Ordovician trilobite faunas and depositional history of the Taebaeksan Basin, Korea: implications for palaeogeography

The Taebaeksan Basin occupies the central-eastern part of the Korean penins ula and was a low-relief shallow marine carbonate shelf on which the Cambro -Ordovician Choson Supergroup was deposited. In the Taebaeksan Basin trilob ites are among the most dominant fossil groups in the Lower Ordovician, but they become less important in Middle Ordovician faunal assemblages. The Ea rly Ordovician trilobite faunas of the Taebaeksan Basin are characterised b y the common occurrence of pandemic genera such as Jujuyaspis, Leiostegium, Asaphellus, Protopliomerops, Hystricurus, Apatokephalus, Shumardia, Asapho psoides, and Kayseraspis. Biogeographically significant trilobite taxa incl ude Yosimuraspis, Dikelokephalina, Koraipsis, and Chosenia. These Ordovicia n trilobite faunas, which thrived in shallow marine environments, show a re markable similarity with faunas from North China, implying that the Taebaek san Basin was connected through contiguous shallow waters to North China. T hese Sino-Korean faunas exhibit a close biogeographic connection with Austr alian faunas, with which they share some endemic genera, whereas they are m ore distantly related to the faunas of South China, South America, and Nort h America. Based on these palaeobiogeographical features, it is suggested t hat in the early Palaeozoic much of the present Korean peninsula including the Taebaeksan Basin belonged to the Sino-Korean block, while part of the p eninsula was derived from the Yangtze block.