Tarryall Creek-South Platte River drainage divide area landform origins in Park County, Colorado, USA

Authors

 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the Tarryall Creek-South Platte River drainage divide area in Park County, Colorado. Hoosier Pass crosses the east-west continental divide and links the north oriented Blue River valley with the south and south-southeast oriented Middle Fork South Platte River valley, which drains in a south and south-southeast direction to join the South Fork South Platte River and to form the southeast oriented South Platte River, which at the southeast end of Elevenmile Canyon Reservoir makes an abrupt turn to flow in a northeast direction through Elevenmile Canyon (a 300-meter deep valley crossing the Puma Hills) and then turns to flow in a north-northeast direction. Tarryall Creek originates along the continental divide a short distance east of Hoosier Pass and flows in a southeast direction before turning in an east-northeast direction to join the north-northeast oriented South Platte River at the northeast end of Elevenmile Canyon. Several southeast oriented streams join the northeast oriented South Platte River in Elevenmile Canyon as barbed tributaries. Through valleys crossing drainage divides near the Tarryall Creek and Middle Fork South Platte River headwaters, in the South Park basin, and in the Puma Hills provide evidence of what were once diverging and converging south and southeast oriented flood flow channels prior to headward erosion of the southeast oriented Tarryall Creek valley. Floodwaters were derived from the western margin of a thick North American ice sheet and flowed from western Canada to and across Colorado at a time when Colorado mountain ranges were beginning to emerge. Prior to a reversal of flood flow on the present day north oriented South Platte River alignment floodwaters flowed to what at that time was the newly eroded southeast oriented Arkansas River valley with early versions (at much higher elevations than today) of the southeast oriented South Platte River and other southeast oriented valleys eroding headward from the Arkansas River valley. South and southeast oriented flood flow at one time flowed across the Puma Hills and later probably deeply eroded the South Park basin surface west of the Puma Hills, although crustal warping may have also changed regional topography. Headward erosion of the northeast oriented Elevenmile Canyon valley captured southeast oriented flood flow crossing the Puma Hills. Headward erosion of the southeast oriented Tarryall Creek valley and tributary valleys captured south oriented flood flow west of the Puma Hills. Headward erosion of the deep southeast and northeast oriented South Platte River valley into northeast Colorado from western Nebraska beheaded and reversed south oriented flood flow channels to create the north-northeast oriented South Platte River drainage route. Headward erosion of the deep southwest oriented Colorado River valley west of the present day east-west continental divide beheaded and reversed south oriented flood flow to the Tarryall Creek and Middle Fork South Platte River headwaters to create the north oriented Blue River drainage route. These flood flow captures and reversals were probably greatly aided by ice sheet related crustal warping that was occurring as floodwaters flowed across the region.

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 Tarryall Creek-South Platte River drainage divide area landform origins in Park County, Colorado. 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 Tarryall Creek-South Platte River drainage divide area landform evidence in Park County, Colorado will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Tarryall Creek-South Platte River drainage divide area location map

Fig1 locmap

Figure 1: Tarryall Creek-South Platte 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 Tarryall Creek-South Platte River drainage divide area Park County, Colorado and illustrates a region in central Colorado. Denver is located near the northeast corner of figure 1. Alma is located near the center of figure 1. The Middle Fork South Platte River originates north of Alma and then flows in a south and southeast direction near Alma and Fairplay to join the South Fork South Platte River (flowing from Antero Reservoir) at Hartsel to form the southeast oriented South Platte River, which then flows to Elevenmile Canyon Reservoir. At the southeast end of Elevenmile Canyon Reservoir the South Platte River makes an abrupt turn to flow in a northeast and north-northeast direction to Denver and the north edge of figure 1 (near northeast corner). North and east of figure 1 the South Platte River flows in a north and northeast direction before making another abrupt turn in northeast Colorado to flow in a southeast direction before turning again to flow in a northeast direction into western Nebraska with water eventually reaching the Gulf of Mexico. The unlabeled southeast oriented South Platte River tributary originating north of the Middle Fork South Platte River headwaters area near Alma and flowing near Bison Peak is Tarryall Creek. The Colorado River flows in a southwest direction across the northwest corner of figure 1 with water eventually reaching the Pacific Ocean. The Blue River originates north of Alma (and north of the Middle Fork South Platte River headwaters and west or the Tarryall Creek headwaters) and flows in a north and north-northwest direction to the north edge of figure 1 (west of center). North of figure 1 the Blue River flows to the southwest oriented Colorado River. Tennessee Pass is located west of Alma. The south-southeast oriented river originating near Tennessee Pass and flowing to Buena Vista and the south center edge of figure 1 is the Arkansas River. South of figure 1 the Arkansas River flows in more of a southeast direction with water eventually reaching the Gulf of Mexico. The Tarryall Creek-South Platte River drainage divide area investigated in this essay is south of Tarryall Creek, north of the south-southeast oriented Middle Fork South Platte River and the southeast oriented South Platte River, and west of the north-northeast oriented South Platte River between Elevenmile Canyon Reservoir and Tarryall Creek, and includes much of the region known as South Park.

Drainage routes in Colorado developed during immense melt water floods from the western margin of a thick North American ice sheet at a time when Colorado mountain ranges were beginning to emerge. Floodwaters flowed from the western Canada to and across Colorado as the regional mountain ranges emerged. Colorado mountain ranges emerged as floodwaters flowed across them, as ice sheet related crustal warping raised the entire state of Colorado and the region mountain masses, and as deep valleys eroded headward into Colorado from both the Gulf of Mexico and the Pacific Ocean. Initially floodwaters flowed in south directions across Colorado, but flood flow directions were changed as crustal warping raised the region and mountain masses in the region and flow directions were even reversed as deep valleys beheaded south oriented flood flow channels causing floodwaters on north ends of beheaded flood flow channels to reverse their flow direction. The north-northeast oriented South Platte River drainage route seen in figure 1 originated as south oriented flood flow channels probably flowing to what at that time was the newly eroded southeast oriented Arkansas River valley. Southeast oriented valleys eroded headward from these south oriented flood flow channels to capture south oriented flood flow in the emerging mountain region further to the west. Headward erosion of a deep southeast and northeast oriented South Platte River valley from western Nebraska into northeast Colorado (north of figure 1) beheaded and reversed the south oriented flood flow on the present day north oriented South Platte River alignment to create the north-northeast oriented South Platte River drainage route seen in figure 1. The reversal of flood flow on the South Platte River alignment also captured flow from the southeast oriented valleys that had eroded headward into the emerging mountains further to the west. At approximately the same time the deep southwest oriented Colorado River valley eroded headward into the emerging mountains and beheaded and reversed south oriented flood flow to the present Tarryall Creek and Middle Fork South Platte River valleys and created the north and north-northwest oriented Blue River drainage route. These flood flow captures and reversals probably were greatly aided by crustal warping that was raising Colorado and the Colorado mountains as floodwaters flowed across the region.

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

Fig2 detlocmap

Figure 2: Detailed location map of Tarryall Creek-South Platte River 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 Tarryall Creek-South Platte River drainage divide area in Park County, Colorado. Green colored areas are National Forest lands, which are primarily located in mountain regions surrounding the South Park basin area. The Middle Fork South Platte River flows from near the northwest corner of figure 2 in a south direction to Alma and then turns in a south-southeast direction to Fairplay, Garo, and Hartsel. At Hartsel the Middle Fork joins the South Fork (flowing from Antero Reservoir) to form the southeast oriented South Platte River, which flows to Elevenmile Canyon Reservoir. At the south end of Elevenmile Canyon Reservoir the South Platte River makes an abrupt turn to flow in a north-northeast direction to the northeast corner of figure 2. Red Hill is located east of Fairplay and Trout Creek flows in a southeast, south, and south-southeast direction on the east side of Red Hill to join the Middle Fork South Platte River near Garo. Reinecker Ridge is located east of Trout Creek and Bald Hill is located east of Garo. Further east Chase Gulch is a southeast and south-southeast oriented tributary joining the South Platte River near the west end of Elevenmile Canyon Reservoir. Sulphur Mountain is located on the west side of Chase Gulch just west of the town of Glentvar. Tarryall Creek originates near the north edge of figure 2 (east of the Middle Fork South Platte River headwaters) and flows in a southeast direction just north of Como before turning in an east and southeast direction to the Tarryall Reservoir State Recreation Area and then in a southeast direction before making a turn to flow in an east-northeast direction to join the north-northeast oriented South Platte River. North and east of Tarryall Creek are the Tarryall Mountains. Ruby Gulch is an east and north-northeast oriented tributary joining Tarryall Creek near the Tarryall Reservoir. With the exception of the north-northeast oriented South Platte River segment almost all other drainage routes seen in figure 2 flow in southeast directions and join the north-northeast oriented South Platte River as barbed tributaries. The southeast orientation of these drainage routes is evidence of south oriented and southeast oriented flood flow channels crossing the region prior to the reversal of flood flow that created the north-northeast South Platte River drainage route.

Tarryall Creek-Trout Creek drainage divide area

Fig3 TarryallTrout

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

Figure 3 provides a topographic map of Tarryall Creek-Trout Creek drainage divide area. The map contour interval for figure 3 is 50 meters. The Summit-Park County line in the northwest corner of figure 3 follows the east-west continental divide. Hoosier Pass crosses the continental divide near the northwest corner of figure 3. North oriented drainage on the north side of Hoosier Pass flows to the north and north-northwest oriented Blue River, which flows to the southwest oriented Colorado River as a barbed tributary. Montgomery Reservoir is located on the south side of Hoosier Pass. The Middle Fork South Platte River flows in a south direction from Montgomery Reservoir to Alma and then to the south edge of figure 2. South of figure 2 the Middle Fork turns in a south-southeast direction to join the South Fork and to form the southeast and north-northeast oriented South Platte River. Mount Silverheels is located in the northwest quadrant of figure 3 and east of the Middle Fork South Platte River. Tarryall Creek originates on the north side of Mount Silverheels and flows in a northeast direction before turning to flow in a southeast direction to the east center edge of figure 3. East of figure 3 Tarryall Creek flows to the north-northeast oriented South Platte River. Trout Creek originates on the east side of Mount Silverheels and flows in a southeast, south, and southeast direction to the south side of Little Baldy Mountain and then turns to flow in a south direction to the south center edge of figure 3. Red Hill is the north-to-south oriented ridge located west of Trout Creek and Reinecker Ridge is east of Trout Creek. Hoosier Pass has an elevation of 3517 meters. The south oriented stream originating on the west side of Mount Silverheels is Beaver Creek, which joins the Middle Fork South Platte River south of figure 3. Beaver Ridge is located between Beaver Creek and the south oriented Middle Fork South Platte River valley. Elevations on the continental divide east of Hoosier Pass exceed 4050 meters and west of Hoosier Pass (and of figure 3) elevations exceed 4100 meters suggesting Hoosier Pass is at least 500 meters deep. Hoosier Pass was eroded by south oriented flood flow moving from the present day north oriented Blue River alignment to the south oriented Middle Fork South Platte River valley. Headward erosion of the deep southwest oriented Colorado River valley north of figure 3 beheaded and reversed the south oriented flood flow channel to create the north oriented Blue River drainage route and the east-west continental divide. Passes north of figure 3 link the southeast oriented Tarryall Creek valley with northwest oriented Blue River tributary valleys. Other unlabeled passes seen in figure 3 link the northeast oriented Tarryall Creek headwaters valley with the south oriented Beaver Creek valley and a northeast oriented Tarryall Creek tributary valley with the south oriented Trout Creek valley. The Tarryall Creek-Beaver Creek pass is at least 350 meters deep and Tarryall Creek-Trout Creek pass is at least 300 meters deep. These unlabeled passes are all water-eroded features and were eroded by south oriented flood flow prior to headward erosion of the much deeper southeast oriented Tarryall Creek valley and its northeast oriented headwaters valley.

Detailed map of South Tarryall Creek-Trout Creek drainage divide area

Fig4 detSTarryallTrout

Figure 4: Detailed map of South Tarryall Creek-Trout 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 Tarryall Creek-Trout Creek drainage divide area seen in less detail in figure 5. The map contour interval for figure 4 is 40 feet. Little Baldy Mountain is located in section 25 in the east half of figure 4 and reaches an elevation of 12,142 feet. Mount Silverheels is located in section 21 in the northwest quadrant of figure 4 and reaches an elevation of 13,822 feet. Tarryall Creek flows in a southeast direction across the northeast corner of figure 4. East of figure 4 Tarryall Creek flows primarily in a southeast direction to join the north-northeast oriented South Platte River as a barbed tributary. South Tarryall Creek originates in section 23 (in north center area of figure 4) and flows in a southeast and then northeast direction to join Tarryall Creek. Silverheels Creek flows in an east direction near the east center edge of figure 4 to join Tarryall Creek. Trout Creek originates on the west side of Mount Silverheels and flows in a southeast direction into section 26 and then turns to flow in a south and southeast direction to the south edge of figure 4 (east of center). South of figure 4 Trout Creek flows primarily in a south direction to join the south-southeast oriented Middle Fork South Platte River, which then flows to the southeast and north-northeast oriented South Platte River. A through valley or pass in the northeast corner of section 26 links the southeast and northeast oriented South Tarryall Creek valley with the south oriented Trout Creek valley. The through valley or pass elevation is between 11,120 and 11,160 feet suggesting the through valley or pass is approximately 1000 feet deep. The through valley was eroded by south oriented flood flow prior to headward erosion of the much deeper southeast oriented Tarryall Creek valley and its northeast oriented South Tarryall Creek tributary valley. A less obvious through valley (or pass) in section 23 links the south oriented South Tarryall Creek valley with the east oriented Silverheels Creek valley to the north. This section 23 through valley or pass is at least 80 feet deep and was eroded by south oriented flood flow moving to the newly eroded South Tarryall Creek valley prior to headward erosion of the east oriented Silverheels Creek valley.

Tarryall Creek-Ruby Gulch drainage divide area

Fig5 TarryallRubyGulch

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

Figure 5 illustrates the Tarryall Creek-Ruby Gulch drainage divide area south and east of figure 3 and there is an overlap area with figure 3. The map contour interval for figure 5 is 50 meters. Tarryall Creek flows in an east-southeast and south-southeast direction from the north edge of figure 5 (east of center) to the east center edge of figure 5. East of figure 5 Tarryall Creek flows in a southeast and east-northeast direction to join the north-northeast South Platte River. Ruby Gulch originates a short distance north of the south center edge of figure 5 and drains in an east and north-northeast direction to join Tarryall Creek near the east center edge of figure 5. Early Gulch is an east and east-southeast tributary originating north of the east oriented Ruby Gulch headwaters and draining to the north-northeast oriented Ruby Gulch segment. Park Gulch is a southeast, northeast, and east-northeast oriented drainage route draining from the north edge of figure 5 (west half) to join Tarryall Creek near the north edge of figure 5. Indian Gulch is a north oriented Park Gulch tributary originating near the center of figure 5 (north of the Early Gulch headwaters). North-to-south oriented linear ridges in the west half of figure 5 link the Park Gulch drainage system with south oriented valleys draining to the south-southeast oriented Middle Fork South Platte River (located south of figure 5). The linear ridges appear to be hogback ridges and the valley orientations in that region are determined by the underlying geologic structures. However the north-to-south oriented valleys between the linear ridges are water-eroded valleys and were eroded by diverging and converging south oriented flood flow channels prior to headward erosion of the Park Gulch valley and its tributary valleys from the actively eroding Tarryall Creek valley. Hills in the Indian Gulch and Early Gulch region are not linear and do not appear to be determining valley orientations. A north-to-south oriented through valley links the north oriented Indian Gulch valley with the east and east-southeast oriented Early Gulch valley. The through valley is at least 50 meters deep and was eroded by south oriented flood flow prior to headward erosion of the east-northeast oriented Park Gulch valley. Headward erosion of the east-northeast oriented Park Gulch valley beheaded the south oriented flood flow channel and floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented Indian Gulch drainage route.

Detailed map of Indian Gulch-Early Gulch drainage divide area

Fig6 detIndianGlEarlyGl

Figure 6: Detailed map of Indian Gulch-Early Gulch 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 Indian Gulch-Early Gulch drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 20 feet. Indian Gulch originates in section 28 (in northwest quadrant of figure 6) and drains in a northeast direction to the north edge of figure 6 (west of center). North of figure 6 Indian Gulch drains in a north direction to join east-northeast oriented Park Gulch, which drains to southeast oriented Tarryall Creek. Early Gulch originates in section 4 (in southwest quadrant of figure 6) and drains in an east and east-southeast direction to near the southeast corner of figure 6. South and east of figure 6 Early Gulch drains to north-northeast oriented Ruby Gulch, which drains to southeast oriented Tarryall Creek. Three closely spaced and roughly parallel north-to-south oriented through valleys in section 34 (in center of figure 6) link the north oriented Indian Gulch valley with the east-southeast oriented Early Gulch valley. The through valleys have floor elevations of between 9680 and 9700 feet. Elevations in the southwest corner of section 33 to the west exceed 10,020 feet and elevations in section 36 to the east exceed 10,200 feet. These elevations suggest the through valleys are approximately 300 feet deep. The through valleys were eroded by diverging and converging south oriented flood flow channels prior to headward erosion of the east-northeast oriented Park Gulch valley north of figure 6. Floodwaters were flowing to what at that time was the newly eroded east-southeast oriented Early Gulch valley. Headward erosion of the east-northeast oriented Park Gulch valley north of figure 6 (from what at that time was the actively eroding southeast oriented Tarryall Creek valley) beheaded and reversed the south oriented flood flow channels to create the north oriented Indian Gulch drainage route. Shallow west-to-east oriented through valleys west of the Early Gulch headwaters and also west of the Indian Gulch headwaters were probably eroded by east oriented flood flow from west of figure 6 moving to the actively eroding Early Gulch and Indian Gulch valleys. Today the region west of figure 6 is lower in elevation and is the floor of a north-to-south oriented through valley seen in figure 5. Headward erosion of that north-to-south oriented through valley west of figure 6 beheaded the east oriented flood flow channels to the actively eroding Early Gulch and Indian Gulch valleys.

Ruby Gulch-Chase Gulch drainage divide area

Fig7 RubyGlChaseGl

Figure 7: Ruby Gulch-Chase Gulch drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 provides a topographic map of the Ruby Gulch-Chase Gulch drainage divide area south and east of figure 5 and includes overlap area with figure 5. The map contour interval for figure 7 is 50 meters. The Puma Hills are located in the east half of figure 7. Tarryall Creek flows in a southeast direction across the northeast corner of figure 7. East of figure 7 Tarryall Creek turns in an east-northeast direction to join the north-northeast oriented South Platte River. Ruby Gulch drains in an east and then north-northeast direction from near the northwest corner of figure 7 to the north edge of figure 7 (west of center). North of figure 7 Ruby Gulch joins southeast oriented Tarryall Creek. Logan Hill is a labeled high point near the northwest corner of figure 7. Chase Gulch originates north of Logan Hill and drains in a south-southeast direction to the south center edge of figure 7. South of figure 7 Chase Gulch drains to the southeast oriented South Platte River, which after flowing to Elevenmile Canyon turns to flow in a north-northeast direction. A broad north-to-south oriented through valley west of the Puma Hills links the southeast oriented Tarryall Creek valley with the southeast oriented South Platte River valley. The through valley as seen in figure 7 is defined by three contour lines on the west side (many more contour lines are found further to the west near the continental divide) and was eroded by south-southeast oriented flood flow prior to headward erosion of the southeast oriented Tarryall Creek valley and its east and north-northeast oriented Ruby Gulch tributary valley. Interesting through valleys or passes can be seen in the Puma Hills region and provide evidence floodwaters once crossed the Puma Hills (before the broad through valley west of the Puma Hills was eroded). Marksbury Gulch is an east oriented drainage route draining to the east edge of figure 7 (south half) and then to southeast and east-northeast oriented Tarryall Creek. Thorpe Gulch is north of Marksbury Gulch and drains to the east center edge of figure 7 and then turns in a southeast direction to join east oriented Marksbury Gulch. Allen Creek is a northeast oriented Tarryall Creek tributary originating north of the Marksbury Gulch headwaters. A northwest-to-southeast oriented through valley or pass links the northeast oriented Allen Creek valley with the east oriented Thorpe Gulch and Marksbury Gulch valleys. The through valley or pass is defined by five contour lines on each side suggesting it is at least 200 meters deep. Following the through valley or pass alignment northward leads to high pass west of Farmun Peak and a north-northwest oriented Tarryall Creek tributary valley. Following the through valley or pass alignment southward leads to south oriented Martland Gulch, which drains to the southeast oriented South Platte River (via Chase Gulch). While the Puma Hills drainage history involved many flood flow captures at one time before those flood flow captures south oriented flood flow moved on an erosion surface equivalent in elevation to the elevation of the pass on the southwest side of Farmun Peak.

Detailed map of Ruby Gulch-Chase Gulch drainage divide area

Fig8 detRubyGlChaseGl

Figure 8: Detailed map of Ruby Gulch-Chase Gulch drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 provides a detailed map of the Ruby Gulch-Chase Gulch drainage divide area seen in less detail in figure 7. The map contour interval for figure 8 is 20 feet. Ruby Gulch drains in an east direction from near the northwest corner of figure 8 to near the northeast corner of figure 8 and east and north of figure 8 drains in a north-northeast direction to join southeast and east-northeast oriented Tarryall Creek, which joins the north-northeast oriented South Platte River. An east oriented Ruby Gulch tributary originates near the north edge of section 25 and drains in an east direction to the east center edge of figure 8. East of figure 8 the tributary turns in a north direction to drain to Ruby Gulch. Chase Gulch originates in section 22 and drains in a northeast and southeast direction near the Elkhorn Community House before turning to drain in a southeast and south direction to the south edge of figure 8 (east of center). South of figure 8 Chase Gulch drains in a south-southeast direction to join the southeast oriented South Platte River, which at Elevenmile Canyon turns to flow in a northeast and then north-northeast direction. A northwest-to-southeast oriented through valley in section 22 links the east oriented Ruby Gulch valley with the southeast and south oriented Chase Gulch valley. The through valley floor elevation at the drainage divide is between 9480 and 9500 feet. The hill on the northeast side rises to 9695 feet and the hill to the southwest rises to 9921 feet suggesting the through valley is approximately 200 feet deep. A west-to-east oriented through valley in section 25 links the southeast and south oriented Chase Gulch valley with the east and north oriented Ruby Gulch tributary valley. The through valley floor elevation is between 9300 and 9320 feet. Elevations just south of the through valley rise to 9443 feet and elevations north of the through valley rise to more than 9500 feet suggesting the through valley is at least 123 feet deep. The through valleys were eroded by diverging and converging flood flow channels as headward erosion of the east and north-northeast oriented Ruby Gulch valley captured southeast and south-southeast oriented flood flow moving to the south-southeast oriented Chase Gulch valley. Diverging and converging flood flow channels such as those seen in figure 8 are typically eroded as large floods cross a region.

Martland Gulch-Pulver Gulch drainage divide area

Fig9 MartlandGlPulverGl

Figure 9: Martland Gulch-Pulver Gulch drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 provides a topographic map of the Martland Gulch-Pulver Gulch drainage divide area east and south of figure 7 and includes overlap areas with figures 7. The map contour interval for figure 9 is 50 meters. The South Platte River flows in a southeast direction from the west center edge of figure 9 to Elevenmile Canyon Reservoir and near the south center edge of figure 9 turns to flow in a northeast and then north-northeast direction to the northeast corner of figure 9. North of figure 9 the South Platte River flows in a north-northeast and north direction into northeast Colorado where it turns in a southeast and then northeast direction to flow into western Nebraska. Elevenmile Canyon, where the northeast oriented South Platte River crosses the Puma Hills, is approximately 300 meters deep at its deepest points. While not seen in figure 9 a southeast oriented through valley extends from the Elevenmile Reservoir southeast end to the headwaters of a southeast and south oriented tributary valley draining to the southeast oriented Arkansas River and provides evidence that the southeast oriented South Platte River segment once flowed to the Arkansas River valley. The through valley floor elevation is approximately 300 meters higher than the South Platte River elevation in Elevenmile Canyon. Chase Gulch drains in a southeast and southeast direction from the west edge of figure 9 (north half) to join the southeast oriented South Platte River (upstream from Elevenmile Canyon Reservoir). Martland Gulch is a south-southwest oriented Chase Gulch tributary draining from the north edge of figure 9 (west half). Pulver Gulch originates at deep pass where the highway crosses the Puma Hills (near north center edge of figure 9) and drains in a southeast and east-southeast direction to join the north-northeast oriented South Platte River near Lake George. Several shorter southeast oriented tributaries flow to the northeast oriented South Platte River in Elevenmile Canyon as barbed tributaries including Messenger Gulch and Rocky Gulch. These barbed tributaries and the South Platte River elbow of capture provide evidence the northeast oriented Elevenmile Canyon valley was eroded headward across multiple southeast oriented flood flow channels, which at one time had to be flowing on an erosion surface at least 300 meters higher than the present day floor of Elevenmile Canyon. Headward erosion of the northeast oriented Elevenmile Canyon valley probably occurred at the time floodwaters on the present day north oriented South Platte River drainage route north of Lake George were beheaded and reversed to create the north-northeast oriented South Platte River drainage route extending from Lake George to near Greeley (north of Denver). This massive flood flow reversal was triggered by headward erosion of a deep southeast and northeast oriented South Platte River valley into northeast Colorado from western Nebraska, but was probably greatly aided by ice sheet related crustal warping that was raising elevations at the south end of the present day north oriented South Platte River drainage route.

Detailed map of Martland Gulch-Pulver Gulch drainage divide area

Fig10 detMartlandGlPulverGl

Figure 10: Detailed map of Martland Gulch-Pulver Gulch 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 Martland Gulch-Pulver Gulch drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 40 feet. Badger Mountain is located in section 35 and reaches an elevation of 11,294 feet. Pulver Mountain (just south of the southeast quadrant of figure 10) reaches an elevation of 10,538 feet. Wilkerson Pass is located in the through valley between Badger Mountain and Pulver Mountain in section 2 and has an elevation of 9502 feet and is approximately 1000 feet deep. Pulver Gulch originates on the east side of Wilkerson Pass and drains in a southeast direction to the east edge of figure 10 (south half). East and south of figure 10 Pulver Gulch drains to the north-northeast oriented South Platte River. Martland Gulch drains in a south-southwest direction from the north edge of figure 10 (west half) to the west edge of figure 10 (south of center). West and south of figure 10 Martland Gulch drains to south-southeast oriented Chase Gulch, which drains to the southeast, northeast, and north-northeast oriented South Platte River. Wilkerson Pass is a deep northwest-to-southeast oriented through valley eroded across the Puma Hills and was eroded by a southeast oriented flood flow channel flowing in the same direction as the southeast oriented flood flow channel responsible for eroding the deeper southeast oriented South Platte River valley to the south of figure 10. Southeast oriented flood flow flowing through the Wilkerson Pass was beheaded by headward erosion of the deeper south-southeast Chase Gulch valley and its tributary valleys from the southeast oriented South Platte River valley to the south of figure 10. While the beheading can be explained by deep erosion of the region west of Wilkerson Pass it is also possible crustal warping was raising the Puma Hills as floodwaters flowed through the Wilkerson Pass. If so the crustal warping may have contributed to the beheading of the southeast oriented flood flow route to the Pulver Gulch 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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