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GEOREF RECORD

Assessing ground penetrating radar's ability to image subsurface characteristics of icy debris fans in Alaska and New Zealand

Abstract

Icy debris fans have recently been described as fan shaped depositional landforms associated with (or formed during) deglaciation, however, the subsurface characteristics remain essentially undocumented. We used ground penetrating radar (GPR) to non-invasively investigate the subsurface characteristics of icy debris fans (IDFs) at McCarthy Glacier, Alaska, USA and at La Perouse Glacier, South Island of New Zealand. IDFs are largely unexplored paraglacial landforms in deglaciating alpine regions at the mouths of bedrock catchments between valley glaciers and icecaps. IDFs receive deposits of mainly ice and minor lithic material through different mass-flow processes, chiefly ice avalanche and to a lesser extent debris flow, slushflow, and rockfall. We report here on the GPR signal velocity observed from 15 different wide-angle reflection/refraction (WARR) soundings on the IDFs and on the McCarthy Glacier; the effect of GPR antenna orientation relative to subsurface reflections; the effect of spreading direction of the WARR soundings relative to topographic contour; observed differences between transverse electric (TE) and transverse magnetic (TM) antenna polarization; and a GPR profile extending from the McCarthy Glacier onto an IDF. Evaluation of the WARR soundings indicates that the IDF deposits have a GPR signal velocity that is similar to the underlying glacier, and that the antenna polarization and orientation did not prevent identification of GPR reflections. The GPR profile on the McCarthy Glacier indicates that the shallowest material is layered, decreases in thickness down fan, and has evidence of brittle failure planes (crevasses). The GPR profile and WARR soundings collected in 2013 indicate that the thickness of the McCarthy Glacier is 82 m in the approximate middle of the cirque and that the IDF deposits transition with depth into flowing glacial ice.


ISSN: 1083-1363
EISSN: 1943-2658
Serial Title: Journal of Environmental & Engineering Geophysics
Serial Volume: 23
Serial Issue: 4
Title: Assessing ground penetrating radar's ability to image subsurface characteristics of icy debris fans in Alaska and New Zealand
Title: 9 (super th) international workshop on Advanced ground penetrating radar (IWAGPR2017)
Author(s): Jacob, Robert W.Trop, Jeffrey M.Kochel, R. Craig
Author(s): Giannopoulos, Antoniseditor
Author(s): Diamanti, Nectariaeditor
Author(s): Warren, Craigeditor
Affiliation: Bucknell University, Department of Geology and Environmental Geosciences, Lewisburg, PA, United States
Affiliation: University of Edinburgh, Edinburgh, United Kingdom
Pages: 423-436
Published: 201812
Text Language: English
Publisher: Environmental and Engineering Geophysical Society, Englewood, CO, United States
Meeting name: 9 (super th) international workshop on Advanced ground penetrating radar (IWAGPR2017)
Meeting location: Edinburgh, GBR, United Kingdom
Meeting date: 20170628June 28-30, 2017
References: 14
Accession Number: 2019-005346
Categories: Environmental geologyApplied geophysics
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables, geol. sketch maps
S43°00'00" - S43°00'00", E171°00'00" - E171°00'00"
N59°46'12" - N59°46'12", W150°13'15" - W150°13'15"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, copyright, Environmental & Engineering Geophysical Society. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2019
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