[U05-P05] High-resolution Holocene records of a stalagmite from maritime Japan
Keywords:Stalagmite, Stable isotope, Trace element, East Asian summer monsoon, Holocene
The ages of the 34-cm-long stalagmite were determined at 17 horizons through Uranium-Thorium dating method at the National Taiwan University. Stable isotopes were measured at 0.2-mm intervals using an isotope ratio mass spectrometer (Thermo Finnigan DeltaPlus) connected with an on-line gas separation and introduction system (GASBENCH II) at the Kyushu University. Trace element analysis was performed with inductivity coupled plasma optical emission spectrometer (iCAP7200, Thermo Fisher Scientific) at the Hiroshima University.
The stalagmite δ18O displays similar temporal patterns with the Chinese records but exhibits much smaller amplitude of δ18O than the Chinese records. This result supports the idea of Mori et al. (2018) that the stalagmite δ18O record from this cave is a superimposed signal of variations in air temperature and seawater δ18O, rather than the hydroclimatic control on meteoric water δ18O . On the other hand, δ13C of the stalagmite has more than 2‰ shift from mid- to late-Holocene with ~1‰ excursions in millennial timescale. The variation synchronized with Mg/Ca suggests that the δ13C change is largely affected by prior calcite precipitation (PCP) from the infiltrating water in the karst bedrock, which generally increases under a dry condition. Supposing that δ13C record of this stalagmite reflects PCP induced by precipitation change, we propose that precipitation or EASM variability is recorded more clearly in δ13C rather than δ18O of stalagmite in maritime Japan.