|
|||||
|
|
Carbon and oxygen isotope fractionation in non-marine ostracods: results from a ‘natural culture’ environment |
|
| Authors: | KW Keatings THE HeatonJA Holmes |
| Institution: | 1 School of Earth Science and Geography, Kingston University, Penrhyn Road, Kingston upon Thames, Surrey, KT1 2EE, UK 2 NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK 3 Environmental Change Research Centre, University College London, 26 Bedford Way, London, WC1H 0AP, UK |
| Abstract: | Carbon and oxygen isotope analysis of ostracods living in the near-constant conditions of spring-fed ponds in southern England allowed accurate determination of the ostracod’s calcite-water 13C/12C and 18O/16O fractionations. The 13C/12C fractionations of two species, Candona candida and Pseudocandona rostrata, correspond to values expected for isotopic equilibrium with the pond’s dissolved inorganic carbon at the measured temperature (11°C) and pH (6.9), whilst those of a third species, Herpetocypris reptans, would represent equilibrium at a slightly higher pH (7.1).The 18O/16O fractionations confirm two previous studies in being larger, by up to 3‰, than those ‘traditionally’ regarded as representing equilibrium. When the measured fractionations are considered in the context of more recent work, however, they can be explained in terms of equilibrium if the process of calcite formation at the ostracod lamella occurs at a relatively low pH (≤7) irrespective of the pH of the surrounding water. The pH of calcite formation, and therefore the calcite-water 18O/16O fractionation, may be species and stage (adult versus juvenile) specific, and related to the rate of calcification. |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ | |