11:30 AM - 11:45 AM
[SEM34-04] Relative paleointensity variation in the Middle Eocene estimate to the marine sediment cores recovered from IODP Site U1403
Keywords:paleomagnetism, marine sediment core, relative paleointensity
It was estimated that 25-160 mcd covered 40.145 Ma (chron C18n.2n/C18r) to 49.344 Ma (C22n/C22r) from the paleomagnetic polarity stratigraphy based on the result of the natural remanent magnetization (NRM) measurement. As a result of Anhysteretic remanent magnetization (ARM), Isothermal remanent magnetization (IRM), ARM/SIRM and S-ratio (-0.1, -0.3 T), 50-101 mcd (40.145 Ma (C18n.2n/C18r) to about 44 Ma (C20r)) interval is considered relatively homogeneous rock magnetic property. Thus, we estimated RPI of this interval.
According to the RPI variation, the shows the minimum on the chron boundary and variation with the big amplitude within chron. In three chron (C18r/C19n, C19n/C19r, C19r/C20n) boundary before and after showed that the intensity decreased with a reversal gently for about 50 ka and the intensity suddenly increased and recovered for about 10 ka. These characteristics are similar to a characteristic to be seen in the RPI of the past 2 million years and the five times reversal boundary during this period (Valet et al., 2005). The reversal frequency of middle Eocene was about half of the present (Merrill et al., 1996). It is suggested that these characteristics are common to paleointensity, regardless of the reversal frequency, continuous middle Eocene to the present.