Hydrological control on the dead-carbon content of a tropical Holocene speleothem

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dc.contributor.authorGriffiths, MLen_AU
dc.contributor.authorFohlmeister, Jen_AU
dc.contributor.authorDrysdale, RNen_AU
dc.contributor.authorHua, Qen_AU
dc.contributor.authorJohnson, KRen_AU
dc.contributor.authorHellstrom, JCen_AU
dc.contributor.authorGagan, MKen_AU
dc.contributor.authorZhao, JXen_AU
dc.date.accessioned2020-05-19T01:33:20Zen_AU
dc.date.available2020-05-19T01:33:20Zen_AU
dc.date.issued2012-12-01en_AU
dc.date.statistics2020-05-19en_AU
dc.description.abstractOver the past decade, a number of speleothem studies have used radiocarbon (14C) to address a range of palaeoclimate problems. These have included the use of the bomb pulse 14C to anchor chronologies over the last 60 years, the combination of U-Th and 14C measurements to improve the radiocarbon age-calibration curve, and linking atmospheric 14C variations with climate change. An issue with a number of these studies is how to constrain, or interpret, variations in the amount of radioactively dead carbon (i.e. the dead carbon fraction, or DCF) that reduces radiocarbon concentrations in speleothems. In this study, we use 14C, stable-isotopes, and trace-elements in a U-Th dated speleothem from Flores, Indonesia, to examine DCF variations and their relationship with above-cave climate over the late Holocene and modern era. A strong association between the DCF and hydrologically-controlled proxy data suggests that more dead carbon was being delivered to the speleothem during periods of higher cave recharge (i.e. lower δ18O, δ13C and Mg/Ca values), and hence stronger summer monsoon. To explore this relationship, we used a geochemical soil-karst model coupled with 14C measurements through the bomb pulse to disentangle the dominant components governing DCF variability in the speleothem. We find that the DCF is primarily controlled by limestone dissolution associated with changes in open- versus closed-system conditions, rather than kinetic fractionation and/or variations in the age spectrum of soil organic matter above the cave. Therefore, we infer that periods of higher rainfall resulted in a higher DCF because the system was 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. © 2020 Elsevier B.V.en_AU
dc.identifier.citationGriffiths, M. L., Fohlmeister, J., Drysdale, R. N., Hua, Q., Johnson, K. R., Hellstrom, J. C., Gagan, M. K., & Zhao, J. X. (2012). Hydrological control on the dead-carbon content of a tropical Holocene speleothem. Quaternary Geochronology 14, 81–93. doi:10.1016/j.quageo.2012.04.001en_AU
dc.identifier.govdoc9507en_AU
dc.identifier.issn1878-0350en_AU
dc.identifier.journaltitleQuaternary Geochronologyen_AU
dc.identifier.pagination81-93en_AU
dc.identifier.urihttps://doi.org/10.1016/j.quageo.2012.04.001en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/9462en_AU
dc.identifier.volume14en_AU
dc.language.isoenen_AU
dc.publisherElsevieren_AU
dc.subjectCarbon 14en_AU
dc.subjectIndonesiaen_AU
dc.subjectQuaternary perioden_AU
dc.subjectStable isotopesen_AU
dc.subjectElementsen_AU
dc.subjectMonsoonsen_AU
dc.titleHydrological control on the dead-carbon content of a tropical Holocene speleothemen_AU
dc.typeJournal Articleen_AU
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