Paleolimnology of the McMurdo Dry Valleys, Antarctica.

摘要: The McMurdo Dry Valleys presently contain more than 20 permanent lakes and ponds, which vary markedly in character. All, with the exception of a hypersaline pond, have perennial ice-cover. dry valley lakes, other ice-free regions continental Antarctica, are unique on this planet that they consistently maintain thick year-round ice cover (2.8-6.0 m) over liquid water. persistent covers minimize wind-generated currents reduce light penetration, as well restricting sediment deposition into lake exchange atmospheric gases between water column atmosphere. From paleolimnological perspective, offer an important record catchment environmental changes. These also modern-day equivalents periglacial were common during glacial periods at temperate latitudes. present mostly remnants larger occupied valleys past, perhaps up to 4.6 Ma ago. Two evidence being filled large within last 10000 years. Repeated drying filling events since then left characteristic impression salt profiles some creating paleo-indicator column. marked sediments by concentration dilution certain chemical constituents, particularly salts, corroborated carbonate speciation oxygen isotope analysis. Stratigraphic analysis is made difficult occurrence 'old carbon' reservoir spurious radiocarbon dates, high degree spatial variability sedimentation. biological relatively simple, containing various taxa planktonic benthic microorganisms, but no higher forms life, advantage paleolimnologists because there bioturbation sediments. Useful paleo-indicators found include cyanobacterial filament sheaths, diatom frustules eukaryotic algal cells, protozoan cysts, photosynthetic pigments, minerals (e.g. carbonates) associated microbial activity. Future work will benefit from fully characterizing connection covers, conditions, paleo-indicators, thereby allowing refinement inferences concerning paleoenvironment. New dating techniques need be tested environment overcome problems dating. establishment detailed focused campaign proposed.