Climate changes posed profound influences on the historical evolution of terrestrial biological and ecological systems. Although sedimentary records such as plant fossils, coal, and evaporites can qualitatively indicate climate fluctuations, quantifying the aridity and humidity degrees and changes in Earth's historical climate remains challenging. As a unique and compact landmass, the South China Block not only preserves abundant ancient marine sedimentary records but also documents the tectonic-climate-ecology co-evolution over hundreds of millions of years.
In this study, we report high contents (2.4 ± 3.8 mg N kg-1) and 17O anomalies (11.0 ± 7.4 ‰) of nitrate (NO3-) in the early Cambrian black shale from South China, likely caused by atmospheric NO3- intrusion under dry climates that followed tectonic uplift. By developing new methods to quantify aridity indices (AI, 0.06 ± 0.08) in combination with observational data with paleoclimate models, we reconstructed the historical AI variations. Our analyses revealed three significant dry-to-humid transitions which include Cambrian-Ordovician to Silurian-Permian, Permian-Triassic boundary to middle Triassic-early Jurassic, and Jurassic-Paleogene to Neogene (Figure 1).
Figure 1 Phanerozoic climate history of South China
This work provides new and unique constraints on Phanerozoic dry-humid degrees and alternations in South China, which are useful for understanding Earth's climate dynamics and their interaction with biological and geological events such as mass extinctions, the evolution of terrestrial plants, and shifts in the global biogeochemical cycles. The paper was published in Geophysical Research Letters, an AGU journal, on October 26, 2024. The first author is Fan Wei-Guo, a 2020 Ph.D. student from Tianjin University, with contributions from Professor Zhou Mingzhong of Guizhou Normal University, Professor Hu Yongyun of Peking University, Professor Shen Yanan of the University of Science and Technology of China, and Professors Liu Xue-Yan, Song Wei, and Liu Cong-Qiang from Tianjin University. This study was supported by the National Natural Science Foundation of China (42125301 (Liu Xue-Yan), 42330505 (Liu Xue-Yan), and 42488201 (Hu Yongyun)).
Article information: Wei-Guo Fan, Xue-Yan Liu*, Mingzhong Zhou, Wei Song, Yongyun Hu, Yanan Shen, Cong-Qiang Liu. (2024) Sedimentary 17O-nitrate evidence for Phanerozoic aridity and humidity oscillations in South China. Geophysical Research Letters, 51, e2024GL111475. https://doi.org/10.1029/2024gl111475.
