The 16th International Conference on Accelerator Mass Spectrometry

210Po, AMS 14C, 230Th/U dating and stable C/O isotope records of two stalagmites from South Ural, Russia

PSA-2

21 Oct 2024, 17:15

20m

Lobby and Hallway , 2nd Floor (( Poster session A should be set up in the morning.))

Poster Applications in Archaeology Poster Session A

Speaker

Mr Hao-Ting Chiu

Description

210Po, AMS 14C, 230Th/U dating and stable C/O isotope records of two stalagmites from South Ural, Russia

Hao-Ting Chiu1, Hong-Chun Li1,*, Tzu-Tsen Shen1, Dilyara Kuzina2, Satabdi Misra1, Horng-Sheng Mii 3, Lisheng Wang4, Zhibang Ma4

1. Department of Geosciences, National Taiwan University, Taipei 10617, Taiwan, ROC (hcli1960@ntu.edu.tw)
2. Institute of Geology and Petroleum Technologies, Kazan (Volga Region) Federal University, Kazan 420008, Russia (di.kuzina@gmail.com)
3. Department of Earth Sciences, National Taiwan Normal University, Taipei 11677, Taiwan, ROC (t44006@ntnu.edu.tw)
4. Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China (wangls@mail.iggcas.ac.cn)

Two stalagmites from Ikenskaya Cave and Oktyabrskaya Cave respectively were collected from south Ural Mountains in Russia in 2022. IKEN-1 from Ikenskaya Cave (54o43’1’’ N, 57o18’25’’ E) is 11.5 cm long and OTAR-1 from (54°10'09.7"N, 56°50'56.5"E) is 20.1 cm long. 210Pb (vis 210Po) dating indicates that IKEN-1 stopped growth before 200 years, whereas OTAR-1 continuously grew to the present. The 230Th/U dating results with large uncertainties and reversed age sequences due to low 238U but high 232Th contents. With high-resolution 14C dating, a total of 17 14C ages in IKEN-1 show stratigraphic order from 61535 Cal yr BP in the surface (1.25 mm) to 3515135 Cal yr BP (105 mm) at the bottom. Three available 230Th/U ages of IKEN-1 are similar to the 14C ages from the same samples, indicating negligible dead carbon influence (DCI) on the 14C ages. Based on the 17 14C ages, the chronology of IKEN-1 has been established by Bacon model. A total of 1155 samples from IKEN-1 have been measured for 18O and 13C, which allow us to reconstruct high-resolution paleoclimatic variations in the studying area during 590~3640 Cal yr BP. The 19 14C ages in OTAR-1 are generally in stratigraphic order from 85075 Cal yr BP in the surface (1.25 mm) to 6640135 Cal yr BP (195 mm) at the bottom, showing that the DCI on the 14C ages is relatively constant. As 210Po dating shows that the surface of this stalagmite is modern, the DCI on the 14C ages in OTAR-1 exists. The Three available 230Th/U ages of OTAR-1 are about 1000 years than the 14C ages from the same samples. We use the average of five 14C ages in the upper 6.25 mm as the DCI age which is 922 years. Subtracting this DCI age of 922 years from each 14C ages, the corrected 14C ages contain the least DCI. Using those corrected 14C ages, the chronology of OTAR-1 has been established by Bacon model. The dating results not only agree with the available 230Th/U ages, but also exhibit a growth hiatus between 200 and 1500 Cal yr BP. A total of 2009 subsamples from OTAR-1 are measuring 18O and 13C, which will provide paleoclimate records since 5590 Cal yr BP.

Keywords: Stalagmite, South Ural Mountain, AMS 14C dating, 210Po and 230Th/U dating, stable isotope records