The Use of Molluscan Shell Biogeochemistry in Environmental Reconstruction

Paleoclimate science, Biogeochemistry, Paleontology, Geochemistry, Paleoecology

Mitchell, Lynda

University:University of Glasgow

关键词: Paleoclimate science, Biogeochemistry, Paleontology, Geochemistry, Paleoecology;   

Others  :  http://theses.gla.ac.uk/74671/1/10992293.pdf

来源: University of Glasgow

【 摘 要 】

Stable carbon and oxygen isotope analysis of fast growing carbonate shells of fossil molluscs from the Plio-Pleistocene of New Zealand and Recent species from Scotland has revealed a high degree of isotopic variability and a strong correlation between delta13C and delta138C in each case. This phenomenon may be due to kinetic isotope effects which are inherent in fast growing shells or areas of shell. If this is the case then equilibrium isotope partitioning may not have had time to occur before the completion of calcite precipitation. Kinetic effects would favour the lighter isotopes of both carbon and oxygen; it is therefore the highest delta13C and delta138C values that are most likely to reflect equilibrium with the environment. Very small carbonate particles often give particularly low delta13C and delta138C values. These results have implications for the use of isotopic data in environmental reconstruction based on fast growing shells and may also be applicable to other carbonate precipitating organisms. Stable isotope analysis of a series of fossil and recent mollusc shells from interglacial shell beds near Wanganui, New Zealand, yielded interglacial palaeotemperatures spanning the past 3.6 million years. The results indicate a cooling of about 10