Nowood River-Powder River drainage divide area landform origins in the Wyoming Bighorn Mountains, USA

Authors

 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the region between Nowood River and Powder River in the Wyoming Bighorn Mountains. The Nowood River is located along the east side of southern Bighorn Basin and flows in a north direction along the Bighorn Mountains west flank before turning to flow in northwest direction into the Bighorn Basin to join the north oriented Bighorn River, which is a tributary to the northeast oriented Yellowstone River in Montana. The North Fork Powder River originates in the high Bighorn Mountains and flows in a southeast direction to join the northeast oriented Middle Fork Powder River and north-northeast oriented South Fork Powder River to form the east and north oriented Powder River, which flows in the Powder River Basin east of the Bighorn Mountains to the Yellowstone River in Montana. South and southwest oriented Nowood River tributaries originate near the North Fork Powder River headwaters and are linked by through valleys with the North Fork Powder River and North Fork Powder River tributary valleys. The Middle Fork Powder River and Middle Fork Powder River tributaries originate west of the Bighorn Mountains crest, have eroded deep water gaps across the Bighorn Mountains, and are linked by through valleys with west oriented Nowood River tributary valleys. Valley orientations, barbed tributaries, elbows of capture, water gaps, and through valleys all provide evidence the region was once crossed by diverging and converging southeast and south oriented flood flow channels at a time when the Bighorn Basin and Bighorn Mountains were not yet distinctive topographic features as they are today. Floodwaters are interpreted to have been derived from the western margin of a thick North American ice sheet and were flowing from western Canada to and across the study region. The Bighorn Mountains emerged as headward erosion of south oriented valleys in the Powder River Basin area first captured the south and southeast oriented flood flow and later as south oriented valleys in the Bighorn Basin area captured the flood flow. Ice sheet related crustal warping also raised the Bighorn Mountains as floodwaters were flowing across them as the thick ice sheet created a deep “hole” in which the ice sheet became located (the study region is located on what could be considered a segment of the deep “hole’s” southwest rim). Headward erosion of the deep northeast oriented Yellowstone River valley from space in the deep “hole’s” southern end being opened up by ice sheet melting beheaded the south and southeast oriented flood flow routes crossing Montana in sequence from east to west. Flood flow routes in the Powder River Basin were beheaded first and floodwaters on the north ends of the beheaded flood flow routes reversed flow direction to create the north oriented Powder River drainage route, which then captured southeast oriented flood flow moving across the present day Bighorn Mountains. Subsequently the actively eroding Yellowstone River valley head beheaded and reversed south oriented flood flow routes in the Bighorn Basin and floodwaters on north ends of the beheaded flood flow routes reversed flow direction to create the Bighorn River-Nowood River drainage route and its various tributary drainage routes. The Bighorn Mountains emerged as ice sheet related crustal warping raised them and as floodwaters deeply eroded the Powder River Basin to the east and the Bighorn Basin to the west.

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 Nowood River-Powder River drainage divide area landform origins in the Wyoming Bighorn 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 Nowood River-Powder River drainage divide area landform evidence in the Wyoming Bighorn Mountains will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Nowood River-Powder River drainage divide area location map

Figure 1: -Nowood River-Powder 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 Nowood River-Powder River drainage divide area in the Wyoming Bighorn Mountains and illustrates a region in north central Wyoming. The Bighorn Mountains are the north-south oriented mountain range labeled “Mountains” in the center of figure 1. The Powder River Basin is located east of the Bighorn Mountains and Bighorn Basin is located west of Bighorn Mountains and north of the Owl Creek Mountains. The Wind River Basin is located south of the Owl Creek Mountains. The Wind River flows in a southeast direction in the southwest quadrant of figure 1 to Riverton and then turns to flow in a northeast and north direction to Thermopolis where the river name changes to become the Bighorn River. North of Thermopolis the Bighorn River flows through the Bighorn Basin in a north direction to the north edge of figure 1 (west half) and north of figure 1 in Montana joins the northeast oriented Yellowstone River. The Nowood River is a northeast, north, and northwest oriented Bighorn River tributary flowing along the west side of the Bighorn Mountains. The North Fork Powder River originates near Powder River Pass in the Bighorn Mountains and flows in a south and southeast direction to join the northeast oriented Middle Fork Powder River near Kaycee and then flow in an east direction to join the north-northeast oriented South Fork Powder River. After flowing in an east direction into the Powder River Basin the Powder River turns to flow in a north direction to the north edge of figure 1 (near northeast corner). North of figure 1 in Montana the Powder River joins the northeast oriented Yellowstone River. The Nowood River-Powder River drainage divide area investigated in this essay is located along the west side of the Bighorn Mountains and extends southward from Powder River Pass to near the Middle Fork Powder River headwaters.

Today the Powder River and Bighorn River are north oriented drainage systems and the Powder River headwaters are located at elevations much higher than the Nowood River valley elevation to the west. Yet, the topographic map evidence illustrated in this essay suggests multiple south and southeast oriented flood flow channels once moved floodwaters from the present day north oriented Nowood River drainage basin to the Powder River drainage basin. If correctly interpreted these former flood flow channels were formed at a time when the Bighorn Mountains, the Bighorn Basin, and the Powder River Basin had not emerged as the distinct topographic features they are today and when floodwaters could freely flow across what is today a high mountain range. The floodwaters are interpreted to have been derived from the western margin of a deep North American ice sheet and were flowing from western Canada in south and southeast directions to and across present day Wyoming. The Bighorn Mountains and adjacent basins emerged as floodwaters flowed across them and their emergence was probably caused by ice sheet related crustal warping and by the removal of great thicknesses of bedrock as floodwaters crossed the rising mountain ranges and deposited the debris in adjacent basins. Ice sheet related crustal warping combined by deep glacial erosion (underneath the ice sheet) created a deep “hole” in which the ice sheet was located. The region in figure 1 could be considered to be segment of the deeply eroded and warped deep “hole” southwest rim. As ice sheet melting progressed space in the south end of the deep “hole” was opened up by ice sheet melting and at least initially drained in a south direction on flood flow channels east of figure 1. The deep northeast oriented Yellowstone River valley then began to erode headward from this newly opened up space in the deep “hole” to capture south and southeast oriented melt water flood flow moving across Montana and into Wyoming. Headward erosion of the deep northeast oriented Yellowstone River valley beheaded the south and southeast oriented flood flow routes in sequence from east to west. Floodwaters on north ends of beheaded flood flow routes reversed flow direction to create north oriented drainage routes. These newly formed north oriented drainage routes then captured south and southeast oriented flood flow from west of the actively eroding Yellowstone River valley head. South oriented flood flow in the Powder River Basin was beheaded and reversed first. The reversed flood flow in the Powder River then captured southeast oriented flood flow moving from the Bighorn Basin across what are now the high Bighorn Mountains. Evidence for such captures is seen in the southeast oriented North Fork Powder River route shown in figure 1 and is illustrated in many other south oriented Powder River tributaries seen in the more detailed maps illustrated in this essay. In time headward erosion of the deep Yellowstone River valley beheaded and reversed flood flow in the Bighorn Basin and flood flow across the Bighorn Mountains ended. At the same time the Bighorn Mountains and Bighorn Basin were emerging as the distinct topographic features they are today. Anyone who has seen the Bighorn Mountains, especially the western slope, knows the above described flood flow movements would be impossible today.

Detailed location map for Nowood River-Powder River drainage divide area

Figure 2: Detailed location map Nowood River-Powder 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 Nowood River-Powder River drainage divide area in the Wyoming Bighorn Mountains. The green colored area straddling the north center edge of figure 2 is National Forest land located in the Bighorn Mountains.  The Bighorn Mountains extend in a north to south direction from the north center edge of figure 2. The Bridger Mountains are located near the southwest corner of figure 2. Lyesite Mountain is a labeled mountain between the Bridger Mountains and the Bighorn Mountains near the south edge of figure 2. The Bighorn Basin is located west of the Bighorn Mountains and north of the Bridger Mountains and the Bighorn River flows in a northeast and north-northwest direction from the west edge of figure 2 (slightly north of center) to the north edge of figure 2 (near northwest corner). The Nowood River originates on the northeast side of Lyesite Mountain and flows in a northeast and north direction to the small town of Bigtrails and then to the town of Tensleep. From Tensleep the Nowood River turns to flow in a northwest direction to join the Bighorn River near Manderson (near north edge of figure 2). Tensleep Creek is southwest oriented tributary joining the Nowood River near Tensleep and Leigh Creek and Canyon Creek are southwest and west oriented Tensleep Creek tributaries. South of Tensleep Creek is west-southwest and west-northwest oriented Spring Creek and then northwest oriented Otter Creek with its west oriented North Fork. Still further south can be found north-northwest oriented Little Canyon Creek and north oriented Box Elder, Cherry, and Deep Creek as Nowood River tributaries. East of the Bighorn Mountains is the Powder River Basin and the Powder River is formed near Kaycee at the confluence of the southeast oriented North Fork and east-northeast oriented Middle Fork and the north-northeast oriented South Fork joining the east oriented Powder River east of Kaycee. The Powder River flows to near Sussex (near east edge of figure 2-south half) and then turns to flow in a north direction to the north edge of figure 2 (near northeast corner). The North Fork Powder River originates near the Canyon Creek headwaters in the green colored area just south of the highway and flows in a southeast direction to join the Middle Fork near Kaycee. Pass Creek is a southeast oriented tributary of interest in this essay. Labeled Middle Fork Powder River tributaries of interest in this essay include the north-northeast, northeast, east-southeast, and southeast oriented South Fork Red Fork Powder River and its south-southeast oriented Beartrap Creek tributary and northeast and southeast oriented Beaver Creek and its east- northeast oriented Blue Creek tributary. Note the large number of south oriented drainage routes in the Bighorn Mountains region in what are today north oriented drainage systems on either side of the Bighorn Mountains. The south oriented drainage routes in the Bighorn Mountains are relics of south oriented flood flow channels that once crossed region. At the time the south oriented flood flow crossed the Bighorn Mountains region the Bighorn Mountains and adjacent Bighorn and Powder River Basins were just beginning to emerge. As the Bighorn and Powder River Basins on either side of the emerging Bighorn Mountains developed the south oriented flood flow channels in the Bighorn Mountains regions were systematically captured by south oriented flood flow channels in the adjacent basin areas. Headward erosion of the much deeper northeast oriented Yellowstone River valley from space in the deep “hole” being opened up by ice sheet melting next beheaded the south oriented flood flow channels in the Powder River Basin. Floodwaters on the north ends of the beheaded flood flow channels reversed flow direction to create the north oriented Powder River drainage route, which captured the southeast oriented flood flow still flowing across the emerging Bighorn Mountains. Next Yellowstone River valley headward erosion beheaded south oriented flood flow on the Bighorn River-Nowood River alignment and floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented Bighorn River and Nowood River drainage routes, which captured the southwest oriented flood flow channels (which were no longer being eroded by floodwaters) that had formerly supplied floodwaters to south oriented flood flow channels in the Bighorn Basin. North and northwest oriented Nowood River tributary drainage routes were created by reversals of flood flow on north ends of south and southeast oriented flood flow routes beheaded by headward erosion of the deep north and northeast oriented Nowood River valley.

Canyon Creek-North Fork Powder River drainage divide area near Powder River Pass

Figure 3: Canyon Creek-North Fork Powder River drainage divide area near Powder River Pass. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of the Canyon Creek-North Fork Powder River drainage divide area near Powder River Pass. Tensleep Creek flows in a south and southwest direction from the north edge of figure 3 (west of Meadowlark Lake) to the west edge of figure 3 (south half) and west of figure 3 flows in a southwest direction to join the north and northwest oriented Nowood River as a barbed tributary. Leigh Creek flows in a south-southwest, west-southwest, and west direction from near the north edge of figure 3 (slightly east of center) to join southwest oriented Tensleep Creek near the west edge of figure 3. Powder River Pass near the northeast corner of figure 3 is where the highway crosses the Nowood River-Powder River drainage divide. Canyon Creek originates on the east side of Powder River Pass and flows in a west-southwest, south-southwest, and south direction to the south center edge of figure 3. South of figure 3 Canyon Creek turns to flow in a west and northwest direction to join southwest oriented Tensleep Creek as a barbed tributary. The North Fork Powder River originates a short distance south of Powder River Pass and flows in a south-southwest and south direction to the south edge of figure 3 (east half) and south of figure 3 turns to flow in a southeast direction to eventually join other Powder River Forks to form the north oriented Powder River. The southeast oriented stream just barely seen in the northeast corner of figure 3 is the North Fork Crazy Woman Creek. East of the figure 3 the North Fork Crazy Woman Creek flows in a southeast, northeast, and southeast direction to Bighorn Mountains east flank where it joins the southeast and northeast oriented South Fork Crazy Woman Creek to form northeast oriented Crazy Woman Creek, which is a Powder River tributary. Note in figure 3 how the North Fork Powder River, Canyon Creek, Leigh Creek, and Tensleep Creek all originate on the high Bighorn Mountains upland surface and flow parallel to each other for a considerable distance before the North Fork Powder River turns to flow in a southeast direction to the Bighorn Mountains east side while the other streams turn to flow in southwest directions to the Bighorn Mountains west side. The parallel stream valleys on the Bighorn Mountains upland surface originated as south oriented flood flow channels, which were first captured by headward erosion of much deeper south oriented flood flow channels on either side of the emerging Bighorn Mountains. At that time there was no deep Yellowstone River valley to the north and elevations north of figure 3 were as high as the Bighorn Mountains upland surface elevation, although the Bighorn Mountains have probably been uplifted significantly since that time. Through valleys crossing drainage divides provide evidence of diverging and converging flood flow channels and of flood flow channels beheaded by headward erosion of deeper flood flow channels. For some examples of the through valleys see the Powder River Pass area (seen in more detail in figure 4) and the drainage divides south of Meadowlark Lark Lake.

Detailed map of Canyon Creek-North Fork Powder River drainage divide area

Figure 4: Detailed map of Canyon Cree-North Fork Powder River 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 Canyon Creek-North Fork Powder River drainage divide seen in less detail in figure 3. Powder River Pass is located in the north half of section 9 in the northeast quadrant of figure 4. Canyon Creek originates in section 4 north of Powder River Pass and flows in a southwest and south-southwest direction to the south edge of figure 4 (near southwest corner) and south and west of figure 4 water eventually reaches the north and northwest oriented Nowood River in the Bighorn Basin. The North Fork Powder River originates in section 10 (east of Powder River Pass) and flows in south-southwest and south direction to the south center edge of figure 4 and south and east of figure 4 water eventually reaches the north oriented Powder River in the Powder River Basin. The south-southwest oriented stream originating in section 8 and flowing to the south edge of figure 4 (between the North Fork Powder River and Canyon Creek) is Webb Creek, which south of figure 4 joins the North Fork Powder River. Powder River Pass is an example of a through valley crossing a drainage divide and many other examples can be seen in figure 4 and other figures illustrating this essay. The map contour interval for figure 4 is 40 feet and the Powder River Pass elevation is 9677 feet. The drainage divide south of Powder River Pass rises to at least 9800 feet and to the north of Powder River Pass it rises to at least 10,215 feet indicating that Powder River Pass is at least 123 feet deep. While almost insignificant compared to the Bighorn Mountains elevation above the adjacent basin and even to other through valleys in the region the Powder River Pass through valley is evidence of a former southeast oriented flood flow channel that was captured by headward erosion of the deeper southwest oriented Canyon Creek valley. Note how in the north half of section 19 a south and south-southeast oriented Webb Creek tributary valley is linked by a shallow through valley with the adjacent Canyon Creek valley. This evidence suggests the Webb Creek and Canyon Creek valleys were at one time converging and diverging flood flow channels until headward erosion of the deeper Canyon Creek valley captured all of the south and southeast oriented flood flow to the Webb Creek flood flow channel.

North Fork Powder River-Billy Creek drainage divide area

Figure 5: North Fork Powder River-Billy Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 provides a topographic map to illustrate the North Fork Powder River-Billy Creek drainage divide area south and somewhat east of figure 3 and includes a significant overlap area with figure 3. The North Fork Powder River flows in a south and southeast direction from the north center edge of figure 5 to the east edge of figure 5 (near southeast corner). Webb Creek flows in a southwest and southeast direction to join the North Fork Powder River near the north center edge of figure 4. Otherwise the only other North Fork Powder River tributaries of significance in figure 5 are southeast and northeast oriented Johnson Creek in the southeast quadrant of figure 5 and north and southeast oriented Pass Creek (south of Johnson Creek). Pass Creek joins the North Fork Powder River south and east of figure 5. Note how a through valley links the southeast oriented Johnson Creek with the North Fork Powder River valley near Dullknife Reservoir. The map contour interval for figure 5 is 20 meters and the through valley elevation is between 2500 and 2520 meters. Elevations rise to more than 2560 meters on either side suggesting the through valley is at least 40 meters deep. The through valley provides evidence of diverging and converging flood flow channels prior to headward erosion of the deeper North Fork Powder River valley, which beheaded the flood flow channel to the Johnson Creek valley. Canyon Creek flows in a south-southwest, south, and west direction from the north edge of figure 5 (west of center) to the west center edge of figure 5. Note southwest oriented Canyon Creek tributaries including Onion Gulch and Bear Gulch. Also note north, west-southwest, and northwest oriented Billy Creek, which originates just north of the north oriented Pass Creek headwaters and which joins the west oriented Canyon Creek segment. Well-defined north-to-south and northwest-to-southeast oriented through valleys link the north oriented Billy Creek valley segment with the north and southeast oriented Pass Creek valley. Through valleys in the Billy Creek-Pass Creek region were originated as converging and diverging flood flow channels and were first captured by headward erosion of the deeper southeast oriented Pass Creek valley, which beheaded a south oriented flood flow channel on the present day north oriented Billy Creek alignment. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented Pass Creek headwaters. Next headward erosion of west-southwest oriented Billy 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 Billy Creek headwaters drainage route. South oriented flood flow to the south oriented flood flow channel was next beheaded by headward erosion of the deeper southeast oriented North Fork Powder River valley, which ended flood flow to the Billy Creek valley (at least on the Bighorn Mountains upland surface). As seen in figure 3 and 4 headward erosion of the Canyon Creek valley then captured flood flow moving to the North Fork Powder River valley and ended flood flow to the North Fork Powder River.

Detailed map of Billy Creek-Pass Creek drainage divide area

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

Figure 6 illustrates a detailed topographic map of the Billy Creek-Pass Creek drainage divide area seen in less detail in figure 5. Pass Creek originates in section 17 (near southwest corner of figure 6) and flows in a north-northeast direction into the southeast corner of section 8 where it turns to flow in a southeast, east-northeast, southeast, and east direction to the southeast corner of figure 6. Note the southeast oriented Pass Creek tributary in section 10. South and east of figure 6 Pass Creek joins the southeast oriented North Fork Powder River with water eventually reaching the north oriented Powder River in the Powder River Basin. Billy Creek flows from the northwest corner of section 9 in a north-northeast and north direction to near the north edge of figure 6 where it turns to flow in a west and west-southwest direction to the west edge of figure 6 (near northwest corner). West of figure 10 Pass Creek eventually joins Canyon Creek with water eventually reaching the north and northwest oriented Nowood River in the Bighorn Basin. In the east half of section 8 a through valley links the north-northeast oriented Pass Creek headwaters valley with the north-northeast oriented Billy Creek headwaters valley. The map contour interval for figure 6 is 40 feet and the through valley floor elevation is shown as 8160 feet. Elevations east of the through valley in section 9 rise to 8326 and west of the through valley near the center of section 8 reach 8392 feet suggesting the through valley is at least 166 feet deep. Another through valley seen in the southeast corner of section 4 and northeast corner of section 9 links the north oriented Billy Creek valley with the southeast oriented Pass Creek valley. This second through valley has an elevation of between 8040 and 8080 feet. Elevations in the north half of section 3 are more than 8400 feet and in section 17 exceed 8400 feet suggesting the through valley may be as much as 320 feet deep. Other northwest-to-southwest through valleys link the north oriented Billy Creek headwaters valley with west oriented and west-southwest oriented valleys draining to the west edge of figure 6. Another through valley of interest is in section 17 and links the north-northeast oriented Pass Creek headwaters valley with a west oriented Spring Creek tributary valley with Spring Creek flowing in a southwest and northwest direction to eventually reach the north and northwest oriented Nowood River valley. These through valleys provide evidence of a southeast oriented anastomosing channel complex that once crossed the region seen in figure 6 with floodwaters coming from what is today the deep Bighorn Basin west of the Bighorn Mountains, although at that time the Bighorn Mountains and Bighorn Basin had not emerged as distinctive topographic features. Floodwaters were flowing to south oriented flood flow channels, which were eroding headward in the Powder River Basin east of the present day Bighorn Mountains (and east of figure 6 the Bighorn Mountains and Powder River Basin were beginning to emerge as distinction features). Headward erosion of deeper west-southwest oriented valleys from much south oriented flood flow channels in the Bighorn Basin area then began to capture the southeast oriented flood flow channels that had been supplying floodwaters to the emerging Powder River Basin and a south-southwest oriented flood flow channel eroded headward on the north-northeast oriented Pass Creek-Billy Creek alignment to capture southeast oriented flood flow from north of the actively eroding and deep south oriented flood flow valley heads. Headward erosion of the deeper southeast oriented Pass Creek valley then beheaded and reversed the south-southwest oriented flood flow to create the north-northeast oriented Pass Creek headwaters valley. Soon thereafter headward erosion of the deeper west-southwest oriented Billy Creek beheaded and reversed the flood flow to the newly eroded Pass Valley and created the north-northeast oriented Billy Creek drainage route. In this manner the south oriented flood flow channels in the Powder River Basin to the east and in the Bighorn Basin to the west competed with each other for the south and southeast flood flow moving across what are today the high Bighorn Mountains. As the south oriented flood flow channels competed with each to capture the flood flow they also were creating the present day Nowood River-North Fork Powder River drainage divide and beginning the process of developing the Bighorn Basin, Bighorn Mountains, and Powder River Basin into the distinctive topographic features they are today.

Spring Creek-Beartrap Creek drainage divide area

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

Figure 7 provides a topographic map of the Spring Creek-Beartrap Creek drainage divide area south and west of figure 5 and includes an overlap area with figure 5. The Billy Creek-Pass Creek drainage divide area seen in figure 6 is located near the northeast corner of figure 7. Spring Creek originates west of the Billy Creek headwaters and flows in a south-southwest, and west direction to southwest oriented Spring Creek Canyon and then turns to flow in a northwest and west direction to the west edge of figure 7 (north of center). West of figure 7 Spring Creek flows in a northwest direction to join the north and northwest oriented Nowood River. South of Spring Creek is the southwest, south-southwest, and west oriented North Fork Otter Creek, which joins northeast oriented South Fork Otter Creek near the southwest corner of figure 7 to form northwest oriented Otter Creek, which joins the Nowood River west of figure 7. Spring Creek Canyon and the North Fork Otter Creek Canyon are eroding into the surface of what appears to a steeply dipping layer of resistant sedimentary strata. North-to-south oriented through valleys link the Spring Creek and Otter Creek valleys at the base of steep west-facing slope and also near the top where the Spring Creek valley is relatively close to the North Fork Otter Creek valley. These through valleys follow the strike of the strata, although they are also water-eroded valleys and provide evidence of flood flow channels that once crossed the region, which today are at very different elevations. Beartrap Creek originates just east of the North Fork Otter Creek headwaters and flows in a southeast, south, and south-southeast direction to the east edge of figure 7 (near southeast corner) and south and east of figure 7 joins the Red Fork Powder River, which then flows to the Middle Fork Powder River. Note how the Beartrap Creek headwaters valley is linked by a through valley with the west oriented North Fork Otter Creek headwaters valley and also with the north oriented Pass Creek valley.  The map contour interval for figure 7 is 20 meters and the Beartrap Creek-North Fork Otter Creek through valley floor elevation is shown as 2474 meters. Elevations to the south rise to more 2620 meters and elevations to north rise to more than 2580 meters suggesting the through valley is at least 100 meters deep. The through valley is a water eroded valley and was eroded by southeast and east oriented water moving to the actively eroding Beartrap Creek valley. At that time there was no steep slope on the west side of the Bighorn Mountains (elevations at the base of the slope are today approximately 1000 meters lower than the through valley floor elevation). The west side of the Bighorn Mountains emerged as floodwaters eroded the Bighorn Basin and as ice sheet related crustal warping raised the Bighorn Mountains. The crustal warping may have been aided by deep erosion of the Bighorn Mountains crest area as the Bighorn Mountains were being uplifted.

North Fork Little Canyon Creek-South Fork Red Fork Powder River drainage divide area

Figure 8: North Fork Little Canyon Creek-South Fork Red Fork Powder River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 provides a topographic map of the North Fork Little Canyon Creek-South Fork Red Fork Powder River drainage divide area south and slightly east of figure 7 and includes a thin strip of overlap area with figure 7. Beartrap Creek flows in a south and south-southeast direction from the north edge of figure 8 (near northeast corner) to the west center edge of figure 8. The south-southeast and southeast oriented stream west of Beartrap Creek is the North Fork Red Fork Powder River and the east-northeast and northeast oriented stream flowing from the south center edge of figure 8 and which turns to flow in a southeast direction just before joining the North Fork Red Fork Powder is the South Fork Red Fork Powder River. East and south of figure 8 the Red Fork Powder River flows in a southeast and south-southeast direction to join the Middle Fork Powder River. Otter Creek Vee is located between northwest oriented Dry Fork (north) and South Fork Otter Creek with Crooked Creek being a northwest oriented South Fork Otter Creek tributary. The south-southwest, west-northwest, and southwest oriented stream in the southwest quadrant of figure 8 is the North Fork of northwest oriented Little Canyon Creek, which flows across the southwest corner of figure 8 and which joins the Nowood River west of figure 8. The Bighorn Mountains crest extends in a roughly north-to-south direction across the center of figure 8 and is crossed by several through valleys linking the Nowood River tributary valleys with the Powder River tributary valleys. Perhaps the most impressive of these through valleys is found near the south edge of figure 8 and links a south oriented South Fork Red Fork Powder River tributary valley with the south-southwest oriented North Fork Little Canyon Creek valley.  A road is located in the through valley. The map contour interval for figure 8 is 20 meters and through valley floor elevation is between 2260 and 2280 meters. Elevations south of the through valley rise to more than 2400 meters and elevations the north rise even higher suggesting the through valley is at least 120 meters deep. The through valley was eroded by southeast oriented flood flow probably moving on the present day northwest oriented Crooked Creek-South Fork Otter Creek alignment to what was then the actively eroding South Fork Red Fork Powder River valley, which was eroded headward from the southeast and southeast oriented Red Fork Powder River valley to capture south and southeast oriented flood flow on the west side of what were then the emerging Bighorn Mountains. The southeast oriented flood flow across the Bighorn Mountains crest ridge was probably beheaded and reversed when headward erosion of deeper south oriented flood flow channels in the Bighorn Basin captured the flood flow. The south-southwest oriented North Fork Little Canyon Creek valley segment is on the alignment of one of these south oriented flood flow channels. These western south oriented flood flow channels were then beheaded and reversed to create the north and northwest oriented Nowood River and its northwest oriented tributaries seen in figure 8. Crustal warping that was raising the Bighorn Mountains probably greatly aided the flood flow reversals, which produced the northwest oriented Nowood River tributary drainage routes on alignments of what had been southeast oriented flood flow channels.

Little Canyon Creek-South Fork Red Fork Powder River drainage divide area

Figure 9: Little Canyon Creek-South Fork Red Fork Powder River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 provides a detailed topographic map of the Little Canyon Creek-South Fork Red Fork Powder River drainage divide area seen south and west of figure 8 and includes an overlap area with figure 8. The North Fork Little Canyon Creek originates near the north center edge of figure 9 and flows in a south-southwest and west-northwest direction to join the northwest oriented Middle Fork and then to flow in a northwest direction to the north edge of figure 9 (near northwest corner). The South Fork Little Canyon Creek originates in the south center area of figure 9 and flows in a south-southwest, west, north, west, and north direction to join Little Canyon Creek in the northwest quadrant of figure 9. Redbank Creek flows in a southwest direction in the west center region of figure 9 to the west edge of figure 9 (south of center) and joins the north oriented Nowood River just west of figure 9. Note how a through valley links the Redbank Creek valley with the South Fork Little Canyon Creek valley. The map contour interval for figure 9 is 20 meters and the through valley floor elevation is between 1600 and 1620 meters. Elevations of more 1700 meters can be found on either side of the through valley suggesting the through valley is at least 100 meters deep. The through valley provides evidence of diverging and converging flood flow channels that once crossed the region. The South Fork Red Fork Powder River flows in a northeast direction to the east edge of figure 9 (near northeast corner) and has interesting headwaters just east of the center of figure 9. One headwaters stream is oriented in a northwest direction and drains the northwest end of a northwest-to-southeast oriented through valley drained in the opposite direction by southeast oriented Bayer Creek, which flows to northeast oriented Beaver Creek (which eventually flows to the Middle Fork Powder River). The through valley floor elevation is between 2260 and 2280 meters and elevations on either side rise to more than 2480 meters suggesting the through valley is more than 200 meters deep. Another South Fork Red Fork Powder River headwaters stream is northeast and north oriented Spring Branch, which is linked by a through valley with a southeast oriented Beaver Creek tributary valley and also with the south-southwest oriented South Fork Little Canyon Creek headwaters valley. As seen here in figure 9 Middle Fork Powder River headwaters are located west of the high Bighorn Mountains crest ridge and are again linked by through valleys with the west oriented Nowood River tributary valleys. This evidence suggests considerable Bighorn Mountains uplift has occurred since floodwaters crossed the region.

Deep Creek-Middle Fork Powder River drainage divide area

Figure 10: Deep Creek-Middle Fork Powder River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 provides a topographic map of the Deep Creek-Middle Fork Powder River drainage divide area south and slightly west of figure 9 and there is no overlap area with figure 9 although the gap between figures is small. The Middle Fork Powder River originates in the south center area of figure 10 and flows in an east, north, north-northeast, east, northeast, and east-northeast direction to the east edge of figure 10 (near northeast corner). Rock Creek is an east and southeast oriented Middle Fork Powder River tributary in the northeast quadrant of figure 10. Deep Creek flows from the south edge of figure 10 (west half) in a north, northwest, north, and northwest direction to the west edge of figure 10 (near northwest corner) and north and west of figure 10 joins the Nowood River. Lost Creek is an east, north, and northwest oriented Deep Creek tributary located north and west of Deep Creek. Little Lost Creek is an east and south oriented Deep Creek tributary located south of Lost Creek. Note how through valleys link east oriented Lost Creek and Little Lost Creek headwaters valleys with the north oriented Middle Fork Powder River headwaters valley. The map contour interval for figure 10 is 20 meters and the Lost Creek-Middle Fork Powder River through valley floor elevation is between 2540 and 2560 meters. Elevations to the north rise to at least 2680 meters and elevations to south rise to more than 2700 meters suggesting the through valley is at least 120 meters deep. In addition note how the Middle Fork Powder River headwaters are located west of the Bighorn Mountains crest ridge and have eroded a deep water gap across the Bighorn Mountains crest ridge near the northeast corner of figure 10. While not completely seen in figure 10 the water gap is more than 400 meters deep just east of figure 10. Southeast oriented tributaries in the northeast quadrant of figure 10 and a broad northwest-to-southeast oriented through valley bounded on the southwest by Cherry Creek Hill provide evidence the Middle Fork Powder River valley eroded headward to capture massive southeast oriented flood flow. The flood flow was beheaded by headward erosion of a deeper south oriented flood flow channel on the present day north oriented Deep Creek alignment. Crustal warping that was raising the Bighorn Mountains at the same time probably helped in the headward erosion of the Deep Creek valley, which became a diverging flood flow channel from a south oriented flood flow channel on the present day Nowood River alignment. Subsequently the south oriented flood flow was beheaded and reversed by headward erosion of the much deeper Yellowstone River valley in Montana to create the north oriented Nowood River and Deep Creek drainage routes. Continued ice sheet related crustal warping probably raised the Bighorn Mountains significantly since the flood flow ended.

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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