Milk River-Marias River drainage divide area landform origins, Sweet Grass Hills, Toole and Liberty Counties, Montana, USA

Authors

Abstract:

Topographic map interpretation methods are used to determine landform origins in the Milk River-Marias River drainage divide area located in the Sweet Grass Hills of northern Toole and Liberty Counties, Montana. The Sweet Grass Hills are located just south of the Canadian border in north central Montana and consist of East Butte, Middle Butte, and West Butte, each of which stands more than 1000 meters above the surrounding plains. The Milk River flows in an east direction to the north in southern Alberta while the Marias River flows in an east direction to the south of the Sweet Grass Hills. North-oriented streams originating in the Sweet Grass Hills region flow to the Milk River while south-oriented streams flow to the Marias River. These opposing drainage routes are today linked by continuous through valleys some of which cross high level ridges in the East and West Butte upland areas. The through valleys and elbows of capture provide evidence of multiple south-oriented anastomosing flood flow routes which once flowed on a surface as high as the tops of the highest East and West Butte peaks. Flood flow is interpreted to have been melt water from a rapidly melting thick North American ice sheet, which had been located in a deep “hole.”Easily eroded bedrock surrounding the high Sweet Grass Hills erosion resistant rock masses was removed as ice-marginal melt water floods deeply eroded the deep “hole’s” southwest wall. Topographic map evidence also suggests the Sweet Grass Hills drainage divide was uplifted as south-oriented flood flow moved across the region and headward erosion of the deep east-oriented Milk River valley to the north beheaded and reversed the south-oriented flood flow.

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 Milk River-Marias River drainage divide area landform origins, Sweet Grass Hills, Toole and Liberty 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 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 leaving a comment here with a link to those essays.
  • 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 Milk River-Marias River drainage divide area landform evidence, Sweet Grass Hills, Toole and Liberty Counties, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm (see paradigm related essay in menu at top of page). This essay is included in the Missouri River drainage basin landform origins research project essay collection.

Milk River-Marias River drainage divide area location map

Figure 1: Milk River-Marias 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 illustrates a location map for the Milk River-Marias River drainage divide area in the Sweet Grass Hills of Toole and Liberty Counties, Montana and shows a region of north central Montana with Alberta and the Saskatchewan southwest corner located north of the west to east oriented United States-Canada border. The Missouri River flows in a northeast direction from Great Falls (near figure 1 south center edge) to Fort Benton and Loma and then turns to flow in a southeast and east-northeast direction south of the Bears Paw Mountains to the figure 1 east edge. The Marias River is formed at the confluence of Cut Bank Creek and Two Medicine River south of Cut Bank, Montana and then flows in an east-southeast direction to Lake Elwell, a large reservoir impounded behind Tiber Dam. From Tiber Dam the Marias River flows in an east, south, and southeast direction to join the Missouri River near Loma. Named Marias River tributaries flowing to Lake Elwell are south-oriented Eagle Creek and south-southeast oriented Willow Creek. Eagle Creek originates near East Butte and Willow Creek originates near West Butte, both of which are just south of the United States-Canada boundary. West Butte and East Butte represent two of the three major buttes in the Sweet Grass Hills area of northern Toole and Liberty Counties, Montana. Note the similarity of elevations for high points at East Butte (2121 meters) and West Butte (2128 meters) suggesting tops of these independent butte areas may record a former erosion surface. The North and South Forks of the Milk River originate on the east edge of the Unites States section of the Waterton-Glacier International Peace Park and flow in a northeast direction into southern Alberta where they join to form the east-oriented Milk River which flows across southern Alberta just north of the Sweet Grass Hills. Near the Alberta southeast corner the Milk River turns to flow in a southeast direction to Havre, Montana and then flows in an east direction to the figure 1 east edge. East of the figure 1 map area the Milk River joins the Missouri River and water eventually reaches the Gulf of Mexico. Between south-oriented Eagle Creek and the southeast-oriented Milk River segment upstream from Havre is southeast-oriented Sage Creek, which also has headwaters near East Butte. The Sage Creek-O’Brien Coulee drainage divide area landform origins essay discusses the region immediately east of the Milk River-Marias River drainage divide area discussed in this essay. Essays for other regional drainage divide areas can be found listed under Milk River and Marias River on the sidebar category list.
  • The Sweet Grass Hills consist of three high butte areas which stand more than 1000 meters above the surrounding plains. In addition to East and West Buttes there is a Middle Butte (also known as Gold Butte), which has a slightly lower elevation (1986 meters). As will be seen in the topographic maps illustrated below each of the buttes, especially East and West Butte, actually consists of several closely spaced buttes with the high elevations given here referring to highest butte in each butte cluster. The Milk River-Marias River drainage divide is located in and/or near of each of the three butte areas, with Marias River tributaries draining in a south direction and Milk River tributaries draining in a north direction. However, as seen in the illustrated topographic maps the drainage divide is not simple and many complexities are found. The Sweet Grass Hills area was deeply eroded by immense south-oriented melt water floods from a rapidly melting thick North American ice sheet, which had been located in a deep “hole.” The ice sheet had formed on a topographic surface which today is preserved, if it is preserved at all, on the highest level Rocky Mountain erosion surfaces. Those high-level Rocky Mountain erosion surfaces today have elevations much higher than the tops of the Sweet Grass Hills buttes and it is probable both the Rocky Mountains and the Sweet Grass Hills were uplifted while massive melt water floods flowed across them and the elevations seen today are very different from elevations present as the ice sheet was melting. The deep “hole” in which the ice sheet was located was formed by a combination of deep glacial erosion and of crustal warping caused by ice sheet’s great weight. Today the Montana and northern Wyoming upper Missouri River drainage basin drains the deeply eroded deep “hole’s” southwest wall. Evidence investigated in this essay documents south-oriented melt water floods across the Sweet Grass Hills area and also documents uplift of the Sweet Grass Hills area as melt water floods were flowing across the region. Headward erosion of the east-oriented Milk River valley in southern Alberta was aided by Sweet Grass Hills region uplift, which caused massive flood flow reversals to erode north-oriented Milk River tributary valleys and to create the Milk River-Marias River drainage divide.

Detailed location map for Milk River-Marias River drainage divide area

Figure 2: Detailed location map for Milk River-Marias 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 Milk River-Marias River drainage divide area in the Sweet Grass Hills area of northern Toole and Liberty Counties, Montana. County lines and names are shown. The United States-Canada border is located along the figure 2 north edge. The Sweet Grass Hills are located in the Toole County northeast corner and the Liberty County northwest corner and consist of East Butte, Gold Butte, and West Butte. Figure 2 elevations are given in feet and the East Butte elevation is 6958 feet, the Gold Butte elevation is 6512 feet, and the West Butte elevation is 6983. Note the remarkable similarity of the East and West Butte elevations. The Milk River flows in an east direction in southern Alberta just north of the international border and then turns to flow in a southeast direction across the figure 2 northeast corner. North-oriented drainage routes flowing to the figure 2 north edge are Milk River tributaries. Named north-oriented Milk River tributaries in the Sweet Grass Hills region are Bear Creek and Breed Creek. The Marias River flows in an east-southeast direction from the figure 2 west edge (just south of center) to Lake Elwell (or Tiber Reservoir). From Tiber Dam the Marias River flow in an east-southeast direction to the Hill County southwest corner region and then turns to flow in a south direction to join the Missouri River south of the figure 2 map area. Named south oriented Marias River tributaries originating in the Sweet Grass Hills region are Cottonwood Creek, Eagle Creek, and Willow Creek. Horse Creek is a named Cottonwood Creek tributary. Eagle Creek has no tributaries shown. Willow Creek named tributaries originating in the Sweet Grass Hills area are Kinyon Coulee, Trail Creek, and Greens Coulee. An interesting unnamed Willow Creek tributary originating between West Butte and Gold Butte is Miners Coulee, which will be seen in more detail in figures 7, 8, and 9 below. Note how most Marias River tributaries from the north are oriented in south and southeast directions. The Marias River valley originated as an east-southeast and east oriented valley extending to the Lonesome Prairie region near the figure 2 southeast corner. This early Marias River valley eroded headward and captured massive south and southeast-oriented melt water flowing across the entire figure 2 map region. At that time the east-oriented Milk River valley to the north of figure 2 did not exist. As what was then the deep Marias River valley eroded headward across the region flood waters on north ends of beheaded flood flow routes reversed flow direction to erode north-oriented Marias River tributaries. Apparently south-oriented flood flow in the present day south-oriented Marias River valley segment did not reverse flow direction, but had already eroded a deep enough valley that flood waters continued to flow south and in time captured the upstream Marias River drainage basin. Headward erosion of the deep east-oriented Milk River valley north of the figure 2 map area repeated the process by capturing the south- and southeast-oriented flood flow moving to what were then actively eroding Marias River tributary valleys and flood waters on north ends of beheaded flood flow routes reversed flow direction to erode north-oriented Milk River tributary valleys.

Breed Creek-Cottonwood Creek drainage divide area

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

 

  • Figure 3 illustrates the Breed Creek-Cottonwood Creek drainage divide area at East Butte. East Butte has two high “peaks” consisting of Mount Brown (elevation 2121 meters) and Mount Royal (elevation 2107 meters) plus several other somewhat lower “peaks” including an unnamed  “peak” a short distance southeast of Mount Royal. Two “peaks” with elevations in the 2007 to 2121 meters range (plus the West Butte peak elevation of 2128 meters) suggests there may have been an erosion surface at that level, although today the  “peaks” stand more than 1000 meters higher than much of the surrounding region. Sage Creek originates on the east side of the pass between Mount Brown and Mount Royal and flows in a north-northeast, east, southeast, and northeast direction to the figure 3 north edge (near northeast corner). North and east of the figure 3 map area Sage Creek turns to flow in a southeast direction to join northeast oriented Big Sandy Creek as seen in figure 1. Breed Creek originates on the west side of the pass between Mount Brown and Mount Royal and flows in a northwest, southwest and north-northwest direction to the figure 3 north edge (west half) and continues into Alberta where it joins the east-oriented Milk River. The figure 3 map contour interval is 20 meters and the elevation of the pass between Mount Brown and Mount Royal is between 1900 and 1920 meters, which means the pass is approximately 200 meters lower than the Mount Brown and Mount Royal peak elevations. This pass is actually a through valley linking the Breed Creek and Sage Creek valleys and was eroded by south and/or southeast oriented melt water floods flowing across what must have been a rising East Butte erosion resistant bedrock mass. The south-oriented stream flowing to the figure 3 south center edge (near McGuire Hill) is Corral Creek. East of Corral Creek is south-oriented Government Creek and its tributaries Tootsie Creek, Mc Tosh Coulee, and Snoose Coulee. South of the figure 3 map area Corral Creek and Government Creek join to form south-oriented Cottonwood Creek, which flows to the Marias River. Note how Tootsie Creek originates as a northeast- and southeast-oriented stream before turning to flow in a south direction to join Government Creek. On the northwest side of the elbow capture, where Tootsie Creek turns to flow in a southeast direction, is a pass or through valley linking the southeast-oriented Tootsie Creek valley with the north-northeast oriented Sage Creek valley to the northwest. The pass elevation is between 1660 and 1680 meters with elevations rising to more 1780 meters to the northeast and rising much higher to the southwest. The pass or through valley is another former flood flow channel eroded prior to headward erosion of the deep north-northeast oriented Sage Creek valley. For reference in future figures the unnamed south-oriented stream just west of Haystack Butte in the figure 3 southwest quadrant is Eagle Creek.

Detailed map of Breed Creek-Cottonwood Creek drainage divide area

Figure 4: Detailed map of Breed Creek-Cottonwood 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 Breed Creek-Cottonwood Creek drainage divide area near Mount Brown and Mount Royal which was seen in less detail in figure 3 above. Figure 4 elevations are given in feet and the contour interval is 20 feet. Mount Brown is located just south of the figure 4 north center edge and reaches an elevation of 6958 feet. Mount Royal is located south of Mount Brown in the section 30 northwest corner and reaches an elevation of 6914 feet. Sage Creek headwaters are located in section 19 on the east side of the through valley eroded between Mount Brown and Mount Royal. Breed Creek headwaters are located in section 24 on the west side of the through valley between Mount Brown and Mount Royal. The through valley floor elevation at the drainage divide is between 6260 and 6280 feet suggesting the through valley is more than 600 feet deep. As previously described the through valley was eroded by south and/or southeast oriented flood flow moving to what was then the actively eroding Sage Creek valley. Erosion of this deep valley began at a time when melt water floods were flowing on a surface at least as high as the tops of Mount Brown and Mount Royal today. Another high-level through valley linking the Breed Creek headwaters with south-oriented Corral Creek, which flows to Cottonwood Creek which in turn flows to the Marias River, is found just south of Mount Royal near the line between sections 25 and 30. Northwest-oriented Ribbon Gulch originates in section 25 and joins Breed Creek west of the figure 4 map area (remember west of the figure 4 map area Breed Creek turns to flow in a northwest and north direction to join the east-oriented Milk River in Alberta). Corral Creek originates in section 30. The through valley linking the northwest-oriented Ribbon Gulch valley with the south-oriented Corral Creek valley has an elevation of between 6320 and 6340 feet at the drainage divide. Elevations of the unnamed high point to the south rise to more than 6400 feet while Mount Royal rises to 6914 feet. While more subtle than the Breed Creek-Sage Creek through valley this Ribbon Gulch-Corral Creek through valley was another southeast and/or south oriented flood flow route across the East Butte region. Further east in section 30 is another interesting through valley linking the north-northeast oriented Tootsie Creek headwaters with the south-oriented Corral Creek valley. The floor of this Tootsie Creek-Corral Creek through valley is between 6140 and 6160 feet at the drainage divide and the unnamed “peak” to the southeast rises to 6566 feet. In other words the Tootsie Creek-Corral Creek through valley is at least 400 feet deep. Today both Tootsie Creek and Corral Creek flow to south-oriented Cottonwood Creek, which means headward erosion of the southeast-oriented Tootsie Creek valley seen in section 20 captured a south-oriented flood flow channel and flood waters on the southwest end of that beheaded flood flow channel reversed flow direction to erode the north-northeast oriented Tootsie Creek headwaters valley.

Breed Creek-Strawberry Creek drainage divide area

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

 

  • Figure 5 illustrates the Breed Creek-Strawberry Creek drainage divide area west of the figure 3 map area and includes overlap areas with figure 3. East Butte can be seen near the east edge of the figure 5 northeast quadrant. Middle Butte is located west of East Butte in the figure 5 northwest quadrant with Gold Butte being the highest point in the Middle Butte.  Middle Butte is a relatively small mass, which reaches an elevation of 1985 meters, which is lower, but still close to the elevations of Mount Brown (2121 meters) and Mount Royal (2107 meters) considering elevations in the figure 5 southwest corner are less than 1100 meters. Between East Butte and Middle Butte is a region of hummocky topography, which based on the figure 5 map evidence could be considered a glacial moraine area. However, evidence that large south-oriented melt water floods crossed the region suggest other possibilities as well. One possibility is the large melt water floods late during the ice sheet melt down history rafted numerous icebergs containing glacially transported debris with the icebergs becoming stranded in the rising Sweet Grass Hills region as headward erosion of the deep east-oriented Milk River valley to the north aided by continuing uplift in the Sweet Grass Hills region caused south-oriented flood flow on north ends of beheaded flood flow to reverse flow direction and to flow in a north direction. Breed Creek can be seen in figure 5 originating just west of the through valley between Mount Brown and Mount Royal near the east edge of the figure 5 northeast quadrant. Note how west of the East Butte upland area Breed Creek turns to flow in a north-northwest direction to the figure 5 north edge (and to join the east-oriented Milk River north of the figure 5 map area). Strawberry Creek originates in the figure 5 east center area (just south of where northwest-oriented Ribbon Gulch joins a southwest-oriented Breed Creek valley segment) and then flows in a southwest direction to the figure 5 south edge (west half). South of figure 5 Strawberry Creek joins a south-oriented Trail Creek, which then joins south-oriented Willow Creek, which flows to the Marias River. Note how the region between East Butte and Middle Butte is the north-south drainage divide between north-oriented streams flowing to the east-oriented Milk River and south-oriented streams flowing to the Marias River. In a sense this region between the two buttes could be considered a huge through valley eroded by south-oriented melt water floods, which were beheaded and reversed by headward erosion of the east-oriented Milk River valley to the north. This interpretation requires deep erosion of easily eroded bedrock material surrounding the erosion resistant East Butte and Middle Butte rock masses. Based on present day elevations it appears more than 1000 meters of surrounding bedrock material was removed. However, the depth of the surrounding bedrock erosion may have been less as in figures 7 and 8 there is evidence the Sweet Grass Hills butte region was being uplifted as flood waters flowed across it.

Detailed map of Breed Creek-Strawberry Creek drainage divide area

Figure 6: Detailed map of Breed Creek-Strawberry 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 Breed Creek-Strawberry Creek drainage divide area on the west side of East Butte, which was seen in less detail in figure 5 above. Breed Creek flows in a southwest, west, and north direction from the figure 6 north edge (east half) to the figure 6 north center edge. Ribbon Gulch drains in a northwest direction from the figure 6 east edge 9, north of center) to join southwest-oriented Breed Creek in section 22 just north of Booster Ridge. Strawberry Creek originates in section 27 on the south side of Booster Ridge and flows in a southwest direction to the figure 6 south edge (west half). Snow Coulee is a south-southwest oriented Strawberry Creek tributary originating in section 33 and joining Strawberry Creek south and west of the figure 6 map area. Note how in section 33 headward erosion of the deeper Strawberry Creek valley has beheaded southwest-oriented flood flow to the Snow Coulee valley. East of Snow Coulee is west-southwest and south-southwest oriented Eagle Creek, which originates in section 26 (near figure 6 east edge) and flows to the figure 6 south edge (east of center). Note in section 26 the through valley eroded across the ridge separating the northwest-oriented Ribbon Gulch valley from the southwest-oriented Eagle Creek headwaters valley. The map contour interval is 20 feet and the through valley floor elevation is between 5140 and 5160 feet. A spot elevation of 5243 feet is shown northwest of the through valley while elevations rise much higher to the southeast. The through valley is at least 80 feet deep and documents a former southwest-oriented flood flow channel which was beheaded by headward erosion of the deep northwest-oriented Ribbon Gulch valley. Think about where the flood water came from that eroded the deep northwest-oriented Ribbon Gulch valley. At that time south-oriented flood waters had to be flowing on a surface higher than the high East Butte ridges, which means much of the region north of East Butte had not yet been eroded. Again, uplift of the East Butte area as flood waters flowed across it could have also been occurring, which could mean regional erosion was less than present day elevations might suggest.

Miners Coulee drainage divide area

Figure 7: Miners Coulee drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 7 illustrates the Miners Coulee drainage divide area between Middle Butte and West Butte located west and north of the figure 5 map area and includes overlap areas with figure 5. The Montana-Alberta border is located just north of the figure 7 map area. The Middle Butte upland region is located in the figure 7 southeast quadrant and the West Butte upland area is located in the figure 7 northwest quadrant. The high point on West Butte is shown with a spot elevation of 2129 meters (the map contour interval is 20 meters). The northwest and north-oriented stream draining to the figure 7 north edge (north of the word “West” in “West Butte”) is Deer Creek, with water flowing to the east-oriented Milk River. The northeast, southeast, and northeast-oriented stream originating just north of the West Butte high point and flowing to the figure 7 north edge is Fred and George Creek, with water also flowing to the east-oriented Milk River. These streams will be seen again in figure 10. For purposes of this essay perhaps the most interesting figure 7 feature is northeast-southwest oriented Miners Coulee, which crosses the north-south drainage divide between West Butte and Middle Butte. The Miners Coulee valley is a well-defined through valley eroded across what is today an obvious drainage divide. At the northeast end a stream drains in a northeast and north direction to join Fred and George Creek and then flow to the Milk River north of the figure 7 map area. At the figure 7 north edge this stream is flowing in valley with an elevation of less than 1060 meters and the elevation where Miners Coulee joins the Milk River is approximately 900 meters. At the southwest end of the Miners Coulee valley a southwest and south-oriented stream flows to the figure 7 south edge (west of center) and south of the figure 7 map area joins south-oriented Willow Creek, which flows to the Marias River. Willow Creek joins the Marias River at Lake Elwell, which has a normal pool elevation of 909 meters. At the figure 7 south edge this south-oriented stream is flowing at an elevation of less than 1100 meters. The drainage divide between these two opposing streams has an elevation of between 1140 and 1160 meters. This Miners Coulee valley illustrates on a very modest basis what happened to erode other through valleys seen in this essay. The southwest-oriented Miners Coulee valley was eroded as a south-oriented flood flow channel just before Milk River valley headward erosion beheaded the south-oriented flood flow. At that time elevations north of the present divide were at least as high as the drainage divide and probably higher. Headward erosion of the deep Milk River valley to the north beheaded the south-oriented flood flow. Flood waters on north ends of the beheaded flood flow channels reversed flow direction to erode north-oriented valleys. However, erosion of these north-oriented valleys may have been aided by uplift of the drainage divide area, which could have occurred during and after the flood flow reversal. The continuous Miners Coulee valley may document tens of meters (or more) of Sweet Grass Hills region uplift since the continuous Miners Coulee flood flow channel was eroded.

Detailed map of Miners Coulee drainage divide area

Figure 8: Detailed map of Miners Coulee drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 8 illustrates a detailed topographic map of the Miners Coulee drainage divide area seen in less detail in figure 7 above. Miners Coulee is labeled and is the continuous northeast to southwest oriented through valley extending from the figure 8 north edge (east half) to the figure 8 south edge (west half). Today the drainage divide between a north-oriented stream flowing to the Milk River to the north of figure 8 (in Alberta) and a south-oriented stream flowing eventually to the Marias River to the south of figure 8 is located near the north center of section 2. A bench mark in the valley at the drainage divide is shown as having an elevation of 3755 feet. The map contour interval is 20 feet and a spot elevation of 4083 feet is located in section 34 to the northwest of the valley drainage divide with a spot elevation of 4266 feet near the west edge of the figure 8 northwest quadrant (much higher elevations are found north and west of figure 8). Elevations rise to more than 4319 feet near the figure 8 southeast corner (much higher elevations are found south and east of figure 8). Depending on how the Miners Coulee valley is defined the valley could be considered to be between 200 feet deep and more than 3000 feet deep, although figure 8 evidence only documents a few hundred feet of depth. Note how north of the Miners Coulee drainage divide there is a northeast-oriented stream flowing to the figure 8 north edge where the elevation is less than 3690 feet. Also note how south of the Miners Coulee drainage divide there is a southwest-oriented stream flowing to the figure 8 south edge where the elevation is less than 3700 feet. This through valley when it was eroded was a continuous southwest-oriented flood flow channel with a continuous gradient from the northeast to the southwest. A reversal of flood flow in the north end of the valley did occur after headward erosion of the deep Milk River valley beheaded the south-oriented flood flow channel. The north-oriented stream gradient could have been eroded by the reversed flood flow, although another possibility is the drainage divide also developed as the Sweet Grass Hills region was being uplifted. Sweet Grass Hills region uplift would probably have been taking place as the southwest-oriented flood flow channel was moving flood water across the region and as the deep east-oriented Milk River valley was eroding headward across southern Alberta to the north of figure 8.

Detailed map of Miners Coulee-Sheep Creek drainage divide area

Figure 9: Detailed map Miners Coulee-Sheep Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 9 illustrates a detailed topographic map of the Miners Coulee-Sheep Creek drainage divide area south and west of the figure 8 map area and south of the figure 7 map area. Willow Creek flows in a south-southeast direction from the figure 9 west edge (north of center) to the figure 9 south edge (west half). Miners Coulee drains in a south-southwest direction from the figure 9 north edge (west half) to join Willow Creek in the figure 9 southwest quadrant. Sheep Creek flows in a southwest direction from the figure 9 east edge (near northeast corner) to join Willow Creek near the figure 9 south edge. Hay Coulee is the south-southwest oriented Sheep Creek tributary in the figure 9 northeast corner. Note the large through valley in the region near the corner of sections 27, 28, 33, and 34 linking the Miners Coulee valley with the Sheep Creek valley. The map contour interval is ten feet and the through valley floor elevation at the drainage divide is between 3410 and 3420 feet.  Elevations in section 33 to the west of the through valley rise to 3445 feet while elevations in sections 27 and 34 to the east of the through valley rise even higher. While not deep the through valley is a former south-oriented flood flow channel that diverged from the south-southwest oriented Miners Coulee valley. A somewhat shallower and higher level, although similar, through valley can be seen in section 2 in the figure 9 southeast quadrant. These through valleys and others in the figure 9 map area provide evidence of the massive south-oriented flood flow which once moved across the Miners Coulee drainage divide seen in the valley seen in figures 7 and 8. As flood waters approached the Willow Creek valley, which was eroding headward from the newly eroded Marias River valley, the flood waters diverged into a series of anastomosing channels as seen in figure 9. As seen in figures 7 and 8, at least during final south-oriented flood flow events in the Sweet Grass Hills region, flood waters flowing between West Butte and Middle Butte were concentrated in the Miners Coulee flood flow channel. Note the change in elevation from the present day drainage divide in the Miners Coulee flood flow channel (3755 feet) to where the south-oriented Miners Coulee drainage enters Willow Creek (3356 at Bench Mark). It is possible much of this elevation difference (399 feet) is the result of Sweet Grass Hills uplift was occurring as the Miners Coulee flood flow channel was being eroded.

Detailed map of Deer Creek-Fred and George Creek drainage divide area

Figure 10: Detailed map of Deer Creek-Fred and George Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 10 illustrates a detailed topographic map of the Deer Creek-Fred and George Creek drainage divide area seen in less detail in figure 7 above and shows a region in the north half of the Sweet Grass Hills West Butte upland area. The Alberta-Montana border is just north of the figure 10 map area. The highest point in the West Butte area is located south of the figure 10 map area. Deer Creek originates in the section 13 southeast corner and flows in a north, northwest, and north direction to the figure 10 north edge (north of section 1 in the figure 1 northwest quadrant). North of the figure 10 map area Deer Creek water flows to the east-oriented Milk River in Alberta. Fred and George Creek flows as a north-northeast oriented stream in the west half of section 19 and then turns to flow in a southeast direction to the figure 10 south edge (east half). South and east of figure 10 Fred and George Creek turns to flow in a northeast direction to join the north-oriented Miners Coulee drainage route and to flow to the east-oriented Milk River in Alberta. McDonald Creek is the northeast-oriented stream flowing from the northwest corner of section 18 to the figure 10 north edge (west of figure 10 northeast corner). South-oriented streams originating in sections 23 and 24 (near the figure 10 southwest corner) flow to Willow Creek, which in turn flows to the east-oriented Marias River. Note in the northeast corner of section 24 and northwest corner of section 19 an east-oriented tributary draining to the elbow of capture where north-northeast oriented Fred and George Creek turns to flow in a southeast direction. Further note in the section 24 northeast corner area two through valleys linking the headwaters of that east-oriented tributary valley with the north-oriented Deer Creek headwaters valley. The map contour interval is 20 feet and the through valley floor elevations are between 5240 and 5260 feet and 5280 and 5300 feet. Another through valley in the section 18 southwest corner region links the northeast-oriented McDonald Creek valley with the southeast-oriented Fred and George Creek valley. This section 18 through valley has a floor elevation at the drainage divide of between 5040 and 5060 feet. The high point in section 24 to the southwest is marked as 6102 feet and the high point in the section 18 southeast corner area is 5652 feet. How deep the through valleys are can be debated, although they provide evidence of multiple south-oriented flood flow routes to the southeast-oriented Fred and George Creek valley, which probably at that time was a south-oriented valley being eroded by south-oriented flood flow. Headward erosion of the deep east-oriented Milk River valley in southern Alberta (just to the north of figure 10) beheaded and reversed the south-oriented flood flow routes in sequence from east to west to erode the present day north-oriented drainage routes.

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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