Teton River-Sun River drainage divide area landform origins, eastern Teton County, Montana, USA

Abstract:

Topographic map interpretation methods are used to determine landform origins in the Teton River-Sun River drainage divide area of eastern Teton County, Montana. The Teton River and Sun River are east oriented Missouri River tributaries, both of which in Teton County originate along the east west continental divide and then flow from deep mountain valleys onto the Montana plains. This essay addresses the drainage divide area region east of the mountains. Teton Ridge is a well-defined west to east oriented ridge which today forms a significant segment of the eastern end of the Teton River-Sun River drainage divide. Deep north-south and northwest-southeast oriented through valleys are cut across Teton Ridge and provide evidence of multiple south and southeast-oriented flood flow channels, which once crossed the region. At that time the east-oriented Teton River valley did not exist and the flood flow channels were being eroded into a surface at least as high as the highest Teton Ridge elevations today. Between the mountain front and the Teton Ridge west end large east-oriented through valleys link Teton River tributary valleys with both the east-oriented Teton River valley and the east-oriented Sun River valley. These through valleys are interpreted to have been eroded as diverging and converging flood flow channels in a large east-oriented anastomosing channel complex of which the Teton River and Sun River valleys were important components. Flood waters eroding the anastomosing channel complex came from the mountain area to the west and are interpreted to have been derived from a rapidly melting thick North American ice sheet, located in a deep “hole.” The present day northern Montana and adjacent Canadian east-west continental divide was the location deep “hole’s” western rim and immense south and southeast-oriented ice-marginal floods flowed along that rim as Rocky Mountain uplift combined deep flood water erosion gradually produced the present day Rocky Mountain topography.

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 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 Teton River-Sun River drainage divide area landform origins in eastern Teton County, 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 Teton River-Sun River drainage divide area landform evidence in eastern Teton County, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm (see link to paradigm related essay above this essay’s title). This essay is included in the Missouri River drainage basin landform origins research project essay collection.

Teton River-Sun River drainage divide area location map

Figure 1: Teton River-Sun 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 Teton River-Sun River drainage divide area in eastern Teton County, Montana and shows a region in north central and northwest Montana. The Canadian border is located along the figure 1 north edge. Glacier National Park is located in the figure 1 northwest corner. The Missouri River flows in a northwest direction from the figure 1 south center edge to near Craig where it turns to flow in a northeast direction to Great Falls, Fort Benton, and Loma. South of Big Sandy (and downstream from Loma) the Missouri River turns abruptly to flow in a south-southeast and then east-northeast direction to the figure 1 east center edge. Water in the Missouri River flows to the Mississippi River and eventually reaches the Gulf of Mexico. The Sun River is an east-oriented tributary joining the Missouri River at Great Falls. The Teton River is another east-oriented tributary, located north of the Sun River, and joins the Missouri River near Loma. Both the Sun River and the Teton River originate along the east-west continental divide which extends in a south-southeast direction from the figure 1 northwest corner along the crest of the Lewis Clark Range to the figure 1 south edge (just west of Helena). West of the continental divide are the northwest-oriented Middle Fork Flathead River and the north-northwest oriented South Fork Flathead River. The Middle and South Forks of the Flathead River flow to the south-oriented Flathead River, which is west of the figure 1 map area although it does flow through Flathead Lake seen along the figure 1 west edge. The Flathead River flows to northwest-oriented Clark Fork (seen in figure 1 southwest corner) with water eventually reaching the Columbia River which flows to the Pacific Ocean. The Teton River-Sun River drainage divide area in eastern Teton County is located east of the mountains and is south of the Teton River and north of the Sun River. The Birch Creek-Teton River drainage divide area landform origins in Pondera and Teton Counties essay describes the region to the north. The Teton River-Missouri River drainage divide area landform origins in Chouteau County essay describes the region to the east and the Teton River-Sun River drainage divide area landform origins in western Teton County essay describes the region to the west. Other essays can be found by selecting desired Missouri River tributaries from the sidebar category list.

Drainage routes in the figure 1 map region were established during the rapid melt down of a thick North American ice sheet, which was located in a deep “hole.” The Upper Missouri River drainage basin in Montana and northern Wyoming (and the Saskatchewan River drainage basin in southwest Alberta) represent the deeply eroded west and southwest wall of the deep “hole” the ice sheet once occupied. The crests of Rocky Mountain ranges in figure 1, including the east-west continental divide, are segments of the deep “hole’s” deeply eroded western and southwest rim. The deep “hole” was formed after the ice sheet had developed and was created by deep glacial erosion under the ice sheet and by crustal warping of regions elsewhere on the continent including uplift of the Rocky Mountains and plateau areas in western North America. At one time the ice sheet stood high above this western and southwest rim (or the present day Canadian and Montana Rocky Mountains) and ice-marginal melt water floods could easily flow in south and southeast directions along what are now the crests of high mountain ranges. The entire figure 1 map area, both east and west of the continental divide, and a much larger region, was crossed by immense south and southeast oriented ice-marginal melt water floods. Initially these immense south and southeast-oriented floods could freely move in south and southeast directions across Montana and Wyoming and Colorado into New Mexico and further along routes now marked by high Rocky Mountain ranges. The present day east-west continental divide was created as Rocky Mountain uplift (proceeding from the south to the north) blocked the south-oriented flood waters forcing flood waters to flow in both east and west directions and to erode deep southeast- and southwest-oriented valleys headward into the rising Rocky Mountains.

In time a combination of Rocky Mountain uplift and of ice sheet melting created a situation where the ice sheet surface was lower in elevation than the ice marginal bedrock surfaces on which the massive south and southeast oriented ice-marginal floods were moving. Deep east and northeast-oriented valleys then began to erode headward from giant south oriented ice-walled canyons being eroded in the decaying ice sheet’s surface. These deep east and northeast-oriented valleys eroded headward in sequence from the south and southeast to the north and northwest. Headward erosion of the east oriented Missouri River across northern Montana (east of the figure 1 map area) was the last such deep valley to erode headward to capture the huge ice-marginal floods in the United States although the South Saskatchewan River valley and the North Saskatchewan River valley subsequently eroded headward into Alberta to also capture the ice-marginal floods. At the same time west of the present day continental divide the west-oriented Columbia River valley and its tributary valleys eroded headward from the Pacific Ocean to also capture the south and southeast-oriented melt water floods. In the deep “hole” rim area, which is today marked by deeply eroded and linear mountain ranges, the south and southeast-oriented flood waters were eroding deep south and southeast-oriented flood flow channels. As these south and southeast-oriented flood flow channels were beheaded by headward erosion of much deeper east- and/or west-oriented valleys, flood waters on the north and northwest ends of the beheaded flood flow channels reversed flow direction to erode what are today north and/or northwest-oriented valleys. Excellent examples of valleys eroded by such massive flood flow reversals can be seen in figure 1. West of the continental divide the northwest-oriented Middle Fork Flathead River, the north-northwest oriented South Fork Flathead River, and the Clark Fork valleys were all eroded by massive flood flow reversals in former south- and southeast-oriented flood flow channels. East of the continental divide the north-northwest oriented Missouri River segment and northwest and north-northwest oriented tributaries to the northeast-oriented Missouri River segment all flow in valleys eroded by massive reversals of flood flow on north ends of beheaded southeast- and south-southeast oriented flood flow channels.

Detailed location map for Teton River-Sun River drainage divide area

Figure 2: Detailed location map for Teton River-Sun 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 Teton River-Sun River drainage divide area in eastern Teton County, Montana. County boundaries are shown and Teton County is labeled. Great Falls is the major city shown and is located in Cascade County in the figure 2 southeast corner. The northeast-oriented Missouri River can be seen in the figure 2 southeast corner flowing through Great Falls. The Teton River originates near the Teton County northwest corner near Mt. Patrick Gass and flows in a south-southeast and southeast direction to the Cave Mtn area and then turns to flow in an east direction onto the Montana plains. Once on the plains the Teton River makes a southeast jog to Choteau and then turns to flow in a northeast and east direction to the Teton County northeast corner and then to figure 2 east center edge. Willow Creek is a major tributary joining the Teton River just south of Choteau. The North and South Forks Willow Creek originate north and south of Ear Mtn and join near Pine Butte to form southeast and east-northeast oriented Willow Creek. Deep Creek is a major Willow Creek tributary and is formed at the confluence of its North and South Forks near Long Ridge and then flows in an east direction to join Willow Creek. South of Collins and north of Teton Ridge there are several unnamed north-oriented Teton River tributaries and further east in the Teton County northeast corner there are northeast and north-northeast oriented Teton River tributaries. The north-oriented Teton River tributary valleys were eroded by reversals of flood flow on north ends of south oriented flood flow channels beheaded by headward erosion of the Teton River valley. The south oriented flood flow was moving to what was then the newly eroded Sun River valley to the south. The North Fork Sun River originates near Sun River Pass (not labeled in figure 2, but located south of Mt May and west of Mt Lockhart) and flows in a south direction to Gibson Reservoir (located along the Teton County south border near the figure 2 southwest corner) where it is joined by the south, east, and north-oriented Middle Fork Sun River and the north-northwest oriented South Fork Sun River to form the east-oriented Sun River. From Gibson Reservoir the Sun River flows for a considerable distance along the Teton County south border before flowing in an east direction across northern Cascade County to join the Missouri River at Great Falls. Several irrigation canals are shown which should not be confused with natural drainage routes. In eastern Teton County Muddy Creek is an important south- and southeast-oriented tributary located south of Teton Ridge. Other tributaries will be encountered on the topographic maps below. The evidence shown below demonstrate the Sun River valley eroded headward across massive south- and southeast-oriented flood flow at a time when the Teton River valley did not exist. Headward erosion of the deep Teton River valley subsequently captured the south- and southeast-oriented flood flow and flood waters on north ends of the beheaded flood flow routes reversed flow direction to erode north-oriented Teton River tributary valleys.

Teton River-Sun River drainage divide area at Teton Ridge

Figure 3: Teton River-Sun River drainage divide area at Teton Ridge. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the Teton River-Sun River drainage divide area at Teton Ridge. Dutton is the town near the north edge of the figure 3 northeast quadrant and Power is the town along the south edge of the figure 3 southeast quadrant. Cordova is the place-name near the figure 3 south center edge. Teton Ridge is labeled and is a prominent west to east oriented ridge slightly north of the figure 3 center and may be composed of erosion resistant bedrock material, although field inspection is needed to be sure. North-oriented drainage north of Teton Ridge flows to the east-oriented Teton River, which is north of the figure 3 map area. South and southeast-oriented drainage located south of Teton Ridge flows to Muddy Creek, which is the south oriented stream flowing to the figure 3 south edge between Cordova and Power. South of the figure 3 map area Muddy Creek flows in a southeast direction to join the east-oriented Sun River. The Teton River-Sun River drainage divide is remarkably well-defined and is located along the Teton Ridge crest. Note how the Teton Ridge crest is uneven with several well-defined north-south oriented through valleys eroded across it. The largest and deepest of these through valleys is used by the highway and railroad between Dutton and Power in the figure 3 east half, although valley’s eastern wall has been largely eroded away and what remains of the east wall is located east of the figure 3 map area. The figure 3 map contour interval is 20 meters and the through valley floor elevation at the drainage divide is between 1120 and 1140 meters. Teton Ridge elevations just south of Dutton rise to more than 1240 meters while east of the figure 3 map area remnants of Teton Ridge rise to more than 1200 meters. In other words this large north-south oriented through valley is at least 60 meters deep and probably was deeper at one time. Another well-defined north-south oriented through valley eroded across Teton Ridge is seen in the figure 3 west half. The floor of this western through valley at the drainage divide has an elevation of between 1200 and 1220 meters. Teton Ridge on either side of this western through valley rises to more than 1260 meters meaning this through valley is at least 40 meters deep. Other shallower through valleys are located between the two mentioned through valleys. Each of these through valleys is a water eroded landscape feature and was eroded by south-oriented flood flow channels at a time when the east-oriented Teton River valley (north of figure 3) did not exist. At that time south-oriented flood flow was initially flowing on a surface at least as high as the Teton Ridge crest today and was flowing to what was then the newly eroded east-oriented Sun River valley. Flood waters eroded deep south- and southeast-oriented flood flow channels headward from the newly eroded Sun River valley north wall and some of these flood flow channels eroded headward across the present day Teton Ridge location. Headward erosion of the deep Teton River valley subsequently beheaded the south-oriented flood flow channels and flood waters on the north ends of the beheaded flood flow channels reversed flow direction to erode north-oriented Teton River tributary valleys and to erode the north-facing Teton Ridge slope.

Detailed map of Hunt Coulee-Muddy Creek drainage divide area

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

Figure 4 provides a detailed topographic map of the Hunt Coulee-Muddy Creek drainage divide area seen in less detail in figure 3 above. This is the eastern through valley seen in figure 3 and is the through valley used by both the highway and railroad, which can be seen just west of the figure 4 center. Teton Ridge is labeled in the figure 4 west center area (west of the highway and railroad). Hunt Coulee is the stream originating near the curve in the highway as a southeast-oriented stream in section 25 and turning the section 30 northwest corner (just east of curve in highway) to flow in a north and north-northeast direction to the figure 4 north edge (west of center). North of the figure 4 map area Hunt Coulee drains to the east-oriented Teton River. South-oriented drainage in section 36 and flowing to the intermittent lake in section 1 is a discontinuous drainage route, but is linked by a through valley to south oriented drainage to Muddy Creek, which then flows to the east-oriented Sun River. The figure 4 map contour interval is ten feet and the through valley floor elevation at the drainage divide (just south of the figure 4 map area) is between 3710 and 3720 feet. Teton Ridge to the west reaches at least 4080 feet along the figure 4 west edge. Elevations greater than 3890 feet can be seen in the figure 4 southeast corner region and north and east of the figure 4 map area a hill reaches at least 3940 feet. Further east there are hills rising to more than 4000 feet. These elevations suggest the north-south oriented through valley is at least 220 feet deep and probably was much deeper when initially eroded. The through valley is a major topographic feature as is Teton Ridge, which is today the drainage divide. These are erosional landforms which must be explained and which were eroded during massive south- and southeast-oriented floods which flowed across the region to what was then the actively eroding and deep east-oriented Sun River valley. Flood waters eroded deep south-oriented flood flow channels headward from the newly eroded Sun River valley north wall into a surface at least as high as the highest Teton Ridge elevations today (the deep Sun River valley was eroding headward into that same high level topographic surface). Apparently the Teton Ridge composition is more resistant to erosion than bedrock material to the north and south and south-oriented flood waters deeply eroded the region to the south. Headward erosion of the deep east-oriented Teton River next beheaded the south-oriented flood flow routes in sequence from east to west. Flood waters on north ends of beheaded flood flow routes reversed flow direction to erode north-oriented Teton River tributary valleys. Because flood flow routes were beheaded in sequence from east to west newly beheaded and reversed flood flow routes could capture south-oriented flood flow from yet to be beheaded flood flow routes further to the west. These captures of flood flow provided the water volumes and movements required to erode the north-facing Teton River valley slope and the north-oriented Teton River tributary valleys.

Teton River-Muddy Creek drainage divide area

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

Figure 5 illustrates the Teton River-Muddy Creek drainage divide area west and slightly south of the figure 3 map area and includes overlap areas with figure 3. Choteau is the town in the figure 5 northwest corner. The Teton River flows in an east direction just south of Choteau and then turns to flow in a northeast direction to the figure 5 north edge (west half). North of the figure 5 map area the Teton River turns to flow in more of an east direction (see figures 1 and 2). Teton Ridge can be seen in the figure 5 northeast corner area and Bole Bench is the upland region to the south in the figure 5 east center region. Between Teton Ridge and Bole Bench is northwest-southeast oriented TL Gap which is a through valley linking the northeast-oriented Teton River valley with the southeast oriented valley of a southeast oriented Muddy Creek tributary, which flows to the figure 5 east edge (north half). Muddy Creek as seen in figure 2 flows to the east-oriented Sun River. Freezeout Lake is the lake along the figure 5 south edge just west of the where the highway crosses the figure 5 south center edge. The east-oriented drainage at Cleiv (a place-name in the figure 5 southeast quadrant) flows to Muddy Creek and the Sun River. Freezeout Lake is located in a large north-south oriented through valley linking the Teton River valley to the north with the east-oriented Muddy River tributary valley to the southeast and also a higher level north-south through valley to the Sun River valley south of the figure 5 map area. The TL Gap through valley and the Freezeout Lake through valley are water eroded features and were eroded by massive south and southeast-oriented flood flow prior to headward erosion of the deep Teton River valley. Teton Ridge in the figure 5 northeast quadrant rises to 1280 meters while elevations along the figure 5 west edge rise to more than 1300 meters (the figure 5 map contour interval is 20 meters in the east half and 50 meters in the west half). Elevations on the Freezeout Lake through valley floor at the Teton River-Muddy Creek drainage divide (at Eastham Junction) appear to be approximately 1150 meters meaning the Teton River-Muddy Creek through valley is at least 130 meters deep. The TL Gap through valley between Teton Ridge and Bole Bench has an elevation at the drainage divide of between 1180 and 1200 meters with Teton Ridge to the north rising to at least 1280 meters and Bole Bench to the south rising to at least 1240 meters. While not as deep or as broad as the Freezeout Lake through valley the TL Gap through valley is a well-defined through valley at least 40 meters deep. Both of these major through valleys were eroded by massive southeast- and south-oriented flood flow prior to headward erosion of the deep Teton River valley. Headward erosion of the deep Teton River valley captured the southeast- and east-oriented flood flow and diverted the water in a northeast and east direction more directly to the what was then the newly eroded Missouri River valley. At the same time flood waters on north and northwest ends of beheaded flood flow routes reversed flow direction to erode north- and northwest-oriented Teton River tributary valleys.

Detailed map of Teton River-Muddy Creek drainage divide area at TL Gap

Figure 6: Detailed map of Teton River-Muddy Creek drainage divide area at TL Gap. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 provides a detailed topographic of the Teton River-Muddy Creek drainage divide at TL Gap seen in less detail in figure 5. Teton Ridge is labeled and is the high ridge located in the figure 6 northeast quadrant and as seen in earlier figures extends in an east direction beyond the figure 6 map area. Bole Bench is located in the figure 6 southwest quadrant and as seen in figure 5 extends in a south direction beyond the figure 6 map area. TL Gap is located in sections 34 and 35 near the figure 6 center and is a through valley linking a northwest-oriented Teton River tributary valley with a southeast-oriented Muddy Creek tributary valley. The figure 6 map contour interval is 10 feet and the TL Gap elevation at the drainage divide is between 3830 and 3840 feet. Elevations on Bole Bench near the figure 6 southwest corner rise to at least 4100 feet while elevations on Teton Ridge rise to more than 4200 feet. Based on the Bole Bench elevation the TL Gap through valley is at least 260 feet deep. TL Gap is a water eroded valley and Bole Bench and Teton Ridge are erosion residuals after water erosion of surrounding regions meaning at one time the surface in the figure 6 map area was at least as high as the present day highest elevations. The TL Gap through valley was probably eroded into that high level surface by southeast-oriented flood waters, which initially flowed on the high level surface. Volumes of water involved must have been great to be able to erode the Bole Bench surface, which is approximately 100 feet lower than the Teton Ridge surface. Further, volumes of flood waters were great enough to erode the deep TL Bench through valley. At that time the deep Teton River valley to the north and northeast did not exist. Headward erosion of the deep Teton River valley beheaded the southeast-oriented flood flow channel moving flood waters through TL Gap to what was then the actively eroding Muddy Creek valley. Flood waters on the northwest end of the beheaded flood flow channel reversed flow direction to erode the northwest-oriented Teton River tributary valley. Volumes of flood water eroding the region in the figure 6 northwest corner area, where elevations are almost 150 feet lower than the TL Gap drainage divide elevation, must also have been great. Flood waters eroding the figure 6 northwest corner area were probably derived from yet to be beheaded south and southeast-oriented flood flow still moving west of what was then the actively eroding Teton River valley. These south and southeast-oriented flood waters were captured by the reversed flow on the newly beheaded and reversed TL Gap flood flow channel and deeply eroded what is now the southeast side of the deep Teton River valley in the figure 6 northwest corner.

Teton River-Willow Creek drainage divide area

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

Figure 7 illustrates the Teton River-Willow Creek drainage divide area west and slightly north of the figure 5 map area and includes a small overlap area with figure 5. Choteau is the town located near the figure 7 east center edge. The Teton River can just barely be seen flowing in an east direction along the north edge of the figure 7 northwest quadrant and then turns to flow in a southeast direction to the figure 7 east edge (south of Choteau). Hod Main Coulee is an east-northeast oriented tributary originating in the figure 7 northwest quadrant and joining the Teton River just east of the figure 7 north center area. Spring Creek is the southeast-oriented Teton River tributary flowing parallel to the Teton River and flowing through Choteau and joins the Teton River just east of the figure 7 map area. Willow Creek is another Teton River tributary and flows in a southeast direction from the figure 7 west center edge almost to the figure 7 south edge and then turns to flow in an east-northeast and north direction to join the Teton River near of the figure 7 east edge (just south of Choteau). Teton Buttes are high points in the figure 7 center region and could be considered a western extension of Teton Ridge seen in earlier figures. The figure 7 map contour interval is 50 meters and spot elevations indicate the two highest points in the Teton Buttes area reach 1458 and 1484 meters. West of the highest Teton Butte elevations and south of the Hod Main Coulee headwaters is another high point marked with a spot elevation of 1476 meters. Between that 1476 meter high point and the 1486 meter Teton Buttes high point are headwaters of southeast-oriented Dog Creek, which joins Willow Creek in the figure 7 southeast quadrant. Note how the Dog Creek headwaters are linked by a through valley with a north-oriented Hod Main Coulee tributary. The through valley floor elevation at the drainage divide is between 1300 and 1350 meters meaning the through valley is at least 120 meters deep. The through valley provides evidence of a large southeast-oriented flood flow channel prior to headward erosion of the deep east-oriented Teton River valley and its tributary Hod Main Coulee valley. West of the 1476 meter high point is another somewhat shallower north-south oriented through valley and is used by a north-south oriented road. Further west and seen in figure 8 is a large northwest-southeast oriented through valley linking the east-oriented Teton River valley with the southeast-oriented Willow Creek headwaters valley. These through valleys provide evidence of anastomosing (diverging and converging) flood flow channels that once crossed the region. At that time headward erosion of the deep Teton River valley had not yet captured the southeast-oriented flood flow and flood waters flowed in south and southeast directions to join the newly eroded Sun River valley (south of the figure 7 map area) and/or to what was then the actively eroding northeast-oriented Teton River valley located east of Chouteau.

Detailed map of Teton River-Willow Creek drainage divide area

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

Figure 8 is a reduction of a detailed topographic map of the Teton River-Willow Creek drainage divide area just west of the figure 7 northwest quadrant and includes overlap areas with areas seen in less detail in the figure 7 northwest quadrant. The Teton River flows in an east direction along the north edge of the figure 8 northwest quadrant and then north of the figure 8 northeast quadrant. Hod Main Coulee originates near the figure 8 center and drains in an east-northeast direction to the figure 8 east edge (north half). Pine Butte is labeled and is the northwest-southeast oriented butte located near the figure 8 west center edge. Willow Creek originates along the figure 8 west edge north of Pine Butte and flows in southeast direction along the Pine Butte east side to the figure 8 south center edge. As seen in figure 7 south and east of the figure 8 map area Willow Creek eventually joins the Teton River. Note how the southeast-oriented Willow Creek valley is linked by a large through valley with the east-oriented Teton River valley. In fact there is almost no drainage divide between the two drainage routes. The figure 8 map contour interval is 20 feet and in places the rise between the Teton River valley elevation (about 4600 feet) and the Willow Creek headwaters valley elevation (also about 4600 feet) is shown by only one contour line. Yet further east the two diverging drainage routes, which later converge, are separated by several miles and by upland regions with high buttes rising to 4841 feet in section 15 and 4893 feet in section 24. Between those two high buttes there is in section 14 a northeast-southwest oriented through valley with a floor at the drainage divide of between 4600 and 4620 feet, which links the east-northeast oriented headwaters of Hod Main Coulee with the southeast-oriented Willow Creek valley. This through valley suggests at one time southeast-oriented flood flow in what was at that time the diverging Willow Creek flood channel split into two diverging flood flow channels with one continuing on the present day Willow Creek alignment while the other extended in a northeast and east-northeast direction along the Hod Main Coulee alignment, which also converged with the east-oriented Teton River flood flow channel. The diverging and converging flood flow channels defined by the present day through valleys provides evidence of a large-scale east-oriented anastomosing channel complex which once crossed the region. The immense east-oriented floods responsible for eroding these anastomosing flood flow channels were coming from the west, which is today a region of high mountains and the east-west continental divide. Flood waters appear to have initially flowed on a surface at least as high as the highest figure 8 elevations today and were responsible for eroding all lower regions. How much erosion occurred in the figure 8 map area before a surface defined by the high elevations today was reached cannot be determined because there are no higher markers, but it is possible significant thickness of bedrock material were removed prior to reaching that surface.

Deep Creek-Sun River drainage divide area

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

Figure 9 illustrates the Deep Creek-Sun River drainage divide area south and somewhat west of the figure 7 map area and includes overlap areas with figure 7. The Rocky Mountain front is located along the figure 9 west edge and west of figure 9 are high mountains. The Sun River flows in an east-northeast direction from the figure 9 southwest corner and then turns to flow in a southeast direction to the figure 9 south edge (east half). Deep Creek flows in an east direction across the figure 9 north half and east of the figure 9 map area joins Willow Creek. Remember Willow Creek is a Teton River tributary so the Deep Creek-Sun River drainage divide seen in figure 9 is also the drainage divide between the Teton River drainage basin and the Sun River drainage basin. Hay Coulee seen near the north edge of the figure 9 northeast quadrant is a Deep Creek tributary. Quigley Coulee is an east-northeast oriented Deep Creek tributary originating near Pishkun Reservoir. Most drainage routes leading to and from Pishkun Reservoir are irrigation canals and natural drainage routes are somewhat obscured, although the east-northeast oriented through valley linking the east-northeast oriented Sun River valley segment with the Pishkun Reservoir basin and the east-northeast oriented Quigley Coulee valley is a natural water eroded feature, which was eroded by massive east-oriented flood flow moving in what must have been a diverging flood flow channel from what was at that time an actively eroding Sun River valley. The figure 9 map contour interval is 50 meters and the Pishkun Reservoir elevation is shown as 1324 meters. The Sun River valley at the elbow of capture (where it turns to flow in a southeast direction) elevation is between 1250 and 1300 meters and no elevations greater than 1350 meters are shown between the Sun River valley and Pishkun Reservoir. While Quigley Coulee is not a Pishkun Reservoir outlet it is a natural east-northeast oriented valley leading from the Pishkun Reservoir basin area to the Deep Creek valley. Elevations in the figure 9 southeast corner area rise to at least 1450 meters and elevations west of Pishkun Reservoir rise even higher, meaning the east-northeast oriented through valley is at least 100 meters deep. This large east-northeast oriented through valley documents former linkages between what are now Teton River tributaries and the Sun River valley. Headward erosion of the northeast-oriented Teton River valley east of Choteau and the northeast-oriented Willow Creek valley segment seen in the figure 7 southeast quadrant captured east-oriented flood flow on the Sun River-Quigley Coulee-Deep Creek flood flow channel probably at a time when it was still a diverging flood flow channel from the Sun River valley flood flow channel. Subsequently deeper erosion of the Sun River valley beheaded flood flow to the east-northeast oriented Quigley Coulee-Deep Creek flood flow channel. Remember the massive east-oriented flood waters that eroded these deep east-oriented flood flow channels came from the mountains to the west, where the east-west continental divide is located near the Sun River headwaters.

Detailed map of Deep Creek-Sun River drainage divide area

Figure 10: Detailed map of Deep Creek-Sun River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 uses a reduced size detailed topographic map to illustrate the Deep Creek-Sun River drainage divide area seen in less detail in figure 9 above. Deep Creek is the east-oriented stream with a forested valley (shown in green) seen along a segment of the figure 10 north edge. The Sun River flows in an east direction from the figure 10 south edge before turning to flow in a northeast and then southeast direction in the figure 10 south center area. The northeast-oriented drainage route from the figure 10 southwest corner to Pishkun Reservoir is the Pishkun Canal and cuts across natural drainage routes such as southeast and south-southeast oriented Arnold Coulee (in figure 10 southwest quadrant). The unlabeled east-oriented stream north of Pishkun Reservoir in the figure 10 northeast quadrant is Quigley Coulee. Split Rock Lake is the smaller labeled lake located between the northeast-oriented Sun River valley segment and Pishkun Reservoir. The southeast-oriented drainage route from Pishkun Reservoir to the figure 10 southeast corner is the Sun River Canal, which is another irrigation canal. Note between the Sun River Canal and the southeast-oriented Sun River valley segment a region of hummocky topography where at least some of the low hills are streamlined in a northwest to southeast direction. This area of low streamlined hills was probably eroded by massive southeast-oriented flood flow at the time the deep east-oriented Sun River valley beheaded the diverging east-northeast oriented Sun River-Pishkun Reservoir-Quigley Coulee flood flow channel, which at one time carried flood water to the east-oriented Deep Creek valley. At that time the Deep Creek valley probably split into diverging flood flow channels east of the figure 10 map area with one channel leading back to the east-oriented Sun River flood flow channel while the other channel led to what was then the actively eroding Teton River valley (or flood flow channel). The figure 10 map contour interval is 20 feet and elevations in the Sun River-Pishkun Reservoir drainage divide area are in the 4320 to 4340 foot range or lower. An elevation greater than 4840 feet can be seen on the west end of a high bench seen along the figure 10 east edge (south half). Elevations greater than 5000 feet can be found along the figure 10 west edge. These elevations indicate the east-northeast oriented Sun River-Pishkun Reservoir-Quigley Coulee-Deep Creek flood flow channel was at least 460 feet deep. The southeast-oriented Sun River valley was eroded at least as deep meaning immense volumes of east-oriented flood waters were moving in the Sun River valley as the Sun River emerged from the Rocky Mountains to the west. To understand where these immense volumes of flood waters were coming from please go to the Teton River-Sun River drainage divide area landform origins essay, western Teton County, Montana essay, which addresses the Teton River-Sun River drainage divide area in the mountains (see Teton River category on sidebar category list).

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.