Stability of fine-grained TT-OSL and post-IR IRSL signals from a c. 1 Ma sequence of aeolian and lacustrine deposits from the Nihewan Basin (northern China)

We tested the suitability of the fine-grained quartz (4–11 μm) Optical Stimulated Luminescence (OSL) and thermally-transferred OSL (TT-OSL), and the fine-grained polymineral (4–11 μm) post-infrared IRSL (post-IR IRSL or pIRIR) signals for dating samples from aeolian-lacustrine deposits from the Xiaochangliang archaeological profile in the Nihewan Basin, China; these deposits include material from the Jaramillo subchron (c. 1.0 Ma).

In the upper aeolian section, the OSL and pIRIR290 ages are consistent with each other, and show that the upper 8.8 m was deposited between c. 0.3 and c. 140 ka. The luminescence ages indicate a major discontinuity in deposition between the aeolian and the older lacustrine deposits. Below this hiatus at 9.4 m (i.e. in the lacustrine sediments) all three signals are found to be in field saturation (no further systematic increase in burial dose with depth) despite the TT-OSL signal (apparent mean burial dose ~880 Gy) being well below saturation on the laboratory growth curve.

This is in contrast to the pIRIR290 signal, which saturates in the field at a level consistent with laboratory saturation. This results in a practical upper limit to the measured burial dose of ~900 Gy (2D0). Thus for the TT-OSL and pIRIR290 signals, the upper limits for dating lacustrine deposits are <260 ka and c. 240 ka, respectively.

These results have major implications for the appropriate future application of these signals. The ages of our lacustrine samples cannot be regarded as necessarily accurate ones; nevertheless, these ages provide the first long series absolute chronology for study of local palaeolithic and geomorphic evolution history aside from the  magnetostratigraphical results available before this research.