Changcai Fm

Its basal part is unconformably marked by the appearance of breccia and separated from the underlying Tuntianying Fm (Barremian), or the Paleozoic Anshan Gr,.

Its top is unconformably bounded by gray sandstone and separated from the volcanic rocks of the overlying Quanshuicun Fm unit at base of the general regional Tongfosi Fm.

This formation is distributed in the Songjiang, Helong, Fudong, Antu and Yanji basins. The basal conglomerate beds mainly occur on the margin of the Songjiang basin with a thickness of 136.6 m. The thickness of coal beds vary greatly, they are 2 m thick on the southern side of the Xiaosha River and thinner ranging from 10 to 50 cm in the Yangmutiaozi area. In the lower part of the Helong basin conglomerate beds are up to 205.7 m thick and the upper part is composed of microclastic rocks and coal beds, where there are more than 10 mineable coal beds with a thickness of 103.8 m. From Xishanping to the Wuming Coal Mine of the Fudong basin, conglomerate, sandstone, shale and coal beds constitute two normal cycles. The coal beds occur in the upper cycle but they vary greatly and are not persistent in thickness in the lower cycle. Yang Xuelin (1959) named the lower cycle as the Xishanping Fm. In the Changcai area, microclastic rocks are dominant with presence of andesite intercalations, and the lower cycle beds are absent. In the Mingyuegou area of the Antu basin, the Changcai Formation consists of tuffaceous gravel-bearing sandstone and tuffaceous conglomerate with siltstone, being 280 m in thickness. In the Tuntianying basin, the formation occurs in the Tuntianying area, which is dominated by microclastic rocks with coal beds, being 350 m thick. The coal beds were named as the Dahuangdi and Meiyaogou coal measures by the No.102 Coalfield Team (1954). In the Baicaogou area, the formation is 200 m thick. Its basal part is represented by thick-bedded tuffaceous conglomerate; its middle part fine sandstone and shale with coal beds; and its upper part sandstone and shale. In the Diyingou basin, the formation is dominated by tuffaceous sandstone and tuffaceous conglomerate with small amounts of intermediate pyroclastic rocks, ranging from 80 to 150 m in thickness. In the Jiaohe basin, the formation occurs at the eastern edge of the basin and is composed of two cycle beds. Conglomerate is not so developed in the lower part of the lower cycle and the coal beds are mostly compound coal beds (8 beds), generally 1 m thick. The lower part of the upper cycle bed is built up by conglomerate and gravel-bearing grit with a thickness of 70 m. In the lower part, the coal beds are quite thin or occur as coal streaks. In the Daguanmenlazi area, both the upper and lower cycles are mostly built up by macroclastic rocks, with a few number of coal streaks, measuring 1743 m in thickness. Y. Mizumura (1936) named the upper and lower coal measures as the Naizishan and Sansonglafa coal bed groups respectively. The Northeast Mesozoic Stratigraphic Study Team (1963) named the Niaolinshan Fm and the Naizishan Fm. However, Zhang Youjun, Han Qinglin et al. (1964-1971) called them as the Zhonggang Fm owing to the coal measures are developed near the Zhonggang area. During the stratigraphic sorting of Jilin (1994), the Niaolinshan Formation and the Naizishan Formation were combined together and collectively called the Changcai Formation.