| 南沙群岛道明群礁库归沙洲脊槽地貌定量研究 |
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| 引用本文： | 梁 鹏,张永战.南沙群岛道明群礁库归沙洲脊槽地貌定量研究[J].高校地质学报,2022,28(5):768-775. |
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| 作者姓名： | 梁 鹏 张永战 |
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| 作者单位： | 1. 海岸与海岛开发教育部重点实验室，南京大学 地理与海洋科学学院，南京 210023；
2. 中国南海研究协同创新中心，南京 210093 |
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| 摘 要： | 脊槽地貌（Spur and Groove）是现代珊瑚礁礁坪和礁前的典型地貌，其发育特征是揭示珊瑚礁形成与演化过程的重要基础，目前有关环礁各地貌带脊槽地貌形态及成因的研究仍较为薄弱。南海南沙群岛岛礁脊槽地貌发育，是进行相关研究的理想区域。本文以南沙群岛北部道明群礁东北库归沙洲的典型脊槽地貌为研究对象，基于多波束测深数据，借助小波分析和过零点分析等方法，对环礁脊槽地貌形态参数进行定量研究。结果表明：库归沙洲各地貌带脊槽发育平均起始水深为15~16 m，主要为深水脊槽，最大起始水深相差较大（达8 m），而终止水深相似（平均为16 m左右）。脊槽高差在礁前斜坡和内礁坪为2.15 m左右，在潟湖坡为1.24 m；平均槽宽在礁前斜坡为47.30 m，在潟湖坡达54.92 m。因此，在礁前斜坡脊槽发育相对密集且高差大，潟湖坡脊槽发育相对稀疏且高差小。从礁前斜坡至潟湖坡，脊槽边坡坡度逐渐增大，由“V”型脊槽向“U”型脊槽过渡，槽谷由左倾逐渐转化为右倾。同时，在内礁坪和潟湖坡多发育次一级脊槽，“V”型和“U”型共存。与全球代表性珊瑚礁脊槽形态的对比分析表明：南海地区各环礁多发育深水脊槽，其槽宽和延伸长度的关系部分符合波浪侵蚀作用主控的“V”型脊槽的拟合直线，部分符合生物建造作用主控的“U”型脊槽的拟合直线，表明其可能受上述两个作用共同控制，不同地貌带两者相对强弱不同。同时，频繁的热带风暴的破坏作用可能也是一个要因。
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| 关 键 词： | 环礁 脊槽地貌 形态参数 小波分析 |
Quantitative Study on the Geomorphology of Spur and Groove atKugui Sandbank of Daoming Reefs in Nansha Islands |
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| LIANG Peng,ZHANG Yongzhan.Quantitative Study on the Geomorphology of Spur and Groove atKugui Sandbank of Daoming Reefs in Nansha Islands[J].Geological Journal of China Universities,2022,28(5):768-775. |
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| Authors: | LIANG Peng ZHANG Yongzhan |
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| Institution: | 1. Key Laboratory of Coast and Island Development, MOE: School of Geography and Ocean Science, Nanjing University, Nanjing 210023, China;
2. Collaborative Innovation Center of South China Sea Studies, Nanjing 210093, China; |
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| Abstract: | Spur and groove (SAG) is a typical geomorphologic feature of modern coral reef flat and reef front, and its development characteristics are an important basis for the understanding of the formation and evolution of coral reefs. However, the morphological features and formation mechanisms of SAG distributed in the different geomorphologic zones of atoll remain unclear up to present. There are series SAG widely distributed in the atolls in Nansha Islands in the South China Sea, which makes the Nansha Islands become an idea research area. In this paper, multi-beam bathymetric data covered the typical SAG well developed area are processed for the Kugui Sandbank, which is located in the northeastern Daoming Reefs. Wavelet analysis and zero crossing analysis are applied. It could be seen that the average initial water depth of SAG development is 15-16 m in all geomorphologic zones, so they are mainly deep-water SAG. The differences between the maximum initial water depth of SAG development in different geomorphologic zones are relatively large, with a difference of 8 m, but their termination water depths are similar, around 16 m as the average. The height of SAG in the front slope of the reef and inner reef flat are about 2.15 m, but only 1.24 m in lagoon slope, while the average wide of SAG in the front slope is 47.30 m, but up to 54.92 m in lagoon slope. Obviously, there are relatively high and dense SAG in the front slope, but low and sparse SAG in lagoon slope. From the front slope to the lagoon slope, the slope gradient of SAG increases gradually, shape of SAG in cross section changes from“V”shaped to“U” shaped, and from left leaning to right leaning. Furthermore, there are secondary SAG developed in inner reef flat and lagoon slope with“V”and“U”shaped. Compared with the other SAG formed in world representative coral reef well developed regions, it is evident that there is mainly deep-water SAG formed in atolls in the South China Sea. The correlation between their space and extension length either belong to“V”shaped or“U”shaped. The former is wave erosion processes dominated, the later is biological construction processes dominated. It probably means that SAGs in the South China Sea are controlled by above two processes together, and their relative strength are different in the different gromorphologic zones. Meanwhile, the destruction caused by the frequent tropical storms might be another key factor. |
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| Keywords: | Atoll Spur and Groove (SAG) morphological parameters wavelet analysis |
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