近～1 Ma帕里西维拉海盆沉积物的粒度分布以及亚洲风尘沉积对东亚冬季风的响应

    Grain size distribution of the Parece Vela Basin sediments and the response of Asian dust deposition to the East Asian winter monsoon over the past ～1 million years

      摘要
    • 摘要: 帕里西维拉海盆（PVB）的风尘主要来源于亚洲大陆干旱地区，风尘粒度与风尘通量（质量堆积速率MAR）是指示东亚季风强度和源区干旱化程度的重要指标。本文通过Weibull函数拟合方法对帕里西维拉海盆内样品的碎屑组分进行了定量分离，结合Sr、Nd同位素特征，分析了不同组分的来源，重建了帕里西维拉海盆在过去近1 Ma期间的风尘MAR。结果表明，CP-19岩芯中细粒组分粒径范围是0.1～12.6 μm，平均众数粒径约1.9 μm，平均含量约50.0 %。推测该组分主要来源于亚洲东部沙漠和黄土高原区域的亚洲风尘，风尘MAR介于22.6～91.5 mg·cm−2·ka−1（平均62.8 mg·cm−2·ka−1）；粗粒组分粒径范围为1.3～58.5 μm，平均众数粒径约13.2 μm，其平均含量约44.2 %，推测主要来自近源的西马里亚纳沟海脊的火山物质，火山物质MAR介于27.3～167.9 mg·cm−2·ka−1（平均60.5 mg·cm−2·ka−1）。在近1 Ma期间，帕里西维拉海盆内的风尘MAR增加反映了东亚风尘源区整体持续干旱的气候特征。1～0.6 Ma期间，海盆内与太平洋之间的风尘MAR变化趋势的差异主要受到增强的东亚冬季风影响；从0.6 Ma开始至今，气候变化周期清晰明确，海盆内和太平洋区域的风尘MAR变化趋势同步，共同反映了冰期阶段东亚地区的冬季风增强、干旱化加剧，并在最近的一个冰期有所减弱的气候特征。

       

      Abstract: Asian dust within the Parece Vela Basin (PVB) mainly originates from the arid regions of Asia, and dust particle size and dust flux (MAR mass accumulation rate) play a very important role in indicating the strength of the East Asian winter monsoon and the degree of aridification of the source region. In this study, we quantitatively separated the detrital fractions of samples within the PVB by the Weibull function fitting method, analyzed the sources of different fractions in combination with the Sr and Nd isotopic signatures of the sediments, and reconstructed the dust MAR within the PVB during the past 1 Ma. Findings indicate that the fine-grained fraction of core CP-19 varies in grain size from 0.1 to 12.6 μm, averaging around 1.9 μm in modal grain size and about 50.0% in content. It is inferred that this fraction is Asian dust, mainly originating from the deserts of eastern Asia and the Chinese loess plateau region, with a dust MAR ranging from 22.6 to 91.5 mg·cm−2·ka−1 (average 62.8 mg·cm−2·ka−1). The coarse-grained fraction of core CP-19 varies in grain size from 1.3 to 58.5 μm, averaging around 13.2 μm in modal grain size and about 44.2% in content. This fraction is inferred to be proximal volcanic material, mainly sourced from the nearby west Mariana ridge, with a volcanic material MAR ranging from 27.3 to 167.9 mg·cm−2·kyr−1 (average 60.5 mg·cm−2·ka−1) The increase in dust MAR within the PVB during the near 1 Ma period reflects the overall persistent arid climatic characteristics of the East Asian dust source region. During the period from 1 to 0.6 Ma, the dust MAR trends within the PVB and between the Pacific Ocean show that the differences are influenced by the enhanced East Asian winter monsoon. From 0.6 Ma to the present, the climate change cycle is clearly defined, and the dust MAR trends in the PVB and the Pacific Ocean are synchronized, which together reflect the climatic features of enhanced winter monsoon and intensified aridification in East Asia during the ice age phase as well as the weakening of the winter monsoon intensity and aridification in the last ice age.

       

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