Bangzhai Fm
Type Locality and Naming
The naming section is located in Bangzhaishan Mt., Sandu County, Guizhou Province, but the exact location of the section is unknown. Two new Dahekou and Tunshang Members in Dushan area were proposed by Wang Yu in 1964 in replaced of Bangzhai Fm. According to Guizhou Geological Survey, the name of Bangzhai Fm is commonly accepted. The lectostratotype is in the Dahekou to Tunshang villages by the Duliujiang River east of Dushan County ( 25°50' 17.73"N, 107°34' 50.67"E). It was named by Ting V.K. as Bangzhai Sandstone in 1929 and quoted formally by Grabau W. in 1931.
Synonym (translation option): Banzhai Fm.
Lithology and Thickness
Quartzite and Sandstone with limestone. The formation in the lectostratotype is subdivided into two members. Lower - Dahekou Member is dominated by thick-bedded to massive yellow and yellow brown quartz sandstone intercalated with a few gray thin-bedded siltstones, 137 m thick. Upper - Tunshang Member consists of sandstones intercalated with several beds of thin limestones and clayey limestones, 148.7 m thick. Some ferruginous sandstones with hematite are developed in the lower and base.
[Figure Outcrops of Dahekou Member (left) and Tunshang Member (right). Note the limestone interbed below the hammer (Courtesy of GuoWen). Length of hammer 28 cm.]
Relationships and Distribution
Lower contact
Conformable on the underlying Longdongshui Fm., the contact being placed at the change from limestone below to ferruginous quartz sandstone above.
Upper contact
Conformably with the overlying Jipao Member of Dushan Fm. The boundary is placed in the occurrence of a thick-bedded nodular limestone above.
Regional extent
This formation is mainly distributed in Dushan and Duyun areas of south Guizhou and the iron Ore mine area in Hezhang County of northwest Guizhou. The “Lantu quartz sandstone” in Lantu area of Sandu County (Ji Rongsen, 1939) and the “Mangshan quartz sandstone” west of Duyun City (Yue Senxun, 1929) probably are synonymous.
GeoJSON
Fossils
In the Tunshang Member yields brachiopod Bornhardtina sp., corals Dendrostella trigemme, Pseudomicroplasma fongi and only flora fragments are in the Dahekou Member.
Age
Depositional setting
It is interpreted as a sedimentary environment of back-fore to nearshore facies.
Additional Information