The Response Of Eolian Dust In The Amami Sankaku Basin To The Paleoclimate In The East Asian Since Quaternary

Amami Sankaku Basin(ASB)is located in the northwestern of the Philippine Sea,and is adjacent to the Asian Continent-the second largest dust source area in the world.Because of the influence of East Asian winter monsoon(EAWM)and Westerlies,a large amount of Asian dust has deposited in this area since the Quaternary.The input of eolian dust is closely related to the aridity history,as well as the strength and path of the atmospheric circulation(Westerlies and East Asian monsoon)in the dust source area.Therefore,eolian dust can be used to establish the paleoclimate change of the dust source area.However,because of the limitation of samples and research areas,the study on the whole quaternary dust records in orbital timescales is still absent.In this research,Hole U1438,recovered from ASB during the International Ocean Discovery Program(IODP)Expedition 351,is used to establish the Asian dust input history.The orbital scale age model of Hole U1438 is established with astronomical tuning method.Based on this age model,the variation of clay minerals of Hole U1438 is discussed.By comparing with dust records in different latitudes in the Philippine Sea,paleoclimate proxies in Asian interior,and combing with the transport path and mechanism of modern dust in the east coast of China,the response mechanism of eolian dust input in the ASB to the paleoclimate change in Asian continent is investigated.And then,the driving mechanism of eolian dust input in the ASB during the early Pleistocene is addressed.The influence of migration of Westerlies on the eolian dust input in the ASB has also been discussed.The modern atmospheric particles were collected from the coast of Qingdao.It is mainly composed of detrital mineralogy(quartz,feldspar)and clay minerals(Illite,smectite,kaolinite,and chlorite).The triangular plot of smectite-illite-kaolinite,Asian dust storm prediction model and hybrid single particle Lagrangian integrated trajectory model indicate that these particles come from the arid Asian continent and the vicinity of Qingdao.Eolian dust from the arid Asian interior is mainly transported by the Westerlies and EAWM and the particles from the surrounding area are transported by the regional air mass.The redness(a*)of hole U1438 sediments have been varied periodically since the Quaternary.The high Redness values in the glacial correspond to the high ratios of(illite+chlorite)/smectite.Illite and chlorite in Hole U1438 sediment are mainly derived from the Asian continent,and smectite is mainly derived from the weathering and alteration of volcanic materials around ASB.The high ratio of(illite+ chlorite)/smectite indicates more contributions of Asian eolian dust.The redness of Hole U1438 sediment can reflect the variation of Asian dust input in the ASB and can be used to build astronomical time scale.Therefore,the redness was applied to rebuild the Quaternary orbital scale age model of Hole U1438.Based on this age model,three aspects of research have been addressed:(1)The variability of(illite+chlorite)/ smectite ratio is reconstructed,which is compared with deep-sea oxygen isotope and paleoclimate proxies in the Asian continent.The results show that the dust deposit in the ASB responds sensitively to the paleoclimate evolution of East Asia since the Quaternary.Therefore,the change of solar radiation caused by the variation of Earth's orbital parameters forced the increase of Northern Hemisphere Ice Sheets,and driven the enhancement of EAWM,Westerlies and the Asian aridity during the glacial period,and force more Asian dust input in the ASB.(2)The wavelet analysis illustrates that the redness of Hole U1438 sediment recorded not only the Mid-Pleistocene transition but also the obvious 100 kyr period in the early Pleistocene.The comparison of sedimentary records in different latitude with redness in Hole U1438 illustrate that the redness corresponds to the sedimentary record in the tropics ocean for the 100 kyr period during the early Pleistocene.The author argues that Asian dust input in the ASB during the early Pleistocene was controlled by the climate fluctuation in the low latitude tropics Pacific and high-latitude.Since the Mid-Pleistocene,the climate fluctuation in the high latitude became the main factors which control the dust input in the ASB.(3)Hole U1438 in the ASB is influenced by both EAWM and Westerlies,and Asian dust in the ASB is derived from Taklimakan desert and the Mongolian Gobi.Because of the difference of climate system,the composition of clay minerals assemblages for the two dust source area is significantly different.The(illite+chlorite)/smectite ratio in hole U1438 decreased significantly during 1.5-0.7 Ma,and kaolinite/chlorite ratio increased,which are similar with the decreased dust flux in hole 885/886 in the north Pacific where was influenced by Westerlies,but the clay ratios in Hole U1438 are different from the southern Philippine sea where was influenced by the EAWM.The author argues that the North-South movement of the Westerly jet forced the varied contribution of the different dust source area.During the 1.5-0.7 Ma,the Westerly jet moved to the north of the Tibet Plateau later in the spring and resulted in dust from the Taklimakan desert decreasing.In the late and early Pleistocene(after 0.7 Ma,before 1.5 Ma),the Westerly jet moved to north side of the Tibet Plateau earlier in the spring and resulted in the contribution of Taklimakan dust increase.