Wuxiahe Fm

It was proposed by Xiang Liwen, Lin Baoyu and Nan Yunshan in 1960 and published in Atlas of Qinling Paleontology in 1963. The type section is located in Wujiahe section, Xiaozhenxiang Township, Mingzhuba District, Langao County, Shaanxi Province. The reference section is at the Bajiaokou section in Ziyang County, Shaanxi Province. (See Additional Information)

Synonym: (吴家河组); 五峡河组; Wujiahe Fm; Wafangdian Fm; Anpingliang Fm

It consists of gray, black-gray thin-bedded siliceous siltstone, siliceous carbonaceous slate interbedded with thick-medium bedded sandstone and silty slate (Figures). The top is unclear, and the base is marked by the disappear of the medium-thick bedded sandstone and /or limestone. It is over 663.3 m in thickness at the type section.

[Figure 1. The lithology of the Wuxiahe Fm at Bajiaokou section (east bank of Renhe River) (Photography by Wang)]

It yields graptolite and brachiopods, etc. The following graptolite zones, the Cyrtograptus sakmaricus zone, C. insectus zone, C. centrifugus zone, C. murchisoni zone and Monograptus riccartonensis zone can be recognized in this formation.

[Figure 2. The typical graptolite fauna in Wuxiahe Fm at the Bajiaokou section, Ziyang, Shaanxi Province (by Wang Jian)]

Synonym: (吴家河组); 五峡河组; Wujiahe Fm; Wafangdian Fm; Anpingliang Fm

Lithology and Thickness:

It consists of gray, black-gray thin-bedded siliceous siltstone, siliceous carbonaceous slate interbedded with thick-medium bedded sandstone and silty slate (Figures). The top is unclear, and the base is marked by the disappear of the medium-thick bedded sandstone and /or limestone. It is over 663.3 m in thickness at the type section.

[Figure 1. The lithology of the Wuxiahe Fm at Bajiaokou section (east bank of Renhe River) (Photography by Wang)]

Lithology-pattern: Clayey sandstone

Relationships and Distribution:

Lower contact:

The Wuxiahe Fm is conformably on the Doushangou Fm or the Baiyaya Fm

Upper contact:

The Wuxiahe Fm is unconformably overlain by the Quaternary.

Regional extent:

It is a band of outcrops from northwest to southeast in the Bajiaokou, Gaoqiao, Banjiuguan of Ziyang Xian and Maixijie, Guanyuan of Langao Xian. The thickness is over 155m at the south of the Gaoqiao-Baxianjie fault, 500-1251m at north of the fault.

GeoJSON:

Fossils:

It yields graptolite and brachiopods, etc. The following graptolite zones, the Cyrtograptus sakmaricus zone, C. insectus zone, C. centrifugus zone, C. murchisoni zone and Monograptus riccartonensis zone can be recognized in this formation.

[Figure 2. The typical graptolite fauna in Wuxiahe Fm at the Bajiaokou section, Ziyang, Shaanxi Province (by Wang Jian)]

Age:

Age span:

Beginning stage: Sheinwoodian

Fraction up in beginning stage: 0.5

Beginning date (Ma):

Ending stage: Pridoli

Fraction up in ending stage: 1

Ending date (Ma):

Depositional setting:

Depositional-pattern:

Additional Information

Fu (1963) established Xianzhonggou Fm, which included the Wuxiahe Fm and the top of Xianzhonggou Fm. The Stratigraphic Chart Compiling Group of Shaanxi Province (1983) revised the name to Wujiahe Fm because the administrative district changed its name to Wujiahe. Ge et Li (1984) established Anpingliang Fm for the upper part of the Wuxiahe Fm and restricted the Wuxiahe Fm to represent the succession of Oktavites spriralis bearing strata, which includes the lower part of the original Wuxiahe Fm and the upper part of the Doushangou Fm. Fu (1986) proposed Wafangdian Fm to represent the late (?) Silurian succession in Wafangdian area, Ziyang Xian. Luo (1992) considered the Anpingliang Fm as the junior synonym of the Wuxiahe Fm since they share the same lithology, lithofacies and metamorphic grade. Ma Runhua (ed.) abandoned the Anpingliang Fm, Xianzhonggou Fm and Wujiahe Fm and resumed the original Wuxiahe Fm in 1998. We accepted the idea and take the Bajiaokou section as the type section and the Songshugou section as the reference section.