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Inferring sites of subglacial erosion using the Pb isotopic composition of ice-rafted feldspar; examples from the Weddell Sea, Antarctica

M. J. Flowerdew, S. Tyrrell and V. L. Peck
Inferring sites of subglacial erosion using the Pb isotopic composition of ice-rafted feldspar; examples from the Weddell Sea, Antarctica
Geology (Boulder) (November 2012) 41 (2): 147-150

Abstract

The delivery of ice-rafted debris (IRD) from glaciated margins is a function of ice sheet dynamics. Shifts in supply and sourcing of IRD can therefore identify episodes of ice sheet instability; however, records can be difficult to correctly interpret because the subglacial geology of the catchment areas, which controls IRD composition, may be obscured. Importantly, variations can also result from shifts in erosion sites due to changes in the basal ice sheet conditions. This study evaluates where subglacial erosion has occurred in catchments that flow into the southern Weddell Sea, Antarctica, by determining the Pb isotopic compositions of individual ice-rafted feldspars from late Holocene marine sediments. Feldspar compositions match those of rock units inferred (through extrapolation of outcrop, magnetic, and gravity data) to compose areas where ice velocity, bed roughness, and shear stress are high. Significantly, signals from areas where ice velocities are high but bed roughness and shear stresses are low were not recorded, suggesting that there is reduced bedrock erosion in these regions. Major variations in IRD composition in the Weddell Sea can result from changing the loci of subglacial erosion, and do not necessarily correspond with major ice sheet instability.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 41
Serial Issue: 2
Title: Inferring sites of subglacial erosion using the Pb isotopic composition of ice-rafted feldspar; examples from the Weddell Sea, Antarctica
Affiliation: British Antarctic Survey, Cambridge, United Kingdom
Pages: 147-150
Published: 20121113
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 34
Accession Number: 2013-007356
Categories: Quaternary geologyIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2013036
Illustration Description: illus. incl. geol. sketch map
S78°00'00" - S63°00'00", W60°00'00" - W18°00'00"
Secondary Affiliation: University College Dublin, IRL, Ireland
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201305
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