Madison River-Gallatin River drainage divide area landform origins in Madison Range (middle), Madison and Gallatin Counties, Montana, USA

Authors


Abstract:

This essay uses topographic map evidence to interpret landform origins between the Madison River and Gallatin River in the middle Madison Range area located in Madison and Gallatin Counties, Montana. The Madison River flows in north direction from near the northwest corner of Yellowstone National Park on the west side of the Madison Range while the Gallatin River flows from the northwest corner of Yellowstone National Park in a north direction on the east side of the Madison Range. North of the Madison Range the Gallatin River turns to flow in a northwest direction to join the Madison River and northeast oriented Jefferson River and to form the north oriented Missouri River. In the study region a north-to-southeast oriented through valley or mountain pass links the northwest oriented Jack Creek valley with the southeast Middle Fork West Fork Gallatin River, which flows through Big Sky to join the north oriented Gallatin River. Further south other northwest-to-southeast oriented through valleys cross the Madison River-Gallatin River drainage divide. These through valleys or mountain passes were eroded by southeast and south oriented flood flow channels as the Madison Range was emerging. At that time the deep Madison River valley to the west did not exist and floodwaters could freely flow across what is today a high mountain range. Emergence of the Madison Range occurred as floodwaters flowed across the region. The north oriented Madison and Gallatin Rivers are flowing in valleys that were initiated as south oriented flood flow channels, and which were reversed in flow direction as floodwaters flowed across the region. Floodwaters were derived from the western margin of a thick North American ice sheet, which was located in a deep “hole”, and were flowing in south and southeast directions from western Canada across Montana. Mountain ranges and high plateau areas emerged as ice sheet related tectonic activity created the deep “hole” in which the ice sheet was located and as deep south oriented valleys eroded headward into the rising mountain masses. Headward erosion of a much deeper northeast oriented Missouri River valley segment north of the study region from space in the deep “hole” being opened up by ice sheet melting beheaded the south oriented flood flow channel supplying floodwaters to the south oriented flood flow channels on the Madison and Gallatin River alignments. Floodwaters on the north end of one beheaded flood flow channel reversed flow direction to create the north oriented Missouri River drainage route. This massive flood flow reversal was greatly aided by ice sheet crustal warping that was raising the Madison Range and other area uplands including Yellowstone Plateau south of the study region where the present day north oriented Madison and Gallatin River originate.

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 Madison River-Gallatin River drainage divide area landform origins in the middle Madison Range located in Madison and Gallatin Counties, 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 Madison River-Gallatin River drainage divide area landform evidence in the middle Madison Range region of Madison and Gallatin Counties, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Madison River-Gallatin River drainage divide area location map

Figure 1: Madison River-Gallatin 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 Madison River-Gallatin River drainage divide in the middle Madison Range located in Madison and Gallatin Counties, Montana and illustrates in the north a region in southwest Montana with the northwest corner of Wyoming and the northern region of Yellowstone National Park appearing in the southeast quadrant of figure 1 and a thin strip of Idaho located along the south edge of figure 1 west of Yellowstone National Park. The Madison Range is labeled and is located near the center of figure 1. The Madison River originates in Yellowstone National Park south of Mount Holmes and flows in a northwest direction to Hebgen Lake (just west of Yellowstone National Park along south edge of figure 1) and then flows in a west to direction to Earthquake Lake before turning to flow in a north direction along the west side of the Madison Range to Three Forks, Montana. At Three Forks the north oriented Madison River joins the north and northwest oriented Gallatin River and the northeast and east oriented Jefferson River to form the north oriented Missouri River, which flows to the north center edge of figure 1. North of figure 1 the Missouri River turns to flow in a northeast and then east direction to North Dakota where it turns again to flow in a southeast and south direction with water eventually reaching the Gulf of Mexico. The Gallatin River originates in the northwest corner of Yellowstone National Park and flows in a northwest and north direction to near Big Sky, Gallatin Gateway and Manhattan before turning to flow again in a northwest direction to join the Madison and Jefferson Rivers at Three Forks. This essay investigates landform origins in the middle Madison Range area and separate essays addresses landforms in the northwest Yellowstone Park region to the south and in the northern Madison Range area extending northward to Three Forks.

A brief look at the big picture erosion history will help understand discussions related to detailed maps shown below. 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 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. North oriented rivers in figure 1, including the north oriented Madison, Gallatin, and Missouri Rivers, are generally flowing in valleys that originated as south oriented flood flow channels. When floodwaters first flowed across the region the mountain ranges, deep river valleys, and basins between the mountains did not exist and floodwaters could freely flow across the region. Mountain ranges emerged as floodwaters flowed across the region and initially floodwaters flowed across what are today high mountain ranges including the Madison Range. The Madison and Gallatin Rivers originated as a south oriented flood flow channels, which were subsequently reversed to form the north oriented drainage routes seen today. The flood flow reversal was probably indirectly caused by crustal warping that occurred as melt water floods flowed across the region with the crustal warping being related to the thick ice sheet presence north and east of figure 1, although the direct cause was headward erosion of a deep northeast oriented valley across Montana (north of figure 1), which beheaded the south oriented flood flow channels supplying floodwaters to the south oriented Madison and Gallatin River flood flow channels. The deep northeast oriented valley was eroding headward from space in the deep “hole” the melting ice sheet had occupied and was capturing the south and southeast oriented ice-marginal melt water floods and diverting the floodwaters into the deep “hole” the ice sheet had formed. This northeast oriented valley was much deeper than the beheaded flood flow channels and floodwaters on north ends of the beheaded flood flow channels reversed flow direction to create the north oriented Missouri River segment and the north oriented Madison and Gallatin River drainage routes seen in figure 1.

Detailed location map for Madison River-Gallatin River drainage divide area

Figure 2: Detailed location map Madison River-Gallatin 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 Madison River-Gallatin River drainage divide area in the middle Madison Range located in Madison and Gallatin Counties, 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 northwest corner of Yellowstone National Park and of Wyoming is located in the southeast corner of figure 2. The Madison-Gallatin County line extends from the north edge to the south edge of figure 2 (slightly east of center) and Madison County is labeled. The Madison River flows in a southwest direction from Hebgen Dam (near south edge of figure 1 slightly east of center) to Earthquake Lake and then to the south center edge of figure 2. South of figure 2 the Madison River turns to flow in a north direction from the south edge of figure 2 (slightly west of center) to Ennis Lake near the north edge of figure 2. North of figure 2 the Madison River continues to flow in a north direction to join the Jefferson and Gallatin Rivers at Three Forks and to form the north oriented Missouri River. The Gravelly Range is located west of the north oriented Madison River and the Madison Range is located to the east. The Gallatin River originates in the northwest corner of Yellowstone National Park near the southeast corner of figure 2 and flows in a northwest direction to the south-to-north oriented highway location in the east half of figure 2. From the Yellowstone National Park northwest corner to the north edge of figure 2 the highway is located in the north oriented Gallatin River valley. The Madison Range is located west of the Gallatin River while the Gallatin Range is to the east. Named Madison River tributaries seen in figure 2 include north and northwest oriented Jack Creek, west and north-northwest oriented Bear Creek, and north-northwest, west-southwest, and west oriented Indian Creek. The unlabeled east oriented stream flowing from Big Sky to the Gallatin River is the West Fork Gallatin River and has a North Fork, Middle Fork, and South Fork. Other named Gallatin River tributaries in the Madison Range include southeast and northeast oriented Buck Creek and northeast and east oriented Taylor Fork (Taylor Creek on more detailed maps). East of the Gallatin River and the Gallatin Range the Yellowstone River flows in a northwest direction from the east edge of figure 2 (near southeast corner) to Miner, Montana and then turns to flow in a north-northeast direction to Livingston, Montana and then to the northeast corner of figure 2. West of the Madison River and the Gravelly Range the Ruby River flows in a north and northwest direction from the south edge of figure 2 to near Twin Bridges, Montana (near northwest corner of figure 2) where it joins the north-northeast oriented Beaverhead River and northeast oriented Big Hole River to form the north-northeast oriented Jefferson River, which flows to the north edge of figure 2 (near northwest corner).

Jack Creek-Middle Fork West Fork Gallatin River drainage divide area

Figure 3: Jack Creek-Middle Fork West Fork Gallatin 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 Jack Creek-Middle Fork West Fork Gallatin River drainage divide area. The Gallatin River flows in a north and northeast direction from the south edge of figure 3 to the east center edge of figure 3. The West Fork Gallatin River flows in an east direction through Big Sky Mountain Village to join the Gallatin River at the point where the Gallatin River turns from flowing in a north direction to flowing in a northeast direction. The North Fork West Fork Gallatin River originates at Bear Basin (near north center edge of figure 3) and flows in a south-southeast direction to join the Middle Fork West Fork west of Big Sky Mountain Village. The Middle Fork West Fork Gallatin River flows in a southeast direction from Big Sky Meadow Village to join the North Fork. The South Fork West Fork Gallatin flows in an east direction across the south center region of figure 3 and then turns to flow in a northeast direction to join the West Fork Gallatin River near Big Sky Mountain Village. Jack Creek is the northwest oriented stream originating north and west of Big Sky Meadow Village and flowing to the west edge of figure 3 (near northwest corner). The South Fork Jack Creek flows in a north direction west of Lone Mountain to join northwest oriented Jack Creek near the northwest corner of figure 3. West and north of figure 3 Jack Creek joins the north oriented Madison River. Note how the northwest oriented Jack Creek valley and southeast oriented Middle Fork West Fork Gallatin River valley are on the same alignments and are also linked by a northwest-to-southeast oriented through valley. The map contour interval for figure 3 is 50 meters and the through valley floor elevation at the drainage divide is between 2350 and 2400 meters. Lone Mountain to the southwest rises to more than 3350 meters while a spot elevation of 3190 meters can be seen in the Spanish Peaks area between the Beehive and the Bear Basins to the north. These elevations suggest the through valley may be as much as 800 meters deep. The through valley is a water-eroded feature and was eroded by a southeast oriented flood flow channel that diverged from a south oriented flood flow channel on the present day north oriented Madison River alignment (north and west of figure 3) and which then converged with a southwest oriented flood flow channel on the present day northeast oriented Gallatin River alignment (seen near east edge of figure 3) to form a south oriented flood flow channel on the present day north oriented Gallatin River alignment (seen near southeast corner of figure 3). At that time the Madison Range was emerging as crustal warping raised the region and as flood flow channels eroded deeper and deeper valleys into the rising mountain mass. Eventually the southeast oriented flood flow channel across the region in figure 3 was beheaded when the flood flow channel on the Madison River alignment beheaded the southeast oriented flood flow channel. Floodwaters on the northwest end of the beheaded flood flow channel reversed flow direction to create the northwest oriented Jack Creek drainage route.

Detailed map of Jack Creek-Middle Fork West Fork Gallatin River drainage divide area

Figure 4: Detailed map of Jack Creek-Middle Fork WEst Fork Gallatin River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 provides a detailed topographic map of the Jack Creek-Middle Fork West Fork Gallatin River drainage divide area seen is less detail in figure 3. The Middle Fork West Fork Gallatin River originates in section 24 and flows in an east direction to section 19 where it turns to flow in southeast direction past Big Sky Meadow Village to the southeast corner of figure 4. Jack Creek originates at Ulerys Lake and flows in a northwest direction to the northwest corner of figure 4. A northwest-to-southeast oriented through valley can be seen in the northeast corner of section 24 linking the northwest oriented Jack Creek valley with the southeast oriented Middle Fork West Fork Gallatin River valley. The map contour interval for figure 4 is 40 feet and the through valley floor elevation at the drainage divide is shown as 7818 feet. Lone Mountain near the south edge of figure 4 rises to 11,182 feet. The drainage divide north of the through valley rises to about 9200 feet near the north edge of figure 4, but north of figure 4 in Spanish Peaks area elevations it rises to 10,487 feet. Based on elevations seen in figure 4 the through valley is approximately 1400 feet deep, although based on the unseen Spanish Peaks elevation the through valley may almost 2700 feet deep. The through valley is a water-eroded feature and was eroded by a southeast oriented flood flow channel into an emerging mountain mass. Initially the Madison Mountains did not stand high above surrounding regions and floodwaters could freely flow across the region. As the Madison Mountains emerged deep south-oriented flood flow channels eroded headward along the present day north oriented Madison River and Gallatin River alignments with diverging and converging flood flow channels crossing the emerging Madison Range. At first the diverging and converging southeast oriented flood flow channel on the Jack Creek-Middle Fork West Fork Gallatin River alignment was able to erode its valley fast enough to keep up with the emerging Madison Range. However in time the emerging Madison Range won the battle and the south oriented flood flow channel on the Madison River alignment beheaded the southeast oriented flood flow channel. The result was a reversal of flood flow on the northwest end of the beheaded flood flow channel to create the northwest oriented Jack Creek drainage route seen in figure 4 today.

South Fork Jack Creek-South Fork West Fork Gallatin River drainage divide area

Figure 5: South Fork Jack Creek-South Fork West Fork Gallatin River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the South Fork Jack Creek-South Fork West Fork Gallatin River drainage divide area west of figure 3 and includes a significant overlap area with figure 3. The Madison River valley is located along the west edge of figure 5 with the north oriented Madison River located west of figure 5. Big Sky Meadow Village is located near the east center edge of figure 5 and Middle Fork West Fork Gallatin River flows in a southeast direction to the east center edge of figure 5. The South Fork West Fork Gallatin River originates between Cedar Mountain and Pioneer and flows in a northeast, east, southeast, and east direction (south of Lone Mountain) to the east edge of figure 5 (near southeast corner). Jack Creek originates north and west of Big Sky Meadow Village and flows in northwest and west-northwest direction to the north edge of figure 5 and joins the north oriented Madison River north and west of figure 5. The South Fork Jack Creek flows in a north direction across the center region of figure 5 (between Fan Mountain and Lone Mountain) to join Jack Creek south of the north center edge of figure 5. Cedar Creek originates at Cedar Lake (near Cedar Mountain, which is near the south edge of figure 5) and flows in a north direction and then turns to flow in a west and northwest direction to the Cedar Creek Alluvial Fan. Note how the north oriented Jack Creek valley and the north and east oriented Cedar Creek valley are linked by a deep through valley. The map contour interval for figure 5 is 50 meters and the through valley floor elevation at the drainage divide is between 2300 and 2350 meters. Fan Mountain to the north rises to 3142 meters, Cedar Mountain to the south reaches 3282 meters, and Lone Mountain to the east exceeds 3350 meters suggesting the through valley may be as much as 800 meters deep. Note also the through valley linking the north oriented Jack Creek valley with the east, southeast, and east oriented South Fork West Fork Gallatin River valley. The through valley elevation at the drainage divide is between 2650 and 2700 meters, suggesting the through valley may be as much as 500 meters deep. These and other similar through valleys seen in figure 5 provide evidence of former diverging and converging south and southeast oriented flood flow channels. The north oriented South Fork Jack Creek alignment was used by south oriented flood flow moving to the South Fork West Fork Gallatin River alignment. However, headward erosion of a deeper south oriented flood flow channel on the present day north oriented Madison River alignment beheaded a southeast oriented flood flow channel on the present day northwest oriented Cedar Creek alignment. Floodwaters on the northwest end of the beheaded flood flow channel reversed flow direction to create the northwest oriented Cedar Creek drainage route and captured the south oriented flood flow on the Jack Creek alignment (which then eroded the west oriented Cedar Creek valley south of Fan Mountain. The north oriented Cedar Creek segment also originated as a south oriented flood flow channel and was beheaded and reversed to create the present day north oriented drainage route and provides evidence south oriented flood flow once moved on a surface equivalent in elevation to the top of Cedar Mountain (although the evidence is subtle—there is a notch between two high points south of Cedar Lake).

Detailed map of South Fork Jack Creek-South Fork West Fork Gallatin River drainage divide area

Figure 6: Detailed map of South Fork Jack Creek-South Fork West Fork Gallatin River 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 South Fork Jack Creek-South Fork West Fork Gallatin River drainage divide area seen in less detail in figure 5. Lone Mountain is the high mountain east of the center of figure 6. Fan Mountain is located in the northwest quadrant of figure 6. Cedar Creek flows in a north and north-northeast direction from the south edge of figure 6 (near southwest corner) into section 29 where it makes an abrupt turn to flow in a west direction to the west edge of figure 6 (north of center). The South Fork Jack Creek flows in a north direction from the west half of section 5 near the south edge of figure 6 to the north edge of figure 6 (west of center). The South Fork West Fork Gallatin River flows in a northeast direction from the south edge of figure 6 (in southeast quadrant of section 4 and then turns in section 3 to flow in an east direction to section 1 where it turns to flow in a southeast to the south edge of figure 6. The deep through valley linking the north oriented South Fork Jack Creek valley with the west oriented Cedar Creek valley is located in section 29 west of Lone Mountain. The map contour interval for figure 6 is 40 feet and the through valley floor elevation at the drainage divide is between 7600 and 7640 feet. Fan Mountain to the north rises to 10,307 feet, Cedar Mountain (south of figure 6) rises to 10,768 feet, and Lone Mountain to the east reaches 11,182 feet suggesting the through valley may be as much as 2600 feet deep. Near the corner of sections 3, 4, 33, and 34 is a another through valley linking a northwest oriented South Fork Jack Creek tributary valley with the east and southeast oriented South Fork West Fork Gallatin River valley. The through valley floor elevation at the drainage divide is between 7960 and 8000 feet suggesting the through valley may be as much as 2700 feet (the through valley is located between Lone Mountain and Cedar Mountain). These through valleys and other through valleys (or mountain passes) seen in figure 6 are water eroded features and were initiated by south and southeast oriented flood flow channels prior to the emergence of the Madison Range. At that time floodwaters flowed on a surface equivalent in elevation to the tops of the high mountains seen in figure 6. Since that time deep south-oriented valleys eroded headward into the rising Madison Range mountain mass beheading and reversing the south and southeast oriented flood flow channels to create the north, northwest, and west oriented drainage routes seen today.

Middle Fork Bear Creek-McAtee Creek drainage divide area

Figure 7: Middle Fork Bear Creek-McAtee Creek drainage divide. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Middle Fork Bear Creek-McAtee Creek drainage divide area south of figure 5 and includes a significant overlap area with figure 5. The Madison River can just barely be seen in the southwest corner of figure 7 and flows in a north-northwest direction west of figure 7. The South Fork West Fork Gallatin River is located in the northeast quadrant of figure 7 and flows in a northeast, east, southeast and east direction to the east edge of figure 7. Named tributaries include northeast oriented Muddy Creek, north-northeast and north oriented Third Yellow Mule Creek, and north and north-northeast oriented Second Yellow Mule Creek. Northeast oriented headwaters of First Yellow Mule Creek flow to the east center edge of figure 7. South of the north oriented Yellow Mule Creek headwaters is McAtee Basin where McAtee Creek originates as a southeast oriented stream, but then turns to flow in a south-southwest and south-southwest direction to join northwest, southwest, and west oriented Indian Creek (not labeled in figure 7) west of Circle Mountain, which south of figure 7 joins the north oriented Madison River. Cougar Creek is a southeast oriented McAtee Creek tributary located between McAtee Basin and Sphinx Mountain. McAtee Creek is not the only barbed tributary seen in figure 7. The North Fork (Bear) Creek originates on the southeast side of Cedar Mountain and flows in a southwest direction to join west oriented Middle Fork and southwest and northwest oriented Trail Creek at the Madison River valley margin to form northwest oriented Bear Creek (not labeled in figure 7), which joins the Madison River west of figure 7. Cameron Creek is a south oriented North Fork Bear Creek tributary. Note the several streams north of Bear Creek flowing in southwest directions to enter the Madison River valley and then turning to flow in a northwest direction once in the valley. These south oriented streams provide evidence of south oriented flood flow channels that crossed the region prior to the massive flood flow reversal that created the north oriented Madison River drainage system. Numerous through valleys or mountain passes can be seen in figure 7 providing further evidence of diverging and converging flood flow channels that crossed the region as the Madison Mountains began to emerge. For example, north and east of Sphinx Mountain a through valley or pass links the west oriented Middle Fork Bear Creek valley with the southeast oriented Cougar Creek valley. The map contour interval for figure 7 is 50 meters and the through valley floor elevation at the drainage divide is between 2700 and 2750 meters. Sphinx Mountain rises to 3375 meters. High elevations to the north vary from 3282 meters at Cedar Mountain to 3005 meters at Pioneer Mountain and more than 3000 meters on the ridge between the through valley and McAtee Basin. These elevations suggest the through valley could be anywhere from 250 to 500 meters deep. The through valley is a water-eroded water valley and was eroded by southeast oriented flood flow prior to emergence of the Madison Range and to headward erosion of a deep south oriented flood flow channel on the present day north oriented Madison River valley alignment.

Detailed map of Middle Fork Bear Creek-Cougar Creek drainage divide area

Figure 8: Detailed map of Middle Fork Bear Creek-Cougar Creek 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 Middle Fork Bear Creek-Cougar Creek drainage divide area seen in less detail in figure 7. Sphinx Mountain is located in the southwest quadrant of figure 8. The Middle Fork Bear Creek originates at the confluence of north and south oriented tributaries in section 3 (north and east of Sphinx Mountain) and flows in a west-northwest direction to section 32 where it turns to flow in a west-southwest direction to the west center edge of figure 8. Cougar Creek originates along the west edge of section 2 and flows in a southeast direction to join south oriented McAtee Creek in section 12. McAtee Creek originates in section 35 and flows in a southeast direction through McAtee Basin to the northeast quadrant of section 1 where it turns to flow in a south direction to the south edge of figure 8 (east half). Note the northwest-to-southeast oriented through valley linking the west-northwest oriented Middle Fork Bear Creek valley with the southeast oriented Cougar Creek valley. The map contour interval for figure 8 is 40 feet and the through valley floor elevation at the drainage divide is between 9000 and 9040 feet. A second intriguing through valley can be seen to the north along the line separating section 35 from section 34. This northern through valley links the valley of a west and south oriented Middle Fork Bear Creek headwaters stream with southeast oriented McAtee Creek headwaters valley. The floor elevation of this northern through valley at the drainage divide is between 9240 and 9280 feet. Sphinx Mountain to the southwest rises to 10,828 feet, the ridge between the two through valleys rises to 9983 feet, and Pioneer Mountain north of figure 8 rises to 9859 feet, suggesting the through valleys may be from 600 to 800 feet deep. Other similar through valleys can be seen crossing most other drainage divides seen in figure 8. The through valleys were eroded by southeast oriented flood flow channels prior to and during emergence of the Madison Range and before headward erosion of a deep south oriented flood flow channel on the alignment of the present day north oriented Madison River valley west of figure 8. Elevations of these through valleys suggest there has been significant regional uplift since flood flow across the region ended.

McAtee Creek-Taylor Creek drainage divide area

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

Figure 9 illustrates the McAtee Creek-Taylor Creek drainage divide area south and east of figure 7 and includes a significant overlap area with figure 7. Sphinx Mountain is located near the northwest corner of figure 9. McAtee Basin is located north and east of Sphinx Mountain and McAtee Creek flows in a southeast and south-southwest direction from McAtee Basin to join northwest, southwest, and west-southwest oriented Indian Creek west of Circle Mountain. West of the northwest oriented Indian Creek segment is north-to-south oriented Shedhorn Mountain and west of Shedhorn Mountain is north-northwest oriented Shedhorn Creek, which flows to west-southwest oriented Indian Creek. West of Shedhorn Creek is No Man Ridge and west on No Man Ridge is north-northwest oriented No Man Creek. The highway near the east edge of figure 9 is located in the north-northwest and north-northeast oriented Gallatin River valley. Taylor Creek flows in a northeast direction from the south edge of figure 9 (west of center) and then turns to flow in an east, east-southeast, east, and east-northeast direction to join the north oriented Gallatin River north of the southeast corner of figure 9.  Note southeast oriented tributaries joining Taylor including Cache Creek, Left Fork Creek and its tributary Deadhorse Creek, and Meadow Creek. A northwest-to-southeast oriented through valley links the northwest oriented Indian Creek valley with the southeast oriented Cache Creek valley. The map contour interval for figure 9 is 50 meters and the through valley floor elevation at the drainage divide is between 2550 and 2600 meters. Elevations immediately to the northeast rise to more than 2800 meters while Shedhorn Mountain to the west rises to more than 3000 meters suggesting through valley is at least 200 meters deep. The through valley provides evidence of a southeast oriented flood flow channel that once moved southeast oriented floodwaters to the present day Gallatin River valley. It is possible the flood flow reversals in the Gallatin and Madison River valleys did not take place simultaneously. If so it is possible floodwaters were reversed first in the Gallatin River valley and for a time southeast oriented floodwaters diverging from a south oriented flood flow channel on the present day north oriented Madison River alignment flowed to the “east” oriented Taylor Creek valley and then made a U-turn to flow in a north direction on the Gallatin River alignment. If so, the Madison Range at that time was still emerging and the deep Madison River valley to the west had yet to be eroded or otherwise formed.

Detailed map of Indian Creek-Taylor Creek drainage divide area

Figure 10: Detailed map of Indian Creek-Taylor 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 Indian Creek-Taylor Creek drainage divide area seen in less detail in figure 9. Indian Creek is the northwest oriented stream flowing to the northwest corner of figure 10. North and west of figure 10 Indian Creek turns to flow in a southwest and then west-southwest direction to eventually reach the north oriented Madison River. Taylor Creek flows in an east direction near the south edge of the southeast quadrant of figure 10 and east of figure 10 joins the north oriented Gallatin River. Cache Creek is a southeast oriented stream joining Taylor Creek near the south center edge of figure 10. A through valley or pass in the north half of section 31 and northwest corner of section 32 links the northwest oriented Indian Creek valley with the southeast oriented Cache Creek valley. The map contour interval for figure 10 is 40 feet and the lowest elevations along the through valley drainage divide are between 8400 and 8440 feet. Elevations in the southeast quadrant of section 29 rise to 9346 feet and Shedhorn Mountain along the west edge of figure 10 rises to 9837 feet (this highest elevation is not seen in figure 10). These elevations suggest the through valley is at least 900 feet deep. The through valley was eroded by southeast oriented flood flow moving from the present day northwest oriented Indian Creek valley to the southeast oriented Cache Creek valley. At that time the Madison Range was still emerging and the deep Madison River valley to the west did not exist. The southeast oriented flood flow channel was beheaded by headward erosion of a much deeper southwest oriented flood flow channel on the present day southwest oriented Indian Creek-McAtee Creek alignment north and west of figure 10. That southwest oriented flood flow channel was probably eroding headward from a deep south oriented flood flow channel on the present day north oriented Madison River alignment. Floodwaters on the northwest end of the beheaded southeast oriented flood flow channel reversed flow direction to create the northwest oriented Indian Creek drainage route seen today.

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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