scholarly journals Alaska GeoSurvey News - Evidence for late Wisconsinan outburst floods in the Tok-Tanacross basin, upper Tanana River valley, east-central Alaska

2010 ◽  
Author(s):  
T. D. Hubbard ◽  
R. D. Reger
Keyword(s):  
River Valley ◽  
East Central ◽  
Outburst Floods ◽  
Late Wisconsinan

Source and Origin of Roxana Silt and Middle Wisconsinan Midcontinent Glacial Activity

1989 ◽  
Vol 31 (3) ◽  
pp. 319-331 ◽  
Author(s):  
W. Hilton Johnson ◽  
Leon R. Follmer
Keyword(s):  
Mississippi River ◽  
Lake Michigan ◽  
Drainage System ◽  
River Valley ◽  
Upper Mississippi River ◽  
Upper Great Lakes ◽  
Mississippi River Valley ◽  
Depositional System ◽  
Stratigraphic Position ◽  
Late Wisconsinan

AbstractThick Roxana Silt (middle Wisconsinan) in central and southwestern Illinois traditionally has been interpreted as loess derived from valley-train deposits in the ancient Mississippi River valley. Winters et al. (H. A. Winters, J. J. Alford, and R. L. Rieck, Quaternary Research 29, 25–35, 1988) recently suggested that the Roxana was not directly related to glacial activity, but was derived from sediment produced by increased shoreline and spillway erosion associated with a fluctuating ancestral Lake Michigan. Because (1) paleoenvironmental and paleohydrologic conditions inferred in the hypothesis are unlikely for a loess depositional system and (2) loess did not accumulate during late Wisconsinan deglaciation under conditions similar to those hypothesized, we suggest the hypothesis should be rejected. Roxana distribution suggests the major source was drainage from the upper Mississippi River valley, and variations in loess thickness in Illinois can be explained by consideration of valley width, depth, orientation, and postdepositional erosion. Tills in the headwaters region of the ancient Mississippi drainage system in Minnesota and Wisconsin occur in the appropriate stratigraphic position and have colors and mineralogic compositions that suggest they could be the parent till of the Roxana. We believe a valley-train source for thick Roxana is most probable and urge continued consideration of middle Wisconsinan glaciation in the upper Great Lakes area.

Holocene emergence at Cape Herschel, east-central Ellesmere Island, Arctic Canada: implications for ice sheet configuration

1992 ◽  
Vol 29 (9) ◽  
pp. 1958-1980 ◽  
Author(s):  
Weston Blake Jr.
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Convincing Evidence ◽  
Ellesmere Island ◽  
East Central ◽  
Radiocarbon Age ◽  
Ice Stream ◽  
Emergence Curve ◽  
Late Wisconsinan

Twenty-five radiocarbon age determinations on marine molluscs, basal organic pond sediments, charred remains in archeological sites, and a variety of other materials have allowed the construction of an emergence curve for Cape Herschel, east-central Ellesmere Island (78°35′N, 74°40′W). Only a narrow fringe of land is present between the Prince of Wales Icefield and Smith Sound, yet emergence of the order of 135 m has taken place during the last 8500–8700 radiocarbon years. The highest in situ shells were collected at an elevation of 107.5 m, and ages of 8470 ± 100 BP (GSC-3314) and 8230 ± 70 BP (TO-230) were obtained on this material.The spectacular and fresh-appearing glacial sculpture along both sides of Smith Sound, coupled with the rapid emergence in Holocene time and the fact that the oldest dates on marine shells at the fiord heads to the west are 3000–4000 years younger than those at Cape Herschel, provides convincing evidence that an ice stream filled Smith Sound (> 500 m deep) during the Late Wisconsinan glacial maximum. The Smith Sound Ice Stream drained southward from the Greenland Ice Sheet and the Innuitian Ice Sheet, which were confluent over Kane Basin, and it overrode the top of Pim Island (550 m asl). Massive melt-off of ice must have been occurring at the transition from Pleistocene to Holocene time, and this melting continued until the mid-Holocene, when all investigated outlet glaciers were behind their present positions.

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