Comparative Study Of Sediment Cores From The Chukchi And Bering Basins And Its Paleoceanographic Implications During Late Quaternary

Core M01dredged from the Chukchi Basin and core BR02from the Bering Basin were selectedfor comparative study of Late Quaternary paleoceanography in the polar and subpolar region. Based onnumerous studies of sediment grain size、color reflectance and elemental geochemistry, severalconclusions are summarized as follows:(1) The color reflectance of M01core display a cyclic sequence of brown beds and gray beds, theformer indicates interglacial periods such as MIS1, MIS5and MIS7, and the later indcates glacialperiods such as MIS2~MIS4and MIS6. Several events of ice rafted debris (IRD) happened before warmperiods including the middle Holocene, MIS5.1, MIS5.3, MIS5.33, MIS7.1, MIS7.3. In MIS2-4andMIS6the Chukchi basin is under the control of the Laurentide ice sheet with huge thickness, there isalmost no IRD in gray beds glacial sediments.(2) BR02core locate at the south of the largest periglacial line of modern winter(March-reference), it is not affected by the ice raft debris throughout the Holocene. But it recordmultiple significant long ice raft debris events (Including H0、AL1、AL2、AL3、AL4、H4and H5) inLast deglaciation and MIS3/2transition, it is very sensitive to the change of Laurentide ice sheet, Eachfluctuations of the temperature in millennial scale may lead to ice raft debris events.(3) Pending the interglaciation, Chukchi basin and borderland is covered by seasonal sea ice, theAtlantic water, and Beaufort Gyre which carrying ice raft debris are strengthened, stratification ofsaltwater and freshwater is weak, the bottom water has high oxygen content. The sediments formated inthis period is brown or yellowish brown, have elevated concentrations of Mn, Co, Ni and Cu, higherplanktonic foraminifera and other organisms left shell, more ice raft debris. The Pacific water thatinfows via the Bering Strait is also enhanced, which is characterized by high nutrient and volcanic ashcontents with Na-rich minerals.(4) The concentrations of Mn, Ba in the upper part of BR02at17-21cm is high, whichcorresponding to of the mid-Holocene warm period, when the Bering Strait is open, water exchangebetween the Bering Sea and the Arctic increased, thereby the circulation in the Bering basin isstrengthened. Water stratification is weak, the bottom water is in redox condition, siliceous organismproductivity is also high.