Sixteenmile Creek-Shields River drainage divide area landform origins, central Montana, USA

Authors

Abstract:

Topographic map interpretation techniques are used to determine landform origins in the Sixteenmile Creek-Shields River drainage divide area located in central Montana. The Shields River is a southwest and south-southeast oriented Yellowstone River tributary and drains the northern Crazy Mountains and the south end of a broad north-south oriented through valley with the Shields River flowing from the Crazy Mountains and then between the Crazy Mountains to the east and the Bridger Range to west. North of the Shields River drainage basin the through valley is located between the Big Belt Mountains to the west and the Castle and Little Belt Mountains to the east and is drained by the north-northwest oriented Smith River, which flows to a northeast-oriented Missouri River segment. Flowing between the north-oriented Smith River and the south-oriented Shields River is west and southwest-oriented Sixteenmile Creek, which originates on the Crazy Mountains northwest flank and which flows between the Bridger Range to the south and the Big Belt Mountains to the north to join a north-northwest oriented Missouri River segment. North-south oriented through valleys link north-oriented Sixteenmile Creek tributaries with south-oriented Shields River tributaries and are interpreted to have been eroded as south-oriented flood flow channels which were beheaded by headward erosion of a much deeper Sixteenmile Creek valley. Flood waters on north ends of the beheaded flood flow channels reversed flow direction to erode the north-oriented Sixteenmile Creek tributary valleys. Flood waters are interpreted to have been derived from a rapidly melting thick North American ice sheet and were flowing from the ice sheet’s western rim in western Alberta and eastern British Columbia in south and southeast directions to and across Montana. Crustal warping related to the ice sheet’s tremendous weight is interpreted to have been raising Montana mountain ranges, including those in the study region, as flood waters flowed across them and contributed to the reversal of flood flow responsible for eroding the north-northwest oriented Missouri River valley segment and the north-northwest oriented Smith River valley.

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 available on this site can 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 Sixteenmile Creek-Shields River drainage divide area landform origins in central 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 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 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 Sixteenmile Creek-Shields River drainage divide area landform evidence in central Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm (see essay listed at header). This essay is included in the Missouri River drainage basin landform origins research project essay collection.

Sixteenmile Creek-Shields River drainage divide area location map

Figure 1: Sixteenmile Creek-Shields 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 Sixteenmile Creek-Shields River drainage divide area and illustrates a region in south central Montana with a strip of northwest Wyoming along the eastern half of the figure 1 south edge. Yellowstone National Park straddles the figure 1 south center edge and is located in the Wyoming northwest corner. The Yellowstone River flows in a northwest direction through Yellowstone National Park and into southern Montana where it turns to flow in a north-northeast direction to near Livingston. At Livingston the Yellowstone River turns again to flow in a northeast direction to Big Timber and then in an east-southeast and northeast direction to the figure 1 east edge. East of figure 1 the Yellowstone River flows in a northeast direction to join the Missouri River near the Montana-North Dakota border. The town of Three Forks is located west of Livingston on highway 90 and is where the north- and northwest-oriented Gallatin River, north-oriented Madison River, and north-northeast and east-oriented Jefferson River meet to form the north and north-northwest oriented Missouri River, which near Holter Lake turns to flow in a northeast direction (and north of the figure 1 map area eventually after a jog to the south turns to flow in more of an east direction). East of the north-northwest oriented Missouri River segment are the Big Belt Mountains. South of the Big Belt Mountains and between Bozeman and Livingston (and unlabeled in figure 1) is the Bridger Range, which is a north-south oriented mountain range between the Big Belt Mountains and the Gallatin Range. The southwest-oriented Missouri River tributary flowing through the towns Ringling and Maudlow between the Big Belt Mountains and the Bridger Range is Sixteenmile Creek, which is not labeled in figure 1. The unlabeled southwest and south-southeast oriented stream originating near Loco Mountain in the Crazy Mountains and flowing through Wilsall and Clyde Park to join the Yellowstone River a short distance downstream from Livingston is the Shields River. The south-southeast oriented Shields River tributary originating near Ringling is Potter Creek. The Sixteenmile Creek-Shields River drainage divide area investigated in this essay is located south of Sixteenmile Creek from its headwaters in the Crazy Mountains to approximately the location of Maudlow. The Sixteenmile Creek-Gallatin River drainage divide area landform origins Gallatin County, Montana essay illustrates and describes the region immediately to the west. Essays illustrating and describing other Montana and northern Wyoming Missouri River drainage divide areas can be found by selecting desired Missouri River tributaries and/or states from the sidebar list of categories.
  • Drainage routes in the figure 1 map region (and in a much larger region) evolved during immense south and southeast-oriented melt water floods derived from a rapidly melting thick North American ice sheet, which was located in a deep “hole.” The deep “hole” did not exist when the ice sheet first formed but was created by a combination of deep glacial erosion (under the ice sheet) and of crustal warping that raised regions adjacent to the giant ice mass. The crustal warping was responsible for uplift of all mountain ranges seen in figure 1, although deep erosion of rising mountain masses by massive melt water floods and deposition of the eroded debris in adjacent valleys and basins may have contributed to the crustal warping. The Missouri River drainage basin in Montana and northern Wyoming is located on the deeply eroded deep “hole” southwest wall. The Canadian Rocky Mountains in western Alberta and eastern British Columbia are located along what was the deep “hole’s” western rim. Flood waters eroding the figure 1 map area were generally coming from the deep “hole’s” western rim and flowing in south and southeast directions into and across Montana to Wyoming with the flood water east of the developing east-west continental divide eventually reaching the Gulf of Mexico. South of northern Wyoming the east-west continental divide was being carved as ice sheet related crustal warping was raising the Rocky Mountains (from south to north) and as deep valleys from the east and the west eroded headward into the rising mountains to capture the immense south and southeast-oriented melt water floods (again from south to north). In time however, as east-west continental divide formation was reaching southern and central Wyoming the combination of crustal warping and of ice sheet melting began to create a different flood flow pattern. Ice sheet melting, especially near the ice sheet’s southern margin, and uplift of ice sheet margin regions in Montana and northern Wyoming created a situation where the immense south and southeast-oriented meltwater floods in Montana and northern Wyoming were flowing at higher elevations than elevations of space being opened up in the deep “hole” the melting ice sheet had once occupied. Deep northeast and east-oriented valleys then eroded headward from the newly opened up deep “hole” space into Montana and northern Wyoming to capture the south and southeast-oriented meltwater floods. These deep valleys eroded headward in sequence from the southeast to the northwest.
  • Headward erosion of the deep east and northeast oriented Yellowstone River valley and its tributary valleys from newly opened up deep “hole” first captured the south and southeast-oriented melt water floods. North and northwest oriented tributary valleys were eroded by reversals of flood flow on north and northwest ends of beheaded south and southeast-oriented flood flow channels. Note how the Yellowstone River in Yellowstone National Park flows in a northwest direction before making a U-turn to flow in an east and east-southeast direction in southern Montana to the north. The northwest-oriented Yellowstone River valley segment was eroded by a massive flood flow reversal on the northwest end of a beheaded southeast-oriented flood flow channel. South and southeast-oriented flood flow to the newly eroded east and northeast oriented Yellowstone River valley (and tributary valleys) was subsequently captured by headward erosion of the deep northeast and east oriented Missouri River valley.
  • Flood waters on north and northwest ends of south and southeast-oriented flood flow channels to the newly eroded Yellowstone  River valley (and west of the Livingston region to what was then the actively eroding west-oriented Snake River valley) reversed flow direction to erode north and northwest oriented valleys. In figure 1 the north-northwest oriented Smith River, which originates north of the Shields River near Ringling and which flows between the Big Belt Mountains and Little Belt Mountains to join the northeast oriented Missouri River north of the figure 1 map area (west half), was formed by such a flood flow reversal as was the north-northwest oriented Missouri River. Prior to being beheaded and reversed the Smith River alignment was used as a south-southeast oriented flood flow channel moving flood waters to the south-oriented Shields River alignment sand then to the newly eroded east and northeast-oriented Yellowstone River valley. Prior to headward erosion of the much deeper east and northeast-oriented Yellowstone River valley the south-southeast oriented flood flow continued to move in a south and southeast direction along a flood flow channel on the present day northwest and north-oriented Yellowstone River alignment upstream from Livingston. In other words the south-oriented Shields River is flowing in valley originally formed by a major south-oriented meltwater flood channel, which was then dismembered first by headward erosion of the much deeper east and northeast-oriented Yellowstone River valley that beheaded and reversed the flood flow channel south of Livingston to create the northwest- and north-oriented Yellowstone River headwaters valley seen today, and second by headward erosion of the much deeper northeast- and east-oriented Missouri River valley that beheaded the south-southeast oriented flood flow channel to create the north-northwest oriented Smith River valley seen today. Today the Shields River is the only drainage route in this dismembered flood flow channel still flowing in a south direction.

Detailed location map for Sixteenmile Creek-Shields River drainage divide area

Figure 2: Detailed location map for Sixteenmile Creek-Shields 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 Sixteenmile Creek-Shields River drainage divide area. Green shaded areas are National Forest lands and are generally located in mountainous regions. The green shaded area straddling the north edge of the figure 2 northeast quadrant is in the Castle Mountains. The green shaded area in the figure 2 east half south of the Castle Mountains is in the Crazy Mountains. The green shaded area in the figure 2 west half straddling the figure 2 north edge is in the Big Belt Mountains, and the green shaded area in the figure 2 west half straddling the figure 2 south edge is in the Bridger Range.  Ringling is the town located near the figure 2 center. Sixteenmile Creek originates on the west edge of the Crazy Mountains (north of Wolf Hill) and flows in a west, north-northwest, and west-southwest direction to Ringling. From Ringling Sixteenmile Creek flows in a southwest direction to Maudlow and then in a west-northwest and west-southwest direction to join the north-oriented Missouri River near Lombard. The Missouri River flows in a north-northeast direction from the figure 2 southwest corner to Lombard and then in a north-northwest direction to Townsend. The lake north of Townsend in the figure 2 northwest corner region is Canyon Ferry Lake, a large reservoir flooding the Missouri River valley. Named Sixteenmile Creek tributaries of importance in this essay are north-oriented Lost Creek, which joins Sixteenmile Creek near Ringling, and southwest and west-oriented Middle Fork which joins Sixteenmile Creek upstream from Maudlow. A unamed Middle Fork tributary of importance is north and north-northwest oriented South Fork Sixteenmile Creek, which flows from the northern Bridger Range to join the Middle Fork south of the town of Francis.
  • The Shields River originates in the Crazy Mountains (south of Bald Ridge) and flows in a west-southwest, southwest, south-southwest, and south direction to Wilsall and then in a south-southeast direction to the figure 2 south edge (east half). Important Shields River tributaries in this essay are south-southeast oriented Potter Creek, which originates near Ringling, and east-northeast oriented Flathead Creek, which originates south of the north-oriented South Fork Sixteenmile Creek headwaters in the Bridger Range and which joins the Shields River near Wilsall. Many Shields River tributaries are oriented in south directions and are still oriented in the same direction as the flood flow channels which previously flowed across region. Flathead Creek is an exception and may be flowing in a valley initially formed as a diverging west-southwest oriented flood flow channel moving flood waters across the present day Bridger Range. Bridger Range uplift and erosion of a deeper south-oriented Shields River valley caused flood waters on the west-northwest end of this flood flow channel to reverse flow direction and to erode the west-northwest oriented Flathead Creek valley (this hypothesis will be further discussed in the figures 9 and 10 discussions). North-oriented Sixteenmile Creek tributaries, including Lost Creek and the South Fork Sixteenmile Creek, are located in valleys that originally were formed by south and south-southeast oriented flood flow channels and which were beheaded by headward erosion of the much deep southwest-oriented Sixteenmile Creek valley. Flood waters on north ends of the beheaded flood flow channels reversed flow direction to erode the present day north-oriented valleys.

Sixteenmile Creek-Shields River drainage divide area in Crazy Mountains

Figure 3: Sixteenmile Creek-Shields River drainage divide area in Crazy Mountains. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

  • Figure 3 illustrates the Sixteenmile Creek-Shields River drainage divide area in the Crazy Mountains. The Crazy Mountains northwest flank is located in the figure 3 east half. The Shields River flows in a west-southwest and southwest direction from the figure 3 east edge (south half) to the figure 3 south center edge. Smith Creek is the south-oriented tributary flowing between Bear Mountain and Billie Butte. Mount Elmo is located near the figure 3 northeast corner. The northwest and northeast-oriented streams on either side of Mount Elmo are tributaries to north-oriented Cottonwood Creek, which flows to the east-northeast oriented South Fork Mussel River, which in turn flows to the east- and north-oriented Musselshell River with water eventually reaching the east-oriented Missouri River. Kavanaugh Creek is the south-oriented Shields River tributary flowing to the figure 3 south center edge and joining the Shields River south of the figure 3 south center edge. Sixteenmile Creek originates north of Bear Mountain and flows in a southwest, west, and north-northwest direction to the figure 3 northwest corner. Note how west-oriented Sixteenmile Creek headwaters are linked by a through valley north of Bear Mountain with a southeast-oriented Smith Creek tributary valley. The figure 3 map contour interval is 50 meters and the through valley floor elevation at the drainage divide is between 1950 and 2000 meters. Scab Rock Mountain to the south rises to 2468 meters while north of Bald Ridge along the figure 3 north edge elevations greater than 2500 meters can be found. In other words the through valley is almost 500 meters deep. The through valley is a water eroded feature and was eroded by southeast-oriented flood flow moving to the south-oriented Smith Creek valley and then probably to the south-oriented Shields River valley. Another north-south oriented through valley is located west of Bear Mountain and links the west-oriented Sixteenmile Creek valley with the south-oriented Kavanaugh Creek valley. The through valley floor elevation at the drainage divide is between 1800 and 1850 meters while Scab Rock Mountain to the east rises to 2468 meters and Wolf Hill to the west to more than 2000 meters. The north-south oriented linear ridges are probably hogbacks indicating the through valley is eroded along an easily to erode geologic unit. Even so the through valley is a water eroded feature and is deeper than the Sixteenmile Creek-Smith Creek through valley north of Bear Mountain. These through valleys and others seen in the figure 3 map area provide evidence of multiple south-oriented flood flow channels linking the Sixteenmile Creek valley and the Shields River valley. Headward erosion of the west-oriented Sixteenmile Creek valley beheaded and reversed the south-oriented flood flow channels to the Shields River valley.

Detailed map of Sixteenmile Creek-Kavanaugh Creek drainage divide area

Figure 4: Detailed map of Sixteenmile Creek-Kavanaugh Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

 

  • Figure 4 illustrates a detailed topographic map of the Sixteenmile Creek-Kavanaugh Creek drainage divide area seen in less detail in figure 3 above. Bear Mountain and Scab Rock Mountain are labeled and are located near the figure 4 east edge. Kavanaugh Creek flows in a south direction in sections 9 and 16 to the figure 4 south center edge and south of figure 4 joins the south oriented Shields River. Sixteenmile Creek can be seen flowing in a southwest and west direction across and along the figure 4 north edge. Note the north-oriented tributary flowing from section 9 to join west-oriented Sixteenmile Creek near the north edge of section 4 and how that tributary has south- and east-oriented headwaters in the section 9 northwest quadrant. The figure 4 map contour interval is 40 feet and the Sixteenmile Creek-Kavanaugh Creek through valley floor elevation at the drainage divide in section 9 is between 5960 and 6000 feet. The ridge immediately to the west rises to more that 6400 feet although Wolf Hill in the figure 4 southwest corner rises to more than 6500 feet meaning the through valley is at least 400 feet deep. Linear ridges in the figure 4 west half are hogback ridges and are composed of erosion resistant strata and the through valley is probably eroded an easily eroded geologic unit. However, the through valley is a water eroded feature and was eroded by south-oriented flood flow moving from the present day Sixteenmile Creek valley to the south-oriented Shields River valley. Note how Sixteenmile Creek has eroded deep water gaps across the north-south oriented hogback ridges. As seen in figure 3 above, west of the figure 4 map area and west of the water gaps cutting across the hogback ridges, Sixteenmile Creek turns to flow in a north-northwest direction. The water gaps provide evidence the hogback ridges did not stand high above the surrounding valleys when flood waters first crossed the region. The north-northwest oriented Sixteenmile Creek valley segment north and west of figure 4 originated as a south-southeast oriented flood flow channel which converged with a southwest-oriented flood flow channel on the Sixteenmile Creek headwaters alignment to form a south-oriented flood flow channel on the Kavanaugh Creek alignment. Remember west of figure 4 and west of the hogback ridges is another larger north-south oriented through valley (seen in figure 5 below), which was also eroded as a south-oriented flood flow channel, and between the various hogback ridges are still additional north-south oriented through valleys. The through valleys provide evidence of multiple converging and diverging flood flow channels such as might be found in a large-scale south-oriented anastomosing channel complex. The water gaps provide evidence of deep flood water erosion that eroded deep valleys surrounding, across, and between the hogback ridges.

Sixteenmile Creek-Potter Creek drainage divide area

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

 

  • Figure 5 illustrates the Sixteenmile Creek-Potter Creek drainage divide area north and west of the figure 3 map area and includes overlap areas with figure 3. Ringling is the town located in the figure 5 northwest quadrant. Sixteenmile Creek flows in a west direction across the hogback ridges from the figure 5 east edge (north of center) and then flows in a north-northwest direction to near the figure 5 north center edge and then turns to flow in a west-southwest direction to Ringling before turning to flow in a south-southwest direction to the figure 5 west edge (south of center). The north-south oriented hogbacks seen in figures 3 and 4 are located in the figure 5 east half. Rees Hills are located south of Sixteenmile Creek in the figure 5 east center region. Cottonwood Creek originates south of the Rees Hills and flows in a west and north direction to join Sixteenmile Creek north and west of the Rees Hills. The north-oriented stream joining Sixteenmile Creek near Ringling is Lost Creek. Note west of Lost Creek is an unnamed north- and west-oriented Sixteenmile Creek tributary. Between north-oriented Lost Creek and the north-oriented Cottonwood Creek segment are headwaters of south-oriented Potter Creek, which flows to the figure 5 south center edge (near highway) and south of the figure 5 map area joins the south-oriented Shields River. The figure 5 map contour interval is 50 meters and note how no contour lines separate headwaters of a north-oriented Sixteenmile Creek tributary from headwaters of south-oriented Potter Creek. The through valley floor elevation at the drainage divide is between 1650 and 1700 meters. The high forested ridge seen near the figure 5 southwest corner rises to 2133 meters and higher elevations can be found west of figure 5. Wolf Hill (south of the Rees Hills) rises to more than 2000 meters and higher elevations can be found east of the figure 5 map area. While the north-south oriented through valley drained in the south by Potter Creek is undoubtably a structural valley it is also a water eroded valley and was eroded by south-oriented flood flow moving from the north-oriented Sixteenmile Creek valley in a south direction to the south-oriented Shields River valley. Today north of the Sixteenmile Creek valley is the north-northwest oriented South Fork Smith River, which flows to the north-northwest oriented Smith River. The south-oriented Smith River-Shields River flood flow channel was dismembered in the figure 5 map area by headward erosion of Sixteenmile Creek valley, which beheaded and reversed the south-oriented flood flow to the Shields River valley as crustal warping raised the figure 5 map region faster than south-oriented flood waters could erode the south-oriented flood flow channels. Headward erosion of the deep northeast-oriented Missouri River valley subsequently beheaded and reversed flood flow on the present day north-northwest oriented Smith River alignment to complete the dismemberment process.

Detailed map of Sixteenmile Creek-Potter Creek drainage divide area

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

 

  • Figure 6 uses reduced size detailed topographic maps to illustrate the Sixteenmile Creek-Potter Creek drainage divide area seen in less detail in figure 5. Ringling is the town near the figure 6 northwest corner. Sixteenmile Creek flows in a west direction from the figure 6 east center edge to section 35 where it turns to flow in a north-northwest and west-northwest direction to the figure 6 north center edge. North of figure 6 Sixteenmile Creek turns to flow in a west-southwest direction across the figure 6 northwest corner (through Ringling). Cottonwood Creek originates south of the Rees Hills in the figure 6 southeast quadrant and flows in southwest and west direction to the section 11 northeast quadrant and then turns to flow in a north-northwest direction to join Sixteenmile Creek in section 35. Also joining Sixteenmile Creek near the section 35 north edge is southwest, west, and southwest oriented Canyon Creek. Note how these streams have eroded valleys across north-south oriented hogback ridges. An unnamed north-oriented Sixteenmile Creek tributary originates in section 28 (in figure 6 north center) and joins Sixteenmile Creek near the figure 6 north center edge. South of section 28 in section 33 is a north-south oriented through valley linking the north-oriented Sixteenmile Creek tributary valley with the south-oriented Potter Creek valley, with Potter Creek flowing to the figure 6 south center edge. Potter Creek originates west of the north-south oriented through valley and flows in a north-northeast and east direction in section 5 before entering the through valley in section 4, where it turns to flow in a south direction. West of the Potter Creek headwaters in section 6 is north-oriented Lost Creek, which flows from south of the figure 6 south edge (near southwest corner) past the Potter Ranch to join Sixteenmile Creek near Ringling. Note how Lost Creek is flowing in a north direction while adjacent Potter Creek is flowing in a south direction. Also note in section 34 (just east of the Sixteenmile Creek-Potter Creek through valley in section 33) there is a wind gap eroded across the north-south oriented ridge separating the north-northwest oriented Sixteenmile Creek valley from its north-oriented tributary valley (Sixteenmile Road makes use of the wind gap). The section 34 wind gap or through valley was last eroded by west- or northwest-oriented flood water moving into a deeper north-south oriented through valley and the west- or northwest-oriented flood flow deposited a large alluvial fan or delta of debris on the east side of the through valley which today serves as the dividing point between the north-oriented Sixteenmile Creek tributary drainage and the south-oriented Potter Creek drainage. The debris blocking the north-south oriented through valley in section 33 was probably deposited during the flood flow reversal that occurred as the deep west-southwest Sixteenmile Creek valley beheaded and reversed south-oriented flood flow channels that existed between the north-south oriented hogback ridges. These south-oriented flood flow channels were beheaded and reversed one at a time from the west to the east and reversed flood flow in a newly reversed flood flow channel could sometimes capture flood waters from a yet to be beheaded flood flow channels further to the west. Westward movement of such captured flood waters carved west-oriented valleys such as that seen in section 34.

Lost Creek-Cottonwood Creek drainage divide area

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

  • Figure 7 illustrates the Lost Creek-Cottonwood Creek drainage divide area south and west of figure 5 and includes overlap areas with figure 5. Potter Creek flows in a south and south-southeast direction from the figure 7 north edge (east half) to the figure 7 southeast corner region. Cottonwood Creek originates just south of the figure 7 center and flows in a southeast direction to join Potter Creek south of the figure 7 southeast corner. North of the Cottonwood Creek valley and east of Elk Ridge are headwaters of north-oriented Lost Creek which flow to the figure 7 north edge (just east of center). West of the Lost Creek headwaters are headwaters of southwest and west oriented Middle Fork Sixteenmile Creek, which flows to the figure 7 west edge (south of center) and then continues to flow in a west direction to join Sixteenmile Creek west of the figure 7 map area. North-of the southwest oriented Middle Fork Sixteenmile Creek headwaters is a north-oriented tributary to north-oriented Meadow Creek, which flows to Sixteenmile Creek north of the figure 7 map area. Note the north-south oriented through valley linking the north-oriented Meadow Creek tributary valley with the southwest and west-oriented Middle Fork Sixteenmile Creek valley. The figure 7 map contour interval is 50 meters and the through valley floor elevation at the drainage divide is between 1800 and 1850 meters. The ridge immediately to the east rises to 2133 meters while a spot elevation on Elkhorn Ridge to the west reads 2190 meters making the through valley approximately 300 meters deep. The through valley was eroded by south, southwest, and west-oriented flood flow moving to the actively eroding and much deeper Sixteenmile Creek valley west of the figure 7 map area. At that time there was no Sixteenmile Creek valley north of figure 7 although flood waters were also flowing in a more direct southwest direction on what is today the deeper Sixteenmile Creek valley (and on other routes that can be reconstructed using other through valleys). Headward erosion of the much deeper Sixteenmile Creek valley beheaded and reversed the south-, southwest-, and west-oriented flood channel and flood waters on the north end reversed flow to erode the north-oriented Meadow Creek and Meadow Creek tributary valley. Looking at the Lost Creek-Cottonwood Creek through valley, just to the east of this Meadow Creek-Middle Fork Sixteenmile Creek through valley, there is evidence of another south-oriented flood flow channel, which did not get captured by headward erosion of the deep west- and southwest-oriented Middle Fork Sixteenmile Creek valley. These south-oriented flood flow channels were captured instead by headward erosion of the southeast-oriented Cottonwood Creek valley, which eroded headward from the south-oriented Potter Creek valley, which was eroding headward from the south-oriented Shields River valley. These south-oriented flood flow channels were also beheaded and reversed by headward erosion of the deep Sixteenmile Creek valley (north of figure 7) and flood waters on the north ends of the beheaded flood flow channels reversed flow direction to erode north-oriented Sixteenmile Creek tributary valleys, such as the Lost Creek valley.

Detailed map of Lost Creek-Cottonwood Creek drainage divide area

Figure 8: Detailed map of Lost Creek-Cottonwood 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 Lost Creek-Cottonwood Creek drainage divide area seen in less detail in figure 7 above. Elk Ridge is the north-south oriented ridge located just east of the figure 8 center. Lost Creek originates near the abandoned McMurdo Ranch in section 24 in the figure 8 northeast quadrant just east of Elk Ridge. The south-oriented stream originating near the figure 8 south edge in the north-south oriented through valley east of Elk Ridge is a south-oriented Cottonwood Creek tributary. The drainage divide between north-oriented Lost Creek and the south-oriented Cottonwood Creek tributary is found in the south half of section 36 and has an elevation of between 6220 and 6240 feet (the figure 8 map contour interval is 20 feet). Elk Ridge to the west rises to more than 6800 feet while the ridge to the east is somewhat lower and has a few points rising above 6400 feet. Using the 6400 feet elevation as the marker the through valley is perhaps 170 feet deep. The through valley was eroded by south-oriented flood flow moving to the southeast-oriented Cottonwood Creek valley south of the figure 8 map area. Looking at the north-south oriented through valley just west of Elk Ridge the Cottonwood Creek headwaters are located along the figure 8 south center edge in section 2. The drainage divide is located in section 2 and a north-oriented stream originates in the section 2 north half and flows to the figure 8 north center edge. North of figure 8 the stream turns to flow in a northwest direction and joins north-oriented Meadow Creek. The section 2 through valley is actually two parallel through valleys separated by a north-south oriented erosional residual. The deeper through valley (the eastern valley) has an elevation at the drainage divides of between 6380 and 6400 feet. Elk Ridge to the east rises to more than 6900 feet while elevations greater than 6900 feet can be found in section 3 to the west suggesting the through valley is at least 500 feet deep. although it is not as deep as the Lost Creek-Cottonwood Creek through valley east of Elk Ridge. South and southwest oriented Middle Fork Sixteenmile Creek headwaters can be seen in section 32 near the figure 8 west edge (south half). In section 29 to the north there is a north-south oriented through valley linking the south, southwest, and west-oriented Middle Fork Sixteenmile Creek valley with a north-oriented Meadow Creek tributary valley. The through valley floor elevation at the drainage divide is between 6040 and 6060 feet. The ridge to the east rises to 6999 feet and Elkhorn Ridge (west of figure 8 rises to more than 7000 feet meaning the through valley is more than 900 feet deep. An interesting east-west oriented through valley ins sections 33 and 34 links the north-south oriented Meadow Creek-Middle Fork Sixteenmile Creek through valley with the north-south oriented Meadow Creek-Cottonwood Creek through valley and provides evidence of diverging and converging flood flow channels such as might be found in a large-scale anastomosing channel complex.

South Fork Sixteenmile Creek-Flathead Creek drainage divide area

Figure 9: South Fork Sixteenmile Creek-Flathead Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

 

  • Figure 9 illustrates the South Fork Sixteenmile Creek-Flathead Creek drainage divide area west and south of the figure 7 map area and includes overlap areas with figure 7. The Bridger Range is the high north-south oriented mountain range seen in the figure 9 southwest corner. Flathead Pass (near southwest corner) is a deep northeast-southwest-oriented pass or through valley crossing the Bridger Range north end. The north and northwest oriented stream flowing from the figure 9 south edge (west half) and then between Horsethief Mountain and Red Rock Mountain to the figure 9 west edge (near northwest corner) is the South Fork Sixteenmile Creek and joins the west-oriented Middle Fork Sixteenmile Creek north and west of figure 9 with the Middle Fork Sixteenmile Creek then joining Sixteenmile Creek, which flows to the north-oriented Missouri River. The South Fork Flathead Creek originates near the figure 9 south edge, just east of the north-oriented South Fork Sixteenmile Creek headwaters, and flows in an east-northeast direction to join the southeast-oriented Middle Fork and south-southeast oriented North Fork to form east-northeast oriented Flathead Creek, which then flows to the figure 9 east edge (south half). East of figure 9 Flathead Creek flows to the south-oriented Shields River. Note the deep water gap eroded by the South Fork Sixteenmile Creek between Horsethief Mountain and Red Rock Mountain. The figure 9 map contour interval is 50 meters and the South Fork Sixteenmile Creek channel in the water gap has an elevation of less than 1700 meters. Red Rock Mountain rises to more than 2200 meters and the Bridger Range west of Horsethief Mountain rises even higher meaning the water gap is at least 500 meters deep. The water gap was first eroded by a southeast and southwest-oriented flood flow channel moving flood waters to what was at that time a southwest-oriented flood flow channel on the Flathead Pass alignment. A west-southwest oriented flood flow channel on the Flathead Creek alignment probably merged with this southeast and southwest-oriented flood flow channel. West of the Bridger Range flood waters flowed in a south direction to the Gallatin River valley, which was initiated as a southeast- and south-oriented flood flow channel, but which was reversed when south-oriented flood flow in the present day north and north-northwest oriented Missouri River valley was beheaded and reversed. Bridger Range uplift occurred as flood waters were eroding the deep Flathead Pass valley and eventually blocked the southwest-oriented flood flow forcing flood waters to flow in an east-northeast direction along the Flathead Creek alignment to the south-oriented Shields River valley. Next headward erosion of the deep Sixteenmile Creek-Middle Fork Sixteenmile Creek valley north of figure 9 beheaded the southeast-oriented flood flow to the newly reversed Flathead Creek valley (or newly formed east-northeast oriented flood flow channel) and flood waters on the northwest end of the beheaded flood flow channel reversed flow direction to erode the north- and northwest-oriented South Fork Sixteenmile Creek valley seen today.

Detailed map of South Fork Sixteenmile Creek-Flathead Creek drainage divide area

Figure 10: Detailed map of South Fork Sixteenmile Creek-Flathead Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

 

  • Figure 10 provides a detailed map of the South Fork Sixteenmile Creek-Flathead Creek drainage divide area seen in less detail in figure 9 above. The South Fork Sixteenmile Creek originates in section 33 (near figure 10 south edge-west half) and flows in a generally north direction to the figure 10 north edge (west of center). North of the figure 10 map area the South Fork Sixteenmile Creek flows in a northwest direction to join west-oriented Middle Fork Sixteenmile Creek with water eventually reaching the north oriented Missouri River. The South Fork Flathead Creek originates in the section 33 southeast corner (just east of the South Fork Sixteenmile Creek headwaters) and flows in an east-northeast direction to the figure 10 east edge (south half).  A southeast oriented tributary joins the South Fork Flathead Creek in section 35. The Middle Fork Flathead Creek originates in section 27 and flows in a southeast and northeast direction to the section 26 northeast corner and then turns to flow in a southeast direction to the figure 10 east edge and joins the South Fork Flathead Creek east of figure 10 to form east-northeast oriented Flathead Creek. Note how the north and northwest-oriented South Fork Sixteenmile Creek valley is linked by a deep and broad through valley with the east-northeast oriented Flathead Creek valley. The high Bridger Range can be seen in the figure 10 southwest corner with elevations greater than 8000 feet visible (the figure 10 map contour interval is 40 feet-20 feet along the figure 10 north edge). Elevations greater than 6700 feet can be found in the figure 10 northeast corner region. The South Fork Sixteenmile Creek-Middle Fork Flathead Creek drainage divide in section 27 has an elevation of between 6240 and 6280 feet or more than 420 feet lower than elevations to the northeast. This 420-foot deep through valley was eroded by southeast-, south-, and east-oriented flood waters flowing on what is today the north and northwest-oriented South Fork Sixteenmile Creek alignment to the present day east-northeast oriented Flathead Creek alignment. Flathead Pass seen near the figure 10 west center edge has an elevation 6922 feet and for time (prior to the flood flow reversal that eroded the deep east-northeast oriented Flathead Creek valley) southwest-oriented flood flow moved across Flathead Pass to the Bridger Range west side and then to the Gallatin River valley. Bridger Range uplift ended that southwest-oriented flood flow and forced the water to flow in the opposite direction or in an east-northeast direction along what had been an west-southwest oriented Flathead Creek flood flow channel to reach the south-oriented Shields River flood flow channel. That change in flood flow direction eroded the deep South Fork Sixteenmile Creek-Flathead Creek through valley and the deep east-northeast oriented Flathead Creek valley seen today. Subsequently headward erosion of the deep west-oriented Sixteenmile Creek-Middle Fork Sixteenmile Creek valley beheaded the southeast- and south-oriented flood flow to the east-northeast-oriented Flathead Creek valley and flood waters on the north and northwest end of the beheaded flood flow channel reversed flow direction to erode the present day north- and northwest-oriented South Fork Sixteenmile Creek valley.

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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