Belle Fourche River drainage basin landform origins, Wyoming and South Dakota, USA, overview essay

Authors

A geomorphic history based on topographic map evidence

Abstract:

This essay provides an overview of more detailed essays using topographic map evidence to illustrate and describe Belle Fourche River drainage basin landform origins. The detailed essays can be found under Belle Fourche River on this website’s sidebar category list. The Belle Fourche River drainage basin is located in northeast Wyoming and western South Dakota. The Bell Fourche River originates in Wyoming’s Powder River Basin and flows in a northeast direction along the Black Hills western flank. The north-oriented Powder River and Little Missouri River drainage basins are located west of the Wyoming Belle Fourche River drainage basin. North of the Black Hills the Belle Fourche River turns to flow in a southeast and then east direction and joins the northeast oriented Cheyenne River east of the Black Hills. The Cheyenne River drainage basin is located south of the Belle Fourche River drainage basin in both Wyoming and South Dakota and the Cheyenne River flows in a southeast and then northeast direction around the Black Hills south end. West of the Black Hills northwest-oriented Belle Fourche River tributaries are linked by through valleys with southeast oriented Cheyenne River tributaries. Through valleys eroded into the high Black Hills upland surface also link north-oriented Belle Fourche River tributaries with south, southeast, and east-oriented Cheyenne River tributary valleys. Topographic map evidence consisting of southeast-northwest oriented Belle Fourche River tributaries and northwest-southeast oriented through valleys crossing present day drainage divides, including drainage divides in the high Black Hills, is interpreted to mean a deep Belle Fourche River valley eroded headward around the Black Hills northeast and northwest flanks to capture immense southeast-oriented floods, which prior to Belle Fourche River valley headward erosion flowed across what is now the Black Hills upland surface. Flood waters were derived from a rapidly melting thick North American ice sheet and deeply eroded the region surrounding the Black Hills. The ice sheet was located in a deep “hole” north and east of the Belle Fourche River drainage basin area and as the ice sheet roots melted deep northeast and east-oriented valleys eroded headward from the deep “hole” to capture the immense southeast-oriented ice marginal floods. Delayed crustal warping triggered by the thick ice sheet weight and deep flood water erosion of ice sheet margin areas may also have contributed to emergence of the present day Black Hills as a high upland region.

Figure 1: Location map for Belle Fourche River in northeast Wyoming and western South Dakota. National Geographic Society map digitally presented using National Geographic Society TOPO software.

Belle Fourche River drainage basin drainage history

Figure 1 above provides a location map for the Belle Fourche River drainage basin, which  is located in northeast Wyoming and western South Dakota. The Belle Fourche River originates in Wyoming’s Powder River Basin south of Gillette, Wyoming and flows in a northeast direction to and along the Black Hills northwest flank and almost reaches the Montana state line. Instead of continuing in a northeast direction the Belle Fourche River then makes an abrupt turn to flow in a southeast direction along the Black Hills northeast flank and finally turns to flow in an east direction to join the northeast oriented Cheyenne River. The Cheyenne River then flows to the south and southeast oriented Missouri River with water eventually reaching the Gulf of Mexico. West of the Belle Fourche River headwaters is the north and northeast oriented Powder River drainage basin, which drains to the northeast oriented Yellowstone River, which in turn flows to the southeast oriented Missouri River. West of the Belle Fourche River in the western Black Hills area is the northeast and north-oriented Little Missouri River drainage basin, which also drains to the Missouri River. North of the Belle Fourche River drainage basin in South Dakota is the southeast and northeast oriented Moreau River drainage basin, which drains to the Missouri River. South and east of the Belle Fourche River drainage basin is the Cheyenne River drainage basin, with the Cheyenne River flowing in a southeast and northeast direction around the Black Hills south end. Note on figure 1 how many Cheyenne River tributaries flowing from the Belle Fourche River-Cheyenne River drainage divide in both the Wyoming Powder River Basin and in the high Black Hills are oriented in a southeast direction. Also note the predominance of southeast and northwest-oriented tributaries to all major northeast- and north-oriented rivers in the figure 1 map area. This northwest-southeast drainage alignment is better seen on more detailed maps and is an important landform feature requiring an explanation.

Figure 2: Belle Fourche River in Wyoming Powder River Basin south of Gillette, Wyoming. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 2 illustrates the northwest-southeast alignment of Belle Fourche River tributaries in Wyoming’s Powder River Basin at a location south of Gillette, Wyoming. The northeast-oriented Belle Fourche River flows from the figure 2 west center edge to the north edge (east half). The spot elevation near where the highway crosses the Belle Fourche River is 1415 meters. Note how tributaries from the north and west are generally oriented in a southeast direction and tributaries from the south and east are generally oriented in a northwest direction. Hay Creek is somewhat of an exception and flows in a north-northeast and north-northwest direction to join the Belle Fourche River near the highway in the figure 2 north center area. Note how Hay Creek tributaries from the west are southeast-oriented and tributaries from the east are northwest-oriented. Also note how southeast-oriented Hay Creek tributaries are linked by through valleys with northwest-oriented Belle Fourche River tributaries. East of Hay Creek, near the figure 2 east edge, is north-northeast oriented West Fork Coal Creek, which near the figure 2 northeast corner joins north-northwest oriented Middle Fork Coal Creek to form northwest-oriented Coal Creek (which is a Belle Fourche River tributary). Note also through valleys linking northwest-oriented Hay Creek valleys with the north-northeast oriented West Fork Coal Creek valley. The northwest-southeast oriented drainage alignment and through valleys provide evidence the West Fork Coal Creek, Hay Creek, and Belle River valleys eroded headward across multiple southeast-oriented flood flow channels such as might be found in southeast-oriented anastomosing channel complex. Headward erosion of the north-northeast oriented West Fork Coal Creek valley was slightly in advance of Hay Creek valley headward erosion and captured the southeast-oriented flood flow first. Hay Creek valley headward erosion was slightly in advance of Belle Fourche River valley headward erosion and captured the southeast-oriented flood flow second and in doing so beheaded flood flow channels to the newly eroded north-northeast oriented West Fork Coal Creek valley. Headward erosion of the northeast-oriented Belle Fourche River valley beheaded  southeast-oriented flood flow routes to the newly eroded Hay Creek valley. In each case flood waters on northwest ends of beheaded flood flow routes reversed flow direction to erode the northwest-oriented tributary valleys. Also in each case headward erosion of the north- or northeast-oriented valley beheaded southeast-oriented flood flow channels one channel at a time (from north to south). Because flood flow channels were anastomosing (or interconnected) reversed flood flow in a newly beheaded channel could capture flood flow from channels further to the south or southwest. Such captures of flood flow aided in the erosion of the northwest-oriented tributary valleys. Southeast-oriented tributary valleys were eroded by southeast-oriented flood flow continuing to flow into each of the newly eroded north- or northeast-oriented deep valleys.

Figure 3: Belle Fourche River segment in Devils Tower and Hulett, Wyoming area along Black Hills west flank. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 3 provides a topographic map of the Belle Fourche River valley in the Devils Tower and Hulett, Wyoming area along the Black Hills west flank. The Belle Fourche River flows in a north direction just west of the highway and near Devils Tower (near the figure 3 south edge) and then turns to flow in a northeast direction past Hulett to the figure 3 north edge (east half). Note how Belle Fourche River tributaries from the west are southeast-oriented and tributaries from the east are northwest oriented. Northwest-oriented drainage in the figure 3 northwest corner flows to the northeast-oriented Little Missouri River. The northwest and northeast-oriented stream along the figure 3 east center edge is Lame James Creek, which flows to north and northwest-oriented Beaver Creek (which is a Belle Fourche River tributary). While the figure 3 topography is very different from the figure 2 topography, suggesting very different bedrock characteristics, the northwest-southeast drainage alignment of Belle Fourche River tributaries is still present in the figure 3 map area. Belle Fourche River drainage basin detailed essays (found under Belle Fourche River on the sidebar category list) provide topographic maps illustrating through valleys linking northwest-oriented Belle Fourche tributary valleys seen in figure 3 with valleys of north-oriented Belle Fourche River tributaries, such as Lame James Creek and Beaver Creek. The Belle Fourche River valley floor elevation is generally less than 1200 meters in the figure 3 map area and decreases to the northeast. Elevations of hills on either side rise to 1400 meters and even higher suggesting the Belle Fourche River valley was at least 200 meters deep when eroded and may have been even deeper. While most figure 3 upland elevations are not significantly greater than elevations in the figure 2 map area, there is a region between the figures 2 and 3 map areas where upland elevations are lower and southeast-oriented through valleys with floor elevations of less than 1320 meters link northwest-oriented Belle Fourche River tributaries with southeast-oriented Cheyenne River tributaries. These through valleys are illustrated in topographic maps in detailed essays found under Cheyenne River and Belle Fourche River on the sidebar category list. Maps in essays found under Little Missouri River and Belle Fourche River on the sidebar category list also illustrate through valleys linking southeast-oriented Belle Fourche River tributary valleys with northwest-oriented Little Missouri River tributary valleys. The northwest-southeast oriented drainage alignment and the through valleys provide evidence the southeast-oriented floods crossed this western edge of the Black Hills uplift area and the deep northeast-oriented Belle Fourche River eroded headward across multiple southeast-oriented flood flow channels such as might be found in a large southeast-oriented anastomosing channel complex.

Figure 4: Belle Fourche River elbow of capture at Black Hills north end. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 4 illustrates the Belle Fourche River elbow of capture where the northeast oriented Belle Fourche River turns to flow in a southeast direction. Alzada, Montana is the town located near the figure 4 north center edge and the west to east oriented Montana-Wyoming state line is located a short distance south of Alzada. The northeast and north-oriented river flowing from the figure 4 west center edge to the figure 4 north center edge at Alzada is the Little Missouri River. North of the figure 4 map area the Little Missouri River flows in a generally north direction to west-central North Dakota where it turns to flow in an east direction to join the southeast-oriented Missouri River. The Belle Fourche River flows in a north-northeast direction from the figure 4 south center edge to the Stoneville Flats area and then turns to flow in a southeast direction to the figure 4 southeast corner. Stoneville Flats is a northwest-southeast oriented through valley linking the north-oriented Little Missouri River valley with the southeast-oriented Belle Fourche River valley. Today northwest-oriented Arkansas Creek drains much of the Stoneville Flats lowland floor and provides evidence that once water flowed in a north-northwest direction in the Stoneville Flats valley. This evidence could be interpreted to mean headward erosion of the southeast-oriented Belle Fourche River captured the north-oriented Belle Fourche River, which previously had been flowing in a north direction to the north-oriented Little Missouri River valley. While in a sense somewhat correct this interpretation by itself overlooks other figure 4 evidence for immense southeast-oriented floods, which flowed across the figure 4 map area. Note the southeast-and northwest orientation of tributaries to the northeast and north-oriented Little Missouri River and Belle Fourche Rivers. Also note northwest-southeast oriented through valleys linking northwest-oriented Little Missouri River tributary valleys with southeast-oriented Belle Fourche River tributary valleys. This tributary drainage alignment and the through valleys provide evidence the southeast-oriented Belle Fourche River valley probably eroded headward into the figure 4 map area during an immense southeast-oriented flood, which was being captured and diverted in a north direction by headward erosion of the north-oriented Belle Fourche River and Little Missouri River valleys. The figure 4 map evidence demonstrates the deep north-oriented Belle Fourche River eroded headward to capture the southeast-oriented flood flow prior to headward erosion of the northeast-oriented Little Missouri River valley, which beheaded southeast-oriented flood flow routes to the newly eroded Belle Fourche River valley. In other words, Little Missouri River valley headward erosion beheaded and reversed southeast-oriented flood flow to the newly eroded northeast-southeast oriented Belle Fourche River valley, and was just as important in the capture events as headward erosion of the southeast-oriented Belle Fourche River valley.

Figure 5: Through valleys in high Black Hills (linking northwest-oriented Cold Springs Creek with southeast-oriented Castle Creek) eroded across the Belle Fourche River-Cheyenne River drainage divide. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 5 provides evidence south and/or southeast-oriented flood waters crossed what is now the high Black Hills upland surface.  The northwest and north-oriented streams in the figure 5 northern third are headwaters of northwest-oriented Cold Springs Creek, which flows to north-oriented Sand Creek, which in turn flows to the northeast and north-oriented Redwater River, which reaches the Belle Fourche River at Belle Fourche, South Dakota, which is north of the Black Hills. South and southeast-oriented drainage in the figure 5 southeast quadrant represents the headwaters of Castle Creek, which eventually reaches east-oriented Rapid Creek, which flows to the northeast-oriented Cheyenne River east of the Black Hills. Northwest and southeast-oriented drainage in the figure 5 southwest quadrant represents headwaters of south oriented Redbird Creek and south oriented Stockade Beaver Creek, both of which flow in a south direction to join the southeast oriented Cheyenne River south of the Black Hills. Note how these diverging drainage systems are linked by well-defined through valleys eroded into the Black Hills upland surface. Elevations in the figure 5 map area are all greater than 2000 meters and upland areas between the valleys rise to more than 2100 meters. Figure 5 elevations are in feet, I am using meters here for comparison with Belle Fourche River valley elevations shown in figures 2, 3, and 4 where elevations were given in meters. The elevation where the Redwater River joins the Belle Fourche River at Belle Fourche, South Dakota is slightly higher than 900 meters. The figure 5 contour interval is 20 feet and the floor of the through valley linking northwest-oriented Cold Springs Creek with southeast-oriented Castle Creek valley has an elevation of 6847 feet while hills on either side of the through valley rise to elevations greater than 7000 feet. In other words a 150-foot plus deep water eroded through valley links the present day Belle Fourche River drainage basin with the northeast-oriented Cheyenne River drainage basin. Study of the figure 5 map area reveals other similar through valleys linking the north-oriented Cold Spring Creek valleys with the south-oriented Redbird Creek and Stockade Beaver Creek valleys. In other words, there is not just one through valley, but there are several through valleys such as might be found in a large-scale south-oriented flood formed anastomosing channel complex. These through valleys provide evidence a south- and/or southeast-oriented flood crossed what is today a high Black Hills upland surface.

Figure 6: Through valleys in high Black Hills (linking northwest-oriented East Spearfish Creek with southeast-oriented North Fork Rapid Creek) eroded across the Belle Fourche River-Cheyenne River drainage divide. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 6 illustrates additional through valleys eroded across the high Black Hills upland surface. The northwest-oriented stream flowing to the figure 6 northwest corner is the East Spearfish Creek, which north and west of figure 6 flows to north-oriented Spearfish Creek, which joins the southeast-oriented Belle Fourche River north of the Black Hills. The north-oriented stream in the figure 6 north center area is Whitewood Creek, which is another Belle Fourche River tributary. The northeast-oriented stream flowing to the figure 6 northeast corner is Elk Creek, which east of figure 6 turns to flow in a southeast and east direction to eventually join the northeast-oriented Cheyenne River east of the Black Hills. The southeast-oriented stream originating near Dumont in the figure 6 south center area and flowing to the figure 6 south edge (east half) is the North Fork Rapid Creek, which south of the figure 6 map area joins east-oriented Rapid Creek, which flows to the northeast-oriented Cheyenne River east of the Black Hills. Elevations in the figure 6 map area are slightly lower than in the figure 5 map area, but uplands areas still rise to more than 1900 meters. The figure 6 map contour interval is 20 feet and the through valley linking the northwest-oriented East Spearfish Creek valley with the southeast-oriented North Fork Rapid Creek valley has an elevation of between 6140 and 6160 feet. A hill immediately to the north rises to more than 6400 feet and a hill to the south rises to more than 6500 feet. In other words the through valley is at least 240 feet deep and may have been even deeper when eroded. Further the through valley is interesting because a through valley now drained to the northwest by Keough Draw parallels the northwest-oriented East Spearfish Creek through valley. In addition to this northwest-southeast oriented through valley a north-south oriented through valley links the north-oriented Whitewood Creek valley with the southeast-oriented North Fork Rapid Creek valley. The elevation of this through valley floor is hard to read on figure 6, but appears to be slightly higher than 6200 feet. Hills on either side of the through valley rise to elevations greater than 6400 feet. Still another through valley is located in the northwest corner of section 9 (in the figure 6 southeast quadrant) and links the southeast-oriented North Fork Rapid Creek valley with the northeast-oriented Elk Creek valley. The floor of this through valley has an elevation of between 6140 and 6160 feet and hills on either side rise to elevations greater than 6400. These through valleys are water eroded features and only make sense in the context of a flood formed anastomosing channel complex being eroded into the Black Hills upland surface.

  • Why would immense southeast-oriented floods be flowing across what are now the high Black Hills and how could those southeast-oriented flood waters flow across the high elevations? The Belle Fourche River (and Cheyenne River) drainage basin history began with development of a North American ice sheet comparable in size to the present day Antarctic Ice Sheet, if not larger. The ice sheet was thick, probably several kilometers thick, and was located in a deep “hole”, which the ice sheet had formed by a combination of deep glacial erosion and crustal warping caused by the ice sheet weight. When at its maximum size the ice sheet stood high above the pre-glacial surface, but also had roots that extended well below the pre-glacial surface, which no longer exists. The Belle Fourche River (and Cheyenne River) drainage basin was probably located south and west of ice sheet’s southwest margin, although evidence for the ice sheet’s southwest margin has probably been removed by deep melt water flood erosion. The pre-glacial surface under the ice sheet was completely destroyed by deep glacial erosion and the pre-glacial surface adjacent to the ice sheet and elsewhere on the North American continent was deeply eroded by deep melt water flood erosion and was also probably significantly altered by crustal warping caused by the thick North American ice sheet presence.
  • Events important to Belle Fourche River (and Cheyenne River) drainage basin history began as the ice sheet was rapidly melting and had melted to the point that in the south it no longer stood high above the surrounding non-glaciated surface, which had probably already been significantly lowered by deep melt water erosion. Immense melt water floods were flowing in a southeast direction along the ice sheet’s southwest margin and were just beginning to deeply erode the region between the Black Hills and the ice sheet’s southwest margin, which at that time was located north and east of today’s Belle Fourche River (and Cheyenne River) drainage basin. At that time the Black Hills did not stand high above the ice sheet surface, or for that matter above the surface located between the Black Hills and the ice sheet southwest margin. Initially immense floods of melt water flowing from the rapidly melting ice sheet flowed is a southeast direction between what were then the emerging Rocky Mountains and ice sheet southwest margin. Flood waters were probably derived from immense southeast and south-oriented supra-glacial melt water rivers which had carved giant ice-walled and ice-floored (later bedrock-floored) canyons into the decaying ice sheet surface and which flowed to the ice sheet’s southwest margin in present day Alberta and then in a southeast direction along the decaying ice sheet’s southwest margin. The surface on which the southeast-oriented floods were moving was significantly higher than the ice sheet floor elevation and probably no longer exists.
  • How did the deep “hole” the ice sheet had been occupying open up so as to permit headward erosion of the deep northeast-oriented Cheyenne River valley (and north-oriented Little Missouri River valley? Remember, the ice sheet was thick and had deep roots. The ice sheet roots may have extended more than a kilometer below the pre-glacial surface on which the ice sheet had formed. The deep “hole” had probably been formed by a combination of deep glacial erosion of the pre-glacial surface underlying the ice sheet and of crustal warping caused by the weight of an ice sheet several kilometers thick. The crustal warping, which almost certainly did not occur instantaneously, probably also affected regions elsewhere on the continent and may have contributed to uplift of the Black Hills and other North American mountain ranges and high plateau areas as flood waters flowed across them. In other words, not only was the rapidly decaying ice sheet located in a deep “hole” that was opening up as the ice sheet melted, but delayed crustal warping caused by the ice weight was raising mountain ranges and high plateaus regions south and west of the ice sheet margin. The combination of these two events created a situation where the gigantic southeast-oriented melt water river flowing along the decaying ice sheet’s southwest margin was systematically captured by headward erosion of deep northeast-oriented valleys, which were eroding headward from the decaying ice sheet location.
  • In the case of the Cheyenne River valley (and north-oriented Little Missouri River valley) it eroded headward from a huge southeast and south-oriented ice-walled and ice-floored (later bedrock-floored) canyon which was carved by an immense southeast and south-oriented supra-glacial melt water river north and east of the ice sheet southwest margin. The Missouri Escarpment in North and South Dakota and in Saskatchewan is today what remains of that giant canyon’s west and southwest wall. The ice floor of that giant southeast and south-oriented ice-walled canyon was significantly lower in elevation than the bedrock surface south and west of the decaying ice sheet margin and the huge melt water river flowing in that southeast and south-oriented ice-walled canyon represented the region’s major drainage route, which captured the immense southeast-oriented ice-marginal floods by eroding deep northeast and east-oriented tributary valleys headward across the ice sheet’s southwest margin and then headward into the adjacent bedrock surface. These deep northeast-oriented valleys diverted the immense southeast-oriented ice-marginal floods into space the ice sheet had once occupied. Melting of what had been the thick ice sheet roots progressively lowered both the ice sheet surface, the ice-walled canyon floor, and the surrounding bedrock surface, creating a situation where new and even deeper northeast-oriented valleys repeatedly eroded headward to capture the immense southeast-oriented ice-marginal melt water floods.
  • Deep northeast-oriented valleys we see today were probably eroded late in the ice sheet melt down history and were probably preceded by earlier, but similar northeast-oriented valleys which also diverted massive southeast-oriented ice-marginal floods onto the decaying ice sheet surface. Valleys were eroded headward in sequence, with valleys located in the east and south being eroded headward first. Subsequently a major climate change triggered by diversion of south-oriented melt water floods to become north oriented melt water floods caused a new thin ice sheet to form. The diversion of the south-oriented melt water floods from the Gulf of Mexico to the Gulf of Saint Lawrence and Hudson Bay occurred as ice sheet melting opened up north and northeast-oriented drainage routes (or ice-walled and bedrock-floored canyons) between decaying thick ice sheet remnants. Flood water diversion drastically changed ocean circulation patterns and resulted in a cooling of Northern Hemisphere climates. The climate change also caused north-oriented flood waters to freeze on the former ice sheet floor, forming a wet based thin ice sheet with rejuvenated thick ice sheet remnants embedded in it. This new thin ice sheet blocked the new northeast-oriented rivers, which caused northeast-oriented drainage to spill over drainage divides along the new ice sheet’s south-west margin, which created segments of the southeast-oriented Missouri River valley in South and North Dakota and northeast Montana. The Missouri River valley location today approximates the location of decaying thick ice remnants (the Missouri Coteau marks where those remnants were located) that formed the thin ice sheet’s south-west margin.

Figure 7: Map showing southeast-oriented Belle Fourche River tributaries north and east of the Black Hills. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 7 concludes this brief overview of the Belle Fourche River drainage basin detailed essays by illustrating the Belle Fourche River route and tributary orientations in the region north and east of the Black Hills. Note how almost all Belle Fourche River tributaries are oriented in a southeast direction. This southeast-oriented drainage is evidence the region north and east of the Black Hills was eroded by massive southeast-oriented floods. The figure 7 map does not show elevations, although green areas in the figure 7 southwest quadrant are National Forest lands in the Black Hills and generally represent the Black Hills upland location. The Black Hills upland surface is more than 1000 meters higher than the region to the north and east, which was deeply eroded by immense southeast-oriented floods flowing between what must have been the emerging Black Hills upland and the decaying thick ice sheet southwest margin located north and east of the figure 7 map area. The Black Hills upland emerged probably due to a combination of deep flood water erosion of regions around them and delayed crustal uplift triggered by the thick ice sheet weight. Another factor contributing to the Black Hills emergence may have been deep flood water erosion, which removed significant thicknesses of overlying bedrock. The Black Hills present day elevation and evidence flood waters flowed across the Black Hills upland surface provides some evidence as to the magnitude of the flood flow and of the deep glacial erosion and flood water erosion that occurred.

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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