Wulabo Fm

The type section is located in the Jingjingzi Trench to the southeast of Urumqi (Urumchi). It was named by the No. 672 Party under the Xinjiang Petroleum Administration in 1957, and was cited publicly by the Compiling Group for the Regional Stratigraphic Chart of the Xinjiang Uygur Autonomous Region in 1981.

Sandstone. It is characterized by a stable lithology and a complex composition of sandstone, comprising rock debris, feldspar and quartz, etc. Lower part is composed of interbeds of grey-green and grey thick-bedded medium-grained feldspar-rich sandstone and medium-bedded siltstone, intercalated with many layers of siliceous rocks and limestone, yielding plant fossil stems, with a thickness of about 750 m. Upper part is composed of interbeds of yellow-green and grey-green medium- and thin-bedded sandstone, siltstone and siltstone, and is possessed cross-bedding, ripple marks and mud cracks, with a thickness of about 500 m. Total thickness of 1000-1400 m.

Among the spore-pollen fossils in the formation it is the bivesiculate pollen that predominates and belongs to the Hamiapollenites- Striatoabietites-Striatoparvisaccites assemblage. The formation yields also bivalves such as Palaeanodonta pseudolaongissima, etc., and Estheria fossils.

It is interpreted as a delta facies.

The average value of the Sr/Ba ratio of the siltstone contained is of 0.37. So it should belong to a delta facies deposit by inference.