雷州半岛珊瑚礁记录的全新世11个暖时段年代季温度变化

A detailed study of the Goniopora reef profile at Leizhou Peninsula, the northern coast of the South China Sea suggests that a series of high-frequency, large-amplitude and abrupt cold events occurred during the Holocene Hypsithermal, an unusual phenomenon termed as the "Leizhou Events" in this paper. This period (corresponding to 14C age of 6.2～6.7kaBP or calendar age of 6.7～7.2kaBP), when the climatic conditions were ideal for coral reefs to develop, can be divided into at least nine stages. Each stage (or called a "climate optimum"), lasting about 20 to 50a, was terminated by a abrupt cold nap and (or) a sea-level lowering event in winter times, leading to widespread emergence and death of the Goniopora corals, and growth discontinuities on the coral surface. Such a cyclic process resulted in the creation of a >4m thick Goniopora reef flat. The mean winter and annual SSTs at the coral growth periods might be 21.63 ℃ and 25.55 ℃, respectively, 2.3℃ and 0.7℃ higher than the respective modern values at Leizhou Peninsula (19.33℃ and 24.85℃, respectively) . The mean monthly SST in the coldest months might be 20.9℃. During this period, the crust subsided periodically but the sea level was rising. Our results provide new evidence for high-frequency climate instability in the Holocene Hypsithermal, and challenge the traditional understanding of Holocene climate..Seasonal to monthly resolutionδ18O of mid-Holocene coral Porites lutea in 6691-6682 Cal. a BP, 5822-5818 Cal. a BP and 5009-5000Cal. a BP (TIMS U-Th ages) from Leizhpu Peninsula, northern coast of the South China Sea, indicate that the ocean surface at about 6691-5000 Cal. a BP was 0.3-0.6℃ warmer than that of 1990-1999a AD, the warmest decade of the 21 century, and the seawater enrichedδ18O by 0.14‰-0.24‰. Warmer water temperature enhanced seawater evaporation, so it was overall a warm and aridity period. The summer SST in 6691-6682 a Cal. BP, 5822-5818 a Cal. BP and 5009-5000a Cal. BP were 0.2-1℃ warmer than the 1990s, consequently it nearly went beyond the upper limits of coral growth, and corals in these time grew slowly with average growth rate of 4.3-4.8mm/a, far below that of the 1990s(8.9mm/a). .Using the coral reef and its biological-geological zones as the high sea level indicators, combined with TIMS U-series and 14C ages, we recognize five episodes of sea-level high-stands in the Holocene (7.2-6.7, ~ 5.8, 5.0-4.2, 2.8-2.0, and ~ 1.5 Cal. ka BP), generally matching those indicated by coral reefs from the west coast of the South China Sea (Vietnam) and the Taiwan Strait. From 7.2 to 6.7 Cal. ka BP, the sea level rose at least 3.42m with an average of about 6.8mm/a, and in about 7071 Cal. a BP the sea level got to the present sea level location. The sea level at about 6.7 Cal. ka BP was at least 181.8 cm higher than the present. The sea level rising in the period was disturbed by multiple stops or slightly drops which resulted the coral reef emergence. The modern coral reef geomorphologic framework took its shape during 6.7-7.2 Cal. ka BP..Under the supporting of the funds, a Porites lutea core from Yongshu Reef of Nansha Islands covering 50 years growth history was firstly analyzed for oxygen and carbon isotopic compositions with monthly and seasonally resolution. The calibration of theδ18O with the instrumental temperature indicated that the coral δ18O is a good indicator for sea surface temperature and air temperature. It can be used to reconstruct the SST and air temperature of Yongshu Reef sea area. In addition, the coral δ18O provides signatures for the intensity of the East Asia monsoon and it is a record for the activities of El Nino events. While the coralδ13C can record the sunshine duration, total cloud cover and rainfall, and it also shows significant association to El Nino events. With the calibrated SST and air temperature formulas, the most recent fifty years SST and air temperature were reconstructed based on the coral δ18O, thus backup the understanding of the climate of Nansha Islands to 1950, far beyond the limit of the

以巳经采集到，并巳经开展了T1 MS U-Th定年的雷州半岛全新世11个暖时期的和现代的造礁珊瑚为材料，利用高分辩率（月），稳定同位素（δ18O）分析的方法，定量重建这11个时诘?0个年平均年内和年代际温度变化．.分析时段之多在国际上属罕见．研究结果将为中煌蛞约坝貌煌米柿辖沂镜娜率牢露妊细窠岜忍峁┛煽康那蜃柿希