Permian radiolarian faunas from Thailand and their paleogeographic significance

Chert and fine-grained elastic rocks in Thailand contain rich Permian radiolarian faunas. We have discriminated eight radiolarian assemblages in these rocks; Pseudoalbaillella bulbosa (Upper Carboniferous to lowermost Permian; Gzhelian to Asselian), Pseudoalbailtella simplex (lowermost Permian; Asselian), Pseudoalbaillella lomentaria (Lower Permian; Asselian to Sakmarian), Pseudoalbaillella scalprata (Lower Permian; Sakmarian), Follicucullus monacanthus (Middle Permian; Wordian), Follicucullus porrectus (upper Middle to lowermost Upper Permian; Capitanian to lower Wuchiapingian), Neoalbaillella ornithoformis (Upper Permian; Wuchiapingian), and Neoalbaillella optima (Upper Permian; Changsingian) assemblages in stratigraphic order. These radiolarians have a potential to contribute to understanding the history of the Paleotethys. Based on the radiolarian biostratigraphy and lithological characteristics, Lower to lower Upper Permian radiolarian-bearing cherts are thought to have been deposited in a pelagic environment in a deep basin far from land. The uppermost Permian radiolarian-bearing cherts, however, reveal differences in their depositional environments. In northern Thailand the uppermost Permian to Middle Triassic radiolarian chert was deposited in a pelagic basin, while in eastern Thailand the uppermost Permian chert and the conformably overlying elastic rocks show a change in depositional environment across the P-T boundary, from a deep pelagic or hemipelagic, to shallow seas in the Triassic. (C) 2002 Elsevier Science Ltd. All rights reserved.