Paleogene structural development of the northern Song Hong Basin and adjacent areas: Implications for the role of extrusion tectonics in basin formation in the Gulf of Tonkin

• Published in: Tectonophysics 2020-08, Vol.789, p.228522, Article 228522
• Main Authors: Hoang, Bui H., Fyhn, Michael B.W., Cuong, Tong D., Tuan, Nguyen Q., Schmidt, William J., Boldreel, Lars O., Anh, Nguyen T.K., Huyen, Nguyen T., Cuong, Trinh X.
• Format: Article
• Language: English
• Subjects: Basins; Beibuwan Basin; Displacement; Eocene; Extrusion; Lateral displacement; Marginal basins; Oligocene; Paleogene; Plate tectonics; Rifting; Rotation; Shear zone; Shearing; Slab-pull; Slip; Song Hong Basin; South China Sea; Stratigraphy; Strike-slip; Tectonics
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2020.228522

The Song Hong Basin situated at the distal part of the Ailaoshan-Red River Shear Zone (ASRRSZ) holds important information on the role of extrusion tectonics in the marginal basin development in the South China Sea. Based on an extensive dataset of 2 and 3-D seismic and stratigraphic information from 27 exploration wells, the Paleogene structural evolution of the northern Song Hong Basin and adjacent areas has been studied in detail. This study proposes a new Paleogene structural development model of the study area. Eocene-Oligocene rifting in the northern Song Hong Basin was driven by left-lateral shearing from the ASRRSZ associated with a combined motion of clockwise rotation and translation of the Indochina Block, which allowed extension along the “restraining bend” geometry of the basin's eastern margin. A structural high separates the Song Hong Basin from the Beibuwan Basin, inhibiting significant strike-slip displacement transfer from the ASRRSZ into rifting in the Beibuwan Basin. Strike-slip displacement from the ASRRSZ is maintained further south to the East Vietnam Boundary Fault segment. Thus, extension of the Beibuwan, Qiongdongnan and Phu Khanh Basins were the result of the interplay between extrusion and slab-pull tectonics. During the end of the Oligocene, reduced extrusion of Indochina caused minimal rotation of the block, and the remaining left-lateral displacement along the ASRRSZ was absorbed into inversion around the junction between the Song Hong and Beibuwan basins. •Paleogene transtension was driven by SE-ward extrusion and rotation of Indochina.•Only a small fraction of the extrusion was taken up by rifting in the Beibuwan Basin.•End-of-Oligocene inversion was driven by reduced extrusion of Indochina.