南沙道明群礁珊瑚礁地貌

珊瑚礁支持了对全球气候变化响应最敏感的生态系统之一，其部分特征地貌是海面变化记录的重要载体。目前，无论是对珊瑚礁现代地貌还是埋藏古地貌的研究多以定性为主，定量研究相对匮乏。基于2017年8~9月采集的浅层地震剖面数据，结合遥感影像研究显示，道明群礁目前是发育有1个岛、4个沙洲、7个干出礁和若干座暗礁的典型珊瑚群礁，其形状率为0.11，紧凑度为0.52，延伸率为4.20，礁坪发育指数为0.30，正处于群礁发育早期阶段，为半开放型—准封闭型群礁，远未台礁化，礁体结构遵循Darwin建立的“上截锥型”理论。道明群礁末次冰期以来的古地貌特征揭示了其地貌演化具有阶段性，经历了三个主要的生长期和两次停滞期，表明冰后期海面上升过程中，在相对水深80~90 m和50~60 m处发生停滞；道明群礁现代珊瑚礁开始发育于全新世早期。道明群礁向海坡、礁坪和潟湖盆相关钻孔的采集，将有助于建立可靠的年代标尺与海面变化过程曲线，进一步揭示冰后期南沙北部珊瑚礁地貌发育及其对海面变化的响应。

Coral Reef Geomorphology of Daoming Reefs in Nansha Islands

Coral reefs support one of the ecosystems responding to global climate change most rapidly, and part characteristic geomorphology of coral reefs is significant proxy to determine the sea level change. Currently, most of the published results are mainly based on qualitative researches, no matter the research on the modern geomorphology or the buried palaeogeomorphology of coral reefs, quantitative research is relatively scarce. Based on the analyses of shallow seismic profile data collected at Daoming Reefs (DR) in the northern area of the Nansha Islands from August to September in 2017 combined with high resolution Google Earth images, DR is a typical atoll with an island, four cays, seven drying reefs and several submerged reefs now. It could be seen that the form ratic of DR is 0.11, the compactness is approximately 0.52 with the ductility of 4.20, while the development index of reef flat is 0.30. It is obviously that DR is still a semi-open to quasi-enclosed atoll, still in the early development stage of reefs. The zoning of the underwater geomorphic units of DR indicates that its reef structure follows the Darwin’s atoll theory of ‘Upper Truncated Cone’. Furthermore, taking the erosion interfaces and various typical seismic facies buried under the reef flat and lagoon of DR into account, the features of its modern geomorphology and buried palaeogeomorphology of DR could be revealed. It also indicates that there are several stages of its geomorphologic evolution, including three main developing phases and two stagnated phases, While sea level rose in the postglacial period, it has two relatively stable phases at the water depth of 80-90 m and 50 - 60 m. The modern coral reef in DR began to grow in the early Holocene and developed continuously till now. To collect  the core samples at its out slope, reef flat and lagoon in DR, it would be helpful to set up the reliable chronology scale and the local curve of sea level rising, which would be important to reveal the geomorphologic evolution of the coral reefs in northern area of the Nansha Islands and its responses to sea level changes since the postglacial period further.