Changchang Fm

The Guangdong Regional Survey Party erected the Changchang Group in 1964, but no stratotype section was indicated when the group was named. The reference section is located ~400 m northwest of Paipo Village in a coal mine, Changchang basin, Qiongshan County, Hainan.

Changchang formation refers to 19.5 ~ 369.80 m section of well CK106 in Changchang basin. Its Lower member (variegated member) consists of unequal-thickness alternating beds of grayish white and grayish black sandstone and sandy conglomerate and gray, grayish green and purplish red, very fine sandstone and mudstone; its Upper member (coal-bearing member) is marked by alternating beds of grayish black oil shale and grayish white grit with coal beds in the upper part and grayish white and grayish black oil shale, coal beds, brownish red mudstone and grayish white grit and sandy conglomerate. The thickness is 322 m in well CK106 of the Changchang basin. The lower member is uniform in lithology, 250 ~ 320 m thick, while the upper member varies relatively greatly in thickness from 25 to 230 m and its lithology is also variable. The central part of the basin contains significant quantities of carbonaceous shale and coal beds.

The formation contains abundant plants and sporopollen in addition to fishes. The plants are Osmunda lignitum, Nelumbo protospeciosa, Cinnamomum larteti and Sabalites szei. Sporopollen may be divided into three assemblages, which are in ascending order: Porocolpopollenites miikensis-Polypodiaceaesporites haardti, Abietineaepollenites-Momipites triletipollenites-Operculumpollis operculatus and Alnipollenites-Quercoidites- Liquidambarpollenites. The assemblage in the upper part ranges into the lower part of the Wayao Formation.

The Changchang Formation consists of fluvio-lacustrine-swampy coal-bearing deposits.