石油与天然气地质 ›› 2024, Vol. 45 ›› Issue (1): 15-30.doi: 10.11743/ogg20240102

• 油气地质 • 上一篇    下一篇

重力流与海底地貌动态相互作用下深水沉积体系发育演化

田纳新1(), 龚承林2, 吴高奎1, 齐昆2, 朱一杰2, 刘静静1   

  1. 1.中国石化 石油勘探开发研究院,北京 102206
    2.中国石油大学(北京) 地球科学学院,北京 102249
  • 收稿日期:2023-10-05 修回日期:2023-11-14 出版日期:2024-02-01 发布日期:2024-02-29
  • 第一作者简介:田纳新(1968—),男,博士、高级工程师,石油地质学。E-mail:tiannx.syky@sinopec.com
  • 基金项目:
    国家科技重大专项(2016ZX05033);中石化集团科研项目(P21043-3)

Development of submarine depositional systems under dynamic interplays between sediment gravity flows and seafloor topography: A case study of the Potiguar Basin on the equatorial Atlantic Ocean

Naxin TIAN1(), Chenglin GONG2, Gaokui WU1, Kun QI2, Yijie ZHU2, Jingjing LIU1   

  1. 1.Petroleum Exploration and Production Research Institute,SINOPEC,Beijing 102206,China
    2.College of Geosciences,China University of Petroleum (Beijing),Beijing 102249,China
  • Received:2023-10-05 Revised:2023-11-14 Online:2024-02-01 Published:2024-02-29

摘要:

海底地貌对重力流沉积具有重要控制作用并同时受到重力流沉积过程影响。针对重力流与海底地貌动态相互作用下深水沉积体系发育演化研究不足的问题,以大西洋赤道段菩提瓜尔盆地的局部沉积记录为解剖对象,基于三维地震资料,采用RGB三色融合技术,阐明了深水沉积体系发育演化特征,揭示了重力流与海底地貌的动态相互作用。研究区初始地貌中的主要地貌低点和次要地貌低点控制了早期深水水道和朵叶体的发育:①随着主要地貌低点斜坡坡度向远物源一端明显变缓,重力流的速度和能量逐渐减小,向下侵蚀能力变弱、侧向拓宽能力增强,水道剖面形态沿流向依次呈现V型、深U型及碟型;②因为水道限制性逐渐减弱,末端非限制性区域发育朵叶体沉积,朵页体上覆于水道充填沉积且向近物源一端生长,最终溢出到研究区西北角的次要地貌低点。水道和朵叶体沉积致使主要地貌低点远物源一端的斜坡坡度进一步变缓,后期块体流被捕获时,其沿流向携带沉积物的能力更容易降低,导致块体搬运沉积复合体(MTCs)在主要地貌低点远物源一端广泛堆积。

关键词: 地貌低点, 动态相互作用, 海底地貌, 重力流, 深水沉积, 菩提瓜尔盆地, 大西洋赤道段

Abstract:

Seafloor topography plays a significant role in the modulation of gravity flow deposition and in the meantime, the associated depositional processes can modify the pre-existing topography. Given a lack of studies on the development of the submarine depositional systems as a consequence of the dynamic interplays between sediment gravity flows and seafloor topography, we analyze the local depositional records of the Potiguar Basin on the equatorial Atlantic Ocean. Using 3D seismic data along with spectral decomposition and spectral decomposition with red, green and blue (RGB) color blending techniques, we investigate the development of a submarine depositional system and then reveal the dynamic interactions between sediment gravity flows and seafloor topography. The results indicate that the main topographic low and the minor topographic low within initial topography of the study area played a major role in the deposition of early submarine channels and lobes. With the gentling of the slope along the main topographic low toward the distal provenance end, the velocities and competences of sediment gravity flows gradually decreased; correspondingly, their tendences of vertically downcutting and laterally broadening respectively weakened and strengthened, resulting in the cross-sectional geometries of submarine channels varying from V-shaped through deep U-shaped to dish-shaped downstream. Because submarine-channel confinement gradually decreased downstream, lobes occur at the unconfined terminal area, which grew headward, overlay on the early channel fills, and finally spilled out into the minor topographic low at the northwestern corner of the study area. The deposition of submarine channels and lobes significantly reduced the slope gradients in distal parts of the main topographic low. When subsequent mass flows were captured by the main topographic low, the capacity of mass flows to carry sediments was prone to get even weaker, thus resulting in more extensive accumulation of mass-transport complexes (MTCs) in distal parts of the main topographic low.

Key words: topographic low, dynamic interaction, seafloor topography, sediment gravity flow, submarine depositional system, Potiguar Basin, equatorial Atlantic Ocean

中图分类号: