Wanlong Fm

Southeast Jilin. The Wanlong Fm was named by the Jinan (S. Jilin) Party of Regional Geological Survey, Changchun College of Geology in 1960, which was first quoted by Yu Jianzhang (C. C. Yu) et al. (1964). The type section is located at Wanlong Village, Iron factory 20 km east of Tonghua City, Jilin Province. The reference section is located at Qinggouzi, Badao River, Hunjiang City (Baishan City), Jilin Province.

Synonym: （万隆组）

The Wanlong Fm consists of a suite of dark carbonate rocks and clastic carbonate rocks and algal reef limestone. Lower member is dark gray medium-thick-bedded and thin-bedded limestone with micrite veins and dolomitic limestone with “finger marks algae” and light color thin-bedded silty limestone. Middle member is dark gray compact massive limestone, shale and silty marl. Upper member consists of yellowish gray calcareous shale, silty marl and dolomitic limestone, dolomite and algae limestone. A micrite-veined limestone that is well developed in the lower part of the formation is of wide distribution and is a stable marker horizon for strata classification and correlation of the Wanlong Formation in this region. Qiao Xiufu et al. (1994) consider that those micrite veins are the records of paleo-earthquakes, suggesting that the seismic vibration caused liquidification in unconsolidated sediments. Some small-scale cross-bedding, ripple-bedding and desiccation cracks are also found in the formation. It is 546-711 m thick.

Abundant microplants have been found in the shale interbeds, such as: Trachysphaeridium sp., Leiopsophosphaera sp., Nucellosphaeridium sp., Pseudo- zonosphaera sinica, Laminarites cf. antiquissimus, Taeniatum cf. simplex etc.