Xiashihezi Fm

The type section is located in the Shihezi Trench of the Chenjiayu area in the East Hills of Taiyuan City, Shanxi Province. It was named by Norin E. in 1922.

Synonym: Lower Shihhotse Fm

Clastics and Coal. In the type section the formation represents a suite of sandstone, shale, coal and manganese-iron-bearing river-facies clastic rocks, the sphere of which begins from the “Luotuobozi Sandstone” (Luotuobozi Greywacke) to the top of the “Taohua Shale”, with a thickness of 79-170 m. It is commonly subdivisible into two lithologic members. Lower member is 48-97.8 m thick, with its lower part consisting of the Luotuobozi Sandstone, and with its upper part consisting of yellow-green shale. In the Qiligou and Luotuobozigou areas of West Hills of Taiyuan City the Luotuobozi Sandstone is composed of three layers of yellow medium-, and coarse-grained sandstones (they are in ascending order the quartz-greywacke, the quartz-sandstone, and the feldspar-quartz-sandstone), intercalated with grey-yellow shale and thin-bedded coal layers, with a thickness of 21-27.8 m, which had merged into one layer while departing from the West Hills of Taiyuan City. Upper member is 66.3-72 m thick and represents interbeds of yellow-green medium- and coarse-grained feldspar-greywacke, quartz-greywacke and yellow-green shale, with its top part being possessed of two layers of bauxitic shales with oolitic texture. In Shanxi Province the sandstone-clay ratio in the Lower member is a bit higher than that in the Upper member, while in the Lower member there are well-developed siltstone and shale, intercalated in most cases with carbonaceous shale and thin coal layers, bearing a darker color. The siltstones in the Upper member are mainly yellow-green and apricot yellow in color, but with a poorly developed schistosity. There occur also manganese-iron-bearing and bauxitic siltstones, followed by the starting of occurrence of purple layers, with the sandstone-clay ratio reducing from north to south, and with the sandstones being changed from the yellow-white and grey-yellow ones to the brown-yellow and yellow-green ones, together with their granularity getting finer, and the composition and texture maturities are getting higher. The color of the shale (especially for that in the Upper member) is changing from being darker to being brighter, and from being grey-green- and yellow-green-colored to being apricot-yellow-colored. The “Taohua Shale” in the upper member has a better development towards south.

The thickest part of the whole formation is seen in the areas of Taiyuan and Yangquan Cities. It is getting thinner to both the southern and northern flanks of the region. In the southern part of North China, the Xiashihezi Fm (the Lower Shihhotse Fm) represents an important coal-bearing stratum which in the western part of Henan Province comprises the lower sandstone layer containing siltstone fragments and coaly debris, with a thickness of 10-20 m; the middle interbeds of thin-bedded medium-grained sandstone and sandy siltstone, containing ferruginous oolites or concretions, with a thickness of 50-60 m; and the upper grand purple stratum, with a thickness of 6-10 m, which is correlatable with the Xiashihezi (Lower Shihhotse) Fm in the vicinity of Taiyuan City.

In the area of the southern margin of North China the formation yields brackish-water animal fossils and charophyte fossils. For instance, in the Yongcheng area the hangers of coal seams in the three coal-bearing formations yield the Paracuneatochara yongchengensis; in the Xinan area of Henan Province it yields such brackish-water bivalves as Naiadites? sp. and insect fossils such as Aissoblatta brachyna, Ptytoblatta parviradia, etc. In the Yingshan area of Huainan region it yields such brachiopods as Lingula sp., etc.

It is interpreted as river-lake facies clastic deposits, with the coastal peat-bog facies being found only in the early stage of its formation. In the Pingding Mt. area of Henan Province to the Huainan area the formation represents delta-facies deposits.