Authors: LACHNIET, MATTHEW S.¹; LARSON, GRAHAME J.²; LAWSON, DANIEL E.³; EVENSON, EDWARD B.⁴; ALLEY, RICHARD B.⁵

Source: Boreas, Volume 30, Number 3, September 2001 , pp. 254-264(11)

Publisher: Wiley-Blackwell

Abstract:

Microstructural analysis of glacial deposits has recently been used as a research tool to determine sediment genesis. However, the occurrence of microstructures in deposits of known origin has not been sufficiently documented, hindering our ability to confidently interpret microstructures in sediments of unknown origin. Our objective is to present a calibration study of microstructures of recent sediment flow deposits and associated sediments from the Matanuska Glacier, Alaska, and to evaluate the degree of commonality with micro-structures found in subglacially deformed sediments. Microstructures in sediment flow deposits can be formed as a result of sediment transport, deposition, and/or post-depositional processes, and are related to the viscosity regime of the source flow. Characteristic microstructures formed during brittle deformation include shears, faults, and brecciation; microstructures formed during ductile deformation include folds, pressure shadows, reorientation of clasts around a `core' stone, fine laminations, basal shear zones, imbrication, and flow fabrics. Other microstructures include fluid escape and injection structures, clast haloes, and fissility. The results of our comparison suggest that sediment flow deposits share many microstructures in common with subglacially deformed sediments.

Document Type: Original article

DOI: http://dx.doi.org/10.1080/030094801750424166

Affiliations: 1: , Department of Earth Sciences, Syracuse University, Syracuse, NY 13244, USA, Email: mlachnie@syr.edu 2: , Department of Geological Sciences, Michigan State University, East Lansing, MI 48824, USA, Email: larsong@pilot.msu.edu 3: , U.S. Army Cold Regions Research and Engineering Laboratory, Anchorage, AK 99505, USA, Email: dlawson@crrel.usace.army.mil 4: , Department of Earth and Environmental Sciences, Lehigh University, Bethlehem, PA 18015, USA 5: , Earth System Science Center and Department of Geosciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA, Email: ralley@essc.psu.edu

Publication date: 2001-09-01

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