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Cambrian and earliest Ordovician fauna and geology of the Sông Đà and adjacent terranes in Việt Nam (Vietnam)

Hughes, Nigel C.; Peng, Shanchi; Harper, David A.T.; Myrow, Paul M.; Phạm, Ngân Kim; Wernette, Shelly J.; Zhu, Xuejian

Authors

Nigel C. Hughes

Shanchi Peng

Paul M. Myrow

Ngân Kim Phạm

Shelly J. Wernette

Xuejian Zhu



Abstract

Later Cambrian and earliest Ordovician trilobites and brachiopods spanning eight horizons from five localities within the Sông Mã, Hàm Rồng and Đông Sơn formations of the Thanh Hóa province of Việt Nam, constrain the age and faunal affinities of rocks within the Sông Đà terrane, one of several suture/fault-bounded units situated between South China to the north and Indochina to the south. ‘Ghost-like’ preservation in dolomite coupled with tectonic deformation leaves many of the fossils poorly preserved, and poor exposure precludes collecting within continuously exposed stratigraphic successions. Cambrian carbonate facies pass conformably into Lower Ordovician carbonate-rich strata that also include minor siliciclastic facies, and the recovered fauna spans several uppermost Cambrian and Lower Ordovician biozones. The fauna is of equatorial Gondwanan affinity, and comparable to that from South China, North China, Sibumasu and Australia. A new species of Miaolingian ‘ptychopariid’ trilobite, Kaotaia xuanensis, is described. Detrital zircon samples from Cambrian–Ordovician rocks of the North Việt Nam and Sông Đà terranes, and from Palaeozoic samples from the Trường Sơn sector of Indochina immediately to the south, contain a predominance of ages spanning the Neoproterozoic period and have a typical equatorial Gondwanan signature. We associate the Cambrian and Tremadocian of the Sông Đà terrane with areas immediately to the north of it, including the North Việt Nam terrane and the southern parts of Yunnan and Guangxi provinces of China.

Citation

Hughes, N. C., Peng, S., Harper, D. A., Myrow, P. M., Phạm, N. K., Wernette, S. J., & Zhu, X. (2022). Cambrian and earliest Ordovician fauna and geology of the Sông Đà and adjacent terranes in Việt Nam (Vietnam). Geological Magazine, 159(1), 55-80. https://doi.org/10.1017/s0016756821000844

Journal Article Type Article
Acceptance Date Jul 19, 2021
Online Publication Date Sep 27, 2021
Publication Date 2022-01
Deposit Date Sep 27, 2021
Journal Geological Magazine
Print ISSN 0016-7568
Electronic ISSN 1469-5081
Publisher Cambridge University Press
Peer Reviewed Peer Reviewed
Volume 159
Issue 1
Pages 55-80
DOI https://doi.org/10.1017/s0016756821000844