Huaqiao Fm

Lithology and Thickness:

The Huaqiao Formation is a carbonate sequence. It consists of dark grey and greyish black, thin-bedded striped argillaceous limestone, laminated argillaceous limestone with limestone lenses, micritic limestone and dolomitic limestone, intercalated with thin- to thick-bedded limestone breccia. The argillaceous limestone at the top is usually weathered into brownish yellow shale. The Huaqiao Formation represents deposits of slope facies.

[Figure: Dominated rocks of the Huaqiao Fm, all from Wa’ergang section, Taoyuan, northwestern Hunan Province, South China. A, B, thin-bedded striped argillaceous limestone，B is in weathered status; C, D, laminated argillaceous limestone with limestone lenses.]

Lithology-pattern: Clayey limestone

Relationships and Distribution:

Lower contact:

The Huaqiao Fm is in conformable contact with the underlying Aoxi Fm. The lower boundary of the formation is marked by lithological change from dolomite of the Aoxu Fm to argillaceous limestone of Huaqiao Fm.

Upper contact:

The Huaqiao Fm is in conformable contact with the overlying either Shenjiawan Fm or Loushankuan Fm. The upper boundary is defined by the appearance of light grey or greyish white, median-bedded crystalline limestone at the base of Shenjiawan Fm, or lithological change from argillaceous limestone to dolomite of the Loushankuan Fm.

Regional extent:

The Huaqiao Formation is exposed in the Jiangnan Slope Area of South China Region, distributed mainly in northwestern and western Hunan (Niuchehe, Tangjiaxi, and We’ergang of Taoyuan County; Tianping of Dayong County; Aoxi of Baojing County; Chatian and Jiudiantang of Fenghuang County) and eastern Guizhou (Dadongna of Tongren City, Yangping of Zhenyuan County).

GeoJSON:

Fossils:

The Huaqiao Formation is richly fossiliferous with trilobites (polymerids and agnostoids), conodonts, and brachiopods (Peng, 1987, 1992; Peng and Chen, 1983, Peng et al., 2004a, b; Engelbretsen and Peng, 2007; Percival et al., 2016; Dong and Zhang, 2017). 14 agnostoid zones and its parallel 10 polymerid zones, and 7 conodont zones are recognized (Peng, 1987, 1992; Peng et al., 1995, 2004a, b; Peng and Robison, 2000). They are too many taxa to be listed in details in these zones. Here only the zone’s names of South China, with one zone recognized in western Zhejiang Province, are listed, in ascending order, the agnostoid zone are: 1, Ptychagnostus atavus Zone; 2, Ptychagnostus punctuosus Zone; 3, Goniagnostus nathorsti Zone; 4, Lejopyge armata Zone; 5, Lejopyge laevigata Zone; 6, Proagnostus bulbus Zone; 7, Linguagnostus reconditus Zone; 8, Glyptagnostus stolidotus Zone; 9, Glyptagnostus reticulatus Zone; 10, Agnostus inexpectans Zone; 11, Tomagnostella orientalis Zone (this agnostoid zone is absent in Huaqiao Fm of northwestern Hunan); 12, Agnostotes orientalis Zone; 13, Rhaptagnosus ciliensis Zone; and 14, Eolotagnostus decorus Zone; and the parallel polymeroid zones are: 1, Dorypyge richthofeni Zone; 2, Pianaspis sinensis Zone; 3, Wanshania wanshanensis Zone; 4, Liostracina bella Zone; 5, Chaungia subquadrangulata Zone; 6, Proceratopyge protracta Zone; 7, Corynexochus plumula Zone; 8, Irvingella angustilimbata Zone; 9, Kaolishaniella-Ochonotellus cf. kuruktagensis Zone; Probinacunaspis nasalis-Peichiashania hunanensis Zone; the conodont zones are: 1, Gapparodus bisulcatus-Westergaardodina brevidens Zone; 2, Shandongodus priscus-Hunanognathus tricuspidatus Zone; 3, Westergaardodina quadrata Zone; 4, Westergaardodina matsushitai-W. grandidens Zone; 5, Westergaardodina lui-W. ani Zone; 6, Westergaardodina cf. calix- Prooneotodus rotundatus Zone; and 7, Proconodontus tenuiserratus Zone.

[Figure 1: Agnostoids served as zonal fossils of biostratigraphy of South China, arranged in ascending succession from left to right and from top to bottom. Except for T, U, all are from the Huaqiao Formation of northwestern Hunan Province (A‒I, K, L from Wangcun, Yongshun County; J, M‒S from Paibi, Huayuan County; V‒AA from Tangjiaxi, Taoyuan County). T, U are from the Huayanssi Fm, Jiangshan County, western Zhejiang Province. They are figured to show a complete agnostoid biostratigraphy of South China in the interval of Huaqiao Formation. A, B, Ptychagnostus atavus (Brøgger, 1878), cephalon and pygidium; C, D; Ptychagnostus punctuosus (Angelin, 1851), cephalon and pygidium; E, F, Goniagnostus nathorsti (Brøgger, 1878), cephalon and pygidium; G, Lejopyge armata (Linnarsson, 1869), exoskeleton, cephalon and pygidium; H, Lejopyge laevigata (Dalman, 1828), exoskeleton; I, J, Proagnostus bulbus Butts, 1926, cephalon and pygidium; K, L, Linguagnostus reconditus Poletaeva and Romanenko, 1970, cranidium and pygidium; M, N, Glyptagnostus stolidotus Öpik, 1961, cephalon and pygidium; O−Q, Glyptagnostus reticulatus (Angelin, 1951), cephalon, pygidium and exoskeleton; R, S, Agnostus inexpectans Kobayashi, 1938, cephalon and pygidium; T, U, Tomagnostella orientalis (Lazarenko, 1966), cephalon and pygidium (the T. orientalis Zone is absent in northwestern Hunan, for which it is substituted by an equivalent polymerid zone, the Corynexochus plumula Zone); V, W, Agnostotes orientalis (Kobayashi, 1935), cephalon and pygidium; X, Y, Rhaptagnosus ciliensis Peng, 1992, cephalon and pygidium; Z, AA, Eolotagnostus decorus Peng, 1992, cephalon and pygidium. All scale bars = 1 mm. See also for zonal fossils for Shenjiawan Fm.]

[Figure 2: Polymerids served as zonal fossils of biostratigraphy South China, arranged in ascending succession, from left to right and from top to bottom. Polymerid zonation of Huaqiao Formation is parallel to the agnostoid zonation of the formation. All are from the Huaqiao Formation of northwestern Hunan Province (A, C‒E, G‒L from Paibi, Huayuan County; B, F from Wangcun, Yongshun County; J‒K, R‒V, from Wa’ergang, Taoyuan County; M‒O from Tangjiaxi, Taoyuan County). A, B, Dorypyge richthofeni Dames, 1883, cranidium and pygidium; C, D; Pianaspis sinensis (Yang in Zhou et al., 1977), cranidium and pygidium; E, Wanshania wanshanensis Rong and Yang, in Zhou et al., 1977), exoskeleton with missing librigenae; F, G, Liostracina bella Lin and Zhou in Lin et al., 1983, cranidium and pygidium; H, I, Chaungia subquadrangulata Sun, 1935, cranidium and pygidium; J, Proceratopyge protracta Peng, 1992, cranidium; K, L, Corynexochus plumula Whitehouse, 1939, cranidium and two pygidia (the Corynexochus plumula Zone is an equivalent of the Tomagnostella orientalis Zone of western Zhejiang); M, N, Irvingella angustilimbata Kobayashi, 1938, cranidium, cranidium; O, Kaolishaniella sp.; P, Q, Ochonotellus cf. kuruktagensis (Zhang, 1981), cranidium and cranidium; R, S, Probinacunaspis nasalis Peng, 1992, cranidium and pygidium; T‒V, Peichiashania hunanensis Peng, 1992, pygidium, cranidium and cranidium. Scale bars = 1 mm for F, G, K, L; 2 mm for A−E, H−J, M, N, T‒V; 6 mm for R; 15 mm for S.]

Age:

Wangcunian through early and middle Jiangshanian (early late-Cambrian); variable among regions

Age span:

Beginning stage: Drumian

Fraction up in beginning stage: 0.0

Beginning date (Ma):

Ending stage: Jiangshanian

Fraction up in ending stage: 0.5

Ending date (Ma):

Depositional setting:

Depositional-pattern:

Additional Information

Huang Weipei in a 1990 manuscript and Zhang (1997) realized the Huaqiao Formation (in narrow sense) and the overlying Chefu Fm are uniform in lithology. These two formations, and the overlying Bitiao Fm as well, were erected by Hunan Regional Geological Team (1964), on the basis of paleontologic rather than lithologic content. These three formations were published in the same article and the Huaqiao Formation holds page priority. Huang in 1990 and Zhang (1997) correctly lumped the Huaqiao Fm and Chefu Fm together but apparently ignored the page priority of the Huaqiao Formation, which was named and described prior to the Chefu Fm, and prior to the Bitiao Fm as well, which shares also same lithology with two underlying formations. Therefore, Peng and Robison (2000, p. 3) proposed the reassignment the Chefu and Bitiao strata to an expanded Huaqiao Formation and suppression of the formation names Chefu and Bitiao. As a result, the Huaqiao Formation here embraces the strata assigned to the Huaqiao, the Chefu and the Bitiao formations by the Hunan Regional Geological Survey Team (1965).