Replication of Subdecadal Holocene δ18O Records from Borneo Speleothems
Abstract
Speleothems from Gunung Buda National Park, Borneo have the potential to record interannual variability in the oxygen isotopic composition of rainwater related to ENSO. However, kinetic fractionation during carbonate precipitation may overprint any rainwater-driven δ18O signal. Preliminary time-series data from a high growth rate stalagmite (~100 μm/yr) show a correlation between δ18O and δ13C at decadal timescales, a possible indicator of kinetic processes. Although Hendy tests showed no clear pattern in δ18O or δ13C along growth bands, this approach is not a conclusive indicator of equilibrium δ18O precipitation (Dorale and Liu, 2009). To evaluate whether kinetic or equilibrium processes control δ18O variations through time, we developed high-resolution records from two stalagmites. If local kinetic fractionation controls δ18O during carbonate precipitation, then records from two different speleothems are unlikely to resemble each other, whereas if meteoric water controls δ18O in the precipitating carbonate, then records from separate nearby speleothems are likely to covary. We measured δ18O and δ13C in speleothems from Bukkit Assam and Snail Shell caves, Gunung Buda National Park, at a resolution of 4 samples/year, to produce 100-year-long records from ~6500 ya. The timing and amplitude of sub-decadal δ18O variability is very similar in the two records. Precise alignment of the time series requires an age offset of 27 years, well within the ~1% (2σ) uncertainty for the U/Th ages (Partin et al., 2007). Replication of δ18O between caves spatially separated by 6 km strongly suggests that the δ18O variations recorded in these caves reflect the δ18O of meteoric water. Our finding of spatial reproducibility in speleothem δ18O records supports the use of Gunung Buda speleothems as interannual resolution climate archives.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMPP43A1648H
- Keywords:
-
- 4922 PALEOCEANOGRAPHY / El Nino;
- 4924 PALEOCEANOGRAPHY / Geochemical tracers;
- 4958 PALEOCEANOGRAPHY / Speleothems