Dead carbon in stalagmites: carbonate bedrock paleodissolution vs. ageing of soil organic matter. Implications for 13 C variations in speleothems

Genty, Dominique; Baker, Andy; Massault, M.; Proctor, C. J.; Gilmour, Mabs; Pons‐Branchu, Edwige; Hamelin, Bruno

doi:10.1016/s0016-7037(01)00697-4

Cited by 257 publications

(185 citation statements)

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“…The result is an 'apparent' radiocarbon age for the speleothem that may differ significantly from the true radiocarbon age and thus cannot be converted to an age in 'cal yr BP' using the atmospheric 14 C calibration curve. The key concern is that the proportion of radioactively dead carbon at the time of deposition (expressed as the % dead carbon fraction, or DCF) varies from cave to cave (Genty et al, 2001;Oster et al, 2010;Hodge et al, 2011) according to site conditions (e.g. climate, overlying vegetation, karst architecture).…”

Section: Introductionmentioning

confidence: 99%

“…climate, overlying vegetation, karst architecture). Moreover, DCF may fluctuate according to local changes in soilwater-rock interaction Genty et al, 2001) and variations in the age spectrum of soil organic matter (SOM) above the cave (Oster et al, 2010;Fohlmeister et al, 2011a), both of which are controlled by climate.…”

Section: Introductionmentioning

confidence: 99%

“…Other studies have shown that quite large and abrupt shifts in DCF can occur in response to variations in regional climate variability and soil processes above the cave. For example, using a number of speleothems from Europe, Genty et al (2001) demonstrated that those sites with annual temperature amplitudes greater than w7 C exhibited a DCF decrease when temperature increased; they inferred the temperature shifts to reflect changes in SOM turnover rate. In addition, they highlighted a significant positive correlation between d 13 C and DCF, which was interpreted to be a direct consequence of limestone dissolution associated with open-versus closed-system conditions.…”

Section: Introductionmentioning

confidence: 99%

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Hydrological control of the dead carbon fraction in a Holocene tropical speleothem

Griffiths

Fohlmeister

Drysdale

et al. 2012

Quaternary Geochronology

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a b s t r a c tOver the past decade, a number of speleothem studies have used radiocarbon ( 14 C) to address a range of palaeoclimate problems. These have included the use of the bomb pulse 14 C to anchor chronologies over the last 60 years, the combination of U-Th and 14 C measurements to improve the radiocarbon agecalibration curve, and linking atmospheric 14 C 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 14 C, 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 d 18 O, d 13 C and Mg/Ca values), and hence stronger summer monsoon. To explore this relationship, we used a geochemical soil-karst model coupled with 14 C 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 CO 2 , and ultimately led to a greater contribution of dead carbon from the bedrock.Published by Elsevier B.V.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hydrological control of the dead carbon fraction in a Holocene tropical speleothem

Griffiths

Fohlmeister

Drysdale

et al. 2012

Quaternary Geochronology

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“…It is also possible to date meaningfully calcite layers that may have accumulated below or above art, thereby potentially revealing maximum or minimum ages for the associated art (e.g. Beck et al 2001;Genty et al 1999Genty et al , 2001Genty et al , 2004Plagnes et al 2003; see also Chapter 7). Those same calcite deposits can be dated by U/Th, allowing for the useful cross-examination of results.…”

Section: Terra Australis 47mentioning

confidence: 99%

“…In effect, water runoff on rock walls could lead to the dissolution of Uranium and the distortion of age determinations, by making them older than would otherwise be the case (for a recent critical review, see Sauvet et al 2015). One way to verify the validity of U/Th ages is to couple them with other methods such as radiocarbon dating that also allows the dating of calcite subject to minor corrections for 'dead' carbon (Beck et al 2001;Fontugne et al 2013;Genty et al 1999Genty et al , 2001Plagnes et al 2003; see also Chapter 7). At the limestone site of Chauvet Cave in France, speleothems 'growing' at ground level were covered with wood charcoal stains.…”

Section: Uranium-thorium Series Datingmentioning

confidence: 99%