Fluctuation of the South Pacific Albacore Stocks (Thynnus alalunga) Relative to the Sea Surface Temperature

Abstract

This paper presents a paleomagnetic intensity record for late Quaternarytime in Taiwan.Samples came from the lower part of an 86-metersedimentary piston core drilled in the Wukou area of the Taipei Basin.Theage interval of the studied portion,as determined by C-14 dating(Liu et al.,1994),was proposed to be between 9,000 yr.B.P. and 21,000 yr.B.P.Naturalremanent magnetization(NRM),anhysteresis remanent magnetization(ARM)and low field magnetic susceptibility(x)of the samples were analyzed.Results show that the stratigraphical variation patterns of NRM/x andARM/x,after 20 mT alternating field demagnetization treatments on bothNRM and ARM of samples,are very similar.This implies that the acquisitionof NRM and ARM are under the same magnetic mineralogical conditions.Thus,the ratio of the NRM to ARM at this demagnetization stagecould represent the paleointensity secular variation of geomagnetic field inthe area studied.Four major high peak areas were found in the NRM/ARM record(after20 mT demagnetization).These were at about 60m,70m,80m and 90m in depth.Three of them could be correlated to another intensity recordanalyzed from a lacustrine sediment core drilled in the Taihu area of China(Wang et al.,1997).Comparing these two records,and the C-14 dated agesof the two cores,the correspondent ages of the four intensity high peakswere proposed to be about 10,000,13,500,17,500 and 21,000 years beforepresent,respectively.In addition,the age assigned to the peak at about 60m in depth is also supported by the volcanic records in Japan(Tanaka,1990).Thus,the record of this study presents a regional secular variationpattern of paleo-intensity of the earth's magnetic field during the last 9,000to 21,000 years in East Asia.