Evidence for temporal fluctuations in marine radiocarbon reservoir ages in the Santa Barbara Channel, Southern California

Differences in the ¹⁴C 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 marine ¹⁴C reservoir ages. These fluctuations coincide with δ¹⁸O and δ¹³C shifts measured in Mytilus californianus shells 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 resolution ¹⁴C dating of marine shells may require different ΔR values for different periods of time.