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Title: Sedimentological analysis of the western terminus region of the Matanuska Glacier, Alaska
Authors: Lawson, Daniel E.
Keywords: Glaciers
Glacial deposits
Glacial morphology
Sediment transport
Publisher: Cold Regions Research and Engineering Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: CRREL report ; 79-9.
Description: CRREL Report
Abstract: Sedimentation at the terminus of the Matanuska Glacier has been found to be primarily subaerial in a 100- to 300m wide, ice-cored zone paralleling the edge of the active ice. Certain physical and chemical characteristics of the ice and debris of the superglacial, englacial and basal zones of the glacier indicate the debris of the basal zone, the primary source of sediment, is entrained during freeze-on of meltwater, probably surficially derived, to the glacier sole. Till formation results from the melting of buried ice of the basal zone. Melt-out till inherits the texture and particle orientations of basal ice debris; other properties are not as well preserved. Most deposits result from resedimentation of till and debris by sediment gravity flows, meltwater sheet and rill flow, slump, spall, and ice ablation. Depositional processes are interrelated in the process of backwasting of ice-cored slopes. Sediment flows are the primary process of resedimentation. Their physical characteristics, multiple mechanisms of flow and deposition, and characteristics of their deposits vary with the water content of the flow mass. Deposits of each process are distinguished from one another by detailed analysis of their internal organization, geometry and dimensions, and the presence of other internal and related external features. Genetic facies are defined by these characteristics. The interrelationship of processes develops a composite depositional sequence defined in terms of genetic facies associations: an upper, resedimented facies association, a middle, till facies association, and a lower, subglacial·resedimented facies association. The lateral and vertical distribution of genetic facies within the associations is mainly nonrepetitive. This distribution reflects the variability in sediment and meltwater availability, local and regional slope, location of the active ice margin, and extent and thickness of the sediment cover and buried basal ice. The sequence may vary due to extensive reworking, override of the ice-cored terminus, or changes in the factors listed above. This study implies that previously interpreted tills may be of resedimented origin, multi-till sequences may originate from a single ice advance-retreat cycle, and an exhaustive study of an assemblage of properties of glacigenic materials is required for regional correlation.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:CRREL Report

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