Terrestrial paleoenvironment characterization across the Permian–Triassic boundary in South China. (February 2015)

• Record Type: Journal Article
• Authors: Bercovici, Antoine; Cui, Ying; Forel, Marie-Béatrice; Yu, Jianxin; Vajda, Vivi
• Is Part Of: Journal of Asian earth sciences. Volume 98(2015)
• Page Start: 225
• Page End: 246
• Publication Date: 2015-02
• Subjects: Permian–Triassic boundary -- Palynology -- Biostratigraphy -- Mass-extinction -- Fungal spike; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2014.11.016
• Languages: English
• ISSNs: 1367-9120

Abstract

Graphical abstract: Highlights: We analyzed four terrestrial PTB sections in Guizhou and Yunnan, South China. The PTB is associated to paleoenvironment change from lacustrine to brackish lagoon. Taphonomic change might add bias on observed extinction patterns across PTB. Paleobotanical and radiometric age are indicating PTB near the top of Xuanwei Fm. Identification of Reduviasporonites below the PTB mark end-Permian fungal spike event. Abstract: Well-preserved marine fossils in carbonate rocks permit detailed studies of the end-Permian extinction event in the marine realm. However, the rarity of fossils in terrestrial depositional environments makes it more challenging to attain a satisfactory degree of resolution to describe the biotic turnover on land. Here we present new sedimentological, paleontological and geochemical (X-ray fluorescence) analysis from the study of four terrestrial sections (Chahe, Zhejue, Mide and Jiucaichong) in Western Guizhou and Eastern Yunnan (Yangtze Platform, South China) to evaluate paleoenvironmental changes through the Permian–Triassic transition. Our results show major differences in the depositional environments between the Permian Xuanwei and the Triassic Kayitou formations with a change from fluvial–lacustrine to coastal marine settings. This change is associated with a drastic modification of the preservation mode of the fossil plants, from large compressions to small comminuted debris. Plant fossils spanning the Permian–Triassic boundary show the existence of two distinct assemblages: In the Xuanwei Formation, a Late Permian (Changhsingian) assemblage with characteristic Cathaysian wetland plants (mainly Gigantopteris dictyophylloides, Gigantonoclea guizhouensis, G . nicotianaefolia, G . plumosa, G . hallei, Lobatannularia heinanensis, L . cathaysiana, L . multifolia, Annularia pingloensis, A . shirakii, Paracalamites stenocostatus, Cordaites sp.) is identified. In the lowermost Kayitou Formation, an Early Triassic (Induan) Annalepis–Peltaspermum assemblage is shown, associated with very rare, relictual gigantopterids. Palynological samples are poor, and low yield samples show assemblages almost exclusively represented by spores. A ∼1 m thick zone enriched in putative fungal spores was identified near the top of the Xuanwei Formation, including diverse multicellular forms, such as Reduviasporonites sp. This interval likely corresponds to the PTB "fungal spike" conventionally associated with land denudation and ecosystem collapse. While the floral turnover is evident, further studies based on plant diversity would be required in order to assess contribution linked to the end-Permian mass extinction versus local paleoenvironmental changes associated with the transition between the Xuanwei and Kayitou formations.