Xiacun Fm

Its basal part is in a conformable contact with the underlying Wenbinshan Fm, but with a disconformable or an unconformable contact between them in some regions.

Unconformably overlain by the Fankeng Fm volcanics.

Coeval with the lower part of the Lishan Fm in this same region. It is distributed essentially in southern Fujian with greater variations in its lithology, rock facies and their thickness in various regions. In the Wuping-Shanghang region the formation is composed largely of grey-black thin-bedded siltstone and quartz-sandstone, intercalated with quartz-gritstone, pebble-bearing sandstone, carbonaceous mudstone and coal beds, yielding bivalve fossils, with a thickness of 74-400 m; in the area of Longshan Mts of Nanjing County to Gekou of Anxi County, the formation is composed mainly of medium-, and fine-grained quartz-sandstone, arkosic quartz-sandstone, siltstone and carbonaceous siltstone, intercalated with many layers of volcanic clastic deposits, yielding bivalve fossils, with a maximum thickness of 2346 m; in the area of the Xiangya Village, Yongan County the formation represents marine-continental alternating-facies microclastic coal-bearing deposits, yielding bivalve fossils as represented by Retroceramus heyuanensis and Parainoceramus matsumotoi, with a thickness of only 31 m; and in the vicinity of the Hukou Village of Xinqiao Township, Changding County the formation is composed of violet-grey and brown gritstones, light-grey and dark-grey medium-, and fine-grained sandy conglomerates, sandstones, siltstones, sandy and calcareous mudstones, intercalated with thin coal beds, yielding bivalve fossils as represented by the Lilingella xinyumensis-Hunanella ovata assemblage, in addition to Ostracods and plant fossils, with a thickness of about 668 m.