On Correcting 14C Ages of Gastropod Shell Carbonate for Fractionation

Correcting the 14C age of a sample for fractionation is straightforward if the measured carbon was derived entirely from the atmosphere, either directly or through chemical and/or biological reactions that originated with atmospheric carbon. This correction is complicated in the case of gastropods that incorporate carbon from limestone or secondary carbonate (e.g. soil carbonate) during shell formation. The carbon isotopic composition of such gastropod shells is determined by fractionation, as well as mixing of carbon from sources with different isotopic values. Only the component of shell carbonate derived from atmospheric carbon should be corrected for fractionation. In this paper, the author derives a new expression for correcting the measured 14C activity of gastropod shells for fractionation, and describe an iterative approach that allows the corrected 14C activity and the fraction of shell carbonate derived from atmospheric carbon to be determined simultaneously.

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Diet control on carbon isotopic composition of land snail shell carbonate

Chinese Science Bulletin ◽

10.1007/s11434-007-0045-z ◽

2007 ◽

Vol 52 (3) ◽

pp. 388-394 ◽

Cited By ~ 23

Author(s):

ZongXiu Liu ◽

ZhaoYan Gu ◽

NaiQin Wu ◽

Bing Xu

Keyword(s):

Isotopic Composition ◽

Carbon Isotopic Composition ◽

Land Snail ◽

Snail Shell ◽

Carbon Isotopic ◽

Diet Control ◽

Shell Carbonate

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Factors controlling shell carbon isotopic composition of land snail <i>Acusta despecta sieboldiana</i> estimated from lab culturing experiment

Biogeosciences Discussions ◽

10.5194/bgd-11-6555-2014 ◽

2014 ◽

Vol 11 (5) ◽

pp. 6555-6590 ◽

Cited By ~ 6

Author(s):

N. Zhang ◽

K. Yamada ◽

N. Suzuki ◽

N. Yoshida

Keyword(s):

Isotopic Composition ◽

Carbon Isotopic Composition ◽

Land Snail ◽

Egg Laying ◽

Atmospheric Co2 ◽

C4 Plant ◽

C3 Plant ◽

Δ13c Values ◽

Carbon Isotopic ◽

Shell Carbonate

Abstract. The carbon isotopic composition (δ13C) of land snail shell carbonate derives from three potential sources: diet, atmospheric CO2, and ingested carbonate (limestone). However, their relative contributions remain unclear. Under various environmental conditions, we cultured one land snail species, Acusta despecta sieboldiana collected from Yokohama, Japan, and confirmed that all of these sources affect shell carbonate δ13C values. Herein, we consider the influences of metabolic rates and temperature on the carbon isotopic composition of the shell carbonate. Based on previous works and on results obtained in this study, a simple but credible framework is presented for discussion of how each source and environmental parameter can affect shell carbonate δ13C values. According to this framework and some reasonable assumptions, we have estimated the contributions of different carbon sources for each snail individual: for cabbage (C3 plant) fed groups, the contributions of diet, atmospheric CO2 and ingested limestone respectively vary as 66–80%, 16–24%, and 0–13%. For corn (C4 plant) fed groups, because of the possible food stress (lower consumption ability of C4 plant), the values vary respectively as 56–64%, 18–20%, and 16–26%. Moreover, we present new evidence that snails have discrimination to choose C3 and C4 plants as food. Therefore, we suggest that food preferences must be considered adequately when applying δ13C in paleo-environment studies. Finally, we inferred that, during egg laying and hatching of our cultured snails, carbon isotope fractionation is controlled only by the isotopic exchange of the calcite–HCO3−–aragonite equilibrium.

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Factors controlling shell carbon isotopic composition of land snail <i>Acusta despecta sieboldiana</i> estimated from laboratory culturing experiment

Biogeosciences ◽

10.5194/bg-11-5335-2014 ◽

2014 ◽

Vol 11 (19) ◽

pp. 5335-5348 ◽

Cited By ~ 12

Author(s):

N. Zhang ◽

K. Yamada ◽

N. Suzuki ◽

N. Yoshida

Keyword(s):

Isotopic Composition ◽

Carbon Isotopic Composition ◽

Land Snail ◽

Egg Laying ◽

Atmospheric Co2 ◽

C3 Plant ◽

Δ13c Values ◽

Carbon Isotopic ◽

Plant Groups ◽

Shell Carbonate

Abstract. The carbon isotopic composition (δ13C) of land snail shell carbonate derives from three potential sources: diet, atmospheric CO2, and ingested carbonate (limestone). However, their relative contributions remain unclear. Under various environmental conditions, we cultured one land snail subspecies, Acusta despecta sieboldiana, collected from Yokohama, Japan, and confirmed that all of these sources affect shell carbonate δ13C values. Herein, we consider the influences of metabolic rates and temperature on the carbon isotopic composition of the shell carbonate. Based on results obtained from previous works and this study, a simple but credible framework is presented to illustrate how each source and environmental parameter affects shell carbonate δ13C values. According to this framework and some reasonable assumptions, we estimated the contributions of different carbon sources for each snail individual: for cabbage-fed (C3 plant) groups, the contributions of diet, atmospheric CO2, and ingested limestone vary in the ranges of 66–80, 16–24, and 0–13%, respectively. For corn-fed (C4 plant) groups, because of the possible food stress (less ability to consume C4 plants), the values vary in the ranges of 56–64, 18–20, and 16–26%, respectively. Moreover, according to the literature and our observations, the subspecies we cultured in this study show preferences towards different plant species for food. Therefore, we suggest that the potential food preference should be considered adequately for some species in paleoenvironment studies. Finally, we inferred that only the isotopic exchange of the calcite-HCO3−-aragonite equilibrium during egg laying and hatching of our cultured snails controls carbon isotope fractionation.

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Can C3 plants faithfully record the carbon isotopic composition of atmospheric carbon dioxide?

Paleobiology ◽

10.1666/0094-8373(2000)026<0137:ccpfrt>2.0.co;2 ◽

2000 ◽

Vol 26 (1) ◽

pp. 137-164 ◽

Cited By ~ 241

Author(s):

Nan Crystal Arens ◽

A. Hope Jahren ◽

Ronald Amundson

Keyword(s):

Carbon Dioxide ◽

Isotopic Composition ◽

Plant Tissue ◽

Atmospheric Carbon Dioxide ◽

Carbon Isotopic Composition ◽

C3 Plants ◽

Data Set ◽

Carbon Isotopic ◽

C Value ◽

Atmospheric Carbon

Atmospheric carbon dioxide is the raw material for the biosphere. Therefore, changes in the carbon isotopic composition of the atmosphere will influence the terrestrial δ13C signals we interpret. However, reconstructing the atmospheric δ13C value in the geologic past has proven challenging. Land plants sample the isotopic composition of CO2 during photosynthesis. We use a model of carbon isotopic fractionation during C3 photosynthesis, in combination with a meta–data set (519 measurements from 176 species), to show that the δ13C value of atmospheric CO2 can be reconstructed from the isotopic composition of plant tissue. Over a range of pCO2 (198–1300 ppmv), the δ13C value of plant tissue does not vary systematically with atmospheric carbon dioxide concentration. However, environmental factors, such as water stress, can influence the δ13C value of leaf tissue. These factors explained a relatively small portion of variation in the δ13C value of plant tissue in our data set and emerged strongly only when the carbon isotopic composition of the atmosphere was held constant. Members of the Poaceae differed in average δ13C value, but we observed no other differences correlated with plant life form (herbs, trees, shrubs). In contrast, over 90% of the variation the carbon isotopic composition of plant tissue was explained by variation in the δ13C value of the atmosphere under which it was fixed. We use a subset of our data spanning a geologically reasonable range of atmospheric δ13C values (−6.4‰ to −9.6‰) and excluding C3 Poaceae to develop an equation to reconstruct the δ13C value of atmospheric CO2 based on plant values. Reconstructing the δ13C value of atmospheric CO2 in geologic time will facilitate chemostratigraphic correlation in terrestrial sediments, calibrate pCO2 reconstructions based on soil carbonates offer a window into the physiology of ancient plants.

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