The sedimentary succession of piston core RC26‐16, dated by 14C accelerator mass spectrometry, provides a nearly continuous palaeoceanographic record of the northeastern South China Sea for the last 15000 yr. Planktic foraminiferal assemblages indicate that winter sea‐surface temperatures (SSTs) rose from 18°C to about 24°C from the last glacial to the Holocene. A short‐lived cooling of 1°C in winter temperature centred at about 11000 14C yr ago may reflect the Younger Dryas cooling event in this area. Summer SSTs have remained between 27°C and 29°C throughout the record. The temperature difference between summer and winter was about ca. 9°C during the last glacial, much higher than the Holocene value of ca. 5°C. During the late Holocene a short‐lived cooling event occurred at about 4000 14C yr ago. Oxygen and carbon isotopic gradients between surface (0–50 m) and subsurface (50–100 m) waters were smaller during the last glacial than those in the Holocene. The fluctuation in the isotopic gradients are caused most likely by changes in upwelling intensity. Smaller gradients indicate stronger upwelling during the glacial winter monsoon. The fauna‐derived estimates of nutrient content of the surface waters indicate that the upwelling induced higher fertility and biological productivity during the glacial. The winter monsoon became weaker during the Holocene. The carbonate compensation depth and foraminiferal lysocline were shallower during the Holocene, except for a short‐lived deepening at about 5000 14C yr ago. A preservation peak of planktic foraminifera and calcium carbonate occurred between 13400 and 12000 14C yr ago, synchronous to the global preservation event of Termination I.

No abstract

The marine Tertiary sequence in the north part of the South China Sea may be divided into 18 Late Oligocene to Pliocene calcareous nannofossil zones and one unnamed Eocene assemblage based on an analysis of calcareous nannofossils from 40 offshore boreholes. The unnamed Eocene assemblage has been found only on the northeast margin of the Zhujiangkou basin. The 18 cakareous nannofossil zones of the Late Oligocene to Pliocene were deposited in succession, but their development degrees are different. Among the 18 calcareous nannofossil zones, those corresponding to Martini's (1971) NN4‐NN5 zones, NN11 zone and NN13‐NN15 zones are well developed, relatively persistent laterally and also widely distributed. They are the important markers for the stratigraphical subdivision and correlation of the Upper Tertiary between the various basins in the north part of the South China Sea. Based on the calcareous nannofossils and the sedimentsry features coup‐led with the foraminifer zonation in certain basins, the present paper discusses the sedimentary characteristics of the marine Tertiary and as well as the distribution and development of the sedimentary hiatus in the region. The calcareous nannofossil markers for the Upper / Lower Tertiary and the Quaternary / Tertiary boundaries, and the characteristics and geological significance of the reworked calcareous nannofossils are also discussed in the paper.