永暑礁西南礁镯生物地貌与沉积环境  

NEW INSIGHTS INTO BIOLOGICAL-GEOMORPHOLOGICAL-SEDIMENTARY ZONES AND ENVIRONMENT RECORDS AT THE SOUTHWEST REEF BRACELET OF YONGSHU REEF, NANSHA ISLANDS

作　　者：余克服[1] 赵建新 施祺[1] 钟晋梁[1] 陈特固[1] 

机构地区：[1]中国科学院南海海洋研究所 [2]DepartmentofEarthSciences,UniversityofQueensland,Brisbane

出　　处：《海洋地质与第四纪地质》2003年第4期1-7,共7页Marine Geology & Quaternary Geology

基　　金：科技部"十五"社会公益专项"南沙群岛及其邻近海

摘　　要：在海上系统调查的基础上提出南沙群岛永暑礁西南部礁镯并非传统的开放型环礁,而是一个封闭型的小环礁,封闭的泻湖能够为高分辨率古环境重建提供原生生物沉积。该小环礁可分为礁前斜坡活珊瑚林带、外礁坪珊瑚生长带、礁突起珊瑚枝块胶结堆积带、内礁坪枝状珊瑚生长—砂质沉积交互带、泻湖坡枝状珊瑚生长—细砂沉积带和泻湖盆底粉砂质生物沉积带共6个生物地貌和沉积带。12个礁坪原生滨珊瑚和2个礁岩滨珊瑚的14C和TIMSU Th测年结果表明永暑礁礁坪面形成于近代,它们没有提供中全新世高海平面的证据,约950aBP的中世纪暖期南沙群岛可能有过非常强的风暴潮。此外,1000年以内的珊瑚常规14C未校正年代与TIMSU Th年代存在显著差异,在环境解释中需要特别小心。From systematic field investigations, comes the following conclusion that the southwest reef bracelet of Yongshu Reef, Nansha Islands is a small closed atoll, rather than an opened one as previously postulated. Thus, the closed lagoon within this atoll may provide in situ biological sediment profiles for highresolution Holocene environment reconstruction. Six biologicalgeological and sedimentary zones are recognized. They are (1) reeffront living coral cluster zone, (2) outer reefflat coralgrowing zone, (3) reefridge coralbranchcemented zone, (4) inner reefflat branchcoralgrowing and sanddeposition zone, (5) lagoon slope branchcoralgrowing and thinsanddeposition zone, and (6) lagoon basinfloor siltdeposition zone. Radiocarbon and TIMS Useries ages of twelve in situ Porites lutea samples from the reef flat and two secondary Porites lutea reef rock samples indicate that the surface reef flat formed in the modern time. Unlike the northern coast fringing reefs, these samples cannot provide any midHolocene high sea level evidence. However, they recorded very strong storm(s) that occurred in the Medieval Warm Period, which produced many secondary large reef rocks deposited on the surface reef flat. The comparison of radiocarbon and TIMS Useries ages suggests that the radiocarbon ages of the corals less than 1 000 years old might have suffered from large uncertainties due to carbonreservoir effects and laboratory detection limitation, and thus great caution must be taken in the environmental interpretation of such corals. 

关 键 词：生物地貌 沉积环境 沉积带 海平面 风暴潮 永暑礁 TIMS U-Th年代 

分 类 号：P736.21[天文地球—海洋地质]