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Glaciation of north dakota, U.S.A.
Quaternary Glaciations - Extent and Chronology, Part II Editors J. Ehlers and P.L. Gibbard 9 2004 Elsevier B.V. All rights reserved
Glaciation of North Dakota, U.S.A. John P. Bluemle, John R. Reid and Karen J. R. Mitchell
North Dakota Geological Survey, 600 E Boulevard Avenue, Bismarck, ND 58505-0840, U.S.A. E-mail: [email protected], us
Early history of glacial mapping in North Dakota
of the ice, thereby marking the position of the ice margin for some undefined period of time. The significance is that such ridges were not the result of climatic changes, as most true moraines are traditionally interpreted. The definition and interpretation of these transverse constructional ridges in North Dakota is still unresolved. The tendency is to separate distinct thrust ridges from the more continuous end moraines (cf Fullerton et al., 1995).
Although several studies of the glacial landscape of the upper Great Plains were published in the late 1800's and early 1900's, the first significant interpretation of the region that included parts of North and South Dakota was by Leverett (1932). He named several end moraines, mainly in Minnesota and Iowa. Subsequent glacial mapping by Gwynne (1951), Crandell (1953), and Flint (1955) in South Dakota was for the U.S. Geological Survey. Flint's map was the first synthesis of glaciation for eastern South Dakota and it served as the basis for subsequent mapping in that area. The first synthesis of statewide glaciation in North Dakota was also by the U.S. Geological Survey (Colton et al., 1963). Their Preliminary Glacial Map of North Dakota showed the south-western comer of North Dakota as being non-glaciated, with increasingly younger glacial boundaries to the north and east. End moraines were delineated, as were ground moraine, outwash deposits, stagnation, or collapse moraine and former glacial lakes. This map continued to serve as the basis for all subsequent mapping until the Geologic Map of North Dakota (Clayton et al., 1980b) was published. This map showed that most till deposits formed as the result of either subglacial and marginal thrusting, or of collapse of debris-veneered stagnant and dead ice. The 1980 map was a compilation of extensive geological mapping that had been completed, beginning in 1959, by the North Dakota Geological Survey (NDGS) as part of a series of county groundwater studies. All of the counties in North Dakota were ultimately mapped, and the results have been published by the NDGS at a scale of 1:125,000. Attempts have been made to interpret the mode and stages of glaciation in North Dakota. Each 'end moraine' was initially interpreted as resulting from a significant readvance of glacier ice. Subsequently, most end moraines were interpreted as being the result of a slight readvance or period of stillstand of the ice margin during retreat of the ice sheet. Clayton & Moran (1974) first avoided using the term 'end moraine' for most linear transverse ridges marking former ice margins in North Dakota. Instead, they def'med them as subglacial, marginal ice-thrust ridges, distinct from marginal 'dump' moraines. This mechanism was previously proposed by Bluemle (1970) and subsequently clarified by Bluemle & Clayton (1984). Such marginal 'shear' masses must have impeded further advance
Glacial boundaries in North Dakota General The oldest glacial boundaries in North Dakota are defined by the outermost limits of scattered glacial erratics (Geological Map). Patches of oxidized loamy till can be found in road cuttings within this boundary, but correlation and dating have not yet been possible. It is only in deeper sections, exposed by bluff recession along eastern Lake Sakakawea, that old tills can be identified and defined at the surface (Ulmer & Sackreiter, 1973) (Fig. 2). Here, the oldest till, the upper member of the Medicine Hill Formation, is probably of pre-Illinoian age (Fullerton et al., 1995). The overlying upper member of the Horseshoe Valley Formation is probably Illinoian, and the upper till, the Snow School Formation, is Late Wisconsinan in age. These tills are typically directly overlain by younger tills, with no discernible weathering at contacts; in places, however, the till units are separated by sand and gravelly sand units, interpreted as being of non-glacial origin (Ulmer & Sackreiter, 1973). Description of the tills in the eastern half of North Dakota continues. Again, because weathering horizons (palaeosols) are uncommon, correlation is defined primarily by superposition, texture and lithology. By use of a closelyspaced drilling network, Harris (1996) was able to differentiate numerous tills, but some of these may be separate facies of the same glacial stage. Thus far, no preLate Wisconsinan tills have been specifically identified in eastern North Dakota. However, deep test boreholes in the Devils Lake area (Hobbs & Bluemle, 1987), have penetrated as many as seven discrete till (and associated lacustrine and fluvial) units, several of which are separated by deep weathering profiles. Extensive subsurface study will be needed in this area to understand the complex till stratigraphy there. 207
208
John P. Bluemle, John R. Reid & Karen J. R. Mitchell
~i~i!il!?:-: ~...~:
........!i :~i::~:~:
~:
........~:.,,,,
......
.~+ :~'::~
Fig. 1. Collapsed glacial topography. This area of rolling relief and abundant, random interlocking ridges is located in south-western Nelson County in eastern North Dakota. The ring-shaped hummocks are known informally as 'doughnuts'. Maximum local relief in the area is about 8 metres.
Pre-Wisconsinan boundaries
The earliest-known glacial boundary is marked solely by the outer extent of glacial erratics. This boundary is subject to modification as additional erratics are discovered. The distribution of such erratics reveals that the ice sheet at some time extended much farther into south-western North Dakota than it did during more recent advances. Exposures of a highly-oxidised till, having few coarse clasts, exist outside of the Wisconsinan glacial boundary, but the best exposures of old tills lie along the rapidly retreating bluffs of Lake Sakakawea (Ulmer & Sackreiter, 1973) in the area of the type section of the Coleharbor Group (Bluemle, 1970). If interpretation of the Lake Sakakawea sections is correct (Fullerton, et al., 1995), the erratics mark a preIllinoian glaciation. Some tenuous evidence of early glaciation can be seen in a few places that are well beyond the known limit of glacial erratic boulders. South of Reeder in western Adams County, North Dakota, for example, several gravel-lined channels extend from west to east across an upland area. These and other similar valleys found in various parts of south-westernmost North Dakota may have carried meltwater along the margins of early glaciers. However, if
glaciers advanced across these areas in Early Pleistocene time, little other evidence remains to document their activity.
Wisconsinan boundaries
Phases in the retreat of the Wisconsinan ice sheet were proposed by Clayton & Moran (1982), based on radiocarbon-dated wood associated with tills. Because such datable materials are scarce, Clayton & Moran interpolated and extrapolated ice phases, using topography wherever possible. The omission of numerous other non-wood dates has been objected to by Klassen (1983), who concluded that North Dakota was ice-free before 13,900 yr BP, based on non-wood dates in southern Manitoba. Moran & Clayton (1984) argued that the wood-based dates support an interpretation of retreating ice margins in the Red River Valley of North Dakota/Minnesota 11,300 yr BP and that the only way both interpretations could be correct is if a separate ice-accumulation centre had existed south of the Canadian border, a most unlikely situation. The location and ages of boundaries have been modified from Clayton & Moran (1982).
North Dakota
209
Fig. 2. Vertical air photograph of an ice-thrust hill located immediately down-glacier from a source depression, which is flooded by a lake (Steele Lake). The shape and size of the depression occupied by Steele Lake is similar to the shape of the hill, which was derived from the depression. North is towards the top of the photograph; the town of Anamoose is at the north edge of the picture. Glacier movement was towards the south-east. Glaciotectonic features such as this ice-thrust hill are common in central North Dakota, where this photograph was taken. The ice-thrust feature shown here is a relatively small one; some of the ice-thrust features cover areas over 100 km:. In some places, ice thrusting has excavated and lifted materials as much as 600 metres.
Problems
The main problem that prevents dating the more recent glacial phases in North and South Dakota is that datable wood samples are scarce. Charcoal, from prairie (and human-induced) fires, is common, but difficult to distinguish from the abundant Tertiary lignite fragments scattered throughout the area. Contamination of wood by lignite dust is also a problem. A second problem is that radiocarbon dating is restricted solely to Late Wisconsinan events. Cosmogenic dating of erratics left behind in the older-glaciated areas has not yet been attempted. Beds of volcanic ash, buried within glacial and glaciofluvial deposits in pre-glacial valleys, have been dated (Fullerton, personal communication) and show that
glaciers that advanced about 700,000 yr diverted the Little Missouri River to the east, initiating the carving of the Little Missouri badlands. Glacial deposits beneath the ash beds have to be older than 700,000 yr.
Specific comments relating to the ice margins on the digital geological map (John Bluemle) Ice-Margin No. 1
This is the maximum extent of glacial erratics and thus presumably marks the outermost extent of glaciation in North Dakota (except note cautionary comments in the above
210
John P. Bluemle, John R. Reid & Karen J. R. Mitchell
k,, ~ ~i I..........
~ ii!~!~i~!~~~iiii~i~i~i!ii~iii~i~iii ii~,~ i ,~i~, ::~::.~,~,~:~.:~::~
....
:: .,~i:!~!~i~i~....................................
!i~ ~,~i~?ii,, iiii~ ~!i~i,~84 ....
Fig. 3. Two views of the Dahlen Esker in north-eastern North Dakota. The upper air view shows a portion of the 6 km-long, 125 metre-wide esker ridge. The esker ridge stands between 17 and 27 metres above the surrounding area. It has a generally accordant crest level, but the crest appears irregular because of numerous minor gaps. The lower photograph of the ridge was taken from a vantage on the crest of the esker itself. The esker is composed of poorly sorted sand and gravel, intermixed with glacial sediment (till).
North Dakota
211
Fig. 4. Vertical air photograph of the Lake Agassiz plain in northeastern-most North Dakota, about 13 km south-west of the town of Pembina. North is towards the top of the picture. The array of ice-drag markings in this area is striking and seems to indicate plowing by ice floes or icebergs moving in several different directions. The icebergs that gouged the soft sediment on the lake floor were apparently propelled mainly north-westward by the wind.
text). This margin is certainly pre-Wisconsinan in age and probably pre-Illinoian. This ice margin closely coincides with Clayton's Dunn Advance (Clayton et al., 1980a).
Ice Margin No. 2
This ice margin is also based entirely on the presence of glacial erraties. The frequency of erratics within ice margin
No. 2 is about ten times that beyond ice margin No. 2 (but within ice margin No. 1). Clayton & Moran (1982) refer to this ice margin as the Verone Advance and consider it to be pre-Wisconsinan in age, probably Illinoian. Till deposits exposed in the bluffs along Lake Sakakawea were correlated by Ulmer & Sackreiter (1973) as Horseshoe Valley Formation. Bluemle (1971) identified the same till deposits as 'Dead Man Till'; he formally named the Coleharbor Formation (now considered to be a Group) in
212
John P. Bluemle, John R. Reid & Karen J. R. Mitchell
the same report. It is likely the Horseshoe Valley/Dead Man was deposited during the Verone Advance.
Ice Margin No. 3 This ice margin is probably earliest Wisconsinan in age. Clayton & Moran (1982) refer to it as the Napoleon Advance.
Ice Margin No. 4 This ice margin is Late Wisconsinan in age. As shown, it corresponds closely to Clayton & Moran's (1982) Long Lake/Zeeland/Blue Hill/Newtown/Charlson Advance.
References
Bluemle, J.P. (1970). Anomalous hills and associated depressions in central North Dakota, Geological Society of America Abstracts, Rocky Mountain Section, p. 325. Bluemle, J.P. (1971). Geology of McLean County, North Dakota - Part I, geology, North Dakota Geological Survey Bulletin, 60, 65 pp. Bluemle, J.P. & Clayton, L. (1984). Large-scale glacial thrusting and related processes in North Dakota, Boreas, 13,279-299. Clayton, L. & Moran, S.R. (1974). A glacial process-form model. In: Coates, D.R. (ed.), Glacial Geomorphology: Binghamton State University of New York Publications in Geomorphology, 89-119. Clayton, L. & Moran, S.R. (1982). Chronology of Late Wisconsinan glaciation in middle North America, Quaternary Science Reviews, 1, 55-82. Clayton, L., Moran, S.R. & Bluemle, J.P. (1980a). Explanatory text to accompany the Geologic Map of North Dakota, North Dakota Geological Survey, Report of Investigations, 69, 93 pp. Clayton, L., Moran, S.R., Bluemle, J.P. & Carlson, C.G. (1980b). Geologic Map of North Dakota, U.S. Geological Survey, Scale 1:500,000. Colton, R.B., Lernke, R.W. & Lindvall, R.M. (1963). Preliminary glacial map of North Dakota, U.S. Geological Survey, Miscellaneous Geologic Investigations, Map 1-331. Crandall, D.R. (1953). Pleistocene geology of part of central South Dakota, Geological Society of America Bulletin, 64, 581-598. Elliott, M.C. (1991). Erosion of fractured banks, Lake Sakakawea, North Dakota, unpublished Master's thesis, University of North Dakota, Grand Forks, 220 pp. Flint, R.F. (1955). Pleistocene geology of eastern South Dakota, U.S. Geological Survey Professional Paper, 262, 173 pp. Fullerton, D.S., Bluemle, J.P., Clayton, L, Steece, F.V., Tipton, M.J., Bretz, R. & Geobel, J.E. (1995). Quaternary
geologic map of the Dakotas 4 x 6 Quadrangle, United States, U.S. Geological Survey, Miscellaneous Investigations Series, Map 1-1420 (NL-14). Gwynne, C.S. (1951). Minor moraines in South Dakota and Minnesota, Geological Society of America Bulletin, 62, 233-250. Harris, K.L. (1996). Computer-assisted lithostratigraphy, ln: Harris, K.L., Luther, M.R. & Reid, J.R. (eds), Quaternary geology of southern Lake Agassiz Basin, North Dakota Geological Survey Miscellaneous Investigations Series, 82, 63-78. Hobbs, H. C. & Bluemle, J. P. (1987). Geology of Ramsey County, North Dakota, North Dakota Geological Survey Bulletin, 71, 69 pp. Klassen, R.W. (1983). Chronology of Late Wisconsinan glaciation in Middle North America-Discussion, Quaternary Science Reviews, 1, xxiii-xxiv. Leverett, F. (1932). Quaternary geology of Minnesota and parts of adjacent states, U.S. Geological Survey Professional Paper, 161, 149 pp. Moran, S.R. & Clayton, L. (1984). Chronology of Late Wisconsinan glaciation in middle North America, reply to the comments of R.W. Klassen, Quaternary Science Reviews, 3 (2/3), i-vi. Ulmer, J.H. & Sackreiter, D.K. (1973). Late Cenozoic stratigraphy of Lake Sakakawea bluffs north and west of Riverdale, North Dakota, North Dakota Geological Survey Report of Investigation, 51, 1 plate with text.
Glaciation of North Dakota, U.S.A. John P. Bluemle, John R. Reid and Karen J. R. Mitchell
North Dakota Geological Survey, 600 E Boulevard Avenue, Bismarck, ND 58505-0840, U.S.A. E-mail: [email protected], us
Early history of glacial mapping in North Dakota
of the ice, thereby marking the position of the ice margin for some undefined period of time. The significance is that such ridges were not the result of climatic changes, as most true moraines are traditionally interpreted. The definition and interpretation of these transverse constructional ridges in North Dakota is still unresolved. The tendency is to separate distinct thrust ridges from the more continuous end moraines (cf Fullerton et al., 1995).
Although several studies of the glacial landscape of the upper Great Plains were published in the late 1800's and early 1900's, the first significant interpretation of the region that included parts of North and South Dakota was by Leverett (1932). He named several end moraines, mainly in Minnesota and Iowa. Subsequent glacial mapping by Gwynne (1951), Crandell (1953), and Flint (1955) in South Dakota was for the U.S. Geological Survey. Flint's map was the first synthesis of glaciation for eastern South Dakota and it served as the basis for subsequent mapping in that area. The first synthesis of statewide glaciation in North Dakota was also by the U.S. Geological Survey (Colton et al., 1963). Their Preliminary Glacial Map of North Dakota showed the south-western comer of North Dakota as being non-glaciated, with increasingly younger glacial boundaries to the north and east. End moraines were delineated, as were ground moraine, outwash deposits, stagnation, or collapse moraine and former glacial lakes. This map continued to serve as the basis for all subsequent mapping until the Geologic Map of North Dakota (Clayton et al., 1980b) was published. This map showed that most till deposits formed as the result of either subglacial and marginal thrusting, or of collapse of debris-veneered stagnant and dead ice. The 1980 map was a compilation of extensive geological mapping that had been completed, beginning in 1959, by the North Dakota Geological Survey (NDGS) as part of a series of county groundwater studies. All of the counties in North Dakota were ultimately mapped, and the results have been published by the NDGS at a scale of 1:125,000. Attempts have been made to interpret the mode and stages of glaciation in North Dakota. Each 'end moraine' was initially interpreted as resulting from a significant readvance of glacier ice. Subsequently, most end moraines were interpreted as being the result of a slight readvance or period of stillstand of the ice margin during retreat of the ice sheet. Clayton & Moran (1974) first avoided using the term 'end moraine' for most linear transverse ridges marking former ice margins in North Dakota. Instead, they def'med them as subglacial, marginal ice-thrust ridges, distinct from marginal 'dump' moraines. This mechanism was previously proposed by Bluemle (1970) and subsequently clarified by Bluemle & Clayton (1984). Such marginal 'shear' masses must have impeded further advance
Glacial boundaries in North Dakota General The oldest glacial boundaries in North Dakota are defined by the outermost limits of scattered glacial erratics (Geological Map). Patches of oxidized loamy till can be found in road cuttings within this boundary, but correlation and dating have not yet been possible. It is only in deeper sections, exposed by bluff recession along eastern Lake Sakakawea, that old tills can be identified and defined at the surface (Ulmer & Sackreiter, 1973) (Fig. 2). Here, the oldest till, the upper member of the Medicine Hill Formation, is probably of pre-Illinoian age (Fullerton et al., 1995). The overlying upper member of the Horseshoe Valley Formation is probably Illinoian, and the upper till, the Snow School Formation, is Late Wisconsinan in age. These tills are typically directly overlain by younger tills, with no discernible weathering at contacts; in places, however, the till units are separated by sand and gravelly sand units, interpreted as being of non-glacial origin (Ulmer & Sackreiter, 1973). Description of the tills in the eastern half of North Dakota continues. Again, because weathering horizons (palaeosols) are uncommon, correlation is defined primarily by superposition, texture and lithology. By use of a closelyspaced drilling network, Harris (1996) was able to differentiate numerous tills, but some of these may be separate facies of the same glacial stage. Thus far, no preLate Wisconsinan tills have been specifically identified in eastern North Dakota. However, deep test boreholes in the Devils Lake area (Hobbs & Bluemle, 1987), have penetrated as many as seven discrete till (and associated lacustrine and fluvial) units, several of which are separated by deep weathering profiles. Extensive subsurface study will be needed in this area to understand the complex till stratigraphy there. 207
208
John P. Bluemle, John R. Reid & Karen J. R. Mitchell
~i~i!il!?:-: ~...~:
........!i :~i::~:~:
~:
........~:.,,,,
......
.~+ :~'::~
Fig. 1. Collapsed glacial topography. This area of rolling relief and abundant, random interlocking ridges is located in south-western Nelson County in eastern North Dakota. The ring-shaped hummocks are known informally as 'doughnuts'. Maximum local relief in the area is about 8 metres.
Pre-Wisconsinan boundaries
The earliest-known glacial boundary is marked solely by the outer extent of glacial erratics. This boundary is subject to modification as additional erratics are discovered. The distribution of such erratics reveals that the ice sheet at some time extended much farther into south-western North Dakota than it did during more recent advances. Exposures of a highly-oxidised till, having few coarse clasts, exist outside of the Wisconsinan glacial boundary, but the best exposures of old tills lie along the rapidly retreating bluffs of Lake Sakakawea (Ulmer & Sackreiter, 1973) in the area of the type section of the Coleharbor Group (Bluemle, 1970). If interpretation of the Lake Sakakawea sections is correct (Fullerton, et al., 1995), the erratics mark a preIllinoian glaciation. Some tenuous evidence of early glaciation can be seen in a few places that are well beyond the known limit of glacial erratic boulders. South of Reeder in western Adams County, North Dakota, for example, several gravel-lined channels extend from west to east across an upland area. These and other similar valleys found in various parts of south-westernmost North Dakota may have carried meltwater along the margins of early glaciers. However, if
glaciers advanced across these areas in Early Pleistocene time, little other evidence remains to document their activity.
Wisconsinan boundaries
Phases in the retreat of the Wisconsinan ice sheet were proposed by Clayton & Moran (1982), based on radiocarbon-dated wood associated with tills. Because such datable materials are scarce, Clayton & Moran interpolated and extrapolated ice phases, using topography wherever possible. The omission of numerous other non-wood dates has been objected to by Klassen (1983), who concluded that North Dakota was ice-free before 13,900 yr BP, based on non-wood dates in southern Manitoba. Moran & Clayton (1984) argued that the wood-based dates support an interpretation of retreating ice margins in the Red River Valley of North Dakota/Minnesota 11,300 yr BP and that the only way both interpretations could be correct is if a separate ice-accumulation centre had existed south of the Canadian border, a most unlikely situation. The location and ages of boundaries have been modified from Clayton & Moran (1982).
North Dakota
209
Fig. 2. Vertical air photograph of an ice-thrust hill located immediately down-glacier from a source depression, which is flooded by a lake (Steele Lake). The shape and size of the depression occupied by Steele Lake is similar to the shape of the hill, which was derived from the depression. North is towards the top of the photograph; the town of Anamoose is at the north edge of the picture. Glacier movement was towards the south-east. Glaciotectonic features such as this ice-thrust hill are common in central North Dakota, where this photograph was taken. The ice-thrust feature shown here is a relatively small one; some of the ice-thrust features cover areas over 100 km:. In some places, ice thrusting has excavated and lifted materials as much as 600 metres.
Problems
The main problem that prevents dating the more recent glacial phases in North and South Dakota is that datable wood samples are scarce. Charcoal, from prairie (and human-induced) fires, is common, but difficult to distinguish from the abundant Tertiary lignite fragments scattered throughout the area. Contamination of wood by lignite dust is also a problem. A second problem is that radiocarbon dating is restricted solely to Late Wisconsinan events. Cosmogenic dating of erratics left behind in the older-glaciated areas has not yet been attempted. Beds of volcanic ash, buried within glacial and glaciofluvial deposits in pre-glacial valleys, have been dated (Fullerton, personal communication) and show that
glaciers that advanced about 700,000 yr diverted the Little Missouri River to the east, initiating the carving of the Little Missouri badlands. Glacial deposits beneath the ash beds have to be older than 700,000 yr.
Specific comments relating to the ice margins on the digital geological map (John Bluemle) Ice-Margin No. 1
This is the maximum extent of glacial erratics and thus presumably marks the outermost extent of glaciation in North Dakota (except note cautionary comments in the above
210
John P. Bluemle, John R. Reid & Karen J. R. Mitchell
k,, ~ ~i I..........
~ ii!~!~i~!~~~iiii~i~i~i!ii~iii~i~iii ii~,~ i ,~i~, ::~::.~,~,~:~.:~::~
....
:: .,~i:!~!~i~i~....................................
!i~ ~,~i~?ii,, iiii~ ~!i~i,~84 ....
Fig. 3. Two views of the Dahlen Esker in north-eastern North Dakota. The upper air view shows a portion of the 6 km-long, 125 metre-wide esker ridge. The esker ridge stands between 17 and 27 metres above the surrounding area. It has a generally accordant crest level, but the crest appears irregular because of numerous minor gaps. The lower photograph of the ridge was taken from a vantage on the crest of the esker itself. The esker is composed of poorly sorted sand and gravel, intermixed with glacial sediment (till).
North Dakota
211
Fig. 4. Vertical air photograph of the Lake Agassiz plain in northeastern-most North Dakota, about 13 km south-west of the town of Pembina. North is towards the top of the picture. The array of ice-drag markings in this area is striking and seems to indicate plowing by ice floes or icebergs moving in several different directions. The icebergs that gouged the soft sediment on the lake floor were apparently propelled mainly north-westward by the wind.
text). This margin is certainly pre-Wisconsinan in age and probably pre-Illinoian. This ice margin closely coincides with Clayton's Dunn Advance (Clayton et al., 1980a).
Ice Margin No. 2
This ice margin is also based entirely on the presence of glacial erraties. The frequency of erratics within ice margin
No. 2 is about ten times that beyond ice margin No. 2 (but within ice margin No. 1). Clayton & Moran (1982) refer to this ice margin as the Verone Advance and consider it to be pre-Wisconsinan in age, probably Illinoian. Till deposits exposed in the bluffs along Lake Sakakawea were correlated by Ulmer & Sackreiter (1973) as Horseshoe Valley Formation. Bluemle (1971) identified the same till deposits as 'Dead Man Till'; he formally named the Coleharbor Formation (now considered to be a Group) in
212
John P. Bluemle, John R. Reid & Karen J. R. Mitchell
the same report. It is likely the Horseshoe Valley/Dead Man was deposited during the Verone Advance.
Ice Margin No. 3 This ice margin is probably earliest Wisconsinan in age. Clayton & Moran (1982) refer to it as the Napoleon Advance.
Ice Margin No. 4 This ice margin is Late Wisconsinan in age. As shown, it corresponds closely to Clayton & Moran's (1982) Long Lake/Zeeland/Blue Hill/Newtown/Charlson Advance.
References
Bluemle, J.P. (1970). Anomalous hills and associated depressions in central North Dakota, Geological Society of America Abstracts, Rocky Mountain Section, p. 325. Bluemle, J.P. (1971). Geology of McLean County, North Dakota - Part I, geology, North Dakota Geological Survey Bulletin, 60, 65 pp. Bluemle, J.P. & Clayton, L. (1984). Large-scale glacial thrusting and related processes in North Dakota, Boreas, 13,279-299. Clayton, L. & Moran, S.R. (1974). A glacial process-form model. In: Coates, D.R. (ed.), Glacial Geomorphology: Binghamton State University of New York Publications in Geomorphology, 89-119. Clayton, L. & Moran, S.R. (1982). Chronology of Late Wisconsinan glaciation in middle North America, Quaternary Science Reviews, 1, 55-82. Clayton, L., Moran, S.R. & Bluemle, J.P. (1980a). Explanatory text to accompany the Geologic Map of North Dakota, North Dakota Geological Survey, Report of Investigations, 69, 93 pp. Clayton, L., Moran, S.R., Bluemle, J.P. & Carlson, C.G. (1980b). Geologic Map of North Dakota, U.S. Geological Survey, Scale 1:500,000. Colton, R.B., Lernke, R.W. & Lindvall, R.M. (1963). Preliminary glacial map of North Dakota, U.S. Geological Survey, Miscellaneous Geologic Investigations, Map 1-331. Crandall, D.R. (1953). Pleistocene geology of part of central South Dakota, Geological Society of America Bulletin, 64, 581-598. Elliott, M.C. (1991). Erosion of fractured banks, Lake Sakakawea, North Dakota, unpublished Master's thesis, University of North Dakota, Grand Forks, 220 pp. Flint, R.F. (1955). Pleistocene geology of eastern South Dakota, U.S. Geological Survey Professional Paper, 262, 173 pp. Fullerton, D.S., Bluemle, J.P., Clayton, L, Steece, F.V., Tipton, M.J., Bretz, R. & Geobel, J.E. (1995). Quaternary
geologic map of the Dakotas 4 x 6 Quadrangle, United States, U.S. Geological Survey, Miscellaneous Investigations Series, Map 1-1420 (NL-14). Gwynne, C.S. (1951). Minor moraines in South Dakota and Minnesota, Geological Society of America Bulletin, 62, 233-250. Harris, K.L. (1996). Computer-assisted lithostratigraphy, ln: Harris, K.L., Luther, M.R. & Reid, J.R. (eds), Quaternary geology of southern Lake Agassiz Basin, North Dakota Geological Survey Miscellaneous Investigations Series, 82, 63-78. Hobbs, H. C. & Bluemle, J. P. (1987). Geology of Ramsey County, North Dakota, North Dakota Geological Survey Bulletin, 71, 69 pp. Klassen, R.W. (1983). Chronology of Late Wisconsinan glaciation in Middle North America-Discussion, Quaternary Science Reviews, 1, xxiii-xxiv. Leverett, F. (1932). Quaternary geology of Minnesota and parts of adjacent states, U.S. Geological Survey Professional Paper, 161, 149 pp. Moran, S.R. & Clayton, L. (1984). Chronology of Late Wisconsinan glaciation in middle North America, reply to the comments of R.W. Klassen, Quaternary Science Reviews, 3 (2/3), i-vi. Ulmer, J.H. & Sackreiter, D.K. (1973). Late Cenozoic stratigraphy of Lake Sakakawea bluffs north and west of Riverdale, North Dakota, North Dakota Geological Survey Report of Investigation, 51, 1 plate with text.