近2 Ma帕里西-维拉海盆沉积物中碎屑组分粒度特征及其物源和古气候意义

摘要

对帕里西-维拉海盆 PV090102孔深海沉积物中碎屑组分进行了粒度分析。结果表明,沉积物碎屑组分的平均粒径为3.2μm,粒径总体变化范围在0.5~32μm,粒度频率分布呈双峰负偏态特征。利用Weibull分布函数对粒度数据进行拟合,分离出粗、细两个不同的端元组分。细粒端元的粒径分布范围较窄,大多在0.5~16μm,峰值较高,众数粒径约为2μm,其特征与北太平中部风尘一致,推测主要为来源于亚洲大陆的风尘,它的百分含量在60%~90%,是碎屑组分的主要物质来源。粗粒端元的粒径分布范围较宽,约为1.6~32μm,峰较扁平,粒径的众数在10μm左右,主要是来自于周围海脊和岛弧的火山物质。PV090102孔沉积物碎屑组分中不同粒度组分对近2 Ma以来亚洲大陆干旱和大气环流系统增强有很好的响应,同时还记录了0.5 Ma以来西太平洋火山活动增强。这些研究结果表明西北太平洋沉积物的粒度组成有助于重建第四纪以来东亚大陆干旱和大气环流历史。%Grain-size analysis on the detrital fraction of deep-sea sediments from the Parece Vela Basin shows that the grain size ranges from 0.5 to 32μm (mean grain size=3.2μm), and the grain size distribution appears to be bi-modal characteristics and negative skewness. Weibull distribution function is used to fit the grain-size distributions of each sample, and two different end-member components are separated from each sample. The fine-grained frac-tion shows a distinct size mode at about 2μm in the range of narrow distribution (mainly 0.5~16μm), which coin-cident with the eolian dust of the North Pacific. We argue that this fraction is mainly derived from Asian dust and is the major component (60%~90%) of the detrital sediment. The coarse fraction is characterized by a wider size range (about 1.6~32μm), a flatter size distribution, and a size mode at about 10μm. The coarse fractions are mainly de-rived from the ridges and islands in and around the Parece Vela Basin. The different size fraction of core PV090102 responses well to the enhanced aridity in the Asian continent and the intensified atmospheric circulation over the last 2 Ma, as well as the strengthened volcanic activity of the Western Pacific since the last 0.5 Ma. This study shows that the grain size composition of the detrital sediment in the Western Pacific is helpful to reconstruct the history of Asian aridity and atmospheric circulation since Quaternary.