Abstract:

This essay uses topographic map evidence to interpret landform origins in the South Platte River-Frenchman Creek drainage divide area in the Colorado northeast corner. The South Platte River originates in the Colorado Front Range and flows in a southeast, north-northeast, and east-southeast direction before turning to flow in a northeast direction to the Colorado northeast corner and then in an east direction to join the southeast oriented North Platte River in western Nebraska and to form the Nebraska Platte River. Frenchman Creek headwaters originate along the South Platte River southeast valley rim and flow in northeast, east, and east-southeast directions to eventually converge in east-southeast oriented Frenchman Creek, which flows to the east oriented Republican River, which then flows across southern Nebraska before turning to flow into Kansas to join the east oriented Kansas River. The drainage divide between the South Platte River and Frenchman Creek in the Colorado northeast corner is an asymmetric drainage divide with the South Platte River valley ranging from about 90 to more than 180 meters deep. Short northwest and north-northwest oriented streams drain the South Platte River southeast valley wall and some of those streams reach the South Platte River as barbed tributaries. Shallow through valleys cross the South Platte River southeast valley rim and link the northwest and north-northwest drainage routes with the Frenchman Creek headwaters. The asymmetric drainage divide, barbed tributaries, through valleys, and valley orientations are interpreted to have been formed when the deep northeast oriented South Platte River valley eroded headward across southeast oriented flood flow moving to what at that time was a newly eroded east oriented Republican River valley in southern Nebraska. Floodwaters are interpreted to have been derived from the western margin of a thick North American ice sheet and were flowing from western Canada to the newly eroded Republican River valley at a time when the Missouri River tributary valleys were being eroded headward in sequence from the southeast to the northwest. The short northwest and north oriented South Platte River tributary drainage routes were created when floodwaters on northwest and north ends of beheaded flood flow routes reversed flow direction to flow to the much deeper and newly eroded South Platte River valley.

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 are listed on the sidebar category list under their appropriate Missouri River tributary drainage basin, Missouri River segment drainage basin (by state), and/or state in which the Missouri River drainage basin is located.

Introduction

The purpose of this essay is to use topographic map interpretation methods to explore the South Platte River-Frenchman Creek drainage divide area landform origins in the Colorado northeast corner. 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 Missouri River drainage basin landform origins research project essays 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 South Platte River-Frenchman Creek drainage divide area landform evidence in the Colorado northeast corner will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

South Platte River-Frenchman Creek drainage divide area location map

Figure 1: South Platte River-Frenchman 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 provides a location map for the South Platte River-Frenchman Creek drainage divide area in the Colorado northeast corner with western Nebraska in the north and east. Kansas is located south of Nebraska in the east half of figure 1. The South Platte River flows in a northeast direction from Fort Morgan, Colorado at the west edge of figure 1 (near southwest corner) to the northeast corner of Colorado and then flows in an east direction to join the southeast and east oriented North Platte River near North Platte, Nebraska and to form the Nebraska Platte River, which then flows to the south and east oriented Missouri River. The Republican River flows in an east-northeast and east direction from Haigler, Nebraska (near south center edge of figure 1 and at the corner of Nebraska, Colorado, and Kansas) to the east edge of figure 1. East of figure 1 the Republican River flows in an east direction across southern Nebraska until it turns to flow in a southeast direction into Kansas to join the east oriented Kansas River, which then flows to the Missouri River. Frenchman Creek headwaters are located south and east of the South Platte River in the northeast corner of Colorado and originate east of Sterling, Colorado. South of Frenchman Creek in northeast Colorado are east and east-southeast oriented streams originating near the South Platte River and flowing toward the Republican River, but which disappear as surface streams. Frenchman Creek flows in an east-southeast direction from the northeast corner of Colorado to join the Republican River near Culbertson, Nebraska. Frenchman Creek and the Republican River have several long southeast and east-southeast oriented tributaries from the north.

The South Platte River also has long east-southeast and southeast oriented tributaries from the west and north. Near the southwest corner of figure 1 the South Platte River has north oriented tributaries from the south, but further downstream no South Platte River tributaries from the south are shown in figure 1 and the South Platte River-Frenchman Creek drainage divide is an asymmetric drainage divide. The asymmetric South Platte River-Frenchman Creek drainage divide in northeast Colorado was created when the South Platte River valley eroded headward across southeast oriented flood flow moving to what was at that time the newly eroded east oriented Republican River valley in southwest Nebraska. Floodwaters were derived from the western margin of a thick North American ice sheet and flowed from western Canada to and across western Nebraska and northeast Colorado to reach what was at that time the actively eroding Republican River valley. At that time the southeast oriented North Platte River valley did not exist, although at that time the North Platte River valley and tributary valleys were probably eroding headward and beheading flood flow routes to the newly eroded South Platte River valley and tributary valleys. West of figure 1 the South Platte River valley eroded headward across south oriented flood flow nearer to what was at that time the emerging Colorado Front Range. The mountains were emerging as floodwaters flowed across them and their emergence was probably caused by ice sheet related crustal warping and deep erosion of surrounding regions by the immense volumes floodwaters moving across the region. Floodwaters on north ends of beheaded flood flow routes reversed flow direction to create north oriented South Platte River tributary drainage routes and the north-northeast oriented South Platte River drainage route (south and west of figure 1).

Detailed location map for South Platte River-Frenchman Creek drainage divide area

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

Figure 2 provides a detailed location map for the South Platte River-Frenchman Creek drainage divide area in the Colorado northeast corner. Logan, Sedgwick, and Phillips are counties in the northeast corner of Colorado. The Nebraska panhandle is located north of Logan and Sedgwick Counties and southern Nebraska is located east of figure 2. The South Platte River flows in a northeast direction from near the southwest corner of figure 2 to near the northeast corner of figure 2. Tributaries from the north are oriented in south-southeast directions and while generally short are present and are shown in figure 2. Two short northwest oriented tributaries are located near the southwest corner of figure 2 and two relatively short north-northwest oriented tributaries are shown in Sedgwick County. Otherwise figure 2 shows no South Platte River tributaries from the south and east. Frenchman Creek headwaters originate south of the railroad and east of Sterling in Logan County and flow in an east direction to near Holyoke in Phillips County and then turn to flow in an east-southeast direction to the east edge of figure 2. East of figure 2 Frenchman Creek flows in an east-southeast direction to join the east oriented Republican River. Wildhorse Creek originates just north of the Frenchman Creek headwaters and flows in an east-northeast and east-southeast direction to the east edge of figure 2 and east of figure 2 joins east-southeast oriented Frenchman Creek. Sand Creek (south) originates south of the Frenchman Creek headwaters in Logan County and flows in an east direction into Phillips County where it disappears as a surface stream in the region south of Holyoke. Sand Creek (north) is located in Sedgwick County and flows in an east-southeast, east, and east-southeast direction to the east edge of figure 2 (north of center). East of figure 2 Sand Creek (north) flows in an east direction to join southeast oriented Spring Creek, which then flows to east-southeast oriented Frenchman Creek. Marks Butte is a labeled high point in the southwest corner of Sedgwick County. The asymmetric drainage divide is apparent in figure 2 and the short northwest oriented South Platte River tributary drainage routes were created by reversals of flood flow on northwest ends of beheaded flood flow routes. The two Sand Creeks in the region suggest an abundance of sand, which could be flood-transported and deposited materials. With the exception of the South Platte River and irrigation canals drainage routes in figure 2 are shown with dashed lines suggesting the streams are intermittent and that the region is dry, which could mean there are wind blown sand deposits in the region.

South Platte River-Sand Draw drainage divide area

Figure 3: South Platte River-Sand Draw drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of South Platte River-Sand Draw drainage divide area. The map contour interval for figure 3 is 10 meters. The South Platte River flows in an east and northeast direction from the west edge of figure 3 (north half) to the north edge of figure 3 (east of center) and north and east of figure 3 flows in a northeast and east direction to join the North Platte River and to form the Nebraska Platte River. Julesburg, Colorado is the town located near the north center edge of figure 3. Ovid is the smaller town in the South Platte River valley west of Julesburg and is located where south oriented Lodgepole Creek joins the east and northeast oriented South Platte River. Southeast oriented streams in the southeast quadrant of figure 3 are headwaters of southeast and east oriented Sand Creek, which east of figure 3 flows to southeast oriented Spring Creek, which then flows to east-southeast oriented Frenchman Creek, which flows to the east oriented Republican River. Sand Draw is an east oriented Sand Creek tributary located near the south center edge of figure 3. The South Platte River valley floor near Julesburg has an elevation of approximately 1060 meters. Elevations on the upland surface directly south of Julesburg and south of the South Platte River valley are approximately 1150 meters. These elevations suggest the South Platte River south valley wall is approximately 90 meters high. Numerous north-northwest oriented South Platte River tributaries drain the South Platte River south valley wall, but none of these tributaries extends headward into the adjacent upland, which is drained by the southeast oriented Republican River tributaries. The 90-meter deep South Platte River valley eroded headward across southeast oriented flood flow moving to what at that time was the actively eroding Republican River valley (south and east of figure 3). As the deep South Platte River valley eroded headward floodwaters on the north ends of beheaded flood flow routes reversed flow direction to flow in northwest and north directions to the newly eroded and deep South Platte River. These reversed floodwaters created the numerous north-northwest oriented South Platte River tributary drainage routes seen in figure 3. Apparently floodwaters were flowing as sheets of flood flow and were not concentrated in deep channels, which accounts for the lack of longer northwest or north oriented South Platte River tributary drainage routes.

Detailed map of South Platte River-Sand Creek drainage divide area

Figure 4: Detailed map of South Platte River-Sand Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 provides a detailed topographic map of the South Platte River-Sand Creek drainage divide area seen in less detail in figure 3. The map contour interval for figure 4 is 10 feet with dotted contour lines at 5 foot intervals on the upland surface in the southeast half of figure 4. Julesburg, Colorado is the town located in the northwest corner of figure 4. The South Platte River flows in a northeast direction across the northwest corner of figure 4 and crosses the 3450-foot contour line near Julesburg. The Radio Tower base near the northwest corner of section 23 on the upland south of Julesburg has an elevation of more than 3790 feet suggesting the South Platte River southeast valley wall at Julesburg is approximately 340 feet deep. The radio tower in section 23 is located at one of the higher elevations on the South Platte River southeast valley wall rim with some lower rim elevations being less than 3720 feet. A northwest to southeast oriented through valley in sections 16 and 17  (in the southeast quadrant of figure 4) links a northwest oriented South Platte River tributary valley with a southeast oriented valley draining to southeast and east oriented Sand Creek and has an elevation of less than 3720 feet. A high point on the South Platte River valley rim in the southeast quadrant of section 5 exceeds 3740 feet suggesting the through valley is more than 20 feet deep. The through valley was probably eroded as a shallow southeast oriented flood flow channel. The South Platte River southeast valley wall is drained by numerous northwest and north-northwest oriented South Platte River tributaries. These tributaries flow to the northeast oriented South Platte River as barbed tributaries, which provides more evidence headward erosion of the 340-foot deep South Platte River valley beheaded southeast oriented flood flow. Flood flow on northwest ends of beheaded flood flow routes reversed flow direction to flow in northwest directions into the newly eroded and deep northeast oriented South Platte River valley. Apparently the amount of reversed flood flow was not great as the northwest oriented South Platte River tributary valleys do not extend far into the upland surface to the southeast. The upland surface in the southeast half of figure 4 slopes gradually in a southeast direction with drainage routes flowing to southeast and east oriented Sand Creek, which flows to southeast oriented Spring Creek, which then flows to east-southeast oriented Frenchman Creek, which flows to the east oriented Republican River. Elevations near the southeast corner of figure 4 are less than 3690 feet, which is 30 to 100 feet lower than elevations along the present day South Platte River-Sand Creek drainage divide.

South Platte River-Wildhorse Creek drainage divide area

Figure 5: South Platte River-Wildhorse Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates a topographic map of the South Platte River-Wildhorse Creek drainage divide area south and west of figure 3 and includes an overlap area with figure 3. The map contour interval for figure 5 is 10 meters. The South Platte River can just barely be seen in the northwest corner of figure 5 and is flowing in a northeast direction. The South Platte River valley floor elevation in the northwest corner of figure 5 is less than 1120 meters. Elevations on the valley rim at the west edge of figure 5 exceed 1250 meters suggesting the South Platte River valley is approximately 130 meters deep. The South Platte River southeast valley wall is again drained by short north-northwest and north oriented tributaries while the upland surface to the south and east is drained in an east and east-southeast direction with water eventually reaching east-southeast oriented Frenchman Creek and the east oriented Republican River. Wildhorese Creek is the east-northeast and east-southeast oriented stream flowing from the west edge of figure 5 (near southwest corner) to the south edge of figure 5 (east of center). South and east of figure 5 Wildhorse Creek water eventually reaches Frenchman Creek. East-southeast and east oriented streams flowing to the east edge of figure 5 flow towards southeast oriented Spring Creek, but end as surface streams in sand covered regions. Marks Butte is the labeled high point north of the center of figure 5 and reaches an elevation of 1241 meters, which is only 30 to 50 meters higher than the surrounding upland surface, which slopes in an east and/or east-southeast direction. The north-northwest and north oriented South Platte River tributary drainage routes were again created by reversals of flood flow on the north ends of beheaded flood flow routes with water flowing in north-northwest and north directions into the much deeper and newly eroded South Platte River valley. The gentle east and/or east-southeast oriented upland surface slope probably prevented large volumes of floodwaters from reversing flow direction and creating more significant north and northwest oriented tributary drainage routes.

Detailed map of South Platte River-Marks Butte drainage divide area

Figure 6: Detailed map of South Platte River-Marks Butte drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 provides a detailed topographic map of the South Platte River-Marks Butte drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 10 feet. The north-northwest oriented slope in the northwest quadrant of figure 6 is located along the rim of the northeast oriented South Platte River southeast valley wall. A high point along the rim is located near the west center edge of figure 6 and reaches an elevation 4093 feet. Marks Butte is located in section 29 (in southeast quadrant of figure 6) and reaches an elevation of 4072 feet. It is difficult to tell from topographic map evidence how these high points were formed, but for purposes of this discussion the assumption is made the high points are erosional residuals. If this assumption is incorrect then interpretations made in this discussion may be incorrect. Assuming the high points are erosional residuals there is a northwest to southeast oriented through valley on the west side of Marks Butte with a valley floor elevation of less than 4000 feet. Based on the Marks Butte elevation this through valley is at least 72 feet deep and was probably eroded by southeast oriented flood flow moving across the region prior to headward erosion of the deep northeast oriented South Platte River valley. Small north-northwest to south-southeast hills can be seen in figure 6. It is possible some or all of these streamlined hills are wind deposited features, although it is possible some or all of these streamlined hills are erosional residuals. Assuming some or all of these streamlined hills are erosional residuals the streamlined hills provide further evidence of south-southeast oriented flood flow across the region. The north-northwest valleys on the South Platte River valley wall in the northwest quadrant of figure 6 were eroded by reversals of flood flow at the time the deep northeast oriented South Platte River valley eroded headward across the southeast oriented flood flow. Floodwaters reversed flow direction to flow into the much deeper and newly eroded South Platte River valley.

South Platte River-North Fork Frenchman Creek drainage divide area

Figure 7: South Platte River-North Fork Frenchman Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the South Platte River-North Fork Frenchman Creek drainage divide area south and west of figure 5 and there is no overlap area with figure 5. The map contour interval for figure 7 is 10 meters. The South Platte River flows in a northeast and north-northeast direction from the west center edge of figure 7 to the north edge of figure 7 (west half). Elevations on the South Platte River valley floor near the west edge of figure 7 are slightly above 1190 meters and decrease to about 1170 meters near the north edge of figure 7. The rim of the South Platte River southeast valley wall extends in a northeast direction from the south edge of figure 7 (west of center) to the east edge of figure 7 (north half). The North Reiradon Hill elevation on the southeast valley rim (near the south edge of figure 7) is 1375 meters while elevations along the valley rim near the east edge of figure 7 are slightly above 1310 meters. These elevations suggest the South Platte River valley is between 140 and 185 meters deep. The northeast oriented stream labeled “North” in the southeast quadrant of figure 7 is the North Fork Frenchman Creek. East of figure 7 the North Fork Frenchman Creek flows in an east direction and eventually turns in an east-southeast direction to join the South Fork and to form east-southeast oriented Frenchman Creek, which eventually joins the east oriented Republican River. The northeast and east oriented drainage routes south and east of the South Platte River valley rim and north and east of the North Fork Frenchman Creek headwaters are headwaters of Wildhorse Creek with water eventually ending up in Frenchman Creek. In other words the upland surface south and east of the South Platte River valley rim drains to Frenchman Creek and the Republican River and not to the adjacent South Platte River. The South Platte River southeast valley wall is drained by multiple north and northwest oriented streams, which originate and end on the valley wall slope. These north and northwest oriented South Platte River tributary drainage routes were created by reversals of flood flow when the South Platte River valley eroded headward across southeast oriented flood flow. Shallow northwest to southeast oriented through valleys can be seen along the South Platte River valley rim, although these through valleys are defined by only one 10-meter contour line on a side. The northeast oriented Wildhorse and North Fork Frenchman Creek headwaters drainage routes were probably created as shallow northeast oriented valleys eroded headward to capture the southeast oriented flood flow prior to headward erosion of the much deeper South Platte River valley.

Detailed map of South Platte River-Wildhorse Creek south drainage divide area

Figure 8: Detailed map of South Platte River-Wildhorse 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 South Platte River-Wildhorse Creek drainage divide area seen is less detail in figure 7. The map contour interval for figure 8 is 10 feet with dotted contour lines at 5-foot intervals. Fleming, Colorado is the town near the east edge of figure 8. The rim of the South Platte River southeast valley wall extends from near the southwest corner of figure 8 to near the northeast corner of figure 8 and north and northwest oriented valleys north of the valley wall rim drain to the northeast oriented South Platte River. Wildhorse Creek originates in section 11 (in west half of figure 8) and flows in a southeast direction to the northeast corner of section 13 and then turns in an east direction to flow to the northwest corner of section 16 where it turns in a north and east direction to flow to the east edge of figure 8 (on south side of Fleming). East of figure 8 Wildhorse Creek flows in an east, east-northeast, and east-southeast direction with water eventually reaching east-southeast oriented Frenchman Creek, which flows to the east oriented Republican River. Figure 8 illustrates shallow northwest-to-southeast oriented through valleys linking north-northwest oriented South Platte River tributary valleys with southeast oriented Wildhorse Creek headwaters valleys. One through valley is located in the southeast quadrant of section 10 and links the southeast oriented Wildhorse Creek headwaters valley with a north-northwest and north oriented South Platte River tributary valley. The through valley floor elevation is between 4330 and 4340 feet. Elevations north of the through valley rise to more than 4380 feet while elevations south of the through valley and seen in figure 8 rise to more than 4370 feet (and just south of figure 8 to more than 4380 feet). These elevations suggest the through valley is at least 40 feet deep. This 40-foot deep through valley was eroded by southeast oriented flood flow moving to the Wildhorse Creek valley prior to headward erosion of the much deeper South Platte River valley. The railroad in section 1 is located in a through valley linking northwest oriented headwaters of a north-northwest oriented South Platte River tributary with east oriented headwaters of an adjacent north-northwest oriented South Platte River tributary. This section 1 through valley is approximately 50 feet deep and illustrates have the much deeper northeast oriented South Platte River eroded headward across southeast oriented flood flow. Headward erosion of the South Platte River valley beheaded southeast oriented flood flow routes in sequence from east to west. Floodwaters on northwest ends of beheaded flood flow channels reversed flow direction to create northwest, north-northwest, or north oriented South Platte River tributary drainage routes. Because flood flow routes diverged and converged floodwaters on a newly beheaded and reversed flood flow channel could capture floodwaters from an adjacent yet to be beheaded flood flow channel. The section 1 through valley (now used by the railroad) was eroded by such captured floodwaters moving in an east direction from a yet to be beheaded flood flow channel in section 34 to a newly beheaded and reversed flood flow channel eroding the north-northwest oriented South Platte River tributary valley in section 36.

South Platte River-Sandy Creek drainage divide area

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

Figure 9 illustrates the South Platte River-Sandy Creek drainage divide area south and west of figure 7 and there is an overlap area with figure 7. The map contour interval for figure 9 is 10 meters. Sterling, Colorado is the town in the northwest corner of figure 9. The South Platte River flows in a north-northeast direction across the northwest corner of figure 9. The rim of the South Platte River east valley wall extends in a north-northeast direction from the south center edge of figure 9 to the north edge of figure 9 (east half). The North Fork Frenchman Creek originates along that east valley rim between North and South Reiradon Hills (in northeast quadrant of figure 9) and flows in an east, northeast, southeast, and northeast direction to the east edge of figure 9 (near northeast corner). East and north of figure 9 the North Fork Frenchman Creek turns to flow in an east direction and eventually joins the South Fork to form east-southeast oriented Frenchman Creek, which flows to the east oriented Republican River. East oriented streams flowing to the east edge of figure 9 (and south of the North Fork Frenchman Creek) flow to east oriented Sandy Creek, which flows towards east-southeast oriented Frenchman Creek, but which disappears as a surface stream before reaching Frenchman Creek. Southeast oriented streams flowing to the south edge of figure 9 (east half) are headwaters of southeast and south-southeast oriented Coyote Creek, which joins east oriented Rock Creek, which then also disappears as a surface stream. Northwest and north oriented streams can be seen draining the South Platte River east valley wall. Many of these streams do not reach the South Platte River and are lost in a region of what appear to be sand dunes on the east side of the South Platte River. Also northwest to southeast oriented erosional residuals and shallow through valleys are located along the east valley wall rim. These erosional residuals and through valleys provide additional evidence the South Platte River valley eroded headward across southeast oriented flood flow. Southeast oriented Coyote Creek headwaters valleys were eroded by southeast oriented flood flow prior to headward erosion of the South Platte River valley while the northeast oriented North Fork Frenchman Creek valley and the east oriented Sandy Creek headwaters valley probably eroded headward across the southeast oriented flood flow.

Detailed map of South Platte River-Coyote Creek drainage divide area

Figure 10: Detailed map of South Platte River-Coyote 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 South Platte River-Coyote Creek drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 10 feet. The rim of the South Platte River east valley wall extends in a northeast direction from Eagle Point Hill (near southwest corner of figure 10) to the north edge of figure 10 (east of center). North-northwest and northwest oriented streams flowing to the north edge of figure 10 flow towards the South Platte River, but disappear in what are probably sand dunes before reaching the river. Coyote Creek flows in a south-southeast direction across section 2 to the south edge of figure 10 in section 12 (near southeast corner of figure 10). South and east of figure 10 Coyote Creek flows in a southeast and south-southeast direction to join east oriented Rock Creek, which then disappears as a surface stream. The east oriented stream in sections 9 and 10 near the south edge of figure 10 is a Coyote Creek tributary. A northwest to southeast oriented erosional residual is located on the line between sections 34 and 35 and is also on the South Platte River east valley rim. Elevations on that erosional residual reach 4639 feet. Eagle Point Hill near the southwest corner of figure 10 reaches 4608 feet. Between the erosional residual and Eagle Point Hill elevations along the South Platte River east valley rim are lower with lowest elevations being between 4560 and 4570 feet. These elevations suggest there is a 30-40 foot deep northwest to southeast oriented through valley crossing the valley rim between the erosional residual and Eagle Point Hill and linking north and northwest oriented South Platte River tributary valleys with the south-southeast and southeast oriented Coyote Creek valley. This through valley was eroded by southeast oriented flood flow prior to headward erosion of the much deeper north-northeast oriented South Platte 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.