张永战1,2,3,,
1. 南京大学地理与海洋科学学院, 江苏 南京 210023
2. 南京大学海岸与海岛开发教育部重点实验室, 江苏 南京 210023
3. 中国南海研究协同创新中心, 江苏 南京 210023
基金项目: 中国科学院学部咨询项目"南海海域、岛礁开发与海疆权益"、中国南海研究协同创新中心及江苏省自然科学基金面上项目（批准号：BK20171341）共同资助
详细信息
作者简介: 王黎, 男, 24岁, 硕士研究生, 从事海岸海洋地貌与沉积学研究, E-mail:twilight528400@hotmail.com
通讯作者: 张永战, E-mail:zhangyzh@nju.edu.cn
中图分类号: P736.14;P737.12收稿日期:2017-11-28
修回日期:2017-12-31
刊出日期:2018-03-30
Distribution and morphological characteristics of Spur and Groove on submerged reefs of Jiuzhang Atoll, South China Sea
Wang Li1,2,3,,Zhang Yongzhan1,2,3,,
1. School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210023, Jiangsu
2. The Key Laboratory of Coast & Island Development of Ministry of Education, Nanjing University, Nanjing 210023, Jiangsu
3. Collaborative Innovation Center of South China Sea Studies, Nanjing University, Nanjing 210023, Jiangsu
More Information
Corresponding author: Zhang Yongzhan,E-mail:zhangyzh@nju.edu.cn
MSC: P736.14;P737.12--> Received Date: 28 November 2017
Revised Date: 31 December 2017
Publish Date: 30 March 2018
摘要
摘要:珊瑚礁脊槽地貌（Spur and Groove，简称SaG），多发育于礁前斜坡，是珊瑚礁生态系统中最具生物多样性和生产力的区域之一。目前，对珊瑚礁脊槽地貌形态特征、形成机制的研究相对匮乏，中国南海南沙珊瑚岛礁区的相关研究尚为空白。基于Google Earth的高清影像与九章环礁典型脊槽地貌发育区的多波束水深数据，分析研究显示：九章环礁潟湖与外侧海水交换区的18个水下暗礁普遍发育脊槽地貌，脊槽的延伸方向与礁缘垂直。实测典型脊槽分布区的平均脊长85.4 m，平均脊高4.2 m，脊水深不超过15.0 m；平均脊宽7.5 m，稍小于槽宽；槽谷横剖面形态多呈斜坡U型。水下暗礁脊槽地貌，与波浪动力条件主控形成的典型侵蚀型脊槽地貌形态差异明显；脊槽分布特点、延伸方向和形态特征，指示了潮流动力作用的影响；其脊长、脊高、脊宽三者互呈正相关，显示珊瑚生长作用对脊槽形态的影响；区域的海平面变化特点，指示了全新世早期海侵条件下发育珊瑚礁脊槽地貌及其残留的可能。脊槽地貌的形成机制及其所揭示的古环境信息，还需要钻孔、沉积动力学和珊瑚礁生态学等方面的进一步综合研究。
关键词: 脊槽地貌/
水下暗礁/
地貌模式/
动力地貌/
残留地貌
Abstract:Spur and Groove(SaG)is a common and significant feature developed primarily crossing fore-reef slope worldwide. It is one of the most productive zones with highest biodiversity in the coral reef ecosystem. However, the morphological characteristics and formation mechanism of SaG are still poorly understood, particularly in Nansha Islands, South China Sea. Jiuzhang Atoll consisting of a series of platform reefs and submerged reefs is one of the echelon arranged bank reefs located in the northern part of Nansha Islands. It develops from more than 2000 m water depth sea bottom and extends along NE-SW direction with 56 km long and 9~14 km wide. The northern part of Nansha Islands is controlled by the monsoon climate with alternated prevailing wind, that is, southwestward wind in summer and northeastward wind in winter. Wind waves are the main wave dynamics distinctly controlled by monsoon climate.
High resolution Google Earth images of 18 submerged reefs of Jiuzhang Atoll and multi-beam bathymetric data collected at a typical SaG area have been used to measure the morphology and analyze the distribution of SaGs. SaG spreads on submerged reefs which is the transitional zone between the lagoon of Jiuzhang Atoll and the open sea, and is perpendicular to the reef edge. The average length and height of spurs in typical SaGs covered area are 85.4 m and 4.2 m, with 7.5 m wide on average, which is narrower than groove. Meanwhile, grooves are U-shaped with flat bottom, covered with abundant broken coral reef fragments, while spurs are covered by some corals. From the lagoon to the fore reef, the water depth of grooves increases gradually, while the change along spurs is not obviously.
The SaGs distributed on submerged reefs of Jiuzhang Atoll are clearly different from the typical wave eroded SaGs, in terms of the water depth of the distribution area, the extension direction of spurs and grooves, and the relationship between the morphological parameters of SaGs. On the other hand, it shows the impact of the tidal dynamic processes. Strong positive correlation could be found among the length, height and width of spurs, which shows the effect of coral growth processes. However, spurs which distribute in 10 m water depth area in average with inclined slope, are distinct from the typical SaGs dominated by coral growth processes in Caribbean Sea. Similar to the deep SaGs disconnected with reef flat in the southern Great Barrier Reef, the SaGs on submerged reefs of Jiuzhang Atoll might be relict features formed at an early stage in the Holocene transgression, while the sea level was relatively stable. Wave eroded terrace in 20~25 m water depth has been observed in northeastern Jiuzhang Atoll, the terraces in the same water depth have been reported in Yongshu Reef and along the coast of the northern South China Sea formed at about 8 ka B.P. And the boundary between Holocene and Pleistocene was buried in 17.3 m deep in Yongshu Reef revealed in a sedimentary core, which located in the reef flat with water depth less than 2 m. Which are all evidences to show that the studied SaGs might be the residual geomorphology. To fully understand SaG formation mechanisms and concerned paleogeographical conditions, further comprehensive research including coral reef ecology, drilling, sedimentary dynamics and paleo-oceanography is necessary, to even understand the development and evolution of bank reefs.
Key words:Spur and Groove/
submerged reef/
geomorphic pattern/
dynamic geomorphology/
residual geomorphology
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