Stalagmites play an important role in paleoclimatic reconstructions from seasonal to orbital time scales as 230Th-dating can provide an accurate absolute age. Additionally, seasonal trace element and optical layers can provide a precise age. We analyzed the seasonal variability of multiple trace elements on a stalagmite (XMG) in Shihua Cave, Beijing and compared them with results from laminae counting. The results show that (1) the polished section of the topmost part of XMG has obvious bi-optical layers under a conventional transmission microscope, however, laminae are not observed using this method in the rest of the sample, and (2) The variations of P/Ca, Sr/Ca, Ba/Ca, U/Ca and Mg/Ca show seasonal cycles throughout the sample. The PC1 in the Principal Component Analysis (PCA) of five trace elements represents the annual cycle. This stalagmite was deposited over 150 ± 1 years through PC1 peak counting. This result corresponds well with the annual layers and U-Th dating. Trace element cyclicity of PC1 can increase the accuracy of stalagmite dating, especially in the absence of obvious laminae and are a powerful method to identify seasonal changes in a strongly contrasting wet-dry monsoon climate region.
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Many thanks to Binggui Cai for his permission for using map of Shihua Cave, to Haiying Sun, Haijian Chen and Linhua Li at the administrative committee of Shihua Cave for field assistance, and to our collaboration, Jie Guo for her helpful discussions. This work was supported by National Natural Science Foundation of China (NSFC) (Grant No. 41402161) Natural Science Foundation of Shanxi Province, China (Grant No. 2015011085) and the Mark Wainwright Analytical Centre at UNSW, Australia.