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Special Session 2: Changing ocean environment: from the sedimentary perspective -- processes and records |
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Paleoenvironmental evolution since 45ka BP based on sedimentary pollen records of 12I712 core in the Northeastern Indian Ocean
SS2-16-S
Weiming Jiang* , South China Sea Institute of Oceanology, Chinese Academy of Sciences
Chuanxiu Luo, South China Sea Institute of Oceanology, Chinese Academy of Sciences
Presenter Email: 467858590@qq.com
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| Based on sporo-pollen assemblage characteristics and AMS 14C dating results of 12I712core in the Indian Ocean, the authors determined four pollen assemblages from A to D from bottom to top by using Tilia software. The following conclusions can be found in the analysis of the 4 zones: A zone, about 45 ~42ka BP: fern (45.32%), tree pollen (32.61%), herb (only22.08%), pollen concentration (632grains/g). In this zone, the Castanopsis and Evergreen Quercus have a high pollen percentage, which reflects the climate at that time was relatively warm. There is a large amount of pollen of the Chenopodiaceae and Poaceae in this zone, indicating that the climate was relatively dry. During this period, the pollen resource of 12I712 core was probably the south of Sri Lanka. B zone, about 42 ~ 36ka BP: fern (49.37), herb (26.14%), tree pollen (only24.48%), pollen concentration (964grains/g). In this zone, the Castanopsis and Evergreen Quercus also have a high pollen percentage, which reflects the climate at that time was relatively warm. There is a large amount of pollen of the Chenopodiaceae and Poaceae in this zone, indicating that the climate was also relatively dry. During this period, the pollen resource of 12I712 core was probably the south of Sri Lanka. C zone, 36 ~ 26ka BP: fern (53.75%), herb (28.10%), tree pollen (only18.15%), pollen concentration was very low (73grains/g). In this zone, the Castanopsis and Evergreen Quercus have a low pollen percentage. And, the pollen percentage of Alnus and Betula is gradually increasing. Combined with low pollen concentration, there reflects the climate at that time was turning cold during this period. And the pollen resource of 12I712 core was probably the south of Sri Lanka and Eurasia. The number of pollen of the Chenopodiaceae and Poaceae in this zone was gradually decreasing, indicating that the climate was gradually turning wet. D zone, 26 ~ 5ka BP: fern (50%), herb (31.58%), tree pollen (only18.42%), with a lowest pollen concentration (22grains/g). In this zone, the Castanopsis and Evergreen Quercus have a lowest pollen percentage, which reflects the climate at that time was cold. The pollen number of the Chenopodiaceae and Poaceae in this zone was gradually decreasing, indicating that the climate was gradually wet. About 18ka BP, the pollen number of Chenopodiaceae, Caryophyllaceae, Euphorbiaceae, Alnus and Pinus reached the maximum, which reflects the climate at that time was coldest. And this moment coincides with the Last Glacial Maximum. |
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