Big Hole River-Wise River drainage divide area landform origins, Pioneer Mountains, Beaverhead County, Montana, USA

Authors


Abstract:

This essay uses topographic map evidence to interpret landform origins in the Pioneer Mountains between the north oriented Big Hole River and Wise River in Beaverhead County, Montana. The Big Hole River flows in a north direction along the Pioneer Mountains west flank and then makes a U-turn to flow in a southeast and south direction along the Pioneer Mountains north and east flanks before making another U-turn to flow in a northeast direction to join the north-northeast oriented Beaverhead River and to form the Jefferson River. The Wise River originates in the southern Pioneer Mountains and flows in a north-northwest and north-northeast direction and joins the southeast oriented Big Hole River along the Pioneer Mountains north flank. Numerous through valleys link drainage routes in the region between the north oriented Big Hole River west of the Pioneer Mountains and the north oriented Wise River in the Pioneer Mountains. Many through valleys are oriented in northwest to southeast directions and appear to have been eroded by diverging and converging flood flow channels in what was a large-scale anastomosing channel complex. If correctly interpreted floodwaters crossed the Pioneer Mountains at a time when the deep Big Hole River valley north and west of the Pioneer Mountains did not exist and when the Pioneer Mountains did not stand high above surrounding regions as they do today. The south oriented Big Hole River valley located east of the Pioneer Mountains was probably eroded by south oriented flood flow, which was captured by headward erosion of the deep Jefferson River valley so as to form the Big Hole River U-turn east of the Pioneer Mountains. Many valleys in the Pioneer Mountains probably were eroded initially as south oriented flood flow channels before being beheaded and reversed so as to create the north oriented drainage routes seen today. The Pioneer Mountains were probably being uplifted as floodwaters flowed across them and this uplift probably contributed to the flood flow reversals. The north oriented Big Hole River valley (and basin) west of the Pioneer Mountains was probably initially eroded by headward erosion of a deep south oriented flood flow channel along the emerging Pioneer Mountains west flank, which beheaded and reversed southeast oriented flood channels so as to erode what are today northwest oriented Big Hole River tributaries. Later uplift of the Big Hole Basin area west of the Pioneer Mountains contributed to a reversal of flood flow that resulted in creation of the north oriented Big Hole River drainage system west of the Pioneer Mountains.

Preface

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

Introduction

The purpose of this essay is to use topographic map interpretation methods to explore the Big Hole River-Wise River drainage divide area landform origins in the Pioneer Mountains in Beaverhead County, Montana and 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 Big Hole River-Wise River drainage divide area landform evidence in the Pioneer Mountains in Beaverhead County, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Big Hole River-Wise River drainage divide area location map

Figure 1: Big Hole River-Wise 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 Big Hole River-Wise River drainage divide in the Pioneer Mountains in Beaverhead County, Montana and illustrates in the east half a region in southwestern Montana with Idaho west and south of Montana except in the southeast corner of figure 1 where an area in Yellowstone National Park in the northwest corner of Wyoming is present. The Pioneer Mountains are located near the center of figure 1 and the Big Hole River flows in a north direction along the west side of the Pioneer Mountains then turns and flows in a southeast and south direction on the east side of the Pioneer Mountains before making still another U-turn to flow in a northeast direction to join the north-northeast oriented Beaverhead River and to form the northeast and east oriented Jefferson River. The Missouri River is formed near the town of Three Forks (located near east center edge of figure 1) at the confluence of the Gallatin, Madison, and Jefferson Rivers and flows in a north and north-northwest direction to the north edge of figure 1. North and east of figure 1 the Missouri River turns to flow in a northeast and then east direction to North Dakota where it turns to flow in a southeast and south direction with water eventually reaching the Gulf of Mexico. The Wise River is shown, but not labeled in figure 1 and flows in a north-northwest and north-northeast direction in the heart of the Pioneer Mountains to join the Big Hole River near the town of Wise River. The Big Hole River-Wise River drainage divide area investigated in this essay is located between the north oriented Big Hole River on the west side of the Pioneer Mountains and the north oriented Wise River.

Before looking at detailed maps of the Big Hole River-Wise River drainage divide area a brief look at the big picture erosion history is appropriate. Large volumes of south and southeast oriented floodwaters once flowed across the region shown by figure 1. Floodwaters were derived from the western margin of a rapidly melting thick North American ice sheet and were flowing in a south and southeast direction from southwest Alberta and southeast British Columbia to and across the figure 1 region. At that time the high mountain ranges and deep valleys and basins that exist today did not exist and floodwaters formed large anastomosing complexes of diverging and converging south oriented flood flow channels as they flowed freely across the region. The mountains ranges and valleys and basins emerged caused by crustal warping related to the presence of a huge continental ice sheet north and east of figure 1 and related to the massive erosion and deposition occurring as floodwaters flowed across the region.  North oriented rivers in figure 1 are generally flowing in valleys that originated as south oriented flood flow channels. The north oriented drainage system seen today were formed during massive flood flow reversals that occurred as mountain ranges and high plateaus were uplifted by ice sheet related crustal warping, which occurred as floodwaters flowed across the region. During these flood flow reversals south oriented flood flow along one route would be captured so as to flow in a north direction along an adjacent route. In addition, deep flood water erosion of valleys and basins surrounding the rising mountain ranges contributed to the emergence of present day mountain ranges.

The south oriented Big Hole River segment east of the Pioneer Mountains is one of the few river segments seen in figure 1 that is still flowing in a south direction. Before being captured by a massive flood flow reversal that took place in the figure 1 east half the south oriented flood flow continued in a south direction to what is now the Snake River drainage basin in eastern Idaho and the northwest corner of Wyoming. The north oriented Big Hole River segment west of the Pioneer Mountains and the north oriented Wise River in the Pioneer Mountains flow on alignments of what began as south oriented flood flow channels, but which were reversed to create the north oriented drainage systems seen today. Reversal of flood flow in the Big Hole River valley west of the Pioneer Mountains and in the Wise River valley in the Pioneer Mountains probably occurred when crustal uplift raised areas in the south relative to areas in the north and as a deep southeast oriented valley eroded headward from the south oriented flood flow channel east of what was then the emerging Pioneer Mountains. The northeast oriented Missouri River valley (north and east of figure 1) and its east and northeast oriented tributary valleys eroded headward from the deep “hole” in which the decaying ice sheet was located. The north-northwest oriented Missouri River valley segment (seen in the figure 1) was eroded by reversals of flood flow on north and northwest ends of beheaded flood flow channels. Reversal of flood flow in the Jefferson River valley captured south oriented flood flow on the present day south oriented Big Hole River alignment (east of the Pioneer Mountains), which created the present day Big Hole River U-turn east of the Pioneer Mountains.

Detailed location map for Big Hole River-Wise River drainage divide area

Figure 2: Detailed location map Big Hole River-Wise 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 Big Hole River-Wise River drainage divide area in the Pioneer Mountains in Beaverhead County, Montana and shows drainage routes not seen in figure 1. Green shaded areas are National Forest lands, which generally are located in mountainous regions. The east-west continental divide is shown with a dashed line along the Anaconda Range crest in the northwest corner of figure 2. The Big Hole River flows in a north direction from the south edge of figure 2 (west half) to the town of Wisdom and then gradually turns to flow in a northeast direction to the town of Fishtrap. From Fishtrap the Big Hole River gradually turns to flow in a southeast direction to the towns of Wise River and Divide and then flows in a south direction almost to the south edge of figure 2 before making a U-turn to flow in a northeast direction. The north-northeast oriented Beaverhead River flows across the southeast corner of figure 2 and joins the Big Hole River near the east edge of figure 2 to form the north-northeast oriented Jefferson River, which flows to the east edge of figure 2. Torrey Mountain is located near the south center edge of figure 2 and is located in the Pioneer Mountains. The Wise River originates near Torrey Mountain and flows in a north-northwest and north-northeast direction and joins the Big Hole River near the town of Wise River. The Big Hole River-Wise River drainage divide area investigated in this essay is located west of the Wise River and east of the north oriented Big Hole River on the west side of the Pioneer Mountains. The major labeled Wise River tributary shown on figure 2 in this region is Pettengill Creek (note: spelling varies on different maps shown in this essay and the essay uses the spelling shown on the most detailed topographic maps). West of Pettengill Creek are west oriented Steel Creek and northwest oriented Doolittle Creek, which flow to the north oriented Big Hole River. North of Doolittle Creek is northwest oriented Squaw Creek, which flows to the northeast oriented Big Hole River. Note the north-northeast oriented streams including Alder Creek north of Pettengill Creek flowing to the southeast oriented Big Hole River segment west of the Wise River. The northwest oriented tributaries to the north and northeast oriented Big Hole River from the southeast and southeast oriented tributaries from the northwest suggest the region was crossed by southeast oriented flood flow channels prior to emergence of the Pioneer Mountains and erosion/formation of the deep north and northeast oriented Big Hole River valley/basin. The southeast oriented flood flow was probably initially captured by headward erosion of the deep south oriented valley on the alignment of the present day north oriented Big Hole River. The northwest oriented tributary valleys were eroded by reversals of flood flow on northwest ends of beheaded flood flow channels. The present day northeast oriented Big Hole River valley was probably headward as a deep southwest oriented flood flow channel at the same time as a diverging and deep southeast oriented flood flow channel eroded headward along the east side of the emerging Pioneer Mountains. Headward erosion of the deep southeast oriented flood flow channel captured south oriented flood flow moving to a south oriented flood flow channel on the present day north oriented Wise River alignment. Crustal warping, which was occurring as floodwaters flowed across the region, at about the same time raised the Pioneer Mountains sufficiently that flood flow in the Wise River flood flow channel reversed flow direction to create the present day north oriented Wise River drainage system. Subsequently crustal warping created topographic barriers that caused a reversal of flood flow west of the emerging Pioneer Mountains, which created the present day north oriented Big Hole River drainage system there.

Big Hole River-Bryant Creek drainage divide area

Figure 3: Big Hole River-Bryant 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 Big Hole River-Bryant Creek drainage divide area. The Big Hole River flows in a northeast direction from the west center edge of figure 3 to near the north edge of figure 3 and then flows in an east and southeast direction to the east edge of figure 3 (south of center). The Wise River can just barely be seen flowing in a northeast direction in the southeast corner of figure 5. Tributaries to the northeast oriented Big Hole River segment are oriented in southeast directions from the northwest and in northwest directions from the southeast. Tributaries from the south to the southeast oriented Big Hole River segment seen in figure 3 are oriented in north and northeast directions. The westernmost of the northeast oriented Big Hole River tributaries is Bryant Creek, which has some southeast oriented tributaries from the northwest and some northwest oriented tributaries from the southeast. East and south of Bryant Creek is north and northeast oriented Alder Creek, which also has some southeast-oriented tributaries from the northwest. Note how the Big Hole River-Bryant Creek drainage divide and the Bryant Creek-Alder Creek drainage divide are crossed by through valleys or mountain passes, which link tributary valleys on the northwest side of the drainage divide with tributary valleys on the southeast side of the drainage divide. For example near Calvert Hill between the Big Hole River and Bryant Creek are through valleys linking the northwest oriented Pony Creek valley with the southeast oriented Dowell Creek valley and linking the northwest oriented Walker Creek valley with the east and southeast oriented Calvert Creek valley. The map contour interval for figure 3 is 50 meters and the Pony Creek-Dowell Creek through valley floor elevation at the drainage divide is between 2100 and 2150 meters. The hill to the northeast rises to 2287 meters and Calvert Hill to the southwest rises to 2370 meters suggesting the through valley is at least 137 meters deep. The Walker Creek-Calvert Creek through valley floor elevation at the drainage divide is between 2250 and 2300 meters. Trident Peak to the south rises to 2429 meters suggesting the through valley is at least 70 meters deep. These through valleys are water-eroded features and were eroded as southeast oriented flood flow channels prior to the existence of the deep Big Hole River valley to the northwest. At that time the Pioneer Mountains did not stand high above surrounding regions as they do today and southeast oriented flood flow could freely flow across the region. Headward erosion of a deep southwest oriented valley on the alignment of the present day northeast oriented Big Hole River beheaded the southeast oriented flood flow channels and floodwaters on the northwest ends of the beheaded flood flow channels reversed flow direction to erode the northwest oriented tributary valleys seen today.

Detailed map of Pony Creek-Dowell Creek drainage divide area

Figure 4: Detailed map of Pony Creek-Dowell 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 Pony Creek-Dowell Creek drainage divide area seen is less detail in figure 3. The Big Hole River can be seen flowing in an east-northeast direction in the northwest corner of figure 4 and the east-southeast oriented Big Hole River valley edge can be seen in the northeast corner of figure 4. Bryant Creek flows in a northeast direction across the southeast quadrant of figure 4. Calvert Hill is located in sections 11 and 12 in the southwest quadrant of figure 4. Pony Creek originates on the Calvert Hill north slopes and flows in a north and northwest direction to join the east-northeast oriented Big Hole River just north of the north edge of figure 4. Dowell Creek flows in a southeast and south direction from Moose Park in the northwest corner of section 7 to join northeast oriented Bryant Creek as a barbed tributary near the west edge of section 8. A through valley in the southeast corner of section 1 links the northwest oriented Pony Creek valley and the southeast oriented Dowell Creek valley. The map contour interval for figure 4 is 40 feet and the through valley elevation at the drainage divide is between 6860 and 7000 feet. The hill in section 6 to the northeast rises to 7502 feet while Calvert Hill in section 12 to the southwest rises to 7775 feet suggesting the through valley is at least 500 feet deep. West of Calvert Hill in section 11 are headwaters of northwest oriented Walker Creek, which flows to the northeast oriented Big Hole River west of figure 4. South of Calvert Hill is northeast and southeast oriented Calvert Creek, which also joins Bryant Creek as a barbed tributary. A through valley also links the Walker Creek and Calvert Creek valleys. The through valley floor elevation at the drainage is between 7440 and 7480 feet. While not seen in figure 4 elevations to the southwest rise even higher than the top of Calvert Hill suggesting this second through valley is at least 300 feet deep. Southeast oriented flood flow channels eroded these through valleys at a time when the deep Big Hole River to the northwest and west did not exist. Floodwaters were at that time probably flowing to a newly eroded deep valley on the Bryant Creek alignment, which suggests the southeast oriented Big Hole River north and east of figure 4 may have been actively being eroded at that time. The northwest oriented Big Hole River tributary valleys were eroded by reversals of flood flow on northwest ends of beheaded flood flow channels as a deep southwest oriented valley eroded headward along the present day northeast oriented Big Hole River alignment west of figure 4.

Squaw Creek-Pettengill Creek drainage divide area

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

Figure 5 illustrates the Squaw Creek-Pettengill Creek drainage divide area south and west of figure 3 and includes an overlap area with figure 3. The northeast oriented Big Hole River and a meander can be seen near the gravel pits in the northwest corner of figure 5. Squaw Creek is the northwest oriented tributary joining the Big Hole River at the northwest corner of figure 5. Papoose Creek and Shaw Creek are northwest oriented Squaw Creek tributaries. Note other northwest oriented Big Hole River tributaries in the northwest quadrant of figure 5. The northwest oriented stream with a North Fork, Middle Fork, and South Fork in the southwest quadrant of figure 5 is Doolittle Creek, which will be seen again in figures 7 and 8. Bryant Creek is the north oriented stream flowing to the north center edge of figure 5. East of Bryant Creek and of Foolhen Ridge is northeast oriented Alder Creek. The Wise River flows in a north-northeast direction across the southeast corner of figure 5. The east-northeast, east-southeast, and east-northeast oriented stream joining the Wise River near Needle Rock is Pettengill Creek. The south oriented Pettengill Creek tributary originating near Foolhen Mountain (near center of figure 5) is Lost Horse Creek. Northeast and southeast oriented Stone Creek joins Pettengill Creek just west of Lost Horse Creek. Note how the northwest oriented Squaw Creek headwaters, including the Papoose Creek and Shaw Creek headwaters, are linked by through valleys with the south oriented Lost Horse Creek valley and the southeast oriented Stone Creek valley. The pattern of valleys seen in this region suggests the valleys originated as diverging and converging southeast oriented flood flow channels at a time when the deep Big Hole River valley to the northwest did not exist. Headward erosion of a deep valley on the Big Hole River alignment combined with uplift of the Pioneer Mountains created the present day drainage divide with floodwaters on northwest ends of the beheaded flood flow channels reversing flow direction to erode the northwest oriented valleys seen today. The flood flow reversal was complex with flood flow channels being beheaded and reversed one channel at a time. Reversed flood flow in a newly beheaded flood flow channel could capture flood flow from yet to be beheaded flood flow channels, which resulted in situations where floodwaters were flowing in one direction in a newly beheaded and reversed flood flow channel while floodwaters were flowing in the opposite direction in an adjacent yet to be beheaded flood flow channel.

Detailed map of Squaw Creek-Stone Creek drainage divide area

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

Figure 6 provides a detailed topographic map of the Squaw Creek-Stone Creek drainage divide area seen in less detail in figure 5. Shaw Mountain is located in the southeast quadrant of section 29. Shaw Creek originates west of Shaw Mountain and flows in a north-northwest direction to the north edge of figure 6 (west half) and joins northwest oriented Squaw Creek north of figure 6. Stone Creek flows in a northeast direction from the south edge of figure 6 (west half) to the south margin of section 22 and then turns to flow in a southeast direction to the south edge of figure 6 (east half) and joins Pettengill Creek south of figure 6. Note in section 22 the deep through valley linking the north-northwest oriented Shaw Creek valley with the southeast oriented Stone Creek valley. The map contour interval for figure 6 is 40 feet and the through valley floor elevation at the drainage divide is between 7840 and 7880 feet. Shaw Mountain to the northeast rises to 8960 feet and elevations greater than 9000 feet are found just south of figure 6. These elevations suggest the through valley is almost 1000 feet deep. The through valley is a water-eroded valley and was eroded by southeast oriented flood flow at a time when the deep Big Hole River valley to northwest did not exist.  Other through valleys can also be seen be seen in figure 6. For example in the west half of section 31 a through valley links a north oriented Shaw Creek tributary valley with a southeast oriented Stone Creek tributary valley. This second through valley suggests there were diverging and converging flood flow channels such as might be found in a southeast oriented anastomosing channel complex. A through valley in section 28 links the northwest oriented Papoose Creek valley with the southeast oriented Effie Creek valley (Effie Creek flows to south oriented Lost Horse Creek). And in the northeast corner of figure 6 is a deep through valley linking the northwest oriented Squaw Creek headwaters valley with the south oriented Lost Horse Creek valley.

Big Hole River-Pettengill Creek drainage divide area

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

Figure 7 illustrates the Big Hole River-Pettengill Creek drainage divide area south and west of figure 5 and includes an overlap area with figure 5. Wisdom is the town located in the southwest quadrant of figure 7. The Big Hole River flows in a north direction from the southwest corner of figure 7 to Wisdom and then to near the north edge of figure 7 before beginning to turn in a northeast direction to flow to the north edge of figure 7 (west half). The northwest oriented Big Hole River tributary in the north center area of figure 7 with a North Fork, Middle Fork, and South Fork is Doolittle Creek, which joins the Big Hole River north of figure 7. South and west of Doolittle Creek is northwest oriented McVey Creek, which joins the Big Hole River near the Gravel Pit in the northwest corner area of figure 7. Steel Creek is the west oriented stream flowing to near Wisdom and then turning to flow in a north direction to join the Big Hole River. Bobcat Mountain is a labeled high point in the southeast quadrant of figure 7. The north and northeast oriented stream just west and north of Bobcat Mountain is Pettengill Creek (spelled Pattengall on figure 7) which turns to flow in an east-southeast direction to the east edge of figure 7. East of figure 7 Pettengill Creek turns to flow in an east-northeast direction and joins the northeast oriented Wise River. Lacy Creek is an east-northeast oriented Wise River tributary located south of Bobcat Mountain. Note how the northwest oriented Middle and South Forks of Doolittle Creek are linked by well-defined through valleys with the valley of an east-southeast oriented Pettengill Creek tributary. The map contour interval for figure 7 is 50 meters and the through valley floor elevations at their drainage divides are between 2500 and 2550 meters. Near Stone Lakes to the north elevations rise to 2774 meters while near Elbow Lake (near south center edge of figure 7) elevations rise to more than 2850 meters suggesting the two parallel through valleys are at least 200 meters deep. The two parallel through valleys provide more evidence of diverging and converging southeast oriented flood flow channels that once crossed what is now the Big Hole River-Pettengill Creek drainage divide. At that time there no deep Big Hole River to the northwest and the Pioneer Mountains were probably just beginning to emerge. Headward erosion of the deep Big Hole River valley (probably as a south oriented valley) beheaded and reversed the southeast oriented flood flow and created the northwest oriented Doolittle Creek drainage system.

Detailed map of Doolittle Creek-Pettengill Creek drainage divide area

Figure 8: Doolittle Creek-Pettengill Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 provides a topographic map of the Doolittle Creek-Pettengill Creek drainage divide area seen in less detail in figure 7. Pettengill Creek flows in a northeast direction across the southeast corner of figure 8. The Middle Fork Doolittle Creek originates near the center of figure 8 and flows in a north-northwest direction from the west margin of section 13 to the north center edge of figure 8. The South Fork Doolittle Creek originates in the northwest corner of section 23 and flows in a northwest and north direction to the north edge of figure 8 (west half). The Middle Fork and South Fork Doolittle Creek valleys are linked by through valleys in the northwest quadrant of section 24 and the southeast quadrant of section 23 with an east and southeast oriented Pettengill Creek tributary valley. The deeper through valley is located is located in section 23 and links the South Fork Doolittle Creek valley with the Pettengill Creek valley. The map contour interval for figure 8 is 40 feet and the deeper through valley floor elevation at the drainage divide is between 8240 and 8280 feet. The hill in the section 26 to the south rises to 9012 feet while the hill in the southeast corner of section 13 rises to more than 8960 feet suggesting the through valley is approximately 700 feet deep. The through valley in section 24 is slightly higher in elevation with a floor elevation of between 8320 and 8360 feet and is approximately 600 feet deep. These two through valleys converge in section 24 while today the South and Middle Forks of Doolittle Creek converge north of figure 8. These valleys provide evidence of diverging and converging southeast oriented flood flow channels that once crossed the Big Hole River-Pettengill Creek drainage divide. At that time there was no high drainage divide and the deep Big Hole River valley to the northwest did not exist. Crustal warping that raised the drainage divide and headward erosion of a deep valley on the Big Hole River alignment resulted in the reversal of flood flow that created the northwest oriented Doolittle Creek drainage system and the present day drainage divide.

Pettengill Creek-Wise River drainage divide area

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

Figure 9 illustrates the Pettengill Creek-Wise River drainage divide area south and east of figure 7 and includes an overlap area with figure 7. The Wise River is formed at the confluence of several tributaries east of Saymore Mountain in the southeast quadrant of figure 9 and then flows in a northwest direction to Big Point before turning to flow in a north-northeast direction to the north edge of figure 9 (east half). Wyman Creek is the northeast oriented stream joining the Wise River near Big Point. Note the south and southeast oriented Wyman Creek tributaries, which flow to Wyman Creek as barbed tributaries, and how they are linked by through valleys eroded across the Table Mountain ridge. Bobcat Mountain is located in the northwest quadrant of figure 9. Lacy Creek originates south of Bobcat Mountain and flows in an east-northeast and east-southeast direction to join the north-northeast oriented Wise River as a barbed tributary north of Big Point. West of Bobcat Mountain are north oriented headwaters of Pettengill Creek, which then turn to flow in a northeast direction to the north edge of figure 9 (west half). Note how the north oriented Pettengill Creek valley is linked by a through valley with east oriented Lacy Creek valley. Lambretch Creek is a southeast and north-northeast oriented stream near the north center edge of figure 9 and north of figure 9 flows to Pettengill Creek. Note how a through valley links the deep north-northeast oriented Lambretch Creek valley with the Lacy Creek valley at the point where Lacy Creek turns to flow in an east-southeast direction. Also note how south of that through valley is a north oriented Lacy Creek tributary, which is linked by a north-to-south oriented through valley across Table Mountain with south oriented Table Creek, which flows to northeast oriented Wyman Creek as a barbed tributary. The map contour interval for figure 9 is 50 meters and the Lambretch Creek-Lacy Creek through valley floor elevation is between 2150 and 2200 meters. The hill directly to the east rises to more than 2550 meters while Bobcat Mountain to the west rises even higher suggesting the through valley is at least 350 meters deep. Through valleys crossing drainage divides in figure 9 provide more evidence of diverging and converging south and southeast oriented flood flow channels that once crossed the region. The flood flow channels were captured by headward erosion of deeper northeast oriented valleys and north and northwest oriented valleys were formed by reversals of flow on the north and northwest ends of beheaded flood flow channels. Figure 9 does not do justice to the pattern of anastomosing through valleys seen in the hearty of the Pioneer Mountains today. I encourage readers to study larger mosaics of maps or  to use digital maps where it is possible to look at larger regions than figures seen in this essay show.

Detailed map of Pettengill Creek-Lacy Creek drainage divide area

Figure 10: Detailed map of Pettengill Creek-Lacy Creek 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 Pettengill Creek-Lacy Creek drainage divide area seen in less detail in figure 9. Pettengill Creek originates near Elbow Lake in section 12 (in southwest quadrant of figure 10) and flows in a northeast and north-northwest direction to the north edge of figure 10 (west half). Lacy Creek originates just south of the northeast oriented headwaters in section 7 and flows in a northeast direction across the south end of the north oriented Pettengill Creek valley and drops into a much deeper east-northeast oriented valley to flow to the east edge of figure 10 (north of center). Lakes and other features in figure 10 suggest the region was probably at one time glaciated, although the valleys predate the glaciers and were eroded by floodwaters flowing across the region. Odell Lake near the south center edge of figure 10 is the headwaters of southeast oriented Odell Creek, which south of figure 10 flows to northeast oriented Wyman Creek as a barbed tributary. The history of valleys in figure 10 probably began with south and southeast oriented flood flow moving from the Pettengill Creek alignment to the Odell Creek alignment. At that time the Lacy Creek alignment was probably being used by a west-southwest oriented flood flow channel moving floodwaters to the southeast oriented Odell Creek flood flow channel. Headward erosion of the deep northeast oriented Wise River valley (east of figure 10) then reversed the direction of flow in the Lacy Creek flood flow channel, which then captured all of the south oriented flood flow, which had been moving to the southeast oriented Odell Creek flood flow channel. With this captured flood flow a much deeper Lacy Creek valley was able to erode headward to the south end of the Pettengill Creek valley. As stated the region was subsequently glaciated with valley glaciers, which streamlined valley walls and further modified the landscape. However, the deep Pettengill Creek-Lacy Creek through valley remains (it is more than 1200 feet deep-the map contour interval is 40 feet) and is evidence of a former flood flow capture point.

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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