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Journal of Paleontology

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ARTINSKIAN CONODONTS FROM THE DINGJIAZHAI FORMATION OF THE BAOSHAN BLOCK, WEST YUNNAN, SOUTHWEST CHINA

¹ Department of Earth System Science, Fukuoka University, Fukuoka 814-0180, Japan, katsumi{at}fukuoka-u.ac.jp
² Shimano 1054-1, Ichihara, Chiba 290-0034, Japan, onuzim{at}kc4.so-net.ne.jp
³ Nanjing Institute of Geology and Palaeontology, Chinese Academy of Science, 39 East Beijing Road, Nanjing 210008, People's Republic of China, xdwang{at}nigpas.ac.cn
⁴ Department of Geology and Geophysics, China University of Geosciences, 29 Xue-Yuan Road, Beijing, 100083, People's Republic of China, meisl{at}cugb.edu.cn

Permian conodonts were recovered for the first time from the Dingjiazhai Formation, a well-known diamictite-bearing stratigraphic unit in the Gondwana-derived Baoshan Block in West Yunnan, Southwest China. The conodont fauna occurs in limestone units within the upper part of the formation and consists of Sweetognathus bucaramangus (Rabe), S. whitei (Rhodes), Mesogondolella bisselli (Clark and Behnken), and an unidentified ramiform element. Based on the known stratigraphic distribution of S. bucaramangus (Rabe), the fauna is referable to the upper Sweetognathus whitei-Mesogondolella bisselli Zone, and thus is dated as middle Artinskian according to the current definition of the stage. The Dingjiazhai Formation is overlain paraconformably by the Woniusi Formation, which is represented mostly by basalts and basaltic volcaniclastics related to rifting volcanism during the separation of the Baoshan Block from Gondwanaland. The present discovery of conodonts from the upper part of the Dingjiazhai Formation reveals that the glaciogene diamictites in the Dingjiazhai Formation are older than middle Artinskian, and the inception of rifting volcanism of the Baoshan Block is later than middle Artinskian.

Occurrence of an essentially warm water element, Sweetognathus bucaramangus (Rabe), in the Dingjiazhai conodont assemblage notwithstanding, the entire fossil faunas including brachiopods and fusulinoideans from the limestone units of the formation can be best interpreted as a middle latitudinal, non-tropical, and still substantially Gondwana-influenced assemblage developed at the northern margin of Gondwanaland just after deglaciation in the southern hemisphere during Early Permian time. This time could be regarded as the beginning of the Cimmerian Region, which had mixed or transitional paleobiogeographic characteristics between the Paleo-equatorial Tethyan and cool/cold Gondwanan realms, and which became well developed during Middle Permian time.

This article has been cited by other articles:

				S. YUKUN, J. XIAOCHI, H. HAO, and Y. XIANGNING PERMIAN FUSULINIDS FROM THE TENGCHONG BLOCK, WESTERN YUNNAN, CHINA Journal of Paleontology, January 1, 2008; 82(1): 118 - 127. [Abstract] [Full Text] [PDF]