地学前缘 ›› 2022, Vol. 29 ›› Issue (4): 55-72.DOI: 10.13745/j.esf.sf.2022.1.2

• 深海沉积过程演化 • 上一篇    下一篇

南海北部琼东南盆地第四系陆架边缘轨迹迁移及深水沉积模式

马畅1(), 葛家旺1,2,*(), 赵晓明1,2, 廖晋3, 姚哲3, 朱继田3, 方小宇2, 向柱1   

  1. 1.西南石油大学 地球科学与技术学院, 四川 成都 610500
    2.南方海洋科学与工程广东省实验室(湛江), 广东 湛江 524000
    3.中海石油(中国)有限公司海南分公司, 海南 海口 570100
  • 收稿日期:2021-08-10 修回日期:2021-09-28 出版日期:2022-07-25 发布日期:2022-07-28
  • 通讯作者: 葛家旺
  • 作者简介:马 畅(1997—),男,硕士研究生,主要从事沉积学方面研究工作。E-mail: swpumc@163.com
  • 基金资助:
    国家自然科学基金项目(42072183);国家自然科学基金项目(41902124);南方海洋科学与工程广东省实验室(湛江)资助项目“南海水合物富集规律及固态流化开采机理研究(一期)(ZJW-2019-03)

Quaternary Qiongdongnan Basin in South China Sea: Shelf-edge trajectory migration and deep-water depositional models

MA Chang1(), GE Jiawang1,2,*(), ZHAO Xiaoming1,2, LIAO Jin3, YAO Zhe3, ZHU Jitian3, FANG Xiaoyu2, XIANG Zhu1   

  1. 1. School of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, China
    2. Guangdong Laboratory of Southern Marine Science and Engineering-Zhanjiang, Zhanjiang 524000, China
    3. Research Institute of Haikou Branch, CNOOC, Haikou 570100, China
  • Received:2021-08-10 Revised:2021-09-28 Online:2022-07-25 Published:2022-07-28
  • Contact: GE Jiawang

摘要:

陆架边缘迁移轨迹综合受控于构造、物源、海平面和气候等多种因素,其迁移演化与深水沉积体系发育关系密切。陆架边缘迁移规律及沉积物输送体制与深水砂体预测是当前国际地学领域的热点议题。本文通过基于琼东南盆地新采集的高精度地震资料,定量表征了第四系陆架边缘轨迹,识别了低角度缓慢上升型、中等角度上升型和高角度急剧上升型等3类陆架边缘轨迹类型。2.4 Ma以来,陆架边缘轨迹时空演化可分为3个阶段且具有侧向差异性:2.4~1.9 Ma以低角度缓慢上升型为主,1.9~0.8 Ma西北部以低角度缓慢上升型为主,东北部则以中等角度上升型为主,0.8 Ma至今西北部以中等角度上升型为主,东北部以高角度急剧上升型为主。琼东南盆地第四系陆架边缘迁移轨迹研究表明:当陆架边缘轨迹角0°<α<4°时,陆坡区峡谷规模较小且下切浅,深海平原区发育多期大型海底扇沉积,块体搬运沉积(MTDs)较少;当4°<α<35°时,陆坡区峡谷规模有所增加,深海平原区海底扇沉积与块体搬运沉积均有出现;当35°<α<90°时,陆坡区峡谷发育较少但下切深,深水平原区沉积以大型块体搬运沉积为主,海底扇几乎不发育。琼东南盆地更新世以来气温不断下降,以及东亚冬季风的显著增强,物源供给增强加之海平面的下降进而导致了西北部陆架边缘表现为进积特征;研究区东北部的断裂活动频繁以及物源供给弱,导致了研究区东北部陆坡推进距离远远小于研究区西北部且发育多期次块体搬运沉积物。以上认识对南海北部陆架边缘体系及深水扇预测具有一定的理论意义。

关键词: 琼东南盆地, 第四系, 陆架边缘轨迹, 定量化表征, 深水沉积体系

Abstract:

The shelf-edge trajectory is comprehensively controlled by tectonics, sediment supply, sea level and climate, and its migration and evolution are closely related to the deep-water depositional systems. The shelf-edge clinoform stacking pattern, sediment-budget partition in deep-water areas and reservoir evaluations are current geoscience hot topics. Based on the newly acquired high-precision, high-density 2D seismic data of the Qiongdongnan Basin (QDNB), this paper quantitatively characterized the Quaternary shelf-edge trajectory and identified three trajectory types in QDNB: flat to slightly rising, moderately rising and steeply rising types. Since 2.4 Ma the temporal evolution of the shelf-edge trajectory in QDNB can be divided into three stages with lateral differences: 2.4-1.9 Ma, mainly the slightly rising type; 1.9-0.8 Ma, the slightly rising type in the western part and moderately rising type in the eastern part; 0.8 Ma-present, the moderately rising type in the western part and steeply rising type in the eastern part. The vertical migration of the shelf-edge trajectory is jointly controlled by the rise and fall of sea level caused by climate change and associated with sediment supply. The differences in tectonic activity and provenance supply lead to lateral variations of the shelf-edge trajectory and progradation or aggradation stacking patterns. According to the above studies, when the shelf-edge trajectory angle, α, is between 0° and 4°, the continental slope canyons are small-scaled and shallow mostly, with developments of multistage large-scale submarine fan deposits in the deep-water area but less mass-transport deposits (MTDs). When 4° <α< 35° the continental slope canyons increase in scale, with occurrences of both submarine fan deposits and MTDs. When 35°<α<90° a few but steep continental slope canyons are developed, along with developments of mainly large-scale MTDs in the deep-water plains, almost without submarine fan deposits. Since the Quaternary the temperature in QDNB continues to drop while the East Asian winter monsoon increases significantly, causing the sediment supply to increase; while decreasing sea level results in progradation at the northwestern shelf edge. In comparison, frequent fault activities and relatively low sediment supply at the northeastern shelf edge result in a much shorter slope advance distance and developments of multistage MTDs. Results of this study have theoretical significance for the predictions of continental shelf-edge system and deep-water deposition in QDNB and other basins.

Key words: Qiongdongnan Basin, Quaternary, shelf-edge trajectory, quantitative characterization, deep-water depositional system

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