Dating of geochemical events in Lake Bonney, Antarctica, and their relation to glacial and climate changes

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Abstract
Measurements of major ion concentrations, δ18O, and 14C content of the waters of Lake Bonney have enabled a reinterpretation of the geochemical events which have taken place in the lake and enabled the age of some of these events to be estimated. The sequence appears to have been: (1) Flooding of the Bonney basin with sea water about 100 000-300 000 years ago, some time after the last occupation of the lower Taylor Valley by the Taylor Glacier. (2) Evaporation of the West Lobe to near dryness prior to 15000 years B.P. (3) Penetration of the Bonney basin by meltwaters from the Taylor Glacier, and reflooding of West Lobe by meltwaters derived in part from the glacier, about 15 000 years ago. (4) Reflooding of the East Lobe by meltwaters from the Taylor Glacier as long ago as 5000 years B.P., as a result of the glacier reaching a maximum extension close to its present position. (5) Evaporation of East Lobe to a depth of 19 m perhaps as a result of a temporary retreat of the Taylor Glacier, producing a convecting, ice-free, lobe saturated in sodium chloride. (6) Reflooding of East Lobe by meltwaters from the Taylor Glacier overflowing West Lobe as a result of a readvance of the glacier or a decrease in the aridity of the climate. The reflooding began not less than 250 years ago. (7) The Taylor Glacier is currently advancing and occupying part of West Lobe.