【摘要】 上新世最重要的古气候事件就是北极冰盖的形成和扩张(3.2—2.5Ma)。根据北极冰盖的形成过程,文中将上新世—早更新世(4.5—1.6Ma)西太平洋暖池核心区ODP807A孔2个浮游有孔虫属种Globigeri-noidesruber和Pulleniatinaobliquiloculata的δ18O(氧同位素)、δ13C(碳同位素)记录数据细分为3个阶段:形成前(4.5—3.2Ma)、形成中(3.2—2.5Ma)和形成后(2.5—1.6Ma)。研究结果表明,北极冰盖形成以来,G.ruber和P.obliquiloculata的δ18O值均呈增大趋势;北极冰盖形成中,G.ruber的δ18O值基本不变,P.obliquiloculata的δ18O值略增大,反映出西太平洋暖池次表层海水受北极冰盖形成的影响更甚;Δδ18O(P-G)(G.ruber和P.obliquiloculata的δ18O的差值)反映出温跃层无明显变化,受北极冰盖形成影响微弱。根据用Ma/Ca值得到的ODP806站SST值(Waraetal.,2005)以及用U3K7’得到的东太平洋ODP847站SST值数据(HerbertandLaura,2010),对北极冰盖形成以来东西太平洋古海洋学演化进行比较发现:冰盖形成以来东西赤道太平洋海水表层温度均有所下降,且东太平洋降温幅度更大;对比同时期的西太平洋ODP807A孔Δδ18O(P-G)与东太平洋ODP847站Δδ18O(T-S)的变化趋势,发现东太平洋温跃层变浅,表明受北极冰盖形成和扩张的影响,东西太平洋温跃层深度梯度增大。对比ODP807A孔与南海南部1143站、南海北部1148站G.ruber的δ18O和δ13C记录,揭示西太平洋边缘海如南海北部和南部受北极冰盖形成的影响有所不同,北部的表层海水温度和生产力水平受冰盖形成的影响更加明显。更多还原

【Abstract】 The most important palaeoclimate event in the Pliocene is the formation and expansion of the Arctic Icecap during 3.2-2.5 Ma.We obtained δ18O(oxygen isotopes),δ13C(carbon isotope)record data of planktonic foraminifera Globigerinoides ruber and Pulleniatina obliquiloculata from the Pliocene-Early Pleistocene interval(4.5-1.6Ma)in ODP807A in the Western Pacific Warm Pool.Based on the formation process of the Arctic Icecap,the above data can be divided into three stages:prior to Icecap formation(4.5-3.2Ma),during Icecap formation(3.2-2.5Ma)and after Icecap formation(2.5-1.6Ma).The results show that since the Icecap formation,δ18O values in both G.ruber and P.obliquiloculata showed increasing trend,respectively indicating the continuous temperature decrease in the surface and subsurface in the Warm Pool.During the Icecap formation,the δ18O value of G.ruber changed little,but that of P.obliquiloculata was heavier,which indicate that the subsurface was affected more strongly by Icecap formation.The δ18O difference between P.obliquiloculata and G.ruber(or Δδ18O(P-G)) reflects little change in the depth of thermocline,implying a very weak influence from the Icecap formation.According to the Mg/Ca value from ODP806(Wara et al.,2005)and UK’37 value from ODP 847(Herbert and Laura,2010),both the surface temperature of western Pacific Ocean and the eastern Pacific Ocean decreased since the Arctic Icecap formation,and a greater range of the eastern Pacific.Compared with Δδ18O(P-G) from the western Pacific ODP807A with Δδ18O(T-S) from the eastern Pacific ODP847 at the same period,the eastern Pacific thermocline changed shallowing,suggesting the gradient of the depth of thermocline between the western and eastern Pacific enlarged.Compared δ18O and δ13C value between G.rubber and P.obliquiloculata at Site 1143 and Site 1148,it also indicated that the surface temperature and the productivity level were more evidently affected in the northern(Site 1148)than in the southern South China Sea(Site 1143).更多还原