Biomakers In Late Middle Pleistocene Sediments On The Eastern Coast Of New Zealand And Their Paleoenvironmental Significance

It is expected that multiple biomarkers can be used to trace the source of sediments in the Canterbury Basin on the eastern coast of New Zealand and to restore the temperature of the local paleoenvironment.The ratios of some biomarkers can also be used to reconstruct the community structure of phytoplankton.The biomarkers actually extracted from sediments from IODP317-U1352B core during MIS 7-8 include n-alkanes and sterols.The parameters obtained from n-alkanes include CPI?TAR??T/?M?ACL?P_aq?AI etc.There are also some sterols extracted from the sediments,which can be used to reconstruct the community structure of phytoplankton.Comparing with other paleo-oceanic indicators,CPI values,as indicative parameters of sediment sources,show different characteristics in glacial and interglacial periods.The characteristics of MIS 7d and MIS 8 are similar,which indicates that the input of terrigenous materials in the two cold periods is less than that in the warm periods(MIS7a^c,which indirectly proves the reliability of CPI parameters.TAR??T/?M and ACL show good consistency and the same trend during the glacial/interglacial periods.Through the analysis of these three parameters,it can be seen that land-source input is more in MIS 7a^c and MIS 7d periods,which is obviously higher than other periods,showing glacier melting and carrying land-source material into the ocean.The variation of Paq parameter indicates that the content of terrestrial organic matter is high in the MIS 7a^c period,and there are more phytoplankton in the sediments during the transition from the Little Ice Age to the Little Warm Age in the MIS 7 period.On the whole,there are fewer macrophytes on the continental slope of the southeastern coast of New Zealand.According to AI index,the content of herbaceous plants in terrestrial organic matter was always higher than that of woody plants except in the early MIS 7d.In the whole cycle,the proportion of C₂₇ sterols was significantly higher than that of the other two.It can be seen that zooplankton was always dominant in the community structure of sediments,while the proportion of higher plants was slightly lower than that of zooplankton.The lowest proportion was phytoplankton.Compared with MIS 7and MIS 8,the content of zooplankton and phytoplankton decreased slightly in the glacial period,increased in interglacial period,which is in accordance with the environmental changes.