DOI: 10.1016/j.quascirev.2015.01.015
Scopus记录号: 2-s2.0-84922335910
论文题名: Magnetic fabrics of drumlins of the Green Bay Lobe, southeastern Wisconsin
作者: Vreeland N.P. ; Iverson N.R. ; Graesch M. ; Hooyer T.S.
刊名: Quaternary Science Reviews
ISSN: 2773791
出版年: 2015
卷: 112 起始页码: 33
结束页码: 44
语种: 英语
英文关键词: Deformation
; Drumlin
; Fabric
; Glacier
; Till
Scopus关键词: Deformation
; Deposition
; Erosion
; Fabrics
; Glaciers
; Magnetic anisotropy
; Magnetic susceptibility
; Morphology
; Anisotropy of magnetic susceptibility
; Drumlin
; Erosional process
; Laurentide ice sheets
; Macroscopic heterogeneity
; Magnetic fabrics
; Sediment deposition
; Till
; Landforms
; deformation
; deposition
; drumlin
; glacial transport
; glacier advance
; Laurentide Ice Sheet
; magnetic fabric
; moraine
; pedogenesis
; Quaternary
; till
; Green Bay
; United States
; Wisconsin
英文摘要: To study if the relief of drumlins of the Green Bay Lobe of the Laurentide Ice Sheet is dominantly the result of depositional or erosional processes, we measured the anisotropy of magnetic susceptibility of ~2500 samples of the Horicon till from five drumlins in southeastern Wisconsin. These drumlins contain no macroscopic heterogeneities that might otherwise help guide interpretation of deformation kinematics. Ring-shear experiments on this till provided the calibration necessary to relate fabrics based on principal susceptibilities of multiple intact samples to patterns of subglacial till deformation. Fabric strengths, based on orientations of maximum susceptibility and measured from samples collected below the zone of pedogenesis, weaken abruptly at depths shallower than 2m. The till lacks evidence of systematically divergent or convergent shear related to drumlin shape. Most till has been sheared in directions 6-24° to the east of drumlin long axes, with shear-plane orientations that are unrelated to drumlin morphology. An exception is till at shallow depths (≤2m) where shearing azimuths and shear-plane orientations agree more consistently with drumlin trends and morphologies. The Horicon till was likely deformed in shear during advance of the lobe. Drumlins formed by erosion of this basal till after glacier flow had shifted to the west, when the Johnstown moraine was being built. A supraglacial till, ≤2m thick, was draped over some of the drumlins during retreat of the lobe. These results do not support models of drumlin formation in which sediment deposition helps amplify drumlin relief. © 2015 Elsevier Ltd. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/59998
Appears in Collections: 过去全球变化的重建
There are no files associated with this item.
作者单位: Department of Geological and Atmospheric Sciences, Iowa State University, Ames, IA, United States; Department of Geosciences, University of Wisconsin-Milwaukee, 3209 N. Maryland Ave., Milwaukee, WI, United States
Recommended Citation:
Vreeland N.P.,Iverson N.R.,Graesch M.,et al. Magnetic fabrics of drumlins of the Green Bay Lobe, southeastern Wisconsin[J]. Quaternary Science Reviews,2015-01-01,112