south oriented anastomosing channel complex interpretation. In other words the present day north oriented Encampment River valley and tributary valleys originated as south oriented anastomosing channels flowing to actively eroding south oriented Elk River tributary valleys. South oriented flood flow in the Encampment River drainage basin was beheaded and reversed to create the north oriented Encampment River drainage system.

Detailed map of Hog Park Creek-Encampment River drainage divide area

Figure 10: Detailed map of Hog Park Creek-Encampment River 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 Hog Park Creek-Encampment River drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 40 feet. The west to east oriented Wyoming-Colorado state line is located north of center in figure 10. The entire region seen in figure 10 is north and east of the east-west continental divide and drains to the north oriented North Platte River with water eventually reaching the Gulf of Mexico. The Encampment River flows in a northwest, north, and northwest direction from the south edge of figure 10 (east half) to the north edge of figure 10 (west half). North of figure 10 the Encampment River flows to the North Platte River. South of figure 10 the north oriented Encampment River valley is linked by a 1500-foot deep through valley with a south oriented tributary valley draining to the southwest and south oriented Elk River with water eventually reaching the Pacific Ocean. The West Fork Encampment River flows in a north-northwest direction from the south center edge of figure 10 to join the northwest oriented Encampment River. South of figure 10 the West Fork valley is linked by a deep through valley with the Encampment River valley and by a shallower through valley with a south oriented tributary valley draining to the Elk River. The South Fork Hog Park Creek flows in a north direction from near the southwest corner of figure 10 to near the northwest corner of figure 10 where it joins southeast and northeast oriented Hog Park Creek, which north of figure 10 flows to the north oriented Encampment River. The East Fork Encampment River flows in a south-southwest, west and northwest direction from the north edge of figure 10 (east half) to join the Encampment River west of Beaver Dam Park. Damfino Creek flows in a northwest direction from the east center edge of figure 10 to join the East Fork in section 10. Through valleys link the South Fork Hog Park Creek valley with Encampment River valley and with the East Fork and Damfino Creek valleys. In section 15 a through valley links the South Fork Hog Park Creek valley with the Encampment Creek valley. The through valley floor elevation is 8534 feet. To the north elevations rise to more than 8760 feet and to the south elevations rise to 9081 feet suggesting the through valley is at least 225 feet deep. The through valley was eroded by southeast oriented flood flow on the present day southeast oriented Hog Park Creek alignment (north and west of figure 10-see figure 9), which was flowing to a south oriented flood flow channel on the present day north oriented Encampment River alignment. A second and deeper through valley is located south of state line in section PB 44 and also links the present day north oriented South Fork Hog Park Creek valley with the north oriented Encampment River valley. The through valley floor elevation is between 8560 and 8600 feet. Elevations to the north rise to 9081 feet and to the south elevations exceed 9200 feet suggesting the through valley is almost 500 feet deep, if not deeper. This second through valley was may have been eroded by southeast oriented flood flow on the Hog Park Creek alignment that continued after the flood flow reversal on the Encampment River alignment. If so southeast and south oriented flood flow on the Hog Park Creek alignment would have made U-turns to reach the newly reversed and then north oriented Encampment River drainage route. Such an interpretation suggests the reversal of flood flow on the Encampment River may have taken place before the North Platte River flood flow reversal. Assuming flood flow was still moving in a south direction on the North Plate River alignment south oriented flood flow could have diverged from the North Platte River alignment to reach the Hog Park Creek valley at a time when the Encampment River had begun to drain in a north direction.

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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