Dating the Raised Beaches:

Some of the beaches in this area have been dated previously using radiocarbon from shells, bones, and other organic remains. There are difficulties in the Antarctic with calibration of these dates due to the long mixing time of Antarctic Ocean water. But they still remain a viable dating tool. This was one method used. Where shells were found to be in situ these have been taken. Two species were found to be dated, Laternula elliptica and Adamussium colbecki . These were only found in the lower energy, sandier beaches.

Lower energy beaches are also ideal sites for the second dating method attempted, that of thermoluminescence dating of sediments. Thermo-luminescence (TL) dating requires sandy material (preferably quartz rich) that has seen sunlight then been buried, such as in a beach ridge. Samples were taken in the sandy ridges and in one site where there were shells, a TL sample was taken alongside. Having the two dating methods in the single place should allow a correlation between the dates obtained. The method for collecting TL samples was changes very little to adapt to Antarctic conditions. Site selection was important as it was impossible to drive a tube to collect sediment into permafrost. A block of wood to place over the end of the tube that could be pounded into slightly frozen ground was useful. We found that if a hole was dug that was suitable, yet frozen, often waiting a day to allow some thawing of the surface layer was enough to get a tube into the sediment. When taking dose rate readings with the gamma spectrometer, to get the probe far enough into the sediment required the use of a small portable hand auger.

The main method of dating used was surface exposure dating using cosmogenic isotopes in the rock platforms associated with the beaches. Cosmogenic isotopes record the build up of cosmogenic radiation from hitting the Earth's surface. If a site has been eroded then exposed at the surface it will start building up the isotopes from the time it was exposed. By collecting surface samples of rock (preferably calcite or potassium rich rocks) a page break time since exposure can be obtained. This part of the coast was ideal for attempting this method as there are rock platforms extending from sea level to the marine limit. Collecting the rock is a relatively simple task of removing a 1 - 2 kg sample from a piece of flat lying rock with chisels and hammers.

No results have been obtained so far on any of the dating methods as the samples are not back from Antarctica at the time of writing, but the surface exposure dating appears to be a promising tool for recording uplift.