Clastic Components in Core 1787 from the East Pacific Ocean and Their Paleooceanic Significance

Key words: 
• clastic /
• components /
• paleo-oceanography

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.