CGRG Bibliography of Canadian Geomorphology
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Author : Carlson, A.E.; Jenson, J.W.; and Clark, P.U.
Date : 2005.
Title : Field observations from the Tiskilwa Till, Il And Sky Pilot Till, Mb of the Laurentide Ice Shee.
Publication : Water, Ice, Land, And Life: The Quaternary Interface. Canadian Quaternary Association 2005 Conference June 5-8, 2005, University of Manitoba, Winnipeg, Manitoba.
Issue : Abstract Volume:
Page(s) : A13.
Abstract
We present field and laboratory data from extensive bluff exposures of the Tiskilwa Till (TT) of the Lake Michigan Lobe, IL and the Sky Pilot Till (SPT) of the Hudson Bay Lowlands, MB of the Laurentide Ice Sheet. Both tills are massive and homogeneous; exhibit a relatively constant grain size throughout their ~6 m thickness; and overly a more heterogeneous till with a gradational contact ~0.6 to 1 m thick. These heterogeneous tills grade into the underlying sorted sediment, parts of which are incorporated into the overlying till. Both the TT and SPT contain deformed sand inclusions up to 1 m thick. The TT inclusions have occasional balls of TT within the sand that indicate sand deposition post-dated deposition of the surrounding till. The TT has stronger macrofabric eigenvalues than the SPT, and shows relatively constant fabric strength throughout its thickness. In contrast, the SPT fabric strength increases up-section in 2 to 3 m thick increments. Eigenvectors are consistent with regional ice flow directions at both locations. There is an abrupt change in ice flow direction across the boundary between the N45E-oriented SPT and the underlying S45E-oriented till. Eigenvectors then shift up-section in the SPT from N45E to N75E as ice flow shifted more towards the west. The TT eigenvectors migrate up-section from N40E to N60E and back to N40E, probably correlating with the initial thickening and subsequent thinning of the Lake Michigan Lobe. The TT also contains numerous pieces of wood aligned with ice flow. Six dates on the wood are between 31.4 and >49.9 14C ka. The age distribution of the wood within the section somewhat mimics the eigenvector migration. The deformed sand inclusions and gradational contacts suggest some deformation of till during deposition. The fabric data imply continuous deposition of till at both locations.
Bibliography of Canadian Geomorphology