OPTICAL DATING STUDIES OF QUATERNARY ORGANIC-RICH SEDIMENTS FROM SOUTHWESTERN BRITISH-COLUMBIA AND NORTHWESTERN WASHINGTON-STATE

The suitability of optical dating using 1.4 eV (infrared) excitation f or determining the time of deposition, or compaction, of organic-rich sediments and peat is assessed with measurements on seven samples from six different lithostratigraphic units. One is of zero age, two have associated C-14 ages, three are known to have been deposited during an interglaciation, and one is similar to 1 Ma old. The samples yield sa tisfactory optical ages ranging from 0 to over 100 ka. We conclude tha t the Muir Point Formation (southern Vancouver Island) and the Whidbey Formation (northwestern Washington State) were both deposited during delta(18)O stage 5, as previously deduced from other evidence. The age obtained from the similar to 1 Ma sample was significantly too low. T he optical dating method is simpler and more precise than thermolumine scence dating, and is recommended for future work.