Norian (late Triassic) Foraminifera from the Baoshan Block, Yunnan Province (China) and their response to palaeoenvironmental changes

During the Norian (Late Triassic), foraminifera became more globally widespread and achieved greater diversity than at any other time in the Triassic. We studied Norian foraminiferal assemblages and their responses to palaeoenvironmental changes in the Potou section of the Baoshan Block, Yunnan Province, China. A total of 37 taxa are identified. The dominant genera are Aulotortus, Miliolipora, Galeanella, Parvalamella, Decapoalina and Triasina. Two Norian (Sevatian age) foraminiferal biozones are recognized at Potou, namely the Aulosina oberhauseri Zone and the Triasina hantkeni Zone. Ten foraminiferal morphogroups (B, C, D, E, F, G, H, I, J and K) are categorized based on their chamber growth characteristics and inferred lifestyles. Morphogroups in the lower part of the Potou section (Aulosina oberhauseri Zone) are dominated by morphogroup I (Decapoalina, Galeanella, Miliolipora, Milioliporidae, Ophthalmidium and Paraophthalmidium) whilst in the upper part of the section (Triasina hantkeni Zone), there was a gradual increase in the abundance of morphogroup H taxa (Aulosina, Aulotortus, Lamelliconus, Parvalamella, Prorakusia and Triasina). Microfacies at the Potou section belong to inner to middle carbonate platform environments and show a gradual up-section increase in the abundance of bioclastic components, such as dasycladaceans and sponges.