Western Ross Sea Sedimentary Environment Reconstruction Since The Last Glacial Maximum

Analyses of grain size,organic carbon/nitrogen and their isotopes,and biomarker have been carried out for the core ANT32-RB16C,in order to identify the source of the organic matter and reconstruct the sedimentary environment characteristics since the Last Glacial Maximum in the western Ross Sea.From the bottom to the top within the core,sub-ice-shelf,pre-ice-shelf and open-marine sedimentary environments can be identified.The combined parameters of ?13C,TOC/TN,n-alkanes,sterane and terpane indicate that the organic matter represents mainly a mixed input from terrigenous and marine sources.During the LGM(24.8~20ka BP),under the influence of ice sheet and the Dense Shelf Water(DSW),the organic matter content was low and its source was associated mainly with a marine origin,with a relatively low plankton productivity,During the Last Deglaciation(20-11.7ka BP),the organic matter released by the melting glaciers that caused the retreating of the Ross Ice Shelf resulted in an increase of terrestrial organic matter supply.During the Oscillation I(18.5~17ka BP)period,the hydrodynamic environment fluctuated significantly,as is indicated by significant variations in the organic matter content and material sources.During the period of the Antarctica Cold Reversal(ACR)(14~12ka BP),the organic matter content increased slightly and its source was of a marine origin,probably ascribed to strong hydrodynamic environment characterized by Dense Shelf Water(DSW)sinking.During the Holocene,the content of organic matter increased significantly,together with the proportion of marine input.The number of prokaryotes such as bacteria increased,resulting in a greater degree of degradation of short-chain n-alkanes.During the Oscillation?(4.2?lka BP),the organic matter content was high,with great oscillations and complex sources,which may be caused by the instability of allogenic organic matter input with the rise and fall of human civilization and the increase of authigenic organic matter.In general,from the LGM to the Last Deglaciation,in the study area the sedimentary environment was affected by the Ross Ice Shelf,whilst since the Holocene it was influenced by climate change.The redox condition in the study area was mainly controlled by the range of the ice shelf and sea ice coverage,rather than the Antarctic Bottom Water(AABW)which had its unique organic matter and oxygen contents.