Paper No. 9
Presentation Time: 10:25 AM
SOIL INDICATORS OF PALEOCLIMATE IN THE DRY VALLEYS, ANTARCTICA
DICKINSON, Warren W.1, SCHILLER, Martin
2, DITCHBURN, R.G.
3, GRAHAM, I.J.
3 and ZONDERVAN, A.
3, (1)Antarctic Research Center, Victoria University Wellington, PO Box 600, Wellington, 6040, New Zealand, (2)School of Geography, Environment and Earth Sciences, Victoria University Wellington, PO Box 600, Wellington, 6040, New Zealand, (3)Institute of Geological and Nuclear Sciences, P.O.Box 31-312, Lower Hutt, New Zealand, Warren.Dickinson@vuw.ac.nz
Conflicting evidence exists for paleoclimate over the past 15 million years in the McMurdo Dry Valleys. A large body of stratigraphic and geomorphic evidence indicates that cold, dry polar conditions have existed at high (>1000m) elevations in the Dry Valleys for the past 12.5 Ma and that warmer and wetter conditions existed prior to this time. Recently, cores from Andrill 1A have shown that the Ross Sea was probably open, under warm conditions 4-8 Ma. How these two distinct paleoenvironments co-existed is not clear, but in the Dry Valleys, ancient soils with several proxy indicators of climate may help to resolve this problem.
Clays bound with atmospheric 10Be are prevalent in many soil profiles in the Dry Valleys. Work on the Hart ash in the Wright Valley has shown that these particles, which are now frozen in place, were illuviated by percolating water from the surface to their present depth in the soil. The illuviation of clay requires significantly more water than presently available in the Dry Valleys. In the Wright Valley, this ‘wet period’ is bracketed between 3.9 Ma, the age of the Hart Ash, and 10 Ma, the detection limit of 10Be in the soil.
In other parts of the Dry Valleys, profiles with atmospheric 10Be suggest the soils became permanently frozen around 6 Ma. By sampling soils at a variety of altitudes and locations we may, in the future, build up a better picture of the transformation from sub polar to polar conditions in the Dry Valleys.
