Approaching To The Enviromental Record Since Late Pliocene In The South Margin Of The IRD Belt, The North Atlantic

Since the late Pliocene global climate changed drastically as the arctic ice sheetsformation and expansion. It remains controversial about its evolutionary process.Integrated Ocean Drilling Project (IODP) Expedition306Site U1312B is located atthe south of IRD belt,its upper90m sediment records the history about the growth anddecline of the arctic ice sheets in detail.We use several proxies:G.ruber δ18O and δ13C、G.ruber relative abundance、N.pachyderm（aR/L）、Planktonic foraminiferal abundance、Ice-rafted debris(IRD) content、CaCO3content and Thermoluminescence to reflect thepalaeoenvironment changes The following results have been achieved.1.According to the comparison between U1312B δ18O and LR04,we establish4.1Ma age framework for the IRD belt age analysis.2.The U1312B proxies change characteristics show the positive response to theMid-Pleistocene Transition (MPT).which began971kaBP and was complete by696kaBP Before MPT, the dominant cycle is41ka, during the MPT,the dominant cyclesare41ka and100ka,after the MPT the dominant cycle is100ka..3.The first appearance IRD at2.52Ma indicates the arctic ice sheets expand largeenough to affect the mid-latitude at this time. Since the MPT, the high frequentappearance of IRD which is composed of plenty of carbonate confirm that theHeinrich-Like Events exist before the Last Glacial period. The arctic ice sheet growthand decline mechanism in short cycle will be the principal research focus in thefuture.4.The arctic ice sheet from the formation to the expansion process can be dividedinto four evolution stages:4.1~3.6Ma, the arctic ice cap was in inchoate period;3.58~3.3Ma, the arctic ice cap began to form;3.29~2.86Ma the arctic ice sheet hadbeen formation but it influenced mainly near the58°N area;2.85~2.5Ma, the arcticice sheet expanded large enough to influence the mid-latitude area.5.Thermoluminescence change characteristics show the instructions of thetemperature change in the study area,its the low/high value fit oxygen isotope glacial/interglacial stage very well.Its change characteristics responds positively to theearth orbital cycles. It is reliability that thermoluminescence is feasible alternativeproxy of the paleooceanography.