No abstract

Waikato samples were pre-treated following standard AMS protocols (UCI KCCAMS, 2011a, b). Following pre-treatment, charcoal (∼2 mm fragments) samples were converted to CO2 in sealed quartz tubes by oxidation at 800°C, using pre-baked CuO in the presence of silver wire to absorb any SOx and NOx produced. Shell (< 3 mm fragments, 35-45 mg) were etched in 0.1M HCl at 80°C to remove ∼45% of the surface. Cleaned shells were then tested for recrystallization by Feigl staining (Friedman, 1959) to ensure either aragonite, or a natural aragonite/calcite distribution was present in the shell (e.g. Nerita sp.). CO2 was collected from shells by reaction with 85% H3PO4. Cryogenically separated CO2 was then reduced to graphite with H2 at 550°C using an iron catalyst. δ 13 C was measured either on a LGR Isotope analyser CCIA-46EP or a Thermos Scientific MAT252 IRMS. Pressed graphite was analysed at the Keck Radiocarbon Dating Laboratory, University of California on a NEC 0.5MV 1.5SDH-2 AMS system (Southon et al., 2004). At ANSTO, after visual inspection for the presence of any powdery, potentially extraneous, calcite deposition shell surfaces were physically cleaned by abrasion of 10-25% of thickness with a Dremel ® tool followed by chemical etching of another 10% with 0.5M HCl for 1-5 minutes under sonication at room temperature (Hua et al., 2001). Feigl

No abstract

No abstract

No abstract