南沙珊瑚礁潟湖坡微地貌对沉积物粒度特征的影响  

Influence of Micro-Geomorphology on Sediment Grain Size Characteristics in the Lagoon Slopes of the Nansha Coral Reefs

作　　者：王明壮 张喜洋 谭飞 王冠[1,3] 施祺 杨红强[1,3,4] Wang Mingzhuang;Zhang Xiyang;Tan Fei;Wang Guan;Shi Qi;Yang Hongqiang(Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou 510301,China;University of Chinese Academy of Sciences,Beijing 100049,China;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,China;Nansha Marine Ecological and Environmental Research Station,Chinese Academy of Sciences,Sansha 573199,China)

机构地区：[1]中国科学院边缘海与大洋地质重点实验室,中国科学院南海海洋研究所,广州510301 [2]中国科学院大学,北京100049 [3]南方海洋科学与工程广东省实验室(广州),广州511458 [4]中国科学院南沙海洋生态环境实验站,海南三沙573199

出　　处：《热带地理》2024年第10期1826-1837,共12页Tropical Geography

基　　金：国家自然科学基金项目(42306076);国家重点研发计划(2021YFC3100603、2022YFC3102402)。

摘　　要：潟湖坡是礁坪沉积物向潟湖盆搬运的关键地貌带,对了解礁后沉积过程和环礁发育演化至关重要。然而,潟湖坡微地貌特征及其对沉积物粒度的影响还未明确。文章对南沙群岛主权礁与三角礁潟湖坡开展研究,采集表层沉积物并结合水深数据和水下微地貌开展粒度分析,结果表明:1)主权礁与三角礁潟湖表层沉积物以砂级颗粒为主,粉砂与细砾质量分数较少,其中主权礁沉积物中砂级颗粒质量分数为94.55%,细砾为4.18%,粉砂为0.61%;三角礁S1-S1′方位含砂93.96%,细砾4.04%,粉砂1.65%;S2-S2′方位含砂91.73%,细砾为6.84%,粉砂为1.17%。潟湖砂体的中值粒径与水深呈显著负相关,粒度分布曲线在深水区呈单峰式,在浅水区呈双峰式,整体偏态为负偏态。2)物源和水动力特征是影响南沙珊瑚礁潟湖坡砂体粒度分布的主要因素,主权礁潟湖坡点礁密布,周围颗粒粒径显著增大,削弱了水深与粒度的负相关性,表明潟湖点礁亦是重要物源;三角礁潟湖坡发育海草床,减弱了颗粒的动力再分选作用,形成粗粒和细粒混积的双峰形态。3)潟湖坡微地貌对颗粒粒度分布起关键作用。主权礁双峰式分布曲线的形成主要受潟湖点礁的影响,而海草根系的固沙作用减弱了颗粒的动力分选作用,形成三角礁双峰式分布曲线。The lagoon slopes of coral atolls,which connect reef flats to lagoon basins,are key geomorphic zones where sediments are physically sorted and transported.These areas are essential for understanding post-reef sedimentary processes and the broader evolutionary dynamics of atolls.However,the influence of the microtopographic features of lagoon slopes on sediment grain size distribution remains unclear.Sediment grain size is a sensitive indicator of environmental and climatic changes and provides valuable insights into sediment transport patterns and depositional environment reconstructions.The spatial distribution of grain size is influenced by the proximity to sediment sources,material availability,and surrounding geomorphological conditions.This study focused on the lagoon slopes of the Shuquan and Jiaojian Reefs in the Nansha Islands,where surface sediment samples were collected and analyzed for grain size,along with depth data and underwater microtopography.The results indicated the following:(1)Surface sediments in the lagoon slopes of the Shuquan and Jiaojian Reefs are predominantly composed of sand-sized particles,with minimal silt and fine gravel content.Specifically,Shuquan Reef sediments comprised 94.55%sand-sized particles,4.18%fine gravel,and 0.61%silt;the S1-S1'transect contained 93.96%sand,4.04%fine gravel,and 1.65%silt;and the S2-S2'transect consisted of 91.73%sand,6.84%fine gravel,and 1.17%silt.(2)The grain size characteristics of lagoon sands were primarily governed by the proximity to sediment sources and hydrodynamic conditions.A significant negative correlation was observed between median grain size and water depth,with grain size decreasing as depth increased.Most lagoon sands originated from reef flats or lagoon slopes,reflecting the diminishing sorting capacity of oceanic wave energy as it moves toward the lagoon center.The grain size distribution curves of lagoon sands are generally unimodal or bimodal,with a trend toward negative skewness.In deeper waters,the curves became sharper,indicatin

关 键 词：粒度 微地貌 潟湖 环礁 南沙群岛 

分 类 号：P737[天文地球—海洋地质]