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Longtan Formation
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Longtan Fm base reconstruction

Longtan Fm


Period: 
Permian

Age Interval: 
P3 (74-76, 83-85, 90), Wuchiapingian (early Lopingian Epoch, early Late Permian)


Province: 
Anhui, Hunan, Zhejiang, Jiangsu, Guizhou, Sichuan

Type Locality and Naming

The type section is located in the Longtan County in the eastern suburb of Nanjing City, and the reference section is situated in the Tianbao Mt. of Dunhua Region, Jiangning County 20 km to the southeast of Nanjing City. It was named by Ding Wenjiang (Ting V.K.) in 1919.

Synonym:

Lungtan Fm


Lithology and Thickness

It is divisible in ascending order into three members: The Sandstone Member, which is composed mainly of light-grey medium- and coarse-grained feldspar-and quartz-sandstones, with a thickness of 20-40 m. Coal-bearing Member, which is composed largely of coarse-grained feldspar-quartz-sandstone, fine-grained sandstone, siltstone and oolitic bauxitic siltstone, intercalated with coal seams and carbonaceous shale containing 3-5 coal layers, with a thickness of 35-40 m, yielding abundant Gigantopterides flora. Limestone Member, which is composed mainly of dark-grey and grey-black thick-bedded and cherty nodule-bearing limestones, intercalated occasionally with shale, yielding abundant brachiopod fauna, as well as Fusulinida and conodonts, etc., with a thickness of 1.5-2.5 m.


Lithology Pattern: 
Coal


Relationships and Distribution

Lower contact

Conformable contact with the sandy shale or siltstone on the top of the underlying Yanqiao Fm,

Upper contact

Conformable contact with the black shale and siliceous shale of the overlying Dalong Fm. But in portions of South China, there is an intervening Talung Fm that spans the Changhsingian interval.

Regional extent

Distributed in the southern and southeastern parts of Hunan Province, the southern part of Anhui Province, the southern part of Jiangsu Province, and the northern part of Zhejiang Province. The typical stratigraphic sequence for the Longtan Fm described above occurs in the southern and eastern parts of Jiangsu Province and in the southern part of Anhui Province. In the southern part of Hubei Province the thickness of the Longtan Fm is only of several meters, and being composed largely of siltstone. In the southeastern part of Hubei Province the formation is composed mainly of fine-grained sandstone and siltstone, intercalated with two coal layers, with a thickness of 40-70 m. The Limestone Member is otherwise known as the Xiayao Fm. Eastward to the southwestern part of Jiangsu Province and the northern part of Zhejiang Province, the thickness of the Sandstone Member of the Longtan Fm reaches as much as of 40-70 m; with the Coal-bearing Member being intercalated with 2-3 layers of sandy limestones and 6-10 layers of coal; the Limestone Member is composed of sandy limestone and ammonoid-bearing sandy siltstone and pure siltstone, with a thickness of 40-80 m. Its top part represents the Upper Coal-bearing Member, which is composed of fine-grained sandstone, siltstone and siltstone, intercalated with coal seams, with a thickness of 40-70 m.


GeoJSON

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Fossils

The lower member yields Plant fossils (phytolites) represented by the Gigantopteris-Lobatannularia assemblage; the middle member yields Brachiopods represented by the Spinomarginifera lopingensis-Squamularia indica assemblage, and Fusulinida such as Codonofusiella sp., etc., belonging to the early stage of the Late Permian Epoch


Age 

Wuchiapingian (early Lopingian Epoch, early Late Permian)

Age Span: 

    Beginning stage: 
Wuchiapingian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
259.55

    Ending stage: 
Changhsingian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
251.90

Depositional setting

It is interpreted as delta-facies coal-bearing deposits.


Depositional pattern:  


Additional Information


Compiler:  

Jin Yugan, Hu Shizhong

GeoJSON estimate by Can Cai and Xinyi Zhang (Chengdu Univ. Tech. students)