西太平洋暖池区三百万年来的古海洋学事件研究

Quaternary paleoenvironmental sections in West Pacific Warm Pool are established, based on the oxygen isotopic, magnetic and biostratigrapic results of the three cores, ODP Site 1143, 17957-2 and MD97-2140 in this area. Signals of paleo-oceanographic and climatic changes are extracted from these sections. Mid-Pleistocene Revolution, climate transition event, intensified East Asian summer monsoon during the last 700~600 ka and summer monsoon enhanced during the interglacial periods and declined during the glacial periods are found from the records of radiolarians and biogeinc compositions. Paleo-oceanographic and climatic changes in West Pacific Warm Pool were forced by 100 ka eccentricity and 20 ka procession cycles based on spectral results of productivity and thermocline proxies. Biogenic bloom event occurred during the Miocene in Indian and Pacific are recorded in the biogenic compositions in the South China Sea. Comparison of the biogenic silica accumulation at Site 1148 of the SCS with that at Site 929 of the Atlantic verifies that the biogenic silica accumulation between the low latitude Pacific and Atlantic oceans expresses as evident relationship of compensation during the Oligocene. XRD analysis and SEM observation of the samples from Site 1148 demonstrate that most of radiolarian, diatom and sponge spicule have suffered from dissolution and reprecipitation, suggested by the opal-A→opal-CT→quartz transformation.

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