Etoucun Fm
Type Locality and Naming
The type section is located at 500 east of Etoucun village (25°11′03″N—110°15′50″E), about 3.5 km south of Wayaokou of Guilin City, Guangxi. Along the No. G321 Highway from Guilin to Yangsuo, in the midway near Ertang Town there is a cement road westward, which leds to an abandoned quarry in a hill foot where the Etoucun Limestone outcrops. The reference section is near Huilong Village at No. 220 milestone of province road S202 from Guilin to Yangsuo (along east bank of Lijiang River), about 36 km SSE of Guilin (25°00'29.29"N, 110°30'49.13"E). It was named by Yin Bao’an et al. in 1978.
[Figure - Topographical map of the southern suburb of Guilin City, Guangxi showing the type localities of the Tangjiawan Fm (A), Guilin Fm (B), Dongcun Fm (C) and Etoucun Fm (D).]
Lithology and Thickness
Limestone. This formation is a set of gray to dark-gray medium- to thick-bedded bioclastic limestone and stromatoporoid-bearing limestone, , intercalated with few
thin-bedded laminated limestone and oncolite.. It is 64 m in thickness.
[Figure - Overviews of the Etoucun Formation in the type locality (left) and the lowest part of the Formation in a small cultivated land of reference section (right), being rich in rugose corals of the Eocaninophyllum yizhangense Zone.]
Relationships and Distribution
Lower contact
The formation is conformable contact with the underlying Dongcun Fm and the boundary is clear based on the color changes of weathered surface from white to dark.
[Figure - The lower boundary of Etoucun Formation (right, dark gray in color) is easily recognized in the field by its darker color with the underlying Dongcun Fm (left, bright white in color).]
Upper contact
The formation is disconformably overlain by the Shangyueshan Member of Yaoyunling Fm of the possible early Carboniferous, which is characterized by the banded limestone. Commonly, there is a thin bed of red weathered crust characterized by enrichment of iron oxide minerals with karstification in the topmost Etoucun Formation, below which all cosmopolitan stromatoporoids, quasiendothyrid foraminifers and cyrtospiriferid brachiopods as well as endemic cystophrentidae rugose corals disappeared. This extinction is most likely with Hangenberg Event equivalent..
[Figure The topmost layer of the Etoucun Formation separated by an erosional paleokarst surface from overlying Yaoyunling Fm in the Huilong section of S202 roadside, Guilin.]
Regional extent
It is distributed in northern and northeastern Guangxi along the southern margin of Jiangnan Old Land.
GeoJSON
Fossils
This formation yields abundant Stromatopora Stromatocerium sp. Actinostroma sp., Plantiferostroma sp., and Trupetrostroma sp.; Foraminifera Quasiendothyra c. communis, Q. regularis, Q. kobeitusana and Q. konensis; and Coral Cystophrentis kolaohoense.
Age
Depositional setting
The lithology and fossils indicate a carbonate platform environment representing a new transgression in the uppermost Famennian
Additional Information