Early Rhuddanian (Llandovery, Silurian) graptolites from Shiqian, northeastern Guizhou Province, South China

 

Authors: Saparin MA, Wang H-Q, Jeon J-W, Wu X-J, Chen Q, Zhang Y-D

Article in press: Received 14 April 2025; Accepted in revised form 27 August 2025; Online 30 November 2025

Keywords: : graptolite, biostratigraphy, Silurian, Rhuddanian, Shiqian, Guizhou, China,

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Abstract

A possible stratigraphical unconformity spanning the Ordovician-Silurian transition has been proposed in the Upper Yangtze Region, South China, explained as likely to have been caused by a global sea-level drop. However, the temporal and spatial extent of the hiatus in the region and whether it was alternatively caused or enhanced by the contemporary Kwangsian Orogeny that affected the entirety of South China is debated. Here we present a graptolite fauna of early Rhuddanian age from Shiqian, northern Guizhou Province, to address this issue and discuss its implications. Graptolite species identified are Normalograptus angustus (Perner), Normalograptus anjiensis (Yang), Normalograptus cf. jideliensis (Koren’ & Mikhaylova), Normalograptus cf. larini Koren’ & Melchin, Normalograptus mirnyensis (Obut & Sobolevskaya), Hirsutograptus sinitzini (Chaletzkaya), Akidograptus ascensus Davies, Avitograptus avitus (Davies), Parakidograptus cf. acuminatus (Nicholson), Korenograptus cf. laciniosus (Churkin & Carter), Metabolograptus parvulus (Lapworth), and Paraclimacograptus cf. innotatus (Nicholson). The graptolite assemblage indicates the upper part of the Akidograptus ascensus Biozone for the lowermost ’Lungmachi Formation’ in the Tunping and Ganlusi sections in Shiqian, northern Guizhou Province. It thus implies that only a minor hiatus occurs between the topmost Ordovician and the lowermost Silurian in the Shiqian area.