Ximatang Fm
Type Locality and Naming
Yin Zanxun named this formation in 1937. The named section is located in Ximatang, Qiubei County, Yunnan Province, and the reference section is located near south of Xinnongzhuang, east of Longgaxinzhai, Qiubei County, Yunnan Province. Yin (1937) named this formation, which original named “Ximatang Shale”, and is similar to the “Feixianguan Shale” in Sichuan Province. It was dated to the Lower Triassic, and the fossils were studied by Yin and Xu Deyou (but the original manuscript was lost), the list was later published by Xu (1938). In 1961, Chen Chuzhen et al. remeasured the section of the “Ximatang Shale”, which was renamed the Ximatang Fm and dated to the early Early Triassic. In 1962, Zhao Jinke et al. redefined the Ximatang Fm and dated in early Early Triassic.
Synonym:
Lithology and Thickness
Lower part is lime green, yellow, yellow green shale, sand shale, with grey limestone. Upper part is grey thin layer siltstone, purple, yellow mudstone, with oolitic limestone, limestone. Total thickness is 421 m
Relationships and Distribution
Lower contact
The bottom boundary is marked by yellow green shale, which is in conformable contact with the underlying Yongningzhen Fm of Olenekian.
Upper contact
It is in conformable contact with the overlying Changxing Fm of Upper Permian.
Regional extent
Mainly distributed in the Nanpanjiang, Wenshan and Mile areas, southeast of Yunnan, with regional thickness varying from 126 m to 646 m. Yellow shale and marl in the Qiubei; Eastern to Guangnan, thick limestone and oolitic limestone are dominant, and the contact relationship with the underlying Changxing Formation of the Upper Permian is dominated conformable, and the local area is disconformity.
GeoJSON
Fossils
Rich in bivalve fossils, the important ones are Towapteria scythica, Pseudoclaraia wangi, Claraia griesbachi, C. aff. aurita, C. aff. intermedia, C. aff. kuichowensis, Eumorphotis multiformis, E. cf. Inaequicostata. Ostracoda: Hollinella tingi
Age
Depositional setting
This formation is a shallow water deposit.
Additional Information