Crustal stretching style variations in the northern margin of the South China Sea

• Published in: Tectonophysics
• Main Authors: Bai, Yongliang, Dong, Dongdong, Brune, Sascha, Wu, Shiguo, Wang, Zhenjie
• Format: Report
• Language: English
• Published: ELSEVIER SCIENCE BV 2019
• Subjects: Crustal stretching style; Lower crustal flow; The northern margin of the South China Sea; Gravity inversion; Sediment load; Divergent mantle flow; Geochemistry & Geophysics; RIFTED CONTINENTAL MARGINS; RIVER MOUTH BASIN; EXTENSION DISCREPANCY; BAIYUN SAG; TECTONIC SUBSIDENCE; IBERIA-NEWFOUNDLAND; THERMAL-EXPANSION; XISHA TROUGH; EVOLUTION; DEPTH; Newfoundland
• Online Access: http://ir.qdio.ac.cn/handle/337002/155396; https://doi.org/10.1016/j.tecto.2018.12.012

Linking deep seismic profiles with regional-scale gravity inversion is a powerful tool to deduce the architecture of rifted margins and their structural evolution. Here we map upper and lower crustal thicknesses of the northern South China Sea (SCS) margin in order to investigate the occurrence of depth-dependent crustal extension from the proximal to the distal margin. By comparing upper and lower crustal stretching factors, we find that the northern margin of the SCS is segmented in three parts: (1) sedimentary basins where upper crust is stretched more than lower crust, (2) distal margin where lower crust is stretched more than upper crust, (3) mostly proximal margin regions where the two layers have similar stretching factors. Our results suggest that sedimentary basins and distal margin prominently feature depth-dependent extension, however accommodated by different processes. While differential thinning within sedimentary basins appears to be governed by lateral pressure variations inducing lower crustal flow, we suggest the distal margin to be affected by a combination of mantle flow-induced lower crustal shearing and sequential fault activity during crustal hyper-extension.