Shell Creek-Nowood River drainage divide area landform origins in the Wyoming Bighorn Mountains and Bighorn Basin, USA

Authors

 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the region between Shell Creek and the Nowood River in the Wyoming Bighorn Mountains and Bighorn Basin. Shell Creek is a northwest and west-southwest oriented stream originating on the crest of the high Bighorn Mountains and joining the north oriented Bighorn River in the Bighorn Basin. The Nowood River is a north oriented stream flowing along the Bighorn Basin east margin before turning to flow in a northwest and west direction into the Bighorn Basin to join the Bighorn River. Paint Rock Creek is a southwest oriented Nowood River tributary originating in the high Bighorn Mountains near the Shell Creek headwaters. Through valleys and barbed tributaries illustrated and discussed in this essay and found at all study region elevations (from near the Bighorn River in the Bighorn Basin to the Bighorn Mountains crest ridge) are interpreted in the context of immense south and southeast oriented melt water floods and provide evidence of southeast and south oriented flood flow channels that once linked the Shell Creek valley with south oriented Nowood River tributary valleys. 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. At least initially the Bighorn Mountains and Bighorn Basin were not distinct topographic features and floodwaters could freely across what is today a major mountain range. The Bighorn Mountains and Bighorn Basin emerged as ice sheet related crustal warping created a deep “hole” in which the ice sheet was located. The Bighorn Mountains and Bighorn Basin could be considered to be located on a segment of the deep “hole’s” deeply eroded and warped southwest rim.  The north oriented Bighorn River drainage system is interpreted to have formed when headward erosion of the deep northeast oriented Yellowstone River valley in Montana beheaded south and southeast oriented flood flow channels crossing the present day Bighorn Mountains and Bighorn Basin region. The Yellowstone River eroded headward from space in the deep “hole” being opened up by ice sheet melting to capture south and southeast oriented flood flow in Montana and to divert the floodwaters into the deep “hole”. Floodwaters on north and northwest ends of beheaded flood flow channels reversed flow direction to create north oriented drainage routes, which then captured south and southeast oriented flood flow from west of the actively eroding Yellowstone River valley head. This interpretation requires Bighorn Mountains uplift to have occurred as floodwaters flowed across the region and probably also requires significant uplift after flood flow ended.

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

Shell Creek-Nowood River drainage divide area location map

Figure 1: Shell Creek-Nowood 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 Shell Creek-Nowood River drainage divide area in the Wyoming Bighorn Mountains and Basin and illustrates a region in north central Wyoming. The Montana-Wyoming state line is located along the north edge of figure 1. The Bighorn Mountains extend in a north-to-south direction just east of the figure 1 center from the north edge to the south edge. The Owl Creek Mountains can be seen in the southwest quadrant of figure 1 and north of the Owl Creek Mountains the Absaroka Range is located along the west edge of figure 1. The Bighorn Basin is located west of the Bighorn Mountains, north of the Owl Creek Mountains, and east of the Absaroka Range. The western margin of the Powder River Basin can be seen along the east edge of figure 1 and is east of the Bighorn Mountains. The Wind River flows in a southeast direction across the southeast corner of figure 1 and south of figure 1 turns to flow in a north direction to Boysen Reservoir and Thermopolis. Between Boysen Reservoir and Thermopolis the Wind River flows through Wind River Canyon, which is a deep canyon eroded across the Owl Creek Mountains. Once in the Bighorn Basin the Wind River name changes to become the Bighorn River, which flows from Thermopolis to Manderson, Greybull, and the north edge of figure 1 (west of center). North of figure 1 the Bighorn River flows in a north-northeast direction to join the northeast oriented Yellowstone River. The Nowood River originates near the south center edge of figure 1 and flows in a north-northeast and north-northwest direction along the Bighorn Mountains western flank before turning to flow in a northwest direction into the Bighorn Basin where it joins the Bighorn River near Manderson. Tensleep Creek is the unlabeled southwest oriented tributary joining the Nowood River near the town of Tensleep. Paint Rock Creek is the unlabeled southwest oriented Nowood River tributary flowing through the town of Hyattville. The unlabeled northwest and west-southwest oriented stream north of Medicine Lodge Creek and flowing near the town of Shell to join the Bighorn River near Greybull is Shell Creek. The Shell Creek-Nowood River drainage divide area investigated in this essay is located south of Shell Creek and north of Paint Rock Creek and the Nowood River west of the Paint Rock Creek. This essay begins at the Shell Creek and Paint Rock Creek headwaters in the high Bighorn Mountains and progresses westward along the drainage divide to the Bighorn River north of Manderson.

Today drainage routes in the region shown by figure 1 are oriented in a north direction with drainage flowing to the northeast oriented Yellowstone River in Montana. However, these north oriented drainage routes evolved during the reversal of massive reversal of south and southeast oriented floods, which flowed across the region as the Bighorn Mountains, Owl Creek Mountains, Absaroka Range, and other regional mountain ranges were emerging. Floodwaters were derived from the western margin of a thick North American ice sheet and were flowing from western Canada to and across the region seen in figure 1. At least initially the Bighorn Basin, Bighorn Mountains, Owl Creek Mountains, and Absaroka Range had not emerged as distinctive topographic features and floodwaters could freely flow across what are today high mountain ranges. The Bighorn Basin and surrounding mountain ranges emerged as ice sheet related crustal warping and deep erosion created a deep “hole” in which the ice sheet was located. The region seen in figure 1 could be considered to be a segment of the deep “hole’s” deeply eroded and warped southwest rim. The massive reversal of south and southeast oriented flood flow occurred as the Bighorn Mountains and Bighorn Basin were emerging and was triggered by headward erosion of the deep northeast oriented Yellowstone River valley across Montana. The deep northeast oriented Yellowstone River valley eroded headward from space at the south end of the deep “hole” that was being opened up by ice sheet melting and which (at least initially) drained in a south direction using flood flow channels east of figure 1. Headward erosion of the deep Yellowstone River valley captured the south and southeast oriented flood flow moving across Montana and diverted the floodwaters in a northeast direction to the deep “hole.” Flood flow routes to Wyoming were beheaded in sequence from east to west. Floodwaters on north ends of the beheaded flood flow channels 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. Flood flow in the Powder River Basin was beheaded and reversed while southeast oriented flood flow was still crossing the present day Bighorn Mountains and the southeast oriented North Fork Powder River (in southeast quadrant of figure 1) is evidence that reversed flood flow on the present day north oriented Powder River drainage route (east of figure 1) captured southeast oriented flood flow from west of the actively eroding Yellowstone River valley head. Continued headward erosion of the deep northeast oriented Yellowstone River valley subsequently beheaded and reversed south oriented flood flow crossing the Bighorn Mountains area and in the present day Bighorn Basin region to create the north oriented Bighorn River and its north oriented tributary drainage routes. The newly created north oriented Bighorn River drainage route then captured southeast oriented flood flow from west of the actively eroding Yellowstone River valley head (e.g. see southeast oriented Wind River in the southwest corner of figure 1).

Detailed location map for Shell Creek-Nowood River drainage divide area

Figure 2: Detailed location map Shell Creek-Nowood 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 Shell Creek-Nowood River- drainage divide area in the Wyoming Bighorn Mountains and Bighorn Basin. The green colored area is National Forest land located in the Bighorn Mountains. The Bighorn Basin is located west of the Bighorn Mountains. The Bighorn River flows in a north direction from the town of Worland near the south edge of figure 2 to the towns of Manderson, Basin, and Greybull before reaching the north edge of figure 2 near the town of Spence. The Nowood River flows in a northwest direction from the south edge of figure 2 (near the town of Tensleep) to join the Bighorn River near the town of Manderson. Note southwest oriented streams flowing from the Bighorn Mountains to join the northwest oriented Nowood River as barbed tributaries. These southwest oriented drainage routes are relics of south oriented flood flow channels that once crossed the region. Tensleep Creek is a southwest oriented tributary originating in the high Bighorn Mountains and joins the Nowood River near the town of Tensleep. Paint Rock Creek is located north and west of Tensleep Creek and originates in the Bighorn Mountains and flows through the town of Hyattsville to join the northwest oriented Nowood River. Paint Rock Creek tributaries include southwest and south oriented Medicine Lodge Creek and south-southwest oriented Dry Medicine Lodge Creek, which join Paint Rock Creek near Hyattsville. Alkali Creek joins Paint Rock Creek west of Hyattsville. West of Alkali Creek south oriented McDermotts Gulch drains to the northwest oriented Nowood River and west of McDermotts Gulch south-southeast oriented Wild Horse Draw drains to the Nowood River as a barbed tributary. Shell Creek originates in the Bighorn Mountains almost at the same point where Medicine Lodge Creek originates and then flows in a northwest and west-southwest direction to the town of Shell and then joins the north oriented Bighorn River near the town of Greybull. Labeled Shell Creek tributaries of interest in this essay include southwest and northwest oriented Trapper Creek and northwest oriented Red Gulch and Sheldon Gulch. The northwest oriented tributaries were formed by reversals of flood flow on northwest ends of beheaded flood flow channels. Note south oriented Shell Creek tributaries and southeast oriented Bighorn River tributaries. The abundance of south oriented barbed tributaries are evidence that a massive flood flow reversal took place as the north oriented Bighorn River drainage system was created.

Shell Creek-Medicine Lodge Creek drainage divide area

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

Figure 3 provides a topographic map of the Shell Creek-Medicine Lodge Creek drainage divide area. Emerald Lake is located slightly north of the center of figure 3. Shell Creek originates at Emerald Lake and flows in a northwest direction to Shell Lake and Shell Reservoir before reaching the north edge of figure 3 (west half). Medicine Lodge Creek originates a short south and west of Emerald Lake and flows in a southwest direction to near the southwest corner of figure 3. A “Pack Trail” crosses from Emerald Lake to the southwest oriented Medicine Lodge Creek valley and makes use of a pass or through valley linking the northwest oriented Shell Creek valley with the southwest oriented Medicine Lodge Creek valley. The map contour interval for figure 3 is 20 meters and the pass elevation is between 3180 and 3200 meters. Elevations west of the pass rise to more than 3320 meters and elevations east of the pass rise to more than 3500 meters suggesting the pass is at least 120 meters deep. North and east of Emerald Lake is Edelman Pass, which links the Shell Creek and Medicine Lodge Creek valleys with the north-northeast oriented Edelman Creek valley. Water in Edelman Creek eventually reaches the Tongue River, which is a north oriented Yellowstone River tributary on the east side of the Bighorn Mountains. The Edelman Pass elevation is between 3120 and 3140 meters with elevations to the north rising to 3386 meters, which suggest Edelman Pass is approximately 240 meters deep. Other passes can be seen linking the Shell Creek and Medicine Lodge Creek valleys. For example Dutch Oven Pass has an elevation of between 3200 and 3220 meters and is at least 100 meters deep. Another example is Geneva Pass (east and south from Emerald Lake), which links the north oriented East Fork Big Goose Creek valley with a south oriented tributary valley draining to the southwest oriented Paint Rock Creek valley. Medicine Lodge Creek is a Paint Rock Creek tributary and Big Goose Creek is a Tongue River tributary. These passes are water-eroded features, yet today they cross high drainage divides in a high mountain range. The passes were eroded by south oriented flood flow moving to what at that time were actively eroding southwest oriented Medicine Lodge Creek and Paint Rock Creek valleys. The northwest oriented Shell Creek valley probably originated as a southeast oriented flood flow channel. At the time the passes were eroded the Bighorn Mountains did not stand high above the surrounding Bighorn and Powder River Basins as they do today. The mountains were uplifted as floodwaters flowed across them and as floodwaters eroded the deep basins on either side. As previously mentioned flood flow east of the emerging Bighorn Mountains was beheaded and reversed before flood flow in the Bighorn Mountains was beheaded and reversed. Southeast oriented flood flow on the Shell Creek alignment probably was captured by reversed flood flow on the Edelman Creek alignment, although was subsequently beheaded and reversed to create the northwest oriented Shell Creek drainage route.

Detailed map of Shell Creek-Medicine Lodge Creek drainage divide area

Figure 4: Detailed map of Shell Creek-Medicine Lodge 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 Shell Creek-Medicine Lodge Creek drainage divide seen in less detail in figure 3. The map contour interval for figure 4 is 40 feet. Emerald Lake is located at the center of figure 4. Shell Creek flows in a northwest direction from Emerald Lake to the northwest corner of figure 4 and then to the Bighorn River west of the Bighorn Mountains. The Edelman Trail extends in a southwest direction from Emerald Lake to the southwest oriented Medicine Lodge Creek valley, with Medicine Lodge Creek flowing to the southwest corner of figure 4. Medicine Lodge Creek flows to Paint Rock Creek, which then flows to the Nowood River west of the Bighorn Mountains. The Edelman Trail crosses the Shell Creek-Medicine Lake Creek drainage divide via a pass with an elevation of 10,465 feet. A high point in the northeast corner of section 28 to the west rises to 10,958 feet and elevations east of the pass rise to more than 11,000 feet suggesting the pass is almost 500 feet deep. North of Emerald Lake is Edelman Pass, which links the Shell Creek valley with the north-northeast oriented Edelman Creek valley, with Edelman Creek flowing to the north edge of figure 4 (east half) and then to the east side of the Bighorn Mountains. The Edelman Pass elevation is only slightly higher than the Emerald Lake elevation of 10,250 feet. Elevations in the northeast corner of section 15 rise to 11,044 feet and elevations to the east of Edelman Pass rise even higher suggesting Edelman Pass is as much as 800 feet deep. Geneva Pass is located in section 31 near the southeast corner of figure 4 and links the north oriented East Fork Big Goose Creek valley with a south oriented Paint Rock Creek tributary valley. South of figure 4 Paint Rock Creek flows in a southwest direction and eventually joins Nowood River. The Geneva Pass elevation is between 10,240 and 10,280 feet. Elevations in section 25 rise to 11,540 feet and elevations greater than 11,600 feet are found east of figure 4. These elevations suggest Geneva Pass is more than 1100 feet deep. Study of figure 4 reveals many other passes crossing the various drainage divides. These passes are all water-eroded features and were eroded by floodwaters crossing the region prior to emergence of the Bighorn Mountains as a high mountain range. Floodwaters initially flowed in south directions to the actively eroding Paint Rock Creek and tributary valleys, although the reversal of flood flow in the Tongue River drainage basin east of the emerging Bighorn Mountains captured southeast oriented flood flow moving on the present day northwest oriented Shell Creek alignment. A reversal of flood flow west of the emerging Bighorn Mountains caused a reversal of flood flow on the Shell Creek alignment, which then created the northwest oriented Shell Creek drainage route.

Trapper Creek-Medicine Lodge Creek drainage divide area

Figure 5: Trapper Creek-Medicine Lodge 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 Trapper Creek-Medicine Lodge Creek drainage divide area west and somewhat south of figure 3 and includes an overlap area with figure 3. The steep Bighorn Mountains west slope is seen in figure 5 with elevations greater than 3000 meters being found near the east edge of figure 5 and elevations of less than 2000 meters being found near the west edge of figure 5 (the map contour interval is 20 meters). Trapper Creek originates near the northeast corner of figure 5 and flows in a southwest west, and northwest direction to the northwest corner of figure 5. The deep Trapper Canyon appears to be eroded into what might be a steely dipping resistant sedimentary rock layer. Medicine Lodge Creek flows in a southwest and south-southwest direction from the east center edge of figure 5 to the south edge of figure 5 (east half). Dry Medicine Lodge Creek (the “Dry” does not show in figure 5) originates north of Iron Mountain (near east center edge of figure 5) and flows in a southwest and south-southwest direction to the south center edge of figure 5.  South of figure 5 Dry Medicine Lodge Creek flows in a south direction to join Medicine Lodge Creek, which then joins southwest oriented Paint Rock Creek. Spanish Point is a labeled high point in the east center region of figure 5. Note how north-to-south oriented through valleys on either side of Spanish Point link the west oriented South Trapper Creek and Trapper Creek valley with the south-southwest oriented Dry Medicine Lodge Creek valley. The Spanish Point elevation is greater than 2800 meters. The through valley east of Spanish Point has an elevation of between 2680 and 2700 meters suggesting the through valley depth is at least 100 meters. The through valley west of Spanish Point has an elevation of between 2660 and 2680 meters, although high points west of the through valley only rise to between 2740 and 2760 meters suggesting the through valley may be 80 meters deep. These and other through valleys linking the Trapper Creek valley with the Dry Medicine Creek valley suggest south oriented flood flow moved across the region prior to headward erosion of the deep west oriented Trapper Creek valley. It is possible the floodwaters flowed in a southeast and east direction along what is now the west and northwest oriented Trapper Creek alignment. Through valleys and valley orientations on the Bighorn Mountains upland surface provide significant evidence suggesting floodwaters came from north and west of the Bighorn Mountains. If so there was no steep west-facing Bighorn Mountains slope at that time and the Bighorn Mountains have since been uplifted and/or the Bighorn Basin has since been deeply downwarped and/or eroded. Probably a combination of uplift and deep erosion explains the emergence of the Bighorn Mountains and Bighorn Basin, which now make such flood flow movement impossible and very difficult to visualize.

Detailed map of Trapper Creek-Medicine Lodge Creek drainage divide area

Figure 6: Detailed map of Trapper Creek-Medicine Lodge 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 Trapper Creek-Medicine Lodge Creek drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 40 feet. South Trapper Creek flows in a southwest and west direction from near the northeast corner of figure 6 to join southwest oriented North Trapper Creek in section 21. From section 21 Trapper Creek flows in a west direction through Trapper Canyon near the north edge of figure 6. Dry Medicine Lodge Creek flows in a southwest and south-southwest direction from the east edge of figure 6 (slightly north of center) into section 4 and then makes a jog to the northwest before turning to flow in a south direction to the south center edge of figure 6. Spanish Point is located in section 33 near the south-southwest oriented Dry Medicine Lodge Creek valley and reaches an elevation of more than 9240 feet. North and west of Spanish Point is west and south oriented Mill Creek, which joins Dry Medicine Lodge Creek at the west edge of section 5 where Dry Medicine Lodge Creek turns from flowing in a northwest direction to flowing in a south direction. North of Spanish Point through valleys link the west oriented Mill Creek valley with the south-southwest oriented Dry Medicine Lodge Creek valley and with the Trapper Creek valley. A road from the northeast corner of section 33 to section 21 makes use of two of these through valleys. The southern through valley links the Mill Creek valley and Dry Medicine Lodge Creek valley and has an elevation of between 8880 and 8920 feet where the road crosses the drainage divide. The northern through valley has an elevation of between 8800 and 8840 feet where the road crosses the Trapper Creek-Mill Creek drainage divide. Elevations east of the through valleys rise much higher than the top of Spanish Point, which suggests the southern through valley may be as much as 380 feet deep. The high point west of northern through valley reaches an elevation of 9112 feet, which suggests the northern through valley is at least 270 feet deep. Depths of these through valleys are small when compared with the Bighorn Mountains west slope elevation change or even with the depths of Trapper Canyon or Dry Medicine Lodge Creek Canyon, but the through valleys are water-eroded features and were eroded by water crossing what are now drainage divides between independent drainage systems. The through valleys can be used to reconstruct a south oriented flood flow channel that was first captured by headward erosion of the south-southwest oriented Dry Medicine Lodge Creek valley, next captured by headward erosion of the Mill Creek valley, and finally captured by Trapper Creek valley headward erosion.

South Sheldon Gulch-Medicine Lodge Creek drainage divide area

Figure 7: South Sheldon Gulch-Medicine Lodge 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 South Sheldon Gulch-Medicine Lodge Creek drainage divide area west and south of figure 5 and includes an overlap area with figure 5. Figure 7 shows the base of the Bighorn Mountains west flank with elevations near the east edge of figure 7 and south of Webber Canyon exceeding 1900 meters and elevations near the west edge of figure 7 being less than 1300 meters (compared to elevations greater than 3000 meters seen in the high Bighorn Mountains to the east in figures 3 and 5). Shell Creek flows in a west direction north of figure 7. Webber Canyon near the northeast corner of figure 7 is a west and northwest oriented Shell Creek tributary, as is South Sheldon Gulch in the northwest quadrant of figure 7. North Sheldon Gulch is the northwest oriented drainage route located immediately east and north of Potato Ridge (near norh center of figure 7). North of figure 7 North Sheldon Gulch and South Sheldon Gulch join to form northwest oriented Sheldon Gulch, which drains to Shell Creek a short distance upstream from the point where Shell Creek joins the north oriented Bighorn River. McDermotts Gulch is a south oriented drainage route in the south center area of figure 7 and drains to the south center edge of figure 7 and then to the northwest and west oriented Nowood River. South-southeast oriented East Fork (McDermotts Gulch) is located east of McDermotts Gulch and joins Nowood River south of figure 7. West of McDermotts Gulch is south-southeast oriented Wild Horse Draw, which joins the west oriented Nowood River as a barbed tributary south of figure 7. The map contour interval for figure 7 is 20 meters. The northwest oriented Shell Creek tributary valleys are linked by through valleys with the south oriented Nowood River tributary valleys. For example near the center of figure 7 a through valley links the northwest oriented South Sheldon Gulch valley with the south oriented McDermotts Gulch valley. The through valley floor elevation is between 1380 and 1400 meters and elevations west of the through valley rise to more than 1420 meters suggesting the through valley is at least 20 meters deep. The through valley and other through valleys like it are evidence of southeast and south-southeast oriented flood flow prior to headward erosion of the west oriented Shell Creek valley. Floodwaters were moving from what is today the north oriented Bighorn River valley to the present day north oriented Nowood River valley. These through valleys are today more than 1500 meters lower in elevation than the through valleys seen in figure 3, yet the through valleys in both figures record similar flood flow movements, which suggests the Bighorn Mountains and Bighorn Basin did not exist as distinct topographic features when floodwaters flowed across the region.

Detailed map of North Sheldon Gulch-East Fork Dermotts Gulch drainage divide area

Figure 8: Detailed map of North Sheldon Gulch-East Fork McDermotts Gulch 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 Sheldon Gulch-East Fork McDermotts Gulch drainage divide area seen in less detail in figure 7. The map contour interval for figure 8 is 20 feet in the west and 40 feet in the east. McDermotts Gulch originates in section 15 (in southwest quadrant of figure 8) and drains in a south direction to the south edge of figure 8 (west half) and south of figure 8 joins the northwest and west oriented Nowood River. East Fork McDermotts Gulch drains in a south-southeast and south direction from section 11 (near center of figure 8) to the south center edge of figure 8 and south of figure 8 makes some southwest jogs to eventually join the Nowood River. Potato Ridge is the “Ridge” or hogback extending in a southeast direction from the northwest corner of figure 8. North Sheldon Gulch originates in section 11 and drains in a northwest direction along the Potato Ridge northeast side to near the northwest corner of figure 8. South Sheldon Gulch drains in a north-northwest direction near the southwest corner of figure 8. North and west of figure 8 North and South Sheldon Gulch join to form northwest oriented Sheldon Gulch, which then drains to west oriented Shell Creek a short distance upstream from where Shell Creek joins the north oriented Bighorn River. In the west half of section 11 a northwest to southeast oriented through valley links the northwest oriented North Sheldon Gulch headwaters valley with the southeast oriented East Fork McDermotts Gulch valley. The through valley floor elevation is between 4880 and 4900 feet. Potato Ridge to the west rises to 5006 feet and the hogback ridge in the southwest quadrant of section 2 rises to more than 5200 feet. These elevations suggest the through valley is more than 100 feet deep. While the through valley is located between what are almost certainly two hogback ridges, which imply structural control of the valley orientation, the through valley is also a water-eroded valley and was eroded by southeast oriented flood flow moving from the present day north oriented Bighorn River valley to the present day north oriented Nowood River valley. The through valley and other similar through valleys in the region provide evidence of multiple flood flow channels as the Bighorn Basin was being eroded and also evidence of south oriented flood flow prior to the reversal of flood flow that created the north oriented Bighorn River drainage system.

East Basin Draw-Nowood River drainage divide area

Figure 9: East Basin Draw-Nowood River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the East Basin Draw-Nowood River drainage divide area west and south of figure 8 and includes an overlap area with figure 8. Basin is the town near the northwest corner of figure 9 and Manderson is the smaller town in the southwest quadrant of figure 9. The Bighorn River flows in a north-northwest and north direction from the south edge of figure 9 (near Manderson) to the north edge of figure 9 (near Basin). The Nowood River flows in a west-northwest and west direction from the south edge of figure 9 (east half) to join the Bighorn River near Manderson. McDermotts Draw is a south oriented Nowood River tributary near the east edge of figure 9. Wild Horse Draw is a south-southeast oriented Nowood River tributary draining from the north edge of figure 9 (slightly west of center) to join the Nowood River near the south edge of figure 9 (near where McDermotts Draw joins the Nowood River). East Basin Draw is a northwest oriented drainage route joining the north oriented Bighorn River a short distance south of Basin. Basin Flats is located directly to the southeast of East Basin Draw and is drained by a southeast oriented Wild Horse Draw tributary. A through valley links the northwest oriented East Basin Draw valley with the southeast oriented Basin Flats valley. The map contour interval for figure 9 is 20 meters and the through valley floor elevation is between 1260 and 1280 meters. Elevations on either side of the through valley rise to more than 1340 meters suggesting the through valley is at least 60 meters deep. Compared to the Bighorn Mountains this through valley is almost insignificant, yet the through valley provides evidence of a former southeast oriented flood flow channel that was eroded prior to the reversal of flood flow in the Bighorn Basin. The southeast oriented flood flow was moving from the present day north oriented Bighorn River valley to the present day north and northwest oriented Nowood River valley (south and east of figure 9). Unlike figures 7 and 8 the East Basin Draw-Basin Flats through valley does not appear to be located between two hogback ridges and probably its orientation was probably not defined by any underlying geologic structures

Detailed map of East Basin Draw-Nowood River drainage divide area

Figure 10: Detailed map of East Basin Gulch-Nowood 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 East Basin Draw-Nowood River drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 20 feet. East Basin Draw originates in the northeast quadrant of section 32 (in northwest quadrant of figure 10) and drains in a southeast and south direction to section 33 and then to section 4 where it turns to drain in a west and northwest direction to the west edge of figure 10 (north half) and west of figure 10 joins the north oriented Bighorn River. The southeast oriented East Basin Draw headwaters provide evidence that what had been a southeast oriented flood flow channel captured southeast oriented flood flow from adjacent flood flow channels when it (the East Basin Draw flood flow channel) was beheaded and reversed so as to flow to the what was then the newly reversed Bighorn River drainage route. South-southeast oriented headwaters of the southeast oriented stream draining Basin Flats originate in the southeast quadrant of section 33 (just east of and adjacent to the south-southeast East Basin Draw headwaters) and then flow across section 3 before turning to drain in a southeast direction to eventually join the northwest and west oriented Nowood River valley as a barbed tributary. A through valley in the east half of section 4 and southwest quadrant of section 3 links the west and northwest oriented East Basin Draw valley with the southeast oriented Basin Flats valley. The through valley floor elevation is between 4200 and 4220 feet. Elevations in section 9 to the south rise to more than 4400 feet. Elevations greater than 4400 feet can also be found in the northwest corner of section 32 to the north. These elevations suggest the through valley is at least 180 feet deep. The through valley is a water-eroded valley and was eroded by southeast oriented flood flow moving from the present day north oriented Bighorn River valley to the present day north and northwest oriented Nowood River valley prior to the reversal of flood flow in the Bighorn Basin. Elevation differences between evidence seen in the Bighorn Mountains (figures 3, 4, 5, and 6) and in the Bighorn Basin (figures 7, 8, 9, and 10) pose interesting questions about how the Bighorn Mountains and Bighorn Basin emerged as distinct topographic features. Both were eroded by south and southeast oriented flood flow that was beheaded and reversed to create the north oriented Bighorn River drainage system. Based on present day topography and elevations such flood flow movements would be impossible, however the topographic map evidence demonstrates such flood flow movements did occur. Obviously the topography at that time was very different from the topography today. How, why, and when the topography was changed are questions that will require significant future research.

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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