黄远静,胡心迪,张永战. 南沙郑和环礁小南薰礁的点礁地貌特征及其控制因素[J]. 海洋地质与第四纪地质,2022,42(3): 25-35. doi: 10.16562/j.cnki.0256-1492.2021082201
引用本文: 黄远静,胡心迪,张永战. 南沙郑和环礁小南薰礁的点礁地貌特征及其控制因素[J]. 海洋地质与第四纪地质,2022,42(3): 25-35. doi: 10.16562/j.cnki.0256-1492.2021082201
HUANG Yuanjing,HU Xindi,ZHANG Yongzhan. Distribution and morphological features of the patch reefs at Xiaonanxun Reef, Zhenghe Atoll of the Nansha Islands, South China Sea[J]. Marine Geology & Quaternary Geology,2022,42(3):25-35. doi: 10.16562/j.cnki.0256-1492.2021082201
Citation: HUANG Yuanjing,HU Xindi,ZHANG Yongzhan. Distribution and morphological features of the patch reefs at Xiaonanxun Reef, Zhenghe Atoll of the Nansha Islands, South China Sea[J]. Marine Geology & Quaternary Geology,2022,42(3):25-35. doi: 10.16562/j.cnki.0256-1492.2021082201

南沙郑和环礁小南薰礁的点礁地貌特征及其控制因素

Distribution and morphological features of the patch reefs at Xiaonanxun Reef, Zhenghe Atoll of the Nansha Islands, South China Sea

  • 摘要: 点礁是在空间上呈点状分布的礁体,是一种重要的珊瑚暗礁地貌类型,南海南沙群岛北部海区的一系列环礁发育有众多的珊瑚点礁。目前,对点礁地貌的形态特征、发育过程和机制的研究相对匮乏,南海地区的珊瑚点礁地貌定量研究尚为空白。以南沙群岛北部郑和环礁西南端的小南薰礁发育的点礁为研究对象,利用多波束水深实测数据结合Google Earth WorldView-2遥感影像,对所识别的123个点礁的顶底水深、高度、顶底直径等形态参数进行量测与统计分析,结果表明,其底部最大水深为35.05 m,顶部最小水深为7.89 m,平均高度2.62 m。其中,88个点礁(占71.5%)分布于水深25~35 m(深水点礁),27个(占17.9%)分布于水深10~18 m(浅水点礁)。点礁顶部和底部直径的平均值分别为8.49 和19.13 m,形状因子和顶底关系因子的平均值分别为0.15和0.42,其剖面形态呈峰丘型(21.1%)和礁坪型(占78.9%),且多呈孤立型分布,亦见少数以群落型分布。浅水点礁以礁坪型为主,其顶部和底部直径较大,而形状因子较小,反映了波浪动力的控制作用;峰丘型仅见于深水点礁,其形状因子较大(>0.23),顶底关系因子较小(<0.25),高度和直径呈正相关,反映了珊瑚生长作用对点礁地貌的影响。点礁底部直径集中呈NEE-N向延伸,显示了海域盛行风向与海水运动方向的控制作用。

     

    Abstract: Coral reef is an efficient indicator for paleoenvironment reconstruction, as it may provide abundant information on paleoclimate changes, sea-level fluctuations and marine environmental variations. Patch reef is a kind of submerged reefs, widely distributed in isolation on reef flat in patch shape in the atolls of the northern Nansha Islands area of the South China Sea. However, the morphological features and formation mechanisms of these patch reefs remain unclear up to present. In this paper, Google Earth WorldView-2 images and multi-beam bathymetric data are processed and carefully studied for the Xiaonanxun Reef, which is located in the southwestern Zhenghe Atoll. Patch reefs are widely distributed there in secondary lagoons, tidal channels, lagoonal slopes and basin floors. Based on the data mentioned above, 123 patch reefs are recognized and measured. The maximum depth of the rim and the minimum depth of the top of the patch reefs are 35.05 m and 7.89 m, and the average height, bottom diameter and top diameter of the patch reefs are 2.62 m, 19.13 m and 8.49 m on average respectively. Most of the patch reefs is distributed in isolation in shapes of “pancake” and “knoll”, and only 3 groups are found combined as colony developed in the area in the water depth of 29 ~ 35 m. The patch reefs developed in the water depth less than 18 m are predominated by the “pancake” type, with the average height and the bottom and top diameters in 1.85 m, 21.98 m and 11.79 m, respectively. The shape index is rather small (less than 0.23), but the relational factor between top and bottom is rather large (87% between 0.30 and 0.75). Wave dynamics are believed the dominant factor to the morphological features. In contrast, “knoll” type of patch reefs is mainly developed in the area under water depth deeper than 25 m, and the average height and bottom and top diameters are 2.74 m, 17.44 m and 6.89 m respectively. The bottom diameter and height of patch reefs are positively correlated and the correlation coefficient R is up to 0.827, which indicates the biological processes of coral growth is the dominant factor to the morphological features. Furthermore, the long axis direction is mainly in NEE to N direction for 82% of the bottoms of the patch reefs, being consistent with the prevailing wind wave direction and perpendicular to the reef crest, which indicate the impacts of the wave dynamic processes as well.

     

/

返回文章
返回