Variations In Terrigenous Provenance At The Slope Of The Western Sea Of Japan Since The Last Galciation And Its Paleoclimatic Implications

The Sea of Japan(JS)is one of the marginal seas in the Northwest Pacific Ocean.It's adjacent to the East Asian continent and the Japanese islands and connects with the open sea through four shallow Straits.Dominated by fluctuating air-sea conditions(the East Asian Monsoon,Westerly Jet,Kuroshio,etc)and its own deep-water circulation,the sediments in the JS archive abundant information of paleoenvironmental changes.At present,the JS receives terrigenous materials transported by rivers,wind,sea ice and volcanoes eruption.There are striking difference of terrigenous materials input between different areas,but researches about the western part of JS are rare.Based on the analysis of sedimentology,major and trace element geochemistry and isotopes in the sedimentary core LV53-18-2 in the western part of JS,this paper analysizes the provenance and transport dynamics of sediments in this core and the main factors controlling of it since the Last Glacial,and discusses the paleoclimatic meaning indicated by provenance evolution.A sediment core LV53-18-2 with a length of 393 cm is investigated,which was retrieved from the western JS(42°56?N,134°44?E,551 m depth)during the first ChinaRussia joint cruise in 2010.The age model has been established on the basis of optical stimulated luminescence dating.Based on the measurements of 393 grain-size,132 major and trace elements and 31 radioactive isotope samples,we reconstruct the history of sea ice activity,bottom current intensity and change in provenace with the aid of principle component analysis,end member analysis and correlation analysis.The result show that variations in seasonal sea ice remianed weak,indicating by low content and mass accumulation rate of Ice Rafted Debris(IRD)and Zr(Hf)content during the glacial lowstand of sea level(30 to 18 ka)when the East Asian Winter Monsoon(EAWM)was intensified and the summer insolation at 45°N reduced.The bottom current intensity increased(decreased)when sea ice activity strengthened(weakened),which was suggested by sediment grain size and contents of S(Mo).Meanwhile,the terrigenous materials are mainly derived from the Northeast China sandyland(Horqin).The component of sediments affected by IRD input during seasonal sea ice activities were enhanced.The drastic variations in seasonal sea ice have been corroborated by MARs of IRD and high contents of Zr(Hf)during the last deglaciation and early middle Holocene(15-7.8 ka),which was attribute to a combination of strong EAWM,increased summer insolation and global sea level rise.The huge amount of input of IRDs affected the sediment component indicated by element tracer and low CIA index.The provenance changes obviously show that the terrigenous material from Northeast China sandyland(Horqin)decreased and the weakly weathered components transported by sea ice increased.After 7.8 ka,variations in seasonal sea ice weakened in relation to dampened EAWM and incursion of Tsushima Warm Current.Almost all element data of this period,such as positive Eu anomaly(1.2?1.4),low CIA(52?57)index and high value of ?Nd,show an increasement of volcanic materials.The increased proportion of volcanic materials may indicate the intensification of the Liman Cold Current(LCC)along the coast and the continuous supply of volcanic material to the western JS.