热带海洋学报 ›› 2021, Vol. 40 ›› Issue (5): 72-84.doi: 10.11978/2020111

• 海洋地质学 • 上一篇    下一篇

中建南盆地北部海底麻坑地貌特征及成因机制

汪灵1,2,3(), 王彬4, 李健1,2(), 喻凯琦1,2,3, 赵芳1,2   

  1. 1.中国科学院边缘海与大洋地质重点实验室, 南海海洋研究所, 广东 广州 510301
    2.中国科学院南海生态环境工程创新研究院, 广东 广州 511458
    3.中国科学院大学, 北京 100049
    4.中国石油天然气股份有限公司杭州地质研究院, 浙江 杭州 310023
  • 收稿日期:2020-09-22 修回日期:2020-12-09 出版日期:2021-09-10 发布日期:2021-01-13
  • 通讯作者: 李健
  • 作者简介:汪灵(1996—), 女, 江西省井冈山市人, 硕士研究生, 主要从事海底地貌与海洋地球物理方面的研究。email: wangling@scsio.ac.cn
  • 基金资助:
    广东省实验室(广州)人才团队引进重大专项(GML2019ZD0104);国家科技基础资源调查专项(2017FY201406);广东省“珠江人才计划”高层次人才认定项目(2017GC010510)

Morphology characteristics and formation mechanisms of submarine pockmarks in the northern Zhongjiannan Basin, South China Sea

WANG Ling1,2,3(), WANG Bin4, LI Jian1,2(), YU Kaiqi1,2,3, ZHAO Fang1,2   

  1. 1. Key Laboratory of Ocean and Marginal Sea Geology, Chinese Academy of Sciences, South China Sea Institute of Oceanology, Guangzhou 510301, China
    2. Innovation Academy of South China Sea Ecology and Environmental Engineering, Guangzhou 511458, China
    3. University of Chinese Academy of Sciences, Beijing 100049, China
    4. PetroChina Hangzhou Research Institute of Geology, Hangzhou 310023, China
  • Received:2020-09-22 Revised:2020-12-09 Online:2021-09-10 Published:2021-01-13
  • Contact: LI Jian
  • Supported by:
    Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(GML2019ZD0104);Special Foundation for National Science and Technology Basic Research Program of China(2017FY201406);Guangdong Pearl River Talents Program(2017GC010510)

摘要:

海底麻坑是与流体逸散相关的一种海底凹陷地貌, 在全球海域的陆架、陆坡和深海平原等均有广泛发育。文章利用高分辨率的多波束测深数据和三维地震资料, 在中建南盆地北部识别出330个规模不等的海底麻坑, 按照麻坑形态可将其分为: 圆形、椭圆形、长条形及新月形麻坑。研究区内海底麻坑直径可达1500~7900m, 最大深度可达175m, 其中圆形麻坑规模(直径、深度)小于椭圆形、长条形和新月形麻坑, 表明圆形麻坑处于麻坑发育早期阶段。三维地震资料显示不同类型海底麻坑的下伏地层中均发育有断层、气烟囱、裂隙等流体逸散通道, 为该区域海底麻坑形成提供了有利条件。在海底麻坑演化过程中, 底流对海底麻坑的地貌形态具有改造作用。当圆形麻坑下伏地层流体活动强烈时, 流体可沿着运移通道直接向麻坑内壁渗漏, 使得其内壁塌陷, 逐渐演化成椭圆形麻坑。由于椭圆形麻坑处于底流活动影响的早期阶段, 其受底流改造作用较弱。在持续性底流活动的强烈改造作用下, 紧密排列的圆形或椭圆形麻坑逐渐拉伸演变成长条形麻坑。当底流作用于孤立的圆形麻坑时, 在底流的上游侧沉积速率增加, 麻坑在上游侧接受沉积被掩埋, 下游侧地层被侵蚀, 从而形成新月形麻坑。根据研究区海底麻坑成因机制分析, 文章首次提出了一种展示中建南盆地不同类型海底麻坑演化过程模型, 该模型有助于理解中建南盆地流体逸散过程和底流活动, 并且可为其他区域海底麻坑演化过程研究提供参考。

关键词: 海底麻坑, 地貌特征, 成因机制, 演化过程, 中建南盆地

Abstract:

Submarine pockmarks are defined as submarine depressions associated with fluid escape, which are distributed widely in the continental shelf, slope and plain of global oceans. By using multibeam bathymetric maps and three-dimensional seismic profiles, we identified 330 pockmarks with different scales in the northern part of the Zhongjiannan Basin in the South China Sea. Depending on the plan views, these pockmarks are divided into four types: circular, elliptical, elongated, and crescent pockmarks. The pockmarks in the study area have diameters ranging from 1500 to 7900 m, with a maximum depth of 175 m. The scale of circular pockmarks is smaller than those of the other three types in this area, indicating that circular pockmarks are in the early stage of submarine pockmarks. The 3D seismic profiles show that fluid escape pathways, such as faults, gas chimneys and fractures, develop in their overlying strata, which provide a favorable condition for these pockmarks. Bottom currents have an effect on shaping the morphology of pockmarks in our study area. When the flowing fluids are powerful in the underlying strata, the flanks of circular pockmarks would collapse where the flowing fluids supply to the flanks along migration pathways directly. Because bottom currents affect elliptical pockmarks at their early stage, elliptical pockmarks would not show any obvious modification. Additionally, the closely arrayed circular or elliptical pockmarks would gradually evolve into elongated pockmarks due to the strong effect of consistent bottom currents. The upstream sides of isolated circular pockmarks are buried due to the increment of sedimentation rate and the downstream sides of these pockmarks are eroded, which leads to the formation of crescent pockmarks. By analyzing the formation mechanisms of pockmarks, we propose a model to exhibit the evolutions of different types of pockmarks in the northern part of the Zhongjiannan Basin. This model helps us better understand the process of fluid escape and bottom current flows and provides a reference for other areas of the formation of pockmarks.

Key words: submarine pockmark, morphology characteristics, formation mechanism, evolution process, Zhongjiannan Basin

中图分类号: 

  • P737.22