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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
Author(s) -
Li Qian,
Azmy Karem,
Yang Shuai,
Xu ShengLin,
Yang Di,
Zhang XiHua,
Chen AnQing,
Chen HongDe
Publication year - 2021
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.4010
Subject(s) - geology , permian , isotopes of strontium , radiogenic nuclide , strontium , supercontinent , isotopes of carbon , paleontology , radiometric dating , stratigraphy , geochemistry , isotope , tectonics , mantle (geology) , structural basin , craton , physics , nuclear physics , quantum mechanics
The radiogenic strontium isotope ( 87 Sr/ 86 Sr) 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 87 Sr/ 86 Sr values decrease consistently upward from 0.70833 to 0.70684, and their trend correlates well with a long‐term increase in the carbon isotope (δ 13 C) values. The negative correlation between the 87 Sr/ 86 Sr and δ 13 C 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 87 Sr/ 86 Sr values. The rate of upward decrease in 87 Sr/ 86 Sr 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 δ 13 C values of the Luduba profile peaks at ~5‰, which correlates with the distinct lowest 87 Sr/ 86 Sr value (~0.70684) near the top of the Maokou Formation (Upper Capitanian). The δ 13 C 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, the 87 Sr/ 86 Sr ratios remain low values, probably due to the development of cold climate, increasing input of hydrothermal flux and low terrestrial runoff.