Late Quaternary lakes in the McMurdo Sound region of Antarctica

Lake levels within the enclosed drainage basins of the Dry Valleys adjacent to McMurdo Sound have fluctuated widely during the Late Quaternary due to (a) local climate change and the consequent variation in the evaporation-pr ecipitation regime, and (b) glacial fluctuations, resulting in changes in t he catchment and meltwater drainage areas of the glaciers and, in some case s, in the volumes of the available lake basins. Three types of lakes can be distinguished on the basis of their water source: (1) lakes receiving the bulk of their water from melting of local alpine glaciers; (2) proglacial l akes associated with outlet glaciers from the East Antarctic Ice Sheet; (3) proglacial lakes associated with the marine oxygen-isotope stage 2 Ross Se a ice sheet and its precursors. The Dry Valleys contain an exceptionally long lacustrine record, extending back at least 300,000 years. Lacustrine sedimentation is cyclical, occurrin g over periods of about 100,000 years. During the last such cycle, relative ly small lakes, both adjacent to East Antarctic outlet glaciers and fed by meltwater from alpine glaciers, existed during stage 5. However, these loca l lakes gave way to large proglacial lakes adjacent to the Ross Sea ice she et in stage 2. The same relationship apparently occurred during the previou s 100,000-year cycle. Dating of lacustrine sediments suggests that lakes pr oglacial to the Ross Sea ice sheet have existed during episodes of sea-leve l lowering during global glaciations. Lakes pro,olacial to outlet glaciers from the East Antarctic Ice Sheet have formed coincident with episodes of h igh eustatic sea fever during interglacial periods.