Millennial Scale Fluctuations of Dry Valleys Lakes: Implications for Regional Climate Variability and the Interhemispheric (a)Synchrony of Climate Change

This Collaborative Research award supports a project headed by Dr. B. Hall to add to the understanding of what drives glacial cycles near the McMurdo Dry Valleys. Her project aimed to integrate the geomorphological record of glacial history with a series of cores taken from the lake bottoms in the Dry Valleys of the McMurdo Sound region of Antarctica. The chronology, necessary to integrate the cores with the geomorphological record, as well as for comparisons with Antarctic ice-core and glacial records, would come from Uranium-Thorium, Uranium-Helium, and Carbon-14 dating of carbonates, as well as luminescence sediment dating.

This Collaborative award enabled application and tests of a range of luminescence sediment-dating procedures to siliclastic silt and sand fractions from lake cores (Fryxell in Taylor Valley and Vanda in Wright Valley), lake-shore deposits (active deltas), and ice-surface sediment (Vanda and Fryxell). A Supplement to this award enabled similar efforts to be applied to ice-surface and short-core deposits from Lake Hoare (also in Taylor Valley), as well as to paleo-deltas at Lake Fryxell.

The luminescence procedures employed included: multi-aliquot, polymineral fine-silt (IR-stimulation for feldspar signals), single-aliquot, multi-grain sand-size quartz (blue diode stimulation), and single-grain quartz (green laser stimulation). The data set for the Collaborative award will thus include a variety of luminescence age estimates, some compared to independent age estimates (either from C-14 on carbonacious matter or known modern settings [thus of 'zero age']).

The purpose of this data set from the Supplement award was to determine which of these procedures and which of the sediment fractions (each often representing a different depositional process, ergo a different daylight-exposure history, daylight exposure being the 'clock-zeroing' mechanism) would provide the most accurate age estimates for the burial time of the sediment. The purpose of the main Collaborative award data set was to exploit the results from the Supplement experiments to obtain accurate ages of sediment burial for selected horizons within the cores. Unfortunately, several of the cores (e.g., those from Lake Vanda, most from Lake Fryxell) were disturbed during shipment from Antarctic to Reno, thus limiting the number of core samples available for dating analyses.