Abstract
Tufas, which are freshwater carbonates, are potential archives of terrestrial paleoclimate. Time series of stable isotopic compositions commonly show regular seasonal patterns controlled by temperature-dependent processes, and some perturbation intrinsic to the locality. We examined three tufa-depositing sites in southwestern Japan with similar temperate climates, to understand the origin of local characteristics in the isotopic records. Seasonal change in the oxygen isotope is principally reflected by temperature-dependent fractionation between water and calcite but was perturbed after heavy rainfalls overwhelming the stability of the δ18O value of the groundwater at one site. Isotopic mass balance indicates an undersaturated and relatively small aquifer at this locality. Water δ18O values at the other two sites were stable, reflecting a regular seasonal change in the δ18O value of tufa. Perturbation of the δ13C values in tufa is largely due to CO2 degassing from the stream, which significantly increases the δ13C values of dissolved inorganic carbon (DIC). At a site with remarkably high pCO2 in springwater and a sensitive response of flow rate to rainfall, the amount of CO2 degassing changed distinctly with flow rate. In contrast, the other two sites having low pCO2 springwater reflect a regular seasonal pattern of δ13C in DIC and tufa specimens.
| Original language | English |
|---|---|
| Pages (from-to) | 1684-1695 |
| Number of pages | 12 |
| Journal | Geochimica et Cosmochimica Acta |
| Volume | 73 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - Mar 15 2009 |
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All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology
Cite this
Intra-annual perturbations of stable isotopes in tufas : Effects of hydrological processes. / Hori, M.; Kawai, T.; Matsuoka, J.; Kano, Akihiro.
In: Geochimica et Cosmochimica Acta, Vol. 73, No. 6, 15.03.2009, p. 1684-1695.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Intra-annual perturbations of stable isotopes in tufas
T2 - Effects of hydrological processes
AU - Hori, M.
AU - Kawai, T.
AU - Matsuoka, J.
AU - Kano, Akihiro
PY - 2009/3/15
Y1 - 2009/3/15
N2 - Tufas, which are freshwater carbonates, are potential archives of terrestrial paleoclimate. Time series of stable isotopic compositions commonly show regular seasonal patterns controlled by temperature-dependent processes, and some perturbation intrinsic to the locality. We examined three tufa-depositing sites in southwestern Japan with similar temperate climates, to understand the origin of local characteristics in the isotopic records. Seasonal change in the oxygen isotope is principally reflected by temperature-dependent fractionation between water and calcite but was perturbed after heavy rainfalls overwhelming the stability of the δ18O value of the groundwater at one site. Isotopic mass balance indicates an undersaturated and relatively small aquifer at this locality. Water δ18O values at the other two sites were stable, reflecting a regular seasonal change in the δ18O value of tufa. Perturbation of the δ13C values in tufa is largely due to CO2 degassing from the stream, which significantly increases the δ13C values of dissolved inorganic carbon (DIC). At a site with remarkably high pCO2 in springwater and a sensitive response of flow rate to rainfall, the amount of CO2 degassing changed distinctly with flow rate. In contrast, the other two sites having low pCO2 springwater reflect a regular seasonal pattern of δ13C in DIC and tufa specimens.
AB - Tufas, which are freshwater carbonates, are potential archives of terrestrial paleoclimate. Time series of stable isotopic compositions commonly show regular seasonal patterns controlled by temperature-dependent processes, and some perturbation intrinsic to the locality. We examined three tufa-depositing sites in southwestern Japan with similar temperate climates, to understand the origin of local characteristics in the isotopic records. Seasonal change in the oxygen isotope is principally reflected by temperature-dependent fractionation between water and calcite but was perturbed after heavy rainfalls overwhelming the stability of the δ18O value of the groundwater at one site. Isotopic mass balance indicates an undersaturated and relatively small aquifer at this locality. Water δ18O values at the other two sites were stable, reflecting a regular seasonal change in the δ18O value of tufa. Perturbation of the δ13C values in tufa is largely due to CO2 degassing from the stream, which significantly increases the δ13C values of dissolved inorganic carbon (DIC). At a site with remarkably high pCO2 in springwater and a sensitive response of flow rate to rainfall, the amount of CO2 degassing changed distinctly with flow rate. In contrast, the other two sites having low pCO2 springwater reflect a regular seasonal pattern of δ13C in DIC and tufa specimens.
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UR - http://www.scopus.com/inward/citedby.url?scp=60449095395&partnerID=8YFLogxK
U2 - 10.1016/j.gca.2008.12.024
DO - 10.1016/j.gca.2008.12.024
M3 - Article
AN - SCOPUS:60449095395
VL - 73
SP - 1684
EP - 1695
JO - Geochmica et Cosmochimica Acta
JF - Geochmica et Cosmochimica Acta
SN - 0016-7037
IS - 6
ER -