Des Moines River-Grand River drainage divide area landform origins in Adair, Madison, Union, and Ringgold Counties, Iowa, USA

Authors

Abstract:

This essay uses topographic map evidence to interpret landform origins in the Des Moines River-Grand River drainage divide area located in Adair, Madison, Union, and Ringgold Counties, Iowa. The major drainage divide observed in the four county study region is the Middle River-Thompson River drainage divide, where the Middle River is a southeast and east-northeast oriented Des Moines River tributary and the Thompson River is a southeast and south oriented Grand River tributary. Also observed in the study region are the Middle River-Nodaway River drainage divide, Nodaway River-Platte River drainage divide, Thompson River-Platte River drainage divide, and the Thompson River Grand River drainage divide. The Nodaway River, Platte River, and Grand River are separate south oriented Missouri River tributaries and flow to the Missouri River at quite different locations while the Des Moines is a southeast-oriented Mississippi River tributary. Valley orientations, elbows of capture, barbed tributaries, and shallow through valleys crossing drainage divides provide evidence present day river valleys and their tributary valleys eroded headward into the study region to capture an immense south and/or southeast oriented flood. Flood waters are interpreted to have been derived from a rapidly melting North American ice sheet located north of the study region. Initially the south and southeast oriented flood waters were captured by the Missouri River valley, which was eroding headward across the state of Missouri. South and southeast oriented tributary valleys then eroded headward from the newly eroded Missouri River valley in sequence with the Grand River-Thompson River and tributary valleys eroding headward first, the Platte River valley eroding headward second, and the Nodaway River valley and tributary valleys eroding headward last. Headward erosion of the Des Moines River valley and its tributary Middle River valley next beheaded flood flow routes to actively eroding Thompson River and Nodaway River headwaters and tributary valleys.

Preface:

The following interpretation of detailed topographic map evidence is one of a series of essays describing similar evidence for all major drainage divides contained within the Missouri River drainage basin and for all major drainage divides with adjacent drainage basins. The research project is interpreting evidence in the context of a previously unexplored deep glacial erosion paradigm, which is fundamentally different from most commonly accepted North American glacial history interpretations. Project essays available at this site may be found by selecting desired Missouri River tributaries and/or states from this essay’s sidebar category list.

Introduction:

  • The purpose of this essay is to use topographic map interpretation methods to explore the Des Moines River-Grand River drainage divide area landform origins in Adair, Madison, Union, and Ringgold Counties, Iowa, USA. Map interpretation methods can be used to unravel many geomorphic events leading up to formation of present-day drainage routes and development of other landform features. While each detailed topographic map feature provides detailed evidence to be explained, the solution must be consistent with explanations for adjacent area map evidence as well as solutions to big picture map evidence puzzles. I invite readers to improve upon my solutions and/or to propose alternate solutions that better explain evidence and are also consistent with adjacent map area and big picture evidence. Readers may do so either by making comments here or by writing and publishing their own essays and then by leaving a link to those essays 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 Des Moines River-Grand River drainage divide area landform evidence in Adair, Madison, Union, and Ringgold Counties, Iowa will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm (see menu at top of page for paradigm related essay). This essay is included in the Missouri River drainage basin landform origins research project essay collection.

Des Moines River-Grand River drainage divide area location map

Figure 1: Des Moines River-Grand 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 location map for the Des Moines River-Grand River drainage divide area in Adair, Madison, Union, and Ringgold Counties, Iowa. The Mississippi River flows in a south-southwest direction from the figure 1 northeast corner to the east center and then turns to flow in a south-southeast direction to the southeast corner. South of figure 1 the Mississippi River eventually flows to the Gulf of Mexico. The state east of the Mississippi River in figure 1 is Illinois. West of the Mississippi River in the figure 1 north half is Iowa and in the south half is Missouri. The Missouri River flows in a south-southeast direction from near the figure 1 northwest corner to Kansas City and then turns to flow in an east-northeast direction to Brunswick, Missouri. At Brunswick the Missouri River turns to flow in a southeast direction to the figure 1 south edge. South of the figure 1 map area the Missouri River turns again to flow in an east direction to join the south-oriented Mississippi River. The state west of the Missouri River in the figure 1 north half is Nebraska and the state in the southwest corner is Kansas. The Des Moines River flows in a south-southeast direction from the figure 1 north edge to Des Moines, Iowa and then flows in a southeast direction to join the Mississippi River at the Iowa-Missouri state border. Note southeast-oriented Des Moines River tributaries, some of which flow in a southeast and then northeast direction just south of Des Moines, Iowa. The Grand River originates near Afton, Iowa (south and west from Des Moines) and flows in a south and southeast direction to join the Missouri River near Brunswick, Missouri. A major Grand River tributary is the Thompson River, which originates near Greenfield (north of Afton and west and south from Des Moines) and which flows in a south-southeast and south direction to join the southeast-oriented Grand River near Utica, Missouri. West of the Grand River in Iowa and south of the Thompson River headwaters are headwaters of the south and south-southwest oriented Platte River and west of the Platte River drainage basin is the south-oriented Nodaway River drainage basin, with the East Nodaway River headwaters being located in the same region (near Greenfield) as the Thompson River headwaters. North of the south-oriented Nodaway, Platte, Grand, and Thompson River headwaters is the southeast-oriented Middle River, which turns to flow in an east-northeast direction to join the southeast-oriented Des Moines River. The Des Moines River-Grand River drainage divide area of concern in this essay includes the East Nodaway River, Platte River, Grand River, and Thompson River headwaters areas and drainage divides between their headwaters streams and also with the Middle River. Note how the drainage divide with the Middle River is not only the Des Moines River (or Middle River) River-Grand River drainage divide, but also the Mississippi River-Missouri River drainage divide.
  • The Des Moines River (or Middle River)-Grand River drainage divide was created during an immense south-oriented flood as the deep Des Moines River valley and the Missouri River and their tributary valleys eroded headward from what was then an actively eroding Mississippi River valley. Flood waters were derived from a rapidly melting North American ice sheet north of the figure 1 map area. The ice sheet had been large and had been located in a deep “hole” created by deep glacial erosion and crustal warping caused by the ice sheet’s tremendous weight. The figure 1 map area was located along the deep “hole’s” southern rim and was deeply eroded by gigantic south-oriented melt water floods prior to the formation of present day drainage networks. How much flood water erosion occurred may never be determined nor may the ice sheet’s most southern margin ever be accurately delineated. What can be determined is all major drainage networks between the figure 1 map area and the Gulf of Mexico were eroded in sequence (from south to north) as deep east and southeast oriented tributary valleys (and tributary valleys to those tributary valleys) eroded headward from the Mississippi River valley. The Mississippi River valley was actively eroded as actively developing tributary valley systems (from both the west and the east) captured the south-oriented melt water floods and diverted the flood flow to the Mississippi River valley. In the figure 1 map area the Missouri River valley eroded headward from the Mississippi River valley first and south-oriented tributary valley systems including the Gand River valley and its tributary Thompson River valley and the Platte River and Nodaway River valleys eroded headward from the actively eroding Missouri River valley in that order. Following soon after the Des Moines River valley and its tributary valleys eroded headward from the actively eroding Mississippi River valley and began to capture south-oriented flood flow to the actively eroding south-oriented Missouri River tributary valleys. Headward erosion of the southeast and east-northeast oriented Middle River valley beheaded south-oriented flood flow routes to the actively eroding Thompson (and Grand) River, Platte River, and East Nodaway River valleys before headward erosion of other Des Moines River tributary valleys beheaded all south-oriented flood flow routes to the actively eroding Middle River valley.

Detailed Des Moines River-Grand River drainage divide area location map

Figure 2: Detailed Des Moines River-Grand River drainage divide area location map. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 2 provides a more detailed location map for the Des Moines River-Grand River drainage divide area in Adair, Madison, Union, and Ringgold Counties, Iowa. County names and boundaries are shown and the west to east oriented Iowa-Missouri state line is located just north of the figure 2 south edge. The southeast-oriented Middle River flows through Howe and Arbor Hill in the Adair County northeast quadrant to Webster on the Adair-Madison County line. Once in Madison County the Middle River turns to flow in an east-northeast direction to join the southeast-oriented Des Moines River in the Warren County northeast corner. The Thompson River originates in Adair County in the region east of Greenfield and flows in a southeast and south-southeast direction across the Madison County southwest corner and eastern Union County to the Union County southeast corner and then across western Decatur County to the Missouri state line. Major Thompson River tributaries in Union County include southeast-oriented Threemile Creek and Twelvemile Creek. The East Fork Grand River originates south of Arispe in south central Union County and flows in a southeast direction to the Union-Ringgold County line and then flows in a south and south-southwest direction to the Ringgold County south center border. The Grand River originates south and west of Afton in Union County and flows in a south, southwest, south, and southwest direction to the Ringgold County southwest corner. South of the figure 2 map area the Grand River turns to flow in a southeast direction and is eventually joined by the south-oriented Thompson River. All streams in Ringgold and Decatur Counties are included in the Grand River drainage basin. The Platte River originates at Green Valley Lake in northwest Union County and flows in a south-southwest and south-southeast to the Ringgold County northwest corner. Once in Ringgold County the Platte River flows in a south and southwest direction adjacent to and parallel with the Grand River to the Taylor County southeast corner. Once in Missouri the Platte River continues to flow in south-southwest and south direction while the Grand River turns to flow in a southeast direction. The East Nodaway River originates at the junction of two tributaries in northeast Adams County and flows in a southwest direction to the Adams County southwest corner and then turns to flow in a south and south-southwest direction to the figure 2 west edge. South-oriented drainage routes in western Adair County are Middle Nodaway river headwaters and tributaries, with the Middle Nodaway River flowing to the Adair County southwest corner before flowing in a southwest direction to the Adams County west center border. West of the figure 2 map area the Middle Nodaway River joins the south-oriented West Nodaway River and subsequently the East Nodaway River to form the south-oriented Nodaway River (see figure 1).

South Fork Middle River-Middle Nodaway River drainage divide area

Figure 3: South Fork Middle River-Middle Nodaway River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 3 uses a reduced size topographic map to illustrate the South Fork Middle River-Middle Nodaway River drainage divide area. Adair is the town located in the figure 3 northwest corner. Casey is the town located near the figure 3 north center edge. The southeast-oriented river flowing from the figure 3 north edge near Casey to the east edge (south half) is the Middle River. The South Fork Middle River flows in a northwest, north, east-southeast, and northeast direction to join the Middle River near Casey. Note how several tributaries to the northwest-oriented South Fork segment are oriented in southeast directions. The south-southeast oriented drainage system flowing to the figure 3 south center edge is the headwaters of the Middle Nodaway River. The northwest-oriented South Fork Middle River valley was eroded by a reversal of a south-southeast oriented flood flow route to what was then the actively eroding Middle Nodaway River valley. The reversal of flood flow occurred when headward erosion of the deep southeast-oriented Middle River valley and its east-southeast oriented South Fork valley captured the south-southeast oriented flood flow route. Flood waters on the northwest end of the beheaded flood flow route reversed flow direction to erode the northwest-oriented South Fork valley segment and in the process captured southeast-oriented flood flow routes still moving water towards the former south-southeast oriented flood flow channel. The deeper Middle River valley knick point was then able to erode headward along those captured southeast-oriented flood flow routes to erode the deep southeast-oriented tributary valleys to the northwest-oriented South Fork valley segment. East of the South Fork-Middle Nodaway River drainage divide is southeast-oriented North Turkey Creek, which joins southeast, north-northeast, north, and northeast oriented South Turkey Creek to flow in a northeast direction to join the southeast-oriented Middle River as a barbed tributary. Note how north-oriented South Turkey Creek has southeast-oriented headwaters and tributaries and also has north-oriented valley segments and tributaries. While exhibiting a somewhat more complex drainage history than the South Fork-Middle Nodaway River drainage divide the Turkey Creek valley erosion also reflects the capture of south-oriented flood flow routes, with the north-oriented tributary valleys and valley segments being eroded by reversals of flood flow on north ends of beheaded south- and southeast-oriented flood flow routes. Close study of the figure 3 map reveals shallow through valleys crossing drainage divides. These through valleys, which are better seen on more detailed topographic maps, provide further evidence of former flood flow channels.

Bruce Branch-Thompson River drainage divide area

Figure 4: Bruce Branch-Thompson River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 4 illustrates the Bruce Branch-Thompson River drainage divide area located south and east of the figure 3 map area and includes overlap areas with figure 3. The Middle River flows in a southeast direction across the figure 4 northeast quadrant. Bruce Branch is an east-northeast oriented Middle River tributary located near the figure 4 north edge. The southeast and northeast oriented stream west of Meadow Lake (near figure 4 north edge) is South Turkey Creek, which was seen in figure 3. The Thompson River originates as an east-oriented stream just south of the Bruce Branch headwaters and then turns to flow in a southeast direction to the figure 4 south edge (near southeast corner). Study of the Bruce Branch-Thompson River drainage divide (seen in more detail in figure 5 below) reveals the presence of several shallow through valleys. The through valleys provide evidence of south-oriented flood flow routes to the southeast-oriented Thompson River valley, which were beheaded by headward erosion of the east-northeast oriented Bruce Branch valley. North of the Bruce Branch valley where the words “Meadow Lake State Wildlife Management Area” are written additional shallow through valleys can be seen linking north-oriented South Turkey Creek tributary valleys with the Bruce Branch valley (and with the Thompson River valley further to the south). In other words, the southeast-oriented North Turkey Creek alignment seen in figure 3 was used by a southeast-oriented flood flow route moving flood waters to what was then the actively eroding Thompson River valley (which was eroding headward from the newly eroded Grand and Missouri River valleys). Headward erosion of the deep east-northeast oriented Bruce Branch valley captured the flood flow and diverted the flood waters to what was then the newly eroded Middle River valley (eroding headward from the newly eroded Des Moines River and Mississippi River valleys). The south-southeast and southwest oriented stream west of Greenfield in the figure 4 west half is the Middle Nodaway River. Note how the Middle Nodaway River has northwest-oriented tributaries (especially in the figure 4 southwest quadrant) and also the pattern of Middle Nodaway tributaries south of the South Turkey Creek elbow of capture. Originally south-oriented flood flow also moved to the Middle Nodaway River drainage basin in a south-southwest direction along the present day north-northeast oriented South Turkey Creek alignment (seen in figure 3). Headward erosion of the deep Middle River valley and its northeast-oriented Turkey Creek tributary valley captured the flood flow route and flood waters on the north end of the beheaded flood flow route reversed flow direction to erode the north-northeast and north oriented South Turkey Creek valley and to capture the southeast-oriented South Turkey Creek headwaters.

Detailed map of Bruce Branch-Thompson River drainage divide area

Figure 5: Detailed map of Bruce Branch-Thompson River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 5 provides a detailed topographic map of the Bruce Branch-Thompson River drainage divide area seen in less detail in figure 4 above. Bruce Branch flows in a northeast direction from section 21 across the section 22 northwest corner and the section 15 southeast corner before turning to flow in an east-southeast and east-northeast direction to the figure 5 north edge (east half) and then to the southeast oriented Middle River (north and east of figure 5). Note the numerous north-oriented Bruce Branch tributary valleys. The north-northeast oriented stream flowing from section 24 to the figure 5 northeast corner area is a barbed Middle River tributary independent of Bruce Branch. The Thompson River originates in the north half of section 28 and flows in an east direction to the section 27 northeast corner before turning to flow in a southeast and south direction to the section 26 southeast corner and the section 25 south center where it turns to flow in southeast direction to the figure 5 southeast corner. Note how the Thompson River valley has several southeast oriented tributary valleys. The Bruce Branch-Thompson River drainage divide appears to be a relic of what was once a gently sloping erosion (or deposition) surface, but also is marked by shallow northwest-southeast oriented through valleys linking north-oriented Bruce Branch tributary valleys with southeast oriented Thompson River tributary valleys. One of the deeper through valleys is located in section 22. The map contour interval is 20 feet and the through valley floor elevation is between 1300 and 1320 feet. Elevations on either side of the through valley rise to more than 1340 feet. While not deep the through valley provides evidence of a south-oriented flood flow channel that prior to headward erosion of the Bruce Branch valley moved flood waters to what was then the actively eroding Thompson River valley. Other through valleys are shallower and are defined by single contour lines on each side, although they also provide evidence of south-oriented flood flow routes. The multiple flood flow routes and the shallow through valleys suggests south-oriented flood water flowed across the entire Bruce Branch-Thompson River drainage divide to what were then actively eroding southeast and south-oriented Thompson River tributary valleys. Headward erosion of the deep Bruce Branch valley beheaded the flood flow routes in sequence from east to west. Flood waters on north ends of beheaded flood flow routes reversed flow direction to erode the north-oriented Bruce Branch tributary valleys.

Bush Branch-Thompson River drainage divide area

Figure 6: Bush Branch-Thompson River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 6 uses a reduced size topographic map to illustrate the Bush Branch-Thompson River drainage divide area located east and somewhat south of the figure 4 map area and includes overlap areas with figure 4. The Thompson River flows in a southeast direction from the figure 6 northwest corner to the figure 6 south center edge. Macksburg is the small town located near where the Thompson River reaches the south edge. The Middle River meanders in an east-southeast direction near the figure 5 north center edge and then across the northeast quadrant to the east edge (north half). Bush Branch is the southeast, northeast, southeast, and north oriented Middle River tributary flowing across the figure 6 north center area just south of the Middle River. Note how the Bush Branch has south and southeast oriented tributaries from the north and northeast, north-northeast, and northwest oriented tributaries from the south. Further note how south of the elbow of capture (where Bush Branch changes from flowing in a southeast direction to flowing in a northeast direction) there is a significant north-oriented tributary valley which is linked by shallow through valleys to south-oriented Thompson River tributary valleys. The southeast-northeast oriented Bush Branch elbow of capture originated where a southeast-oriented flood flow route converged with a southwest-oriented flood flow route to create a south-oriented flood flow route which then split into several diverging channels. Such convergence and divergence of flood flow channels is typical of large-scale anastomosing channel complexes. The diverging south-oriented flood flow channels were captured by headward erosion of the deep southeast-oriented Thompson River valley and the south-southeast and southwest oriented tributary valleys then eroded headward along the diverging flood flow channels. Next headward erosion of the deep Bush Branch valley from the actively eroding Middle River valley beheaded the southwest-oriented flood flow south of Webster (Middle River P.O.). Flood waters on the northeast end of the beheaded flood flow route reversed flow direction to erode the northeast-oriented Bush Branch valley and to capture what is today the southeast-oriented Bush Branch valley segment. The reversal of flood flow also eroded the north-oriented Bush Branch tributary valley. Rocky Branch is the north-northeast oriented Wells Creek tributary originating near Macksburg and flowing to a similar southeast-northeast oriented Wells Creek elbow of capture. The figure 6 valley orientations, elbows of capture, barbed tributaries, and through valleys provide evidence of many other examples of captures of south-oriented flood flow channels by headward erosion of the figure 6 deep valleys.

Detailed map of Bush Branch-Thompson River drainage divide area

Figure 7: Detailed map of Bush Branch-Thompson River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 7 provides a more detailed topographic map of the Bush Branch-Thompson River drainage divide area seen in less detail in the figure 6 map area above. The Thompson River flows in a south, southeast, south, and southeast direction from the figure 7 northwest corner to the south center edge. Note short north-northeast oriented Thompson River tributaries from the south and how those tributary valleys are linked by shallow trough valleys with south-oriented tributary valleys to an unnamed southeast-oriented stream in the figure 7 southwest quadrant. Examples of the through valleys can be seen in section 17 southeast corner and section 21 center. The tributary orientations and the through valleys provide evidence headward erosion of the deep unnamed southeast-oriented stream valley first captured multiple south-oriented-oriented flood flow channels, which had moving flood waters across a surface as high as the present day figure 7 drainage divides. Headward erosion of the deep Thompson River valley next captured the south-oriented flood flow channels and flood waters on north ends of the beheaded flood flow channels reversed flow direction to erode the north-northeast oriented Thompson River tributary valleys. The Bush Branch valley extends from section 9 in the figure 7 northwest quadrant in a southeast, northeast, southeast, and northeast and east direction to the figure 7 northeast corner (and then to the Middle River as seen in figure 6). Again note how north-oriented Bush Branch tributary valleys are linked by shallow through valleys with south-oriented Thompson River tributary valleys. The map contour is 20 feet and the through valleys are defined by a single contour line on each side. The shallow through valleys suggest flood waters were flowing across the entire figure 7 map area on an erosion (and/or deposition?) surface at least as high as the highest figure 7 elevations today. Headward erosion of the Bush Branch valley, which included capturing some southeast-oriented flood flow channels and beheading and reversing some other south-oriented flood flow channels beheaded south-oriented flood flow routes to the newly eroded Thompson River valley. Flood waters on north ends of beheaded flood flow channels reversed flow direction to erode north-oriented Bush Branch tributary valleys.

East Nodaway River-Thompson River drainage divide area

Figure 8: East Nodaway River-Thompson River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 8 uses a reduced size topographic map to illustrate the East Nodaway River-Thompson River drainage divide area and is located south and west of the figure 6 map area (there is no overlap area with previous figures). Creston is the large town located just east of the figure 8 south center. The south and south-southwest oriented river flowing through Green Valley Lake and west of Creston to the figure 8 south center edge is the Platte River, which south of the figure 8 map area flows in a south and south-southwest direction to eventually reach the Missouri River. Note how the Platte River originates north of Spalding and how the south-oriented Platte River valley is linked to a northwest-oriented tributary to the west, south, southwest, south, and southwest oriented East Nodaway River, which flows from the figure 8 north center edge to the figure 8 southwest corner. West and south of the figure 8 map area the East Nodaway River flows in a southwest direction to join the south-oriented West Nodaway River and to form the south-oriented Nodaway River, which flows to the Missouri River. Note how the East Nodaway River and southwest oriented East Nodaway River tributaries have a number of northwest-oriented tributaries. The barbed tributary valleys were eroded by reversals of flood flow on north and northwest ends of beheaded south- and southeast-oriented flood flow routes. In the case of the East Nodaway River-Platte River drainage divide north of Spalding the beheaded flood flow route had been supplying flood waters to the actively eroding Platte River valley. Headward erosion of the East Nodaway River valley captured the flood flow and flood waters on the northwest end of the beheaded flood flow route reversed flow direction to erode the northwest-oriented tributary valley. Twelvemile Creek is the southeast-oriented stream flowing through Twelvemile Lake to the figure 8 southeast corner and south and east of the figure 8 flows to the south-oriented Thompson River. The southeast-oriented stream just north and east of Twelvemile Creek is Threemile Creek, which also flows to the south-oriented Thompson River (located just east of the figure 8 map area). The southeast-oriented stream in the figure 8 northeast corner is West Branch Creek, which is another Thompson River tributary. What is particularly interesting about the figure 8 map area is how headward erosion of southeast-oriented Thompson River tributary valleys and headward erosion of the southwest and south oriented East Nodaway River valley beheaded all south-oriented flood flow routes to the south and south-southwest oriented Platte River valley. Each of these south-oriented rivers eventually flows to the Missouri River, but in very different places (see figure 1). The figure 8 map evidence suggests headward erosion of each of the three different river valleys from the newly eroded Missouri River valley reached the figure 8 map area at approximately the same time.

Twelvemile Creek-Grand River drainage divide area

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

 

  • Figure 9 uses a reduced size topographic map to illustrate the Twelvemile Creek-Grand River drainage divide area located south and east of the figure 8 map area and includes overlap areas with figure 8. Creston is the large town located near the figure 9 northwest corner. Twelvemile Creek flows in a southeast direction from the south end of Twelvemile Lake located near the figure 8 north center edge to join the south-southeast oriented Thompson River just north of the figure 9 southeast corner. Afton is the town located on the northeast side of the Twelvemile Creek valley at the highway intersection east of Creston. Talmage is the place-name where the west to east oriented highway crosses the south, southeast, and south oriented Thompson River (east of Afton) and Threemile Creek is the southeast-oriented stream joining the Thompson River near Talmage. Southwest and south-southwest oriented streams flowing to the figure 9 west edge are Platte River tributaries with the southwest, west, and south-southwest oriented East Platte River being the tributary flowing to the west edge north of the southwest corner. Shannon City is the small town located just north of the figure 9 south center edge. the south- and southwest-oriented river flowing through Shannon City is the Grand River. Note how both the south-oriented East Platte River headwaters and the south-oriented Grand River headwaters begin just south of the west to east oriented highway extending from Creston to Afton. An east-oriented Twelvemile Creek tributary parallels the highway and both the East Platte River headwaters valley and the Grand River headwaters valley are linked by a shallow through valley with north-oriented tributary valleys to that east-oriented Twelvemile Creek tributary valley. In other words headward erosion of the southeast-oriented Twelvemile Creek tributary valley beheaded a south-oriented flood flow channel which was diverging, with some of the flood water flowing to the actively eroding Grand River valley while some of the flood water was flowing to the actively eroding East Platte River valley. This evidence suggests a giant south-oriented anastomosing channel complex extending across what are today separate Missouri River tributary drainage basins was being captured by headward erosion of multiple deep south-oriented Missouri River tributary valleys. Figure 10 below provides a more detailed topographic map of the Twelvemile Creek-Grand River drainage divide area to better illustrate valley relationships.

Detailed map of Twelvemile Creek-Grand River drainage divide area

Figure 10: Detailed map of Twelvemile Creek-Grand River 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 Twelvemile Creek-Grand River drainage divide area west of Afton, Iowa and seen in less detail in figure 9 above. Afton is the town located near the figure 10 east edge (north half). Twelvemile Creek flows in an east, south-southeast and southeast direction from the figure 10 north center edge (just north of the vertical word HIGHLAND) to the figure 10 east edge (south half). The unnamed east-northeast oriented stream between the highway and railroad in the figure 10 northwest quadrant is a Twelvemile Creek tributary. The Grand River originates in section 23 (near figure 10 center) and flows in a south-southeast direction to the figure 10 south edge (near center). The East Platte River originates in section 22 and flows in a south direction to the figure 10 south edge in section 34. Note north-oriented tributaries the east-northeast-oriented Twelvemile Creek tributary on the same alignments as the Grand River and East Platte River headwaters. A case can be made for very shallow through valleys eroded into what appears to be an almost level drainage divide separating the Twelvemile Creek tributary valley from the south-oriented Grand River and East Platte River valleys, however the evidence is subtle. The shallow through valleys are easiest to identify in sections 24, 25, and 19 and represent through valleys between a north-oriented Twelvemile Creek tributary valley and south-oriented Grand River headwaters valleys and also a southeast and east-northeast oriented Twelvemile Creek tributary valley (seen in figure 10 southeast quadrant). More subtle through valleys can be identified in sections 22 and 23. Orientations of north-oriented tributary valleys, north of the drainage divide and of the south-oriented East Platte River, Grand River, and the southeast and east-northeast oriented Twelvemile Creek tributary headwaters valleys and the shallow through valleys, provide evidence of diverging flood flow channels which flowed on an erosion (and/or deposition?) surface at least as high as the present day drainage divide. Headward erosion of the deep Twelvemile Creek valley and its unnamed east-northeast tributary valley (near north edge) captured the diverging flood flow routes in sequence from east to west. Flood waters on north ends of the beheaded flood flow routes reversed flow direction to erode the north-oriented Twelvemile Creek tributary valleys and tributary valleys to the unnamed east-northeast oriented Twelvemile Creek tributary valley. The figure 10 evidence demonstrates that at one time flood waters flowed simultaneously to what were then actively eroding Thompson River, Grand River, and Platte River valleys, all of which had eroded headward from the newly eroded Missouri River 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.

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