The radiocarbon age of calcite dissolving at the sea floor: Estimates from pore water data

Journal Article · Sat Apr 01 04:00:00 EST 2000 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/S0016-7037(99)00424-X· OSTI ID:20062609

Martin, W R; McNichol, A P; McCorkle, D C

The authors measured the radiocarbon content and stable isotopic composition of pore water and bottom water {Sigma}CO{sub 2}, sedimentary organic carbon, and CaCO{sub 3} at two sites on the Ceara Rise, one underlying bottom water that is supersaturated with respect to calcite (Site B), the other underlying under saturated bottom water (Site G). The results were combined with pore water O{sub 2}, {Sigma}CO{sub 2}, and Ca{sup 2+} profiles (Martin and Sayles, 1996) to estimate the radiocarbon content of the CaCO{sub 3} that is dissolving in the sediment mixed layer. At Site G, the CaCO{sub 3} that is dissolving in the upper 2 cm of the sediments is clearly younger (richer in {sup 14}C) than the bulk sedimentary CaCO{sub 3}, indicating that nonhomogeneous CaCO{sub 3} dissolution occurs there. The case for nonhomogeneous dissolution is much weaker at the site underlying supersaturated bottom water. The results indicate that nonhomogeneous dissolution occurs in sediments underlying under saturated bottom water, that the dissolution is rapid relative to the rate of homogenization of the CaCO{sub 3} in the mixed layer by bioturbation, and that the dissolution rate of CaCO{sub 3} decreases as it ages in the sediment mixed layer. The results support the hypothesis, based on solid phase analyses, that the preferential dissolution of young (i.e., radiocarbon-rich) CaCO{sub 3} leads to a pattern of increasing radiocarbon age of mixed-layer CaCO{sub 3} as the degree of under saturation of bottom water increases (Keir, 1984; Broecker et al., 1991).

• Research Organization: Woods Hole Oceanographic Institution, MA (US)
• OSTI ID: 20062609
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 8 Vol. 64; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
CALCITE
CARBON 14
CARBON DIOXIDE
CARBON SINKS
CLIMATIC CHANGE
DISSOLUTION
INTERSTITIAL WATER
ISOTOPE DATING
SEA BED
SEAS