Reassessing two contrasting Late Miocene-Holocene stratigraphic frameworks for the Pearl River Mouth Basin, northern South China Sea
Marine and Petroleum Geology(2019)
Abstract
This work reassesses two contrasting Late Miocene-Holocene stratigraphic frameworks for the Pearl River Mouth Basin (PRMB), northern South China Sea. Two distinct stratigraphic frameworks based on seismic-stratigraphic (SFI) and biostratigraphic (SFII) data are compared in terms of their applicability and accuracy. In order to stress the differences between both frameworks, major stratigraphic boundaries (T1-base Quaternary and T2-base Pliocene) derived from SFI and SFII were revisited and described. Sedimentation rates estimated for the two frameworks, complemented with published data, indicate that average sedimentation rates and trends for SFI match the regional reference data for Quaternary strata. In terms of well-seismic ties, two allochthonous sedimentary units with similar lithology and grain sizes were identified as comprising fine-grained turbidites at the bottom, and fine-grained sediment failures at the top, revealing widespread mass wasting on the middle to lower continental slope. In such a setting, nannofossil assemblages accumulated on the continental slope were likely reworked because of their relatively minute sizes. Sediment cores with low recovery rates collected during a first hydrate expedition in 2007 have led to important misunderstandings when defining the first and last appearances for nannofossil species. Hence, stratigraphic framework I (SFI) - based on a combination of seismic and sequence stratigraphic data - is suggested as more suitable to attain stratigraphic correlations across the continental slope of the PRMB. Our findings can resolve the ambiguities and uncertainties arising from the two contrasting stratigraphic frameworks, providing a robust foundation to reassess the tectono-sedimentary evolution of the PRMB, South China Sea.
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Key words
South China Sea,Pearl River Mouth Basin,Stratigraphic correlation,Stratigraphic boundaries,Late Miocene-Holocene,Submarine canyons
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