| A reliable chronological framework is essential for Paleolithic archaeological research, however, complex depositional process may cause significant uncertainties in Optically Stimulated luminescence (OSL) dating. Six OSL samples from the cultural layer of the Shanghu site were dated using single-aliquot regenerative protocol, to analyze the luminescence characteristics and evaluate the signal bleaching by comparing the OSL ages of different grain-size fractions, and to provide time estimation for early human activities. Comparisons among OSL ages of three grain-size fractions (medium or large aliquot) were made based on three samples, and the ages of 4-11, 38-63, and 63-90 μm range at 50-63 ka, 67-78 ka and 71 ~ 94 ka, respectively. Then small aliquot was applied to the coarse fraction of all the six samples. Their diverse equivalent doses demonstrate the sediments were insufficiently bleached, and the ages of SH01 to SH06 were calculated by minimal age model as 4.1 ± 0.9 ka, 6.8 ± 1.9 ka, 32 ± 4 ka, 47 ± 8 ka, 28 ± 4 ka and 28 ± 4 ka, respectively. These ages based on small aliquot are much younger that the results from medium or large aliquot, demonstrating that all the fine, medium and coarse fractions of sediments in this site were poorly bleached. The minimal ages of coarse-grained fraction suggest the prehistoric human occupied this region since ca. 30 ka, no early than 47 ka. However, this time estimation might be still overestimated. |
