Tieling Fm
Type Locality and Naming
Jixian, Tianjin. The Tieling Fm was named by Gao Zhenxi (Kao, C. H.), Xiong Yongxian (Hsiung, Y. H.) and Gao Ping (Kao, P.) in 1934. The type section is at Tieling Village, 5 km north of Jixian City, Tianjin Municipality.
[Figure: The Tieling Fm in the Jixian section. a-Stromatolite reef; b-c-d-Glauconite grains in between stromatolites]
Synonym: （铁岭组）
Lithology and Thickness
The Tieling Fm is composed of limestone and dolomitic limestone of tidal zone. The formation is subdivided into two members or subformations. The base of first member (Daizhuangzi Subformation; 153 m thick) is composed of medium- to thick-bedded sandstone, replaced upward by interbedded of shale and Mn-bearing dolomite, and with an upper part of variegated shale, where small-scale stromatolite reefs are abundantly developed, culminating in a top of unstable siliceous breccia capped by a paleo-weathering crust. The second member (Laohuding Subformation; 180 m thick) has a lower part of interbedded basinal clasts and Mn-bearing dolomite with dolomitic limestone; a middle part that is a gigantic stromatolite limestone reef accompanied with basinal-clastic limestone; and a top of dolomitic limestone. The carbonate rock in the formation is mostly tabular-layered and medium- to thick-bedded. The sediments in the stromatolite reef are mostly thick- to very thick-bedded with laminations and cross-bedding. The total thickness is recorded to 333 m.
Relationships and Distribution
Lower contact
The sandstone in the base of the formation is in conformable contact with underlying Hongshuizhuang Fm.
Upper contact
The top is in unconformable contact with the overlying Xiamaling Fm.
Regional extent
Tianjin, Hebei, west Liaoning. Tieling Formation widely distributed in the Yan-Liao (Yanshan-Liaohe) area. In north sector of Yanshan Mountain, it is absent; but in west sector in Xuanhua (190 m) there is obvious depositional break between the first and second members. It is dominated by clastic rock, clastic dolomite and thick-bedded dolomite. In east sector, in Kuancheng (204 m thick) it is stable in lithological character. It is thickening in western Liaoning region; in Harqin Zuoqi (334 m) and Lingyuan (276 m). It is thinning to south direction from Harqin Zuoqi, for example in Chaoyang (13-103 m) where it is stable in lithological character, but the middle and upper stratigraphic horizons are absent, while the middle and lower horizon is commonly Mn-bearing.
GeoJSON
Fossils
The stromatolites are mainly the Chihsienella-Tielingella assemblage. The microplants are Taeniatum crassum, Polyporata obsoleta etc.
Age
Depositional setting
Additional Information
The paleomagnetic polarity when the Tieling Fm deposited was mixed type, and the paleomagnetic pole was at 24°N, 207.5° (by Zhang Huimin et al., 1991).