Seabed Prehistory Area 240: Optical Dating of Submarine Cores
Author(s): Dr P S Toms
This study contributes to the Seabed Prehistory Area 240 project, providing Optical age estimates for nine sediment samples obtained from four vibrocores. The time-dependent optically stimulated luminescence signal was calibrated from multi-grain, fine sand aliquots using a single-aliquot, regenerative-dose protocol to provide a measure of natural dose absorption during the burial period. This dosimetry was converted into chronometry by assessing the rate of dose absorption, accounting for litho-cosmogenic emissions along with moisture absorption and grain size attenuation effects. The Optical age estimates generated in this study span from 31 ka (Marine Isotope Stage 2) to greater than 869 ka (Marine Isotope Stage 24). The majority of samples are accompanied by analytical caveats, however all intra-core age estimates are consistent with their relative stratigraphic position. Dose rates are below average for most samples; in such cases age estimates become increasingly sensitive to inaccuracies in Dr as the magnitude of Dr decreases and burial period increases. The reliability of the optical chronology should be measured against any extrinsic temporal control that may be available to the project. If units dated in this study can be shown to be stratigraphically equivalent between cores then it may be possible to assess reliability intrinsically, quantifying the convergence of age estimates from divergent Dr values.
- Report Number:
- 81/2011
- Series:
- Research Department Reports
- Pages:
- 25
- Keywords:
- Geochronology Maritime Optically Stimulated Luminescence
