Paleoceanographic Implications Of The Core On The Continental Shelf Off The Ross Sea Since 15 Ka

In this study,base on the multi-parameters measurement,including AMS14 C dating,organic carbon,grain size and factor analysis of grain size data,of gravity core JB04,sampled in the continental shelf of the Ross sea,After studying the sedimentary strata and process and discussing the paleoceanographic significance,several conclusions were drawn as follows:(1)The change of sedimentary environment has produced four different sedimentary facies in the past 15 ka.Between 15.0 ka.B.P.~11.7 ka.B.P.,the sedimentary facies is dark greenish gray diamictite without stratification covered by ice sheet,and the sedimentation process was mainly dominated by glacial scraping corrosion.Between 11.7 ka.B.P.~9.5 ka.B.P.,the sedimentary facies is dark greenish gray diamictite with weak stratification which deposited under the ice shelf.Between9.5 ka.B.P.~7.0 ka.B.P.,the sedimentary facies is dark greenish gray diamictite without stratification which deposited in front of the ice shelf.Between 7.0ka.B.P.~2.6 ka.B.P.,the sedimentary facies is olive gray siliceous mud and ooze deposited in seasonal sea ice environment and was affected by iceberg.(2)The sources of paleoproductivity in the study area were different as the sedimentary facies changed.Between 15.0 ka.B.P.~11.7 ka.B.P.,the core station was covered by ice sheet which isolated the nutrients and sunlight.the paleoproductivity was low.Between 11.7 ka.B.P.~9.5 ka.B.P.,the core station was under ice shelf,as the melting of the ice shelf amounts of nutrients was released,the paleoproductivity in study area began to increase,mainly was calcarecous productivity;Between 9.5ka.B.P.~7.0 ka.B.P.,the core station was in front of the ice shelf,as the ice shelf further receded,the calcareous productivity began to decrease,and the growth of thesiliceous productivity was slower.Between 7.0 ka.B.P.~2.6 ka.B.P.,the core station was in seasonal sea environment,the paleoproductivity was high and mainly was siliceous productivity.(3)The LGM grounding line is interpreted to have extended about 74.4°-75.3°S in the Joides basin,mainly affected by the topography and the Modified Circumpolar Deep Water.Retreat of the grounding line must have occurred in Joides basin by 13 ka.B.P.,between 13.0 ka.B.P.~11.7 ka.B.P.the rate of retreat was slow between 13.0 ka.B.P.~11.7 ka.B.P.,but from 11.7 ka.B.P.~7.0 ka.B.P.,the rate of retreatment was as high as 50~60 km/ka.