USING OSL TO CREATE SEA-LEVEL CURVES IN ANTARCTICA

The purpose of this investigation is to obtain ages from raised-beach deposits along the Antarctic Peninsula using optically stimulated luminescence (OSL). OSL is commonly used for dating sand grains, but its application to dating rock surfaces is relatively new. The basis of OSL measures trapped electron charges within quartz and feldspar crystals that are released upon light stimulation. Methods were developed to isolate quartz grains from the underside of cobbles from raised beach ridges and boulder pavements for OSL measurements. These cobbles were used to construct sea-level curves by determining the last exposure of their concealed side to sunlight. We collected 12 samples from the shores of Maxwell Bay within the South Shetland Islands of the Antarctic Peninsula. 8 of the 12 samples contained enough quartz material for OSL analysis. In conjunction with their elevation, the OSL ages were used to reconstruct sea-levels for the South Shetland Islands. The OSL-derived sea-level curves are in agreement with previously published sea-level curves obtained from the same area. Furthermore, the OSL ages are internally consistent in that ages obtained from higher ridges are always older than ages from lower ridges and ages obtained from the same ridges overlap one another. A modern beach sample was found to be completely bleached, signifying a modern OSL age where no signal remained in the luminescent trap. The use of OSL is shown to be a robust method for dating raised beaches and reconstructing paleo sea levels in areas where material for radiocarbon techniques is problematic or unavailable.