Miocene–Pliocene planktonic foraminiferal biostratigraphy of the Pearl River Mouth Basin, northern South China Sea

The present study deals with the planktonic foraminiferal biostratigraphy of the Miocene–Pliocene sequence of three petroleum exploration wells (BY7-1-1, KP6-1-1 and KP9-1-1) in the Pearl River Mouth Basin (PRMB). In general, the three wells contain a fairly well-preserved, abundant foraminiferal fauna. The proposed planktonic foraminiferal zonation follows the scheme updated by Wade et al. (2011). Nineteen planktonic foraminiferal zones have been recognized, 14 zones (zones M1–M14) for the Miocene and 5 zones (zones PL1–PL5) for the Pliocene. The zonation is correlated with previously published biostratigraphic subdivisions of the Neogene succession in the PRMB and with international foraminiferal zonations. The zonal boundaries are mostly defined by the last appearance datum of zonal taxa of planktonic foraminifera, which is more reliable than the FAD (first appearance datum) events for ditch cutting sampling. Changes in the coiling of Globorotalia menardii (s. l.) are also used to define the zonal boundaries, where no LADs (last appearance datum) are available. The Fohsella fohsi group, comprising useful taxa for delimiting zonal boundaries of the middle Miocene in other areas, has a poor record within the Pearl River Mouth Basin due to unfavorable ecological conditions, and cannot be used for the studied wells. Different from the previously reported zonal scheme for the PRMB, the present zonation is based on correlation with the current standard planktonic foraminiferal zonation, with calibrated absolute ages.