Niubao Fm
Type Locality and Naming
The reference section is located near Niubao in the Lunpola basin 100 km northwest of Baingoin County, Tibet. Named by the Qinghai Petroleum Party in 1958.
Lithology and Thickness
A sequence of deep-water lacustrine mudstone and shale, belonging to a petroleum-bearing association of fine to coarse clastic rocks and carbonate rocks. The base is brownish red conglomerate and sandy conglomerate, with rare fossils. The middle and upper parts consist dominantly of gray and grayish green mudstone-shale, with marlstone and oil shale and locally tuff. The lithology and thickness change greatly laterally. The strata in the Lunpola and Baingoin basins are thickest, being up to 3000 m. In the basin center the rocks are fine in grain size and bear oil and gas and locally oil shale. The thickness ranges from 20 to 3000 m.
Relationships and Distribution
Lower contact
The base has an unconformable contact with the underlying Cretaceous Jingzhushan Fm (Cret. Column 7a) or Abushan Fm (Cret. Column 6a near Tibet-Qinghai border).
Upper contact
The base has a disconformable contact with the overlying Oligocene Dingqinghu Fm.
Regional extent
The Niubao Formation comprises the lower part of the Longmenka Gr, Chaimasiba Gr and Qilin Fm in the western region and the Songbai Gr and Jue’en Gr (Jueen Gr) in the eastern part.
GeoJSON
Fossils
The middle and upper parts yields sporopollen and the charophytes Obtusochara, Sphaerochara and Tectochara and the ostracod Cypris-Limnocythere assemblage.
Age
Depositional setting
Additional Information