| The understanding of global climatic laws and mechanisms since Quaternary can help toforecast the coming climate. Eolian component in marine sediments provides the paleoclimaticinformation of source area and plays a significant role in the research of global climate andenvironment. In this paper, grain size, radiogenic strontium (Sr) and neodymium (Nd) isotopecompositions together with eolian fluxs were analyzed on the detrital fraction of core PV090102sediment from the Parece Vela Basin. The conclusion that sediment in Parece Vela Basin isderived mainly from Asian continent was drawn by the grain-size and isotopic data, furthermore,the past changes of Asian eolian input to the basin over the last2Ma and the paleoclimaticevolution history of Asian continent since2Ma were discussed based on the eolian fluxs data.Grain-size analysis on the detrital fraction of core PV090102shows that the grain size rangefrom0.5to32μm (mean grain size=3.2μm), and the grain size distribution appears to be bimodalcharacteristics and negative skewness. Weibull distribution function is used to fit the grain-sizedistributions of each sample, and two different end-member components are separated from eachsmaple. The fine-grained fraction shows a distinct size mode at about2μm in the range of narrowdistribution (mainly0.5~16μm),which coincident with the eolian dust of the North Pacific. Weargue that this fraction is derived mainly from Asian dust and is the major component (60~90%)of the detrital sediment. The coarse fraction are characterized by a wider size range (about1.6~32μm)，and aflatter size distribution, and with a size mode at about10μm. Thecoarse fractions aremainly derived from the ridges and islands around Parece Vela Basin.The detrital fraction of core PV090102have a wide87Sr/86Sr ratio (0.709555~0.713356)and narrow143Nd/144Nd ratio (εNd(0)=-6.8~-9.1), The data are consistent with a two end-membermixing between volcanic materials from ridges and islands around Parece Vela Basin and eolian dust from the Asian continent, Theradiogenic Sr isotope composition of the <2μm、2~10μm and>10μm fraction shows that the <2μm fraction have a higher average87Sr/86Sr(0.713084~0.715481), which coincident with the eolian dust of the North Pacific. The>10μmfraction was characterized by lower87Sr/86Sr (0.705892~0.708128), which is similar to thevolcanic materials from ridges and islands around Parece Vela Basin.2~10μm fraction has a87Sr/86Sr between eolian and volcanic materials, and mainly near eolian member. These resultsfurther prove that the fine fraction is derived mainly from Asian dust. Using the the radiogenic Srisotope binary mixing model, we have calculated the content of eolian component. The resultfurther firmly shows that Asian eolian is the major component (63.0~92.3%) of the detritalsediment.This paper evaluated the eolian flux of core PV090102with the eolian content data obtainedby gain size and Sr、Nd isotope compositions. Based on eolian flux, we identified three stages ofenhanced aridity in the As ian continent and the strengthened atmospheric circulation forced by theincrease of global ice volume and the uplift of Tibetan Plateau over the last2Ma, i.e.1.95~1.2Ma、1.2~0.5Ma and0.5Ma~now. The eolian flux fluctuate significantly during1.2~0.5Ma, whichrespond to the mid-Pleistocene transition (MPT) in Quaternary. Moreover, the different sizefraction of core PV090102response well to the enhanced aridity in the As ian continent and thestrengthened atmospheric circulation over the last2Ma, as w ell as the strengthened volcanicactivity of the western Pacific since the last0.5Ma. The eolian component of core PV090102offers the potentials to reconstruct the climatic evolution of eastern Asia and the volcanic historyof west Pacific since Quaternary. |
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