Qiangmulequ Fm
Type Locality and Naming
It was named by Jiang Zhongti in 1983. The naming section is located along the bank of the Qiangmulequ River near the No. 114 Maintenance Squad of the Qinghai-Tibet Highway, Anduo County, Tibet. Schematic strat column in previous "red Chinese Lexicon" suggests it is the lowest formation in the Yanshiping Gr.
Synonym: （羌姆勒曲组）
Lithology and Thickness
Lower part is composed of grey-green and grey-violet siltstones and poststones (= fine-grained sandstone), intercalated with alternating layers of shales, argillaceous siltstones and silty mudstones. Upper part is composed of alternating layers of grey and grey-black medium-bedded limestones, medium-, and thick-bedded limestones together with medium-, and thin-bedded marls and biotic limestones, being rich in ammonites and bivalve fossils. It is 725.8 m in thickness.
Relationships and Distribution
Lower contact
Its basal part consisting of medium-bedded poststones (= fine-grained sandstone), being in a conformable contact with the top part consisting of grey-green silty shale intercalated with bands of thin-bedded poststones of the underlying Wenquan Fm (J2), corresponding to the Shaqiaomu Fm.
Upper contact
No top part of the formation has been found. Regionally, the schematic strat column indicates the next younger unit as Xueshan Fm (assigned as mid-Cretaceous)
Regional extent
The formation is distributed essentially along the bank of the Qiangmulequ River with a consistent lithology. The strata yielding typical late Jurassic ammonites and bivalve fossils are exposed only in the Qiangmulequ area, the lithological characteristics of which are correlatable with those in the Wenquan area, but not belonging to one and the same sedimentary environment.
GeoJSON
Fossils
It yields ammonites fossils such as Virgatosphinctes sp., Lithacoceras sp., Aulacosphinctoides sp. and Perisphinctes sp.; as well as bivalve fossils as represented by Exogyra cf. sandulina, Chlamys (Radulopecten) cf. fibrosodichotomus, Eopecten cf. tegulatus, Holcothyris cf. subovalis in the Qiangmulequ region.
Age
Depositional setting
Additional Information