RADIOCARBON AND STABLE ISOTOPE VARIATION IN PRE-BOMB ARGOPECTEN SHELLS FROM PERU: IMPLICATIONS FOR CHRONOMETRY AND THE MARINE RESERVOIR CORRECTION

Peruvian marine upwelling can be variable, causing significant changes in the radiocarbon content of marine organisms and complicating radiocarbon dating of coastal systems. To accurately interpret radiocarbon measurements from either modern or archaeological Peruvian mollusks, the interannual, seasonal, and geographic variations in mollusk shell carbonate radiocarbon must be considered. Here we report full radiocarbon and stable carbon and oxygen profiles along growth axes of Argopecten purpuratus shells collected from coastal Peru during 1908 and 1926. The 1908 shells grew during normal upwelling conditions and the 1926 shells grew during the reduced upwelling of the 1925-6 El Niño/Southern Oscillation (ENSO) event. We discuss the interrelations of these isotopic profiles, the effects of ENSO on the profiles, and implications of the observed radiocarbon variation for reservoir correction measurements.