Browsing by Author "Wittmann, H"
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- ItemCosmogenic nuclides constrain surface fluctuations of an East Antarctic outlet glacier since the Pliocene(Elsevier, 2017-12-05) Jones, JS; Norton, KP; Mackintosh, AN; Anderson, JTH; Kubik, P; Vockenhuber, C; Wittmann, H; Fink, D; Wilson, GS; Golledge, NR; McKay, RMUnderstanding past changes in the Antarctic ice sheets provides insight into how they might respond to future climate warming. During the Pliocene and Pleistocene, geological data show that the East Antarctic Ice Sheet responded to glacial and interglacial cycles by remaining relatively stable in its interior, but oscillating at its marine-based margin. It is currently not clear how outlet glaciers, which connect the ice sheet interior to its margin, responded to these orbitally-paced climate cycles. Here we report new ice surface constraints from Skelton Glacier, an outlet of the East Antarctic ice sheet, which drains into the Ross Ice Shelf. Our multiple-isotope (10Be and 26Al) cosmogenic nuclide data indicate that currently ice-free areas adjacent to the glacier underwent substantial periods of exposure and ice cover in the past. We use an exposure-burial model driven by orbitally-paced glacial–interglacial cycles to determine the probable ice surface history implied by our data. This analysis shows that: 1) the glacier surface has likely fluctuated since at least the Pliocene; 2) the ice surface was >200 m higher than today during glacial periods, and the glacier has been thicker than present for ∼75–90% of each glacial–interglacial cycle; and 3) ice cover at higher elevations possibly occurred for a relatively shorter time per Pliocene cycle than Pleistocene cycle. Our multiple-nuclide approach demonstrates the magnitude of ice surface fluctuations during the Pliocene and Pleistocene that are linked to marine-based ice margin variability. © 2017 Elsevier B.V.
- ItemPreliminary results of CoQtz-N: a quartz reference material for terrestrial in-situ cosmogenic 10Be and 26A1 measurements(Elsevier, 2019-10-01) Binnie, SA; Dewald, A; Heinze, S; Voronina, E; Hein, AS; Wittmann, H; von Blanckenburg, F; Hetzel, R; Christl, M; Schaller, M; Léanni, L; ASTER Team; Hippe, K; Vockenhuber, C; Ivy-Ochs, S; Maden, C; Fülöp, RH; Fink, D; Wilcken, KM; Fujioka, T; Fabel, D; Freeman, SPHT; Xu, S; Fifield, LK; Akçar, N; Spiegel, C; Dunai, TJThere is growing interest in geochronological applications of terrestrial in situ-produced cosmogenic nuclides, with the most commonly measured being 10Be and 26A1 in quartz. To extract and then separate these radionuclides from quartz and prepare them in the oxide form suitable for accelerator mass spectrometry (AMS) requires extensive and careful laboratory processing. Here we discuss the suitability of a crushed, sieved and etched, sub-aerially exposed vein quartz specimen (CoQtz-N) to act as a reference material for chemical laboratory preparation and AMS measurements. Splits of CoQtz-N were distributed to eleven target preparation laboratories. The CoQtz-N 10Be targets were then measured at seven different AMS facilities and five of the preparation laboratories had their 26A1 targets measured at four different AMS facilities. We show that CoQtz-N splits are sufficiently homogeneous with regard to nuclide concentrations, that it has been cleaned of any atmospheric derived (i.e. meteoric) 10Be and that it has low concentrations of the major elements that can interfere with Be and A1 extraction chemistry and AMS measurements. We derive preliminary concentrations for 10Be and 26Al in CoQtz-N as 2.53 ± 0.09 × 106 at/g and 15.6 ± 1.6 × 106 at/g, respectively, at the 95% confidence limit. © 2019 Elsevier B.V.