A geomorphic history based on topographic map evidence

The Niobrara River-North Loup River drainage divide area discussed here is located in northern Nebraska, USA. Although detailed topographic maps of the Niobrara River-North Loup River drainage divide area have been available for more than fifty years detailed map evidence has not previously been used to interpret the region’s geomorphic history. The interpretation provided here is based entirely on topographic map evidence. The Niobrara River-North Loup River drainage divide area is interpreted to have been eroded during immense southeast-oriented flood events, the first of which flowed on a topographic surface at least as high as the highest points in the present-day drainage divide area. Flood waters probably deposited sediments from which Nebraska sand hills were developed. Flood erosion ended when headward erosion of the east-oriented Niobrara River valley captured all southeast-oriented flood flow.

Preface:

The following interpretation of detailed topographic map evidence is provided as evidence in the Missouri River drainage basin landform origins research project, which is compiling similar evidence for all major drainage divides contained within the Missouri River drainage basin and for all major drainage divides with and within certain adjacent drainage basins. The research project is interpreting evidence in the context of a previously unexplored geomorphology paradigm, which is briefly described in the introduction below. 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 Nebraska Niobrara River-North Loup River drainage divide area landform origins. 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 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 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 similar essays is a thick North American ice sheet, comparable in thickness to the present day Antarctic ice sheet, occupied approximately the North American region usually recognized to have been glaciated and through its weight and erosive actions created a “deep” North American “hole”, 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 Nebraska Niobrara River-North Loup River drainage divide area landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Niobrara River-North Loup River drainage divide area general location map

Figure 1: Niobrara River-North Loup River drainage divide area general 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 general location map for the Niobrara River-North Loup River drainage divide area. The state of Nebraska is located south of the yellow boundary line and the state of South Dakota is north of the red boundary line. The Niobrara River flows in an easterly direction across northern Nebraska. Labeled Niobrara tributaries in the Niobrara River-North Loup drainage divide area include Snake River and Gordon Creek. The North Loup River originates south of Gordon Creek and flows generally in a southeast direction to the figure 1 southeast quadrant. The Calamus River is a major North Loup River tributary which originates near Moon Lake and flows southeast to join the North Loup River near Burwell, Nebraska. Much of the Niobrara River-North Loup River drainage divide area is located in the Nebraska Sand Hills region. The Sand Hills are stabilized sand dunes that post date the region’s major drainage system evolution. Sand dunes obscure much of the topographic map evidence required to interpret the region’s drainage history and this essay relies on what limited evidence is available. Landform evidence illustrated in this essay is interpreted in the context of an immense southeast-oriented flood flowing across the entire figure 1 map area and which was systematically captured and diverted east and perhaps even northeast by headward erosion of deep valleys eroded into a topographic surface at least as high as the figure 1 region highest elevations today. In the figure 1 map region headward erosion of the North Loup River valley first captured the southeast-oriented flood flow and then the southeast-oriented Calamus River valley eroded headward along a southeast-oriented flood flow route as a tributary to the actively eroding southeast-oriented North Loup River valley. Headward erosion of the much deeper east-oriented Niobrara River valley and its various tributary valleys captured southeast-oriented flood flow moving to what were then the actively eroding and newly eroded southeast-oriented North Loup River and Calamus River valleys. Detailed maps provide evidence supporting this interpretation. Evidence of southeast-oriented flood flow in adjacent regions is described in essays under Niobrara River on the sidebar category list and also under White River, which is the major east-oriented drainage basin immediately to the north of the Niobrara River drainage basin.

Niobrara River-North Loup River drainage divide area detailed location map

Figure 2: Niobrara River-North Loup River drainage divide area detailed location map. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 2 provides a detailed location map for the Niobrara River-North Loup River drainage divide area. Cherry, Brown and Keya Paha Counties are located in Nebraska. The Niobrara River flows east, southeast, and northeast across northern Cherry County and then turns southeast to form the boundary between Keya Paha County and Brown County. The North Loup River originates in western Cherry County and flows southeast to the southeast Cherry County corner area and then southeast to the figure 2 south edge. The Calamus River originates in Brown County and flows southeast to the Brown County southeast corner. Note how there are other southeast-oriented streams or streams with southeast-oriented valley segments located throughout the figure 2 region. These parallel southeast-oriented valleys were probably initiated as interconnected channels in a large southeast-oriented anastomosing channel complex, evidence of which is further discussed in the Niobrara River-Elkhorn River drainage divide area essay describing landform evolution in the region immediately to the east. Sand dune regions cover much of the figure 2 map area and the best evidence for determining regional drainage history is found in northern Brown County and northeastern Cherry County where northeast-oriented Niobrara River tributaries have captured southeast-oriented streams. These captures suggest the northeast-oriented Niobrara River tributaries eroded southwest from what was an actively eroding Niobrara River valley head to capture yet to be beheaded (by headward erosion of the Niobrara River valley) multiple southeast-oriented flood flow routes, such as might be found in a southeast-oriented anastomosing channel complex. Other evidence is located in the Nebraska National Forest area where the Snake River and Gordon Creek valleys have eroded southwest to capture east-oriented flow. However, as detailed maps below illustrate this evidence, along with evidence in the North Loup River valley and in the Calamus River valley, is somewhat obscured by the presence of sand dunes and cannot be considered as conclusive as evidence in northern Brown County. While the sand dunes obscure some desired evidence, the dunes provide evidence large amounts of sand were deposited across the figure 2 map region. Further north in North Dakota and Manitoba for example, sand dune regions are developed on sandy deltas where large glacial melt water floods entered what are usually considered to have been large standing bodies of water (or lakes). Evidence presented here is not adequate to determine whether or not the Nebraska Sand Hills region originated as such a deltaic deposit, although evidence presented here and in other essays makes a strong case for immense southeast-oriented floods moving to and across the present day Nebraska Sand Hills region.

Niobrara River tributary valleys in Ainsworth and Long Pine area

Figure 3: Niobrara River tributary valleys in Ainsworth and Long Pine area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 3 illustrates north-oriented Niobrara River tributary valleys in the Ainsworth and Long Pine area of northern Brown County, Nebraska. Long Pine Creek is the north-oriented Niobrara River tributary flowing through Long Pine. Bone Creek flows northeast through Ainsworth and then north to the figure 3 north edge. Northeast and east-oriented Sand Draw flows in the figure 3 northwest quadrant to join Bone Creek in the figure 3 north center. Note how Long Pine Creek has a significant southeast-oriented headwaters valley segment in the figure 3 southeast quadrant and south of Long Pine and near the figure 3 north edge is flowing in northwest-oriented valleys. Also note northwest-oriented Spring Brook flowing to Long Pine Creek at its elbow of capture in the figure 3 southeast corner. This evidence suggests the north-oriented Long Pine Creek valley eroded south to capture southeast-oriented flood flow routes not yet been beheaded by headward erosion of the Niobrara River valley to the north. The northwest-oriented valley segments and the northwest-oriented tributary valley were eroded by reversed flow on the northwest ends of beheaded southeast-oriented flood flow routes. The southeast-oriented flood flow was probably moving in anastomosing (or interconnected channels), which meant reversed flow on a beheaded flood flow channel could frequently capture flood flow from yet to be beheaded flood flow channels further to the south and southwest. Such captures of yet to be beheaded flood flow often enable reversed flow channels to erode significant valleys. Headward erosion of the north-oriented Long Pine Creek valley proceeded headward erosion of the Bone Creek valley, which captured southeast-oriented flood flow moving to the newly eroded Long Pine Creek valley. Headward erosion of the Sand Draw valley then captured southeast-oriented flood flow moving to the newly eroded Bone Creek valley.

Detailed map of Sand Draw-Bone Creek drainage divide area

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

Figure 4 illustrates a detailed map of the Sand Draw-Bone Creek drainage divide area immediately southwest of where east-oriented Sand Draw enters north-oriented Bone Creek (and illustrates an area seen in less detail in figure 3 above). Note how tributary valleys to the east-oriented Sand Draw valley are southeast oriented. An unnamed Bone Creek tributary flows east across sections 31, 32 and 33 in the figure 4 southwest quadrant and joins Bone Creek in the southwest corner of section 34 in the figure 4 southeast quadrant. Note how tributary valleys to that east-oriented Bone Creek tributary valley are southeast oriented. Note also how the north-oriented Bone Creek valley has several northwest-oriented tributary valleys. This southeast and northwest orientation of tributary valleys provides evidence the north-oriented Bone Creek valley eroded headward across southeast-oriented flood flow and the northwest-oriented tributary valleys were eroded by reversals of flood flow on the northwest ends of beheaded flood flow routes. The unnamed east-oriented Bone Creek tributary valley then eroded west to capture southeast-oriented flood flow, which was subsequently captured by headward erosion of the Sand Draw valley further to north. The southeast-oriented tributary valleys to both the unnamed east-oriented tributary valley and the east-oriented Sand Draw valley were eroded by southeast-oriented flood flow routes carrying flood water into the newly eroded valleys. Northeast-oriented tributary valleys to the north-oriented Bone Creek valley and the east-oriented Sand Draw valley were eroded in sequence from east to west as the Sand Draw valley eroded headward to capture southeast-oriented flood flow that had not yet been captured by Sand Draw valley headward erosion. Flood flow to the figure 4 map area ceased as Plum Creek valley headward erosion to the north captured all southeast-oriented flood flow.

Plum Creek-Sand Draw drainage divide area in Johnstown-Ainsworth area

Figure 5: Plum Creek-Sand Draw drainage divide area in Johnstown-Ainsworth area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 5 illustrates the Plum Creek-Sand Draw drainage divide area in the Johnstown-Ainsworth, Nebraska area. Plum Creek is the major stream flowing from the figure 5 south edge to the figure 5 north edge. Note how near the south edge Plum Creek is northwest-oriented and then turns to become northeast-oriented, and in the figure 5 north center turns southeast before turning northeast again. Also note the predominance of northwest-oriented Plum Creek tributaries from the east and southeast oriented Plum Creek tributaries from the west. East of Plum Creek flowing past the Ainsworth municipal airport is northeast-oriented Sand Draw (seen in figures 3 and 4 above). Northeast and north oriented Bone Creek is present in the figure 5 southeast corner. The southeast and northwest-oriented Plum Creek tributaries provide evidence the Plum Creek valley eroded headward to capture multiple southeast-oriented flood flow routes. The southeast-oriented Plum Creek valley segment is evidence the Plum Creek valley eroded headward along one southeast-oriented flood flow route before eroding southwest to capture additional southeast-oriented flood flow channels. The northwest-oriented Plum Creek valley segment is evidence the Plum Creek valley eroded headward along a reversed flow route, that had developed when Plum Creek valley headward erosion beheaded a southeast-oriented flood flow route. The northwest-oriented Plum creek tributary valleys were eroded by reversed flood flow on the northwest ends of beheaded southeast-oriented flood flow routes. The sequence of drainage routes development recorded by the figure 5 evidence begins with headward erosion of the north and northeast-oriented Bone Creek valley. Subsequently the Sand Draw valley eroded west and southwest to capture southeast-oriented flood flow to the newly eroded Bone Creek valley. Next the Plum Creek valley eroded southwest, northwest, southwest, and southeast to capture southeast-oriented flood flow to the newly eroded Sand Draw valley. Finally headward erosion of the Niobrara River valley to the north of the figure 5 map area captured all southeast-oriented flood flow that had been moving to the figure 5 map area.

Detailed map of Sand Draw-Bone Creek tributary drainage divide

Figure 6: Detailed map of Sand Draw-Bone Creek tributary drainage divide. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 6 illustrates a detailed map of the drainage divide between northeast-oriented Sand Draw seen in figures 3 and 5 above and a southeast-oriented Bone Creek tributary, also seen in figures 3 and 5 above. Note how there is a northwest-southeast oriented through valley (or dry valley) linking the northeast-oriented Sand Draw valley with the southeast-oriented Bone Creek tributary valley. The through valley is evidence the northeast-oriented Sand Draw valley eroded headward across a southeast-oriented flood flow route to capture the southeast-oriented flood flow and to divert the water northeast and east to the Niobrara River valley. Through valleys such as this one permit drainage histories to be constructed. When constructing such drainage histories it is important to remember the through valleys were usually eroded by flood waters flowing in anastomosing channels. Consequently there are frequently multiple parallel through valleys, although not always at the same elevations. Anastomosing channel complexes are constantly changing as one of the interconnected flood flow channels erodes deeper and captures flood flow from other flood flow channels. The source of the flood waters moving across the Niobrara River-North Loup River drainage divide area cannot be determined from evidence presented here. However, using the larger Missouri River drainage basin landform origins research project essay collection (published on this website) the flood waters can be traced headward in a northwest direction across the Niobrara River, White River, Cheyenne River, and Powder River drainage basins into Montana and southern Alberta and Saskatchewan. Rapid melting of a thick North American ice sheet located in a deep “hole” occupying approximately the North America location usually recognized to have been glaciated would be a logical flood water source. Further, rapid melting of a thick North American ice sheet located in such a deep “hole” would explain why deep valleys eroded headward to capture southeast-oriented melt water floods and to divert the flood waters further and further northeast into space the ice sheet had once occupied.

Snake River elbow of capture area

Figure 7: Snake River elbow of capture area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 7 illustrates the Snake River elbow of capture area where the east oriented Snake River turns to flow northeast to the Niobrara River. The figure 7 map area is west of the previous figures and is located in the Nebraska National Forest area shown in figure 2. Figure 7 also illustrates the difficulty of interpreting drainage histories from evidence in sand dune covered areas. Figure 7 evidence is not adequate to determine whether the east oriented Snake River alignment (and also the east oriented Steer Creek alignment in the north of figure 7) originated prior to dune development or has developed as a result of dune orientations. It is possible the drainage pattern at least to some extent originated prior to sand dune formation. If so, the northeast-oriented Snake Creek valley eroded south to capture east or southeast oriented flood flow routes moving along what are today the Steer Creek and the Snake Creek east-oriented drainage routes. However, it is very probable the east-oriented Steer Creek and Snake River drainage routes reflect at least to some extent dune orientations, which probably reflect wind direction orientations, so figure 7 evidence is inconclusive in terms of deciphering drainage history. In spite of this difficulty the presence of a large sand dune area at a location crossed by an immense flood documented in the Missouri River drainage basin landform origins research project essays is evidence flood waters may have been temporarily ponded causing flood waters to deposit large amounts of sediment in a deltaic formation of some type. Central and western Nebraska was a region where immense floods moving southeast from central Montana and northeast Wyoming converged with immense floods moving east from central Wyoming and northeast from northeast Colorado and southeast Wyoming. The convergence of these immense floods may have resulted in the ponding of flood waters in Nebraska and the deposition of flood transported sediments that later developed into an extensive Nebraska sand dune region.

Gordon Creek-North Loup River drainage divide area

Figure 8 is a big picture view of the Gordon Creek-North Loup River drainage divide area south of the Snake River area illustrated in figure 7 above. The east and northeast-oriented Snake River is located in the figure 8 north. Gordon Creek is the east oriented stream flowing across the figure 8 center just north of Big Dry Valley and turning to flow northwest almost to join Snake Creek at Merritt Reservoir, but then turning northeast along the figure 8 east edge to flow independently to the Niobrara River (see figures 1 and 2). Between east oriented Snake River and east oriented Gordon Creek is east oriented Boardman Creek, which flows parallel to Gordon Creek across much of the figure 8 map area, but turns north and northeast to flow to the Snake River at Merritt Reservoir. The east and southeast-oriented stream along the figure 8 south edge is the North Loup River. Again the question can be raised as to whether the figure 8 drainage patterns are primarily a reflection of the dune orientations, which were determined by wind directions, or whether the drainage pattern reflects in some way the drainage pattern that existed prior to sand dune development. The drainage divide between adjacent and parallel Boardman Creek and Gordon Creek, which then diverge and flow in different ways to the Niobrara River suggests there is more to the drainage pattern than just the dune orientation. Apparently prior to dune development a northeast-oriented Gordon Creek valley eroded southwest to capture east or southeast-oriented flood water and subsequently headward erosion of a northeast-oriented Snake River valley from the Niobrara River valley to the north captured southeast-oriented flood flow in what is today at least some of the east-oriented Snake River and east-oriented Boardman Creek drainage area. While topographic map evidence alone does not permit conclusions to be drawn, the figure 8 evidence documents the presence of a large sand covered region, which would be consistent with sediments that might be deposited in a region where immense floods from several different directions converged and flood waters were temporarily ponded.

North Loup River in Wamaduza Valley area

Figure 9: North Loup River in Wamaduza Valley area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 9 illustrates with less reduction the southeast-oriented North Loup River east of the figure 8 map area and there is some overlap between figure 8 and figure 9. Note the southeast-oriented Wanaduza Valley and how it is aligned with the Big Dry Valley, which was located immediately south of east-oriented Gordon and Boardman Creeks. It is possible that prior to being captured by the northeast-oriented Gordon Creek valley and the northeast-oriented Snake River valley the east-oriented Gordon Creek valley and the east-oriented Boardman Creek valley (if they were two separate valleys and if they were east-oriented valleys at that time) continued east and southeast along the present day Big Dry Valley and Wanaduza Valley alignment to the North Loup River valley. If so the southeast-oriented orientation of those valleys would be consistent with the headward erosion of deep valleys northwest along southeast-oriented flood routes prior to Niobrara River valley headward erosion. Headward erosion of the deep Niobrara River valley to the north would have enabled the northeast-oriented Gordon Creek valley to erode southwest to capture southeast-oriented flood flow and subsequently the northeast-oriented Snake River valley to erode southwest to capture at least some of the same southeast-oriented flood flow routes. Northeast-oriented Niobrara River tributary systems illustrated in figures 3 and 5 above probably reflect what the northeast-oriented Gordon Creek and northeast-oriented Snake River valleys might have looked like prior to the dune development. Please remember this interpretation is based solely on topographic map evidence and well data and other ground data from the figure 9 region may provide significant additional information that could change the interpretation.

Calamus River headwaters area

Figure 10: Calamus River headwaters area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 10 illustrates the Calamus River headwaters area located just south of Moon Lake (see figures 1 and 2 for figure 10 location). The Calamus River is southeast oriented and south-oriented and in figure 10 those orientations are consistent with the dune orientations. For that reason it is difficult to say whether the Calamus River southeast-orientation originated prior to dune development or as a result of the dune development. Evidence presented here and in other essays suggests the Calamus River southeast orientation may be a reflection of southeast-oriented flood waters that once flowed across the Niobrara River-North Loup River drainage divide and that deposited the sand deposits now forming the dunes. If so the southeast-oriented Calamus River valley orientation is further evidence supporting the flood interpretation (see figures 1 and 2 for Calamus River southeast orientation south and east of the figure 10 map area). If the Calamus River southeast orientation has been completely determined by dune orientations then figure 10 simply illustrates further the immense size of the Nebraska Sand Hills region and vast amount of flood-deposited sediment required to produce such a large sand dune region.

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.