The premature decay of rifting processes in the northern South China Sea (38–33.9 Ma): insight from 3D seismic and its interpretation of the Lufeng Sag of the Pearl River Mouth Basin

Abstract

A marked transition in depositional signatures within the second rift phase (RP2, 38–33.9 Ma) in the Lufeng Sag, a proximal domain on the northern continental margin of the South China Sea (SCS) has been previously documented. This study integrates seismic data, fault paleo-throw, strain and depth-to-detachment to demonstrate the structural variability in time and space during the early to late stage of RP2 in the Lufeng Sag and investigates the rifting transition and its relationship with rifting processes on the northern SCS margin. The results indicate that extensional deformation transferred from south to north within the Lufeng Sag during RP2 and the rifting in the South Sub-sag was weaker than in the North Sub-sag during both the early and late stages. This structural variability may be related to the basement uplift in the southeast caused by the remote effect of plate movement and magmatic underplating under the Dongsha Uplift. A change of basin geometry from wedge-shaped to nearly tabular, strongly reduced paleo-throws and strains, and sharply increased depth-to-detachment from the early to late stage indicates the premature decay of rifting before the breakup of the SCS. This transition may be influenced by the opening of the Northeast Sub-basin of the SCS at ca 37 Ma, where extensional strain sharply concentrated, and led to the waned rifting of the Lufeng Sag. The study thus provides new insights into rifting processes along the northern SCS margin that can be applied to similar basins elsewhere.

KEY POINTS

1. Basin geometry, fault paleo-throw, strain and depth-to-detachment analysis demonstrate a weakened rifting in the Lufeng Sag (38–33.9 Ma).

2. Structural variability between the South and North sub-sags may be caused by the remote effect of plate movement and magmatic underplating during the Dongsha Uplift.

3. Structural transitions in the Lufeng Sag indicate a premature decay of rifting before the breakup of the SCS, which was caused by thermal subsidence and regional plate subduction.

Keywords:

• Tectonic evolution
• second rift phase
• premature decay of rifting
• Pearl River Mouth Basin
• continental margin
• South China Sea

Acknowledgements

We would like to express our gratitude to the China National Offshore Oil Corporation Limited-Shenzhen, for their kind permission to publish the results. We appreciate Yuan An, Zicheng Niu and Rui Liu, who offered lots of helpful efforts on seismic data interpretations. Special thanks to the Associated Editor Brian G. Jones, for his professionally editorial work, which significantly improved the readability and scientific impact of the final submitted manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data used to support the findings of this study are available from the corresponding authors upon request.

Additional information

Funding

This research was financially supported by National Natural Science Foundation of China [No. 41902124], a China Postdoctoral Science Foundation Funded Project [No. 2019M653477], a Scientific Research Starting Project from Southwest Petroleum University [No. 2018QHZ010], and the Foundation of State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing [No. PRP/Open-1903].