Zhangshu Fm

The naming section is located at Linjiang Township ~15 km southwest of Zhangshu Township and the reference section is in well Qing 12 of Qingjiang County.

Synonym: The Zhangshu Formation was originally the Linjiang Fm. The latter name was given by the Jiangsu Bureau of Geology in 1961 and formally used in 1963 (Zhang Yuping and Tong Yongsheng, 1963). The name Linjiang Formation is confused with a related Proterozoic horizon; so it is proposed that it be renamed the Zhangshu Formation.

Lower part is purplish brown and purplish red sandy mudstone with sandstone. Upper part is purplish red sandy mudstone and muddy sandstone with bluish gray or grayish green muddy sandstone, sandstone, marlstone and oil shale. The total thickness is ~350–400 m.

This formation yields relatively abundant fossils but these fossils have not been studied intensively. According to the records, now the fishes Leucisus sp. and Aoria sp. and Clupeiformes have been found; the ostracods are the assemblage mainly of Limnocythere and Cyprois; the gastropods are Australobis and Physa; the charophytes are mainly Grovesichara cf. yangi, Hornichara linjiangensis and Obtusochara jiangsuensis. According to He Yueming and Sun Xiangjun (1977), the pollen of gymnosperms in the sporopollen assemblage has a relatively high content, accounting for ~40% of the total, and especially the pollen of Pinaceae is dominant, making up 75–80% of the gymnosperm content at most. This feature reflects that the air temperatures were much lower than those of its underlying Xinyu Gr.

It is mainly lacustrine deposits, with occasional fluvial deposits.