Paleoenvironmental changes in the northern East China Sea and the Yellow Sea since the last deglaciation marine transgression

In order to determine the onset of the last deglaciation marine transgression and to reconstruct paleoenvironmental changes during the Holocene, two cores, ECSDP-102 and YMGR-102, were taken from the northern East China Sea off the mouth of the Yangtze River, and from the southern Yellow Sea, respectively. According to AMS ¹⁴C ages the northern East China Sea and the southern Yellow Sea began to have been flooded at about 13.2 ka BP which is in agreement with that in the central Yellow Sea (core CC-02). δ¹⁸O and δ¹³C records of benthic foraminifera Ammonia ketienziensis and δ¹³Corg values provide information on paleoenvironmental changes from brackish (estuarine) to modern marine conditions caused by globally rapid sea-level rise since the last deglaciation. Termination 1 (T1) ended at about 9.0-8.7 ka BP in the southern and central Yellow Sea, whereas T1 lasted until about 6.8 ka BP in the northern East China Sea. This time lag between the two seas indicates that the timing of the post-glacial marine transgression seems to have been primarily influenced by the bathymetry. The present marine regimes in the northern East China Sea and the whole Yellow Sea have been contemporaneously established at about 6.0 ka BP. This is strongly supported by marked changes in occurrence of benthic foraminiferal assemblages, δ¹⁸O and δ¹³C compositions of A. ketienziensis, TOC content and δ¹³Corg values. The δ¹⁸O values of A. ketienziensis show a distinct shift to heavier values of about 1‰ from the northern East China Sea through the southern to central Yellow Sea. The northward shift of ¹⁸O enrichment may reflect gradual decrease of the bottom water temperature in the northern East China Sea and the Yellow Sea.