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 pIRIR 290 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 pIRIR 290 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 (2 D 0 ). Thus for the TT ‐ OSL and pIRIR 290 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.