Antarctic glacial chronology : new constraints from surface exposure dating

A 14.5 million-year record of East Antarctic Ice Sheet fluctuations from the central Transantarctic Mountains, constrained with cosmogenic <sup>3</sup>He, <sup>10</sup>Be, <sup>21</sup>Ne, and <sup>26</sup>Al

“…Ferrar pyroxene is known to contain a non-zero concentration of non-cosmogenic (presumably magmatic) 3 He. Kaplan et al (2017), Margerison et al (2005), and Ackert (2000) obtained maximum limiting concentrations for noncosmogenic 3 He of 5--7 x 10 6 atoms/g, which are consistent with an unpublished estimate (Balco, unpublished data) of 3.3 ± 1.0 x 10 6 atoms/g. As this is 1.2% of the lowest total 3 He concentration measured in a Roberts Massif erratic in this study, and 0.1 % of the average concentration observed, we disregard it and assume that all observed 3 He in pyroxene is cosmogenic.…”

A 14.5-million-year record of East Antarctic Ice Sheet fluctuations from the central Transantarctic Mountains, constrained with cosmogenic <sup>3</sup>He, <sup>10</sup>Be, <sup>21</sup>Ne, and <sup>26</sup>Al

“…Ferrar pyroxene is known to contain a nonzero concentration of noncosmogenic (presumably magmatic) 3 He. Kaplan et al (2017), Margerison et al (2005), and Ackert (2000) obtained maximum limiting concentrations for noncosmogenic 3 He of 5-7×10 6 atoms g −1 , which are consistent with an unpublished estimate (Balco, unpublished data) of 3.3 ± 1.0 × 10 6 atoms g −1 . As this is 1.2 % of the lowest total 3 He concentration measured in a Roberts Massif erratic in this study and 0.1 % of the average concentration observed, we disregard it and assume that all observed 3 He in pyroxene is cosmogenic.…”

Age and uplift rates of Sirius Group sediments in the Dominion Range, Antarctica, from surface exposure dating and geomorphology

“…Sandstone boulders from the more distal and deeply weathered Dominion moraines (Fig. 3) yield a mean 21 Ne exposure age of 1940 F 100 ka (n = 5) (Ackert, 2000). The moraine crests are roughly parallel to the Beardmore glacier margin and only 130 m of elevation separates the oldest and youngest moraines.…”

“…This drift is typical of cold-based glacial deposits. Surface exposure dating of these drifts on the Mercer Platform indicates that they range from Holocene ( f 10 ka) to late Pliocene (>2 Ma) (Ackert, 2000). These drifts place a minimum age on the underlying Sirius deposits and limits on tectonic uplift during the last 2 Ma.…”