Changpo Fm

Hainan Geological Brigade was named in 1975. The named section is located in Changpo, Dan County, Hainan Province, and the reference section is drill hole ZK107 in the Changpo Basin.

The lithology is mainly gray, blue-gray mudstone, silty mudstone, clayey siltstone, intercalated with gray calcareous oil shale, carbonaceous oil shale and lignite, and contains a small amount of clayey rock and siderite. At the bottom, there are variegated conglomerate, glutenite, and clayey medium-coarse sandstone. It can be divided into upper, middle and lower parts: Lower part is composed of variegated calcium-bearing mudstone, sandy mudstone and gravelly muddy sandstone with blue-gray marl, and the bottom is sandy conglomerate with a thickness of 220 m; Middle part is mainly gray mudstone with Oil-bearing shale and lignite, with a thickness of 102 m; Upper part is gray mudstone, sandy mudstone and clayey sandstone, partially intercalated with marl, containing pyrite and calcareous clumps, with a thickness of 13 m. The total thickness of the group is 250-629 m.

The central part of the Changpo Formation is rich in fossils, mainly including fish Hypophthalmichthys sp. and Pseudobagrus sp; turtles Amyda sp.; crocodile Alligator sp.; gastropods Hydrobia sp., Bithynia sp., Amnicola sp., etc.; plant Phyllites sp., Betula sp., Alnus sp., Carya sp., etc.; Ostracods Cyprinotus cf. formalis, Ilyocypris cf. biplicata, Candoniella cf. albicans, etc.; pollen is the combination of Crassoretitriletes-Polypodiisporites-Quercoidites.

The Changpo Formation is a deposit of fluvial and lacustrine coal-bearing clastic rocks.