Cosmogenic He-3 data from surface sediments above old buried ice in Beacon Valley, Antarctica

The cosmogenic He-3 data set created during this project provides three major constraints:

*The cosmogenic 3He survey from Mullins Glaciers allows us to calculate for the first time paleo-flow rates of a glacier on the million year time scale. A simple calculation yields a paleo-flow rate of < a few mm y-1 over the last 4 My. This result is in striking agreement with the modern flow rates based on InSar data reported by Rignot et al (Rignot et al., 2002), indicating that Mullins Glacier flow velocity remained relatively constant over millions of years. The finding that a rather sensitive local rock glacier remained dynamically stable over millions of years can only be explained by very consistent climate conditions and the near absence of significant climate changes.

*The depth profile experiment of surface sediment overlying the old buried ice in Beacon Valley indicates (i) that there have been probably some geomorphic processes active in the upper layer of the sublimation tills reworking the simple ‘deeper=older’ stratigraphy; (ii) the cobble survey from the polygon center shows high degree of variety in ‘sublimation age’ and disintegration and weathering characteristics of individual boulders, that is not mirrored by different morphologic appearances of the surfaces (all look old).

* The cosmogenic He-3 chronology from Kennar Glacier is one of the best glacial chronologies ranging from 10,000 to 3,000,000 yr to date, yielding a pulse of small amplitude glaciations 17 ky – 180 ky – 218 ky – 325 ky – 595 ky – 950 ky - ? – 1560 ky – 2900 ky.