Marine strata of Cretaceous age are widely distributed and well exposed in the Gamba area of South Tibet. A pre-requisite for understanding the depositional and palaeoenvironmental processes, which formed these deposits, is a reliable stratigraphic framework. The strata of the Qiangdong section in the Gamba area yielded calcareous nannofossils which provide a powerful tool for establishing a detailed biostratigraphic subdivision. They also allow for a supra-regional correlation, ideally on a global scale.
Recently, an international research team consisting of PhD student HAN Meiling, Prof. LI Gang from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), alongside Prof. Jörg Mutterlose from Ruhr University Bochum, Germany, and Prof. Ulrich Heimhofer from Leibniz University Hannover, Germany, conducted a systematic study on the mid-Cretaceous calcareous nannofossil biostratigraphy of the Qiangdong section in the Gamba area, southern Tibet. This study has been published in the international journal “Cretaceous Research”.
A total of 76 species have been identified in the 159 m thick section, allowing for the recognition of seven bioevents (calcareous nannofossil zones UC0 to UC7) covering the upper Albian–lower Turonian interval. The first occurrences of the calcareous nannofossil marker species Corollithion kennedyi (base UC1a, 100.5 Ma) and Quadrum intermedium (base UC5c, 94.1 Ma) constrain the Albian/Cenomanian and Cenomanian/Turonian boundaries in the Qiangdong section.
The dominance of Watznaueria barnesiae throughout the studied interval suggests that diversity and abundance of the assemblages were clearly driven by diagenesis. Interval 1 (0–11 m) is barren of calcareous nannofossils. Within Interval 2 (12–43 m), the coexistence of Biscutum constans, Zeugrhabdotus spp. and Nannoconus spp. indicates a deep nutricline. Interval 3 (44–122 m) shows a decrease of B. constans, Discorhabdus ignotus and Nannoconus spp. along with an increase in W. barnesiae, suggesting enhanced diagenesis. Interval 4 (123–159 m), dominated by W. barnesiae, indicates a diagenetically highly altered environment with limited species diversity. A significant negative correlation between species diversity and the relative abundance of W. barnesiae further supports the idea that strong diagenetic alteration affected the nannofossil assemblages.
A regional comparison with findings from the Tingri area, about 150 km west of the studied section, enhances the precision of biostratigraphic correlations in South Tibet. In addition, moderate to poor nannofossil preservation suggests a diagenetic influence for both the Tingri and Gamba areas, highlighting the necessity of critically evaluating nannofossil preservation when interpreting nannofossil assemblages for reliable palaeoceanographic reconstructions. The temperature and nutrient indices obtained in this study deviate from those published in past studies. These findings emphasize that preservation and diagenetic influence need to be critically considered when interpreting nannofossil assemblages for palaeoenvironmental reconstructions.
This research was supported by the National Natural Science Foundation of China.
Reference: Han, M., Li, G.*, Heimhofer, U., Mutterlose, J., 2025. Late Albian–early Turonian calcareous nannofossils from southern Tibet—implications for preservation, biostratigraphy and palaeoecology. Cretaceous Research, 171:106101. https://doi.org/10.1016/j.cretres.2025.106101
Figure 1.Structural diagram of the study area and the location of the section
Figure 2. Lithology, CaCO3 content, relative abundances of selected nannofossil taxa, temperature (MTI) and nutrients (MNI) in the Qiangdong section. ACB = Albian/Cenomanian boundary, CTB = Cenomanian/Turonian boundary.
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