Meteoric 10Be as a tracer of subglacial processes and interglacial surface exposure in Greenland

QUATERNARY SCIENCE REVIEWS

卷:191

Article

Graly, Joseph A.¹  Corbett, Lee B.²  Bierman, Paul R.²  Lini, Andrea²  Neumann, Thomas A.³ 

[1] Indiana Univ Purdue Univ, Dept Earth Sci, Indianapolis, IN 46202 USA

[2] Univ Vermont, Dept Geol, Burlington, VT USA

[3] NASA, Goddard Space Flight Ctr, Greenbelt, MD USA

关键词: Quaternary;    Interglacials;    Glaciation;    Glaciology;    Greenland;    Cosmogenic isotopes;    Stable isotopes;   

DOI  :  10.1016/j.quascirev.2018.05.009

来源: Elsevier

【 摘 要 】

In order to test whether sediment emerging from presently glaciated areas of Greenland was exposed near or at Earth's surface during previous interglacial periods, we measured the rare isotope Be-10 contained in grain coatings of sediment collected at five ice marginal sites. Such grain coatings contain meteoric Be-10 (Be-10(met)), which forms in the atmosphere and is deposited onto Earth's surface. Samples include sediment entrained in ice, glaciofluvial sediment collected at the ice margin, and subglacial sediment extracted during hot water drilling in the ablation zone. Due to burial by ice, contemporary subglacial sediment could only have acquired substantial Be-10(met) concentrations during periods in the past when the Greenland Ice Sheet was less extensive than present. The highest measured Be-10(met) concentrations are comparable to those found in well-developed, long-exposed soils, suggesting subglacial preservation and glacial transport of sediment exposed during preglacial or interglacial periods. Ice-bound sediment has significantly higher Be-10(met) concentrations than glaciofluvial sediment, suggesting that glaciofluvial processes are sufficiently erosive to remove tracers of previous interglacial exposures. Northern Greenland sites where ice and sediment are supplied from the ice sheet's central main dome have significantly higher Be-10(met) concentrations than sites in southern Greenland, indicating greater preglacial or interglacial landscape preservation in central Greenland than in the south. Because southern Greenland has more frequent and spatially extensive periods of glacial retreat but nevertheless has less evidence of past subaerial exposure, we suggest that Be-10(met) measurements in glacial sediment are primarily controlled by erosional efficiency rather than interglacial exposure length. (C) 2018 Elsevier Ltd. All rights reserved.

【 授权许可】

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