A comparison of sediment accumulation chronologies by the radiocarbon and 230Thexcess methods

Four Northeast Atlantic cores which exhibited well-correlated linear progressions of conventional radiocarbon age with depth were analysed to provide 230 Th-excess profiling data. The current evaluation of marine radiocarbon data suggests that conventional radiocarbon ages consistently underestimate true time. This deficit progressively increases from 4 to 22 ky BP. As a result, steady-state sediment accumulation rate models based on conventional radiocarbon ages are expected to be in error by up to 17%, dependent on the period over which the estimates are made. When proxy timescales from the radiocarbon and Th-230(excess) data for the four cores are compared over periods between 0-11.5 and 0-18.2 ky BP, the trend of cumulative time derived from the Th-230(excess) profiling data is shown to be consistent with the expected trend of conventional radiocarbon age vs the best current estimate of true time. This agreement supports the use of Th-230(excess) tracer for detailed estimates of changing deep-sea sediment accumulation fluxes.