Middle Permian radiolarians from Anmenkou, Chaohu, Northeastern Yangtze platform, China

Abstract

The biostratigraphy of the Middle Permian Gufeng Formation in the northeastern Yangtze platform is examined based on radiolarians. This study is concentrated on the Anmenkou section in the Chaohu area of Anhui Province, China. The Gufeng Formation is divided into the Phosphate Nodule‐bearing Mudstone Member (PNMM) and the Siliceous Rock Member (SRM) in ascending order. The former primarily consists of mudstone including abundant phosphate nodules, and the latter consists mainly of alternating beds of chert, siliceous mudstone and mudstone, with intercalations of porous chert. Ammonoids in the mudstone of the lower PNMM are Wordian. Chert, siliceous mudstone and mudstone of the SRM include abundant radiolarians with sponge spicule assemblages suggestive of the Wordian–Capitanian. Albaillellaria are predominant in the lower SRM, while Entactinaria and Spumellaria are predominant in the middle and upper SRM. These radiolarians correspond to three radiolarian assemblage zones: Pseudoalbaillella longtanensis–Pseudoalbaillella fusiformis, Follicucullus monacanthus, and Follicucullus scholasticus–Ruzhencevispongus uralicus. The assemblage of radiolarians and sponge spicule fauna suggests a depositional depth of 150–500 m. The radiolarian fauna of the Gufeng Formation is considered to be representative of the relatively shallow, tropical radiolarian fauna of the Middle Permian eastern Paleotethys.

Taxonomic significance of short forms of middle Permian Pseudoalbaillella Holdsworth and Jones, 1980 (Follicucullidae, Radiolaria)

“…The first appearance (FA) of the short forms of P. internata and P. monacantha coincides with the FA of their respective species. Additionally, in previous studies, P. fusiformis co-occurred with its short form; P. monacantha co-occurred with its short form (e.g., Ishiga et al, 1982Ishiga et al, , 1986Kametaka et al, 2009;Ito et al, 2013a). These similarities in shape, size, and occurrence suggest that the specimens of the short forms are the upper half of their respective species.…”

“…Occurrence: This species is reported from Japan (e.g., Ishiga and Imoto, 1980;Ishiga et al, 1982), South China (e.g., Kametaka et al, 2009;Wang and Yang, 2011), the United States (Holdsworth and Jones, 1980;Blome and Reed, 1992), and Thailand (Sashida et al, 1993).…”

“…Occurrence: This species has been reported from Japan (e.g., Ishiga et al, 1982), South China (e.g., Sheng and Wang, 1985;Kametaka et al, 2009), and the United States (e.g., Holdsworth and Jones, 1980). Range: Late Cisuralian (Early Permian) to Guadalupian (Middle Permian).…”

“…Range: Late Cisuralian (Early Permian) to Guadalupian (Middle Permian). Pseudoalbaillella fusiformis is a characteristic species of the P. globosa Assemblage Zone in Southwest Japan (Ishiga, 1986) and a diagnostic species of the P. longtanensis-P. fusiformis Assemblage Zone in South China (Kametaka et al, 2009;Wang et al, 2012) Range Zone in Southwest Japan (Ishiga, 1986(Ishiga, , 1990 and from the Albaillella xiaodongensis to F. monacanthus zones in South China (Wang et al, 1994). Kuwahara and Yao (1998) found P. fusiformis from the Neoalbaillella grypa to N. optima zones (Lopingian: Upper Permian) in Southwest Japan.…”

“…As a result of morphological analysis of these radiolarians, we confirmed the short forms of P. fusiformis, P. internata, and P. monacantha. Pseudoalbaillella fusiformis and P. monacantha are characteristic or diagnostic species of middle Permian radiolarian zones (e.g., Ishiga, 1990;Kametaka et al, 2009). However, the short forms of each species occur abundantly in most horizons of the Gujingling section.…”