M.A. Theses: Michael Phillip Richards, 1994

Luminescence Dating of Quartzite From the Diring Yuriakh Site

The lower cultural stratum (stratum 5) at the Diring Yuriakh archaeological site, in Siberia, Russia, contains crude stone tools, which, it has been suggested, were made before the currently accepted earliest occupation of Siberia in the Upper Palaeolithic (ca. 35,000 years ago). The stratum 5 artifacts are mostly quartzites, which contain a great deal of quartz. The artifacts lie on a deflation surface, and show evidence of wind abrasion, so it is likely that they were exposed to sunlight for a period of time before being buried by the overlying sediments. Experiments were undertaken to see if these quartzites could be dated using luminescence dating techniques similar to those that have been used to date the last time quartz grains extracted from sediments were exposed to sunlight. A method was developed to extract quartz grains from the quartzites, layer by layer, using successive 30 minute treatments of 50% hydrofluoric (HF) acid. By comparing the luminescence signal of quartz grains from each layer of quartzite recently exposed to sunlight, it was found possible to determine how deep into the quartzite the sunlight penetrated sufficiently to reduce the luminescence to zero. This allows selection of quartz grains for luminescence dating that should have been exposed to sufficient sunlight in the past. Dating attempts were made on quartzite samples from stratum 5 and stratum 2 ( a deeper non-cultural stratum), and it was found that the traps in the quartz grains were in saturation. After determining the radiation dose required to saturate the traps the dose-rate was calculated for each sample and then minimum age limits were determined. A stratum 2 quartzite was found, using thermoluminescence, to be last exposed to sunlight more than 150 ka ago. A stratum 2 control sample, which was expected to be in saturation on the basis of its supposed age, was found not to be in saturation, and yielded an equivalent dose of 440 90 Gy, using 1.4 eV excitation. The evidence presented for a stratum 5 quartzite suggest it was last exposed to sunlight over 74 ka ago.