Abstract: Background, aim, and scope Electron Spin Resonance (ESR) dating method is a new dating method developed rapidly in Quaternary chronology in recent decades and has received extensive attention from the Quaternary scholars. The characteristics of ESR signal can be used for source tracing, judging heating time and heating history, and has broad application prospects in Quaternary geology studies. Many studies on ESR dating are mainly focused on the determination of sediment age and dating reliability, but there are less studies on the characteristics of quartz E' center, Ge center, Al center, Ti-Li center, which were directly related to dating. Especially for the signal characteristics of samples subjected to special effects such as high temperature and high dose radiation. In fact, the essential characteristics of the ESR signal directly determine the dating range, experimental procedure and application of the method. Therefore, it is great significance to research the characteristics of ESR signals. Materials and methods Datong volcanic group is in the Datong Basin in the northern part of China. Many researchers have studied this area, the volcanic eruptions in this area lie between Quaternary loess and lacustrine layers. The lacustrine sediment was baked by volcanic lava overlain, and the lava baked lacustrine sediment is ideal for us to study the thermal characteristics of quartz ESR signals in nature. In this paper, the ESR signatures of the lava-baked and unfired lacustrine layers in Datong volcano were studied, and the effects of high-temperature baking on the characteristics of ESR signals and the characteristics of sunlight bleaching in different quartz were summarized. Results It was found that high-temperature baking significantly enhances the sensitivity of the quartz Ti-Li center ESR signal. There is no significant change in the sensitivity of the quartz Al center ESR signal, the sensitivity of the E' center signal increases slightly, and there is no Ge center signal before high-temperature baking. Ge center signal appeared after high temperature baking. The results of the sunlight bleaching experiment showed that after the high-temperature baking effect, the unbleaching part of the Al center was reduced, and the ESR signals back to zero faster. Discussion The increase in the sensitivity of the ESR signals will reduce the relative error of the signal measurement when use the ESR dating. Therefore, the samples which have been baked at high temperatures in the past, the ESR dating may have better results. Conclusions The sensitivity of quartz Ti-Li and E' centers ESR signals enhanced after baked by volcanic lava. The quartz Ge center ESR signal appears after baked by volcanic lava. The Al center sunlight unbleached part decrease after baked by volcanic lava. Recommendations and perspectives When using ESR dating, we must pay attention to the characteristics of various signals and select the appropriate dating signals.
Keywords: ESR; bleaching; heat; volcanic lava; lacustrine sediment