MID-TO LATE-HOLOCENE SEA LEVEL HIGHSTANDS: EVIDENCE FROM FRINGING CORAL REEFS AT QIONGHAI, HAINAN ISLAND
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摘要: 采用精确的高程测量和高精度的TIMS铀系定年方法,对海南岛东部琼海青葛附近低潮时出露的原生死珊瑚和外礁坪上的活微环礁进行调查研究。调查结果表明,青葛附近外礁坪上的微环礁存在狭窄的生长上限(±8cm),位于最低低潮面上,是相当精确的海平面标志物。原生死珊瑚顶面与附近现代活微环礁顶面的高差数据和精确可靠的TIMS铀系年龄数据显示,5500~5200aBP (U/Th年龄,相对于2008年)时海平面至少高出现在(100±8) cm,真实的海平面很可能比现在高2.0~2.2m。总体上,5500~3500aBP期间海平面波动变化,波动幅度约为0.6m,且这种波动与气候波动有较好的对应性。4400~3900aBP期间琼海珊瑚礁的发育缺失很可能与此时的气候干冷有关。Abstract: Systematic field investigation and elevation survey were carried out on emerged primary dead massive corals and sub-tidal living micro-atolls along the coast of Qingge Township, Qionghai City, Hainan Island. Samples collected from these dead massive corals were also dated by the high-precise TIMS Useries method. The results show that:(1)micro-atolls on the outer reef flat at Qingge are precise sea-level indicators because their surface elevations are confined in a narrow range of only 8 cm below the lowest tidal level; (2) paleo-sea-level, indicated by the elevations (as relative to the mean elevation of living micro-atolls) and U/Th ages of primary dead corals, was at least 1 m higher than the present one during the stage 5 500-5 200 years ago, or more likely to be 2.0-2.2 m above the present; (3) paleo-sea-level, which oscillated by up to 0.6 m during the period of 5 500-3 500 aBP, was coincident with climatic changes on the whole; (4) the conspicuous lack of coral growth 4 400-3 900 aBP correlates well with the cold and dry period in south China reflected in speleothem δ180 records from Dongge Cave in Guizhou Province, which coincides with the collapse of the Neolithic Culture of China (NCC).
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Key words:
- coral reefs /
- mid-to late-Holocene /
- high sea level /
- oscillation /
- Qionghai City /
- Hainan Island
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