Deep-water Depositional Features of Miocene Zhujiang Formation in Baiyun Sag,Pearl River Mouth Basin

Eleven lithofacies and five lithofacies associations were indentified in the Miocene Zhujiang Formation on the basis of detailed core analysis. It could be determined that three depositional types developed, namely submarine fan, basin and deep‐water traction current Six microfacies were further recognized within the fan, including main channels in the inner fan, distributary channels in the middle fan, inter‐channels, levees and the outer fan. The lower Zhujiang Formation, mainly sandstone associations, was inner fan and inner‐middle fan deposits of the basin fan and the slope fan. The middle part, mainly mudstone associations, was outer fan deposits. With the transgression, the submarine fan was finally replaced by the basinal pelagic deposits which were dominated by mudstone associations, siltstone associations, and deep‐water limestone associations. During the weak gravity flow activity, the lower channels, the middle‐upper outer fans and basin deposits were strongly modified by the deep‐water traction current. The identification of the deep‐water traction deposition in Miocene Zhujiang Formation would be of great importance. It could be inferred that the deep‐water traction current had been existing after the shelf‐break formation since the Late Oligocene (23.8 Ma) in the Baiyun sag, influencing and controlling the sediment composition, the distribution, and depositional processes. It would provide great enlightenment to the paleo‐oceanic current circulation in the northern South China Sea.