Wenchang Fm

Pearl River Mouth Basin (offshore). The naming section is located in WC19-1-2 well in the Wenchang depression of the Pearl River Estuary basin, Guangdong; the reference section is WC19-1-3 well. Named by the Western South Sea Branch, China National Offshore Oil Corp. in 1985. The stratotype section of the Wenchang Formation is represented by the 2986–3331 m interval of the well WC19-1-2, located between the Shenhu Fm and Enping Fm.

It is a sequence of lacustrine grayish black and brownish gray mudstone with light gray sandstone. Lower part consists of alternating beds of gray sandstone and grayish black, dark gray mudstone, with a few conglomerate beds. Upper part consists of light brownish red, grayish black and brownish gray mudstone with minor light gray sandstone and coal beds. The sandstone is poorly sorted and rounded, being mainly feldspar lithic sandstone feldspathic debris sandstone; mudstone is pure, without calcium, containing significant quantities of siderite grains. The total thickness is 0–912 m. At the seismic section this formation is equivalent to the reflector group between T₈–T₉.

This formation is rich in sporopollen, represented by the Quercoidites- Pentapollenites assemblage. In HJ15-1-1 well in the Hanjiang depression there occur small quantities of calcareous nannofossils such as Discoaster barbadiensis, D. kuepperi, Reticulofenestra umbilica and Tribrachiatus orthostylus.

It is lacustrine deposits.