Tongue River-Pumpkin Creek drainage divide area landform origins, southeast Montana, USA

· Montana, Tongue River
Authors

A geomorphic history based on topographic map evidence

Abstract

The Tongue River-Pumpkin Creek drainage divide area is located in eastern Montana, USA. Although detailed topographic maps of the Tongue River-Pumpkin Creek drainage divide area have been available for more than fifty years detailed map evidence has not previously been used to interpret the region’s geomorphic history. The interpretation provided here is based entirely on topographic map evidence. The Tongue River-Pumpkin Creek drainage divide area is interpreted to have been eroded during immense southeast-oriented flood events, the first of which flowed on a topographic surface at least as high as the highest points in the present-day drainage divide area. Flood erosion across the drainage divide ended when headward erosion of the deep Tongue River valley captured all southeast-oriented flood flow.

Preface:

The following interpretation of detailed topographic map evidence is provided as evidence in the Missouri River drainage basin landform origins research project, which is compiling similar evidence for all major drainage divides contained within the Missouri River drainage basin and for all major drainage divides with and within certain adjacent drainage basins. The research project is interpreting evidence in the context of a previously unexplored geomorphology paradigm, which is briefly described in the introduction below. Project essays are listed on the sidebar category list under their appropriate Missouri River tributary drainage basin, Missouri River segment drainage basin (by state), and/or state in which the Missouri River drainage basin is located.

Introduction:

  • The purpose of this essay is to use topographic map interpretation methods to explore eastern Montana Tongue River-Pumpkin Creek drainage divide area landform origins. 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 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 in a comment here.
  • This essay is also exploring a 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 similar essays is a thick North American ice sheet, comparable in thickness to the present day Antarctic ice sheet, occupied approximately the North American region usually recognized to have been glaciated and through its weight and erosive actions created a “deep” North American “hole”, 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 Tongue River-Pumpkin Creek drainage divide area landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Tongue River-Pumpkin Creek drainage divide area location map

Figure 1: Tongue River-Pumpkin Creek drainage divide area location map. National Geographic Society map digitally presented using National Geographic Society TOPO software.

Figure 1 provides a Tongue River-Pumpkin Creek drainage divide area location map and illustrates a region in eastern Montana. The state of North Dakota is located in figure 1 northeast corner and the state of South Dakota is located in the figure 1 southeast corner. The state of Wyoming is south of Montana and west of South Dakota. The Yellowstone River flows in a northeast direction to Glendive, Montana located in the figure 1 northeast quadrant. The Tongue River flows northeast from the figure 1 south edge and Tongue River Reservoir and south of Miles City, Montana turns northwest to join the northeast-oriented Yellowstone River as a barbed tributary at Miles City. Pumpkin Creek originates near Sonnette, Montana and flows north-northeast and northwest to join the Tongue River south of Miles City. Figure 1 illustrates southeast and northwest-oriented Yellowstone River tributaries. The southeast and northwest-orientation of tributary valleys is evidence the northeast-oriented Yellowstone River valley eroded southwest across multiple southeast-oriented flood flow routes, such as might be found in a large-scale flood-formed anastomosing channel complex. Northwest-oriented tributary valleys were eroded by reversed flood flow on northwest ends of beheaded flood flow channels. Because channels were anastomosing (meaning they were interconnected) reversed flood flow on beheaded flood flow channels often captured yet to be beheaded southeast-oriented flood flow from flood flow channels further to the southwest. Such captures of yet to be beheaded flood flow often helped erode significant northwest-oriented tributary valleys. Based on the northwest-southeast orientation of tributary streams, landform evidence illustrated in this essay is interpreted in the context of an immense southeast-oriented flood flowing across the entire figure 1 map area and which was systematically captured and diverted further and further to the northeast by headward erosion of deep valleys eroded into a topographic surface at least as high as the figure 1 region highest elevations today. In the figure 1 map region headward erosion of the north-northeast oriented Pumpkin Creek valley upstream from the northwest-oriented Pumpkin Creek-Tongue River valley segment is evidence the Pumpkin Creek valley eroded south-southwest to capture southeast-oriented flood flow. The northeast-oriented Tongue River valley upstream from the northwest-oriented Tongue River valley near Miles City next captured the southeast-oriented flood flow and then headward erosion of the Yellowstone River valley captured the same southeast-oriented flood flow routes and diverted the flood waters more directly to the northeast-oriented Yellowstone River valley (downstream from Miles City, Montana). Detailed maps below provide evidence supporting this interpretation. The Yellowstone River-Tongue River drainage divide area essay, Big Dry Creek-Yellowstone River drainage divide area essay and the Musselshell River-Yellowstone River drainage divide area essay describe regions located west and north of the Tongue River-Pumpkin Creek drainage divide area discussed here and can be found under Yellowstone River on the sidebar category list. The Pumpkin Creek-Mizpah Creek drainage divide area essay and in the Mizpah Creek-Powder River drainage divide area essay both located east of the area discussed here and can be found under Powder River on the sidebar category list.

Tongue River-Pumpkin Creek drainage divide area detailed location map

Figure 2: Tongue River-Pumpkin Creek drainage divide area detailed location map. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 2 illustrates a somewhat more detailed map of the Tongue River-Pumpkin Creek drainage divide area discussed here. Rosebud, Custer, Fallon and Carter Counties are located in Montana. South of Custer County is Powder River County. The Tongue River-Pumpkin Creek drainage divide area discussed here is located primarily in Custer County and northern Powder River County. The Yellowstone River flows east and northeast through Miles City to the figure 2 north edge. The north and northeast-oriented Tongue River flows from the figure 2 southwest quadrant and then turns to flow northwest before joining the northeast-oriented Yellowstone River at Miles City. Pumpkin Creek originates south of the figure 2 map area and flows north in the figure 2 south center and then turns northwest to join the northwest-oriented Tongue River valley segment. Figure 2 shows numerous southeast and northwest-oriented Yellowstone River and Tongue River tributaries and some southeast and northwest-oriented Pumpkin Creek tributaries. This northwest-southeast drainage alignment is evidence the north-oriented Pumpkin Creek valley eroded south and south-southwest across an immense southeast-oriented flood to capture flood waters and to divert flood waters north. Further, the drainage alignment is evidence the northeast-oriented Tongue River valley subsequently eroded southwest to capture the same southeast-oriented flood flow. Subsequently the Yellowstone River valley eroded southwest and west to capture the same southeast-oriented flood flow and divert the flood water more directly to the northeast. The southeast-oriented tributary valleys were eroded by southeast-oriented flood flow moving into the newly eroded and deep Pumpkin Creek, Tongue River and Yellowstone River valleys. The northwest-oriented tributary valleys were eroded by reversed flood flow on the northwest ends of beheaded southeast-oriented flood flow routes. Because flood waters move in and erode anastomosing (or interconnected) channels reversed flood flow on a beheaded flood flow route could capture flood flow from yet to be beheaded flood flow routes. Such captures of yet to be beheaded flood flow could enable the reversed flood flow routes to erode much deeper and larger northwest-oriented valleys than might otherwise be possible. Often evidence for such flow reversals and captures can be found on detailed topographic maps. Detailed maps below focus on evidence in the Ash Creek, Foster Creek, Beaver Creek, and Little Pumpkin Creek areas.

North end of the Tongue River-Pumpkin Creek drainage divide area

Figure 3: North end of the Tongue River-Pumpkin Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the north end of the Tongue River-Pumpkin Creek drainage divide area. The Tongue River flows northeast and north from the figure 3 southwest corner. Pumpkin Creek flows northwest from the figure 3 southeast corner to join the Tongue River along the figure 3 north edge. Tributaries to the northeast-oriented Tongue River are almost all southeast-oriented from the west and northwest-oriented from the east. This orientation of Tongue River tributaries is evidence the Tongue River valley eroded southwest across multiple southeast-oriented flood flow routes such as might be found in a southeast-oriented anastomosing channel complex. Tributaries to the northwest-oriented Pumpkin Creek valley are predominantly northeast-oriented from the south and west or southwest-oriented from the north, although in the figure 3 southeast corner La Grange Creek is southeast-oriented. The northwest-oriented Pumpkin Creek valley segment (and the northwest-oriented Tongue River valley segment downstream from figure 3) originated as a reversal of flow on the northwest end of a southeast-oriented flood flow route beheaded by headward erosion of the deep Yellowstone River valley northwest of the figure 3 map area. Reversed flood flow then eroded valleys to the southwest to capture yet to be beheaded flood flow routes further to the southwest. The northeast-oriented Pumpkin Creek tributary valleys are linked by through valleys to northwest-oriented Tongue River tributary valleys, which is evidence headward erosion of the deep northeast-oriented Tongue River valley beheaded southeast-oriented flood flow routes that had been captured by reversed flood flow moving on the present day northwest-oriented Pumpkin Creek valley alignment. The area east of the Pumpkin Creek valley was discussed in the Pumpkin Creek-Mizpah Creek drainage divide essay. The west and southwest-oriented Pumpkin Creek tributaries seen in the figure 3 northeast quadrant originated as reversals of east-oriented flood flow that had been captured by headward erosion of the deep Mizpah Creek valley to the east of figure 3.

Tongue River-Pumpkin Creek drainage divide in Ash Creek north area

Figure 4: Tongue River-Pumpkin Creek drainage divide in Ash Creek north area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates the Tongue River-Pumpkin Creek drainage divide area south of the figure 3 map area and includes overlap areas with figure 3. The northeast-oriented Tongue River is located in the figure 4 northwest corner. North-northeast oriented Pumpkin Creek is located in the figure 4 southeast corner. Northwest-oriented Ash Creek flows from the figure 4 south edge (center east) to join the northeast-oriented Tongue River in the figure 4 northwest quadrant. Note how Tongue River tributaries are southeast-oriented from the northwest and northwest-oriented from the southeast. Pumpkin Creek tributaries from the west are southeast or east-southeast oriented and from the east are northwest-oriented (although they cannot be seen here except in the figure 4 southeast corner). Note how northeast-oriented tributary valleys eroded southwest from the northwest-oriented Ash Creek valley. These northeast-oriented tributary valleys eroded southwest from reversed flood flow on the northwest end of the newly beheaded Ash Creek alignment to capture yet to be beheaded southeast-oriented flood flow routes further to the southwest. Figure 5 below illustrates the northeast-oriented Ash Creek headwaters area valley, which also eroded southwest to capture yet to be beheaded southeast-oriented flood flow routes. The capture of significant amounts of yet to be beheaded southeast-oriented flood flow provided sufficient flood water to the newly reversed flood flow on the Ash Creek alignment to erode a significant northwest-oriented valley. Prior to being beheaded and reversed flood flow on the Ash Creek alignment was moving southeast to the newly eroded north-northeast oriented Pumpkin Creek valley. Note also through valleys linking other northwest-oriented Tongue River tributary valleys with southeast-oriented Pumpkin Creek tributary valleys. These through valleys provide evidence that southeast-oriented flood waters once flowed in multiple channels across the present day Tongue River-Pumpkin Creek drainage divide to what was then the newly eroded north-northeast oriented Pumpkin Creek valley. The Tongue River-Pumpkin Creek drainage divide was subsequently created by headward erosion of the northeast-oriented Tongue River valley, which beheaded the southeast-oriented flood flow routes to Pumpkin Creek causing flood waters on the northwest ends of the beheaded flood flow routes to reverse flow direction and to flow northwest to the newly eroded and deeper northeast-oriented Tongue River valley.

Tongue River-Pumpkin Creek drainage divide in Ash Creek south area

Figure 5: Tongue River-Pumpkin Creek drainage divide in Ash Creek south area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Tongue River-Pumpkin Creek drainage divide area south of the figure 4 map area and includes overlap areas with figure 4. The northeast oriented Tongue River is located in the figure 5 northeast corner. North-northeast oriented Pumpkin Creek is located in the figure 5 southeast corner. Ash Creek flows northeast toward the figure 5 east center and then turns northwest to flow to the figure 5 north edge (center east).  Note how east-oriented Mc Fee Creek in the figure 5 south center, which flows to northeast and northwest-oriented Ash Creek, provides a link between northwest-oriented Haddow Creek headwaters and  northeast-oriented Ash Creek headwaters. Northeast of Haddow Creek note northwest-oriented Brown Creek, which is similarly linked to northeast-oriented Butte Creek, which flows to northwest-oriented Ash Creek. And, northeast of Brown Creek is northwest-oriented Jack Creek (labeled “Creek” in figure 5), which provides a similar link to northeast-oriented Winter Creek, which also flows to the northwest-oriented Ash Creek valley.  These linkages provide evidence that reversed flood flow on what was then the newly beheaded southeast-oriented flood flow route using the Ash Creek alignment captured flood flow from multiple yet to be beheaded southeast-oriented flood flow routes further to the southwest. Headward erosion of the northeast-oriented Winter Creek valley captured yet to be beheaded southeast-oriented flood flow on the Jack Creek alignment, headward erosion of the northeast-oriented Butte Creek valley captured yet to be beheaded southeast-oriented flood flow on the Brown Creek alignment, and headward erosion of the northeast-oriented Ash Creek headwaters valley and the east-oriented Mc Fee Creek valley captured yet to be beheaded flood flow on the Haddow Creek alignment. Flood flow on each of these routes was then beheaded in sequence as the deep Tongue River valley eroded southwest. Once beheaded, flood waters on the northwest ends of the beheaded flood flow routes reversed flow direction to flow northwest to the newly eroded Tongue River valley. Note also on figure 5 through valleys on either side of Kirkpatrick Hill in the figure 5 southeast corner area that link the northwest-oriented Ash Creek valley with the north-northeast oriented Pumpkin Creek valley. These through valleys and other similar through valleys provide evidence southeast-oriented flood flow once moved from the present day Ash Creek drainage basin to the present day Pumpkin Creek drainage basin.

Tongue River-Pumpkin Creek drainage divide in Foster Creek north area

Figure 6: Tongue River-Pumpkin Creek drainage divide in Foster Creek north area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates Tongue River tributaries in the region south and west of the figure 5 map area and includes overlap areas with figure 5. The northeast-oriented Tongue River flows from the figure 6 west edge to the figure 6 north edge. Northwest-oriented Haddow Creek is located in the figure 6 northeast quadrant. Northwest-oriented Foster Creek flows from the figure 6 south edge across the figure 6 center to join the Tongue River just north of the figure 6 north edge. Northwest-oriented Lay Creek is the major northwest-oriented Tongue River tributary in the figure 6 southwest quadrant. Note how Tongue River tributaries in figure 6 are southeast-oriented from the northwest and northwest-oriented from the southeast. This northwest-southeast tributary orientation is evidence the deep northeast-oriented Tongue River valley eroded southwest across multiple southeast-oriented flood flow channels such as might be found in a southeast-oriented anastomosing channel complex. Figure 6 evidence is best explained in the context of an immense southeast-oriented flood flowing on a topographic surface at least as high as the highest figure 6 elevations today. Flood waters were captured by headward erosion of the deep north-northeast oriented Pumpkin Creek valley to the east of figure 6. The deep Pumpkin Creek valley captured the southeast-oriented flood flow and diverted the water north and northwest to what was then the newly eroded northeast-oriented Yellowstone River valley. Subsequently headward erosion of the deep northeast-oriented Tongue River valley captured the southeast-oriented flood flow and diverted the flood waters more directly to the northeast-oriented Yellowstone River valley. Headward erosion of the Tongue River valley proceeded from the northeast to the southwest and southeast-oriented flood flow routes to the north-northeast oriented Pumpkin Creek valley were beheaded and reversed from northeast to southwest (flood flow on the Haddow Creek alignment was beheaded and reversed before flood flow on the Foster Creek alignment, which was beheaded before flood flow on the Lay Creek alignment was beheaded and reversed). Reversed flood flow on newly beheaded flood flow routes often captured flood flow from yet to be beheaded flood flow routes, and such captures helped erode significant northwest-oriented valleys.

Tongue River-Pumpkin Creek drainage divide in Foster Creek south area

Figure 7: Tongue River-Pumpkin Creek drainage divide in Foster Creek south area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Tongue River-Pumpkin Creek drainage divide area south and east of the figure 6 map area and includes overlap areas with figure 6. North and north-northeast oriented Pumpkin Creek is located in the figure 7 southeast corner and east center. Note northwest-oriented tributaries to Pumpkin Creek from the east and southeast oriented Pumpkin Creek tributaries from the northwest. Foster Creek originates in the figure 7 southwest quadrant and flows east and then north-northeast across the figure 7 center before turning northwest to flow to the figure 7 north edge. Northwest-oriented headwaters of the northwest-oriented North Fork of Foster Creek are located in the figure 7 north center. Note northwest-oriented Jandell Creek and an unnamed northwest-oriented Foster Creek tributary both flowing to Foster Creek at the elbow of capture where Foster Creek turns from being north-northeast oriented to being northwest-oriented. The northwest-oriented Jandell Creek valley and the unnamed northwest-oriented Foster Creek tributary valley are linked to the southeast oriented Ranch Creek and Flat Butte Creek valleys, which drain to the north-northeast oriented Pumpkin Creek valley. Also note how the east-oriented Lone Tree Creek valley, which drains to the north-oriented Pumpkin Creek valley, is linked to the Foster Creek south elbow of capture where Foster Creek turns from being east-oriented to being north-northeast oriented. These linkages are evidence flood waters once flowed southeast and east from what is today the Foster Creek drainage basin to the north- and north-northeast oriented Pumpkin Creek drainage basin. Reversal of flood flow on the Foster Creek alignment created the present day Foster Creek-Pumpkin Creek drainage divide. The north-northeast oriented Foster Creek valley segment probably eroded south-southwest to capture southeast and east oriented flood water that had been moving to erode the Lone Tree Creek valley.

Tongue River-Pumpkin Creek drainage divide in Beaver Creek west area

Figure 8: Tongue River-Pumpkin Creek drainage divide in Beaver Creek west area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates Tongue River tributaries in the Tongue River-Pumpkin Creek drainage divide area south and west of the figure 7 map area and includes overlap areas with figure 7. The northeast-oriented Tongue River is located in the figure 8 northwest corner. Northwest-oriented Beaver Creek flows from the figure 8 south edge (center east) to join the Tongue River near the figure 8 west center edge. Northwest-oriented Liscom Creek flows from the figure 8 east center area to the figure 8 north edge. Note how northeast-oriented Liscom Creek tributaries are linked by through valleys with southwest-oriented Beaver Creek tributaries. These through valleys are evidence flood waters once flowed from the Beaver Creek valley northeast along multiple channels to the northwest-oriented Liscom Creek valley. At that time southeast-oriented flood flow on the Liscom Creek alignment had just been beheaded and reversed, while headward erosion of the deep northeast-oriented Tongue River valley had yet to behead southeast-oriented flood flow on the Beaver Creek alignment. Reversed flood flow on the Liscom Creek alignment captured the yet to be beheaded southeast-oriented flood flow on the Beaver Creek alignment and the captured flood waters moved northeast from the Beaver Creek alignment to the Liscom Creek alignment. Elevations of the through valley floors above the present day Beaver Creek and Liscom Creek valley floors provides a measure of the erosion accomplished as flood waters were being captured and reversed to flow to the newly eroded northeast-oriented Tongue River valley. The source of the southeast-oriented flood flow cannot be determined from evidence presented here. However, the Missouri River drainage basin landform origins research project essays (published on this website) as a group can be used to trace flood waters headward towards their source. A logical flood water source would be rapid melting of a thick North American ice sheet that through erosive actions and its weight was located in a deep “hole” (probably occupying approximately the location of the continent usually recognized to have been glaciated). Not only would rapid melting of such an ice sheet explain the immense quantities of flood water involved, but it would also explain why deep valleys were eroding headward to capture south-oriented flood waters and to divert the flood waters further and further northeast (into space in the “deep” hole the rapidly melting thick North American ice sheet had formerly occupied).

Tongue River-Pumpkin Creek drainage divide in Beaver Creek east area

Figure 9: Tongue River-Pumpkin Creek drainage divide in Beaver Creek east area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Tongue River-Pumpkin Creek drainage divide area south and east of the figure 8 map area and includes overlap areas with figure 8. Northwest-oriented Beaver Creek flows to the figure 9 northwest corner. North-oriented Pumpkin Creek is located in the figure 9 southeast corner. East of the north-south oriented Elk Ridge in the figure 9 east center is north and northeast-oriented Little Pumpkin Creek. The present day Tongue River-Pumpkin Creek drainage divide in figure 9 is a north-south ridge located slightly west of the figure 9 center. There are shallow valleys or saddles eroded into the ridge and those saddles provide evidence water once flowed across the ridge (or present day drainage divide). Southeast-oriented Pumpkin Creek tributaries in the figure 9 southeast corner and east center area provide evidence the north-oriented Pumpkin Creek valley eroded south across southeast-oriented flood flow. The southeast-oriented flood flow came from northwest of the present day Tongue River-Pumpkin Creek drainage divide, which means the Pumpkin Creek valley was being eroded into a topographic surface at least as high as the highest figure 9 elevations today. Subsequently the deep Little Pumpkin Creek valley eroded southwest and south into that same high level topographic surface to capture southeast-oriented flood flow moving on the Beaver Creek alignment. Probably some type of resistant rock prevented deep valleys from being eroded headward into the present day drainage divide area. However, when the deep northeast-oriented Tongue River valley beheaded southeast-oriented flood flow on the Beaver Creek alignment, the reversed flood waters on the northeast end of the beheaded flood flow route captured yet to be beheaded flood flow from further to the southwest and the captured flood waters systematically eroded north- and northeast-oriented tributary valleys to the northwest-oriented Beaver Creek valley. Headward erosion of the tributary valleys created the present day ridge that serves as the Tongue River-Pumpkin Creek drainage divide.

Little Pumpkin Creek-Pumpkin Creek drainage divide area

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

Figure 10 illustrates the Little Pumpkin Creek- Pumpkin Creek drainage divide area west of the figure 9 map area and includes overlap areas with figure 9. Little Pumpkin Creek flows north and northeast in the figure 10 west half. North-northeast oriented Pumpkin Creek is located slightly east of the figure 10 center. Note most Pumpkin Creek tributaries from the east are northwest oriented while most Pumpkin Creek tributaries from the west are southeast-oriented. Exceptions are northeast-oriented Little Pumpkin Creek and its northeast-oriented Cottonwood Creek tributary. The northwest-southeast orientation of Pumpkin Creek tributaries is evidence the deep Pumpkin Creek valley eroded headward across multiple southeast-oriented flood flow routes, such as might be found in a southeast-oriented anastomosing channel complex. As previously mentioned the deep Pumpkin Creek valley eroded south into a topographic surface at least as high the highest regional elevations today. Flood waters lowered the regional topographic surface to produce the landscape seen today. Note also how the north oriented Little Pumpkin Creek valley has northwest-oriented tributaries especially at the north end of Elk Ridge, which is today the Little Pumpkin Creek-Pumpkin Creek drainage divide. Three named northwest-oriented Little Pumpkin Creek tributaries are Bridge Creek, Coal Creek, and Buckberry Creek. These northwest-oriented tributaries are evidence that headward erosion of the deep north and northeast-oriented Little Pumpkin Creek valley beheaded and reversed southeast-oriented flood flow routes that were moving flood waters southeast across the present day Elk Ridge to the north-oriented Pumpkin Creek valley. East and northeast-oriented Little Pumpkin Creek tributary valleys were eroded by captured flood flow that had been flowing southeast along the Beaver Creek alignment. This captured flood flow moved east and northeast to what was then the actively eroding Little Pumpkin Creek valley headcut. As mentioned previously, resistant rock along the present day Tongue River-Pumpkin Creek drainage divide and along present day Elk Ridge appears to prevented flood waters from eroding deep valleys across the present day drainage divides, which caused flood waters to erode somewhat different valleys here than were eroded further to 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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