Yangzhuang Fm
Type Locality and Naming
Jixian County, Tianjin. The Yangzhuang Fm was named by Gao Zhenxi (Kao, C. S.), Xiong Yongxian (Hsiung, Y. H.) and Gao Ping (Kao,P.) in 1934. The naming locality is the Yangzhuang Village, 10 km north of Jixian County, Tianjin Municipality.
Synonym: （杨庄组）
Lithology and Thickness
The formation is strongly characterized by abundance of gypsum, halite pseudocrystals and a tint of purple-red color. It is dominated by carbonate rock and subdivided into three members. First member, 209 m thick, is an interbedding of purple-red thick-bedded sandy dolomitic limestone and grey-white cherty dolomitic limestone. Second member, 434 m thick, consists of purple-red muddy dolomitic limestone accompanied with grey-white terrigenous clastic dolomitic limestone in. Third member, 130 m thick, is composed of interbedding of dark-grey bituminous fine-crystalline dolomite and purple-red microcrystalline dolomite. The total thickness is 773 m.
Relationships and Distribution
Lower contact
The base of the formation is marked by basal surface of a white silty, muddy dolomite that contacts with a disconformity onto the underlying Gaoyuzhuang Fm.
Upper contact
Conformable with Wumishan Fm
Regional extent
Tianjin, Hebei, west Liaoning. The formation is distributed in Yanshan Mountain and Liao-he drainage area. It is distributed in limited area and is thinned in north segment of Yanshan Mountain, such as only 413- 192 m in Xinglong-Pingquan counties. In the west segment, it is quickly thinned or pinched out in Badal-ing-Zhuolu (78-42 m thick), and is dominated by sandy-muddy dolomite. In the east segment, in Fengrun-Qianan-Luanxian it is gradually thinned (707-181 m), where the clast content increases. In western Liaoning Province, it is 541 m in Lingyuan, 403 m in Harqin Zuoqi, 309 m in Chaoyang, 334 m in Jinxi, 321 m in Yixian, 456 m in Xingcheng. It varies slightly in lithological character, with only the red dolomite having a larger change. It thins both from south to north and from west to east. For example, it is 266 m thick in Lingyuan, but only 26 m in Wafangdian and Xijinggou.
GeoJSON
Fossils
Stromatolites in the formation are Microstylus zhaizhuangensis, Yangzhuangia columnaris etc. Microplants: Asperatopsophosphaera umishanensis, Pseudozonosphaera verrucosa etc.
Age
Depositional setting
Additional Information
When the Yangzhuang Fm deposited the paleomagnetic polarity was negative, and the paleomagnetic pole was at 16.5°N, 42.5° (Zhang Huimin et al., 1991).