The techniques of thermal ionization mass spectrometry (TIMS) and multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS) were used for the high-precision timing of the domestic stalagmite standard (GBW04412)

international coral standard (RKM-4) and the Nanhai corals. The results of uranium contents and the ratios of234U/238U and 230Th/234U in the two standards measured by using two techniques were consistent within the error range. Most of the Nanhai corals have less than 3 μg /g of the uranium contents and 150±5 of the δ234U(T) values

which means that the corals have not been subjected to the alternation since they were brought up 7000 years ago

therefore

they preserve the original environmental signals. The age sequence of the corals shows that three events of the high sea level happened in Nanhai area in the periods corresponding to 6799-6307 a B.P.

4472-4285 a B.P. and 1279-1012 a B.P. respectively. The above-mentioned three stages were relative to the Megathermal and Medieval Warm Periods in our country.