摘要:
对太平洋1787站柱状沉积物进行了碎屑组分分布和来源的研究,并根据碎屑组分的分布特征对火山活动和南极底流活动状况进行探讨.结果表明,沉积物中的碎屑组分主要是生物来源、海洋自生来源和火山源,并推测本柱芯沉积期曾有11次火山活动期和9次南极底流入侵.在火山活动期,沉积物中火山来源矿物含量显著增加;在南极底流活动期,沉积物中褐铁矿和微结核等形成于氧化环境的矿物含量较高,生物扰动构造发育.所推测的底流活动期在氧同位素曲线上均有明显反映,并与古地磁资料得出的沉积间断基本吻合,表明沉积物的碎屑组分分布特征能间接指示古海洋事件.
Abstract:
The sediment samples of Core 1787,which is 810 cm in the length was colle cted from the esat Pacific Ocean.The present water depth is 5073 m.Their clastic components,distributions and sources were studied,and an attempt was made to ex tract paleooceanogrphic information from the clastic components in late Cenozice ra. For the mineral analyses,the 0.063～0.25 mm fraction was separated from the sedi ment samples by wet sieving,heavy components were extracted using tribromomethan e(density 2.89).All the minerals were identified using a petrographic microscope,when necessary,immersion oils.The results shows that the heavy components are m ainly micro-manganese nodules,biogenous apatite,limonte,magnetite and pyroxene; and the light components are mainly biogenous opal(the tests of siliceous organi sms,such as radiolaria and sponge-spicule),clay aggregates and volcanic glass.W ith the depth increasing,the abundance of these components varies regularly.It i s revealed that,in Cenozoic era,there are 11 times of valcano actvity and 9 time s of activity of antarctic bottom water(AABW),and the AABW led to at least 8 tim es of hiatuses.In the periods of valcano erruption,the abundnce of volcanic clas ts are appearently increased.In the periods of AABW,the abundance of limonite,mi cro-manganese nodules are high,bioturbation in sediments are strong,and the oxi gen isotope values are lighter.AABW is the main factor to lead to hiatuses and o xidative enviroment.The supposed periods of AABW coincided well with the hitu ses infered by magnetostraitigraphy,sediments structure and DSDP data.It is sugg seted that clastic components and their assemblages can provide mineral evidence s to reconstruct sedimentary environment.
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