Nanshuba Fm
Type Locality and Naming
The named section is located in Nanshuba, Mengbang District, Zhenkang County, Yunnan Province.
Synonym: Nansoba Fm (spelling)
Lithology and Thickness
It is dominated by clastic rocks interlaced with carbonate rocks. Lower part is grayish yellow shale with a little sandstone. Middle part is light gray medium thick dense relatively pure limestone and dolomitic limestone. Upper part is yellow shale with purple shale. The bottom boundary is marked by the first occurrence of gray-yellow shale, 600 to 1400 m thick
Relationships and Distribution
Lower contact
Conformable contact with the underlying Dashuitang Fm
Upper contact
The contact relationship is unknown. At present, there is no continuous section between the overlying Wandianba Fm and the Nanshuba Fm, and their Upper Triassic fossil features are very similar. Therefore, the Chengdu Institute of Geology and Mineral Resources of the Chinese Academy of Geological Sciences and the Sichuan Regional Geological Survey (1992) believe that the two formations are upper/lower or phase transition relationships, which need to be studied further.
Regional extent
GeoJSON
Fossils
Bivalve producing Burmesia lirata-Costatoria napengensis assemblage; Anatomites sp., Tropites cf. payeri etc.; Conodonts such as Epigondolella postera, E. bidentata, E. abneptis spatulatus, E. multidentata; foraminifera, coral, etc. [But some of these may be from the underlying Dashuitang Fm, because some former authors combined the two formations.]
Age
Depositional setting
"Wu et al. (2020) recognized eight types of microfacies in the Dashuitang and Nanshuba formations including endoclastic breccia limestone. They concluded that the Dashuitang Formation was deposited on a deep slope, and the overlying Nanshuba Formation was a deep-water shelf." (From " Carbon-isotope excursions in the Norian Stage (Upper Triassic) of the Baoshan terrane, South China " submission by Xin Jin et al., 2022.)
Additional Information