Dome Fuji Ice Core O2/N2 timescale (DFO-2006), 0-2504 m (0-340 kyr)

DFO-2006 age scale of the Dome Fuji ice core (Antarctica) for 0-2504 m (~340 kyr), based on orbital tuning using O2/N2 ratio of trapped air. The O2/N2 of the Dome Fuji core reflects physical properties of original snow, and its long-term variations are expected to be in phase with summer solstice insolation at the site. We derive chronological tie points between low-pass filtered O2/N2 record and local (77 S) summer solstice insolation curve by peak-to-peak matching, to modify the original glaciological timescale in Watanabe et al. (2003). We can use the O2/N2 data only from the depths in which air is occluded as clathrate hydrates, which restricts the youngest tie point to 82 kyr b2k. The original timescale, which has a constraint at 41 kyr ago, is unchanged for 0-41.5 kyr ago and its agreement with Greenland timescales is probably within 1 kyr. We linearly interpolated the original timescale between all the O2/N2 tie points, as well as between 41.5 and 82 kyr ago. Gas age of the core was derived by subtracting ice age-gas age difference (delta age) from the DFO-2006 ice age, using Pimienta-Barnola densification model (Barnola et al., 1991, Tellus). See reference for further details and uncertainty.