Baoyue Fm

The naming section is from Zhushangang No. 23 well, Sanshui, Guangdong Province. Named by Zhang Xianqiu in 1978.

The Baoyue Formation refers to a sequence of red clastic rocks between the Buxin and Huayong formations. Lower part, 192 m thick, consists of unequal-thickness, alternating beds of dark gray and purplish gray, calcareous mudstone and calcareous siltstone, with purplish gray and light gray fine sandstone and medium-coarse sandstone, containing pebbly sandstone and sandy conglomerate. Middle part, 306 m thick, is composed of purplish gray and brown siltstone and fine sandstone with sandstone, pebbly sandstone and mudstone. Upper part, 326 m thick, has alternating beds of purplish red, brownish red and light gray sandy conglomerate, pebbly coarse sandstone and very fine sandstone, with variegated mudstone. Its lithology and thickness vary greatly and the rocks in the Sanshui basin have a tendency to become fine from south to north. The strata are thickest in the Huayong-Baoyue area, being ~800–1100 m thick, and from there the strata become thin outward rapidly.

It contains abundant ostracods, gastropods and bivalves, and in addition it also contains fishes, charophytes, sporopollen and plants. Ostracods are represented by the Cyprois reniformis-Cypris henanensis assemblage; gastropods mainly include Amnicola xiagangensis and Brachyspira subsphaerica etc.; charophytes are marked by the Neochara huananensis-Peckichara subspheria assemblage; sporopollen mainly occurs in the middle and lower parts of the formation, represented mainly by the Quercoidites-Cupuliferoidaepollenites-Ulmipollenites undulosus-Pentapollenites maomingensis assemblage. The horizon of Bemalambda fossils found in Guanyao, Nanhai, is considered by somebody to be the Baoyue Fm; from the properties of the fossils, however, it is very likely to occur in the Buxin Fm.

This formation belongs to a regressive sequence characterized by the transition from lacustrine facies to fluvio-alluvial facies.