Reassessing two contrasting Late Miocene-Holocene stratigraphic frameworks for the Pearl River Mouth Basin, northern South China Sea

Abstract

High-resolution 2D/3D seismic and biostratigraphic data are used to reassess two contrasting Late Miocene-Holocene stratigraphic frameworks (SFI and SFII) for the northern slope of the Pearl River Mouth Basin (PRMB), northern South China Sea. The major stratigraphic boundaries (T1-base Quaternary and T2-base Pliocene) derived from SFI and SFII are different in depth. The trends of average sedimentation rates from Late Miocene to Quaternary were estimated according to the major boundaries in order to highlight the differences between these two frameworks. The seismic reflection terminations as erosional and truncation features were recognized through the seismic data implying that the submarine channels and mass-transport deposits are valid stratigraphic markers of Late Miocene-Holocene basin development on the northern South China Sea margin and other continental margins. The sediments from hydrate drilling sites in the Shenhu Area consist of two allochthonous sedimentary units with similar lithology and grain sizes: a) fine-grained turbidites at the bottom, and b) fine-grained submarine landslides at the top. Nannofossil assemblages with relatively minute sizes were likely to be reworked due to the setting of widespread mass wasting on the middle to lower continental slope. A key result of this study is that the stratigraphic framework based on a combination of seismic and sequence stratigraphic data is more suitable for stratigraphic correlations across the northern slope of the PRMB. Our findings provide a robust foundation to rebuild the tectono-sedimentary evolution of the PRMB and also resolve the uncertainties in the Late Miocene-Holocene stratigraphic frameworks of the study area.