Tuanshanzi Fm
Type Locality and Naming
Jixian County, Tianjin. The Tuanshanzi Fm was named by Chen Jinbiao in 1963. The type section is in Xishan Mt. -Xiaonanshan Mt. near Tuanshanzi Village, Xiaying Township, Jixian County, Tianjin Municipality.
Synonym: （团山子组）
Lithology and Thickness
The Tuanshanzi Fm is dominated by Fe-bearing dolomite, silty microcrystalline dolomite, sandwiched with grey-yellow sandstone and minor green silty shale. It is subdivided into three lithologic members. First member is dominated by dark-grey ferruginous dolomite and silty siderite dolomite. Second member has a lower part of thin-interbedding of grey-yellow calcareous fine-grained sandstone or siltstone with dark- grey thin-bedded argillaceous and arenaceous dolomite; with scour molds often seen in base surfaces of calcareous siltstone and desiccation cracks and pseudocrystals of halite sometimes seen. The upper part of the second member is dark-grey medium- to very-thick-bedded dolomite, sandy microcrystalline dolomite, sometimes with cross-bedding and ripple marks. Third member is purple platy-bedded, sandy microcrystalline dolomite, sandwiched with grey-yellow sandstone and green-shale, in which the desiccation cracks, ripple marks and pseudocrystals of halite are seen on their bedding surface. The total thickness is recorded to 479 m.
Relationships and Distribution
Lower contact
It is in conformable contact with the underlying Chuanlinggou Fm.
Upper contact
It is in conformable contact with Gaoyuzhuang Fm.
Regional extent
Tianjin, Hebei, west Liaoning. It is widely distributed in the Yan-Liao (Yan-shan-Liaohe) area. In western Liaoning, its distribution area is similar to that of Chuanlinggou Fm, but it is subdivided there only in-to upper and lower parts. The lower part of the formation is dominated by carbonate rock, but the upper part, clastic rock (260-624 m thick). It is developed completely in Lingyuan (624 m thick) where it bears rich microplants. But it is obviously thinned in Yixian and Chaoyang counties (337 m, 340 m respectively). In east sector of Yanshan Mountain, in Xinglong, Kuancheng and Pingquan it is dominated by dolomite (202-300 m thick). In Zunhua, Qian'an, Luanxian (69 m) the clastic rock increases; in west sector of Yanshan Mt., in the area of Badaling and Xuanhua (57-167 m thick) it is dominated by dolomite, but sandwiched with volcanic rock or volcaniclastic rock in the top part.
GeoJSON
Fossils
The first member contains multicellular macro-algae, such as Tuanshanzia fasciara, Changchengia stipitata, The second member yields stromatolites Kussiella tuanshanziensis, Stratifera f., microplants Asperatopsophosphaera bavlensis, Pseudozonosphaera verrucosa etc. The stromatolites in third member are Gruneria cf. biwabikia etc. Microplants in Lingyuan are Leiopsophosphaera crassa, Polyporata obsolete. Stromatolite at Badaling is Conophyton rugiforme.
Age
Depositional setting
Additional Information
The paleomagnetic polarity during deposition of the Tuanshanzi Fm was negative, and the paleomagnetic pole was -7.2°N, 69.4° (Zhang Huiming et al., 1991).