Xinzhuangcun Fm

Pearl River Delta. The naming section is located in well ZK52 at Dalangshan, Sanshui, Guangdong. Named by Zhang Xianqiu et al. in 1978.

Synonym: Xinzhuang Fm

Dark purplish red sandy conglomerate and brownish red or dark gray mudstone and siltstone with gypsum, mirabilite and halite beds. The formation is divided into three lithological members. Lower member, called the Mafang Member, is dark red conglomerate, sandy conglomerate and pebbly muddy sandstone, with some gypsum concretions, ~60 m thick. Middle member, called the Dakeng Member, is marked by dark red muddy siltstone with light blackish gray equivalents in the lower part and blackish gray mudstone with dark red lime siltstone in the upper part, both parts containing gypsum, with a thickness of 50 to 82 m. Upper member, called the Genkeng Member, consists of alternating dark red or dark purplish red and dark gray or blackish gray lime mudstone, marlstone and muddy siltstone, 70–80 m thick. The middle and lower parts of the member are intercalated with gypsum beds; the base is separated from the Dakeng Member by purplish red muddy siltstone with lime concretions; and at the top there commonly occur light gray siltstone and fine sandstone with cross bedding, sometimes intercalated with oil shale. The lithology and thickness vary greatly. From the basin center to margins, fragments become coarse, gray beds decrease and sandy conglomerate increases. The thickness of the formation varies greatly from 40 to 820 m.

This formation contains abundant ostracods, gastropods and charophytes, as well as foraminifera, fishes, bivalves, conchostracans and sporopollen. The ostracods are represented by the Eucypris sanshuiensis-Parailyocypris changzhouensis-Limnocythere dalangshanensis assemblage; the charophytes are abundant and have a great variety of genera and species, totaling 21 genera and 76 species, called the Grovesichara changzhouensis-Peckichara longa-Stephanochara breviovalis assemblage; The conchostracans is paraleptestheria manglaensis; the sporopollen occurs in the upper part of the formation, represented by the Ulmipollenites-Plicapollis-Pentapollenites assemblage; the fishes are only Tungtingichthys gracilis. In addition, the foraminifera Triloculina, Discorbis, Nonion and Nonionella are found in thin sections. The age of this formation had been assigned as Early Paleocene.

The formation consists dominantly of lacustrine deposits and there are piedmont diluvial deposits on the basin margins.