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Journal of Tropical Oceanography

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Calcium Carbonate Composition of Surface Sediments and Influencing Factors in the 90°E Ridge of the Northeast Indian Ocean

DU Shuhuan1, XIAND Rong2, SU Xiang1, ZHANG Lanlan1, PAN Zirui1,3, XIE Jinwo4, LUO Chuanxiu1, WAN Sui1   

  1. 1. Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guang zhou 510301, China;

    2. State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;

    3. University of Chinese Academy of Sciences, Beijing 100049, China;

    4. School of Geography and Remote Sensing, Guangzhou University, Guangzhou 510006, China


  • Received:2025-01-01 Revised:2025-03-07
  • Supported by:

    Hainan Provincial Joint Project of Sanya Yazhou Bay Science and Technology City (2021JJLH0048); the Guangdong Basic and Applied Basic Research Foundation (2023A1515010705, 2023A1515011955)；Independent Integration Program, South China Sea Institute of Oceanography, Chinese Academy of Sciences (SCSIO2023HC07); National Natural Science Foundation of China (42176082)

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Abstract: By studying the calcium carbonate composition and spatial distribution of surface sediments from the 90°E ridge and its adjacent waters in the northeast Indian Ocean, not only clarity the main sources of calcium carbonate in sediments from different water depths, but also reveal the influenced factors and variation mechanism of the calcium carbonate content of surface sediments in the northeast Indian Ocean. Based on the whole-sample calcium carbonate and its particle size calcium carbonate tests of 10 surface sediment samples, combined with the scanning electron microscope microscopic characteristics and quantitative statistical data, found that the calcium carbonate content of the Ridge Area varies between 36.95% -74.76%, with an average content of 56.05%, which can be classified into three grades of 30%-45%, 45%-60%, and 60%-75%, and that the influencing factors for the regional distribution of calcium carbonate have a diversity of factors. At stations with water depths above 3000 m, calcium carbonate mainly comes from foraminiferal shells with particle sizes >150 μm; in areas with water depths close to or exceeding the dissolution surface of calcium carbonate, calcium carbonate mainly comes from fine-grained fractions with particle sizes <25 μm; microscopic characterization of the 25-38 μm fractions and the statistical results show that, in addition to calcareous ultramafic fossils and fragments of foraminiferal shells in the surficial sediment, different genera of calcium carbonate were also identified for the first time, the proportion of calcareous organisms in the surface sediments reached 73.68%. In addition, the variation of calcium carbonate content in the ridge area is closely related to the dilution of land-based materials and siliciclastic shells. The method of statistical analysis of particle size calcium carbonate combined with scanning electron microscope microscopic features established in this study, not only provides a new method for revealing the mechanism of calcium carbonate changes in deep-sea sediments, but also deepens the understanding of the composition of buried and dissolved organic carbon in the ocean, providing a scientific basis for the study of the global ocean carbon cycle.

Key words: 90°E Ridge, surface sediments, calcium carbonate composition, particle size calcium carbonate