North Fork Powder River-Middle Fork Powder River drainage divide area landform origins in the Wyoming southern Bighorn Mountains, USA

Authors

 

 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the region between the North Fork Powder River and the Middle Fork Powder River in the Wyoming southern Bighorn Mountains. The North Fork Powder River originates on the west edge of Bighorn Mountains upland surface and flows in a south direction along the Bighorn Mountains upland surface before turning to flow 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. The northeast oriented Middle Fork Powder River originates further to the south on the west edge of Bighorn Mountains upland surface and is joined northeast and southeast oriented tributaries that also originate on the west edge of the Bighorn Mountains upland surface. The Middle Fork and some Middle Fork tributaries have eroded deep canyons across the Bighorn Mountains upland surface. Through valleys link the North and Middle Fork Powder River valleys and their tributary valleys with much deeper valleys of tributaries to the north oriented Nowood River on the west side of the Bighorn Mountains upland surface. Through valleys also link Middle and North Fork tributary valleys with each other and with the Middle Fork Crazy Woman Creek valley to the north. In addition to the through valleys, barbed tributaries, elbows of capture, and drainage route U-turns are common throughout the study region. The topographic map evidence is interpreted in the context of massive south and southeast oriented floods that once crossed the region. 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 present day Bighorn Mountains. At least initially the Bighorn Mountains had not emerged as a mountain range and floodwaters could freely flow across what is today a major mountain barrier. The Bighorn Mountains emerged as floodwaters flowed across them and as floodwaters deeply eroded the Powder River Basin to the east and the Bighorn Basin to the west. Ice sheet related crustal warping helped raise the Bighorn Mountains and also created a deep “hole” in which the ice sheet was located. A systematic reversal of flood flow directions occurred when ice sheet melting opened up space at the south end of the deep “hole” and the deep northeast oriented Yellowstone River valley eroded headward from that space across Montana to capture the immense south and southeast oriented melt water floods. Floodwaters on north ends of beheaded flood flow routes reversed flow direction to create north oriented drainage routes. Flood flow in the Powder River Basin was beheaded and reversed first to create the north oriented Powder River drainage route, which then captured southeast-oriented flood flow still moving across the southern Bighorn Mountains. Subsequently Yellowstone River valley headward erosion beheaded and reversed flood flow routes to the Bighorn Basin and ended all flood flow to the newly created North Fork and Middle Fork Powder River drainage basins.

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

North Fork Powder River-Middle Fork Powder River drainage divide area location map

Figure 1: North Fork Powder River-Middle Fork 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 North Fork Powder River-Middle Fork Powder River drainage divide in the Wyoming southern Bighorn Mountains and illustrates a region in north central Wyoming. Casper is the largest city shown and is located near the south edge of the southeast quadrant of figure 1. The Bighorn Mountains extend in a north-to south direction from the north center edge of figure 1 to south of the center of figure 1. The Bighorn Basin is located west of the Bighorn Mountains and is drained by the north oriented Bighorn River.  The Powder River Basin is located east of the Bighorn Mountains and is drained by the north oriented Powder River. The Powder River is formed near Kaycee (north of Casper) at the confluence of the southeast oriented North Fork Powder River and northeast oriented Middle Fork Powder River and the north-northeast oriented South Fork Powder River and then flows in an east direction before turning to flow in a north direction to the north edge of figure 1. North of figure 1 the Powder River eventually joins the northeast oriented Yellowstone River in southeast Montana. The North and Middle Forks Powder River drain much of the southern Bighorn Mountains south of Powder River Pass. The Nowood River flows in a northeast, north-northwest, and northwest direction along the west side of the Bighorn Mountains and drains the region directly west of the North Fork and Middle Fork Powder River drainage basins. The Nowood River flows to the north oriented Bighorn River, which north of figure 1 also flows to the northeast oriented Yellowstone River in Montana. The North Fork Powder River-Middle Fork Powder River drainage divide area investigated in this essay is located south and west of the North Fork Powder River, north and west of the Middle Fork Powder River, and east of the Nowood River drainage basin.

Today the Powder River is a north oriented drainage system, which flows to another north oriented drainage system, yet the North Fork Powder River is definitely a south oriented drainage route, which was captured by the north oriented Powder River. How and why did this capture occur? The north oriented drainage routes seen in figure 1 developed during the systematic reversal of immense south oriented melt water floods that once flowed across the entire region seen in figure 1. The floodwaters were coming from the western margin of a thick North American ice sheet and were flowing from western Canada to and across Wyoming. At least initially the Bighorn Mountains and other regional mountain ranges had not emerged and south and southeast oriented floodwaters could freely flow across what are today massive mountain barriers. The Bighorn Mountains emerged as deep south-oriented flood flow channels eroded headward into the adjacent Powder River and Bighorn Basins and as ice sheet related crustal warping uplifted the Bighorn Mountains. The huge ice sheet created a deep “hole” in which the ice sheet was located and the ice sheet related crustal warping raised regions surrounding that deep “hole.” The region seen in figure 1 could be considered to be a segment of the deep “hole’s” deeply eroded and warped southwest rim. At first ice marginal melt water floods flowed in south and southeast directions along and across that southwest rim. In time ice sheet melting opened up space at the south end of the deep “hole”, which at least initially drained in south directions using flood flow channels east of figure 1. The deep northeast oriented Yellowstone River valley then eroded headward across Montana to capture the south and southeast oriented melt water floods. Flood flow routes to Wyoming were beheaded in Montana in sequence from east to west by headward erosion of the much deeper northeast oriented Yellowstone River valley. Floodwaters on north ends of the beheaded flood flow channels reversed flow direction to create new north oriented drainage routes. East and northeast oriented valleys then eroded headward from these new north oriented drainage routes to capture south and southwest oriented flood flow moving west of the actively eroding Yellowstone River valley head (or west of the heads of whatever east or northeast oriented valleys were located to the north). Southeast oriented flood flow on the North Fork Powder River alignment was captured in this manner by headward erosion of an east oriented valley from the newly created north oriented Powder River drainage route.

Detailed location map for North Fork Powder River-Middle Fork Powder River drainage divide area

Figure 2: Detailed location map North Fork Powder River-Middle Fork 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 North Fork Powder River-Middle Fork Powder River drainage divide area in the Wyoming southern Bighorn Mountains. The green colored region represents National Forest lands, which are located in the high Bighorn Mountains. The Bighorn Mountains extend southward from the green colored area to south of the south edge of figure 2. The North Fork Powder River originates in the green colored area just west of Hazelton Peak and flows in a south and southeast direction passing the town of Mayoworth and then making an eastward jog before resuming its southeast direction to join the Middle Fork Powder River east of Kaycee. East of Kaycee the Powder River flows in an east direction to join the north-northeast oriented South Fork Powder River and then to turn and flow in a north direction near the town of Sussex. A labeled southeast oriented North Fork tributary is southeast oriented Pass Creek north of Mayoworth (not to be confused with the south-southeast and northeast oriented Pass Creek south of Mayoworth). The Middle Fork Powder River flows in a northeast, east, and northeast direction from the south edge of figure 2 (west half) to Kaycee and then turns to flow in an east direction to join the southeast oriented North Fork and to form the Powder River. A major labeled tributary of interest in this essay is the southeast oriented Red Fork Powder River with its south-southeast oriented Beartrap Creek tributary, and its north and northeast oriented South Fork tributaries. Also of interest in this essay is northeast, south-southeast, and east oriented Beaver Creek, which flows through the town of Barnum. The Nowood River is the north and north-northwest oriented river west of the Powder River drainage basin flowing through the towns of Bigtrails and Tensleep before flowing to the west edge of figure 2 (and then to the north oriented Bighorn River). Figure 2 shows many more drainage routes than figure 1 and the southern Bighorn Mountains region is primarily drained by south oriented drainage routes flowing to north oriented rivers on either side of the Bighorn Mountains. These south oriented drainage routes were established by south oriented floodwaters as the Bighorn Mountains were emerging and the floodwaters initially flowed to the much deeper south oriented flood flow channels that were eroding headward into the region. Subsequently headward erosion of the deep Yellowstone River valley from space in the deep “hole” being opened up by ice sheet melting beheaded and reversed the south oriented flood flow channels in the Powder River Basin to create the north oriented Powder River drainage route. The newly created north oriented Powder River drainage route then captured most of the south oriented flood flow channels and drainage routes south of the emerging Bighorn Mountains before Yellowstone River valley headward erosion beheaded and reversed flood flow in the Bighorn Basin to the west. For this reason  several Powder River tributaries have eroded deep canyons or water gaps across the Bighorn Mountains upland surface.

East end of the North Fork Powder River-Middle Fork Powder River drainage divide area

Figure 3: East end of the North Fork Powder River-Middle Fork Powder River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of the east end of the North Fork Powder River-Middle Fork Powder River drainage divide area. The map contour interval for figure 3 is 20 meters. Kaycee is the town located near the southeast corner of figure 3. The Middle Fork Powder River flows in a northeast direction from the south edge of figure 3 (east half) to near Kaycee and then turns to flow in east direction to the east edge of figure 3 (near southeast corner). The North Fork Powder River flows in a south-southeast direction from the north edge of figure 3 (near Mayoworth) and then turns to flow in an east, northeast, east, and south-southeast direction to join the Middle Fork Powder east of figure 3. Pine Ridge is a hogback ridge located west of Kaycee. The highest elevations on Pine Ridge exceed 1620 meters. West of Pine Ridge are south and southeast oriented School Section Draw and Alkali Creek with lower hogback ridges between them. West of Alkali Creek is another hogback ridge with elevations rising to 1711 meters at one high point. Between Pine Ridge and that western hogback ridge there are several shallow north to south oriented through valleys linking the North Fork Powder River valley with the Middle Fork Powder River valley. The through valleys are defined by two and three contour lines on a side. While the through valleys probably are located along the strike of less resistant dipping strata the through valleys are water-eroded features and were eroded by south oriented flood flow channels prior to headward erosion of east oriented North Fork Powder River valley segment. Headward erosion of the east oriented North Fork Powder River valley segment beheaded the south oriented flood flow channels and diverted the floodwaters to the present day North Fork Powder River valley. Gardner Mountain and E K Mountain are high hogback ridges located in the west half of figure 3. Pass Creek originates on Gardner Mountain (south of northwest corner of figure 3) and flows in an east direction to the west side of E K Mountain and then in an east-northeast direction around the south end of E K Mountain to join the North Fork Powder River. A deep north to south oriented through valley on the west side of E K Mountain links the southeast oriented Martin Draw valley with the south and east-northeast oriented Pass Creek valley. This through valley is at least 240 meters deep and was eroded by south oriented flood flow prior to headward erosion of the southeast oriented Martin Draw valley. West of E K Mountain is Dull Knife Pass, which is a deep wind gap eroded across Gardner Mountain. A shallower wind gap can also be seen crossing E K. Mountain. These wind gaps were eroded by east and southeast oriented flood flow channels eroding headward to capture south and southeast oriented flood flow before headward erosion of deeper south-southeast oriented valleys on both sides of E K Mountain and Gardner Mountain.

Red Fork Powder River-Middle Fork Powder River drainage divide area

Figure 4: Red Fork Powder River-Middle Fork Powder River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 provides a topographic map of the Red Fork Powder River-Middle Fork Powder River drainage divide area west and south of figure 3 and includes an overlap area with figure 3. The map contour interval for figure 4 is 20 meters. The Middle Fork Powder River flows in a northeast, east, and northeast direction from the south center edge of figure 4 to the east edge of figure 4 (south half). Dull Knife Pass can be seen crossing the north edge of figure 4 (east half) and is eroded across Gardner Mountain as seen in figure 3. The northeast, southeast, and south-southeast oriented stream flowing from the west edge of figure 4 (south half) to Barnum and then in an east direction to join the Middle Fork Powder River is Beaver Creek. Red Draw is a south oriented Bear Creek tributary north of Barnum. The northeast oriented stream flowing across the northwest corner of figure 4 and then turning near the north edge of figure 4 to flow in an east-southeast direction is the South Fork Red Fork Powder River, which joins the southeast oriented North Fork Red Fork Powder near north edge of figure 4-west half) to form the east-southeast and south-southeast oriented Red Fork Powder River, which joins the Middle Fork Powder River near the southeast corner of figure 4. Multiple north-to-south oriented through valleys link the Red Fork Powder River valley (near confluence of South and North Fork s Red Fork Powder River) with south oriented Red Draw and the south-southeast oriented Beaver Creek valley. The through valley floor elevation are between 1740 and 1760 meters. Elevations east of the through valleys rise to 1836 meters suggesting the through valley could be as much as 80 meters deep. The through valleys were eroded by south oriented flood moving from the southeast oriented North Fork Red Fork Powder River alignment to what were at that time the actively eroding Red Draw and Beaver Creek valleys. Headward erosion of the east-southeast oriented Red Fork Powder River valley captured the south oriented floodwaters and diverted the flood flow to the south-southeast oriented Red Fork Powder River valley to the east. Note how the northeast oriented streams flowing from the west edge of figure 4 have eroded deep valleys or canyons into the higher elevations seen near the west edge of figure 4. The higher elevations along the west edge of figure 4 are located on the east side of the high north-to-south oriented Bighorn Mountains crest ridge and deep canyons have been eroded into that crest ridge by Powder River tributaries originating on or near the west side of the Bighorn Mountains crest ridge. The northeast oriented South Fork Red Fork Powder River canyon near the northwest corner of figure 4 is almost 300 meters deep. Figure 5 shows the Beaver Creek canyon better and also shows the even deeper Middle Fork Powder River canyon.

Beaver Creek-Middle Fork Powder River drainage divide area

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

Figure 5 illustrates the Beaver Creek-Middle Fork Powder River drainage divide area west and south of figure 4 and includes a significant overlap area with figure 4. The map contour interval for figure 5 is 20 meters. The north to south oriented Bighorn Mountains crest ridge extends across the center of figure 5 with elevations exceeding 2500 meters at the highest points. North of figure 5 the Bighorn Mountains rise much higher with the highest peaks approaching and even exceeding 4000 meters (see figure 1). A steep west-facing slope can be seen near the west edge of figure 5 and north and northwest oriented drainage to the west edge of figure 5 flows to the north and northwest oriented Nowood River. The steep west-facing slope could be a fault escarpment or it could have been eroded by south oriented flood flow prior to the reversal of flood flow in the Bighorn Basin. The Middle Fork Powder River originates south of the southwest corner of figure 5 and flows in a north and northeast direction to the south edge of figure 5 (west half) and then turns to flow in an east direction to the east edge of figure 5 (between the North River [Slope] and Slope River [Slope]). Note south oriented tributaries to the east oriented Middle Fork Powder River including north-northeast, east, and southeast oriented Rock Creek and southeast oriented Sullivan Creek. Rock Creek and Sullivan Creek are linked by through valleys with the north and south oriented headwaters of a west and north oriented Nowood River tributary valley. These through valley provide evidence of southeast oriented flood flow channels that once flowed from the Bighorn Basin to the Middle Fork Powder River valley. Beaver Creek originates north of the Sullivan Creek headwaters area and flows in a northeast direction almost to the northeast corner of figure 5 and then turns to flow in an east-southeast direction. Blue Creek is a southeast oriented stream originating between the Beaver Creek and Sullivan Creek headwaters and then turning to flow in a northeast and east direction to the east center edge of figure 5. East of figure 5 Blue Creek joins south-southeast oriented Beaver Creek. Note how the southeast oriented Blue Creek headwaters valley is linked by through valleys with a southeast oriented Beaver Creek headwaters valley and with a southeast, east and south oriented Middle Fork Powder River tributary valley. The through valleys are defined by at least five contour lines on a side and are approximately 100 meters. A close at that region reveals other through valleys of varying depths providing evidence of what was once an anastomosing channel complex. The anastomosing channel complex was eroded by southeast oriented flood flow channels that were captured by headward erosion of the deep east oriented Middle Fork Powder River canyon (300-400 meters deep). Headward erosion of Blue Creek valley next captured the southeast oriented flood flow with headward erosion of the Beaver Creek valley beheading the flood flow channels to newly eroded Blue Creek valley. A reversal of flood flow then occurred in the Nowood River drainage basin to the northwest to create the northwest oriented Nowodd River tributary valleys seen in northwest corner of figure 5. The reversal of flood flow may have been aided by Bighorn Mountains uplift that created the steep west-facing slope seen along the present day Nowood River-Powder River drainage divide (near west margin of figure 5).

North Fork Powder River-Red Fork Powder River drainage divide area

Figure 6: North Fork Powder River-Red Fork Powder River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates a topographic map of the North Fork Powder River-Red Fork Powder River drainage divide area north and slightly east of figure 5 and includes a small overlap area with figure 5. The map contour interval for figure 6 is 20 meters. The north to south oriented Bighorn Mountains crest ridge extends across the center of figure 6. Elevations along the crest ridge exceed 2500 meters while elevations decrease towards the east and west margins of figure 6. Drainage flowing to the west edge of figure 6 flows to the north and northwest oriented Nowood River, which then flows to the north-oriented Bighorn River. Beaver Creek flows in a northeast and east-southeast direction from and to the south edge of the southeast quadrant of figure 6. The South Fork Red Fork Powder River flows in a north and northeast direction from the south edge of figure 6 (near southwest corner) through a deep canyon eroded into the high Bighorn Mountains crest ridge and then turns to flow in a east-southeast direction to join the south-southeast and southeast oriented North Fork Red Fork Powder River, which flows from the north edge of figure 6 (west of center). Note how in the southwest quadrant of figure 6 through valleys link the northeast oriented South Fork Red Fork Powder River valley with a south-southwest oriented Nowood River tributary valley (west of figure 6 that tributary makes a northwest and southwest jog and then flows in a northwest direction to join the north oriented Nowood River). Also note how further north shallow west to east oriented through valleys link east oriented North Fork Red Fork Powder River tributary valleys with the much deeper Nowood River valley on the west side of the Bighorn Mountains crest ridge. In fact near the north edge of figure 6 the North Fork Red Fork Powder River is flowing very close to the west edge of the high Bighorn Mountains crest ridge and north of figure 6 (and seen in figure 7) the south-southeast oriented North Fork Red Fork Powder River headwaters are linked by through valleys with the valley of a west oriented Nowood River tributary. In other words water that eroded the North Fork Red Fork Powder River valley came from the Bighorn Basin to the west of the Bighorn Mountains at a time when the Bighorn Basin floor was at least as high as the Bighorn Mountain Mountains crest ridge. Since that time deep erosion of the Bighorn Basin and/or uplift of the Bighorn Mountains has created the Bighorn Mountains western slope seen in the west half of figure 6. Gardner Mountain can be seen along east edge of figure 6. West of Gardner Mountain is Fraker Mountain, which appears to be a steeply dipping hogback ridge. The Red Fork Powder River has eroded a deep water gap across  the south end of Fraker Mountain  and an east oriented wind gap can be seen north of the Red Fork Powder River canyon and provides evidence of an east oriented flood flow channel that preceded headward erosion of the much deeper Red Fork Powder River valley and tributary valleys. .

Pass Creek-Beartrap Creek drainage divide area

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

Figure 7 illustrates the Pass Creek-Beartrap Creek drainage divide area north and slightly east of figure 6 and there is a very thin overlap area with figure 6. The map contour interval for figure 7 is 20 meters. The high Bighorn Mountains crest ridge or upland surface is in the west half of figure 7 and is east of the labeled county line with highest elevations being slightly above 2500 meters. Further north the Bighorn Mountains upland surface and high peaks are much higher. The North Fork Powder River flows in a south and east direction near from the north center edge of figure 7, but quickly turns to flow in a south-southeast direction to the east edge of figure 7 (south half). Pass Creek originates as a north oriented stream in the northwest quadrant of figure 7 but quickly turns to flow in a southeast direction with some east jogs before turning in an east-northeast direction to join the North Fork Powder River in the east center area of figure 7. Beartrap Creek originates south of the Pass Creek headwaters and flows in a southeast, south, south-southeast, and south direction to the south center edge of figure 7. Southwest and west oriented streams (flowing to the west edge of figure 7) flow to the north and northwest oriented Nowood River, which flows to the north oriented Bighorn River. Note through valleys linking the Pass Creek and Beartrap Creek headwaters valley with valleys of the west and southwest oriented Nowood River tributaries. Some these through valleys are defined by five contour lines on a side and may be as much as 100 meters deep. These through valleys provide evidence of east oriented flood flow channels that once crossed the present day Nowood River-Powder River drainage divide. Today the through valley floors are more than 1000 meters higher than the Nowood River valley to the west of figure 7, which means either areas to the west of figure 7 have been deeply and/or the Bighorn Mountains have been significantly uplifted since that time. The east oriented flood flow probably occurred as floodwaters from the yet to eroded Bighorn Basin in the west flowed around the south end of the emerging Bighorn Mountains (what are today the highest Bighorn Mountains  areas north of figure 7 emerged as a barrier before the region in figure 7 emerged as a mountain barrier) to reach flood flow channels in the Powder River basin to the east. Other through valleys link the southeast oriented Pass Creek valley with the southeast oriented Beartrap Creek valley segment. The deepest of these north to south oriented through valleys has a floor elevation of between 2420 and 2440 meters. Elevations both east and west of the through valley rise to more than 2540 meters suggesting the through valley is at least 100 meters deep. This and similar through valleys provide evidence of a south oriented flood flow channels to the actively eroding Beartrap Creek valley that was beheaded by headward erosion of the deeper southeast oriented Pass Creek valley. These south oriented flood flow channels provide evidence of flood flow moving in a south direction along the present day Bighorn Mountains crest ridge or upland surface.

Detailed map of Pass Creek-Beartrap Creek drainage divide area

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

Figure 8 illustrates a detailed topographic map of the Pass Creek-Beartrap Creek drainage divide area seen in less detail in figure 7. The map contour interval for figure 8 is 40 feet. Beartrap Creek flows in a south-southeast and southeast direction from the west edge of figure 8 (north of center) to the south edge of figure 8 (west of center). Pass Creek flows in a southeast, east-northeast, southeast, and east-southeast direction from the north edge of figure 8 (west half) to the east edge of figure 8. A north to south oriented through valley in the southeast corner of section 22 links the Pass Creek valley with the Beartrap Creek valley. The through valley floor elevation is between 7920 and 7960 feet. Elevations east of the through valley rise as high 8375 feet while elevations west of the through valley rise to more than 8400 feet. These elevations suggest the through valley is at least 400 feet deep. The through valley is a water eroded feature and was eroded by south oriented flood flow prior to headward erosion of the deeper Pass Creek valley. Another shallower through valley is located along the border between sections 23 and 24 and links the southeast oriented headwaters of Larramandy Draw with the Pass Creek valley. South of figure 8 Larramandy Draw turns in a southwest direction to join Beartrap Creek. This shallower through valley provides evidence of a second flood flow channel suggesting multiple flood flow channels such as are found in an anastomosing channel complex. The multiple diverging and converging channels are typical of flood formed anastomosing channel complexes and are important evidence in interpreting the through valleys as flood flow channels rather than as channels of streams draining local regions, which are typical of most drainage routes seen today. The diverging and converging flood flow channel complexes require large volumes of water to form especially when the 400-foot deep channels are being eroded and then captured by headward erosion of a still deeper flood flow channel. Such volumes of water are unlikely to have existed in the emerging Bighorn Mountains and probably came from a more distant source. Even rapid melting of small alpine glaciers further north in the higher Bighorn Mountains would be unlikely to produce the water volumes required to eroded the multiple channels seen in figure 8, much less the much larger system of diverging and converging flood flow channels observed and discussed in other figures illustrating this essay.

Middle Fork Crazy Woman Creek-North Fork Powder River drainage divide area

Figure 9: Middle Fork Crazy Woman Creek-North Fork Powder River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Middle Fork Crazy Woman Creek-Middle Fork Powder River drainage divide area north of the figure 7 and includes an overlap area with figure 7. The map contour interval for figure 9 is 20 meters. West oriented streams along the west edge of figure 9 flow to the Bighorn Basin and the north oriented Bighorn River. The North Fork Powder River flows in a south-southwest and south direction from the north edge of figure 9 (west half) and then turns to flow in a southeast direction to Dullknife Reservoir. From Dullknife Reservoir the North Fork Powder River flows in a southeast, south, east, and south-southeast direction to the south edge of figure 9 (east half) and south and east of figure 9 eventually flows to the Powder River Basin and the north oriented Powder River. The Middle Fork Crazy Woman Creek flows in a southeast and east direction from the north edge of figure 9 (east of center) to the east edge of figure 9 (north half) and east and south of figure 9 enters the Powder River Basin with water eventually reaching the north oriented Powder River. Doyle Creek originates near the north edge of figure 9 (west half) and flows in a south, south-southeast, and northeast direction to near the north center edge of figure 9 and then turns to flow in a northeast, east and north direction to join the Middle Fork Crazy Woman Creek. South of the Doyle Creek first or western U-turn is southeast and oriented Bull Creek, which flows to the North Fork Powder River. The first Doyle Creek U-turn history began with two converging flood flow channels. One of the converging flood flow channels was located on the present day south and south-southeast oriented Doyle Creek headwaters alignment. The other converging flood flow channel was located on the present day northeast oriented Doyle Creek alignment. The converging floodwaters then flowed in a southeast and south direction on the present day Bull Creek alignment to what was then the actively eroding North Fork Powder River valley. The second or middle Doyle Creek U-turn was made by two diverging south oriented flood flow channels and two converging flood flow channels made the third or eastern Doyle Creek U-turn. Evidence for these diverging and converging flood flow channels can be seen by studying drainage divides to observe through valleys. Headward erosion of the much deep Middle Fork Crazy Woman Creek valley beheaded and reversed a south oriented flood flow channel to create the north oriented Doyle Creek segment, Next the east oriented Doyle Creek valley segment eroded headward to behead and reverse flood flow on the eastern northeast oriented Doyle Creek segment. That reversal of flood flow captured southeast oriented flood flow on the southeast oriented Doyle Creek segment. Headward erosion of the deeper knick point from the deeper Middle Fork Crazy Woman Creek valley then beheaded the southwest oriented flood flow channel on the western Doyle Creek northeast oriented segment and the resulting flood flow reversal created the western Doyle Creek northeast oriented segment, which then captured flood flow on the south and south-southeast oriented Doyle Creek headwaters segment and beheaded flood flow to the Bull Creek valley.

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

Figure 10: Detailed map of Doyle Creek-North Fork Powder 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 Doyle Creek-North Fork Powder River drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 40 feet. The North Fork Powder River flows in a southeast direction from the west edge of figure 10 (south half) to Dullknife Reservoir and then to the south edge of figure 10 (west of center). Bull Creek originates in section 15 and flows in a southeast direction to section 24 and then turns to flow in a south direction to the south edge of figure 10 (east half) and south of figure 10 joins the southeast oriented North Fork Powder River. Doyle Creek flows in a south-southeast direction from the north edge of figure 10 (between sections 10 and 11) to the north margin of section 14 and then turns to flow in a northeast direction to the north edge of figure 10 (east half) and north of east of figure 10 makes two more complete U-turns before finally flowing to the Middle Fork Powder. A north to south oriented through valley in the west half of section 13 links the Doyle Creek U-turn with the south oriented Bull Creek valley. The through valley floor elevation is between 8400 and 8440 feet. The high point in section 15 to the west is 8936 feet and elevation exceeding 8600 feet can be found near the east edge of section 13 to the east. These elevations suggest the through valley is at least 160 feet deep. The through valley actually extends from the east half of section 13 westward across section 14 to the east half of section 15 with the deepest valley channel being located in the west half of section 13. The through valley was eroded by a south oriented flood flow channel formed by the convergence of a south-southeast flood flow channel on the present day south-southeast oriented Doyle Creek alignment and a southwest oriented flood flow channel on the present day northeast oriented Doyle Creek alignment. Flood flow in the through valley when headward erosion of a much deeper southeast oriented Doyle Creek valley (north of figure 10) beheaded and reversed the southwest oriented flood flow channel to create the northeast oriented Doyle Creek segment. A deeper valley head eroded headward on the newly created northeast oriented Doyle Creek segment and captured the south-southeast oriented flood flow on the south-southeast oriented Doyle Creek segment and ended all flood flow to the Bull Creek valley. Flood flow from west of figure 10 may have continued to flow in the North Fork Powder River valley until beheaded by headward erosion of valleys north and west of figure 10 beheaded all flood flow routes in that region.

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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