The latest Permian calcareous algae of the Changxingian from the lower Yangtze region, East China, and the establishment of a new algal province: the Pyrulites Province.

Abstract

Although the latest Permian calcareous algae are widespread and well documented in Soth China, there have been only scattered records from East China. Here we reported a latest Permian calcareous algal flora from the Changxing Formation of the lower Yangtze region, East China. The flora was collected from two sections in southern Jiangsu (Wuxi and Suzhou) and two sections in northwest Zhejing (Huzhou and Changxing). The algal flora comprises five genera and 8 species, including a new species, all assignable to Gymnocodiaceae (Gymnocodium bellerophontis, G. exile, G. sp., Permocalculus fragilis, P.tellenus and Pyrulites sinicus) and Dasycladales (Macroporella changxingensis sp. nov., Mizzia sp.). Two common microproblematica genera Pseudovermiporella and Tubiphytes are also identified here. The algal flora shows close Tethyan affinities and is comparable in general terms to other Late Permian algal floras known from the Tethys Realm and particularly it is similar to the eastern Tethyan floras From South China, which is characterized by the dominance, both in species diversity and in abundance of Gymnocodiaceae algae. Compared to the calcareous algal flora of Middle Permian age the Changxingian flora shows low divcersity and none of species continue over the PermianTriassic boundary.The discovery of calcareous algae from the Changxing Formation at Meishan section, Changxing, northwestern Zhejian is particularly interesting since this section is the global stratotype section for the Changxingian Stage and for the Permian Triassic boundary (GSSP) (Yin, 1996). The Changxing Formation at this locality is composed of shallow marine carbonates with carbonate tempesties and turbidites representing an intra shelf slope and basin facies with anoxia/dysaerobic environment conditions. Although the algal assemblage is similar in general aspects to the assemblages of the Huzhou, Wuxi and Suzhou sections to the east and northeast, these three sections represent shallow platform/reef limestone facies. Further, the fossil algae from the Meishan section are usually fragmentary and few in number indicating allochthonous preservation and it is believed that most of the fossils were transported from east and northeast. It is interesting to note that a well known Permian microproblematica genus, Pseudovermiporella, was discovered both from Meishan section and from Xishan section,Suzhou .There is no consensus regarding the systematic affinity of this fossil. It has been established as a dasyclad alga by Elliott (1958) and referred by Korde 1965 to red algae. The other authors suggested that Pseudovermiporella is a benthic attached foraminifera (Henbest, 1963; Vachard, 1980, etc.). The abundant occurrence of the genus in the carbonate sequence of the Meishan section, which is deposited in a sedimentary environment unfavourable for shallow marine calcareous algae may support a foraminiferal affinity of Psudovermiporella. The discovery of the distinctive genus Pyrulites Mu in the lower Yangtze region is of interest both stratigraphycally and palaeobiogeographically. This genus was established as a subgenus of Permocalculus on the bases of Permocalculus (Pyrulites) sinicus Mu (1981)