Evidence for Temporal Fluctuations in Marine Radiocarbon Reservoir Ages in the Santa Barbara Channel, Southern California

Differences in the14C ages of closely associated marine shell and carbonized plant material from stratified archaeological deposits on San Miguel Island, California, suggest Holocene (10,000–present) fluctuations in marine14C reservoir ages. These fluctuations coincide with δ18O and δ13C shifts measured inMytilus californianusshells from the same stratigraphic contexts and general atmospheric/oceanic circulation models for the region. Based on these data we make three primary observations: (1) significant changes appear to have occurred in the radiocarbon reservoir during the Holocene; (2) these fluctuations appear to correlate with regional oceanographic changes; and (3) high resolution14C dating of marine shells may require different ΔR values for different periods of time.