Buxin Fm

The naming section is located in the Honggang quarry, Dalang Mountain, ~4 km north of Hekou Township, and in well CK2 at Buxin Village ~4 km northeast of Hekou Township, Sanshui, Guangdong. The reference section is located in well Baoyueshui No. 8, ~4 km north of Sanshui County and in well ZK52 at Dalang Mountain, Sanshui County. Named by Tang Xing, Liang Baochang and Zhou Mingzhen in 1964–1965.

Broadly subdivided into three members: Lower member: gray, brownish gray and brownish red sandy conglomerate, grayish black and gray mudstone, clayey sandstone and marlstone. Middle member: dark gray and grayish black mudstone with sandstone, clayey sandstone and marlstone, locally containing oil shale. Upper member: alternating beds of grayish brown and dark gray mudstone and grayish brown and light gray sandstone and clayey sandstone. Its outcrop thickness at the surface is ~140 m and that in the well may reach 950 m.

Fishes are dominated by the Tungtingichthys-Mystus (or Aoria)-Osteochilus assemblage; gastropods include Parhydrobia, Lioplax and Bellamya; ostracods are mainly the Sinocypris-Limnocythere-Cyprois assemblage; conchostracans are Fushungograpta, Paraleptestheria etc.; plants have Cinnamomum and Plibinia, as well as the charophytes assemblage Gyrogona-Peckichara-Stephanochara. As for the age of Buxin formation, according to the analysis of bemalambdids found in Guanyao Town, Nanhai, fishes and other symbiotic biota found in Sanshui, it is more appropriate to determine the age from Paleocene to early Eocene.

Lacustrine deposits.