Zhuhai Fm

Pearl River Mouth Basin (offshore). The naming section is located in well Zhu 5 of the Xinjiang River depression, Pearl River Estuary basin, Guangdong, and the reference section is located in well EP17-3-1 of the Enping depression. Named by Zhong Shuixian et al. in 1981.

Located above the Enping Fm and below the Zhujiang Fm, the Zhuhai Formation consists of gray and grayish white sandstone with dark gray mudstone. The formation is divided in ascending order into three members: First member, grayish white, dolomitic, pebbly sandstone, sandstone and siltstone with blackish gray, grayish yellow and brownish red mudstone and black carbonaceous shale, 113.5 m thick; Middle member, light gray sandstone with blackish gray mudstone, oil shale, bituminous shale and lignite, 304 m thick; Third member, yellowish gray dolomitic sandstone and muddy fine sandstone alternating with blackish gray mudstone, intercalated with thin-bedded bituminous shale and oil sandstone, 313 m thick. The total thickness is 0–875 m. In the seismic section the formation is equivalent to the strata between reflectors T₈ and T₇.

Abundant sporopollen is contained in this formation, represented by the Alnipollenites-Pinuspollenites assemblage; while foraminifera and calcareous nannofossils are only found in the middle and upper parts of the horizon of a few wells: the planktonic foraminifera belong to the lower part of zone N4 and zone P22, mainly including Globigerina angulisuturalis, G. ciparoensis, Globorotalia opima and Globoquadrina dehiscens etc., and the benthic foraminifera are Uvigerina sp. and Textularia sp. etc.; the nannofossils belong to the lower part of zone NN1 and zones NP24 and NP25, mainly including Sphenolithus ciperoensis, Zygrahablithus bijugatus and Dictyococcites bisectus etc.

The lower part of this formation consists predominantly of continental deposits, which upward grade to paralic deposits.