- 1Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, China
- 2Department of Geosciences, Princeton University, Princeton NJ, USA
- 3Institute of Oceanography, Shanghai Jiao Tong University, Shanghai, China
- 4State Key Laboratory of Marine Geology, Tongji University, Shanghai, China
- 5Laoshan Laboratory, Qingdao, China
- 6Hefei National Laboratory, Hefei, China
41Ca (half-life = 99 ka) is a cosmogenic radionuclide that has long been proposed as a promising dating tracer for geological and archaeological samples from Middle and Late Pleistocene [1]. Calcium is abundant and has a residence time of 800 ka in the oceans, much longer than the half-life of 41Ca. This has led to the expectation of a uniform distribution of 41Ca/Ca ratios in oceans around the globe. Ocean deposits acquire the global seawater value of 41Ca/Ca upon the initial formation. Since ocean deposits are shielded from cosmic rays by overlying seawater, no cosmogenic 41Ca is produced as deposits grow older. These conditions are ideal for 41Ca dating of marine deposits.
However, the 41Ca/Ca ratio is typically less than 10⁻15 in the environment, posing significant challenges for their measurements. Recent advances in Atom Trap Trace Analysis (ATTA) [2] have enabled the detection of 41Ca in geological samples [3]. The lowest 41Ca/Ca ratio measured so far is 3 × 10−18, found in a foraminifer sample from the Pacific Ocean.
We measured the 41Ca/Ca ratios in seawater samples from various depths in oceans around the world and mapped the spatial distribution of 41Ca. This work identifies the critical initial 41Ca/Ca value for 41Ca dating of marine deposits. Building on these findings, we performed 41Ca dating on foraminifera and coral samples from the Pacific, South China Sea, and Southern Ocean, and compared the results with those obtained from other dating methods. Meanwhile, we are exploring the feasibility of applying 41Ca dating to other geological and archaeological samples.
References:
[1] Raisbeck, G., Yiou, F. Possible use of 41Ca for radioactive dating. Nature 277, 42–44 (1979).
[2] A Primer on Atom Trap Trace Analysis (ATTA). http://atta.ustc.edu.cn/en-us/events/attaprimer.html
[3] Xia, TY., Sun, WW., Ebser, S. et al. Atom-trap trace analysis of 41Ca/Ca down to the 10–17 level. Nat. Phys. 19, 904–908 (2023)
How to cite: Sun, W.-W., Bender, M., Huang, E.-Q., Huang, H., Jiang, W., Lu, Z.-T., Tian, J., Xia, T., Yan, Y.-Z., Yang, G.-M., and Zhu, H.-M.: 41Ca dating of marine deposits from Middle and Late Pleistocene, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4937, https://doi.org/10.5194/egusphere-egu25-4937, 2025.
