Ice-walled-lake plains: Implications for the origin of hummocky glacial topography in middle North America

Clayton, L.; Attig, J. W.; Ham, N. R.; Johnson, M. D.; Jennings, C. E.; Syverson, K. M.

Abstract:

Ice-walled-lake plains are prominent in many areas of hummocky-till topography left behind as the Laurentide Ice Sheet melted from middle North America. The formation of the hummocky-till topography has been explained by: (1) erosion by subglacial floods; (2) squeezing of subglacial till up into holes in stagnant glacial ice; or (3) slumping of supraglacial till. The geomorphology and stratigraphy of ice-walled-lake plains provide evidence that neither the lake plains nor the adjacent hummocks are of subglacial origin. These flat lake plains, up to a few kilometers in diameter, are perched as much as a few tens of meters above surrounding depressions. They typically are underlain by laminated, fine-grained suspended-load lake sediment. Many ice-walled-lake plains are surrounded by a low rim ridge of coarser-grained shore sediment or by a steeper rim ridge of debris that slumped off the surrounding ice slopes. The ice-walled lakes persisted for hundreds to thousands of years following glacial stagnation. Shells of aquatic molluscs from several deposits of ice-walled-lake sediment in south-central North Dakota have been dated from about 13 500 to 10 500??B.P. (calibrated radiocarbon ages), indicating a climate only slightly cooler than present. This is confirmed by recent palaeoecological studies in nearby non-glacial sites. To survive so long, the stagnant glacial ice had to be well-insulated by a thick cover of supraglacial sediment, and the associated till hummocks must be composed primarily of collapsed supraglacial till. ?? 2007 Elsevier B.V. All rights reserved.

Genre:

Article

ProdID:

70032042

Citation Author:

Clayton, L.; Attig, J. W.; Ham, N. R.; Johnson, M. D.; Jennings, C. E.; Syverson, K. M.

Citation Contributing Office:

Citation Datum:

Citation Day:

Citation Edition:

Citation Editor:

Citation End Page:

248

Citation Issue:

1-2

Citation Keywords:

Citation Language:

English

Citation Larger Work Title:

Geomorphology

Citation LatN:

Citation LatS:

Citation LonE:

Citation LonW:

Citation Month:

Citation No Pagination:

Citation Number Of Pages:

Citation Online Only Flag:

Citation Phsyical Description:

Citation Projection:

Citation Public Comments:

Citation Publisher:

Citation Series:

Citation Series Code:

Citation Series Number:

Citation Search Results Text:

Ice-walled-lake plains: Implications for the origin of hummocky glacial topography in middle North America; 2008; Article; Journal; Geomorphology; Clayton, L.; Attig, J. W.; Ham, N. R.; Johnson, M. D.; Jennings, C. E.; Syverson, K. M.