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.

• The purpose of this essay is to use topographic map interpretation methods to explore the Deep Creek-Sixteenmile Creek drainage divide area landform origins in the southern Big Belt Mountains, 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 essay and leaving a link to that essay in a comment here.

• This essay is also exploring a new geomorphology paradigm in which erosional landforms are interpreted as evidence left by immense glacial melt water floods. Implied in that interpretation is the immense floods were derived from a thick North American ice sheet that created a deep “hole” in the North American continent and also melted fast. The previously unexplored paradigm being tested in this and other essays in the Missouri River drainage basin landform origins research project is a thick North American ice sheet, comparable in thickness to the Antarctic ice sheet, occupied the North American region usually recognized to have been glaciated, and through its weight and erosive actions created a deep North American “hole”. The southwestern rim of that deep “hole” is today preserved in the high Rocky Mountains. The ice sheet through its weight and deep erosion (and perhaps deposition along major south-oriented melt water flow routes) caused significant crustal warping and tectonic change, through its action of melting fast produced immense floods that flowed across the continent, and through its action of melting fast systematically opened up space in the ice sheet created “hole” so headward erosion of newly developed north-oriented drainage systems captured immense south-oriented melt water floods and diverted immense melt water floods north into space the ice sheet had once occupied.

• If this previously unexplored paradigm is correct the geographic region explored by this essay should contain evidence of immense floods that were captured by headward erosion of new valley systems so as to cause the floods to flow in a different direction. Ability of this previously unexplored paradigm to explain Deep Creek-Sixteenmile Creek drainage divide area landform evidence in the southern Big Belt Mountains, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm (see essay listed at header). This essay is included in the Missouri River drainage basin landform origins research project essay collection.

Figure 1: Deep Creek-Sixteenmile 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 map of central Montana and provides a location map for the Deep Creek-Sixteenmile Creek drainage divide area in the southern Big Belt Mountains. The Big Belt Mountains are located in the figure 1 west center region and are labeled. Helena is the Montana state capitol and is located west of the Big Belt Mountains. Bozeman is a major town located south of the Big Belt Mountains. The unlabeled mountain range just east of Bozeman and between the Big Belt Mountains and the figure 1 south edge is the Bridger Range. West and north of Bozeman is the town of Three Forks where the north and northwest-oriented Gallatin River, north-oriented Madison River, and north-northeast and east oriented Jefferson River meet to form the north-oriented Missouri River. From Three Forks the Missouri River flows in a north and north-northwest direction (west of the Big Belt Mountains) to Holter Lake (a reservoir) and then turns to flow in a northeast direction to Great Falls and the figure 1 north center edge. The Little Belt Mountains are located east of the Big Belt Mountains and the north-northwest oriented river flowing between the Big Belt Mountains and Little Belt Mountains to join the Missouri River near Great Falls is the Smith River. The Smith River originates just north of the town of Ringling near Elk Peak. Elk Peak is in the Castle Mountains (unlabeled in figure 1). South of the Castle Mountains are the labeled Crazy Mountains. The stream originating on the Crazy Mountains northwest flank and flowing in a west direction to Ringling before turning to flow in a southwest direction to join the Missouri River between Three Forks and Toston is Sixteenmile Creek (unlabeled in figure 1). North of Toston is the town of Townsend and a highway extends in an east direction from Townsend across the Big Belt Mountains south end. For most of the distance across the Big Belt Mountains that highway is located in the Deep Creek valley (Deep Creek is not shown in figure 1). Deep Creek is a west-oriented Missouri River tributary originating on the Big Belt Mountains east side and has eroded a deep valley across the mountains. A southeast and south-oriented Sixteenmile Creek tributary (Battle Creek) drains the area immediately east of the west-oriented Deep Creek through valley. The Deep Creek-Sixteenmile Creek drainage divide area investigated in this essay is located south of Deep Creek, north of Sixteenmile Creek, east of the Missouri River, and west of Battle Creek. The region immediately to the north is described in the South Fork Smith River-Missouri River drainage divide area landform origins in Meagher and Broadwater Counties, Montana essay. Essays illustrating and describing other Missouri River drainage divide areas can be found by selecting appropriate states and/or Missouri River tributaries from the categories list on the sidebar.

• At the time present day figure 1 drainage route developed the entire figure 1 map was being eroded by massive south and southeast-oriented melt water floods from western Alberta and eastern British Columbia, which was where the western rim of a deep “hole” in which a rapidly melting thick North American ice sheet was located. Initially at least present day mountains did not stand high above the surrounding landscape and the immense south and southeast-oriented melt water floods could freely flow across the region. Crustal warping caused by the ice sheet’s tremendous weight was raising mountain ranges and lowering adjacent valleys and basins as flood waters flowed across them. For a time flood water erosion may have kept pace as the rising mountain masses were eroded and the eroded materials probably were deposited in adjacent valleys and basins. In time however the mountain masses began to rise faster than the flood waters could erode them and flood waters eroded deep valleys across the rising mountain masses and/or were channeled between the rising mountain masses. The present day north-northwest oriented Smith River alignment for example was the location of a south-southeast oriented flood flow channel between the Big Belt Mountains and Castle Mountains and then further south between Big Belt Mountains (and the unlabeled Bridger Range south of the Big Belt Mountains) and the Crazy Mountains. Headward erosion of the deep northeast-oriented Missouri River valley (from space being opened up in the deep “hole” by thick ice sheet melting) beheaded the south-southeast oriented flood flow channel. Flood waters on the north-northwest end of the beheaded flood flow channel reversed flow direction to erode the north-northwest oriented Smith River valley. West of the Big Belt Mountains the process was repeated when headward erosion of the deep northeast-oriented Missouri River valley beheaded a south-southeast oriented flood flow channel on the present day north-northwest oriented Missouri River alignment. Flood waters on the north-northwest end of the beheaded flood flow channel reversed flow direction to erode the north-northwest oriented Missouri River valley and also the north-oriented Gallatin, Madison, and Jefferson River valleys and their tributary valleys. The Deep Creek-Sixteenmile Creek drainage divide area investigated in this essay is located between these two former south-southeast oriented flood flow channels, which are now drained by north-northwest oriented rivers.

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

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• Looking more closely at the Deep Creek-Sixteenmile Creek drainage divide area figure 2 provides a detailed location map. County boundaries are shown with Broadwater County being labeled. The county east of Broadwater County is Meagher County. The county in the figure 2 southeast corner is Park County and Gallatin County is west of Park County. Green shaded areas are National Forest lands and are generally located in mountainous regions. Three Forks is the town near the figure 2 south edge near the Gallatin County-Broadwater County line. The Missouri River flows in a north-northeast direction from Three Forks to Lombard and then turns to flow in a north-northwest direction to the figure 2 north edge with the Missouri River valley near the figure 2 north edge being flooded by Canyon Ferry Lake (Reservoir). Townsend is the town at the south end of Canyon Ferry Lake. The Big Belt Mountains are east of Canyon Ferry Lake and extend north of the figure 2 north edge. Deep Creek is a west and west-southwest oriented stream flowing from the east side of the Big Belt Mountains (along the highway east of Townsend) across the Big Belt Mountains to join the north-oriented Missouri River a short distance upstream from Townsend. East of the west-oriented Deep Creek alignment are east and southeast-oriented headwaters of southwest and south-oriented Battle Creek, which flows to southwest and west-oriented Sixteenmile Creek at the town of Sixteen (located in Meagher County southwest corner). Sixteenmile Creek flows across the Big Belt Mountains south end to join the north-oriented Missouri River at the town of Lombard. The Bridger Range is the mountain range south of Sixteenmile Creek and straddles the figure 2 south edge. North of Sixteenmile Creek in Broadwater County is west-oriented Dry Creek and between Dry Creek and Deep Creek is an unnamed west-oriented stream which on more detailed maps is labeled as Greyson Creek.

• Note how many tributaries to the north-oriented Missouri River flow in south directions to join the Missouri River as barbed tributaries. These barbed tributaries are evidence the north-oriented Missouri River valley was once a south-oriented flood flow channel and was beheaded and reversed by headward erosion of the deep northeast-oriented Missouri River valley (north of figure 2) to erode the present day deeper north-oriented Missouri River valley. The Castle Mountains straddle the north edge of the figure 2 northeast quadrant. Note north-oriented drainage routes between the Big Belt Mountains and Castle Mountains flowing to the figure 2 north edge. These north-oriented streams include the north-northwest oriented South Fork Smith River and flow to the north-northwest oriented Smith River. South-oriented streams between the Bridger Range and the Crazy Mountains (south of Sixteenmile Creek headwaters in Meagher County and east of the figure 2 east edge in Park County) include the south-oriented Shields River (flowing through towns of Wilsall and Clyde Park). The Smith River-Shields River flood flow channel was a major south and south-southeast oriented flood flow channel prior to being dismembered by headward erosion of the west-oriented Sixteenmile Creek valley and subsequently by headward erosion of the deep northeast-oriented Missouri River valley (north of figure 2). North-oriented streams north of the Deep Creek headwaters are aligned with the south-oriented Deep Creek headwaters and are located in valleys eroded by reversals of south-oriented flood flow to the Deep Creek valley which occurred when headward erosion of the deep northeast-oriented Missouri River valley beheaded and reversed south-oriented flood flow east of the Big Belt Mountains. The flood flow reversal was probably aided by uplift of the middle section of the south-oriented Smith River-Shields River flood flow channel as massive south-oriented floods were flowing across the figure 2 map region.

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

• Figure 3 illustrates the Deep Creek-Battle Creek drainage divide area on the Big Belt Mountains east flank. Deep Creek flows in a south-southwest and southwest direction across the figure 3 northwest corner. North of the figure 3 map area the south-southwest oriented Deep Creek headwaters valley is linked by a through valley with a northeast-oriented Smith River tributary valley (illustrated and described in the South Fork Smith River-Missouri River drainage divide area landform origins Meagher and Broadwater Counties, Montana essay). The west-oriented Deep Creek tributary flowing just north of the Grass Mountain Ski Area is the Castle Fork Deep Creek. Note how the Castle Fork Deep Creek originates east of the Big Belt Mountains and flows in a west direction to the southwest and west-oriented Deep Creek valley which extends across the Big Belt Mountains. Originating immediately east of the Castle Fork Deep Creek headwaters is Battle Creek, which flows in an east direction to the figure 3 east half and then turns to flow in a south-southeast, southwest and south direction to the figure 3 south edge (just east of center). South of figure 3 Battle Creek joins west-southwest oriented Sixteenmile Creek, which also flows across the Big Belt Mountains to the north-oriented Missouri River. Sixteenmile Creek can be seen flowing in a southwest and west-southwest direction across the figure 3 southeast corner (an abandoned railroad is located in the Sixteenmile Creek valley). East of the figure 3 map area is a broad north-south oriented through valley drained in the north by the north-northwest oriented Smith River, in the south by the south-southeast oriented Shields River, and in the middle by southwest and west oriented Sixteenmile Creek. The southwest oriented Deep Creek and Sixteenmile Creek valleys were eroded across the Big Belt Mountains south end as southwest-oriented flood flow channels diverging from the main south-southeast oriented Smith River-Shields River flood flow channel east of the figure 3 map area and converging with a major south-oriented flood flow channel on the present day Missouri River alignment. At the time the flood flow channels first crossed the region the Big Belt Mountains did not stand high above the adjacent valleys (or lowlands) and flood water could freely flow across what is today a high mountain range. The Big Belt Mountains were uplifted as the flood flow moved across them with the flood flow channels eroding deeper and deeper valley into the rising mountain mass. The Sixteenmile Creek valley was eroded at the south end of the rising Big Belt Mountain mass and was able to erode deeper than the Deep Creek valley to the north. As a result the deeper Sixteenmile Creek valley was able to capture west-oriented flood flow moving to the Deep Creek valley east of the rising Big Belt Mountains front. The east-oriented Battle Creek valley segment was eroded by a reversal of west-oriented flood flow which was beheaded by headward erosion of the deeper southwest- and south-oriented Battle Creek valley segments. Figure 4 below provides a detailed topographic map of Klondike Pass area which links northwest-oriented Sulphur Bar Creek with southeast-oriented Hay Creek (seen in figure 3 southwest quadrant).

Figure 4: Detailed map of Sulphur Bar Creek-Hay Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

• Figure 4 illustrates a detailed topographic map of the Sulphur Bar Creek-Hay Creek drainage divide area at Klondike Pass which was seen in less detail in figure 3 above. Klondike Pass is located near the figure 4 center and is a deep through valley eroded across Grassy Mountain. The figure 4 map contour interval is 40 feet and the Klondike Pass elevation is shown as being 6771 feet. The ridge top in section 17 to the south reaches an elevation of 7227 feet while the ridge in the east half of section 8 to the north rises to 7430 feet meaning the Klondike Pass through valley is at least 450 feet deep. Klondike Pass is a water eroded feature and was eroded by southeast-oriented flood flow moving across the figure 4 map area prior to headward erosion of the west-southwest oriented Deep Creek valley to the northwest (not seen in figure 4). The southeast-oriented stream originating at Klondike Pass flows to south-southeast and southeast oriented Hay Creek, which flows to the figure 4 southeast corner. South and east of figure 4 Hay Creek flows to Battle Creek, which then flows to west-southwest oriented Sixteenmile Creek (which is located south of the figure 4 map area). The northwest-oriented stream originating at Klondike Pass is a tributary to northwest-oriented Sulphur Bar Creek, which north and west of figure 4 flows to west-oriented Deep Creek. The northwest-southeast orientation of these valleys and the Klondike Pass through valley provide evidence of a southeast-oriented flood flow channel that was beheaded and reversed by headward erosion of the much deeper west- and southwest-oriented Deep Creek valley. The existence of this southeast-oriented flood flow channel suggests that prior to headward erosion of the deep west-oriented Deep Creek and Sixteenmile Creek valleys the region was crossed by southeast-oriented flood flow. The northwest-oriented stream in the figure 4 southwest corner is Greyson Creek. Greyson Creek originates in section 20 on the west side of another and deeper through valley or pass across the Grassy Mountain south end. An east-northeast oriented Hay Creek tributary originates on the east side of the through valley, although between the through valley and that east-northeast oriented Hay Creek tributary are south-oriented headwaters of Sherlock Creek, which flow to Sixteenmile Creek (south of figure 4). West of figure 4 Greyson Creek turns to flow in a west direction to the north-oriented Missouri River. Figures 5 and 6 below better illustrate the Sherlock Creek and Hay Creek relationships with Sixteenmile Creek and with hogback ridges along the Big Belt Mountains south flank.

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

• Figure 5 illustrates the Dry Creek-Sixteenmile Creek drainage divide area south and west of figure 3 and includes overlap areas with figure 3. Sixteenmile Creek flows in a southwest direction from the figure 5 east edge to the Meagher-Broadwater-Gallatin County corner and then flows in a south-southwest direction to the figure 5 south center edge. Battle Creek is the south-oriented tributary joining Sixteenmile Creek in the figure 5 northeast quadrant. Hay Creek is the southeast-oriented Hay Creek tributary flowing from the figure 5 north center edge and Horse Creek is a northeast-oriented Hay Creek tributary. Greyson Creek headwaters can be seen flowing in a northwest direction near the figure 5 north edge (west of Hay Creek in the figure 5 northwest quadrant). The north and west-northwest oriented stream south of the word “MOUNTAINS” and flowing to the figure 5 west edge (north half) is Dry Creek. Note how three south-southeast oriented Sixteenmile Creek tributaries have eroded deep valleys across the arcuate hogback ridge between Dry Creek and Sixteenmile Creek. The westernmost tributary is Haw Gulch, which has eroded its valley along the strike of the dipping beds and which has avoided cutting a deep valley across the hogback ridge. The center tributary is Paddys Run, which has eroded a deep water gap across the hogback ridge and which drains in a south-southeast direction to join Sixteenmile Creek south of the figure 6 south center edge. Note how the south-southeast oriented Paddys Run valley is linked by a through valley with the north-oriented Dry Creek headwaters valley. Further east and north is southeast-oriented Spring Gulch (or Sherlock Creek) which joins Sixteenmile Creek near the Meagher-Broadwater-Gallatin County corner. Spring Gulch (Sherlock Creek in figure 6 which is a more detailed topographic map) has eroded a deep water gap across the hogback ridge. Note how the southeast-oriented Spring Gulch (or Sherlock Creek) valley is linked by through valleys with the west-northwest oriented Dry Creek valley and also with the northeast-oriented Horse Creek valley. The multiple deep south-southeast oriented valleys eroded into the arcuate hogback at the Big Belt Mountains south end suggests multiple south-southeast oriented flood flow channels flowed across the region as the Big Belt Mountains were being uplifted. These were probably diverging and converging flood flow channels such as might be found in an anastomosing channel complex and were probably constantly changing as deeper channels were able to erode headward along zones of bedrock weakness. Eventually uplift of the Big Belt Mountains combined with headward erosion of a deeper Missouri River valley (west of figure 5) resulted in dismemberment of the southeast-oriented flood flow channels which created the drainage divides seen in figure 5. The present day north and west-northwest oriented Dry Creek valley was eroded by a reversal of flood flow on the west and north ends of what had been an east and south-oriented flood flow channel.

Figure 6: Detailed map of Sherlock Creek water gap  area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

• Figure 6 provides a detailed topographic map of the Sherlock Creek (Spring Gulch on figure 5) water gap area seen in less detail in figure 5 above. Sixteenmile Creek flows in a southwest and south direction from the figure 6 east edge (north of center) to the figure 6 south edge (east of center). Sherlock Creek flows in a southeast direction from the figure 6 northwest corner to join Sixteenmile Creek at the Broadwater-Meagher County border (where Sixteenmile Creek changes from flowing in a southwest to south direction). Note how Sherlock Creek has eroded a deep water gap across the high ridge defined by Sherlock Mountain (in section 15) and Wall Mountain (in section 4). The figure 6 contour interval is 40 feet and Sherlock Creek flows across the 5600, 5400, and 5200 foot contour lines as its flows through the water gap. Wall Mountain to the north rises to 6868 feet while Sherlock Mountain to the south rises to 6620 feet which means the water gap is from 1000 to 1400 feet deep. Sixteenmile Creek has also eroded a 1000-foot deep valley through the region (note spot elevation of 6189 feet in section 18 just north of figure 6 southeast corner). The southwest and south-oriented Sixteenmile Creek valley was probably eroded as a southwest and south-oriented flood flow channel and the southeast-oriented Sherlock Creek valley was a converging southeast-oriented flood flow channel while the Big Belt Mountains were being uplifted. The south-oriented flood flow was moving eventually to south-oriented flood flow channels moving flood waters to and across the present day Yellowstone National Park region where headward erosion of deep valleys from both the east and the west was carving the east-west continental divide. Big Belt Mountain uplift combined with headward erosion of the deep northeast-oriented Missouri River valley (north of this essay’s study region) in time resulted in massive flood flow reversals that ended southeast-oriented flood flow to the Sixteenmile Creek valley and southeast-oriented flood flow through the Sherlock Creek water gap also was ended. Since that time only local drainage has flowed through the deep Sixteenmile Creek canyon and Sherlock Creek water gap.

Figure 7: Deep Creek-Dry Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

• Figure 7 illustrates the Deep Creek-Dry Creek drainage divide area west and slightly north of the figure 5 map area and includes an overlap area with figure 5. The Missouri River flows in a north-northwest direction across the figure 7 southwest corner and the Canyon Ferry Lake (Reservoir) south end, which floods the Missouri River valley, can be seen in the figure 7 northwest corner. Dry Creek flows in a west-northwest and then west-southwest direction from the figure 7 southeast corner to join the north-oriented Missouri River just south of the town of Holker near the figure 7 southwest corner. The next west-oriented stream north of Dry Creek is Greyson Creek, which flows from the figure 7 east edge (south half) to join the Missouri River a short distance north of Holker. North of Greyson Creek is west-northwest, west, and southwest oriented Deep Creek, which flows from the figure 7 east edge (north of center) to the figure 7 west edge (south of center) and then joins the Missouri River just west of figure 7. Note how Deep Creek and to a lesser extent Dry Creek flow to the Missouri River as a barbed tributaries suggesting the Missouri River valley may have once been a south-oriented drainage route with flow subsequently being reversed to move in a north direction. Missouri River tributary orientations are much better seen on larger region maps such as figure 2 where many south-oriented tributaries from both sides of the Missouri River valley flow to the Missouri River as barbed tributaries. Study of the drainage divides between the west-oriented Missouri River tributaries in figure 7 reveals a number of north-south oriented through valleys. The most obvious through valleys can be seen along the Deep Creek-Greyson Creek drainage divide east of the a north-south oriented hogback ridge (just east of the figure 7 center). Note several north-oriented Deep Creek tributaries and how those tributaries are linked by through valleys with the Greyson Creek valley to the south. Figure 8 below provides a detailed topographic map of the Deep Creek-Greyson Creek drainage divide area in that region to better illustrate the through valleys. The through valleys were eroded as south-oriented flood flow channels to what was then probably a newly eroded Greyson Creek valley prior to headward erosion of the deeper west-oriented Deep Creek valley. The north-oriented Deep Creek tributary valleys were eroded when flood waters on north ends of the beheaded flood flow channels reversed flow direction to erode north-oriented tributary valleys.

Figure 8: Detailed map of Deep Creek-Greyson Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

• Figure 8 provides a detailed topographic map of the Deep Creek-Greyson Creek drainage divide area seen in less detail in figure 7 above. Deep Creek flows in a west direction along the north margin of the figure 8 northwest quadrant. Greyson Creek flows in a generally west direction near the figure 8 south edge. Note how there are several north and northwest oriented Deep Creek tributaries and how those tributaries are linked by through valleys with the Greyson Creek valley. For example in the figure 8 southwest quadrant a north-south oriented through valley in the southwest corner of section 2 and northwest corner of section 11 links a north-oriented Deep Creek tributary valley with a south-oriented Greyson Creek tributary valley. The figure 8 map contour interval is 40 feet and the through valley floor elevation is between 5040 and 5080 feet. The spot elevation on the high ridge in the figure 8 southwest corner reads 5646 feet and much higher elevations can be found along the south half of the figure 8 east edge. In other words the through valley is approximately 600 feet deep. This 600-foot deep valley is a water eroded feature and was eroded by south-oriented flood water moving to what was then the actively eroding Greyson River valley. Additional through valleys can be seen by proceeding further east along the drainage divide. For example Ross Gulch is a northwest-oriented Deep Creek tributary located in sections 5, 32, and 31. Near the northeast corner of section 8 is a through valley linking the Roos Gulch headwaters with a southwest-oriented Greyson Creek tributary. The through valley floor elevation is between 5600 and 5640 feet while the hill immediately to the west rises to more than 5760 feet indicating the through valley is at least 120 feet deep. Again this through valley provides evidence of south-oriented flood flow prior to headward erosion of the Deep Creek valley. Headward erosion of the Deep Creek valley beheaded the southeast and southeast-oriented flood flow channel supplying flood waters to the actively eroding Greyson Creek valley. Note how the adjacent hill (to the west) does not rise as high as the ridge in the figure 8 southwest corner or as high as the previously cited elevation along the figure 8 west edge. The two through valleys mentioned as examples (and other through valleys not mentioned) between those high points could just be channels eroded into the floor of what was once a much broader and deeper south-oriented flood flow channel that was captured by Greyson Creek valley headward erosion.

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

• Figure 9 illustrates the Dry Creek-Sixteenmile Creek drainage divide area south of the figure 7 map area and includes overlap areas with figure 7. The Missouri River meanders in a north-northwest direction near the figure 9 southwest corner. Toston is the small town on the Missouri River east bank a short distance south of the figure 9 west center edge area. Maudlow in the small town located near the figure 9 southeast corner. Sixteenmile Creek is flowing in a west, northwest, and west-southwest direction from Maudlow to join the Missouri River just south of the figure 9 map area (near southwest corner). Haw Creek is the south and south-southeast oriented tributary joining Sixteenmile Creek near the figure 9 southeast corner. Note other south-oriented tributaries flowing to Sixteenmile Creek. Sixmile Creek is the west-southwest and west oriented Missouri River tributary originating north of Sixmile Mountain and located north of Sixteenmile Creek. Dry Hollow is the northwest, west-southwest, and west oriented stream north of Sixmile Creek. Dry Creek flows in a west-northwest direction near the figure 9 northeast corner and then is seen flowing in a west-southwest direction near the figure 9 northwest corner. Again note north-south oriented through valleys crossing the west-east oriented drainage divides. The figure 9 map contour interval is 50 meters and many smaller landform features are lost, although a number of north-south oriented through valleys can be seen. Probably the most obvious through valleys can be seen crossing the Sixmile Creek-Sixteenmile Creek drainage divide, which is shown using a more detailed topographic map in figure 10. The through valleys were eroded by south-oriented flood flow which was captured in sequence by headward erosion of the west-oriented Sixteenmile Creek valley first, headward erosion of the west-oriented Sixmile Creek valley second, headward erosion of the west-oriented Dry Hollow valley third, and next by headward erosion of the Dry Creek valley. Headward erosion of these west-oriented valleys was across south-oriented flood flow, which means at that time the present day north-oriented Missouri River valley was being eroded by south-oriented flood flow. Subsequently, due to crustal warping and headward erosion of the deep northeast-oriented Missouri River valley north of the figure 9 map area, the south-oriented flood flow across the figure 9 map area (and in the Missouri River valley) was beheaded and flood waters on the north end of the beheaded flood flow channel(s) reversed flow direction to erode a much deeper north-oriented Missouri River valley, which among other things eroded deep incised meanders into the underlying bedrock (as seen near the figure 9 southwest corner).

Figure 10: Detailed map of Sixmile Creek-Sixteenmile Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

• Figure 10 provides a detailed topographic map of the Sixmile Creek-Sixteenmile Creek drainage divide area seen in less detail in figure 9 above. The Missouri River flows in a northwest direction in the figure 10 southwest corner. Sixteenmile Creek can be seen flowing in a west direction near the figure 10 southeast corner. Sixmile Creek can be seen near the figure 10 north center edge and is also flowing in a west direction. Several well-defined north-south oriented through valleys link the Sixmile Creek valley and the Sixteenmile Creek valley. Starting in the west is a through valley seen in section 20 linking a north-oriented Sixmile Creek tributary valley with a south-southwest oriented Sixteenmile Creek tributary valley. Another through valley can be seen in section 28 linking a north-oriented Sixmile Creek tributary valley with a south-southwest oriented Sixteenmile Creek tributary valley. Just to the east in the section 27 northwest corner and section 22 southwest corner is another through valley this time oriented in a south-southeast direction. And in the section 22 northeast corner a through valley links a west-oriented Sixmile Creek tributary valley with a south-southeast oriented Sixteenmile Creek tributary valley. Study of the figure 10 map area reveals additional through valleys. While the through valleys are undoubtably eroded along zones of bedrock weakness they are also water eroded features and were eroded by south-oriented flood flow channels eroding headward from what was at that time the newly eroded west-oriented Sixteenmile Creek valley. At that time the west-oriented Sixmile Creek valley did not exist and flood waters could freely flow in a south direction from north of figure 10 to the newly eroded Sixteenmile Creek valley. Headward erosion of the west-oriented Sixmile Creek then beheaded the south-oriented flood flow channels in sequence from west to east. Flood waters on north and west ends of the beheaded flood flow channels reversed flow direction to erode the north-oriented Sixmile Creek tributary valleys. Because the flood flow channels were beheaded in sequence from west to east reversed flood flow in a newly beheaded and reversed flood flow channel could capture south-oriented flood waters from yet to be flood flow channels further to the east. Such captures of yet to be beheaded flood flow provided water volumes required to erode the north-oriented Sixmile Creek tributary valleys.

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.