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

Abstract:

Topographic map interpretation methods are used to interpret landform origins in the Milk River-Battle Creek drainage divide area located in northeast Hill County, Montana. The study region is bounded on the west and south by the southeast and east-oriented Milk River, on the north by the Canadian border, and on the east by south-southeast oriented Battle Creek and was deeply eroded by immense southeast-oriented ice-marginal melt water floods flowing along the southwest margin of a rapidly melting North American ice sheet. Evidence within the study region documents headward erosion of valleys 100 or more meters deep into upland erosion surfaces, although evidence from adjacent drainage divide regions suggests the valleys may have been much deeper when initially eroded. Headward erosion of the east-oriented and deep Milk River captured the southeast-oriented flood flow and deep southeast-oriented flood flow channels then scoured regions to the northwest as they eroded headward from the newly eroded Milk River valley north wall. Immense quantities of southeast-oriented flood water moving into the newly eroded and deep Milk River valleys completely removed the valley’s north wall and deeply scoured the region to the northwest. Streamlined erosional residuals, a predominance of southeast-oriented drainage routes, barbed tributaries, and northwest-southeast oriented through valleys are examples of the topographic map evidence supporting this flood erosion interpretation.

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-Battle Creek drainage divide area landform origins in northeast 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 links 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 Milk River-Battle Creek drainage divide area landform evidence in northeast 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.

Milk River-Battle Creek drainage divide area location map

Figure 1: Milk River-Battle Creek 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 is a location map for the Milk River-Battle Creek drainage divide area in northeast Hill County, Montana and illustrates a region in north central Montana with southwest Saskatchewan and the Alberta southeast corner located to the north. The Milk River flows from the figure 1 west edge (just north of the Canada-United States border) in an east direction almost to Wild Horse, Alberta before turning to flow in a southeast direction to Fresno Reservoir and Havre, Montana. From Havre the Milk River flows in an east and east-southeast direction to Malta where the Milk River makes a north-northeast oriented jog before flowing in a southeast direction to the figure 1 east edge (near Hinsdale). The Missouri River flows in a northeast direction from the figure 1 south edge (west half) to Fort Benton and Loma before flowing in a southeast and east-northeast direction around the Bears Paw Mountains south margin and then to Fort Peck Reservoir (unlabeled in figure 1, but seen near the figure 1 southeast corner). The Milk River joins the Missouri River downstream from Fort Peck Reservoir (not seen in figure 1). Battle Creek originates in the Cypress Hills region of southwest Saskatchewan and flows in a south-southeast direction to join the Milk River near Chinook, Montana. Lodge Creek is located west of Battle Creek and originates in the Cypress Hills region of southeast Alberta and flows in a southeast direction to join the Milk River also near Chinook, Montana. Between Lodge Creek and the Milk River in southeast Alberta is southeast-oriented Sage Creek, which flows to Wild Horse Lake, which located in Montana just south of the Alberta-Saskatchewan border. Note how Wild Horse Lake is shown as an intermittent lake with no outlet. The Milk River-Battle Creek drainage divide area in northeast Hill County, Montana investigated in this essay (which also includes a small region in northwest Blaine County, Montana) is located north and east of the Milk River, west of Battle Creek, and south of the Canada-United States border. The Battle Creek-Savoy Creek drainage divide area landform origins, Blaine County, Montana essay describes landform origins in the region directly to the east. Milk River drainage divide area essays can be found listed under Milk River in the sidebar category list.

Before looking at the Milk River-Battle Creek drainage divide area in detail I will briefly comment what was happening in a much larger picture view based on evidence from hundreds of other Missouri River drainage basin landform origins research project essays. The Milk River-Battle Creek drainage divide area observed in this essay was eroded by massive southeast-oriented melt water floods flowing along the southwest margin of a rapidly melting North American ice sheet. Events described in this essay occurred very late in the ice sheet’s melt down history and were preceded by many previous erosional events for which evidence no longer remains. The ice sheet had formed on a topographic surface at least as high, if not higher, than the highest level Rocky Mountain erosion surfaces today, although those Rocky Mountain erosion surfaces have probably been uplifted since that time. The ice sheet formed a deep “hole” by both deep glacial erosion of underlying bedrock and by crustal warping of adjacent regions. Rocky Mountain uplift, including uplift of Rocky Mountain outlier ranges such as the Bears Paw Mountains seen in figure 1, probably was caused by crustal warping related to the ice sheet’s great weight and perhaps also by crustal unloading as immense ice-marginal melt water floods eroded the region. In other words, the Milk River-Battle Creek drainage divide area probably has experienced deep melt water flood erosion several times greater than any erosion documented by present day topographic map evidence. Initially this melt water flood erosion occurred as giant southeast-oriented melt water floods flowed along the ice sheet’s southwest margin. Subsequently, as deep ice-walled and ice-floored canyons were carved by supra glacial melt water rivers into the ice sheet surface, and the floors of these ice-walled canyons became lower than elevations of bedrock surfaces adjacent to the melting ice sheet, the ice-marginal melt water floods were diverted in northeast and east directions onto the ice sheet surface toward these deep ice-walled canyons. The resulting northeast and east-oriented flood flow movements deeply eroded ice-marginal regions such as the figure 1 map area and as the floors of the ice-walled canyons became lower the northeast and east-oriented flood flow routes migrated downstream along the ice-walled canyons (and to the southeast along the ice sheet southwest margin).

The final erosion event, which is best recorded by present day topographic map evidence, began as a deep east and northeast oriented valley eroded headward from what had become an ice-walled and bedrock-floored canyon in the North Dakota northwest corner. This huge ice-walled and bedrock-floored canyon had for all practical purposes detached the ice sheet’s southwest margin and today the northeast and east facing Missouri Escarpment in Saskatchewan, North Dakota, and South Dakota is all that remains of the canyon’s southwest and west wall. The deep northeast and east oriented valley eroded headward across the ice sheet’s detached southwest margin into northeast Montana and then across Montana along the route of the present day Missouri River valley route and soon thereafter a tributary valley eroded headward across Montana along the present day Milk River valley route. The Milk River valley eroded headward across southeast-oriented melt water flood flow and captured the flood flow and diverted flood waters to the newly eroded east and northeast oriented valley, which then directed the flood flow to the giant ice-walled and bedrock-floored canyons which had been carved into the decaying ice sheet surface. South and east of the Cypress Hills upland region in southwest Saskatchewan and southeast Alberta, between Battle Creek and Whitewater Creek, an upland region drained by Woody Island Coulee is where deep erosion by Milk River valley tributaries did not occur and evidence of earlier northeast- and east-oriented flood flow can be seen, however east and west of that upland the landscape was deeply eroded by southeast-oriented melt water flood flow moving to the newly eroded and deep Milk River valley. The Woody Island Coulee upland surface stands more than 200 meters higher than the floor of the Milk River valley to the south, suggesting the Milk River valley when eroded was at least 200 meters deep. Evidence presented in essays describing the Bears Paw Mountain region (e.g. Beaver Creek-Birch Creek drainage divide area, Big Sandy Creek-Beaver Creek drainage divide, and Big Sandy-Birch Creek drainage divide essays) suggests flood waters once crossed the Bears Paw Mountains, although Bears Paw Mountain uplift may have been occurring at that time, which means present day Bears Paw Mountain elevations may not be reliable markers to determine flood erosion depths.

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

Figure 2: Detailed location map for Milk River-Battle Creek drainage divide area.United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 2 is a detailed location map for the Milk River-Battle Creek drainage divide area in northeast Hill County, Montana. The Canadian border is located along the figure 2 north edge. Hill County is labeled and the county east of Hill County is Blaine County and the Hill-Blaine County line is shown. The Milk River flows in a southeast direction from the figure 2 northwest corner to Fresno Reservoir and then to Havre. From Havre the Milk River flows in an east direction to Chinook and the figure 2 east edge. Battle Creek flows in a south-southeast direction across the Hill County northeast corner (just barely) and then to join the Milk River near Chinook in Blaine County. West of Battle Creek is southeast oriented Lodge Creek, which flows through Creedman Coulee National Wildlife Refuge (in the Hill County northeast corner region) and then to join the Milk River also near Chinook. Between Lodge Creek and the Milk River in eastern Hill County is southeast-oriented Redrock Coulee, which has an extensive network of southeast-oriented tributaries. Redrock Coulee is shown as draining toward the Milk River near Lohman, in western Blaine County, although a definite link to the Milk River is not shown. Near the Canadian border, between the Milk River and Lodge Creek, is Wild Horse Lake, which is shown as an intermittent lake with no outlet. Spring Coulee is a southeast- and south-oriented Milk River tributary located between the Milk River and Wild Horse Lake. The predominance of southeast-oriented drainage routes is evidence of the southeast-oriented flood flow that eroded the Milk River-Battle Creek drainage divide area as massive ice-marginal melt water floods flowed into the newly eroded and deep Milk River valley. Evidence presented in the Battle Creek-Savoy Creek drainage divide area landform origins essay for the region east of figure 2 documents the Milk River valley eroded headward into a topographic surface at least 200 meters higher than the present day Battle Creek and Milk River valley floor elevations. Topographic map evidence in the Milk River-Battle Creek drainage divide area does not document as a deep a Milk River valley in the Milk River-Battle Creek drainage divide area, although the lack of higher surface remnants probably is because of much deeper flood erosion west of the Battle Creek valley. Regions east of the Battle Creek valley were protected from southeast-oriented flood erosion by the presence of the Cypress Hills upland region in Canada (see figure 1). No such protection from southeast-oriented flood flow erosion existed in the region west of the Battle Creek valley. As a result the topographic map examples shown below illustrate a region which was deeply scoured by immense southeast-oriented floods.

Sage Creek-Spring Coulee drainage divide area

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

Figure 3 illustrates the Sage Creek-Spring Coulee drainage divide area located south of the Canadian border. The Milk River flows in a southeast direction across the figure 3 southwest quadrant. Spring Coulee is labeled and drains in a southeast direction from the figure 3 north edge (west half) to the figure 3 center region and then in a south direction to the figure 3 south edge. Note how northwest-southeast oriented Spring Coulee Ridge is located immediately to the northeast of the southeast-oriented Spring Coulee segment. Grassy Lake is located along the Canadian border just east of Spring Coulee Ridge and Sage Creek flows from Grassy Lake in a southeast direction to Wild Horse Lake, which is located in the figure 3 northeast quadrant. Note how Grassy Lake and other figure 3 lakes outside the Milk River valley are shown as intermittent lakes and how Wild Horse Lake is shown in way that suggests it is perhaps even more intermittent and most of the time is probably just a flat sandy region that can be covered with water during wet periods. The map contour interval is 20 meters and the highest figure 3 elevations are along the crest of the northwest-southeast oriented Spring Coulee Ridge, which extends along the Wild Horse Lake southwest margin. Elevations along Spring Coulee Ridge rise to slightly above 900 meters. Lowest figure 3 elevations are in the Milk River valley, which near the figure 3 south edge has a floor elevation of slightly less than 800 meters. The Milk River valley appears to be generally 40-60 meters deep, which means relief elsewhere on the map is in the 40-60 meter range. Note how landforms are streamlined in a northwest-southeast direction, which is the result of the southeast-oriented flood flow that scoured the entire figure 3 map area. The south-oriented Spring Coulee valley segment eroded headward from what was at that time the actively eroding Milk River valley head to capture southeast-oriented flood flow moving parallel to the actively eroding Milk River valley. The southeast-oriented Spring Coulee valley segment and southeast-oriented Spring Coulee valley segments were eroded by southeast-oriented flood flow routes captured by headward erosion of the south-oriented Spring Coulee valley segment. North and east of the northwest-southeast oriented Spring Coulee Ridge southeast-oriented flood waters moving on the Sage Creek-Wild Horse Lake alignment used a separate broad southeast-oriented flood flow channel which eroded headward what was then the actively eroding southeast-oriented Lodge Creek valley (see figures 4 and 5). Spring Coulee Ridge is an erosional remnant left as flood waters flowed to the southeast-oriented Milk River valley to the southwest and to southeast-oriented Lodge Creek to the northeast.

Wild Horse Lake-Dog Coulee drainage divide area

Figure 4: Wild Horse Lake-Dog Coulee drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates the Wild Horse Lake-Dog Coulee drainage divide area east of the figure 3 map area and includes a thin overlap area with figure 3. The international border is located along the figure 4 north edge. The southeast end of Wild Horse Lake is located near the figure 4 northwest quadrant west edge. Dog Coulee originates along the northwest-southeast oriented ridge in the figure 4 southwest quadrant (the Havre Air Force Station is located on the ridge). Note how Dog Coulee first drains in a north direction and then turns to drain in an east-southeast direction across the figure 4 south center region and then to the figure 4 south edge (east half). Also note how an unnamed northeast and northwest-oriented stream also drains the ridge on which Havre Air Force Station is located and then turns to flow in the opposite direction of Dog Coulee toward Wild Horse Lake. The northwest-oriented segment of this unnamed stream and the east-southeast oriented Dog Coulee segment are located on approximately the same northwest-southeast oriented alignment and are relics of what was once a southeast-oriented flood flow channel, which drained to what was then an actively eroding and deep southeast-oriented Lodge Creek valley, which had eroded headward from the newly eroded and deep Milk River valley. The massive southeast-oriented flood flow scoured most of the figure 4 map area the flood flow channel floor was graded to the elevation of the newly eroded Lodge Creek valley floor. The northwest-southeast oriented ridge on which Havre Air Force Station is located is an erosional remnant preserved along the dividing line between the southeast-oriented flood flow to the actively eroding Lodge Creek valley (to the northeast) and flood flow to the actively eroding Milk River valley (to the southwest). Lodge Creek (unnamed in figure 4) can be seen flowing in a south-southeast direction across the figure 4 northeast corner. South and west of Lodge Creek is southeast-oriented Creedman Coulee, which is a Lodge Creek tributary.The southeast-orientation of figure 4 drainage routes reflects flood flow directions at the time the figure 4 map region was eroded. Flood erosion in the Wild Horse Lake basin must have scoured the region slightly deeper and/or deposition of flood transported sediments to the southeast of the lake basin created a low barrier, which blocked the southeast-oriented flood flow route and created a shallow lake basin.

Lodge Creek-Battle Creek drainage divide area

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

Figure 5 illustrates the Lodge Creek-Battle Creek drainage divide area east of the figure 4 map area and includes overlap areas with figure 4. The international border is located along the figure 5 north edge. Lodge Creek is labeled and flows in a south-southeast direction from the figure 5 north edge (near northwest corner) to the figure 5 south edge (just east of center). Creedman Coulee is the southeast-oriented stream labeled “Coulee”. Battle Creek flows in a south direction near the east edge of the figure 5 northeast quadrant and then turns to flow in south-southeast direction to the figure 5 east edge. Woodpile Coulee is a southeast-oriented Battle Creek tributary in the figure 5 northeast quadrant and Antelope Coulee is a southeast-oriented Woodpile Coulee tributary near the figure 5 north edge. Hay Coulee drains in a south-southeast direction across the figure 5 east half and is located between Lodge Creek and Battle Creek. South of the figure 5 map area Hay Coulee drains to Lodge Creek. The map contour interval is 20 meters and elevations in the figure 5 southwest corner region exceed 860 meters. Elevations in the Battle Creek valley where it crosses the figure 5 east edge are less than 800 meters. Elevations along the Battle Creek-Woody Island Coulee drainage divide east of the figure 5 map area rise to more than 1060 meters, which probably represents the maximum level of the topographic surface into which the Milk River valley and its southeast-oriented tributary valleys (such as the Battle Creek and Lodge Creek valleys and their tributary valleys) were eroded. If so, the entire figure 5 map area was lowered by more than 200 meters as massive southeast-oriented ice-marginal melt water flood flow moved across the region and into the newly eroded and deep Milk River valley to the south. The southeast orientation of many figure 5 drainage routes provides evidence of the flood flow direction.

Cottonwood Coulee-Redwood Coulee drainage divide area

Figure 6: Cottonwood Coulee-Redwood Coulee drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates the Cottonwood Creek-Redwood Coulee drainage divide area located south and west of the figure 4 map area and there is no overlap area with previous figures. The Milk River valley is located in the figure 6 southwest corner and is flooded by Fresno Reservoir. Cottonwood Coulee is labeled and drains in a south direction from the figure 6 north edge (west half) to the Milk River valley near the figure 6 southwest corner. Note how in the figure 6 west center region East Cottonwood Coulee drains in a west-northwest direction to south-oriented Cottonwood Coulee. Redrock Coulee is labeled and originates north of west-northwest oriented East Cottonwood Coulee and drains in an east-southeast direction to the figure 6 east edge (south of center). Note how the Redrock Coulee valley is linked by a through valley with the south-oriented Cottonwood Coulee valley. The map contour interval is 20 meters and the through valley floor elevation is between 840 and 860 meters. Elevations north and south of the through valley rise to more than 900 meters, meaning the through valley is at least 40-60 meters deep. The through valley provides evidence of what was once a large east-southeast oriented flood flow channel, which had eroded headward from the Milk River valley east of the figure 6 map area. Headward erosion of the deep Milk River valley, and then of the south-oriented Cottonwood Coulee valley from the newly eroded Milk River valley, captured the southeast and south-oriented flood flow moving to the Redrock Coulee flood flow channel and in the process beheaded the Redrock Coulee flood flow channel and created the through valley seen today. Note other southeast and south-oriented streams in the figure 6 map area, which provide additional evidence of the southeast-oriented flood flow which once crossed the figure 6 map area. Northeast-oriented Lohman Coulee and east-northeast oriented Quigley Coulee in the figure 6 southeast quadrant were eroded headward from the actively eroding Redrock Coulee valley head in sequence across southeast-oriented flood flow which was subsequently beheaded by headward erosion of the actively eroding east-southeast oriented Redrock Coulee valley.

Detailed map of Cottonwood Coulee-Redrock Coulee drainage divide area

Figure 7: Detailed map of Cottonwood Coulee-Redrock 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 Cottonwood Coulee-Redrock Coulee drainage divide area seen in less detail in figure 6 to better illustrate the through valley seen in figure 6. Redrock Coulee drains in a south-southeast direction from section 18 (near figure 7 north center edge) to section 19 and then turns to drain in an east-southeast direction to section 28 near the figure 7 east edge. Cottonwood Coulee drains in a south-southeast direction in section 13 (near figure 7 north edge) to the eastern margin of section 24 where it turns to make a westward jog before turning again to flow in a south direction along section 25 western margin and then to flow in a west-southwest direction toward the figure 7 southwest corner. East Cottonwood Coulee drains in a northwest direction to join Cottonwood Coulee where it turns from draining in a south direction to draining in a west-southwest direction. South of the figure 7 map area Cottonwood Coulee turns again to drain in a south-southeast direction to the Milk River. Note the through valley linking the Cottonwood Coulee and Redrock Coulee valleys in the south half of section 19 and along the section 30 north margin. The map contour interval is ten feet and the through valley floor elevation is between 2800 and 2810 feet. Elevations in the section 30 southeast quadrant rise to more than 2980 feet and elevations greater than 2980 feet can be in sections 16 and 17 in the figure 7 northeast quadrant. In other words the through valley is more than 170 feet deep. Also note how the east-southeast oriented Redrock Coulee valley extends in a northwest direction to the figure 7 northwest corner region (the highway follows the valley toward the northwest corner). The south-southeast oriented Cottonwood Coulee and Redrock Coulee valleys in the figure 7 north half both originated as south-oriented tributaries to an east-southeast oriented Redrock Coulee flood flow channel. Headward erosion of the south-oriented Cottonwood Coulee valley segment in the figure 7 southwest quadrant probably originated from a southeast-oriented flood flow channel on the present day northwest-oriented East Cottonwood Coulee alignment. Headward erosion of the south-oriented Cottonwood Coulee valley (not seen in figure 7) from the Milk River valley then captured the south-oriented Cottonwood Coulee valley segment seen in the figure 7 southwest quadrant and in doing so beheaded and reversed flood flow on the East Cottonwood Coulee alignment so as to to erode the northwest-oriented East Cottonwood Coulee valley.

Redrock Coulee-Milk River drainage divide area

Figure 8: Redrock Coulee-Milk River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates the Redrock Coulee-Milk River drainage divide area located south and east of the figure 6 map area and includes overlap areas with figure 6. The south-southeast oriented Milk River valley is located near the figure 8 west edge and is flooded by Fresno Reservoir. Fresno Dam is located near the figure 8 south edge. Cottonwood Coulee drains in a south-southeast and southwest direction in the figure 8 northwest corner. Other named Milk River tributaries from the east (from north to south) are Miller Coulee, Browns Coulee, Kiehns Coulee, Messerschmidt Coulee, Nelson Coulee, Davenport Coulee, Cherry Coulee, Supenau Coulee and Fiedling Coulee. Note how Browns Coulee and Kiehns Coulee after draining in south and south-southwest directions turn to drain in northwest directions to enter the south-southeast oriented Milk River valley. The northwest-oriented segments of these south-oriented coulee valleys were eroded by reversals of flood flow on the northwest ends of beheaded flood flow routes. Also note a northwest-southeast oriented through valley just north of Fresno Dam, which provides evidence of a southeast-oriented flood flow channel parallel to the deeper southeast-oriented Milk River valley. The south-southwest and south oriented Milk River tributary valleys were eroded in sequence as the actively eroding and deep Milk River valley eroded headward into and across the figure 8 map area. For example, headward erosion of the Supenau Coulee beheaded flood flow to what was then the newly eroded Fielding Coulee valley. Headward erosion of the Nelson Coulee valley beheaded flood flow to the newly eroded Davenport and Cherry Coulee valleys and also to the newly eroded Supenau Coulee valley. Kiehns Coulee valley headward erosion beheaded flood flow to the newly eroded Messerschmidt Coulee and Nelson Coulee valleys and headward erosion of the Browns Coulee valley beheaded flood flow to the newly eroded Kiehns Coulee valley. Finally headward erosion of the Cottonwood Coulee valley beheaded flood flow routes to the newly eroded Miller and Browns Coulee valleys. Much of the flood flow in these coulee valleys was eroding the east-northeast wall of what was at that time the actively eroding and deep south-southeast oriented Milk River valley head area. The Milk River valley floor just below Fresno Dam has an elevation of between 760 and 780 meters. Flagstaff Hill near the figure 8 center has an elevation of 898 meters and provides evidence the Milk River valley as it eroded headward into and across the figure 8 map area was at least 120 meters deep, although the topographic surface into which the deep Milk River valley was eroded was much higher than the present elevation of Flagstaff Hill.

Coal Coulee-Milk River drainage divide area

Figure 9: Coal Coulee-Milk River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Coal Coulee-Milk River drainage divide area located east and slightly south of the figure 8 map area and includes overlap areas with figure 8. Havre is the city located in the figure 9 southwest quadrant. The Milk River flows in an east-southeast direction from the figure 9 west edge to Havre and then makes a northeast jog before flowing in an east direction across the figure 9 south center region and then makes a jog to the northeast just before reaching the figure 9 east edge. East of the figure 9 map area the Milk River again flows in an east direction. The northeast-oriented valley segment northeast of Havre has southeast and east-southeast oriented tributaries. Note how an unnamed east-oriented Milk River tributary is linked by a through valley with south-southwest oriented Wales Coulee (a Milk River tributary located near the figure 9 west edge). Coal Coulee is labeled and drains the figure 9 northwest quadrant to east-southeast oriented Redrock Coulee, which is seen in the figure 9 northeast quadrant. The Milk River valley floor elevation in the figure 9 south center region is between 740 and 760 meters (the map contour interval is 20 meters). The Redrock Coulee valley in the figure 9 northeast quadrant has a floor elevation of between 760 and 780 meters, suggesting it is almost as deep as the Milk River valley to the south. Elevations along the Coal Coulee-Milk River drainage divide near the figure 9 west center edge rise to more than 880 meters, which suggests the Milk River valley was at least 120 meters deep when it eroded headward across the figure 9 map area and the Redrock Coulee valley was almost as deep. As previously noted the topographic surface into which the deep Milk River valley and its deep tributary valleys, such as the Redrock Coulee valley, were eroded was probably at least 120 meters higher than the present day Coal Coulee Milk River drainage divide. The east- and east-southeast oriented drainage routes predominant in the figure 9 map area suggest flood waters were flowing primarily in east and east-southeast directions across the figure 9 map area as they deeply eroded the entire figure 9 map region. As seen in earlier figures these east and east-southeast oriented flood waters were being fed by massive southeast-oriented flood flow from the north.

Thibadean Coulee-Redrock drainage divide area

Figure 10: Thibadean Coulee-Redrock Coulee drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 illustrates the Thibadean Coulee-Redrock Coulee drainage divide area north and east of figure 9 and includes overlap areas with figure 9. Battle Creek flows in a south-southeast direction from the figure 10 north edge (east half) to the figure 10 southeast corner. Dry Fork is the south-oriented Battle Creek tributary located east of Battle Creek. Lodge Creek flows in a southeast direction from the figure 10 north edge (west of center) to the figure 10 south edge (just west of southeast corner). Note how in the figure 10 southeast quadrant Lodge Creek and Battle Creek share the same valley, but are flowing in separate channels. The map contour interval is 20 meters and elevations along the Battle Creek valley floor near the figure 10 southeast corner are in the 740-760 meter range. East of the figure 10 northeast corner elevations rise to more than 1060 meters on buttes forming the rim of a large abandoned east and/or northeast-oriented headcut standing above a high level topographic surface remnant (see Battle Creek-Savoy Creek drainage divide area landform origins essay). Redrock Coulee is labeled and is located in the figure 10 southwest quadrant and drains in an east-southeast direction to the east-oriented Milk River valley, which is located just south of the figure 10 map area. Thibadean Coulee is an east-oriented Lodge Creek tributary located in the figure 10 northwest quadrant. Elevations in much of the figure 10 northwest quadrant are in the 820 to 840 meter range, which gives the impression the valleys are 60 meters or less deep. However, the entire figure 10 map region was deeply eroded by massive southeast-oriented flood flow flowing into what was initially probably a 200-300 meter deep east-oriented Milk River valley. The north wall of that deep east-oriented Milk River valley was completely removed by the immense southeast-oriented melt water floods and valleys seen in figure 10 were eroded into the new erosion surface formed as the flood waters flowed across the region.

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.