Yishijilik Fm
Type Locality and Naming
The type section is located on Yishijilik Mountain, north of Tekes County, Xinjiang. It was named by Tan Hongbing et al. in 1976.
Lithology and Thickness
Volcanics and Volcaniclastics. Composed of gray-purple, purple-red and gray-green intermediate and acid eruptive rocks at Awulale Mt. and the south slope of Boluohuoluo Mt. in a NW-SE trend. In the representative Tuomasubei section, it is dominated by purple, purple-red and brick-red very fine-grained acidic volcanic rocks, rhyolite porphyry, amygdaloidal pyroxene-andesitic porphyrite, andesitic dacite porphyry, basalt porphyrite and andesitic pebbly lithic tuff, as well as purple crystal-lithic tuff and other tuffs, with tuffaceous fine- to coarse-grained sandstones and tuffaceous conglomerate in the lower part. Exposed thickness 1529.5 m.
In the middle Tuergong River of Awulale Mt., the thickness increases, reaching 9536 m, and the amygdaloidal peridotite-basalt porphyrite increases, with more basic lava in the upper part and more acid lava in the lower part. At Naogaigou of Yining County on the south slope of Boluohuoluo Mt., it is composed of gray-purple rhyolitic breccia tuff, rhyolitic welded tuff and minor rhyolitic porphyry. Neither top nor bottom is completely exposed, with an exposed thickness of 1881.2 m.
Relationships and Distribution
Lower contact
Unconformable contact with the underlying Akeshak Fm at the type section. Unconformable or disconformable contact with the underlying Halajunshan Fm at exposures in middle Tuergong River of Awulale Mt.
Upper contact
Unconformable contact with the overlying Tiemulik Fm at exposures in middle Tuergong River of Awulale Mt. The top is unseen at the type section;
Regional extent
Distributed at Yishijilik Mountain of Tekes County in a NW-SE trend, the formation varies greatly in thickness and lithology, with few interbeds of normal clastic rock and limestone.
GeoJSON
Fossils
No fossils are found
Age
Depositional setting
It is interpreted as a
Additional Information