• The purpose of this essay is to use topographic map interpretation methods to explore the Platte River-Grand River drainage divide area landform origins in Gentry, Andrew and De Kalb Counties, Missouri, 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 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 Platte River-Grand River drainage divide area landform evidence in Gentry, Andrew, and De Kalb Counties, Missouri 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.

• Figure 1 provides a location map for the Platte River-Grand River drainage divide area in Gentry, Andrew, and De Kalb Counties, Missouri. Figure 1 illustrates regions in northwest Missouri, southwest Iowa, southeast Nebraska, and northeast Kansas. The Missouri River flows in a south-southeast direction from Omaha, Nebraska to Kansas City, Missouri and then turns to flow in an east-northeast direction to Brunswick, Missouri. From Brunswick the Missouri River flows in a south-southeast direction to the figure 1 south edge and south and east of figure 1 turns to flow in more of an east direction to join the south-oriented Mississippi River. The Grand River originates near Afton, Iowa (near figure 1 north center edge) and flows in a south and south-southwest direction into northern Missouri. Once in Missouri the Grand River turns to flow in a southeast direction and then turns to flow in a south direction to join the Missouri River near Brunswick. The Platte River originates near Creston, Iowa (close to the Grand River headwaters) and flows in a south and southwest direction adjacent to and parallel with the Grand River into northern Missouri. Once in northern Missouri the Platte River flows in a south direction to join the Missouri River near Platte City, Missouri (a short distance upstream from Kansas City) while the Grand River turns to flow in a southeast direction. The Platte River-Grand River drainage divide area of concern in this essay is located south of where the Grand River turns from flowing in a south direction to flowing in a southeast direction and is south of the town Stanberry, Missouri and north of highway 36. Towns shown on figure 1 included in the Platte River-Grand River drainage divide area in Gentry, Andrew, and De Kalb Counties in addition to Stanberry are King City and Maysville. Note south-southwest oriented Platte River tributaries and the north-northeast oriented Grand River tributary originating in the study region. These tributaries are illustrated in more detailed maps shown below.

• Drainage routes in the figure 1 map region and adjacent areas were established during immense south-oriented floods. Flood waters were derived from a rapidly melting North American ice sheet, which at the time figure 1 drainage routes were established was located north of the figure 1 map area. The ice sheet had been large, probably comparable in size if not larger than the modern-day Antarctic Ice Sheet. The North American ice sheet had been located in a deep “hole” which had been eroded by deep glacial erosion and further shaped by crustal warping caused by the ice sheet’s tremendous weight. The figure 1 map area represents a region which would have been located on the deep “hole’s” southern rim. The southern rim was deeply eroded by melt water flood erosion and significant thicknesses of material may have been stripped from the entire figure 1 region prior to present day drainage route establishment. No markers remain in the southern rim area to suggest how much erosion took place. Further, the massive south-oriented melt water floods through both flood water erosion and flood water deposition have probably so confused evidence that the southernmost ice sheet margin may never be determined. What can be determined is at the time figure 1 drainage routes were established the ice sheet southern margin was north of the figure 1 map area and was located in southeast South Dakota and southwest Minnesota. Further, at that time immense supra glacial melt water rivers were flowing off the ice surface and carving giant ice-walled and bedrock-floored canyons into the ice sheet surface. Water from the decaying ice sheet was flowing in a south direction across the entire figure 1 map area, although flow from the mouth of one giant ice-walled and bedrock-floored canyon was moving south  through eastern Nebraska and perhaps western Iowa while water from mouths of other huge ice-walled and bedrock-floored canyons was converging to flow south along the present day Mississippi River valley.

• Deep valleys eroded headward into the figure 1 map area from the Mississippi River valley located east of the figure 1 map area. South of the figure 1 map area in Arkansas the southeast-oriented Arkansas River valley eroded headward from the Mississippi River valley prior to headward erosion of the southeast-oriented White River valley to capture south-oriented floods flowing across the entire region. Headward erosion of the deep Missouri River valley (and east and northeast oriented tributary valleys located south of the figure 1 map area) next captured the south oriented flood flow and beheaded flood flow routes the newly eroded White River valley. South-oriented tributary valleys then eroded headward from the newly eroded Missouri River valley along and across the south-oriented flood flow routes. Headward erosion of the southeast-oriented Des Moines River valley and tributary valleys (seen in the figure 1 northeast corner area) next beheaded south-oriented flood flow to some Missouri River tributary valleys. The south-southeast oriented Missouri River valley segment eroded headward along what was a particularly large south and south-southeast oriented flood flow route, which was being fed by an immense melt water river flowing from the mouth of a giant ice-walled and bedrock-floored canyon, which had been carved into the surface of the decaying ice sheet. Evidence for that giant ice-walled and bedrock-floored canyon is described in essays which can be found listed under James River, ND Missouri River, and SD Missouri River on the sidebar category list.

• Note how west of the Platte River there are several closely spaced south-oriented Missouri River tributaries flowing parallel to and adjacent to each other. Also note how east of the Grand River there are multiple closely spaced south-oriented tributaries flowing to the southeast-oriented Grand River segment. The closely spaced and roughly parallel elongate south-oriented Missouri River and Grand River tributary (and tributary) drainage basins seen in figure 1 suggest present day south-oriented valleys eroded headward along what were once south-oriented channels in a gigantic south-oriented anastomosing channel complex. Such an anastomosing channel complex was captured by headward erosion of the deep Missouri River valley and southeast-oriented tributary valleys (such as the southeast-oriented Grand River valley segment identifiable in figure 1) and the flood waters were diverted to the south-oriented Mississippi River valley. Evidence seen on more detailed topographic maps illustrated in this essay further support this anastomosing channel origin interpretation. North-oriented barbed tributaries, such as the north-oriented Grand River tributary seen in figure 1, were eroded by reversals of south-oriented flood flow on north ends of beheaded flood flow routes. Essays describing nearby drainage divide area are listed under MO Missouri River on the sidebar category list.

• Figure 2 provides a more detailed location map for the Platte River-Grand River drainage divide area in Gentry, Andrew, and De Kalb Counties, Missouri. County names and boundaries are shown. Doniphan and Atchison Counties are located in Kansas while Holt, Andrew, Buchanan, and Platte Counties are in Missouri. The southeast, southwest, and southeast oriented Missouri River, which flows from the figure 2 northwest corner to the south edge, forms the Kansas-Missouri border. The Platte River flows in a south direction from the figure 2 north center (just west of the Gentry County west border) into and across eastern Andrew and Buchanan Counties and then turns to flow in a south-southwest direction in Platte County and joins the Missouri River south of the figure 2 map area. The south-oriented One Hundred and Two River is located just west of the Platte River and joins the Platte River in Buchanan County. The Third Fork Platte River originates in the Andrew northeast corner and flows in a south direction along the Andrew-De Kalb County border before turning to flow in a southwest direction to join the Platte River in Buchanan County. Between the Platte River and the Third Fork in southeast Andrew County is south-oriented Muddy Creek, which is a Third Fork tributary. East of the Third Fork in western De Kalb County is the south-southeast, south-southwest, and southwest oriented Little Third Fork which originates near King City in southwest Gentry County and which joins the Third Fork in the Buchanan County northeast corner. The Grand River flows in a south-southeast, east, and southeast direction from the figure 2 north edge (near Gentry County northwest corner) to the Gentry County southeast corner and then in a southeast direction across Daviess County to the figure 2 east center edge. Tributaries of interest in this essay are tributaries located south and west of the Grand River. Starting in the north Island Creek flows in a north direction to join southeast and east oriented Wildcat Creek near Stanberry in western Gentry County. Lost Creek originates south of Ford City in southern Gentry County and flows in a south direction into north central De Kalb County  before turning to flow in an east-southeast direction to join north-northeast oriented Grindstone Creek, which joins the Grand River in the Daviess County northwest corner area. Note the north-northeast oriented West Fork Lost Creek south of Maysville in De Kalb County. South of the north-northeast oriented West Fork Lost Creek and Grindstone Creek headwaters in southern De Kalb County are headwaters of the south-southwest oriented Little Platte River, which joins the Platte River in the Platte County northeast corner area. In the De Kalb County southwest quadrant are headwaters of south-southwest and southwest oriented Castile Creek, which joins the Platte River in the Buchanan County southeast corner area.

• While Platte River tributaries in the study region are dominantly oriented in south directions, the figure 2 map demonstrates Grand River tributaries, even if they have south-oriented headwaters and/or segments, are oriented in multiple directions and have significant north-oriented tributaries and/or valley segments. This difference between the study region Platte River tributaries and the Grand River tributaries is because headward erosion of the deep southeast-oriented Grand River valley and its tributary valleys beheaded south-oriented flood flow routes to what were then actively eroding south-oriented Platte River valleys. Flood waters on north ends of beheaded flood flow routes reversed flow direction to erode the north-oriented tributary valleys. Headward erosion of the east-southeast oriented Lost Creek valley (from the reversed flood flow eroded valley being eroded on the Grindstone Creek alignment) proceeded slightly in advance of Grand River valley headward erosion and beheaded south-oriented flood flow moving to the actively eroding Little Platte River valley. Flood waters on the north end of the beheaded flood flow reversed flow direction to erode the north-northeast oriented West Fork Lost Creek. At the same time the Lost Creek valley captured south-oriented on a flood flow route extending south from the Ford City area. Subsequently Grand River valley headward erosion into central Gentry County and headward erosion of the Wildcat Creek valley beheaded the south-oriented flood flow route to the actively eroding Lost Creek valley head near Ford City. Again flood waters on the north end of the reversed flood flow route reversed flow direction to erode a north-northwest oriented Wildcat Creek tributary valley. Further west headward erosion of the east-oriented Wildcat Creek valley to the Stanberry area behead south-oriented flood flow to what was then the actively eroding south-oriented Third Fork Platte River valley. Again flood waters on the north end of the beheaded flood flow route reversed flow direction to erode the north-oriented Island Creek valley. Evidence for many additional flood flow reversals can be found on more detailed topographic maps, a few samples of which are provided below.

• Figure 3 uses a reduced size topographic map to illustrate the Wildcat Creek-Turkey Creek drainage divide area near Stanberry, Missouri. The Grand River flows in a south-southeast direction in the figure 3 northeast corner. The Platte River flows in a south direction near the figure 3 west edge. Stanberry is the larger town located in the figure 3 northeast quadrant, Conception is the smaller town in the northwest quadrant, and Island City is the even smaller town located in the southeast quadrant. Guilford is a smaller town in the southwest quadrant. Wildcat Creek flows in a southeast and east-southeast direction from the figure 3 north edge (west of center) to Stanberry and then in an east-northeast direction to join the Grand River just east of the figure 3 east edge. The north-oriented stream flowing from Island City to join Wildcat Creek near Stanberry is Island Creek. Turkey Creek is the south, southeast, and east oriented stream joining Island Creek near Island City. King Branch is the south-southeast oriented Turkey Creek tributary located in the figure 3 south center area. Note how Turkey Creek also has north-oriented tributaries from the south. East of Island Creek in the figure 3 southeast quadrant is north-northwest oriented Walnut Fork, which also has some north-northeast oriented tributaries. The presence of north-oriented drainage systems in a region surrounded by major south-oriented river valleys resulted because headward erosion of the deep east-oriented Wildcat Creek valley (from the actively eroding Grand River valley head) beheaded south-oriented flood flow channels in what was a giant south-oriented anastomosing channel complex. Flood waters on north ends of beheaded flood flow routes reversed flow direction to erode the north-oriented valleys. Headward erosion of the east-oriented Turkey Creek valley (from the actively eroding and newly reversed Island Creek valley) was slightly in advance of Wildcat Creek valley headward erosion and was able to capture flood flow from west of the actively eroding Wildcat Creek valley head. Headward erosion of the deep south-oriented Platte River valley along one of the south-oriented flood flow channels prevented the Wildcat Creek valley from eroding further to the west. Further evidence supporting this flood origin interpretation is found in shallow through valleys linking north-oriented Wildcat Creek tributary valleys with south-oriented Turkey Creek tributary valleys. For example, note how the south-southeast oriented King Branch valley is linked by shallow through valleys with north-oriented tributary valleys to an east-northeast oriented Wildcat Creek tributary.

• Figure 4 illustrates the Turkey Creek-Third Fork Platte River drainage divide area located south of the figure 3 map area and includes overlap areas with figure 3. The south-oriented Platte River valley is located along the figure 4 west edge. King City is the town located in the figure 4 southeast quadrant. Island City is located east of the figure 4 north center area. Turkey Creek flows across the figure 4 north center area to join north-oriented Island Creek at Island City. Remember, Island Creek flows to Wildcat Creek, which flows to the Grand River. The south-oriented stream located west of King City and flowing to the figure 4 south center edge is the Third Fork Platte River and is a Platte River tributary. Note how the south-oriented Third Fork Platte River valley is linked by shallow through valleys with the north-oriented Island Creek valley. The map contour interval is ten meters and narrow through valleys defined by one contour line on each side can be identified. However, study of the figure 4 map reveals even higher elevations on both sides of the narrow through valleys so much broader through valleys defined by an additional contour line on each can be seen. Figure 5 below provides a detailed topographic map to better illustrate the through valleys. East of King City the south-southeast oriented stream flowing to the figure 4 east edge (just north of the southeast corner) is the headwaters of Lost Creek. Lost Creek will be seen again in figures 6-10. The north-northwest oriented stream in the figure 4 northeast quadrant (east of the highway) is Walnut Fork. Note how the north-northwest Walnut Fork alignment is almost the same as the south-southeast oriented Lost Creek alignment. Valley orientations and shallow through valleys where they exist provide evidence of south-oriented flood flow channels to the actively eroding Lost Creek valley, Third Fork Platte River valley, and their tributary valleys prior to headward erosion of the deep east-oriented Wildcat Creek valley north of the figure 4 map area. Headward erosion of the deep Wildcat Creek valley as already mentioned beheaded and reversed south-oriented flood flow so as to erode the north-oriented Walnut Fork and Island Creek valleys.

• Figure 5 provides a detailed topographic map of the Island Creek-Third Fork Platte River drainage divide area seen in less detail in figure 4 above. The south-southeast oriented stream flowing to the figure 5 south center edge is the Third Fork Platte River and south of the figure 5 map area flows in a south direction and eventually joins the Platte River. The north-oriented stream flowing to the figure 5 north center edge is Island Creek, which joins Wildcat Creek, which then flows to the Grand River. Note the southeast-oriented Island Creek tributary from the west. Two well-defined north-south oriented through valleys can be seen in figure 5 linking the north-oriented Island Creek valley with the south-oriented Third Fork Platte River valley. The first of the through valleys is located in the section 24 northeast quadrant and has a valley floor elevation of between 308 and 312 meters (the map contour interval is 4 meters). Elevations on both sides of the through valley rise to at least 324 meters (and 328 meters by going further in either direction). The other through valley is located in the section 18 southeast quadrant and has a valley floor elevation of between 316 and 320 meters. The through valleys are not deep, but are water eroded landforms and were eroded by south-oriented flood flow prior to headward erosion of the deep east-oriented Wildcat Creek valley north of the figure 5 map area. Headward erosion of the deep Wildcat Creek valley from what was then the actively eroding Grand River valley, which had eroded headward from the actively eroding Missouri River valley, beheaded the south-oriented flood flow, which had been flowing to the actively eroding Third Fork Platte River valley. Flood waters on north ends of beheaded south-oriented flood flow channels reversed flow direction to erode the north-oriented Island Creek valley and its tributary valleys and to create the Island Creek-Third Fork Platte River drainage divide. Other shallow through valleys linking the Third Fork Platte River valley with north-oriented Turkey Creek tributary valleys and also with northwest and southwest oriented Platte River tributary valleys can be seen by studying detailed topographic maps of regions north and west of figure 5.

• Figure 6 provides a reduced size topographic map of the Walnut Fork-Lost Creek drainage divide area located east of the figure 4 map area and south and east of the figure 3 map area. Stanberry is the town located in the figure 6 northwest corner. King City is the town near the figure 6 southwest corner. Wildcat Creek joins the Grand River just north of the word COOPER (just east of Stanberry) and the Grand River then flows in an east, south, and southeast direction to the figure 6 southeast corner. Island Creek is the north-oriented Wildcat Creek tributary located next to the figure 6 west edge. Walnut Fork is the north-northwest oriented tributary joining Wildcat Creek just west of the word COOPER. Darlington is the small town located in the figure 6 north center area near where the Grand River turns from flowing in an east direction to flowing in a south direction. The north-northeast oriented tributary joining the Grand River near Darlington is Long Branch, which originates near Ford City. Note how the south-oriented Grand River segment consists of a series of incised meanders where the Grand River valley is much narrower than further upstream. While not seen in the figure 6 map the south-oriented East Fork Grand River joins the Grand River just north of the south-oriented Grand River segment and the south-southeast oriented Middle Fork Grand River joins the Grand River almost at the same point suggesting the presence of two converging south-oriented flood flow channels which were captured by headward erosion of the deep southeast-oriented Grand River valley which eroded headward into the figure 6 southeast quadrant. Gentryville is a small town located in next to one of the south-oriented Grand River meanders east of the figure 6 center area. Stillhouse Branch is a north, northeast, and southeast oriented tributary joining the Grand River near Gentryville. The north-oriented Stillhouse Branch headwaters valley was eroded by a reversal of flood flow on the north end of a beheaded flood flow route. Note how downstream from the south-oriented Grand River segment the Grand River again flows in an east direction before turning to flow in a southeast direction. Campbell Creek is a north-oriented tributary flowing to the east oriented Grand River segment just east of that elbow of capture and Hickory Creek is a north-northeast oriented tributary flowing to east and northeast-oriented Owl Creek, which joins the Grand River at the elbow of capture. The north-oriented Campbell Creek and north-northeast oriented Hickory Creek valleys provide evidence of flood flow reversals on north ends of beheaded south-oriented flood flow channels.

• Figure 7 illustrates the Hickory Creek-North Fork Lost Creek drainage divide area south and east of the figure 6 map area and includes overlap areas with figure 6. McFall is the town located in the figure 7 northeast corner area, Ford City is located near the northwest corner, and Santa Rosa is near the southeast corner. Berlin is the place-name near the figure 7 center. The Grand River flows in an east and southeast direction from the figure 7 north center area to the east center edge. Owl Creek originates south of Ford City and flows in a southeast, east, and northeast direction to join the Grand River near the figure 7 north center edge. Hickory Creek is a north-northeast oriented Owl Creek tributary aligned with the northeast-oriented Owl Creek segment. Lost Creek is the south-southeast and south oriented stream located in the figure 7 west center area and flowing to the figure 7 south edge (west half). The East Fork Lost Creek flows in an east direction north of the word GRANT and then turns to flow in a south-southeast and south direction to the figure 7 south center edge (near the south edge the stream name changes to Middle Fork). Note how the south-southeast oriented East Fork Lost Creek valley is linked by a shallow through valley with a north-northwest oriented Hickory Creek tributary valley. Further east, just south of Berlin, the North Fork Lost Creek originates and flows in a southeast and south direction to the figure 7 south edge (just east of center). Note how the southeast-oriented North Fork Lost Creek valley is linked by a through valley with a  north- and northwest-oriented Hickory Creek tributary valley. South of the figure 7 map area the various Lost Creek forks join east-southeast oriented Lost Creek, which then flows to north-northeast oriented Grindstone Creek, which joins the southeast-oriented Grand River as a barbed tributary. The valley orientations and through valleys provide evidence of one time diverging and converging flood flow channels prior to headward erosion of the deep Grand River valley into the figure 7 north center edge area. Headward erosion of the deep Grand River valley beheaded south-oriented flood flow channels which were moving flood water to actively eroding Lost Creek tributary valleys and flood waters on north ends of the beheaded flood flow channels reversed flow direction to erode the north-oriented Owl Creek valley segment, Hickory Creek valley, and Hickory Creek tributary valleys and also to create the present day Hickory Creek-Lost Creek drainage divide.

• Figure 8 provides a detailed map of the Hickory Creek-East Fork Lost Creek drainage divide area seen in less detail in the figure 7 map area. Berlin is the small cluster of buildings at the corner of sections 25, 26, 35, and 36 in the northeast quadrant. Hickory Creek flows in an east-southeast direction from section 29 in the northwest quadrant into the section 28 southwest quadrant and then turns to flow in a northeast direction to the figure 8 north center edge. North-oriented streams in sections 27 and 26 are Hickory Creek tributaries. Note north-oriented Hickory Creek tributaries shown entirely in the figure 8 map area and how the tributary valleys are linked by shallow through valleys with south-oriented stream valleys. For example, along the border separating section 34 and section 9 a shallow through valley links a north-oriented Hickory Creek tributary valley with a south-oriented tributary valley to the east and south-southeast oriented East Fork Lost Creek valley, which is located in the figure 8 south center area. The map contour interval is 4 meters and the through valley floor elevation is between 300 and 304 meters. Elevations east of the through valley rise to at least 316 meters while elevations west of the through valley rise more than 320 meters. Much shallower through valleys can be seen in section 8 linking south-oriented tributary valleys to the east-oriented East Fork Lost Creek valley with north-oriented Hickory Creek tributary valleys. The south-southeast oriented headwaters of the North Fork Lost Creek flow to the figure 8 east edge just north of the southeast corner. Note how in the section 35 northwest quadrant a shallow through valley links the southeast-oriented North Fork Lost Creek headwaters valley with a north-oriented Hickory Creek tributary valley. The section 35 through valley floor elevation is between 296 and 300 meters and hills on both sides rise to at least 316 meters. Other shallower through valleys can also be found. The through valleys and valley orientations are again evidence of former south-oriented diverging and converging flood flow channels in what was once a south-oriented anastomosing channel complex supplying water to actively eroding Lost Creek tributary valleys. Headward erosion of the deep Grand River valley (north of the figure 8 map area) beheaded the flood flow channels and flood waters on north ends of the beheaded flood flow channels reversed flow direction to erode the north-oriented Hickory Creek valley and the north-oriented Hickory Creek tributary valleys.

• Figure 9 illustrates the Third Fork Platte River-Lost Creek drainage divide area located west and south of the figure 7 map area and includes overlap areas with figure 7. Maysville is the town near the southeast corner and Union Star is the town located south of the northwest corner. The Third Fork Platte River flows in a south direction near the figure 9 west edge and south of the figure 9 map area eventually joins the Platte River. Crooked Creek is the labeled southwest-oriented tributary joining the Third Fork Platte River in the figure 9 west center area. Note several northwest-oriented Crooked Creek tributary valleys. The Little Third Fork is the southeast, south-southwest, and south oriented stream flowing from the figure 9 north edge (west of center) across the figure 9 center area to the south edge. South of the figure 9 map are the Little Third Fork Platte River joins the Third Fork Platte River, which subsequently joins the Platte River. Note southeast-oriented Little Third Fork Platte River tributaries from the west and how some of the southeast-oriented tributaries are aligned with northwest-oriented Crooked Creek tributary valleys. Lost Creek flows in a south direction from the figure 9 north edge (east of center and then turns to flow in an east-southeast direction to the figure 9 east center edge. As previously seen east of the figure 9 map area Lost Creek flows to north-northeast oriented Grindstone Creek, which flows to the southeast-oriented Grand River. Note how the Little Third Fork Platte River and Lost Creek valleys are located very close to each other before the Lost Creek valley turns to the east while the Little Third Fork Platte River valley continues in a south direction. The map contour interval is 10 meters and near the place-name of Wood the Little Third Fork Platte River valley floor elevation is between 290 and 300 meters while the Lost Creek valley floor elevation is between 270 and 280 meters. The drainage divide elevation is between 310 and 320 meters. The closeness of the two south-oriented valleys suggests the valleys originated as channels in a south-oriented anastomosing channel complex. Headward erosion of the east-southeast oriented Lost Creek valley captured south-oriented flood flow in the eastern channel and diverted the flood flow to what was then the newly reversed Grindstone Creek valley, which had been beheaded by Grand River valley headward erosion. Apparently the Little Third Fork Platte River valley channel was deep enough that Lost Creek valley headward erosion could not capture it.

• Figure 10 illustrates a detailed topographic map of the Little Third Fork Platte River-Lost Creek drainage divide area seen in less detail in figure 9 above. Wood is a small cluster of buildings located east of the figure 10 south center area and is shown as a place-name on figure 9. Lost Creek flows in a well-defined south-oriented valley from the figure 10 north edge to the south edge in the figure 10 east half (east of Wood). Note how some Lost Creek tributaries from the west are oriented in southeast directions, although other tributaries are oriented in east and even northeast directions. Lost Creek tributaries from the east tend to be oriented in south and southwest directions. Spot elevations marked on the Lost Creek valley floor range from 270 meters near the figure 10 south edge to 280 meters near the north edge. The Little Third Fork Platte River flows in a somewhat narrower and shallower valley in a south-southeast, south, and south-southwest direction in the figure 10 west half (west of Wood). Note how Little Third Fork Platte River tributaries from the east are very short and how the Little Third Fork Platte River-Lost Creek drainage divide is an asymmetric drainage divide with tributaries to Lost Creek being much better developed than tributaries to the Little Third Fork Platte River. However, Little Third Fork Platte River tributaries from the west appear to be well-developed and generally flow in east and southeast directions. Spot elevations on the Little Third Fork Platte River valley range from 292 meters near the figure 10 south edge to 302 meters near the north edge. Study of the Little Third Fork Platte River drainage divide, which is also the divide between the Platte River drainage basin and the Grand River drainage basin, reveals shallow through valleys linking tributary valleys on opposite sides, although the through valleys are usually defined by a single 4-meter contour line. Drainage divide elevations are approximately 40 meters higher than the Lost Creek valley floor and approximately 20 meters higher than the Little Third Fork Platte River valley floor. The figure 10 evidence suggests southeast and east oriented flood flow did cross the drainage divide to the actively eroding Lost Creek valley and its east and southeast oriented tributary valleys, however the evidence also suggests no major southeast or east oriented flood flow channels were beheaded in this region (as compared to former channels seen in some earlier figures, for example figures 5 and 8). In other words, a south-oriented channel on the Little Third Fork Platte River alignment had probably already been established and the east and southeast-oriented flood flow to the actively eroding Lost Creek valley might have been overflow spilling from the smaller south-oriented channel.

Additional information and sources of maps studied