Continentward-dipping detachment fault system and asymmetric rift structure of the Baiyun Sag, northern South China Sea
Continentward-dipping detachment fault system and asymmetric rift structure of the Baiyun Sag, northern South China Sea
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DOI：
10.1016/j.tecto.2018.02.002
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发表时间：
2018-02
期刊：
影响因子：
2.9
通讯作者：
Zhichao Zhou;L. Mei;Jun Liu;Jinyun Zheng;Liang Chen;Shihao Hao
中科院分区：
文献类型：
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作者：
Zhichao Zhou;L. Mei;Jun Liu;Jinyun Zheng;Liang Chen;Shihao Hao
利用深地震反射剖面研究了南海中北部边缘远缘的裂谷结构和深部地壳结构。然而，由于地震资料有限，远缘超伸展裂谷盆地（白云凹陷和荔湾凹陷）的伸展断裂系统和裂谷构造一直是争论的一个基本问题。根据新的三维地震勘探资料和二维地震反射剖面，白云凹陷发现了一系列因伸展断裂作用而向海洋倾斜的断块。伸展断层一直倾向于大陆。在倾斜断块和伸展断层之下，低角度、高振幅和连续的反射被解释为控制伸展过程的主拆离面。裂陷过程中，倾向大陆的正断层自南向北依次演化，形成白云凹陷不对称的裂谷构造。白云凹陷被一系列构造高点与大洋分隔开来，这些构造高点是在33 Ma左右的大陆裂解和26-24 Ma的洋脊向南跳跃的岩浆活动的影响下抬升的。因此，我们认为岩浆活动在南海大陆伸展和最终裂解过程中起了重要作用。
The rift architecture and deep crustal structure of the distal margin at the mid-northern margin of the South China Sea have been previously investigated by using deep seismic reflection profiles. However, one fundamental recurring problem in the debate is the extensional fault system and rift structure of the hyperextended rift basins (Baiyun Sag and Liwan Sag) within the distal margin because of the limited amount of seismic data. Based on new 3D seismic survey data and 2D seismic reflection profiles, we observe an array of fault blocks in the Baiyun Sag, which were tilted towards the ocean by extensional faulting. The extensional faults consistently dip towards the continent. Beneath the tilted fault blocks and extensional faults, a low-angle, high-amplitude and continuous reflection has been interpreted as the master detachment surface that controls the extension process. During rifting, the continentward-dipping normal faults evolved in a sequence from south to north, generating the asymmetric rift structure of the Baiyun Sag. The Baiyun Sag is separated from the oceanic domain by a series of structural highs that were uplifted by magmatic activity in response to the continental breakup at ~33 Ma and a ridge jump to the south at 26–24 Ma. Therefore, we propose that magmatism played a significant role in the continental extension and final breakup in the South China Sea.