Duodigou Fm
Type Locality and Naming
It was named by Chen Yirui as the “Duodigou Limestone” in 1961. The naming section is located in the Duodigou Gully on the northern side of Lhasa City, Tibet.
Synonym: （多底沟组）
Lithology and Thickness
Lower part is composed of grey medium-bedded limestone, argillaceous limestone and marl, with its base representing grey medium-bedded limestone, intercalated occasionally with marls. Upper part consists of grey medium-, and thin-bedded alternating layers of algal limestone with grey calcareous shales. Its thickness is over 600 m.
Relationships and Distribution
Lower contact
The basal part of the formation is in a conformable contact with the underlying Quesangwenquan Fm at Quesang consisting of an alternating layer of sandstone and shale.
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Linbuzong Fm
Regional extent
The formation is distributed in the area of Lhasa, and is characterized by a consistent lithology and varying degrees of metamorphism when the rocks are approaching to the granite massif. Its thickness varies a bit greatly, being of over 600 m to the north of Lhasa City; of over 1000 m at the Yeba Gully in Dazi County, where the Duodigou Fm overlies the Yeba Fm of the Upper Triassic [Not in Triassic lexicon entries[.
GeoJSON
Fossils
In the area of Lhasa, the formation yields foraminifera as represented by Pseudocyclammina ex. gr. lituun, P. maynci (?), Salpingoporella cf. johnsoni, S. annulata, Sarfatiella dubari, Cladocoropsis memoria-naumanni, Cl. kotoi var. tosaensis and etc., and corals as represented by the late Jurassic elements such as Lochmaesmila radiata and etc.
Age
Depositional setting
Additional Information