Sidingshan Fm

North-central Anhui. The name Sidingshan Fm derived from the Sidingshan Series named by Xu Jiawei in 1958. The naming locality is situated at Sidingshan north of Shouxian County, and the reference section is in Diangeda to Bai'eshan, Shouxian County, Anhui Province.

Synonym: （四顶山组）

The Sidingshan Fm is dominated by medium- to thick-bedded stromatolite-bearing dolomite, and is subdivided into three lithologic members. Lower member is white gray, pink and grayish pink, medium- to thick-bedded dolomite and pelitic dolomite. Middle member has two parts. The lower part consists of gray to yellowish gray, medium bedded siliceous dolomite (with pisolitic chert) and pelitic dolomite, intercalating with lenses of quartzose sandstone in the basal part. The upper part is pink to purple gray thin-bedded pelitic dolomite, siliceous dolomite and calcareous siltstone. Upper member consists of light gray and gray thick-bedded dolomite with chert nodules and bandings. The thickness varies from 274 to 321 m.

Lower member yields stromatolites Inzeria shouxianensis, Boxonia cf. melrosa, B. songjiensis, Conophyton lijiadunensis, Gymnosolen f., Jurusania f. etc. The upper part of the middle member yields stromatolites Linella f. and microplants Laminarites antiquissimus, Taeniatum simplex, Leiopsophosphaera sp. etc. Upper member yields stromatolites Gymnosolen f., Tungussia f., Baicalia etc., and microplants Trematosphaeridium cf. holtedahlii, Polyporata obsoleta etc.

The Sidingshan Formation is restricted in the limits of the lower member, with the middle and upper members using separately the Niyuan Fm and the Jiudingshan Fm in Huaibei area (North of Huaihe River) by the Anhui Party of Regional Geological Survey in 1979. In view of the original meaning of the Sidingshan Formation and the disputed problems of the stratigraphic sequence and correlation in Xuhuai area, this Lexicon proposes to retain the original definition of the Sidingshan Formation made by Zhu Zhaoling et al. in 1964.