Chengzihe Fm
Type Locality and Naming
E. Heilongjiang – Sanjiang. The Chengzihe Formation was designated by Chen Guangya in 1963. The section for the designation is in Didao of the Jixi City, Heilongjiang and its reference sections are down the boreholes (No.74-83, No.33, No.9) at Hadali of the Xinghua Village 20 km northwest of the Jixi City of the Heilongjiang Province. Middle formation in Jixi Gr.
G. Morita (1943) named the two coal beds in the middle and upper parts of the Didao Group. The intercalated coal beds designated in Jixi designated by Ren Ji (1950) included the Didao Fm and the Chengzihe Formation. Chen Guangya (1959) suggested that the intercalated coal beds did not include the Didao Fm. Gu Zhiwei (1962) called the coal-bearing beds in Jixi as the Jixi Formation. As the Jixi Fm and the Jixi Gr are duplicated names, Chen Guangya redesignated them the Chengzihe Formation in 1963. In 1982 Ju Ranhong and Zheng Shaolin et al established the Shihebei Fm by separating the paralic bed from the lower Chengzihe Formation in the Pingyang Town of the Jixi City. In 1989 when Zhang Hairi and Li Weirong were compiling the Geological Annals of Heilongjiang, they assigned the paralic bed of the lower Chengzihe Formation of the Boliji basin to the Shuguang Fm of the Longzaogou Gr. Lithostratigraphically the lower part of the Chengzihe Formation is not remarkably different from the continental bed above. Therefore, the paralic bed is still assigned to the lower part of the Chengzihe Formation when the stratigraphic unit entry is prepared.
Lithology and Thickness
The Chengzihe Formation is mainly continental sediments, of which the lower part is marked by paralic coal-bearing beds. It can be divided in ascending order into three parts: Lower part is represented by gray white medium and fine-grained sandstone, siltstone, mudstone and coal beds with marine intercalations. Middle part is gray white medium and fine-grained sandstone with siltstone, carbonaceous mudstone, tuff and coal beds. Upper part is gray white fine sands, siltstone interbedded with mudstone, with coal beds. The formation is 541 m thick and is an important coal-bearing formation in the region.
Relationships and Distribution
Lower contact
The lower limit is marked by a disconformity of quartzose conglomerate over the volcanic rocks of the Didao Fm.
Upper contact
The upper limit is separated from the boulder clay-bearing grit of the overlying Muling Fm by medium and fine-grained sandstone.
Regional extent
The present formation is mainly distributed in the Jixi, Boli, Shuanghua, Shuangyashan-Suibin and Hegang basins. It consists of siltstone and fine sandstone and grit on the west margin of the Jixi basin. Conglomerate or gravel-bearing sandstone are common in the lower and upper parts but coal beds are mostly seen in the lower part. The base limit is marked by conglomerate that lies unconformably over the Paleozoic granite. The formation is 200-300 m thick. In the central and eastern parts of the basins, sandy mudstone is predominant, and the area with the Jixi and Muling basins as the center of deposition can be divided into two zones, the northern and the southern. The southern zone proceeds from Guangyi to Honghuo through Muling where the lithology can be divided into three parts: the upper, middle and lower, with the base mostly built up by conglomerate and gravel-bearing grit, ranging from 400 to 1400 m in thickness. The northern zone proceeds from Huotonggou in the west to Heitai through Didao, Jixi, Chengzihe and Donghai, with the base mostly built up by conglomerate that lies unconformably over the volcanic rocks of the Didao Formation. In the Boli basin, the Chengzihe Formation is widely distributed, of which the characteristic features are exactly the same with that of the Jixi basin. Only difference is that the coal-bearing characters of the Jixian Coalfield south of the Songhua River are not so good. In the Hegang basin, the strata that are equivalent to the present formation are called the Shitouhezi Fm. During the stratigraphic sorting of Heilongjiang (1994), the Shitouhezi Fm was discarded because it was of the same lithology but different names from the Chengzihe Formation.
GeoJSON
Fossils
It yields floras Coniopteris onychiodes, C. hymenophylloides, Onychiopsis elongata, Acanthopteris gothani; Dinoflagellates Oligosphaeridium comples, Muderongia tetracantha, Palaeoperidium cretaceum in the Pingyang Town; Angiosperms Asiatifolium elegans, Chengzihelia obovata, Jixia pinatipartita, Rogersia lanceolata on the north bank of the Muling River of Jixi; bivalves Aucellina caucasica, A.optiensis, A. eletzkii; and sporopollen Appendicisporites crimensiis, Impardecispora apiverrucata, Pilosisporites verus, Triporoletes involucratus, etc. in Ronghua and Pingyang of the Jidong County.
Age
Depositional setting
It is suggestive of paralic facies in the lower part and lacustrine bog facies in the middle and upper parts.
Additional Information