A shift in the South China Sea marine radiocarbon reservoir age associated with the opening of the Balabac Strait

Accurate chronologies are crucial when comparing paleo-climate records, especially in the case of terrestrial and marine comparisons. It is essential to understand temporal variability of the radiocarbon reservoir effect to produce an accurate chronology. Here we establish a high-resolution Bayesian chronology for a northern South China Sea (SCS) sediment core. By applying a piece-wise linear regression method, we observe a distinct shift in the marine radiocarbon reservoir age at ~16.9 ka BP from our core. This shift hampers the accuracy of chronology, even though within higher dating resolution. Together with chronologies within different resolution, we show that the piece-wise linear regression approach is potential in producing accurate chronology for marine sediment. Based on comparisons with other sediment records from the region we show that the shift in radiocarbon reservoir age was pervasive throughout the SCS basin, coeval with the opening of the Balabac Strait, as global sea level rose. Hence, we highlight that the opening of the Balabac strait had a basin-wide effect on surface ocean circulation in the SCS.