Abstract: Background, aim, and scope The determination of the depositional age of Early to Middle Pleistocene is an urgent problem for Quaternary studies, the ESR dating method provides the possibility for the dating of sediment during this period. However, previous works have found that it takes a long time for the signal associated with the titanium (Ti) and aluminum (Al) defects in detrital quartz grains to be reduced to zero or to constant residual value by sunlight exposure, which may cause the phenomenon that the ESR signal of quartz grains is incomplete bleaching prior to sediment deposition. On the other hand, when using ESR signal of quartz for dating, it is difficult to accurately determine whether the ESR signal has been reset to its constant residual value or to zero, moreover, the constant residual value of ESR signal for Al center is difficult to be estimated accurately. Therefore, the reliability by this method remains to be questioned. In this paper, we attempt to identify the best agreement between other age criteria established by Paleomagnetic dating study with observed age and to determine whether ESR dating is reliable. Materials and methods Here we have carried out ESR analyses on five samples with different depths from the BJ14 core drilled from the Baijian Lake in the present Tengger Desert based on Ti-Li signal and Al signal in detrital quartz grains. Results Our results show that: (1) this method yields agreement between the Al signal and Ti-Li signal ages for 2 samples, while Al signal ages were 200—500 ka older than Ti-Li signal for other 3 samples; (2) The dates obtained by this method based on Ti-Li signal are generally consistent with paleomagnetic dating results from BJ14 core and therefore appear to be reliable. Discussion The fact that the Al signal age is older than Ti-Li signal age is probably related to the previous recognition given Al center signal slower bleaching kinetics in comparison with the Ti center. In desert environment, the process of migration or accumulation for aeolian sand is rapid, for which ESR signal of Ti-Li center has been to reset to zero, while incomplete bleaching for ESR signal of Al center. Conclusions Finally, these results demonstrate that a great potential for using Ti-Li centres to date Early Pleistocene deposits, and the usefulness of using the Multiple Centres approach, here, although we only carried out ESR analyses based on two kinds of ESR signals (Ti-Li signal and Al signal) in detrital quartz grains. Meanwhile, we can infer that ESR optical age estimates to be reported as an accurate burial age based on Ti and Al signals should keep agreement between De values for both the Al and Ti signals. And if there is no independent age control, we obtain disagreement between the ages obtained by the two signals, and furthermore the Al signal age is less than that from the Ti signal age, then the Ti signal age can probably be taken as the age of burial. Recommendations and perspectives Our results show that the ESR dating has the potential to date much older deposits, and the importance to measure both Al and Ti centers for dating purpose. We recommend that the MC approach (the multiple center) should be finally very most tested for dating purpose.
Keywords: ESR dating; Al center; Ti-Li center; Tengger Desert