Aletonggou Fm
Type Locality and Naming
Kuruktag region. The Aletonggou Fm was named by E. Norin in 1937. The typical section is located at Tiementuoluogai northwest of Tiemintuo- Luogaitala. The reference section is in Zhaobi Mountain in middle Kuruktag and south of Ushitala of Heshuo County, Xinjiang Weiwuerzhu Zizhiqu (Xinjiang Uygur Autonomous Region). Lower-middle formation of the Kuruktag Gr (3 of 9).
Synonym: （阿勒通沟组）
Lithology and Thickness
The Aletonggou Fm is dominated by gray, greenish gray and minor reddish-brown medium- to fine-grained sandstone, siltstone, silty slate and laminated slate. It is obviously characterized by bearing different sized gravels (dropstones) in the fine-clastic rock, and the sandstone bearing unstable glacial intercalations (diamictite, with tens to over 100 m thick single layers) and lenticular or thin-bedded limestone. The sandstone has ripple marks and oblique beddings. The thickness is generally about 580 to 1500 m and is thicker in middle area and thinner east and westwards, and is up to 2017 m in Astanbulak.
Locally, the upper part generally contains intermediate-acidic, acidic (minor basic) volcanic rock and tuff. In the west area, intercalations of volcanic rock are increasing (especially in the upper part). In the middle area, the volcanic rock is decreasing, and in the clastic rock the dropstones are common and the strata are generally intercalated with thick-bedded massive glacial conglomerate (diamictite, with thickness 20 to 130 m). In the east area, the volcanic rock is not common and the tuffaceous sandstone intercalations are common.
[Figure: Stratigraphic Column of the Kuruktag Gr]
Relationships and Distribution
Lower contact
At the bottom there is often a layer of glaciogenic rock (diamictite), which rests disconformably or locally unconformably on the Zhaobishan Fm
Upper contact
Unconformably underlies the Teruiaiken Fm tillite. However, in some locations according to the stratigraphic column, there is an intervening Huangyanggou Fm of interglacial limestone unless scoured away.
Regional extent
Kuruktag region. With a wide distribution, this formation is exposed in West Kuruktag (Kalatiekenwula, Xishankou), going eastward to the south of Heshuo County and east of Weili County, to middle Kuruktag area (Zhaobishan, Xinggertag) and Kesitanbulak north of Xingdi and eastward to east Kuruktag (Yulegunbulak); in addition, it is also exposed in Yardang Mountain on the south.
GeoJSON
Fossils
The fine clastic rock yields abundant microplants including Trachysphaeridium cultum, T. hyalinum, Pseudozonosphaera asperella, Asperatopsophosphaera bavlensesis, A. umishanensis etc.
Age
Depositional setting
Additional Information
Some geologists consider the Teruiaiken Formation, together with underlying Aletonggou Formation, as the product of the same ice age, with only different environments and resulting different lithologies. However, some geologists oppose such a glacial origin, and consider it to be gravity flow deposits.