Sage Creek-Milk River drainage divide area landform origins, Hill County, Montana, USA

· Milk River, Montana
Authors

Abstract:

Topographic map interpretation methods are used to determine landform origins in the Sage Creek-Milk River drainage divide area located in Hill County, Montana. The Milk River flows in a southeast and east direction in Hill County and is joined west of Havre, Montana by north-northeast oriented Big Sandy Creek, which flows along the western flank of the Bears Paw Mountain uplift region. Sage Creek is a southeast oriented Big Sandy Creek tributary, which flows west of and roughly parallel to the adjacent southeast-oriented Milk River segment. Sage Creek joins Big Sandy Creek as a barbed tributary. Topographic map evidence reveals multiple through valleys paralleling the southeast-oriented Milk River and Sage Creek valleys, suggesting all southeast-oriented valleys originated as channels in a large-scale southeast and/or south oriented anastomosing channel complex. North ends of some through valleys drain in north directions to the southeast-oriented Milk River and are additional barbed tributaries. Streamlined hills provide evidence of deep south and southeast oriented flood water erosion of the entire region and document deep erosion of at least several hundred meters in some areas. Based on evidence from other essays flood waters are considered to have been ice-marginal melt water floods derived from a rapidly melting thick North American ice sheet. The ice sheet had been located in a deep “hole” and had deep “roots” so as the ice sheet melted flood waters were lowering regions south and west of the decaying ice sheet so those ice margin regional elevations roughly corresponded with the lowering ice sheet surface, which was significantly lower than the surface on which the ice sheet had originally formed.

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 Sage Creek-Milk River drainage divide area landform origins in Hill 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 then by 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 Sage Creek-Milk River drainage divide area landform evidence in Hill County, 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.

Sage Creek-Milk River drainage divide area location map

Figure 1: Sage Creek-Milk 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 Sage Creek-Milk River drainage divide area in Hill County, Montana and shows a region in north central Montana with the Saskatchewan southwest corner and the Alberta southeast corner located north of the east-west oriented United States-Canada border. The Milk River is labeled and flows from the figure 1 west edge (just north of the international border) to Milk River, Alberta and then in an east and southeast direction to Fresno Reservoir in Montana (near figure 1 center). From Fresno Reservoir the Milk River flows in a generally east direction to Havre, Chinook, Harlem and Malta before making a northeast jog and then flowing to the figure 1 east edge. East of the figure 1 map area the Milk River joins the Missouri River with water eventually reaching the Gulf of Mexico. The Missouri River can be seen in figure 1 and flows in a northeast direction from the figure 1 south edge (west half) through Fort Benton and Loma before turning to flow in a southeast direction around the Bears Paw Mountains south margin and then flows in an east direction to Fort Peck Reservoir (seen in figure 1 southeast corner, but not labeled). Big Sandy Creek is a northeast-oriented Milk River tributary flowing along the Bears Paw Mountains west margin. Sage Creek is a southeast-oriented Big Sandy Creek tributary, which begins near East Butte (just south of the international border) and which joins northeast-oriented Big Sandy Creek as a barbed tributary. The Sage Creek-Milk River drainage divide area investigated in this essay is located south and west of the Milk River, north and east of Sage Creek, and is bounded on the north by the international border and on the southeast by Big Sandy Creek. The Milk River-Battle Creek drainage divide area landform origins, Hill County, Montana essay describes the region directly to the east. Regions east of Big Sandy Creek in the Bears Paw Mountains are described in the Big Sandy-Beaver Creek drainage divide area landform origins essay and in the Big Sandy Creek-Birch Creek drainage divide area landform origins essay. Essays can be found by selecting Milk River from the sidebar category list.
  • Before looking at the Sage Creek-Milk River drainage divide area in detail a brief summary of the big picture situation may be useful. The figure 1 map area is located along what at the time the Sage Creek-Milk River drainage divide area was eroded was located near the southwest margin of a rapidly melting thick North American ice sheet. The ice sheet had been located in a deep “hole” and the entire upper Missouri River drainage basin in Montana and northern Wyoming, including the figure 1 map area, is today what remains of that deep “hole’s” southwest wall. The ice sheet initially formed on a topographic surface preserved today, if it is preserved at all, on the highest level Rocky Mountain erosion surfaces. Those high level Rocky Mountain erosion surfaces have probably been uplifted since the ice sheet formation as the deep “hole” was created by a combination of deep glacial erosion and of crustal warping caused by the ice sheet’s great weight. In addition deep melt water flood erosion of (and perhaps deposition in) may have triggered crustal warping, which took place as immense melt water floods flowed across the region. In spite of significant crustal warping, which almost certainly continued to occur as the thick ice sheet was melting, ice-marginal flood erosion deeply eroded the region south and west of the ice sheet’s southwest margin, which is today the upper Missouri River drainage basin in Montana and northern Wyoming. When the ice sheet stood high above the surrounding region ice-marginal melt water floods flowed in south and southeast directions across Montana and northern Wyoming. However, as ice sheet melting continued and the ice sheet surface was lowered (to the level of the surrounding region) melt water floods began to flow in east and northeast directions onto the ice sheet surface (remember, the ice sheet had deep roots which extended well below the surrounding bedrock surface). The east and northeast oriented melt water floods moved to a deep southeast and south-oriented ice-walled canyon carved by a huge supra-glacial meltwater river into the decaying ice sheet surface. In time the ice-walled canyon became a bedrock-floored canyon and detached the ice sheet’s southwest margin. Today the northeast and east-facing Missouri Escarpment in Saskatchewan, North Dakota, and South Dakota is what remains of that ice-walled canyon’s southwest and west wall.
  • How much material was eroded from north central Montana is difficult to determine. A large east and/or northeast-oriented melt water flood river flowed across the high Cypress Hills region which today straddles the southern Saskatchewan-Alberta border. This large east and/or northeast-oriented melt water river then migrated in a downstream direction along the giant ice-walled canyon and crossed what is today the somewhat lower Wood Mountain region in southern Saskatchewan. The east and/or northeast-oriented melt water river then continued to migrate in a downstream direction along the ice-walled canyon and crossed the present day Flaxville surface area in northeast Montana. Finally after migrating further downstream the east and/or northeast-oriented river eroded a deep bedrock valley across what is today the Medicine Lake area of northeast Montana. This bedrock valley was eroded headward from what by that time had become a giant ice-walled and bedrock-floored canyon in northwest North Dakota. From Poplar, Montana to northwest North Dakota this large northeast-oriented valley is today an abandoned valley, which has been blocked by glacial deposits at its northeast end. However west of Poplar, Montana the large east and northeast-oriented valley is today used by the Missouri River, which captured southeast-oriented ice-marginal flood waters, which were flowing on the plains east of the rising Rocky Mountains, and also captured south and southeast-oriented melt water flood waters, which in western Alberta were flowing into valleys west of the rising Rocky Mountain front and then were flowing in a south direction into southwestern Montana where rising Rocky Mountain ranges blocked the southward flood flow and diverted flood waters north and northeast toward the ice sheet margin. Headward erosion of the deep Milk River valley occurred during this final deep melt water flood erosion event and was caused almost entirely by immense southeast-oriented ice-marginal floods from east of the rising Rocky Mountain front. Landforms illustrated in this essay were almost completely eroded during this final melt water flood erosion event, although readers need to be aware there were earlier melt water erosion events which deeply eroded the entire region prior to this final melt water flood erosion event.

Detailed location map for Sage Creek-Milk River drainage divide area

Figure 2: Detailed location map for Sage Creek-Milk 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 Sage Creek-Milk River drainage divide area in Hill County, Montana. The United States-Canada border is located just north of the figure 2 north edge. The Hill County-Liberty County line is located in the western half of figure 2 and the counties are labeled. The Milk River is labeled and flows in a southeast direction from the figure 2 north edge (just west of center) to Fresno Reservoir, which floods the Milk River valley. From Fresno Reservoir the Milk River continues in a southeast and east direction to Havre and the figure 2 east edge (south half). Big Sandy Creek is the northeast-oriented Milk River tributary in the figure 2 southeast quadrant (paralleling a railroad and highway and joining the Milk River west of Havre). South and east of Big Sandy Creek is the Bears Paw Mountain region. Sage Creek flows in an east and southeast direction from the figure 2 northeast corner region to join Big Sandy Creek near the figure 2 south edge. Note how southeast-oriented Sage Creek joins northeast-oriented Big Sandy Creek as a barbed tributary. Also note how almost Sage Creek and Milk River tributaries in the Sage Creek-Milk River drainage divide area are oriented in southeast directions. The southeast-orientation of present day drainage routes is a relic of massive southeast-oriented ice-marginal melt water floods, which once flowed across the region. One major exception to the southeast orientation of drainage routes is Kennedy Coulee which drains in a southeast and then northwest direction to join the Milk River just north of the figure 2 map area in Canada. The northwest-oriented Kennedy Coulee valley segment was eroded when headward erosion of the deep Milk River valley (which is oriented in an east direction just north of figure 2) beheaded a southeast-oriented flood flow route. Flood waters on the northwest end of the beheaded flood flow route reversed flow direction to erode the northwest-oriented Kennedy Coulee valley segment, which also captured southeast-oriented flood flow from a flood flow route further to the west. Another exception to the southeast orientation of tributaries is what appears to be a north-northwest oriented drainage route from Chain of Lakes to Fresno Reservoir (this will be seen in more detail in figure 4 and will not be the same as shown in figure 2). Note how Dry Lake Coulee (misnamed in figure 2) drains in a southeast direction to the north-northwest oriented drainage route. Again the north-northwest oriented valley segment was eroded by a reversal of flood flow on the north-northwest end of a beheaded flood flow route (beheaded by Milk River valley headward erosion). While not addressed in this essay the southeast-oriented melt water floods in the Sage Creek-Milk River drainage divide area flowed directly toward what is now the high Bears Paw Mountain region in the figure 2 southeast corner region. Apparently the Bears Paw Mountains were not as much of an obstacle to the flood flow at that time as present day elevations would suggest. If so, the Bears Paw Mountains may have been rising as flood waters flowed across the region and deeply eroded the surrounding easily eroded bedrock.

Kennedy Coulee-Sage Creek drainage divide area

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

 

Figure 3 illustrates the Kennedy Coulee-Sage Creek drainage divide area just south of the United States-Canada border in the Hill County northwest corner. Goldstone is a place-name near the figure 3 center. The Milk River flows in a southeast direction across the figure 3 northeast corner (the Milk River is oriented in an east direction just north of the figure 3 center region). Kennedy Coulee is the southeast and north-northwest oriented drainage route in the figure 3 northwest quadrant and drains to the east-oriented Milk River north of the figure 3 map area. Sage Creek flows in a southeast, east, and southeast direction from the figure 3 west edge (south of center) to the figure 3 south center edge. The figure 3 map contour interval is 20 meters and at first glance the region appears to have remarkably low relief (away from the Milk River and Kennedy Coulee valleys). However, a close look reveals an interesting north-northwest to south-southeast oriented through valley extending from the Kennedy Coulee elbow of capture (where Kennedy Coulee turns from draining in a southeast direction to draining in a north-northwest direction) to the Sage Creek valley near the figure 3 south center edge. Goldstone is located on the through valley’s east side. The through valley is drained by what appears to be a discontinuous south-oriented drainage route. The through valley floor elevation is between 900 and 920 meters. East of Goldstone is a northwest-southeast oriented streamlined hill with elevations greater than 940 meters (a spot elevation reads 945 meters, but may not be the highest point). West of the through valley elevations also rise to more than 940 meters and generally appear to be higher than east of the through valley. Note how the through valley roughly parallels the Milk River valley and links the Kennedy Coulee valley segments with the southeast-oriented Sage Creek valley. These valleys provide evidence of multiple southeast-oriented flood flow channels that scoured the figure 3 landscape prior to headward erosion of the deep Milk River valley. Milk River valley headward erosion (north of the figure 3 map area) beheaded southeast-oriented flood moving in what are today both the southeast and the north-northwest oriented Kennedy Coulee valley segments to the south-southeast oriented through valley and then to southeast-oriented Sage Creek valley. Flood waters on the north-northwest end of the eastern Kennedy Coulee segment reversed flow direction to erode the deep north-northwest oriented Kennedy Coulee valley segment. The reversed flood flow captured southeast-oriented flood flow moving on the western Kennedy Coulee valley segment alignment and the deep Kennedy Coulee valley eroded headward along that valley segment. Headward erosion of the deep Kennedy Coulee valley beheaded south-oriented flood flow in the south-southeast oriented through valley to the Sage Creek valley ending flood flow on that route.

Milk River-Sevenmile Coulee drainage divide area

Figure 4: Milk River-Sevenmile Coulee drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 4 illustrates the Milk River-Sevenmile Coulee drainage divide area located east and slightly south of the figure 3 map area (figure 4 in the west has an overlap area with figure 3). The Milk River is labeled and flows in a southeast and south direction from the figure 4 north edge (west half) to the figure 4 south edge (east half). Sevenmile Coulee is a south-southeast oriented valley draining across the figure 4 south center region to join the Milk River near the figure 4 south edge. Note how Sevenmile Coulee is aligned with a north oriented Milk River tributary valley, which enters the Milk River valley as a barbed tributary. While the figure 4 contour interval of 20 meters does not provide enough detail to show a through valley linking the north- and south-oriented valleys, figure 5 below provides a more detailed topographic map to show that such a through valley does in fact exist. Also note how in section 6 just south of an intermittent lake the Sevenmile Coulee valley splits into two valleys which go around an erosional remnant and then join again. The Sevenmile Coulee valley is evidence of a southeast and/or south-oriented anastomosing channel complex which once crossed the figure 4 map area. Compare elevations in the Sevenmile Coulee-Milk River drainage divide area (between 820 and 840 meters) with elevations on the streamlined hill near Goldstone in figure 3 (greater than 940 meters). This difference in elevation illustrates the depth of erosion which occurred in the Milk River valley region as immense southeast and south-oriented melt water floods scoured the region. While today it is difficult to imagine a landscape in the figure 4 map area at least 100 meters higher than it is today, the figure 3 evidence suggests flood waters at one time flowed on such a high level surface. And, there is no evidence in the figure 3 or 4 map areas to suggest how much bedrock material was removed by massive ice-margin melt water floods prior to the levels seen in figure 3.

Detailed map of Milk River-Sevenmile Coulee drainage divide area

Figure 5: Detailed map of Milk River-Sevenmile Coulee drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 5 illustrates a detailed topographic map of the Milk River-Sevenmile Coulee drainage divide area seen in less detail in figure 4 above. The Milk River is labeled and flows from the figure 5 north edge (west half) to the south edge (east half). Sevenmile Coulee drains in a south direction from sections 25 and 30 to the figure 5 south edge in section 6 and is linked by a through valley in the section 25 northeast corner with a north-oriented Milk River tributary valley. As seen in figure 4 south of the figure 5 map area Sevenmile Coulee drains in a south-southeast direction to join the Milk River. The through valley provides evidence that at one time water flowed in the Sevenmile Coulee parallel to what must have been flow in the adjacent Milk River valley. Also note north and east of the Milk River valley in sections 20, 21, and 28 a northwest-southeast oriented through valley extending from near the figure 5 north edge to the south-oriented Spring Coulee valley in section 34. Note how in the section 28 northwest corner and section 29 northeast corner regions a small maze of through valleys links this northwest-southeast oriented through valley with the southeast oriented Milk River valley. This complex of through valleys, which show up best in more detailed topographic maps such as figure 5, provide evidence the deep Milk River valley eroded headward as one of multiple southeast and south-oriented flood flow channels in what was a southeast- and/or south- oriented anastomosing channel complex. The figure 5 map contour interval is ten feet and the Milk River elevation near the figure 5 center is between 2590 and 2600 feet. The northeast valley wall in section 28 rises to more than 2750 feet and elevations along the southwest valley wall are slightly lower, although west of Sevenmile Coulee elevations rise even higher. In other words the Milk River valley is approximately 150 feet deeper than the surrounding surface areas, which as we noted in the figure 4 discussion are significantly lower than the surface the flood waters originally flowed across (in feet those elevations are more than 3100 feet). In other words, evidence seen in figures 3, 4, and 5 suggests more than 350 feet of bedrock material has been removed from the figure 5 map area and more than 500 feet of material has been removed from the Milk River valley area.

Milk River-Chain of Lakes Coulee drainage divide area

Figure 6: Milk River-Chain of Lakes Coulee drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 6 illustrates the Milk River-Chain of Lakes Coulee drainage divide area south and east of the figure 4 map area and there is no overlap between figures 4 and 6. The Milk River valley is flooded by Fresno Reservoir and extends from the figure 6 north center edge area to the figure 6 southeast corner. Note the northwest-southeast oriented through valley on the northeast side of Saddle Butte in the figure 6 northeast quadrant. The through valley is evidence of a southeast oriented flood flow channel which was eroded parallel to the deeper Milk River valley channel. South and west of the Milk River valley is the south-southeast and southeast oriented Chain of Lakes Coulee. Note how at the north end southeast-oriented Archie Coulee enters a north-oriented valley. The north-oriented valley drains to the southeast-oriented Milk River as a barbed tributary. Further to the south southeast- and east-oriented Spring Coulee enters a southeast-oriented valley with discontinuous drainage and just to the south east-oriented Dry Lake Coulee also enters the southeast-oriented Chain of Lakes Coulee valley. Note how the Dry Lake Coulee in figure 2 has the orientation of Spring Coulee. The Chain of Lakes Coulee valley was eroded by another south and southeast-oriented flood flow channel, which eroded headward on a route roughly parallel to the adjacent Milk River valley. These parallel flood flow channels were eroded at a time when south- and southeast-oriented flood waters were eroding anastomosing channels into what was then the figure 6 map area upland surface. Subsequently headward erosion of a much deeper flood flow channel along the present day Milk River valley route beheaded the adjacent diverging and converging flood flow channels. Flood waters on the north ends of the beheaded flood flow channels reversed flow direction to erode what are today valleys of north-oriented barbed Milk River tributaries. In the case of the north end of the southeast-oriented Chain of Lake Coulee valley the reversal of flood flow captured southeast-oriented Archie Coulee, which resulted in Archie Coulee becoming a barbed tributary to what is an unnamed north-oriented barbed Milk River tributary.

Detailed map of Milk River-Chain of Lakes Coulee drainage divide area

Figure 7: Detailed map of Milk River-Chain of Lakes Coulee drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 7 provides a detailed topographic map of the Milk River-Chain of Lakes drainage divide area seen in less detail in figure 6 above. Fresno Reservoir in the figure 7 northeast quadrant floods the southeast oriented Milk River valley. Chain of Lakes Coulee is labeled and is a discontinuous south-southeast drainage route extending to the figure 7 south edge (just east of center). Note how in section 14 (figure 7 northwest quadrant) the valley is draining in a north-northwest direction while south of section 25 where east-oriented Spring Coulee joins the south-southeast oriented Chain of Lakes valley the valley appears to drain in a south-southeast direction. Between the opposing drainage routes the valley is shown as containing a chain of intermittent lakes. The map contour interval is 10 feet and the valley floor in section 25 is between 2620 and 2630 feet with slightly lower elevations further north. Elevations both east and west of the north-northwest to south-southeast oriented through valley rise to at least 2700 feet (more to the west) indicating the valley is at least 70 feet deep. The Milk River channel elevation is shown in the northeast quadrant as being less than 2560 feet suggesting the Milk River valley is at least 140 feet deep. The Chain of Lakes Coulee valley was eroded by south-southeast oriented flood flow along what was one of several southeast- and south-oriented anastomosing flood flow channels. The lakes on the Chain of Lakes Coulee valley floor were probably formed when tributary coulees, such as Spring Coulee, deposited low relief deltas on the Chain of Lakes valley floor. Because headward erosion of the deep Milk River valley had beheaded the south-southeast oriented flood flow in the Chain of Lakes Coulee valley the deltas were not eroded away and blocked the local drainage to form what are today intermittent lakes. Landslides and slumping from the adjacent valley walls may also have played a role in blocking the once continuous south-southeast oriented Chain of Lakes Coulee valley. The north-northwest oriented drainage at the north end of the valley (in figure 7) is flowing in a north-oriented valley eroded by a reversal of flood flow on the north end of the beheaded south-southeast oriented flood flow route.

Detailed map of Big Coulee-O’Brien Coulee drainage divide area

Figure 8: Detailed map of Big Coulee-O’Brien Coulee drainage divide area.United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 8 illustrates a reduction of a detailed topographic map of the Big Coulee-O’Brien Coulee drainage divide area west of the figures 6 and 7 map areas (there is no overlap area). Sage Creek flows in a south-southeast direction from the figure 8 north edge (east half) to the figure 8 southeast corner. Little Sage Creek is a south-southeast oriented Sage Creek tributary located in the Sage Creek valley just west of Sage Creek in the figure 8 northeast quadrant. Big Coulee is an east-southeast oriented stream with a northeast-oriented valley segment in the figure 8 northwest corner, which joins Little Sage Creek in section 10 in the figure 8 northeast quadrant. O’Brien Coulee is an east- and southeast oriented Sage Creek tributary draining from the figure west edge (south half) to the figure 8 south edge (east half) and joining Sage Creek south and east of the figure 8 map area. Note the northwest-southeast oriented through valley in the figure 8 west half linking the Big Coulee valley with the O’Brien Coulee valley. A large northwest-southeast oriented erosional remnant is located near the figure 8 and provides a marker to document how much material has been eroded away. A spot elevation at the top of the erosional remnant near the east edge of section 13 reads 3129 feet. Elevations on the Big Coulee-O’Brien Coulee through valley floor to the west are in the 3030 to 3040 foot range suggesting the through valley has been eroded to a depth of approximately 100 feet. Elevations in the Sage Creek valley to the east are in the 2870 to 2880 foot range suggesting the Sage Creek valley was eroded to a depth of at least 250 feet. Compare the 3129 foot elevation with the 2700 elevation found at the highest points between Chain of Lakes Coulee and the Milk River in figure 7 above. The entire figure 7 map area was apparently lowered by at least 250 feet as the southeast- and south-oriented flood waters scoured that region. And remember there is no reason to believe the 3129 foot elevation seen in figure 8 represents the original surface level. In fact there is good reason to believe substantial erosion occurred prior to reaching the 3129 foot level. In other words, what we are seeing in figure 8 is evidence of deep ice-marginal melt water flood water erosion of the entire north central Montana region, which lowered regional elevations by hundreds of feet, if not more.

Detailed map of Sage Creek-Milk River drainage divide area

Figure 9: Detailed map of Sage Creek-Milk River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 9 is a reduction of a detailed topographic map of the Sage Creek-Milk River drainage divide area east of Gildford, Montana. Gildford is located near the figure 9 west center edge and Kremlin, Montana is located just east of the figure 9 east edge. Sage Creek meanders in a south direction from Gildford to the figure 9 southwest corner and then in an east direction almost to the figure 9 south center edge before turning to flow south of the figure 9 map area. The north-northeast oriented drainage route draining toward the figure 9 northeast corner is Wild Rose Coulee, which north and east of figure 9 drains to south-southeast oriented Chain of Lakes Coulee as a barbed tributary. Note how landforms, especially in the figure 9 east half, have been streamlined in a north-northwest to south-southeast direction. The streamlined hill in section 33 has a spot elevation of 2964 at its top. Elevations in the Sage Creek valley at Gildford are in the 2800 to 2810 foot range. The Chain of Lakes valley floor where Wild Rose Coulee enters (not seen in figure 9) has an elevation of less than 2650 feet and the Milk River valley channel elevation to the east is 2530 feet (also not seen in figure 9). The streamlined landscape seen in figure 9 was eroded by immense south- and southeast oriented flood flow which deeply scoured the entire region. When flood waters first flowed across the region the Milk River valley region to the east was just as high as the figure 9 region. Probably larger volumes of flood flow eroded the Milk River valley deeper than the figure 9 region, although there can be no question the figure 9 map area was deeply eroded also. Headward erosion of the deep Milk River valley into present day Canada and then across southern Alberta (see figure 1) beheaded all southeast- and south-oriented flood flow to the figure 9 map area. I am not sure of the origin of the small depressions east of Gildford. Some of the depressions appear as though they could be the result of flood scour and/or slumping of valley walls (or delta formation on floors of flood carved valleys). However, the depressions in the north half of section 1 and in the section 27 southwest and northwest corners appear to have a different origin, although similar depressions do not appear elsewhere in the region. While the presence of the depressions does not negate the flood origin hypothesis for figure 9 landforms, there may be an additional local factor I have not yet recognized.

Sage Creek-Big Sandy Creek drainage divide area

Figure 10: Sage Creek-Big Sandy Creek drainage divide area. 

United States Geological Survey map digitally presented using National Geographic Society TOPO software.

  • Figure 10 illustrates the Sage Creek-Big Sandy Creek drainage divide area south and east of the figure 9 map area (there is no overlap with figure 9). Big Sandy Creek flows in a north-northeast direction from the figure 10 south edge (just west of center) to the figure 10 north edge (west of northeast corner). North and east of the figure 10 map area Big Sandy Creek flows to the Milk River. Sage Creek flows in southeast direction from the figure 10 northwest corner region to join Big Sandy Creek near the figure 10 south center edge as a barbed tributary. As we have seen in previous figures the Sage Creek-Milk River drainage divide area was eroded by immense southeast and south-oriented melt water floods, which removed hundreds of feet (and/or meters) of bedrock material from at least some of the drainage divide regions (and probably much more which can not be documented). Contour lines are not shown in the figure 10 southeast corner region although spot elevations suggest elevations are significantly higher than the Big Sandy Creek valley floor. North-northeast oriented Big Sandy Creek crosses the 800 meter contour line near the figure 10 south center edge and all valley elevations north and east of that point are lower. A spot elevation near the figure 10 east edge just north of the southeast corner reads 1123 meters. Several spot elevations in the 900-1000 meters range are found in the region to the east and north of the 1123 meter spot elevation. These spot elevations are documenting higher elevations on the edge of the Bears Paw Mountain uplift area. Note how Big Sandy Creek tributaries from the southeast are oriented in northwest directions. The northwest-oriented Big Sandy Creek valley orientations originated as southeast-oriented flood flow channels, which once flowed across what is now the Bears Paw Mountain uplift area. Southeast-oriented flood flow across what is now the Bears Paw Mountain uplift region was reversed by a combination of Bears Paw Mountain uplift, which occurred as flood waters were flowing across the region, and also by headward erosion of the deep north-northeast oriented Big Sandy Creek valley. Flood waters on northwest ends of the southeast-oriented flood flow channels reversed flow direction to erode the northwest-oriented Big Sandy Creek tributary valleys. The massive southeast-oriented flood flow deeply eroded the region east and north of the Bears Paw Mountain uplift to achieve the landscape seen today.

Additional information and sources of maps studied

This essay has provided only a sample of the detailed topographic map evidence supporting the flood erosion interpretation. Many additional illustrations could be provided. Readers are encouraged to look at mosaics of detailed topographic maps to see the abundance of available data. Maps used in this study were created and published by the United States Geologic Survey and can be obtained directly from the United States Geological Survey and/or from dealers offering United States Geological Survey maps. Hard copy maps can also be observed at United States Geological Survey map depositories, which are located throughout the United States and elsewhere. Illustrations used here were created using National Geographic Society TOPO software and digital map data. TOPO software and map data can be obtained from the National Geographic Society and/or dealers offering National Geographic Society digital map data.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: