科研之友
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摘要
Optically stimulated luminescence (OSL) measurements are reported for single aliquots and single grains of quartz from sedimentary deposits within Cave 13B at Pinnacle Point, South Africa (PP13B). Ages have been obtained for 30 samples from the Middle Stone Age and from sterile geological deposits at the base and top of the sediment sequence. The ages for all the archaeological units have been obtained from single-grain measurements that enable unrepresentative grains to be rejected after they have been scrutinized for their OSL behavior. The shape of the equivalent dose distribution and the degree of spread in equivalent dose for each sample have also been scrutinized for evidence of depositional and post-depositional effects that can influence the accuracy of the age estimates. This study also used the same systematic approach as that used for the dating of the Howieson's Poort and Still Bay in South Africa. This single-grain approach results in more accurate and precise age estimates that place all ages measured and analyzed in this way on a common timescale. Four periods of human occupation have been dated to similar to 162 ka, similar to 125 ka, similar to 110 ka, and similar to 99-91 ka during Marine Isotope Stage (MIS) 6, 5e, 5d, and 5c, respectively. Occupation of the site appears to have occurred at periods of higher sea level and increased aeolian activity, and the cave was ultimately sealed by the accumulation of a large dune similar to 90 ka ago that infilled the cave, but also blanketed the cliff face above the cave, thus preventing further habitation of the site until 39 ka.
- 出版日期2010-10
