TAILIEUCHUNG - New discovery of late early ordovician graptolites and discussion on stratigraphic sequence of paleozoic sediments in the Dinh Ca - Trang Xa section, Vo Nhai disctrict, Thai Nguyen province, Northeast Vietnam

In previous studies, they were described as Mo Dong or Than Sa Formations (Middle-Upper Cambrian). The graptolite faunas newly discovered from the Dinh Ca Market - Na Mo - Dong Bo cross section are composed of Expansograptus urbanus (Monsen), Expansograptus abnormis (Hsu), Tetragraptus quadribrachiatus (Hall), T. approximatus Nicholson, T. pacificus Ruedemann, T. decipiens . Hall, Schizograptus sp., belonging to the quadribrachiatus Biozone, indicating Floian Stage or late Early Ordovician. | Vietnam Journal of Earth Sciences, 39(1), 76-86, DOI: Vietnam Academy of Science and Technology Vietnam Journal of Earth Sciences (VAST) New discovery of late early ordovician graptolites and discussion on stratigraphic sequence of paleozoic sediments in the Dinh Ca - Trang Xa Section, Vo Nhai Disctrict, Thai Nguyen Province, Northeast Vietnam Nguyen Huu Hung*, Nguyen Trung Minh, Doan Dinh Hung, Nguyen Ba Hung Vietnam National Museum of Nature, Vietnam Academy of Science and Technology Received 19 July 2016. Accepted 9 February 2017 ABSTRACT Sandstone, quartzitic sandstone rhythmically interbedded with siltstone, calcareous siltstone and cherty shale are largely exposed in the Dinh Ca - Trang Xa area, Vo Nhai District, Thai Nguyen Province, NE Vietnam. In previous studies, they were described as Mo Dong or Than Sa Formations (Middle-Upper Cambrian). The graptolite faunas newly discovered from the Dinh Ca Market - Na Mo - Dong Bo cross section are composed of Expansograptus urbanus (Monsen), Expansograptus abnormis (Hsu), Tetragraptus quadribrachiatus (Hall), T. approximatus Nicholson, T. pacificus Ruedemann, T. decipiens . Hall, Schizograptus sp., belonging to the quadribrachiatus Biozone, indicating Floian Stage or late Early Ordovician. This serves as the basis for age determination and for establishing new lithostratigraphic units termed as the Dinh Ca Formation (O1 dc) and the Ba Nhat Member. The stratigraphic sequence of Paleozoic sediments in the Dinh Ca - Trang Xa area is also discussed in this paper. Keywords: Graptolite faunas, late Early Ordovician, Dinh Ca Formation, Ba Nhat Member, Thai Nguyen, Vietnam. ©2017 Vietnam Academy of Science and Technology 1. Introduction1 The location of graptolite Ordovic fauna collection and study of stratigraphic sequence including Ordovician, Devonian, and Carboniferous-Permian is shown in Figure 1. The area consists of low hilly and mountainous .

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• Vietnam Journal of Earth Sciences
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• Vo Nhai disctrict
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