Late Cenozoic high resolution bio-stratigraphy and its bearing on sea-level fluctuation in the western Pearl River Mouth Basin

The Neogene in the Western Pearl River Mouth Basin is dominated by neritic shelf sediments, in which favorable marine sand reservoirs and multi-sets of reservoir-cap combinations are discovered. Therefore, it is the key to study the sea-level changes which control the origin and position of sand bodies. In order to understand the sea level changes, a chronostratigraphic framework of the western Pearl River Mouth Basin has been set up based on the abundance and percentage of foraminifera and calcareous nannofossils (>0.25mm) combined with bio-events and age data, lithological data, logging data and seismic data. Single well analysis of sequence stratigraphy is carried out for the data from eighteen wells. Two 2nd-order sequences and 15 3rd-order sequences are identified. The sea-level change curve was then established in cooperation with the study of the ancient ecological facies and depositional structures as well as the on-lap relationship, recognized on the reflection seismic profile. Paleo-water depth was quantified through comparison of the fossil foraminifera to present species in the western South China Sea, for which the living conditions are known. The Neogene in the western part of the Pearl River Mouth Basin is affected by the continuous subsidence during the depression stage and a stepped transgression sequence is formed, different from the sequences formed in global regressive stages.