a: Measured at the Keck Carbon Cycle Accelerator Mass Spectrometry Facility (UCIAMS), Earth System Science Department, University of California, Irvine, United States of America.b: All raw radiocarbon dates were converted to 2Sigma calendar ages with the CALIB 7.1 software using the MARINE13 calibration dataset without a further adjustment for a regional 14C reservoir age (ΔR, deviation from the average global reservoirage of 400 years).c: 2Sigma enclosing 95.4% of probability distribution.d: The sample contains excess 14C from post AD 1950 atmospheric thermonuclear weapons tests.