Little Blackfoot River-Boulder River drainage divide area landform origins along continental divide, Powell and Jefferson Counties, Montana, USA

Authors


Abstract:

This essay uses topographic map evidence to interpret landform origins in the region between the Little Blackfoot River and the Boulder River along the east –west continental divide in Powell and Jefferson Counties Montana. The continental divide in the study region serves as the Powell-Jefferson County border with Powell County being west of the continental divide. South and east of the continental divide the study region is drained by south and southeast oriented Boulder River tributaries. The Boulder River, which after flowing in a north direction, turns to flow in an east, southeast, and south-southwest direction to join the east oriented Jefferson River, which flows to the north oriented Missouri River with water eventually reaching the south oriented Mississippi River and the Gulf of Mexico. North and west of the continental divide the study region is drained by north, northwest, and west oriented Little Blackfoot River tributaries. The Little Blackfoot River originates along the continental divide and flows in a generally north, west-northwest, and southwest direction to join the northwest oriented Clark Fork. Multiple through valleys (or mountain passes) cross the continental divide and other study region drainage divides and link valleys of the Little Blackfoot River tributaries with valleys of the Boulder River tributaries and also provide linkages between valleys on both sides of the continental divide. South and southeast oriented flood flow channels eroded the through valleys. At that time the continental divide did not exist and Montana mountain ranges were just beginning to emerge. Floodwaters were derived from a thick North American ice sheet and were flowing from western Canada across Montana. The thick ice sheet was located in a deep “hole” and the ice sheet weight was causing crustal warping that raised Montana and Wyoming mountain ranges. Floodwaters flowed across what were emerging mountain ranges and carved deep valleys into them. Headward erosion of deep southeast, northeast, and east oriented valleys, including headward erosion of the deep northeast oriented Missouri River valley from space in the deep “hole” being opened up by ice sheet melting, captured south oriented flood flow east of the present day continental divide. Floodwaters on north ends of beheaded flood flow channels reversed flow directions to erode north oriented valleys. Barbed tributaries provide further evidence of the flood flow captures and reversals. West of the continental divide the south and southeast oriented flood flow channels were beheaded and reversed by headward erosion of the west oriented Little Blackfoot River valley segments, to create north and northwest oriented drainage routes and the continental divide.

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 Little Blackfoot River-Boulder River drainage divide area landform origins along the continental divide in Powell and Jefferson Counties, Montana and 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 Little Blackfoot River-Boulder River drainage divide area landform evidence along the continental divide in Powell and Jefferson Counties, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Little Blackfoot River-Boulder River drainage divide area location map

Figure 1: Little Blackfoot River-Boulder 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 Little Blackfoot River-Boulder River drainage divide area along the continental divide in Powell and Jefferson Counties, Montana and illustrates a region in western Montana. The Missouri River is located in the east half of figure 1 and is formed at Three Forks (near south edge in southeast quadrant) at the confluence the north and northwest oriented Gallatin River (not labeled), the north oriented Madison River (not labeled), and the northeast, east, and northeast oriented Jefferson River. From Three Forks the Missouri River flows in a north and north-northwest direction to Canyon Ferry Lake and Holter Lake before turning to flow in a northeast and east direction to the north edge of figure 1. North and east of figure 1 the Missouri River flows in an east direction to North Dakota where it turns to flow in a southeast and south direction with water eventually reaching the Gulf of Mexico. The Boulder River originates north of Butte and flows in a north direction before turning to flow in an east direction to the towns of Basin and Boulder. From the town of Boulder the Boulder River flows in a southeast and south-southwest direction to join the Jefferson River near Cardwell. West of the east-west continental divide and of Butte is Clark Fork (Columbia River), which flows in a north direction from Warm Springs through Deer Lodge to Garrison and then turns to flow in a northwest direction to Goldcreek and Drummond before reaching the west center edge of figure 1. West of figure 1 Clark Fork joins the Columbia River with water eventually reaching the Pacific Ocean. The Little Blackfoot River is the unlabeled west oriented tributary flowing from Elliston and Avon to join Clark Fork near Garrison. The Little Blackfoot-Boulder River drainage divide area illustrated and discussed in this essay is located between the north and west oriented Little Blackfoot River headwaters and the north and east oriented Boulder River headwaters. The Clark Fork-Boulder River drainage divide area along the continental divide north of Butte, Montana essay illustrates and discusses the region immediately to the south of the region illustrated and discussed here.

Before looking at detailed maps of the Little Blackfoot River-Boulder River drainage divide area a brief look at the big picture erosion history is appropriate. Large volumes of south and southeast oriented floodwaters once flowed across the region shown by figure 1, including the present day north and west-northwest oriented Clark Fork drainage basin west of the continental divide. Floodwaters were derived from the western margin of a rapidly melting thick North American ice sheet and were flowing in a south and southeast direction from southwest Alberta and southeast British Columbia to and across the figure 1 region. At that time (at least initially) there were no high mountains in western Montana or in the region south of figure 1 and floodwaters could freely flow across locations that are today high mountain ranges. Western Canada, Montana, Wyoming, and other mountain ranges were formed by ice sheet related crustal warping and occurred as floodwaters flowed across rising mountain masses. In addition, deep flood water erosion of valleys and basins surrounding the rising mountain ranges contributed to the emergence of present day mountain ranges. In time the ice sheet related crustal warping combined with deep glacial erosion under the ice sheet created a deep “hole” in which the ice sheet was located. Eventually as the ice sheet melted there came a time when elevations on the ice sheet surface (at least in the south) were lower than elevations along the deep “hole” southwest rim where the immense south and southeast oriented ice marginal melt water floods were flowing. Deep northeast oriented valleys then eroded headward from space in the deep “hole” being opened up by the ice sheet melting to capture the south and southeast oriented melt water floods in present day Montana.

The northeast oriented Missouri River valley segment north of figure 1) and its east and northeast oriented tributary valleys eroded headward from the deep “hole” across the south and southeast oriented flood flow. Northwest oriented Missouri River tributary valleys and the north-northwest oriented Missouri River valley segment seen in figure 1 were eroded by reversals of flood flow on north and northwest ends of beheaded flood flow channels. The present day north oriented Madison River, north and northwest oriented Gallatin River, and north oriented Jefferson River and their north and northwest oriented tributary alignments were established initially as south oriented flood flow channels, which were reversed and deepened during the massive upper Missouri River drainage basin flood flow reversal. Uplift of the Yellowstone Plateau and mountain ranges south of figure 1 probably contributed significantly to the massive flood flow reversal. Headward erosion of the east oriented Jefferson River valley captured south oriented flood flow on the present day south oriented Boulder River alignment. The north oriented Boulder River segment flows on the alignments of what began as south oriented flood flow channels. Floodwaters on north ends of those south oriented flood flow channels reversed flow direction when headward erosion of the deep east oriented Boulder River beheaded the south oriented flood flow routes.

A similar situation occurred west of the continental divide where headward erosion of the deep south oriented Columbia River valley and tributary valleys (north and west of figure 1) beheaded and reversed southeast and south oriented flood flow channels to create the present day north and northwest oriented Clark Fork drainage system. The southwest oriented Little Blackfoot River valley segment probably eroded headward from a south oriented flood flow channel on the present day north oriented Clark Fork alignment in figure 1. North oriented Little Blackfoot River tributary and headwaters valleys were eroded by reversals of flood flow on north ends of beheaded south oriented flood flow routes. The reversal of flood flow that created the north and northwest oriented Clark Fork drainage system simply diverted the Little Blackfoot River flood flow to the northwest and to the Columbia River (when the former south oriented flood flow channel south of Garrison was reversed to create the north and northwest oriented Clark Fork north of Deer Lodge Pass across the present day continental divide).

Detailed location map for Little Blackfoot River-Boulder River drainage divide area

Figure 2: Detailed location map Little Blackfoot River-Boulder River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 2 provides a more detailed location map for the Little Blackfoot River-Boulder River drainage divide area along the continental divide in Powell and Jefferson Counties, Montana and shows drainage routes not seen in figure 1. County boundaries are shown. Jefferson County is labeled and Powell County is the unlabeled county in the northwest quadrant of figure 2. Helena is located in Lewis and Clark County, which is north of Jefferson County and east of Powell County. Green shaded areas are National Forest lands, which generally are located in mountainous regions. The east-west continental divide is labeled and is followed by the Jefferson County-Powell County boundary. Canyon Ferry Lake is located near the northeast edge of figure 2 and is a large reservoir flooding the north-northwest oriented Missouri River valley. The Boulder River originates on the northeast side of the continental divide (where the Jefferson County west border or continental divide is oriented in a west to east direction in the southwest quadrant of figure 2) and flows in a north direction to near Blizzard Hill and then turns to flow in an east direction to the towns of Basin and Boulder before turning to flow in a southeast and south-southwest direction to join the Jefferson River (south of figure 2). Clark Fork flows in a north direction from the south edge of figure 2 (near southwest corner) to Deer Lodge and Garrison and then in a northwest direction to the west edge of figure 2 (near northwest corner). The Little Blackfoot River originates between Cliff Mountain and Thunderbolt Mountain near the continental divide on the Powell County-Jefferson County border and zig zags in a generally north direction before turning to flow in a west-northwest direction to Elliston and Avon. From Avon the Little Blackfoot River flows in a southwest direction to join Clark Fork near Garrison. The Little Blackfoot River-Boulder River drainage divide area illustrated and discussed in this essay is located along the Powell County-Jefferson County border and extends from the Cliff Mountain-Thunderbolt Mountain area to the Old Baldy Mountain area. Note the south and southeast oriented Boulder River tributaries originating near Thunderbolt Mountain.

Little Blackfoot River-Boulder River drainage divide area

Figure 3: Little Blackfoot River-Boulder River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of the Little Blackfoot River-Boulder River drainage divide area. The continental divide is a labeled dashed line along the Jefferson County west border and is located in the west half of figure 3. The Boulder River is labeled and is in the south half of figure 3 and flows in a northeast and east direction from south edge of figure 3 (west half) to the east edge of figure 3 (south half). South oriented Boulder River tributaries originating near the continental divide are Indian Creek, Rock Creek, and Thunderbolt Creek. Thunderbolt Creek originates at Cottonwood Lake, which is located between Electric Peak and Thunderbolt Mountain. Red Rock Creek is the southeast oriented Boulder River tributary originating near the continental divide just north and east of Thunderbolt Mountain. North of Cottonwood Lake and north of the continental divide are headwaters of the north-northeast oriented Little Blackfoot River, which flows to the north center edge of figure 3 near Blackfoot Meadows. North of figure 3 the Little Blackfoot River turns to flow in a west direction to eventually join northwest oriented Clark Fork. The west and northwest oriented stream originating just west of Electric Peak (on the north or west side of the continental divide) is the Middle Fork of northwest oriented Cottonwood Creek, which is a Clark Fork tributary. Note how through valleys link valleys on opposite sides of the continental divide. Perhaps the easiest through valley to see links the north oriented Little Blackfoot River valley with the south oriented Thunderbolt Creek valley. The map contour interval for figure 3 is 50 meters and the through valley floor elevation at the continental divide is between 2250 and 2300 meters. Thunderbolt Mountain to the east rises to more than 2600 meters while Electric Peak to the west rises to more than 2500 meters. The through valley is at least 200 meters deep and is evidence of a former south oriented flood flow channel that was captured by headward erosion of the east oriented Boulder River valley. Headward erosion of the west oriented Little Blackfoot River north of figure 3 beheaded the south oriented flood flow channel. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to erode the north oriented Little Blackfoot River headwaters valley. Other through valleys can be seen crossing the continental divide and other drainage divides in figure 3. For example, north of Thunderbolt Mountain a through valley links the north oriented Little Blackfoot River valley with the southeast oriented Red Rock Creek valley. Or west of Electric Peak a somewhat shallower through valley links the Middle Fork Cottonwood Creek valley with the south oriented Rock Creek valley. Between Cliff Peak and Electric Peak a through valley links the west and northwest oriented Middle Fork Cottonwood Creek valley with the north oriented Little Blackfoot River valley. These and other through valleys provide evidence of multiple diverging and converging flood flow channels that once crossed the region.

Detailed map of Little Blackfoot River-Red Rock Creek drainage divide area

Figure 4: Detailed map of Little Blackfoot River-Red Rock 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 Little Blackfoot River-Red Rock Creek drainage divide area seen is less detail in figure 3. The Powell County-Jefferson County border is labeled and is also the west-east continental divide with drainage in Powell County flowing to Clark Fork and the Pacific Ocean and drainage in Jefferson County flowing to the Boulder River and the Gulf of Mexico. South oriented Rock Creek in section 31 (near southwest corner of figure 4) flows to Boulder River as does south oriented Thunderbolt Creek, which originates at Cottonwood Lake in section 28. The southeast oriented stream in section 24 (northeast quadrant of figure 4) is Red Rock Creek, which is also a Boulder River tributary.  The north-northeast oriented stream originating in section 22 north of Thunderbolt Mountain is the Little Blackfoot River, which eventually flows to northwest oriented Clark Fork, and the west and west-northwest oriented stream in the northwest quadrant of figure 4 is the Middle Fork Cottonwood Creek, which flows to northwest oriented Cottonwood Creek which then flows to north and northwest oriented Clark Fork, Note how the various diverging drainage routes are linked by through valleys. The map contour interval for figure 4 is 40 feet. In section 30 a 400-foot deep or deeper through valley links the Middle Fork Cottonwood Creek valley with the Rock Creek valley. In section 21 a 1000-foot deep through valley links a northeast oriented Little Blackfoot River tributary valley with the south oriented Thunderbolt Creek valley. Along the line between sections 22 and 23 a 800-foot deep through valley links a Little Blackfoot River tributary valley with a Red Rock Creek tributary valley. These three mentioned through valleys cross the continental divide. Near the corner of sections 16, 17, 20, and 21 a 700-foot deep through valley links the Middle Fork Cottonwood Creek valley with a northeast oriented Little Blackfoot River tributary valley. Other shallower through valleys can also be seen. These through valleys are all water eroded features and were eroded by south and southeast oriented flood flow moving across the region. At first the flood flow was moving to the deep east oriented Boulder River valley, which was eroding headward across the region south of figure 4. Later as headward erosion of the deep west oriented Little Blackfoot River valley north of figure 4 occurred flood flow channels were beheaded and reversed to erode the north oriented Little Blackfoot River headwaters valley seen in figure 4. Southeast oriented flood flow moving on the Cottonwood Creek-Middle Fork Cottonwood Creek alignment then moved in an east direction to the newly reversed Little Blackfoot River alignment and helped erode the north oriented Little Blackfoot River valley. Reversal of flood flow to create north oriented Clark Fork drainage (west of figure 4) also reversed flood flow on the Cottonwood Creek-Middle Fork Cottonwood Creek alignment, which eroded the west and west-northwest oriented Middle Fork valley seen in figure 4.

Little Blackfoot River-Basin Creek drainage divide area

Figure 5: Little Blackfoot River-Basin Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Little Blackfoot River-Basin Creek drainage divide area east and north of figure 3 and includes a significant overlap area with figure 3. The dashed line extending from the west edge of figure 5 (just south of center) to the north edge of figure 5 (east of center) is the Powell County-Jefferson County line and also the continental divide. Drainage south and east of the continental divide flows to the Boulder River. The Boulder River can be seen flowing in an east direction near the southeast corner of figure 5. Southeast oriented tributaries joining the Boulder River in the southeast quadrant of figure 5 are Red Rock Creek and Basin Creek (the town of Basin is located near where Basin Creek joins the Boulder River). West of the Red Rock Creek and Basin Creek headwaters (on the west side of the continental divide) is Blackfoot Meadows and the north-northeast and northwest oriented headwaters of the Little Blackfoot River. Note how the southeast oriented South Fork Basin Creek (which appears to be labeled South Fork Fox Creek-this labeling confusion is cleared up in figure 6) is linked by through valleys with the north and northwest oriented Little Blackfoot River valley. The map contour interval for figure 5 is 50 meters and the deepest through valley has a floor elevation where the trail crosses the continental divide of between 2200 and 2250 meters. Bison Mountain to the north rises to more than 2400 meters while Thunderbolt Mountain to south rises to more than 2600 meters meaning the through valley is at least 150 meters deep. Southeast oriented flood flow on the present day northwest oriented Little Blackfoot River alignment once crossed the continental divide and flowed to the southeast Fox Creek and Basin Creek valleys and then to the Boulder River valley. Headward erosion of a northeast oriented Little Blackfoot River valley segment (north of figure 5-see figure 7) beheaded and reversed the southeast oriented flood flow channel, which eroded the northwest oriented Little Blackfoot River valley segment. Remember, southeast oriented floodwaters were still being captured from the northwest oriented Middle Fork Cottonwood Creek valley, which can be seen originating between Cliff Mountain and Electric Peak in west center region of figure 5. These captures only make sense in the context of an anastomosing complex of flood flow channels, where captured flood flow from one flood flow channel helped erode another flood flow channel and the captured floodwaters were making U-turns until headward erosion of the deep valleys further beheaded and reversed the flood flow channels being captured.

Detailed map of Little Blackfoot River-South Fork Basin Creek drainage divide area

Figure 6: Detailed map of Little Blackfoot River-South Fork Basin Creek 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 Little Blackfoot River-South Fork Basin Creek drainage divide area seen in less detail in figure 5. The Powell County-Jefferson County boundary is labeled and is the continental divide. West and north of the continental divide is the north-northeast and northwest oriented Little Blackfoot River, which flows from the south edge of figure 6 (near southwest corner) to the northwest corner of figure 6. South and east of the continental divide is southeast South Fork Basin Creek and southeast oriented Fox Creek, with Fox Creek joining the South Fork Basin Creek south and east of figure 6. Note the deep through valley crossing the continental divide along the border between sections 12 and 13.  The through valley links a west-northwest oriented Little Blackfoot River tributary valley with an east-southeast oriented South Fork Basin Creek tributary valley. The map contour interval for figure 6 is 40 feet and the through valley floor elevation at the continental divide is between 7280 and 7320 feet. Bison Mountain (on continental divide at north edge of figure 6) rises to 8032 feet and the continental divide elevation on the south edge of figure 6 is more than 8000 feet. These elevations suggest the through valley is 700 feet or more deep. Other much shallower through valleys can also be seen crossing the continental divide such as near the southwest corner of section 13 and near the northwest corner of section 12. These through valleys provide evidence of multiple southeast oriented flood flow channels, which once crossed the region. Over time the deepest flood flow channels captured floodwaters from the shallower flood flow channels until headward erosion of a northeast oriented Little Blackfoot River valley segment (north of figure 6-see figure 7) beheaded and reversed the southeast oriented flood flow, which had been moving to the actively eroding South Fork Basin Creek valley. The flood flow reversal was responsible for creating the north and northwest oriented Little Blackfoot River drainage route seen in figure 6. Also note in section 7 the through valley linking a south, west, and south oriented South Fork Basin Creek tributary valley with the southeast oriented Fox Creek valley. That through valley provides further evidence of the diverging and converging flood flow channels that once crossed the region.

Ontario Creek-Basin Creek drainage divide area

Figure 7: Ontario Creek-Basin Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Ontario Creek-Basin Creek drainage divide area east and north of figure 5 and includes a significant overlap area with figure 5. The Powell County-Jefferson County border and continental divide is shown with a labeled dashed line extending from the southwest corner of figure 7 to the north edge of figure 7 (east of center). The Little Blackfoot River originates between Electric Peak and Thunderbolt Mountain in the southwest quadrant of figure 7 and flows in a north-northeast, northwest, northeast, and north-northwest direction to the north edge of figure 7. The Little Blackfoot River elbows of capture seen in figure 7 show how headward erosion of the northeast oriented Little Blackfoot River valley segment beheaded and reversed a southeast oriented flood flow channel (the channel to the southeast oriented South Fork Basin Creek valley) to create the northwest oriented Little Blackfoot River valley segment. The northeast oriented Little Blackfoot River valley segment eroded headward from the north-northwest oriented Little Blackfoot River valley seen near the north edge of figure 7 (which had been created by a reversal of flood flow on a beheaded southeast oriented flood flow channel). The northwest oriented tributary on the southeast end of that beheaded southeast oriented flood flow channel and originating north of the center of figure 7 and joining the Little Blackfoot River at its elbow of capture just west of Treasure Mountain (near north edge of figure 7) is Ontario Creek. The north oriented Ontario Creek tributary in the center of figure 7 is Bison Creek.  South of the north oriented Bison Creek valley (and of the continental divide) is east and southeast oriented Elk Gulch, which drains to south and south-southeast oriented Basin Creek (remember, Basin Creek joins the Boulder River near the town of Basin). The map contour interval for figure 7 is 50 meters and the floor of the through valley crossing the continental divide between the north-oriented Bison Creek valley and the southeast oriented Elk Gulch valley is between 2050 and 2100 meters. Elevations along the continental divide to the northeast rise to more than 2300 meters while even higher elevations can be found at Bison Mountain to the west. These elevations suggest the through valley is at least 200 meters deep. The through valley provides evidence of still another major southeast and south oriented flood flow channel to the east and south oriented Boulder River valley. The southeast and south oriented flood flow channel was beheaded and reversed by headward erosion of a northeast oriented Little Blackfoot River valley segment north of figure 7, which created the north oriented Bison Creek valley segment, the northwest oriented Ontario Creek valley segment, and the north-northwest oriented Little Blackfoot River valley segment.

Detailed map of Bison Creek-Joe Bower Creek drainage divide area

Figure 8: Detailed map of Bison Creek-Joe Bower Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 provides a detailed topographic map of the Bison Creek-Joe Bower Creek drainage divide area seen in less detail in figure 7 and includes an overlap area with figure 6. The continental divide is also the Powell County-Jefferson County border and is labeled and extends from the northeast corner of figure 8 to the south edge of figure 8 (west half). Bison Creek flows in a north direction from section 4 through sections 33 and 28 to the north edge of figure 8 and joins northwest oriented Ontario Creek north of figure 8. Ontario Creek joins the northeast oriented Little Blackfoot River north of figure 8 and the Little Blackfoot River then turns to flow in a north-northwest direction. Monarch Creek is the northwest, north, east, and north-northeast oriented stream in the northwest quadrant of figure 8 and is also a Ontario Creek tributary. Larabee Gulch is the north oriented stream flowing to the northwest corner of figure 8 and is a Little Blackfoot River tributary. The through valley linking the Little Blackfoot River valley with the South Fork Basin Creek valley, which was discussed in figure 6, is located in sections 12 and 13 in the southwest quadrant of figure 8. Basin Creek flows in a southwest direction from the east edge of figure 8 (north half) to the southeast corner of section 9 and then turns to flow in a south and southeast direction to the south edge of figure 8 (east half). Joe Bower Creek is the southeast oriented stream originating along the continental divide and joining Basin Creek in the southeast corner of section 9. Note how the Joe Bower Creek valley is linked by a through valley across the continental divide in section 4 with the north oriented Bison Creek valley. The map contour interval for figure 8 is 40 feet and the through valley floor elevation at the continental divide is between 6840 and 6880 feet. The continental divide to the northeast rises to more than 7680 feet and to the southwest it rises to more than 7800 feet meaning the through valley is approximately 800 feet deep. The through valley is another example of the multiple through valleys crossing the continental divide in this region. These through valleys were eroded by diverging and converging southeast and south oriented flood flow channels that once moved large volumes of melt water across the study region. At that time elevations north and west of figure 8 were as high if not higher than elevations in the figure 8 region. Mountains and drainage divides emerged as floodwaters flowed across the region and ice sheet related crustal warping raised the mountain ridges.

Basin Creek-Cataract Creek drainage divide area

Figure 9: Basin Creek-Cataract Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Basin Creek-Cataract Creek drainage divide area east of figure 7 and includes a significant overlap area with figure 7. The Powell County-Jefferson County border is located along the continental divide, which is shown by a labeled dashed line extending from the west edge of figure 9 (near southwest corner) to the north edge of figure 9 (near northeast corner). Old Baldy Mountain is located on the continental divide in the north center area of figure 9. Basin Creek originates south of Old Baldy Mountain and flows in a west and southwest direction before turning to flow in a south-southeast direction to the south center edge of figure 9. South of figure 9 Basin Creek joins the Boulder River near the town of Basin. East of the Basin Creek headwaters is Cataract Meadows and the Cataract Basin. Cataract Creek originates in the Cataract Meadows area and flows to Cataract Basin and then in a south and south-southwest direction to the south edge of figure 9. South of figure 9 Cataract Creek joins the Boulder River a short distance east of the town of Basin. The Little Blackfoot River flows in a northeast direction across the northwest corner of figure 9. Ontario Creek is the northwest oriented tributary joining the Little Blackfoot River just north of figure 9. Note how the west oriented Basin Creek headwaters valley is linked by a through valley with the east oriented Cataract Creek headwaters valley. The through valley is located between Old Baldy Mountain to the north and the Three Brothers to the south. The map contour interval for figure 9 is 50 meters and the through valley floor elevation at the drainage divide is between 2250 and 2300 meters. Elevations on Old Baldy Mountain rise to more than 2450 meters while elevations on the Three Brothers to the south rise to more than 2550 meters. In other words the through valley is at least 150 meters deep. Continuing south along the Basin Creek-Cataract Creek drainage divide other west to east oriented through valleys can be seen. For example several through valleys are located between the Three Brothers and Jack Mountain. The deepest of the through valleys has a floor elevation at the drainage divide of between 2300 and 2350 meters. Jack Mountain is more than 100 meters higher than the Three Brothers, which means the through valley is more than 200 meters deep. Note southwest oriented Jack Creek at the west end of that through valley. Jack Creek flows to south-southeast oriented Basin Creek. But a south oriented Jack Creek tributary is linked by a through valley west of the Three Brothers with the west oriented Basin Creek headwaters valley. These through valleys provide further evidence of the diverging and converging flood flow channels that once crossed the region. Study of figure 9 drainage divides reveals many other through valleys, which suggests a complex history as deeper flood flow channels captured flood flow from less deep flood flow channels.

Detailed map of Basin Creek-Jack Creek drainage divide area

Figure 10: Detailed map of Basin Creek-Jack Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 provides a detailed topographic map of the Basin Creek-Jack Creek drainage divide area seen in less detail in figure 9 and includes an overlap area with figure 8. The Powell County-Jefferson County border is located along the continental divide and extends from the west edge of figure 10 (south of center) to the north edge of figure 10 (west of center) and then can be seen along the north edge of figure 10 (east half). Bison Creek flows in a north direction from section 4 to join northwest oriented Ontario Creek just north of the northwest corner of figure 10. Basin Creek originates in section 31 and flows in southwest and west direction to section 35 and then turns to flow parallel to the continental divide in a southwest direction until reaching the southeast corner of section 9 where it turns to flow in a southeast direction. Jack Creek is a southwest oriented stream (south of the west oriented Basin Creek segment) and flows to the south edge of figure 10 (just west of center) and joins Basin Creek south of figure 10. Note the south oriented Jack Creek tributary originating in section 1 and how a deep north to south oriented through valley links that tributary valley with the west oriented Basin Creek valley. The map contour interval for figure 10 is 40 feet and the through valley floor elevation at the drainage divide is between 7120 and 7160 feet. Elevations in section 11 to the southwest rise to 7566 feet while near the east edge of section elevations rise to 8003 feet. In other words the through valley is at least 500 feet deep. The through valley was eroded by south oriented flood flow at the same time that a diverging and converging flood flow channel on the present day Basin Creek alignment was eroding the Basin Creek valley. In time the Basin Creek valley was eroded deeper (and/or crustal warping raised a ridge blocking south oriented flood flow on the Jack Creek tributary valley). In either case the deeper Basin Creek valley captured the south oriented flood flow to the Jack Creek valley. A much higher level through valley can be seen to the east in section 6 and links the southwest oriented Jack Creek headwaters valley with the a northwest oriented Basin Creek tributary valley. This higher level through valley has an elevation at the drainage divide of between 7760 and 7800 feet and is at least 400 feet deep. This higher level through valley provides evidence of a still earlier stage in the flood flow erosion of landscape seen today in figure 10.

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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