Huayong Fm

The naming section is located in well Huayongshui No. 3 in Nanhai City, Guangdong. Named by Zhang Xianqiu et al. in 1973.

This formation refers to a sequence of clastic rocks and volcanic rocks above the Baoyue Formation. Lower part, called the Xiqiaoshan Member, is composed of grayish white and grayish purple sandy conglomerate, pebbly sandstone and siltstone alternating or interbedded with pyroclastic rocks, rhyolite, trachyte and basalt, 600–1000 m thick. Upper part, called Quanxinggang Member, consists of brick-red and brownish red sandy conglomerate, pebbly sandstone, siltstone and mudstone with small amount of basalt or tuffaceous sandstone, 333 m thick. Its lithology and thickness vary relatively greatly: from the center to margins of the basin, clastic rocks become coarse and the layer number and thickness of volcanic rocks decrease rapidly and even volcanic rocks completely disappear. The top of the formation has been subjected to different degrees of erosion and the remaining thickness is 275–1070 m.

This formation contains abundant ostracods and gastropods, in addition to bivalves, fishes, charophytes, sporopollen and plants. The ostracods are represented by the Sinocypris reticulata-Limnocythere lata assemblage and Limnocythere xiaotangensis-Cyprois circularis assemblage; the gastropods are Nanhaispira eversilabia, Australorbris sp., Gyraulus sp. etc. the charophytes are the Hornichara huachongensis-Amblyochara taixianenesis assemblage; the sporopollen is the Alnipollnites-Polypodiaceaesporites-Momipites assemblage.

This formation belongs to the terrestrial clastic-volcanic formation of eruptive facies and fluvial alluvial facies.