Speleothem laminae have been postulated to form annually, and this lamina-chronology is widely applied to high-resolution modern and past climate reconstructions. However, this argument has not been directly supported by high resolution dating methods. Here we present contemporary single-lamina 230 Th dating techniques with 2σ precision as good as ±0.5a yr on a laminated stalagmite with density couplets from Xianren Cave, China, that covers the last 300 years. We find that the layers do not always deposit annually. Annual bands can be under- or over-counted by several years during different multi-decadal intervals. The irregular formation of missing and false bands in this example indicates that the assumption of annual speleothem laminae in a climate reconstruction should be approached carefully without a robust absolute-dated chronology.
Bibliographical noteFunding Information:
We thank H. Liu and C.-C. Wu for their assistance in the field and laboratory. This study was supported by grants from Taiwan ROC NSC (100-2116-M-002-009 and 101-2116-M-002-009, 102-2116-M-002-016 to C.-C.S.), NTU (101R7625 to C.-C.S), NSFC (41272204 to M.T., 41002061 to X.J., and 2013CB955902 to H.C.), and USA NSF (1103403 to R.L.E.).