A geomorphic history based on topographic map evidence

The Musselshell River-Yellowstone River drainage divide area discussed here is located primarily in Rosebud and Treasure Counties, Montana. The Musselshell River flows east and north to the east oriented Missouri River. The Yellowstone River flows east and northeast to join the Missouri River. Although detailed topographic maps of the Musselshell River-Yellowstone River 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 Musselshell River-Yellowstone River 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 east and north-oriented Musselshell River valley captured all southeast-oriented flood flow.

Introduction:

• The purpose of this essay is to use topographic map interpretation methods to explore Montana Treasure and Rosebud County area Musselshell River-Yellowstone River drainage divide 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 Musselshell River-Yellowstone River drainage divide area landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Musselshell River-Yellowstone River drainage divide area location map

Figure 1: Musselshell River-Yellowstone River drainage divide area location map (select and click on maps to enlarge). National Geographic Society map digitally presented using National Geographic Society TOPO software.

Figure 1 provides a Musselshell River-Yellowstone River drainage divide area location map which is located entirely in Montana. The Yellowstone River flows east in the figure 1 southeast quadrant to Billings and then flows in a northeast direction to Miles City, located near the figure 1 east edge. The Missouri River flows east from the figure 1 northwest quadrant to Fort Peck Lake, which is a reservoir flooding the Missouri River valley. The Musselshell River originates west of figure 1 and flows east-southeast to Lavinia where it turns northeast to flow to Melstone. At Melstone the Musselshell River turns north-northwest to flow to the Missouri River at Fort Peck Lake, which extends south into the Musselshell River valley. East of the north-northwest oriented Musselshell River valley is the east- and north-oriented Little Dry Creek and Big Dry Creek drainage basin, which drains to the Missouri River. This essay addresses Musselshell River-Yellowstone River drainage divide area evidence located west of Big Porcupine Creek (which flows southeast to the Yellowstone River west of Forsyth) and east of a line between Melstone (on the Musselshell River) and Bighorn (on the Yellowstone River). Figure 1 illustrates southeast and northwest-oriented Yellowstone River  and Musselshell 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 here 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 Yellowstone River valley first captured southeast-oriented flood flow and diverted the flood waters northeast, and subsequently headward erosion of the east-oriented Missouri River valley and north-northwest oriented Musselshell River valley captured the same southeast-oriented flood flow and diverted the flood waters still further to the north and east. Detailed maps below provide evidence supporting this interpretation. The Big Dry Creek-Yellowstone River drainage divide area essay described the region located immediately east of the Musselshell River-Yellowstone River drainage divide area described here and can be found under Big Dry Creek on the sidebar category list.

Musselshell River-Yellowstone River drainage divide area detailed location map

Figure 2: Musselshell River-Yellowstone River 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 Musselshell River-Yellowstone River drainage divide area discussed here. Treasure County, Montana is labeled. North and east of Treasure County is Rosebud County. North of Rosebud County is Garfield County. Melstone is located in Musselshell County and south of Musselshell County and west of Treasure County is Yellowstone County. The Musselshell River-Yellowstone River drainage divide area discussed here is located primarily in southern Garfield County, northwest Rosebud County, and northeast Treasure County. The Yellowstone River flows northeast and east through Treasure County to Forsyth and then continues east and northeast to Miles City at the figure 2 east edge. The Musselshell River flows east to Melstone and then turns north-northwest and north to flow along the figure 2 west edge to the figure 2 north edge. This essay addresses evidence in the region defined by southeast-oriented Alkali Creek to the west and Big Porcupine Creek to the east (both flowing to the Yellowstone River) and northwest-oriented Calf Creek, northwest, north and west-oriented Rattlesnake Creek, west-oriented Home Creek, and northwest-oriented Lost Horse Creek (not shown on figure 1, but flowing the Musselshell River near Melstone). Figure 2 shows numerous southeast-oriented Yellowstone River tributaries. Also, nearly all Musselshell River tributaries from the east and south are northwest-oriented. This northwest-southeast drainage alignment is evidence the northeast-oriented Yellowstone River valley eroded southwest across an immense southeast-oriented flood to capture flood waters and to divert flood waters northeast. Further, the drainage alignment is evidence the east and north-oriented Musselshell River valley subsequently eroded south and west to capture the same southeast-oriented flood flow and divert the flood waters to the Missouri River valley in the north. The southeast-oriented tributary valleys were eroded by southeast-oriented flood flow moving into the newly eroded and deep Yellowstone and Musselshell 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 would 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.

Calf Creek-McGinnis Creek drainage divide area

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

Figure 3 illustrates the Calf Creek-McGinnis Creek drainage divide area east of Gumbo Ridge. Calf Creek flows northwest to the figure 3 northwest corner area and then to the north-oriented Musselshell River. Note how Calf Creek headwaters are linked by a through valley with south-southeast oriented McGinnis Creek, which flows to figure 3 southeast quadrant and south edge and then to south-and southeast-oriented Big Porcupine Creek, which flows to the Yellowstone River. Also note south-oriented Calf Creek tributaries just west of south-southeast oriented Day Coulee (which drains to McGinnis Creek). The south-oriented Calf Creek tributaries and the through valley to south-oriented McGinnis Creek valley provide evidence the northwest-oriented Calf Creek valley originated as a southeast-oriented flood flow route that was reversed when headward erosion of the north-oriented Musselshell River valley beheaded the southeast-oriented flood flow route. Note how McWilliams Coulee in the figure 3 west center originates as an east-oriented valley and then turns northeast to join northwest-oriented Calf Creek. The McWilliams Coulee valley probably was eroded by yet to be beheaded flood flow southwest of the Calf Creek northwest-southeast alignment that was captured by reversed flood flow on the Calf Creek alignment. East of McWilliams Coulee north-oriented Taylor Coulee provides similar evidence with its southeast-oriented headwaters located south of northwest-southeast oriented Gumbo Ridge. In the figure 3 northeast corner Sand Creek flows northeast to Big Dry Creek, which flows east and north to the Missouri River. West of the Sand Creek headwaters are north-oriented Big Dry Creek headwaters, which after flowing north turn northeast and east to join Sand Creek and then flow north to the Missouri River. Note how the north-oriented Big Dry Creek headwaters are linked by a through valley with the northeast-oriented Sand Creek headwaters. South-oriented flood flow to a south-oriented McGinnis Creek tributary valley was captured by headward erosion of the northeast-oriented Sand Creek valley and then captured  (north of figure 3) by headward erosion of the Big Dry Creek valley, causing a reversal of flood flow to create the present day north-oriented Big Dry Creek headwaters valley.

Big Breed Creek-McGinnis Creek drainage divide area

Figure 4: Big Breed Creek-McGinnis Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates the Big Breed Creek-McGinnis Creek drainage divide south of the figure 3 map area (there is no overlap). Big Breed Creek flows to the figure 4 northwest corner and then to west-oriented Rattlesnake Creek, which flows to the north-northwest oriented Musselshell River. North-oriented Beaverball Creek is the major Big Breed Creek tributary shown. West of Beaverball Creek headwaters are headwaters of northwest-oriented Antelope Creek, which flows to north- and west-oriented Rattlesnake Creek. McGinnis Creek flows south in the figure 4 northeast quadrant and then southeast in the figure 4 east center. In the figure 4 south center are headwaters of West Blacktail Creek. Both McGinnis Creek and West Blacktail Creek flow southeast to join southeast-oriented Big Porcupine Creek, which flows to the Yellowstone River. Note how southeast-oriented West Blacktail Creek headwaters are linked by a through valley with north-oriented Beaverball Creek headwaters and are also on nearly the same northwest-southeast oriented alignment as northwest-oriented Antelope Creek headwaters. Also note how the north-south McGinnis Creek valley segment has numerous southeast-oriented tributaries. This evidence strongly suggests that prior to headward erosion of the deep Musselshell River valley southeast-oriented flood waters flowed across the entire region, probably eroding an ever-changing anastomosing channel complex into the regional surface. Headward erosion of the south-oriented McGinnis Creek valley segment captured southeast-oriented flood flow routes and diverted water into the deeper McGinnis Creek channel. Subsequently headward erosion of the deep Musselshell River valley beheaded southeast-oriented on the Big Breed Creek alignment and caused flood waters on the northwest end of that flood flow route to reverse flow direction and to flow northwest toward the newly eroded Musselshell River valley. The north-oriented Beaverball Creek valley was then eroded at least in part by flood waters captured from the yet to be beheaded southeast-oriented flood flow route on the Antelope Creek-West Blacktail Creek alignment. Headward erosion of the north-oriented Rattlesnake Creek valley (west of figure 4) then beheaded and reversed flood flow on the Antelope Creek alignment and figure 4 drainage patterns have changed little since that time.

McGinnis Creek and Big Porcupine Creek valleys

Figure 5: McGinnis Creek and Big Porcupine Creek valleys. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates where McGinnis Creek joins south and southeast-oriented Big Porcupine Creek and is east of the figure 4 map area and includes overlap areas with figure 4. Big Porcupine Creek is the south oriented stream in the figure 5 east half. McGinnis Creek flows south and then southeast to join Big Porcupine Creek near the figure 5 south edge (east half). North of the McGinnis Creek-Big Porcupine Creek confluence southeast-oriented Short Creek joins south oriented Big Porcupine Creek. Note how headwaters of southeast-oriented Short Creek are linked by a northwest-southeast oriented through valley with a northwest-oriented McGinnis Creek tributary. The northwest-oriented tributary and the through valley provide evidence that southeast-oriented flood flow once moved from the south and southeast-oriented McGinnis Creek valley to the southeast-oriented Short Creek valley at the same time as water was moving south and southeast in the McGinnis Creek valley. Flood flow to the Short Creek valley was beheaded when the McGinnis Creek valley eroded a deeper channel, causing flood waters on the northwest end of the beheaded flood flow route to reverse flow direction and to erode what is today the northwest-oriented McGinnis Creek tributary valley. This divergence and convergence of flood flow channels was typical as southeast-oriented flood waters eroded what was then the north wall of the newly eroded and deep Yellowstone River valley. Flood waters were eroding an ever-changing pattern of anastomosing (or interconnected) channels where as one channel would erode deeper it would capture flood waters moving in adjacent channels. In the process channels were eroded around erosional residuals of higher level erosion surfaces. Note the northwest-southeast oriented erosional residual between McGinnis Creek and Short Creek. Similar erosional residuals can be seen east of Big Porcupine Creek and all along the south and southeast-sloping Yellowstone River north valley wall.

Froze to Death Creek and Big Porcupine Creek valleys

Figure 6 illustrates the Froze to Death Creek and Big Porcupine Creek drainage divide near Ingomar. The figure 6 map area is south and west of the figure 5 map area and there is no overlap. Southeast-oriented Froze to Death Creek is located in the figure 6 southwest corner and flows southeast to the east-oriented Yellowstone River valley. The East Fork of Froze to Death Creek flows south-southeast through Ingomar and south of Ingomar is joined by the southeast-oriented Middle Fork of Froze to Death Creek. Southeast-oriented Sun Coulee extends just northeast of the highway near Ingomar to the figure 6 southeast quadrant and then turns north to drain to southeast-oriented West Blacktail Creek. West Blacktail Creek flows southeast from the figure 6 north edge to join southeast-oriented Big Porcupine Creek in the figure 6 southeast quadrant. Big Porcupine Creek flows southeast from the figure 6 north edge through the northwest quadrant to join West Blacktail Creek and then to the figure 6 east edge. Southwest-oriented East Blacktail Creek flows from the figure 6 northeast corner to join southeast-oriented Big Porcupine Creek in the figure 6 east center. Figure 6 evidence further demonstrates that present day southeast-oriented Yellowstone River tributary valleys were eroded as channels in what was a southeast-oriented anastomosing channel complex. The deep Yellowstone River valley eroded southwest and west to capture an immense southeast-oriented flood and to divert the flood waters to the northeast. The southeast-oriented anastomosing channel complex was eroded into what was then the newly eroded and deep Yellowstone River valley north wall. Figure 6 evidence of the former southeast-oriented anastomosing channel complex is found in through valleys linking present day southeast-oriented Yellowstone River tributary valleys and also in erosional residuals isolated by those through valleys. For example, just north of Ingomar south-oriented East Fork Froze to Death Creek headwaters are linked to southeast-oriented Sun Coulee headwaters and to north-oriented headwaters of southeast-oriented Blind Coulee, which flows to southeast-oriented West Blacktail Creek. Further note the erosional residual isolated by Blind Coulee, West Blacktail Creek and Sun Coulee. Or, in the figure 6 north center note the through valley crossing the ridge between southeast-oriented West Blacktail Creek and southeast-oriented Big Porcupine Creek. That through valley provides evidence flood water once flowed between the two southeast-oriented valleys.

Musselshell River and Calf Creek valleys

Figure 7: Musselshell River and Calf Creek valleys. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 moves to the Musselshell River side of the Musselshell River-Yellowstone River drainage divide and looks at the region where northwest-oriented Calf Creek joins the north-oriented Musselshell River. Figure 3 illustrated the drainage divide area between northwest-oriented Calf Creek and southeast-oriented McGinnis Creek. The Musselshell River flows north along the figure 7 west edge and Calf Creek flows northwest from the figure 7 southeast corner to join the Musselshell River in the figure 7 northwest corner area. The northwest-oriented South Fork of Lodgepole Creek is located in the figure 7 northeast quadrant. Musselshell River tributaries from the east, including Calf Creek and South Fork of Lodgepole Creek, are northwest-oriented. These northwest-oriented Musselshell River tributary valleys were eroded by reversals of flood flow on northwest ends of southeast-oriented flood flow channels beheaded by north-oriented Musselshell River valley headward erosion. The north-oriented Musselshell River valley eroded south across an anatomosing complex of southeast-oriented flood flow channels and because channels were interconnected reversed flood flow in the newly beheaded flood flow channels usually captured southeast-oriented flood flow from yet to be beheaded flood flow routes further to the south and southwest. The northeast-oriented Calf Creek tributary valleys were probably eroded when such captured flood waters moved northeast to join reversed flood flow on what was then the newly beheaded Calf Creek route. For example, look at northwest-oriented Williams Coulee in the figure 7 southwest quadrant and east and north-oriented Wagga Coulee in the figure 7 south center. Yet to be beheaded (by headward erosion of the deep north-oriented Musselshell River valley) southeast-oriented flood flow on the Williams Coulee alignment was captured by reversed flood flow on what was then the newly beheaded Calf Creek alignment. The captured flood flow moved east and north to what is today the northwest-oriented Calf Creek valley. Such captures of yet to be beheaded flood flow enabled reversed flood flow on the Calf Creek alignment to erode a significant northwest-oriented valley. Most Calf Creek tributaries from the north and east are southwest-oriented. At least some of those southwest-oriented tributary valleys and the northeast-oriented South Fork Lodgepole Creek tributary valleys were probably initiated by yet to be beheaded southeast-oriented flood flow on the Calf Creek alignment that was captured by reversed flood flow on what was then the newly reversed South Fork Lodgepole Creek alignment.

Musselshell River and Rattlesnake Creek valleys

Figure 8: Musselshell River and Rattlesnake Creek valleys. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Continuing south along the Musselshell River valley figure 8 illustrates where northwest, north, and west oriented Rattlesnake Creek joins the north oriented Musselshell River. Figure 8 is west of the figure 4 map area and includes overlap areas with figure 4. Big Breed Creek flows northwest and west in the figure 8 northeast quadrant and joins east oriented Rattlesnake Creek in the figure 8 north center. Rattlesnake Creek flows northwest in the figure 8 south center and then flows north to join west oriented Big Breed Creek and flow west in the figure 8 northwest quadrant to join the north-northwest oriented Musselshell River. Previously mentioned (in figure 4) Antelope Creek is the major northwest-oriented Rattlesnake Creek tributary in the figure 8 center. West of the Antelope Creek headwaters is previously mentioned north oriented Beaverball Creek, which flows to Big Breed Creek. Note orientations of tributaries to the various valley segments. For example the east oriented Rattlesnake Creek valley segment in the figure 8 northwest quadrant has numerous northwest-oriented tributaries. While many larger Musselshell River tributaries from the east are not northwest-oriented, almost all of the west and southwest-oriented tributary valleys have northwest-oriented tributaries. The north oriented Rattlesnake Creek valley segment has both southeast and east oriented tributaries from the west and northwest, west, and even southwest-oriented tributaries from the east. The predominant orientation of such secondary tributary valleys however is northwest and southeast. This northwest-southeast tributary orientation is evidence of the southeast-oriented flood flow the larger valleys eroded headward to capture. Most deviations from the northwest-southeast orientation of tributary valleys can be explained by movements of southeast-oriented flood water that were captured by reversed flow on newly beheaded southeast-oriented flood flow routes. For example in the figure 8 southwest quadrant south and southwest-oriented East Keggy Coulee is linked by through valleys to both the north-oriented Rattlesnake Creek valley segment and west-oriented Stensvad Coulee, which drains to the north-oriented Musselshell River. East Keggy Coulee was probably eroded at least in part by yet to be beheaded (by headward erosion of the Musselshell River valley) southeast-oriented flood flow that was captured by reversed flood flow in what is today the north- and west-oriented Rattlesnake Creek valley. Flood flow in the East Keggy Coulee valley was reversed to flow south and southwest when headward erosion of the Musselshell River valley captured the southeast-oriented flood flow route that had been supplying the northeast and east-captured flood flow route that had been supplying flood waters to the north- and west-oriented Rattlesnake Creek valley.

Musselshell River-Alkali Creek-West Muggins Creek drainage divide area

Figure 9: Musselshell River-Alkali Creek-West Muggins Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates  the Musselshell River-Alkali Creek-West Muggins Creek drainage divide area south and southeast of Melstone, Montana and does not overlap with previous figures. The northeast-oriented Musselshell River (which is turning to flow north and north-northwest) is located in the figure 9 northwest quadrant. West oriented Home Creek flows along the figure 9 north edge to the Musselshell River. South of Melstone north-northwest oriented Lost Horse Creek flows to the Musselshell River. Horse Creek flows northwest from the figure 9 center to join the Musselshell River east of Melstone. Southeast-oriented West Muggins Creek flows to the figure 9 southeast corner and then to southeast-oriented Muggins Creek and the east-oriented Yellowstone River. Southeast-oriented drainage routes further to the west flow to southeast-oriented Alkali Creek, which also flows to the east-oriented Yellowstone River. Note how close the heads of the southeast-oriented Yellowstone River tributary valleys are to the deeper Musselshell River valley. Also note the through valleys linking northwest-oriented Musselshell River tributaries with the southeast-oriented Yellowstone River tributaries. For example, in the figure 9 south center note how northwest-oriented Lost Horse Creek headwaters are linked to southeast-oriented Indian Creek headwaters at Indian Springs (located along the figure 9 south edge center). Figure 9 evidence is explained in the context of an immense southeast-oriented flood moving across the figure 9 map area and that was eroding a southeast-oriented anastomosing channel complex into what was then the newly eroded north wall of the deep east-oriented Yellowstone River valley, which had eroded southwest and west to capture the flood waters and divert the flood waters northeast. Subsequently headward erosion of the deep north- and northeast-oriented Musselshell River valley eroded south and southwest to capture the flood flow and by doing so beheaded the southeast-oriented flood flow routes to the Yellowstone River valley. West- and northwest-oriented Musselshell River tributary valleys were eroded by reversed flow on the northwest ends of the beheaded flood flow routes, with the reversed flow routes often capturing southeast-oriented flood flow from yet to be beheaded flood flow routes.

Rattlesnake Creek-Home Creek-Muggins Creek drainage divide area

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

Figure 10 illustrates the Rattlesnake Creek-Home Creek-Muggins Creek drainage divide area east of the figure 9 map area and west of the figure 6 map area and includes overlap areas with both figures 6 and 9. Muggins Creek flows south from Sumatra and later turns southeast to flow to the east-oriented Yellowstone River. The West Fork of Froze to Death Creek flows southeast from Sumatra to southeast-oriented Froze to Death Creek and then to the east-oriented Yellowstone River. Rattlesnake Creek flows northwest from Sumatra and then north and east to the north-oriented Musselshell River. Home Creek flows east from Sumatra to the northeast and north-oriented Musselshell River. Note how these various drainage routes are linked by through valleys in the Sumatra region. To summarize briefly what happened in this figure 10 region, southeast-oriented flood waters to the east-oriented Yellowstone River valley were first concentrated in the southeast-oriented channel now used by the northwest-oriented Rattlesnake Creek valley and the southeast-oriented West Fork Froze to Death Creek valley. Subsequently headward erosion of the deep south and southeast-oriented Muggins Creek valley captured some of the flood flow, although probably flood waters flowed southeast along both the Froze to Death Creek and the Muggins Creek valley routes as well as across much of the intervening drainage divide area. Headward erosion of the deep north-oriented Musselshell River valley then beheaded southeast-oriented flood flow on what is now the northwest-oriented Rattlesnake Creek valley route causing flood waters on the northwest end of the beheaded flood flow route to reverse flow direction and to flow northwest to the newly eroded and locally deeper north-oriented Musselshell River valley. Reversed flood flow on the northwest-oriented Rattlesnake Creek valley route then captured yet to be beheaded (by headward erosion of the north-oriented Musselshell River valley) southeast-oriented flood water being concentrated on an east-oriented Home Creek valley route that was flowing to the south and southeast-oriented Muggins Creek and Froze to Death Creek routes and the captured flood waters turned northeast to flow to the newly created northwest-oriented Rattlesnake Creek valley and the north-oriented Musselshell River valley. Headward erosion of the Musselshell River valley next captured the east-oriented flood flow on the Home Creek valley route and diverted the water north, which in turn caused a reversal of flood flow in the beheaded Home Creek valley to create the present day west-oriented Home Creek valley.

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.