Early–Middle Permian strontium isotope stratigraphy of marine carbonates from the northern marginal areas of South China: Controlling factors and implications,Geological Journal

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Early–Middle Permian strontium isotope stratigraphy of marine carbonates from the northern marginal areas of South China: Controlling factors and implications
Geological Journal ( IF 1.4 ) Pub Date : 2020-10-18 , DOI: 10.1002/gj.4010
Qian Li _{1,

2} , Karem Azmy ₂ , Shuai Yang ₁ , Sheng‐Lin Xu ₁ , Di Yang ₃ , Xi‐Hua Zhang ₄ , An‐Qing Chen ₁ , Hong‐De Chen _{1,

3}

Affiliation

The radiogenic strontium isotope (⁸⁷Sr/⁸⁶Sr) system is a powerful tool for constraining sea‐level change and palaeoclimatic variations as well as tectonic activities. The Permian is a period that records the lowest seawater Sr‐isotopic ratios in the Earth's history. The near‐primary geochemical signatures retained in the micritic carbonates of the Luduba section (uppermost lower to Middle Permian) on the northern margin of the South China Block allowed the reconstruction of reliable carbon and Sr‐isotope profiles for global chemostratigraphic correlations. The investigated interval (~300 m) spans the Chihsia and overlying Maokou formations (Kungurian to Capitanian series). The ⁸⁷Sr/⁸⁶Sr values decrease consistently upward from 0.70833 to 0.70684, and their trend correlates well with a long‐term increase in the carbon isotope (δ¹³C) values. The negative correlation between the ⁸⁷Sr/⁸⁶Sr and δ¹³C values suggests that the sea‐level change, climatic conditions, opening of the Neo‐Tethys Ocean, and accretion of the Pangean Supercontinent are among the factors that might have contributed to the consistent depletion of the ⁸⁷Sr/⁸⁶Sr values. The rate of upward decrease in ⁸⁷Sr/⁸⁶Sr values throughout the Chihsia Formation is generally higher than that of the overlying Maokou Formation, which provides a possible marker for intra‐ and interbasinal basin stratigraphic correlations. The general increase in the δ¹³C values of the Luduba profile peaks at ~5‰, which correlates with the distinct lowest ⁸⁷Sr/⁸⁶Sr value (~0.70684) near the top of the Maokou Formation (Upper Capitanian). The δ¹³C values decrease to 3.6‰ at the top of the Maokou Formation, that correlates with the rapid sea‐level drop in the Late Guadaualupian worldwide. Meanwhile, the⁸⁷Sr/⁸⁶Sr ratios remain low values, probably due to the development of cold climate, increasing input of hydrothermal flux and low terrestrial runoff.

更新日期：2020-10-18

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