Rock Creek-Porcupine Creek drainage divide area landform origins, Valley County, Montana, USA

· Milk River, Montana
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  • Eric Clausen Website: http://geomorphology… At present I am a professor emeritus having taught geology at Minot State University (North Dakota, USA) from 1968 until 1997. I was trained in geology at Columbia University and the University of Wyoming where my studies emphasized regional geomorphology. For many years I have pursued a research interest that developed when as result of geologic field work and interpretation of large mosaics of detailed North American topographic maps I discovered significant evidence previous investigators had ignored. Over a period of many years, after studying such anomalous evidence, I was forced to develop a fundamentally different interpretation of North American geomorphic history than that which is generally accepted. Geomorphology is the study of landforms and my interest as a geomorphology researcher is in determining the origin of large drainage systems, such as the Missouri River drainage basin in North America. The Missouri River drainage basin consists of thousands of smaller drainage basins, each of which has a history my essays (website posts) are trying to unravel. What I try to do is reconstruct the landscape the way it looked prior to the present day drainage system. I then try to determine how the present day drainage system evolved. While conducting my Missouri River drainage basin landform origins study I also developed an interest in scientific paradigms, especially in how scientific paradigms develop and how they are replaced. The Missouri River drainage basin landform origins project at geomorphologyresearch.com has been completed and I am currently creating a catalog of Philadelphia, PA area erosional landforms, which can be found at phillylandforms.info For off site questions and discussions about either project I can be contacted at eric2clausen@gmail.com

Abstract:

Topographic map interpretation methods are used to interpret landform origins in the Rock Creek-Porcupine Creek drainage divide area located in Valley County, Montana. Rock Creek originates in the Wood Mountain area in southern Saskatchewan, just north of the international border, and flows in a south-southwest and south direction to join the southeast-oriented Milk River near Hinsdale, Montana. Porcupine Creek is located east of Rock Creek and originates near Opheim, Montana, just south of the international border, and flows in a south direction to join the Milk River just before the Milk River joins the east-oriented Missouri River. The Rock Creek-Porcupine Creek drainage divide area was eroded by immense south-oriented glacial melt water floods as the deep Missouri River and Milk River valleys eroded headward into the region. Initially multiple south-southeast oriented flood flow channels, such as might be found in a large south-southeast oriented anastomosing channel complex, were captured by headward erosion of the south-oriented Porcupine Creek valley. These south-southeast oriented flood flow channels were subsequently beheaded by headward erosion of south-southwest, southwest, and west oriented Rock Creek tributary valleys, which may have occurred as a south-southwest oriented anastomosing channel complex was being formed. Evidence for the initial south-southeast oriented anastomosing channel complex is found in the form of through valleys crossing present day drainage divides and barbed tributaries to Rock Creek tributaries. Present day drainage patterns, when combined with the through valley evidence, document the existence of closely spaced south-oriented diverging and converging flood flow channels, such as might be found in an anastomosing channel complex.

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 Rock Creek-Porcupine Creek drainage divide area landform origins in Valley 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 link to those essays 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 Rock Creek-Porcupine Creek drainage divide area landform evidence in Valley County, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm (see menu at top of page for paradigm related essay). This essay is included in the Missouri River drainage basin landform origins research project essay collection.

Rock Creek-Porcupine Creek drainage divide area location map

Figure 1: Rock Creek-Porcupine 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 Rock Creek-Porcupine Creek drainage divide area in Valley County, Montana location map and illustrates a region in northeast Montana with southern Saskatchewan to the north. Fort Peck Lake is a large reservoir flooding the Missouri River valley and the Missouri River flows in an east direction from Fort Peck Dam to the North Dakota border along the figure 1 east edge (south half). The Milk River flows from Zurich (near figure 1 west center edge) to Harlem, Dodson, Wagner, and Malta and then makes a jog in a northeast direction before flowing in a southeast direction to Saco, Hinsdale, Vandalia, Tampico, Glasgow, and Nashua before joining the Missouri River downstream from Fort Peck Dam. Porcupine Creek is a south-oriented stream originating near Opheim (just south of the Canada-United States border, near figure 1 center) and joining the Milk River near Nashua, just before the Milk River joins the Missouri River. Rock Creek originates in the Wood Mountain area north of the international border (figure 1 center area) and flows in a south-southwest and south direction to join the Milk River near Hinsdale. Willow Creek is a west and south-southwest oriented Rock Creek tributary. Between Rock Creek and Porcupine Creek is south-southwest oriented Lime Creek, which joins the Milk River near Tampico. [On the more detailed maps Lime Creek is a relatively minor stream and Buggy Creek is the more significant stream in the Lime Creek location.] West of Rock Creek is the east-southeast and south oriented Frenchman River which flows from southern Saskatchewan to join the Milk River near Saco. East of the Porcupine Creek headwaters is the southeast oriented West Fork Poplar River, which flows to the southeast- and southwest-oriented Poplar River, which in turn flows to the Missouri River near Poplar. The Rock Creek-Porcupine Creek drainage divide area in Valley County, Montana is located north of the Milk River, south of the international border, west of Porcupine Creek, and east of Rock Creek. The Wood River-Frenchman River drainage divide area landform origins essay and the Wood River-Poplar River drainage divide area landform origins essay describe regions north of the Rock Creek-Portcupine Creek drainage divide area and the Poplar River-Missouri River drainage divide area landform origins, Daniels, Valley, and Roosevelt Counties essay describes the region directly to the east. Poplar River essays can be located under the MT Missouri category on the sidebar category list and the Frenchman River essay can be located under the Milk River category.
  • Based on topographic map evidence presented in this essay and on topographic map evidence presented in hundreds of similar essays the figure 1 map area was eroded by massive south, south-southeast, and southeast oriented melt water floods moving along the southwest margin of a rapidly melting North American ice sheet. At the time the figure 1 map area was eroded the ice sheet southwest margin was located in the figure 1 northeast corner area and had been detached when a giant southeast and south-oriented ice-walled and bedrock-floored canyon was carved into the decaying ice sheet surface. Today the northeast and east-facing Missouri Escarpment, which extends from east central Alberta to south central South Dakota, is what remains of that ice-walled and bedrock-floored canyon’s southwest and west wall. The ice-walled and bedrock-floored canyon floor was significantly lower in elevation than areas south and west of the ice sheet’s detached southwest margin, which meant massive southeast, south-southeast, and south oriented ice marginal melt water floods were flowing at an elevation much higher than elevations east and north of what was a northwest-southeast oriented ice barrier. A major breach in the ice sheet’s detached southwest margin opened up in the Medicine Lake, Montana area (near figure 1 east center edge) and a deep northeast-oriented valley eroded headward from that breach to capture the massive ice-marginal floods. Today that valley has been abandoned in the region northeast of Poplar, Montana, but west of Poplar the Missouri River valley and its tributary valleys, including the Milk River valley, eroded headward in sequence (from south to north) from the that ice sheet margin breach. Note how south of Fort Peck Dam there is the flooded north-oriented valley of Big Dry Creek, which is located on approximately the same alignment as south-oriented Porcupine Creek. The north-oriented Big Dry Creek valley was eroded by a reversal of flood flow on the north end of a beheaded south oriented flood flow route, which had been beheaded by headward erosion of the deep Missouri River valley. Milk River valley headward erosion next captured the south-oriented flood flow route and what is today the deep Porcupine Creek valley then eroded headward from the newly eroded Milk River valley. The south-oriented Lime Creek, Rock Creek, and Frenchman River valleys also eroded headward from the actively eroding and deep Milk River valley. Topographic maps illustrated in this essay provide a sample of evidence supporting the flood origin for landform origins in the Rock Creek-Porcupine Creek drainage divide area.

Detailed location map for Rock Creek-Porcupine Creek drainage divide area

Figure 2: Detailed location map for Rock Creek-Porcupine Creek 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 Rock Creek-Porcupine Creek drainage divide area in Valley County, Montana. The international border is located along the figure 2 north edge and all figure 2 areas are in Montana. County names and boundaries are shown. The Milk River flows in a southeast direction from near the figure 2 west center edge to Saco, Hinsdale, Tampico, Glasgow, and Nashua before flowing to the figure 2 south edge. South of the figure 2 map area the Milk River joins the east-oriented Missouri River, which can be seen along the Fort Peck Indian Reservation south edge near the figure 2 southeast corner. Porcupine Creek and the West Fork Porcupine Creek form the western boundary of the Fort Peck Indian Reservation. The Middle Fork Porcupine Creek originates west of Opheim north of the Fort Peck Reservation northwest corner. Rock Creek flows in a south-southwest and south direction from the figure 2 north edge (west of center) to join the Milk River near Hinsdale. Note how in northern Valley County Rock Creek tributaries (e. g. South Fork) are oriented in west directions and appear linked to east-oriented West Poplar River tributaries (e. g. Roanwood Creek and Spring Creek), which appear to have beheaded south-southeast headwaters of Porcupine Creek tributaries (e.g. Snow Coulee). South of west oriented South Fork are west and southwest oriented headwaters of Willow Creek and its southwest-oriented tributaries. South of the southwest and west-southwest oriented Willow Creek tributaries are a maze of south-oriented Milk River tributaries including Buggy Creek and its tributary Canyon Creek. Note how north of Glasgow the southeast-oriented Dry Fork Creek, which flows to Porcupine Creek, and south-southeast oriented Porcupine Creek appear to have beheaded a number of the south-oriented drainage routes to the Milk River, including Cherry Creek. Further north note how southwest-oriented Willow Creek tributaries appear to have beheaded south-southeast oriented Porcupine Creek tributaries (Dry Fork Creek and Middle Fork). Still further north west-oriented South Fork (Rock Creek) appears to have beheaded Willow Creek headwaters and tributaries. These drainage patterns suggest headward erosion of the deep southeast-oriented Milk River valley captured a south-oriented flood formed anastomosing channel complex. Headward erosion of the Porcupine Creek valley and its tributary valleys then beheaded the anastomosing channel complex’s easternmost flood flow channels and headward erosion of the Willow Creek valley and its tributary valleys next beheaded the newly formed south-southeast oriented flood flow channels to the south-southeast oriented Porcupine Creek tributary valleys. Next headward erosion of the Rock Creek valley and its west-oriented South Fork valley beheaded flood flow channels to the newly eroded Willow Creek valley and its tributary valleys and also to Middle Fork Porcupine Creek.

Rock Creek-Roanwood Creek drainage divide area

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

 

  • Figure 3 illustrates the Rock Creek-Roanwood Creek drainage divide area near the international border. Rock Creek flows in a south-southwest direction in the figure 3 northwest corner. South Creek (South Fork in figure 2) flows in a west-northwest direction from the figure 3 center area to join Rock Creek near the figure 3 west edge. Deep Creek is a southwest-oriented tributary flowing to the figure 3 southwest corner and joining Willow Creek south and west of the figure 3 map area, with Willow Creek then joining Rock Creek. Note how Deep Creek is linked by a through valley (north of Last Chance Reservoir) with the west-northwest oriented South Creek valley. The figure 3 contour interval is ten meters and the through valley floor elevation is between 810 and 820 meters. West of the through valley there is a spot elevation of 842 meters and east of the through valley elevations rise even higher. North of the through valley is another through valley linking the west-northwest and southwest oriented Tomato Creek valley (which drains to South Creek) with the west-northwest oriented South Creek valley. These through valleys are examples of evidence documenting south-oriented flood flow channels captured by headward erosion of west-oriented Rock Creek tributary valleys. Willow Creek originates near the Opheim Air Force Station and flows in a southwest direction to the figure 3 south edge (in southeast quadrant). The southeast-oriented stream originating south and east of Willow Creek in section 6 and flowing to the figure 6 south edge is the Middle Fork Porcupine Creek and will be better seen in figure 4. Note how north and west of Willow Creek, on the same alignment as the southeast-oriented Middle Fork Porcupine Creek, are northwest-oriented South Creek headwaters. A through valley links the northwest-oriented South Creek headwaters valley with the southwest-oriented Willow Creek valley. The through valley floor elevation is between 940 and 950 meters and elevations greater than 960 meters are found immediately to the southwest while elevations greater than 1000 meters are found to the northeast. A similar through valley links the Willow Creek valley with the southeast-oriented Middle Fork Porcupine Creek headwaters valley. These northwest-southeast oriented through valleys provide evidence of a southeast-oriented flood flow channel to what was once the actively eroding Middle Fork Porcupine Creek valley, which was beheaded by headward erosion of the deep southwest-oriented Willow Creek valley, and which was then beheaded and reversed by headward erosion of the deep Rock Creek valley. The resulting reversal of flood flow eroded the northwest and west-northwest oriented South Creek valley. Through valleys in the figure 3 map area are much better seen on more detailed topographic maps, but many additional through valleys exist and provide evidence of southeast-oriented flood flow routes beheaded by headward erosion of west, west-northwest, and northwest oriented Rock Creek tributary valleys.

Willow Creek-Middle Fork Porcupine Creek drainage divide area

Figure 4: Willow Creek-Middle Fork Porcupine Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 4 illustrates the Willow Creek-Middle Fork Porcupine Creek drainage divide area located south and slightly east of the figure 3 map area and includes overlap areas with figure 3. Willow Creek flows in a southwest direction from the figure 4 north edge (east of center) to the figure 4 west edge (south of center). North and west of Willow Creek is south-southwest oriented Lone Tree Coulee, which drains to Willow Creek. And west of Lone Tree Coulee is south-southwest oriented West Fork (Willow Creek) which also drains to Willow Creek (near figure 4 west edge). South of Willow Creek in the figure 4 center and west center area is west-southwest oriented Shaw Coulee, which drains to Willow Creek, and south of Willow Creek in the figure 4 southwest quadrant is west-southwest oriented Chisholm Creek, which flows to the figure 4 west edge (north of southwest corner). South and west of figure 4 Chisholm Creek joins Willow Creek, which then joins Rock Creek. A close look at drainage divides between Willow Creek and its various tributaries reveals several through valleys crossing the drainage divides. For example in the figure 4 southwest quadrant a through valley links a northwest-oriented Willow Creek tributary valley with the west-southwest oriented Chisholm Creek valley. The map contour interval is ten meters and the through valley floor elevation is between 810 and 820 meters. Elevations west of the through valley rise to more than 860 meters and east of the through valley elevations rise even higher. The through valley provides evidence of a south-oriented flood flow channel beheaded and reversed by Willow Creek valley headward erosion. Perhaps an even more interesting through valley links the southwest-oriented Willow Creek valley (near the figure 4 north edge) with headwaters of south-southeast oriented Middle Fork Porcupine Creek, which flows to the figure 4 south edge just west of the southeast corner. The floor of the large through valley has an elevation of between 920 and 930 meters and elevations in the Dahl Hills to the southwest rise to at least 1000 meters while elevations to the northeast near the Opheim Air Force Station (see figure 3) also rise to more than 1000 meters. This broad northwest-southeast oriented through valley, which as seen in figure 3 continues north and west of Willow Creek, is more than 70 meters deep and provides evidence Willow Creek valley headward erosion beheaded south-southeast oriented flood flow to the Middle Fork Porcupine Creek valley. The south-oriented stream flowing to the figure 4 south center edge is West Fork Porcupine Creek. Note how the south-oriented West Fork Porcupine Creek valley is also linked by a through valley to the west-southwest oriented Chisholm Creek and Shaw Coulee valleys. Lowest points on the through valley drainage divide are between 890 and 900 meters and elevations rise to more than 950 meters on either side. This large south-southeast oriented through valley provides additional evidence headward erosion of the Willow Creek valley and its tributary valleys beheaded multiple south-southeast oriented flood flow channels to the Porcupine Creek valley.

Deep Creek-Willow Creek drainage divide area

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

 

  • Figure 5 illustrates the Deep Creek-Willow Creek drainage divide area north and west of the figure 4 map area and south and west of the figure 3 map area and includes overlap areas with figures 3 and 4. Rock Creek flows in a south-southwest direction from Thoeny (near northwest corner) to the figure 5 west edge (south half). Deep Creek flows in a southwest direction from Last Chance Reservoir near the figure 4 north center to the figure 5 south edge (east of southwest corner). Cow Coulee originates in the figure 5 center south of Deep Creek and drains in a south-southwest and southwest direction to the figure 5 south edge (east of Deep Creek). West Fork (Willow Creek) originates south of a west-northwest oriented Deep Creek tributary (south and east of Last Chance Reservoir) and flows in a south-southwest direction to join Willow Creek south of the figure 5 south center edge. South-southwest oriented Lone Tree Coulee is located east of West Fork and southwest-oriented Willow Creek is south and east of Lone Tree Coulee. West-southwest oriented Shaw Coulee is seen in the figure 5 southeast corner. Today the figure 5 area is characterized by closely spaced and converging southwest and south-southwest oriented valleys. But study the drainage divides and it quickly becomes apparent shallow through valleys cross all drainage divides. For example, in the figure 5 northwest quadrant Starbuck Coulee drains in a north-northwest direction to join Rock Creek as a barbed tributary. Note how the north-northwest oriented Starbuck Coulee valley is linked to the Deep Creek valley by a well-defined through valley. South of that through valley is another through valley linking the Deep Creek valley with the Cow Coulee valley, which then converges with the Willow Creek valley.These aligned through valleys provide evidence of a former south or south-southeast oriented flood flow channel captured first by Cow Coulee valley headward erosion, next by Deep Creek valley headward erosion, and still later by Rock Creek valley headward erosion, which reversed flood flow on the northwest end of the beheaded flood flow channel to erode the north-northwest oriented Starbuck Coulee valley. Many more through valleys can be seen in the figure 5 map area such as along the Rock Creek-Deep Creek drainage divide in the figure 5 southwest quadrant. These through valleys provide evidence of south-southeast oriented flood flow channels captured by headward erosion of the southwest and south-southwest oriented Rock Creek, Willow Creek, and tributary valleys.

Chisholm Creek-West Fork Porcupine Creek drainage divide area

Figure 6: Chisholm Creek-West Fork Porcupine Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 6 illustrates the Chisholm Creek-West Fork Porcupine Creek drainage divide area located south and slightly west of the figure 4 map area and including overlap areas with figure 4. Chisholm Creek flows in a west-southwest and west direction to the figure 6 west center edge. North of Chisholm Creek in the figure 6 northwest quadrant Willow Creek (unlabeled) flows in a southwest and west direction to the figure 6 west edge (just south of northwest corner). Shaw Coulee joins Willow Creek near the figure 6 north edge. West of figure 6 Willow Creek turns to flow in a south-southwest direction to join south-oriented Rock Creek. Just north of the figure 6 southwest corner south-southwest and west oriented headwaters of Drifter Creek (only the word Creek is visible) flow to Willow Creek, which then joins Rock Creek. Note how the Drifter Creek headwaters valley is linked by a through valley with the Chisholm Creek valley. The south-southeast oriented stream in the figure 6 east half flowing from the northeast quadrant to the south edge is the West Fork Porcupine Creek. As previously described the south-southeast oriented West Fork Porcupine Creek valley is linked by a through valley with the Chisholm Creek and the Shaw Coulee valleys. The through valley floor elevation at the drainage divide are between 890 and 900 meters and elevations greater than 950 meters are found on both sides of the through valley. Further east is an unlabeled southeast-oriented stream flowing to the figure 6 south center edge. This stream is Buggy Creek (which will be seen again in figure 8) and south of the figure 8 map area Buggy Creek turns to flow in a south-southwest direction, although a southeast-oriented through valley links the southeast-oriented Buggy Creek valley segment with the southeast-oriented Dry Fork Porcupine Creek valley (this will be seen in figure 8). Note in figure 6 how the southeast-oriented Buggy Creek headwaters valley is linked by a through valley with the northwest-oriented Long Coulee valley, which drains to Chisholm Creek. The through valley floor elevation appears to be between 910 and 920 meters (probably closer to 920 meters) and elevations greater than 950 meters can be found on either side of the through valley. This through valley is further evidence headward erosion of deep south-southwest oriented valleys from the newly eroded Milk River valley captured multiple southeast and south-southeast oriented flood flow channels moving flood waters to the actively eroding Porcupine Creek valley system, such as might be found in a large southeast and south-southeast oriented anastomosing channel complex. The northwest-oriented Long Coulee valley was eroded by a reversal of flood flow on the northwest end of the southeast-oriented flood flow channel, which was beheaded by headward erosion of the deep Chisholm Creek valley.

Detailed map of Chisholm Creek-West Fork Porcupine Creek drainage divide area

Figure 7: Detailed map of Chisholm Creek-West Fork Porcupine Creek 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 Chisholm Creek-West Fork Porcupine Creek drainage divide area seen in less detail in figure 6 above. West Fork Porcupine Creek is labeled and flows in a south-southeast and south direction in the figure 7 east half. Chisholm Creek flows in a southwest and west direction across the figure 7 northwest corner. Note how Chisholm Creek has a west-northwest oriented tributary in section 5 near the figure 7 north edge and a northwest-oriented tributary in sections 7 and 8, which also flows across the section 17 northeast corner. In the southwest quadrant of section 4 (near figure 7 north edge) a through valley links the west-northwest oriented Chisholm Creek tributary valley with the south-southeast oriented West Fork Porcupine Creek valley. Further south in the north half of section 16 another through valley links the northwest-oriented Chisholm Creek tributary valley with the south-oriented West Fork Porcupine Creek valley. The map contour interval is 10 feet with some dotted 5-foot contour lines and floors of both through valleys at the drainage divides are between 2940 and 2950 feet in elevation. Between the two through valleys is a hill which rises to 3002 feet in elevation. But, notice that elevations rise to 3150 feet in the figure 7 northeast corner and a spot elevation of 3134 feet is located in section 19 near the figure 7 southwest corner. These high elevations define a much broader and deeper through valley than the through valleys in sections 4 and 16 first appear to be. The broader and deeper through valley spans the diagonal distance between the high elevations mentioned, which is approximately 4.5 miles, and is approximately 200 feet deep at its deepest points. This large south-southeast oriented through valley is a remnant of what was once a major south-southeast oriented flood flow channel, which was just one of several large south-southeast oriented flood flow channels crossing what is today the Rock Creek-Porcupine Creek drainage divide area. Headward erosion of the deep south-southwest oriented Rock Creek valley and its southwest and west-oriented tributary valleys, such as the Chisholm Creek valley, systematically captured the south-southeast oriented flood flow and diverted the water to what was then the newly eroded Milk River valley.

Buggy Creek-Dry Fork Porcupine Creek drainage divide area

Figure 8: Buggy Creek-Dry Fork Porcupine Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 8 illustrates the Buggy Creek-Dry Fork Porcupine Creek drainage divide area located south of the figure 6 map area and includes overlap areas with figure 6. The West Fork Porcupine Creek flows in a south-southeast direction from near the figure 8 north edge to the figure 8 east edge (just north of southeast corner). In the figure 8 southeast quadrant Dry Fork Porcupine Creek flows in a southeast direction to the figure 8 south edge, just west of the southeast corner. Buggy Creek flows in a southeast direction in the figure 8 north center area and then turns to flow in a south-southwest direction to the figure 8 south edge, just west of center, and then continues south of the figure 8 map area to join the Milk River. West of Buggy Creek is south-southwest oriented Canyon Creek, which south of the figure 8 map area joins Buggy Creek. West of Canyon Creek is south-southeast oriented West Fork, which joins Canyon Creek south of the figure 8 map area. Drifter Creek headwaters flow in a south-southwest and west direction in the figure 8 northwest corner area. Southwest-oriented headwaters of Eagle Creek can be seen in the figure 8 west center edge area. Drifter Creek and Eagle Creek both flow to south-southwest oriented Willow Creek, which is located west of the figure 8 map area and which flows to south-oriented Rock Creek. Headwaters of northwest-oriented Long Coulee, which flows to Chisholm Creek, can be seen along the figure 8 north edge (west of center) and are aligned with the southeast-oriented Buggy Creek headwaters valley, which is also aligned with the southeast-oriented Dry Fork Porcupine Creek valley. Note how a northwest-southeast oriented through valley links the Dry Fork Porcupine Creek valley with the Buggy Creek headwaters valley. The map contour interval is ten meters and the through valley floor elevation is between 890 and 900 meters. Elevations on either side rise to more than 910 meters. Also note how the southeast-oriented Buggy Creek headwaters valley has been eroded across what were once two south-southwest oriented valleys leading to the Canyon Creek valley. Through valleys along these south-southwest oriented valley routes link the southeast-oriented Buggy Creek valley with the Canyon Creek headwaters and also with the south-southeast oriented West Fork Porcupine Creek valley. These intersecting valleys were probably eroded as a south-southwest oriented anastomosing channel complex beheaded a south-southeast oriented anastomosing channel complex. The south-southeast oriented anastomosing channel complex was supplying flood water to what was then the actively eroding Porcupine Creek valley system, which had eroded headward from the newly eroded Missouri River valley. The south-southwest oriented anastomosing channel complex may have eroded headward from newly eroded deep valleys south of the Milk River valley, although details cannot be determined in this essay.

Eagle Creek-Canyon Creek drainage divide area

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

 

  • Figure 9 illustrates the Eagle Creek-Canyon Creek drainage divide area south and west of the figure 8 map area and includes overlap areas with figure 8. Rock Creek flows in a south direction near the figure 9 west edge and is joined by south-southwest oriented Willow Creek near the figure 9 west center edge. Eagle Creek originates near the figure 9 north center edge and flows in a southwest direction to join Willow Creek in the figure 9 northwest quadrant. Ash Coulee is a southwest and northwest-oriented Eagle Creek tributary and Spring Coulee is a west and northwest-oriented Eagle Creek tributary. The south-oriented stream located south of Spring Coulee and flowing to the figure 9 south edge east of Rock Creek is Lime Creek. Note how the south-oriented Lime Creek valley is linked by a through valley with the northwest-oriented Spring Coulee valley. The northwest-oriented Spring Coulee and Ash Coulee valley segments were eroded by reversals of flood flow on northwest ends of beheaded southeast and south-oriented flood flow channels, which were beheaded by Eagle Creek valley headward erosion. Buggy Creek flows in a south-southwest direction from the figure 9 east edge (north half) to the figure 9 south edge (near southeast corner). West of Buggy Creek is Canyon Creek, which flows from near the Forsman Reservoir area in the figure 9 northeast quadrant to the figure 9 south edge (just west of Buggy Creek) and then joins Buggy Creek south of the figure 9 map area. The West Fork of Canyon Creek flows from near Newberry Flat (in northeast quadrant) to join Canyon Creek in the figure 9 southeast quadrant. Note how Newberry Flat is in fact the floor of a through valley linking the west-oriented Eagle Creek valley with the south-southeast oriented West Fork Canyon Creek valley. The map contour interval is ten meters and the drainage divide at Newberry Flat has an elevation of between 850 and 870 meters (depending on where you look). Newberry Flat stands more than 50 meters higher than the Eagle Creek valley immediately to the west. However north and east of Newberry Flat elevations rise to more than 940 meters in the figure 9 northeast corner and south and west of Newberry Flat elevations rise to more than 910 meters. Other through valleys suggest complicated flood flow patterns as headward erosion of Rock Creek tributary valleys captured south-southeast oriented flood flow channels, however the 40-60 meter deep Newberry Flat through valley provides evidence of a major south-southeast oriented flood flow channel.

Rock Creek-Unger Coulee drainage divide area

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

 

  • Figure 10 illustrates the Rock Creek-Unger Coulee drainage divide area located south of the figure 9 map area and includes overlap areas with figure 9. The southeast-oriented Milk River valley is located in the figure 10 southwest quadrant and the Milk River meanders in a southeast direction near the figure 10 southwest corner. Rock Creek flows in a south direction along the figure 10 northwest quadrant west edge and then turns to flow in a south-southwest direction to join the Milk River near Hinsdale, which is located just west of the figure 10 southwest corner. Lime Creek originates in the figure 10 northwest quadrant as a southwest, northwest, southwest-oriented stream and then turns to flow in a south-southeast direction to join the Milk River south of the figure 10 south edge. Black Coulee is a south-southeast oriented drainage route between Lime Creek and Unger Coulee, which is linked to the northwest-oriented Lime Creek valley segment by a well-defined through valley just east of Blacktail Coulee. The through valley floor elevation is between 790 and 800 meters and hills on either side rise to more than 830 meters. Unger Coulee is the prominent south-oriented drainage route extending in a south direction from the figure 10 north center to the south center edge. Just east of Unger Coulee is south-oriented Canyon Creek, which joins south-southwest oriented Buggy Creek south and east of the figure 10 center (west-oriented Crooked Creek joins Buggy Creek near where Canyon Creek and Buggy Creek meet). Note how Crooked Creek flows in a south-southwest direction from the figure 10 northeast quadrant and then abruptly turns to flow in a west-southwest direction to join Buggy Creek. Also note how a well-defined through valley links the south-southwest oriented Crooked Creek valley with the south-oriented Spring Creek valley. Through valleys, such as the two mentioned here, provide evidence of what were once diverging flood flow channels. Converging valleys as seen in the figure 10 map area provide evidence of what were once converging flood flow channels. Probably one of the most impressive features of the figure 10 map area is the abundance of closely spaced and converging and diverging southeast and south-southeast oriented drainage routes between Rock Creek and Unger Coulee and of south-oriented drainage routes east of Unger Coulee. These closely spaced converging and diverging drainage routes are evidence of a large south-oriented anastomosing channel complex, which was beheaded by headward erosion of west, southwest, and south-southwest oriented Rock Creek tributary valleys in the north.

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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