Shields River-Gallatin River drainage divide area landform origins, Gallatin and Park Counties, Montana, USA

Authors

Abstract:

Topographic map interpretation methods are used to determine erosional landform origins in the Shields River drainage divide area located in Gallatin and Park Counties, Montana. The Shields River is a south-southeast oriented tributary to the east and northeast oriented Yellowstone River and flows in a broad valley east of the Bridger Range and west of Crazy Mountains. The Gallatin River flows in a north and northwest oriented direction to join the north oriented Madison River and northeast oriented Jefferson River to form the north oriented Missouri River. Dry Creek is a south oriented tributary which flows in a broad valley west of the Bridger Range and which joins the northwest and west oriented East Gallatin River, which in turn flows to the Gallatin River. The north-south Bridger Range is a high mountain range located between the south oriented Shields River drainage basin and the north oriented Gallatin River drainage basin. Multiple through valleys, including deep mountain passes across the high Bridger Range, cross the present day Shields River-Gallatin River drainage divide and provide evidence of what was once a large-scale south-oriented anastomosing channel complex, which moved immense floods across the entire region. Flood waters flowed across the Bridger Range as the mountains were rising and numerous barbed tributaries provide evidence of flood flow reversals as crustal warping and headward erosion of the deep east and northeast oriented Yellowstone River valley (south and east of study region) forced massive flood flow reversals east of the Bridger Range and as crustal warping and headward erosion of the deep northeast and east oriented Missouri River valley (north and west of study region) forced an even larger flood flow reversal west of the Bridger Range. Based on evidence from outside the study region flood waters were derived from a rapidly melting thick North American ice sheet and were flowing in south and southeast directions into and across Montana as present day Montana mountain ranges were beginning to emerge and continued to flow across Montana as the mountain ranges emerged.

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 Missouri River 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 available at this site may be found by selecting desired Missouri River tributaries and/or states from this essay’s sidebar category list.

Introduction:

  • The purpose of this essay is to use topographic map interpretation methods to explore the Shields River-Gallatin River drainage divide area erosional landform origins in Gallatin and Park Counties, Montana, USA. Map interpretation methods can be used to unravel many geomorphic events leading up to formation of present-day drainage routes and development of other erosional 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 providing 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 essays in the Missouri River drainage basin landform origins research project 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 Shields River-Gallatin River drainage divide area landform evidence in Gallatin and Park Counties, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm (see essay listed on header). This essay is included in the Missouri River drainage basin landform origins research project essay collection.

Shields River-Gallatin River drainage divide area location map

Figure 1: Shields 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 Shields River-Yellowstone River divide area location map and shows a region in southern Montana with a strip from the Wyoming northwest corner seen along the east half of the figure 1 south edge and bits of Idaho seen along the west half of the figure 1 south edge. Yellowstone National Park is located primarily in the Wyoming northwest corner and is labeled near the figure 1 south center edge. The Yellowstone River flows in a northwest direction to Gardiner, Montana (along Yellowstone National Park north edge) and then for a short distance into Montana before turning to flow in a north-northeast direction to near Livingston. Near Livingston the Yellowstone River turns to flow in a northeast direction to Big Timber and then in an east-southeast and east-northeast direction to the figure 1 east center edge. East of figure 1 the Yellowstone River flows in a northeast direction to join the Missouri River near the Montana-North Dakota border. North of Livingston are the Crazy Mountains. The unlabeled stream flowing in a southwest direction from near Loco Mountain to Wilsall and then in a south-southeast direction through Clyde Park to join the Yellowstone River is the Shields River. Flathead Creek is an east-northeast oriented tributary joining the Shields River near Wilsall, but is not shown in figure 1. Note the south-southeast oriented tributary originating near Ringling and joining the Shields River near Wilsall and how north of Ringling there is a north-northwest oriented drainage route between the Big Belt Mountains and the Little Belt Mountains. That north-northwest oriented river is the Smith River, which north of the figure 1 map area joins the Missouri River. Returning to the Yellowstone National Park area the Gallatin River flows in a north-northwest direction between the Gallatin Range and the Madison Range, past the towns of Big Sky and Gallatin Gateway to the town of Three Forks where it joins the north-oriented Madison River and the north-northeast, east, and northeast oriented Jefferson River to form the north and north-northwest oriented Missouri River. North of the figure 1 map area the Missouri River turns to flow in a northeast direction and then after a jog to the south flows in a more of an east direction across Montana. The East Gallatin River flows in a northwest from near Bozeman to join the Gallatin River near Manhattan with only the northwest end shown in figure 1 (a north-northwest and north oriented tributary is shown south Belgrade). East of Bozeman and extending from the Big Belt Mountains south end to the Gallatin Range north end is the Bridger Range, which is not labeled on figure 1, although which is an important mountain range in this essay. The Shields River-Gallatin River drainage divide area investigated in this essay is located south and west of east-northeast oriented Flathead Creek and the south-southeast oriented Shields River and north and east of the East Gallatin River and includes much of the high Bridger Range. The region immediately to the north is described in the Sixteenmile Creek-Shields River drainage divide area landform origins, central Montana essay and the region to the west is described in the Sixteenmile Creek-Gallatin River drainage divide area landform origins Gallatin County, Montana essay.
  • Drainage routes in the figure 1 map region (and a much larger region) developed during immense south and southeast-oriented floods which flowed across the entire region. At that time the mountain ranges did not stand high above the surrounding basins and plains and flood waters could freely flow across the region. Flood waters responsible for eroding the Shields River-Gallatin River drainage divide area (and much of the figure 1 map region) were derived from western Alberta and eastern British Columbia, which at time was evolving into western rim of a deep “hole’ in which a rapidly melting thick North American ice sheet was located. The Missouri River drainage basin in Montana and northern Wyoming is the deep “hole’s” deeply eroded southwest wall. The deep “hole” did not exist when the ice sheet first formed, but was created by deep glacial erosion (under the ice sheet) and by crustal warping that raised mountain ranges and high plateau areas along the ice sheet margins and elsewhere on the North American continent. Crustal warping took place as the thick ice sheet melted and mountain ranges were raised as immense south and southeast-oriented melt water floods flowed across them. Massive south and southeast-oriented melt water floods flowed from the ice sheet’s western margin across Montana, Wyoming, and Colorado into New Mexico and Texas along routes roughly corresponding with the present day east-west continental divide while the Rocky Mountains were being uplifted (from south to north). At the same time deep valleys eroded headward from the Gulf of Mexico in the east and the Pacific Ocean in the west to capture the immense south and southeast-oriented melt water floods and to carve the east-west continental divide. In time a combination of deep “hole” formation and of ice sheet melting created a situation where the south and southeast-oriented ice-marginal melt water floods were flowing at elevations higher than deep “hole” space being opened up by the ice sheet melting (especially along the ice sheet’s southern margin). This new situation changed the melt water flood flow directions as deep northeast and east-oriented valleys eroded headward from the newly opened up deep “hole” space into Montana and northern Wyoming to capture the south and southeast-oriented melt water floods. These deep valleys and their tributary valleys eroded headward in sequence from the southeast to the northwest.
  • Headward erosion of the deep northeast-oriented Yellowstone River valley occurred prior to headward erosion of the deep east oriented Missouri River valley, which beheaded the south and southeast-oriented flood flow moving to what was then the newly eroded Yellowstone River valley. Of importance to this essay the deep Yellowstone River eroded headward to the Livingston region and captured a major south-oriented flood flow channel moving flood waters between what were then the emerging Bridger Range and the Crazy Mountains (and between the Big Belt Mountains and Little Belt Mountains further to the north). Prior to being captured much of the south-oriented flood flow was continuing south along a flood flow channel roughly corresponding with the present day northwest, and north-northeast oriented Yellowstone River valley alignment (south of Livingston), although using a much shallower flood flow channel. Headward erosion of the much deeper east and northeast-oriented Yellowstone River valley beheaded the south-oriented flood flow channel near Livingston and flood waters on the north end of the beheaded flood flow channel reversed flow direction to erode the deep northwest and north-northeast oriented Yellowstone River valley seen today. Uplift of the Yellowstone Plateau, which underlies the Yellowstone National Park region, probably greatly aided in this massive flood flow reversal. Headward erosion of the deep Missouri River valley (north of the figure 1 map area) was responsible for even larger flood flow reversals. First deep Missouri River valley headward erosion beheaded and reversed the south-southeast oriented flood flow channel between the Big Belt Mountains and the Little Belt Mountains to erode the north-northwest oriented Smith River valley. Next deep Missouri River valley headward erosion beheaded and reversed a major south-southeast oriented flood flow channel west to the Big Belt Mountains to erode the north and north-northwest oriented Missouri River valley seen in figure 1. Prior to being beheaded and reversed the south-southeast flood flow channel west of the Big Belt Mountains split in the Three Forks region to form three diverging south-oriented flood flow channels moving flood waters to what was probably the actively eroding and deep west-oriented Snake River valley (which at that time may have reached the area south of the figure 1 south center). Reversal of flood flow in the present day north-northwest oriented Missouri River valley also reversed flood flow in each of these diverging flood flow channels so as to erode three north-oriented river valleys, with the north-northwest oriented Gallatin River valley being the easternmost one.

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

Figure 2: Detailed location map for Shields River-Gallatin River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 
  • Figure 2 provides a detailed location map for the Shields River-Gallatin River drainage divide area. Green shaded areas are National Forest lands and are generally located in mountainous regions. County boundaries are shown and Gallatin and Park Counties are labeled. The green shaded area in the figure 2 northeast corner is located in the Crazy Mountains. The green shaded area north of Bozeman is in the Bridger Range. The green shaded area in the figure 2 southeast corner is located in the Absaroka Range and the green shaded area south of Bozeman is in the Gallatin Range. The Yellowstone River flows in a north direction from the figure 2 south edge between the Absaroka Range and Gallatin Range to Livingston and then turns to flow in a northeast direction to Mission and then in an east direction to the figure 2 east edge (south half). The Shields River originates in the Crazy Mountains north of the figure 2 northeast corner and flows in a south-southwest and south direction to Wilsall and then in a south-southeast direction to Clyde Park and then to join the Yellowstone River near Mission. Flathead Creek is an east-northeast oriented tributary originating in the Bridger Ranger Range and joining the Shields River near Wilsall. Other labeled east-oriented Shields River tributaries originating in the Bridger Range include Brackett Creek and Bangtail Creek. The Gallatin River flows in a north direction from the figure 2 south edge (near Spanish Breaks) to Bozeman Hot Springs and then near Manhattan turns to flow in a west-northwest direction to Three Forks where it joins the north-oriented Madison River and northeast-oriented Jefferson River to form the north-northeast oriented Missouri River seen north of Three Forks. The East Gallatin River flows in a northwest and west direction from Bozeman to join the Gallatin River near Logan. Bridger Creek is a south and west oriented tributary flowing from the Bridger Range east side to join the north-northwest oriented East Gallatin River north of Bozeman as a barbed tributary. Jackson Creek is a southwest-oriented East Gallatin River tributary located east of Bridger Creek (more detailed maps show Jackson Creek joining other streams before reaching the East Gallatin River). Between the Bridger Range and the Missouri River in the figure 2 northwest quadrant are the Horseshoe Hills. The lowland between the Horseshoe Hills and the Bridger Range is drained by south-oriented Dry Creek, which flows to the East Gallatin River. Several southwest oriented Dry Creek tributaries originate in the Bridger Range and Bear Creek is the southwest oriented tributary flowing from the Bridger Range to the northwest-oriented East Gallatin River as a barbed tributary. South-oriented streams west of the Bridger Range are flowing to what today is a north-oriented drainage system and provide evidence of a previous south-oriented drainage system that existed prior to the drainage reversal that created the north-oriented Gallatin-Missouri River drainage basin. Note also north-oriented headwaters and tributaries to some of the east-oriented Shields River tributaries. Those north-oriented headwaters and tributaries are flowing in valleys eroded by reversals of flow on the north ends of beheaded south-oriented flood flow channels (with the flood flow reversals probably also aided by Bridger Range uplift, which occurred as flood water flowed in a south direction across the rising mountains).

 Flathead Creek-Pass Creek drainage divide area

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

 

  • Figure 3 illustrates the Flathead Creek-Pass Creek drainage divide area and the Bridger Range northern end. The Bridger Range is the high mountain ridge extending in a south-southeast direction from the figure 3 north edge (west of center) to the figure 3 south edge (east of center). Flathead Pass is a labeled deep though valley eroded across the Bridger Range in the figure 3 north half. Directly east of Flathead Pass are north-oriented headwaters of north and northwest oriented South Fork Sixteenmile Creek, which flows to west-oriented Sixteenmile Creek, which in turn flows to the north oriented Missouri River (significantly west of the figure 3 map area).  Just east of the north oriented South Fork Sixteenmile Creek headwaters are east oriented headwaters of east-northeast oriented Flathead Creek, which flows to the south oriented Shields River east of the figure 3 map area. The west side of Flathead Pass is drained by west-southwest oriented Pass Creek, which flows to south-oriented Dry Creek west of the figure 3 map area. West and south of the figure 3 map area Dry Creek flows to the west oriented East Gallatin River. The figure 3 map contour interval is 50 meters. An elevation for Flathead Pass is not given, but based on the contour lines it is between 2150 and 2200 meters. Bridger Range elevations to the north of Flathead Pass rise to more than 2550 meters and south of Flathead Pass the elevations are even higher. In other words Flathead Pass is at least 350 meters deep and may be deeper. Flathead Pass is a water eroded feature and was eroded by west-southwest oriented flood flow moving across what must have been a rising Bridger Range mountain mass. The flood flow channel moving water through Flathead Pass apparently diverged from a larger south-oriented flood flow channel on the Smith River-Shields River valley alignment and converged with a larger south-oriented flood flow channel on the Dry Creek-Gallatin River valley alignment. In addition a southeast and south oriented flood flow channel on the present day north-oriented South Fork Sixteenmile Creek valley alignment supplied flood waters to the Flathead Pass flood flow channel. For a time flood water erosion was able to erode the deep Flathead Pass valley fast enough to maintain its course as the Bridger Range rose, however eventually Bridger Range uplift forced a reversal of flood flow that eroded the east-northeast oriented Flathead Creek valley, which captured the southeast and south oriented flood flow moving on the South Fork Sixteenmile Creek alignment. Eventually Sixteenmile Creek valley headward erosion (north of figure 3) beheaded the southeast and south oriented flood flow east of the Bridger Range. Flood waters on the north and northwest end of the beheaded flood channel reversed flow direction to erode the north and northwest oriented South Fork Sixteenmile Creek valley.

Flathead Creek-Brackett Creek drainage divide area

Figure 4: Flathead Creek-Brackett Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 4 illustrates the Flathead Creek-Brackett Creek drainage divide area south and east of the figure 3 map area and includes overlap areas with figure 3. Flathead Pass is located near the figure 4 northwest corner. Flathead Creek flows in an east-northeast direction from the Bridger Range east flank to the figure 4 north edge (east half – near the Park County-Gallatin County border). Battle Ridge Pass is a labeled pass or through valley just west of the figure 4 south center area. Cache Creek flows in an east-southeast direction toward Battle Ridge Pass and then just north of Battle Ridge Pass turns to flow in a north-northeast direction to join Flathead Creek near the figure 4 north center (a short distance north of Sedan). Brackett Creek is formed a short distance south of Battle Ridge Pass at the confluence of its southeast-oriented North Fork, east-northeast oriented Middle Fork, and northeast and north oriented South Fork and then flows in a an east direction (with a northeast jog) to the figure 4 east edge (south half) and east of figure 4 joins the south-southeast Shields River (near Clyde Park). Battle Ridge is a high southwest to northeast oriented ridge, probably associated with the Bridger Range structure, which extends from the Battle Ridge Pass area to the figure 4 east edge. The figure 4 map contour interval is again 50 meters and elevations along the Battle Ridge crest reach to slightly above 2250 meters while elevations greater than 2900 meters can be found along the Bridge Range crest west of Battle Ridge Pass. Based on the contour lines the Battle Ridge Pass elevation at the drainage divide is between 1900 and 1950 meters, meaning Battle Ridge Pass is a 300-meter plus deep valley linking the north-northeast oriented Cache Creek valley with the north-oriented South Fork Brackett Creek valley and the east-oriented Brackett Creek valley. The Battle Ridge Pass valley was eroded by south-oriented flood flow moving to the south-oriented Bridger Creek headwaters located south of the north-oriented South Fork Brackett Creek valley (seen in figure 5 below). The south-oriented flood waters were diverging from the south-southeast Shields River flood flow channel east of the figure 4 map area and converging with south-oriented flood flow channel moving on the South Fork Sixteenmile Creek alignment to reach Battle Ridge Pass and the south-oriented Bridger Creek valley (which eventually drains to the Gallatin River). Bridger Range uplift (including Battle Ridge uplift) as flood waters were flowing across the figure 4 map region probably combined with headward erosion of a deeper south-southeast oriented Shields River valley (east of figure 4 and probably associated with headward erosion of the deep east and northeast oriented Yellowstone River valley into the region south and east of the figure 4 map area) caused a flood flow reversal north of Battle Ridge that eroded the north-northeast oriented Cache Creek valley.

Brackett Creek-Bridger Creek drainage divide area

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

 

  • Figure 5 illustrates the Brackett Creek-Bridger Creek drainage divide area south and west of the figure 4 map area and includes overlap areas with figure 4. Battle Ridge Pass is near the figure 5 north center edge. Brackett Creek is formed south of Battle Ridge Pass at the confluence of its southeast-oriented North Fork, east-northeast oriented Middle Fork, and northeast and north oriented South Fork and flows in an east direction to the figure 5 east edge (near northeast corner) and then to the south-southeast oriented Shields River (which flows to the Yellowstone River). Note how the north-oriented South Fork Brackett Creek drains a segment of a large north-south oriented through valley extending from Battle Ridge Pass to the figure 5 south center edge. South of the segment drained by north-oriented South Fork Brackett Creek  the through valley is drained by south-oriented Bridger Creek, which south and west of figure 5 flows to the East Gallatin River. The Bridger Bowl Ski Area is located near the south-oriented Bridger Creek headwaters and Grassy Mountain is a labeled high area east of the Bridger Bowl Ski Area. The figure 5 map contour interval is 50 meters and a spot elevation on Grassy Mountain reads 2323 meters. A spot elevation on the Bridger Range crest to the west reads 2657 meters. The South Fork Brackett Creek-Bridger Creek through valley floor elevation at the drainage divide is between 1850 and 1900 meters meaning the through valley is more than 300 meters deep. The through valley is a water eroded feature and was eroded by south-oriented flood flow moving to what at one time were south-oriented flood flow channels south of figure 5, which probably included south oriented flood flow channels on both the present day north oriented Gallatin and Yellowstone River alignments (south of Bozeman and Livingston respectively). After reversal of flood flow on the Missouri River-Gallatin River alignment the south-oriented flood flow on the Bridger Creek alignment was captured by the northwest oriented East Gallatin River and the north-oriented Missouri River. Headward erosion of a deeper east-oriented Brackett Creek valley from the south-southeast oriented Shields River valley beheaded the south oriented flood flow, with flood water on the north end of the beheaded flood flow channel reversing flow direction to erode the north-oriented South Fork Brackett Creek valley. Note also the location of Ross Pass just west of the Middle Fork Brackett Creek headwaters. Ross Pass is another deep valley eroded across the high Bridger Range, although it is not as deep as Flathead Pass. The west-southwest oriented stream originating at Ross Pass is Ross Creek, which west of the figure 5 map area flows to the northwest-oriented East Gallatin River.  Figure 6 below provides a detailed topographic map of the Ross Pass area.

Detailed map of Brackett Creek-Ross Creek drainage divide area

Figure 6: Detailed map of Brackett Creek-Ross 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 Brackett Creek-Ross Creek drainage divide area at Ross Pass, which was seen in less detail in figure 5 above. Ross Pass is labeled and is located slightly north and east of the figure 6 center. The east-northeast oriented stream originating just east of Ross Pass is Middle Fork Brackett Creek, which east of the figure 6 map area flows to east-northeast and east oriented Bracket Creek, which in turn flows to the south-southeast oriented Shields River. The west-southwest oriented stream originating just west of Ross Pass is Ross Creek, which west and south of the figure 6 map area flows to the northwest and west oriented East Gallatin River, which in turn flows to the northwest oriented Gallatin River, which then joins the Madison and Jefferson Rivers to form the north-oriented Missouri River. The figure 6 map contour interval is 40 feet and the Ross Pass elevation is given as 7620 feet. Ross Peak to the north rises to more than 8900 feet while the high point near the section 14 north center edge to the south is more than 8600 feet. In other words Ross Pass is approximately 1000 feet deep. Ross Pass like Flathead Pass to the north is a water eroded landform and was eroded by west-southwest oriented flood flow moving across what was then the rising Bridger Range mountain mass. For a time the west-southwest oriented flood flow was able to erode the Ross Pass valley as fast as the mountains rose around it, however eventually the rising mountain mass blocked the west-southwest oriented flood flow and forced the flood water to reverse its flow direction to erode the east-northeast oriented Middle Fork Brackett Creek-Brackett Creek valley. This flood flow reversal may have been aided by headward erosion of the deep Yellowstone River valley into the region east and south of the figure 6 map area and then by headward erosion of a deeper south-southeast oriented Shields River flood flow channel from that newly eroded and deep Yellowstone River valley.

Canyon Creek-Bridger Creek drainage divide area

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

 

  • Figure 7 illustrates the Canyon Creek-Bridger Creek drainage divide area east of the figure 5 map area and includes significant overlap areas with figure 5. Battle Ridge Pass is located near the figure 7 northwest corner. Clyde Park is the town located in the figure 7 northeast corner and the Shields River flows in a south-southeast direction across the figure 7 northeast corner. The Bridger Bowl Ski Area is labeled near the figure 7 west center edge and Bridger Creek flows in a south direction from slightly north of the Ski Area to the figure 7 south edge (near southwest corner). Brackett Creek is formed at the confluence of its three forks south of Battle Ridge Pass and flows in an east-northeast and east-southeast direction to join the Shields River a short distance downstream from Clyde Park. The east-oriented stream (in the figure 7 east half) located south of Brackett Creek is Canyon Creek , which flows to the figure 7 east edge (just north of center) and which then joins the Shields River east of figure 7. South of Canyon Creek in the figure 7 east half is east-oriented Bangtail Creek and south of Bangtail Creek is east-oriented Willows Creek. Note how all of these east-oriented Shields River tributaries have north-northeast oriented tributaries and/or headwaters. East of Grassy Mountain (located east of the Bridger Bowl Ski Area) are north-northeast oriented Skunk Creek and Miles Creek, which both flow to east-oriented Brackett Creek. East of Miles Creek are north-northeast oriented Canyon Creek headwaters and then Grouse Creek and Bridgman Creek. Note how these north-northeast oriented streams are aligned with west-southwest and west oriented Bridger Creek tributaries, which include Olson Creek, White Creek, and Stone Creek. Study of the drainage divide reveals through valleys eroded across it, although some of the through valleys are very shallow and are best seen on more detailed topographic maps. The through valley between the north-northeast oriented Skunk Creek valley and the west-southwest oriented Olson Creek valley is easily seen on figure 7. The figure 7 map contour interval is 50 meters and the through valley elevation at the drainage divide is between 2100 and 2150 meters. Grassy Mountain to the north rises to 2323 meters and higher elevations are located on the ridge to the southeast, meaning the through valley is at least 173 meters deep. The through valley was eroded by southwest oriented flood flow diverging from the south-southeast oriented Shields River flood flow channel moving to the south oriented Bridger Creek flood flow channel, which was supplying flood water to south oriented flood flow channels further to the south. Headward erosion of the much deeper northeast and east oriented Yellowstone River valley into the region and then of a deeper south-southeast oriented Shields River valley (probably aided by Bridger Range uplift occurring at the same time) enabled the east-oriented Willow Creek, Bangtail Creek, and Brackett Creek valleys to erode headward in sequence (from south to north) to capture the diverging south-southwest oriented flood flow routes. Flood waters on north ends of beheaded flood flow routes reversed flow direction to erode the north-northeast oriented tributary and headwaters valleys. The south-southwest oriented flood flow routes were beheaded and reversed one at a time, which meant reversed flood flow on a newly reversed flood flow route could capture yet to be beheaded and reversed flood flow from further west. The capture of such yet to be beheaded flood flow, plus on-going uplift of the Bridger Range, probably helped erode the deep north-northeast oriented tributary and headwaters valleys.

Willow Creek-Jackson Creek drainage divide area

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

 

  • Figure 8 illustrates the Willow Creek-Jackson Creek drainage divide south and slightly east of the figure 7 map area and includes significant overlap areas with figure 7. Bridger Creek flows in a south direction just west of the figure 8 west edge and streams flowing to the figure 8 west edge are Bridger Creek tributaries. Just west of the figure 8 southwest corner Bridger Creek turns to flow in a west direction to join the northwest and west oriented East Gallatin River with water then flowing to the northwest oriented Gallatin River and north oriented Missouri River. Jackson Creek is a southwest oriented stream flowing to the figure 8 south edge in the figure 8 southwest quadrant and south and west of figure 8 joins a northwest-oriented stream to form a west-southwest and northwest oriented East Gallatin River tributary. Northeast of the southwest oriented Jackson Creek headwaters are northeast oriented North and Middle Fork headwaters with the North and Middle Forks joining the northeast-oriented South Fork to form east oriented Willow Creek, which flows to figure 8 east edge (north half) and then to join the south-southeast oriented Shields River. Note how the southwest oriented Jackson Creek headwaters are linked by through valleys with the northeast oriented North and Middle Forks Willow Creek headwaters. The through valleys are not as deep as some seen in earlier figures, but can be seen figure 8. The figure 8 map contour interval is 50 meters and the through valley elevations at the drainage divide are between 2250 and 2300 meters. The hill-top to the southeast is shown as reaching 2354 meters while the hill-top to the northwest is shown as reaching 2427 meters making the through valleys at least 150 meters deep. The through valleys were eroded by southwest oriented flood flow moving initially to what was a south oriented flood flow channel in the present day north oriented Yellowstone River and Gallatin River drainage basins (south of the figure 8 map area). Reversal of flow in the south-oriented flood flow channel on the present day north oriented Madison River-Missouri River valley alignment also reversed flood flow in the south oriented Gallatin River flood flow channel and south-oriented flood flow channels on what are today north-oriented Gallatin River tributary alignments. With that reversal of flood flow the southwest oriented flood flow across the Willow Creek-Jackson Creek drainage divide was captured by the northwest and west oriented East Gallatin River valley and now flows to the north-oriented Missouri River (west of figure 8).

Bridger Creek-Jackson Creek drainage divide area

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

 

 

  • Figure 9 illustrates the Bridger Creek-Jackson Creek drainage divide area south and west of the figure 8 map area and includes significant overlap areas with figure 8. The city of Bozeman, Montana is located just west of the figure 9 southwest quadrant. The East Gallatin River flows in a north-northwest and northwest direction from the figure 9 south edge (south half) to the figure 9 west edge (south of center). Bridger Creek flows in a south-southwest and west direction from the figure 9 north center edge to the figure 9 west center edge and joins the East Gallatin River west of the figure 9 map area. Interstate highway 90 is the major highway located in the figure 9 south half and Bozeman Pass in the figure 9 southeast quadrant is where Interstate 90 crosses the Bridger Range. Jackson Creek flows in a southwest direction a short distance west of Bozeman Pass and north of the figure 9 south center edge joins northwest oriented Meadow Creek to form west-southwest and northwest oriented Rocky Creek, which flows to the north-northwest and northwest oriented East Gallatin River. South of figure 9 northwest oriented Meadow Creek is linked by a deep and well-defined northwest-southeast oriented through valley with southeast and south-southeast oriented Trout Creek, which flows to the north oriented Yellowstone River valley (south and east of figure 9) as a barbed tributary. The northwest-southeast oriented Meadow Creek-Trout Creek through valley was eroded by a southeast oriented flood flow channel that diverged from the west-southwest and northwest oriented Rocky Creek flood flow channel. The east oriented stream flowing along the highway east of Bozeman Pass is Billman Creek, which joins the Yellowstone River at Livingston. Green Mountain is a labeled high point near the figure 9 center. Note the northwest-southeast oriented through valley north and east of Green Mountain linking the Bridger Creek valley with the Jackson Creek valley. Spring Creek drains the northwest end of the through valley and joins south-oriented  Bridger Creek as a barbed tributary while an unnamed southeast-oriented stream drains the through valley southeast end to Jackson Creek. Note how the through valley is aligned with and linked to Bozeman Pass indicating that at one time the south oriented flood flow channel on the Bridger Creek alignment split into two diverging flood flow channels at the present day Spring Creek-Bridger Creek meeting point. One of the diverging flood flow channels moved flood waters in a west direction to the East Gallatin River alignment while the other  diverging flood flow channel moved flood waters in a southeast direction toward Bozeman Pass, where the flood flow channel split into a southeast and east oriented flood flow channel moving flood water across Bozeman Pass to the Yellowstone River alignment while the other diverging flood flow channel moved flood water in a southwest and northwest direction along the present day Jackson Creek-Rocky Creek alignment. The latter flood flow channel may also have split where Meadow Creek and Jackson Creek meet today with at least some of the water flowing in a southeast direction to the Yellowstone River valley, although Bridger Range (and Gallatin Range to the south) uplift may have begun dismemberment of the southeast oriented Meadow Creek-Trout Creek flood flow channel by the time the west-southwest and northwest oriented Rock Creek valley was eroded. Study of the figure 9 map area reveals evidence of many other flood flow channels, suggesting the entire region was crisscrossed by a maze of anastomosing flood flow channels. Figure 10 below provides a detailed topographic map of the Bridger Creek-Kelly Creek drainage divide area west of Green Mountain.

Detailed map of Bridger Creek-Kelly Creek drainage divide area

Figure 10: Detailed map of Bridger Creek-Kelly 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 Bridger Creek-Kelly Creek drainage divide area seen in less detail in figure 9 above. The East Gallatin River flows in a west-northwest direction across the figure 10 southwest corner. Kelly Creek is the west-southwest oriented East Gallatin River tributary flowing across sections 7, 12, and 11 in the figure 10 south half. Little Bridger Creek is a southwest oriented East Gallatin River tributary located in the figure 10 southwest quadrant. Bridger Creek is the west-southwest and west oriented stream seen near the figure 10 north edge flowing through sections 36, 35, and 34 to the figure 10 west edge (near northwest corner). Note the deep canyon Bridger Creek has eroded just north of Drinking Horse Mountain in section 34. Note also the multiple through valleys linking the west oriented Bridger Creek valley with the southwest oriented Kelly Creek and Little Bridger Creek valleys. The deepest through valley is located in section 6 and links a (barbed) north-northwest oriented Bridger Creek tributary with south-oriented Kelly Creek headwaters. The figure 10 map contour interval is 40 feet and the through valley floor elevation at the drainage divide is between 5440 feet and 5480 feet. The hill in near the section 1 east edge just to the west rises to 5774 feet while east of the through valley elevations rise even higher, meaning the through valley is approximately 300 feet deep. This 300-foot deep through valley was eroded by south-oriented flood flow diverging from the southwest and west oriented Bridger Creek flood flow channel and which was moving in a south and then southwest direction in the Kelly Creek valley to the East Gallatin River valley. Other slightly deeper through valleys can be found further to the west in section 2 and link a north-northwest oriented Bridger Creek tributary with both the Kelly Creek valley and the Little Bridger Creek valley. Floor elevations of these through valleys at the drainage divides are between 5320 and 5360 feet with the hill near the section 2 northwest corner rising to more than 5760 feet, making the through valleys almost 400 feet deep. Each of the through valleys mentioned was eroded by anastomosing south and southwest oriented flood flow channels crossing the present day Bridger Creek-Kelly Creek and Bridger Creek-Little Bridger Creek drainage divides. At the same time flood waters were eroding these south and southwest oriented flood flow channels west oriented flood waters were eroding the deep Bridger Creek canyon north of Drinking Horse Mountain. Headward erosion  of what became a much deeper west-oriented Bridger Creek flood flow channel (as the deep canyon north of Drinking Horse Mountain was eroded) beheaded the south and southwest oriented flood flow channels in sections 6 and 2. Flood waters on north ends of the beheaded flood flow channels reversed flow direction to erode north oriented (and barbed) Bridger Creek tributary valleys.

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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