Stratigraphic architectures and associated unconformities of Pearl River Mouth basin during rifting and lithospheric breakup of the South China Sea

Abstract

The lithosphere breakup processes from initial rifting of the crust to the complete rupture of the lithosphere underwent several tectonic evolution stages and resulted in the formation of a distinct stratigraphic architecture and associated unconformities. In this study, a dense grid of seismic profiles tied to industrial borehole data are used to investigate the stratigraphic architecture and unconformity interfaces in the Pearl River Mouth basin of the northern South China Sea margin. The Pearl River Mouth typed rifted margin evolved from stretching, thinning, to finally seafloor spreading. Our results indicate that a distinct stratigraphic architecture with well defined unconformities are formed in the proximal to distal zone of the margin. The syn-rift strata have been constrained by the top of basement unconformity and the lithosphere breakup unconformity. Polyphase rift strata during lithospheric rupture process are mainly controlled by two fault patterns, high-angle normal faults and low-angle detachment faults. In the proximal domain, multiple episodes of syn-rift strata are characterized by vertical superimposed half-graben or graben type stratigraphic patterns separated by crack-related unconformity. However, in the more distal zones, syn-rift strata composed two distinct intervals separated by detachment-related unconformity, including small-scaled dispersed half-graben or graben at the lower part and large-scaled wide syn-detachment depression at the upper part. Based on these observations we provide an effective method for the correlation of sedimentary strata from the proximal to distal domains of the passive rifted margins during the lithospheric rupture process.