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|Title: ||Rainfall variability and temporal changes in the dead carbon fraction in an Indonesian speleothem|
|Authors: ||Hua, Q|
|Issue Date: ||1-Jan-2016|
|Publisher: ||The AQUA Biennial Conference|
|Citation: ||Hua, Q., Griffiths, M., Drysdale, R., Bajo, P., Jenkins, D., Hellstrom, J., Johnson, K., Gagan, M., & Zhao, J. (2016, 5-9 December). Rainfall variability and temporal changes in the dead carbon fraction in an Indonesian speleothem. Papers presented at the AQUA Biennial Meeting, Auckland, New Zealand. Abstract retrieved from http://aqua.org.au/wp-content/uploads/2013/06/AQUA-2016-program-with-abstracts.pdf#page=5&zoom=auto,-46,6.|
|Abstract: ||The number of speleothem-based paleoclimate records has increased significantly in recent
years. To assess the potential hydrological control on speleothem radiocarbon variability, we constructed a high-resolution dead carbon fraction (DCF) record from a speleothem from Flores,
Indonesia for two different periods, the Younger Dryas (YD) chronozone and the Last Millennium. A total of thirty-four 14C analyses were conducted on calcite extracted from U-Th dated stalagmite LR06-B1. To better characterise the paleoclimate and environmental changes, highresolution
stable-isotope (δ18O, δ13C) and trace-element (Mg/Ca, Sr/Ca) measurements were
also conducted along the same stalagmite sections.
Broad comparison of the DCF record with the hydrologically-controlled proxy data suggests that rainfall increases were matched by DCF increases. In line with a previous interpretation of DCF
variability for the same specimen, but during the interval 2.4-2.8 ka and the post-bomb period, we interpret the DCF during the YD and the Last Millennium to have been primarily controlled by limestone dissolution associated with changes in open- versus closed-system conditions, rather
than other potential factors such as kinetic fractionation and/or variations in the age-spectrum of soil organic matter above the cave. It then follows that more abundant monsoon rainfall in Flores resulted in the soil-karst system being in a more closed state, which inhibited carbon isotope
exchange between the karst-water dissolved inorganic carbon and soil-gas CO2, and ultimately led to a greater contribution of dead-carbon from the bedrock.
Our results indicate that DCF in tropical speleothems can be used as a proxy of past rainfall and consequently monsoon variability.|
|Appears in Collections:||Conference Publications|
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