干旱区生态环境知识资源中心

We tested the feasibility of dating freshwater and terrestrial molluscs from the semiarid and arid zone in China, since these types of shell material deposit only aragonite to form their shell structure, and shell integrity can be easily observed using X-ray diffraction. We also tested the possibility of estimating microenvironmental changes from shell delta(13)C values, but variations within shell populations preclude the use of these values as a reliable indicator. Reservoir ages were calculated for living shells of the same species as fossil shells by using their measured C-14 ages, which were recalculated using an average value of atmospheric C-14 activity for the years spanning their time of collection as the modern standard. The results indicate that freshwater and terrestrial shells are potentially useful as dating material, provided extreme care is taken in their collection and other datable material (in this case wood and pollen) is within the profile to act as a comparison.