Early Permian ammonoids from the Kaeng Krachan Group of the Phatthalung-Hat Yai area, southern peninsular Thailand |
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| Authors: | Masayuki Fujikawa Katsumi Ueno Apsorn Sardsud Wirote Saengsrichan Yoshihito Kamata Ken-ichiro Hisada |
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| Institution: | aAkiyoshi-dai Museum of Natural History, Shuho-cho, Mine-gun, Yamaguchi 754-0511, Japan;bDepartment of Earth System Science, Fukuoka University, Fukuoka 814-0180, Japan;cGeological Survey Division, Department of Mineral Resources, Bangkok 10400, Thailand;dDepartment of Earth Sciences, Yamaguchi University, Yamaguchi 753-8512, Japan;eInstitute of Geoscience, University of Tsukuba, Ibaraki 305-8571, Japan |
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| Abstract: | An Early Permian small ammonoid fauna consisting of Neocrimites sp., Agathiceras suessi Gemmellaro, A. girtyi Böse, Agathiceras? sp., and Miklukhoceras sp. was found in nodules of a fine sandstone bed exposed in the Phatthalung-Hat Yai area of southern peninsular Thailand. The ammonoid-bearing bed belongs stratigraphically to the uppermost part of the Kaeng Krachan Group, which is essentially a clastic-dominant, Late Carboniferous (?) to Early Permian stratigraphic unit, widely distributed in western and peninsular Thailand. This ammonoid fauna is considered to be of Bolorian (Kungurian) age and includes Agathiceras girtyi Böse, which is described for the first time from Thailand. The present discovery of Bolorian ammonoids suggests that the uppermost part of the Kaeng Krachan Group is slightly younger than previously considered and around the latest Early Permian. This further implies that the continental margin environment of the Sibumasu Block drastically changed at around Bolorian time from a cool, clastic-dominant shelf condition to a temperate to subtropical, carbonate platform due to rapid northward drift after middle Artinskian rifting. |
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| Keywords: | Ammonoidea Kaeng Krachan Group Peninsular Thailand Permian Ratburi Limestone |
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