Abstract In order to investigate the relationship between sea-level changes during the Last Glacial Cycle (LGC) and seismic stratigraphic sequences on the NW continental shelf of the South China Sea, a sparker single-channel high-resolution seismic profiling was correlated with a sediment core taken offshore western Hainan Island. Interpretation of the seismic stratigraphy in relation to local and global sea-level changes could be refined. According to the age model, developed from AMS (accelerator mass spectrometry)- 14 C and OSL (optically stimulated luminescence) dates, and δ 18 O (oxygen isotope) stratigraphy, the 88.3 m sediment core reflects environmental change since 110 ka. Correlation with a sediment core in the adjacent basin based on stable oxygen isotope records allows a zonation of the top 15 m of the sediment core and the identification of marine isotope stages (MIS) 1–5e. Seven seismic reflectors interpreted as unconformities were identified. These erosional surfaces have been dated by interpolation using an age–depth model compared to global eustatic curves. The results indicate that seven sea-level cycles can be distinguished in the study area during the LGC, and these are correlated with regional and global sea-level change models. Further research confirms that seismic stratigraphy in the NW South China Sea can be intimately related to LGC sea-level changes associated with regional surface uplift and sediment supply.

Abstract Paralia sulcata (Ehr.) Cleve, a common diatom microfossil species in shelf and adjacent deep-sea sediments, is becoming potentially useful in palaeoenvironmental reconstructions due to its coarsely silicified exoskeleton being well preserved in sediments. This paper presents the distributions of P. sulcata in sediment cores from the SE Asian marginal seas taken from formerly published and original materials. Paralia sulcata achieved variable abundance in the glacial–interglacial sediment analysed, showing spatial changes in the core profiles of the South China Sea, with lower abundances during the last glacial stage and higher values in the post-glacial. Conversely, in the East China Sea, it attains lower abundances during the Holocene, while higher ones in last glacial stage. Over a short timescale, variations in the abundance of this species responded quickly to the climatic and oceanographic fluctuations. We illustrate a ‘seesaw’ effect that its high abundances revealed in the East China Sea at 15–11 cal ka BP, whereas this occurred during period 11–8 cal ka BP in the South China Sea. The rapid increase in abundance of this species in the South China Sea is interpreted as an indication of a plausible link with the opening of the Taiwan Strait and the general coastal water circulation pattern during deglaciation.