Rapid trace element analysis of speleothems by ELA-ICP-MS

Excimer laser ablation inductively coupled plasma mass spectrometry (ELA-ICP-MS) has been used to analyse the concentration of Mg, Sr, Ba, and U along the outer wall of a soda-straw stalactite from southeastern Australia. The results of this study reveal high frequency oscillations superimposed upon longer-term trends in the data, in particular those of Sr/Ca and Ba/Ca. The high frequency oscillations in the trace elements are assumed to be annual and have been used to compile a chronology which agrees to better than 1% of an independent chronology based on dendrochronological counting of distinctive banding on the surface of the speleothem. The autocorrelation and dendrochronological methods produce a 230-year record of trace element fluctuations spanning the period from 1766 to 1996. Comparisons between the speleothem trace element record and ring width measurements to regional precipitation and temperature fluctuations reveal that a complex relationship exists between them. This study demonstrates that analysis of the trace element composition of soda-straw stalactites is possible at sub-annual resolution, and that some trace elements in these speleothems can vary significantly on an annual basis in an apparent response to changing environmental conditions. The study also reveals the significant advantages that ELA-ICP-MS has over other microbeam techniques in regard to the relative speed and ease of acquiring data with minimal sample preparation.