LAKE SEDIMENTS AND SOILS OF TAYLOR AND WRIGHT VALLEYS, ANTARCTICA

The Antarctic Dry Valleys (ADV) represent a unique analog for Mars as they are extremely cold and dry deserts. Chemistry and mineralogy of lake sediments and soils from Taylor and Wright Valleys were analyzed (Gibson E.K. et al. (1983); Bishop et al. (1996); Bishop et al. (2001); Englert et al. (2012)). Samples from lakes, ponds and their respective vicinity were collected in 1979/1980, from Lake Hoare bottom in 1994/95, and from lake surfaces in 2005/06. Surface samples are from Lakes Brownworth, Vanda and Fryxell; bottom drill cores from Lake Hoare; sediment cores from Lake Hoare, Don Juan and Don Quixote ponds. Systematic analysis by INAA, XRD, VNIR and mid-infrared spectroscopy, and other methods is in progress for all samples.

VNIR spectra of Taylor and Wright Valley lake samples show Fe²⁺ (electronic) pyroxene bands for less altered soils. H₂O, OH bands and CO₃bands are visible in more altered surface sediments. Mid-IR spectra show vibrational bands due to quartz, pyroxene, and feldspar. Orthopyroxene/clinopyroxene ratios are ~40/60 for most samples near Lakes Vanda and Brownworth. Element abundances from each ADV Lake are consistent with variable soil formation and weathering environments. Normalized K/Th ratios have a slightly wider spread than their potential source rocks, but K abundances are higher than those for Mars. To first order, different proportions of the potential source materials can explain the K/Th vs. K pattern for ADV lakes.

Soluble salt depth profiles of Don Juan Pond, Don Quixote Ponds and other locations show high ionic concentrations of NaCl. The next most abundant cation, calcium, is most likely linked to the remaining chloride and sulfate. Magnesium, potassium and nitrate are generally low. Don Juan Pond related dry ponds #4, #3 and #1 profiles demonstrate NO₃^-/Cl^-increases related to increasing elevation. The distribution of ions seems to be dependent on multiple factors including climate, hydrology, and sediment age.

Gibson E. K. et al. (1983) J. Geophys. Res. 88, A912-A928. Bishop J. L. et al. (1996) GCA 60,765-785. Bishop J. L. et al. (2001) GCA 65:2875-2897. Calridge and Campbell (1977) Soil Sci. 123, 377-384. Dehouck E. et al. (2012) GCA 90, 47-63. Englert P. et al. (2012) 43rd LPSC abs. #1743.