[H-QR06] Innovative applications of luminescence and ESR dating to geosciences

[HQR06-02] Optically stimulated luminescence dating of feldspar from fluvial terrace deposits formed during the last glacial period

*Hayashizaki Ryo¹ (1.Central Research Institute of Electric Power Industry)

Optically Stimulated Luminescence (OSL) dating is a pivotal method for determining the depositional chronology of quartz and feldspar since their last solar exposure. Recent advancements in OSL dating techniques for feldspar, particularly the development of post-infrared infrared stimulated luminescence (pIRIR) dating have expanded the depositional age determinations to encompass the last several hundred thousand years. However, OSL dating of feldspar is still in its infancy, and it remains uncertain whether accurate ages can be obtained depending on the depositional process and types of feldspar. This study conducted pIRIR dating to verify whether consistent ages can be obtained from fluvial terrace deposits formed during the last glacial period in the Obanazawa Basin, Yamagata Prefecture, Japan.
The samples (ρ= 2.53~2.58 g/cm3) lacked potassium feldspar, predominantly comprising quartz with minor plagioclase. The application of pIR200IR290 dating proved unsuccessful in measuring OSL signals within specific samples. This result indicated that pIR200IR290 dating is not suitable for samples devoid of potassium feldspar. Despite inferring that the samples had sufficient exposure to sunlight, the ages obtained from pIR50IR290 and pIR200IR290 methods were older than expected. OSL dating of feldspars has predominantly concentrated on potassium feldspar, suggesting that extending OSL dating to encompass plagioclase within fluvial terrace deposits presents a challenge.