Sediment Source Analysis And Rare Earth Elements Composition Research In Mendeleev Ridge Of Western Arctic Ocean During The Late Quaternary

The Arctic Ocean has a rapid response to climate change through its unique geographical environment and extensive sea ice distribution.Water structure,biome composition and atmospheric circulation in Arctic Ocean have obviously changed due to significant reduction in sea ice area and thickness caused by global warming in the past 40 years.These changes will not only affect the Arctic region,but also the mid-latitude regions,the northern hemisphere and even the global areas through the amplification effects of the Arctic Ocean on climate change along with the East Asian Monsoon and global thermohaline circulation.Therefore,it is significative to study the complex influence patterns of the Arctic on global climate in long-time scale variation of the glacial-interglacial periods,and then reconstruct the evolution dynamics of the ice sheet,ocean current and material transportation in the Arctic Ocean through a variety of methods.In this paper,the core of ARC07-E25 raised from the Mendeleev Ridge during Chinese seventh Arctic Scientific Expedition is compared with the core of HLY0503-8JPC and PS/72-343-1 with reliable age model.We established a?200ka age framework,rebuilt the evolution pattern of ice sheet and ocean current and analyzed the sources of sediment and the control mechanism of rare earth elements?REE?in E25 core of Mendeleev Ridge,all results based on color reflectance,AMS14C dating and foraminifera stable carbon and oxygen isotopes,paleomagnetic inclination,major and trace elements?including rare earth elements?and bulk mineral content data.Total rare earthchanges between 122.37 to 231.94?g/g.The northern American Shale normalized records of the sediments generally show enrichment in medium rare earth element?MREE?and light rare earth element?LREE?which dominated by lanthanum?La?,Cerium?Ce?and neodymium?Nd?,while heavy rare earth element?HREE?also shows advantages of independence.It's apparent in the results that Ce is the absolute dominant element in thewhich has a strong control over it and the main source of REE is detrital material from Laptev Sea and East Siberian Sea with high LREE content.REE has a great affinity with fine grains less than 63?m,and will be affected by water REDOX environment at the same time.Consequently,thecontent is increasing in the brown layers representing oxidation condition and decrease in the gray layer representing reduction condition.Reconstruction of paleoenvironment shows that Mendeleev Ridge was controlled by the Beaufort Gyre?BG?during the interglacial/stadial periods?MIS 7/5/3/1?,when the Transpolar Drift?TPD?retreated and material from the Canadian and Alaskan Arctic transported to the study area in large quantities.The presence of Pink-White-Layer in MIS 7/5d/3 periods indicate the material input of Laurenteide Ice Sheet?LIS?,the high calcite content mainly contributed by clastic carbonate with less bio-carbonate,and partial calcite dissolution in the MIS7 period.The comprehensive analysis reveals that the material input of Mendeleev Ridge during the interglacial/stadial rely on not only sea ice and icebergs transported driven by ocean currents,but also on the shelf process across the basins related to the nepheloid,sea ice salting out and transportation of the mid-depth ocean current.The Mendeleev Ridge was greatly influenced by TPD in the glacial periods?MIS 6/4/2?,and deposited typical minerals of Eurasian provenance such as feldspar,quartz and pyroxene.The anomlies in IRD content and sedimentary rate in MIS6 indicate that the Mendeleev Ridge may be affected by the ice cover.The extremely low values ofalso prove that the transportation capacity of surface current has significantly decreased or even sluggish at this time,suggesting that the mineral components and sediments may be carried by glacier extension.Increase in?La/Yb?_NASCindicates the proportion of material from East Siberia is lager in the Mendeleev Ridge sediments since the last glacial period.Nevertheless,the quartz content in E25sediments continued to increase,while the pyroxene and feldspar content decreased after MIS 3,suggesting that the multiple ice-melt water discharge events of the LIS and the enhancement events of BG during the last deglaciation period had significant effects on the sedimentary environment of the west Arctic Ocean.