Magnetic Properties of Marine Sediments from the East Philippine Sea
|School||Graduate School , Chinese Academy of Sciences ( Institute of Oceanography )|
|Keywords||East Philippine Sea marine sediment magnetic properties paleomagnetism rock magnetic|
This paper presents the results of systemic paleomagnetism investigation anddetailed rock magnetic investigation of the marine sediments from the East PhilippineSea on the basis of the application of the newly developed environmental magnetictechniques. The research of multiple magnetic parameters shows the sorts and contentof magnetic minerals in sediments. The source of magnetic mineral, the paleoclimaticvariation and sedimentary environmental changes were discussed, and theenvironmental magnetic evidence was provided.A systemic alternating field demagnetization has been done on the seven cores.We have got the characteristic remnant magnetism of all the samples. A comparisionof geomagnetic polarity of marine sediments with the geomagnetic polarity time-scaleby A.Cox has been made, we discovered the clear boundary between Bruhnes normalepoch and Matuyama reversed epoch in most cores, the Jaramillo event during theMatuyama period was identified. The age and rate of accumulation of the sedimentshave been estimated.The susceptibility value of marine sediments is relatively low and its curvefluctuates rhythmically. A detailed magnetic analysis has been done on the coreF090102 from the Parece Vela Basin, the following magnetic parameters weremeasured: susceptibility (χ), anhysteretic remnant magnetization (ARM), isothermalremnant magnetization (IRM), saturation isothermal remnant magnetization (SIRM),IRM-300mT (induced in a field of -300mT) and typical temperature dependence ofmagnetic susceptibility curves (χ-T). First, a magnetostratigraphic record wasobtained. The Bruhnes-Matuyama reversal, the Jaramillo event, as well as the Olduvaievent during the Matuyama period, were identified. Analyses of magnetic parametersdemonstrated that magnetic minerals in the sequence were dominated bylow-coercivity ferromagnetic minerals with subordinate high-coercivityantiferromagnetic minerals. The χ-T curves results indicate that the magneticmineralogy of the upside and bottom of the core is dominated by magnetite, maybesome titanomagnetites are included, but for the middle parts of core sediments, thecooling curves are under the heating curves, the Curie temperature is about 550℃,maybe ilmenite and some iron-enriched titanohaematite are included. The resultsshow that the rock-magnetic parameters well correspond to the paleoclimaticvariations and sedimentary environmental changes.