Optical Dating of Deep-Sea Sediments using Single Grains of Quartz: a Comparison with Radiocarbon

Abstract

In this paper, we demonstrate that optical dating of single grains of quartz offers an alternative means of dating deep-sea sediments. The precision and accuracy of the technique, which has the potential to date sediments deposited during the last 500,000 years or so, is limited by the random and systematic uncertainties associated with producing optical ages. These result in total relative age uncertainties of between 10% and 20% at the 68% confidence interval, which are similar in size to those associated with Late Quaternary oxygen-isotope chronologies. We analysed single grains of quartz from several depth intervals down core Fr10/95-GC17, which was collected offshore from Cape Range Peninsula, Western Australia, from a water depth of 1093 m in the eastern Indian Ocean. The single-grain optical ages are shown to be consistent with AMS radiocarbon ages obtained from planktonic foraminifera from the same core. We also show that marine sediments are not immune from partial or heterogeneous bleaching (incomplete resetting) of the optical dating signal. Where partial or heterogeneous bleaching of the optical dating signal is indicated, we recommend that single-grain dating be employed and the burial dose estimated from the population of grains with the lowest absorbed radiation dose.