Guozigou Fm
Type Locality and Naming
No type section was assigned originally either by the above-mentioned United Team or by Cheng (1979) when they proposed the Guozigou Formation, either informally or formally. An auxiliary section, the Fenggou section, at the Fenggou Valley, south of Kensay Mountain Pass, Huocheng County, Xinjiang Uygur Autonomous Region, was proposed by Cai (1999) as representative section of the formation. The section lies about 52 km northeast of the seat of Huocheng County, Xinjiang Uygur Autonomous Region (81°10’06”E, 44°28’24”N). It is the lower portion of the same type section, shared by the overlying Xin’ertai Formation that was measured by the Joint Team of Regional Geology Survey Team of Xinjiang Uygur Autonomous Region and Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences in 1974. In this section, the Guozigou Formation is about 40 m thick. The Guozigou Formation was first published by Cheng (1979). The name is derived from Guozigou Canyon in Houcheng County, Ili Kazak Autonomous Prefecture, Xinjiang Uygur Autonomous Region. It was originally appeared a 1974 manuscript by the Joint Team of the Institute of Geology, Chinese Academy of Geological Sciences, and the Stratigraphic Brigade of the Second Regional Geological Survey Team of Xinjiang Uygur Autonomous Region.
Synonym: （果子沟组）
Lithology and Thickness
The Guozigou Formation is a carbonate sequence, consisting of grey, thin-bedded limestone and marlstone, intercalated with thick-bedded argillaceous and siliceous, striped limestone.
Relationships and Distribution
Lower contact
The Guozigou Fm is in conformable contact with the underlying Kensay Fm. The lower boundary of the Guozigou Formation is defined by lithologic change from the clastic sandstone of the Kensay Fm to the limestone of the Guozigou Fm
Upper contact
The Guozigou Fm is in conformable contact with the overlying Xin’ertai Fm. The upper boundary is defined by appearance of argillaceous siltstone at the base of the Xin’ertai Fm.
Regional extent
The Guozigou Formation is exposed in the west of Middle Tianshan-Beishan Region, distributed, with little considerable variation in lithology, at Guozigou of Houcheng County, at Kokirqin of Jinghe County, and in the area Mengjikur River. The thickness is slightly variable, about 7 m thick at Kokirqin, 11 m along Mengjikur River, and about 40 m at Guozigou.
GeoJSON
Fossils
In the type section, three trilobite zones are recognized. The lower Agnostotes tianshanicus Zone contains following genera: Agnostotes, Aistagnostus, Charchaqia, Haniwoides, Hedinaspis, Innitagnostus, Pareuloma, Proceratopyge, Proteuloma, Pseudoyuepingia (=Sayramaspis), Rhaptagnostus, Skljarella (=Proaraiopleura), and Yuepingia; the middle Lotagnostus americanus Zone contains following genera: Acrocephalina, Agnostogonus, Charchagia, Hedinaspis, Innitagnostus, Jegorovia, Lotagnostus, Macropyge, Parabolinella, Pareuloma (=Gansucephalina), Skljarella (=Proaraiopleura), Proceratopyge, Proteuloma, Pseudagnostus, Pseudoyuepingia, Rhaptagnostus, Wujiajiania, and Yuepingia; and the upper Bulbolenus Zone contains following genera: Acrocephalina, Agnostogonus, Agnostotes, Atopasaphus, Bulbolenus, Charchaqia, Clavatellus, Diceratopyge, Gouzia, Hedinaspis, Innitagnostus, Lotagnostus, Macropyge, Plicatolina, Proceratopyge, Proteuloma, Pseudoyuepingia, Rhaptagnostus, Richardsonella, and Skljarella (=Proaraiopleura).
Age
Depositional setting
Additional Information