Paleolimnology of perenially ice-covered Antarctic oasis lakes

Paleolimnological investigations were carried out on perennially ice-covered lakes of the Bunger Hills Oasis {dollar}(66spcirc 15sp{lcub}prime{rcub}{dollar}S; {dollar}100spcirc 45spprime{dollar}E) and the McMurdo Dry Valleys {dollar}(77spcirc 30spprime{dollar}S; {dollar}162spcirc 00spprime{dollar}E) of Antarctica. The lacustrine carbon reservoir effect was assessed by {dollar}sp{lcub}14{rcub}{dollar}C dating various modern carbon reservoirs. It was discovered that modern surface waters in some dry valley lakes have no reservoir effect. Old ages of lake bottom water reflect whatever the age of the inflowing water is plus the actual age of the bottom water which in some cases exceeds 10,000 years. It was concluded that nearshore and lake bottom sediments can be effectively dated with {dollar}sp{lcub}14{rcub}{dollar}C of microbial mats, but paleolake deposits can not be reliably dated without accounting for the age of the bottom water. We tested several other techniques (thermoluminescence, paleomagnetism, {dollar}sp{lcub}137{rcub}{dollar}Cs, {dollar}sp{lcub}210{rcub}{dollar}Pb) for their ability to correct the {dollar}sp{lcub}14{rcub}{dollar}C age and/or to be used on their own to obtain suitable chronologies. Thermoluminescence holds the most promise for using in conjunction with {dollar}sp{lcub}14{rcub}{dollar}C to obtain suitable dates from paleolake deposits.; The modern {dollar}rmdeltasp{lcub}13{rcub}C{dollar} signature in McMurdo Dry Valley lake deposits (carbonates and organic matter) was appraised in order to strengthen inference that can be made from ancient deposits. The 24 hours of sunlight during the austral summer and perennial ice covers create a diffusion-limited situation with respect to CO{dollar}sb2{dollar} in lake bottom microbial mats (i.e. CO{dollar}sb2{dollar} is diffused into the mat at a rate less than demand) in the near-shore moat and just below the perennial ice covers. This causes the mats not to discriminate among the different carbon isoptopes as much, reducing fractionation during photosynthesis. Ancient lake sediments were investigated to assess the significance of varying {dollar}rmdeltasp{lcub}13{rcub}C{dollar} values with respect to the dry valley paleoenvironment, and to an analog of the dry valleys--ancient Mars. Lacustrine sand mounds formed by former ice-covered lakes were deemed the most suitable paleolake deposits for extracting the best information about a lake's environmental history.; The general concepts developed in the McMurdo Dry Valleys were tested in another region of the Antarctic, Bunger Hills Oasis. White Smoke Lake, a perennially ice-covered lake in the Bunger Hills, also has diffusion-limitation of CO{dollar}sb2{dollar} in the microbial mat. In contrast to the McMurdo Dry Valley lakes, Cs{dollar}sp{lcub}137{rcub}{dollar} and {dollar}sp{lcub}210{rcub}{dollar}Pb were found to be much more effective for sediment dating in this lake.