末次冰消期以来苏拉威西海颗石藻化石记录与古海洋变化

通过对苏拉威西海MD98-2178柱状样(3.62°N、118.70°E)颗石藻化石属种相对含量的统计,重建了2万年来海水古生产力、营养跃层的变化。其中Emiliania huxleyi、Gephyrocapsa oceanica、Florisphaera profunda占颗石藻群落的80%~90%。由于G.oceanica与F.profunda存在于两种完全不同的生态环境中,两者的变化趋势完全相反。前者代表高生产力以及高营养物质的海水,后者则代表低生产力与较深的营养跃层。推测冰消期颗石藻对环境变化具有两种响应模式:以约13.5 ka的生产力峰值期为界,13.5 ka之前颗石藻古生产力变化主要响应于径流对海洋营养物质的输入,而13.5 ka之后则主要响应于海水-大气之间水循环的强度。全新世F.produnda含量及其所反映的营养跃层变化具有明显的百年尺度波动,与太阳活动的100~260 a周期具有良好的相关性。推测全新世苏拉威西海区营养跃层变化受百年尺度的类似厄尔尼诺-南方涛动(El Nino-Southern Osillation,ENSO)的变化及太阳活动的驱动。

COCCOLITHOPHORE RECORDS AND THEIR RESPONSE TO PALEOCLIMATIC AND PALEOENVIROMENTAL CHANGES IN SULAWESI SEA FROM THE LAST DEGLACIAL

To reconstruct the variation in paleoproductivity and nutricline of sea water over the last 20 ka,we analyzed the relative abundance of coccolithophores in deep sea core MD98-2178(3.62°N,118.70°E),Sulawesi Sea.Three coccolihophores species,Emilania huxleyi,Gephyrocapsa oceanica and Florisphaera profunda,representing 80%~90% relative abundance,dominate the coccolith assemblage.Owing to the absolutely different ecological niche between G.oceanica and F.profunda,they experienced inverse variation trend,the former being sensitive to nutritive material in sea water and representing high productivity,and the latter indicating low productivity and deep nutricline.We suggest that two models can be attributed to coccolihophores responding to paleoenvironment around the timing 13.5 ka in the deglacial.Before 13.5 ka coccolihophores and their productivity mainly responded the nutritive material that transported by run-off,and after 13.5 ka they responded to the intensity of hydrology between sea water and atmosphere.Centennial scale oscillations of F.profunda% are found in the Holocene period,being agreement with solar activity in 100~260 years cycles.We infer that long-term ENSO-like conditions and solar activities could force the variation of nutricline in Holocene.