Shamuluo Fm
Type Locality and Naming
It was named by the Regional Geological Survey Party under the Geological Bureau of Tibet in 1987. The naming section is located at Shamuluo south of the Salt Lake region of Geji County, Tibet (E 82°25′, N 32°18′).
Synonym: （沙木罗组）
Lithology and Thickness
Lower part is composed of grey-white medium-bedded and medium-grained quartz-sandstones and grey-brown pebble-bearing gritstones intercalated with calcareous shale. Upper part is composed of grey-white medium-, and thin-bedded quartz-sandstones, intercalated with dark-grey thin-bedded bioclastic limestones. Its visible thickness is of over 340 m.
Relationships and Distribution
Lower contact
No base of it has been found. . "it has been found that the Upper Jurassic to Lower Cretaceous Shamuluo Fm rests with angular unconformity on the Muggar Kangri Gr (= Muggarakangri Gr)" [from New results and major progress in regional geological survey of the Baingoin County Sheet, Chen Guorong et al., https://en.cnki.com.cn/Article_en/CJFDTotal-ZQYD2004Z1020.htm]. Regionally, the schematic strat column had also indicated the next older unit as Cuoguo Fm.
Upper contact
Its top part consisting of grey-white medium-, and thin-bedded quartz-sandstone and siltstone and being in a disconformable contact with the grey-white medium-bedded quartz-sandstone intercalated with thin-bedded marl and bioclastic limestone from the basal part of the overlying Cretaceous System.
Regional extent
The formation is distributed extensively in the areas of Shamuluo and Gangre of the Salt Lake region, Geji County and Wuma of Gaize County. In the Shamuluo and Gangre areas the formation represents largely clastic rocks, while in the Wuma area it represents essentially carbonates. In most areas the formation is lack of its top and basal parts, yet in the Wuma area the top part of the formation is in an unconformable contact with the overlying Triassic System, with a thickness of 340-450 m.
GeoJSON
Fossils
In the Salt Lake region, it yields ammonites fossils as represented by Perisphinctidae; coral fossils such as Heliocoenia cf. oribignyi, H. meriani, Epistreptophyllum sp., Latiastrea sp. and Stylina sp.; and bivalve fossils such as Ostrea sp. and Buchia sp. In the Gangre region it yields abundant coral fossils such as Thamnasteria sp., Dermoseris delogadoi, Thecosmilia magna, Stylina lobata, Calamophyllia sp., Stylosmilia sp. and Dimorphastrea sp.
Age
Depositional setting
Additional Information