Age constraints of the Hungshihyen Formation (Early to Middle Ordovician) on the western margin of the Yangtze Platform,South China: New insights from chitinozoans |
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Affiliation: | 1. CAS Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China;2. Department of Geology, Tallinn University of Technology, Tallinn 19086, Estonia;3. Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, China;4. State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China;5. CNRS, University of Lille, UMR 8198 Evo-Eco-Paléo, Cité Scientifique, Lille 59000, France;6. Admission of Graduate Student of University of Science and Technology of China, Hefei 230026, China |
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Abstract: | The Hungshihyen Formation represents the Lower to Middle Ordovician near-shore siliciclastic deposits on the western margin of the Yangtze Platform, South China. However, its age is still debated, largely because of insufficient studies. Here we documented the Bursachitina maotaiensis–B. qianbeiensis chitinozoan assemblage from the lower part of the Hungshihyen Formation at Songliang, Qiaojia County, eastern Yunnan Province. This assemblage is remarkably similar to an assemblage that roughly correlates to the middle part of the Corymobograptus deflexus graptolite Biozone in northern Guizhou Province, indicating that the Hungshihyen Formation at Songliang is probably of late Floian age and may extend into the early Dapingian. Additionally, a revision on the chitinozoans previously documented from the strata assigned to the same formation in the Wuding area was made according to the latest classification. The revision allows the recognition of the Euconochitina symmetrica–Eremochitina brevis assemblage, and therefore suggests a late Tremadocian age for this interval based on regional and global chitinozoan biostratigraphic correlations. Considering also its lithologic succession, we argue that the chitinozoan-bearing strata in the Wuding area previously assigned to the Hungshihyen Formation correspond most likely to the uppermost part of the underlying Tangchi Formation or the lowermost part of the Hungshihyen Formation. The base of the Hungshihyen Formation appears therefore to be diachronous in eastern Yunnan Province. |
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Keywords: | Chitinozoa Floian Ordovician Hungshihyen Formation eastern Yunnan South China |
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