古地磁场相对强度的非热剩磁法测定及初步结果

本文叙述了近年来国际上新兴起的利用沉积剩磁与非磁滞剩磁以及饱和等温剩磁的比值推求古地磁场相对强度的基本原理以及该方法应用于石灰岩洞穴二次沉积物磁性分析上的可行性及优越性,并使用我国广西石笋样品求出了中国6000年以来的古地磁场相对强度的变化规律。该规律具有三个特点:1．若干个以1000年为短周期的运动,复合于一长周期运动之内;2．存在五个极大值及五个极小值;3．目前地磁场相对强度近于极小值区。

NONTHERMOMAGNETOMETRY OF PALEOMAGNETIC FIELD INTENSITY AND ITS PRELIMINARY RESULT

The authors describe in this paper the fundamentals of estimating relative paleomagnetic field intensity by the currently used nonthermomagetic met-hod, which utilizes DRM/ARM and/or DRM; SIRM as indicators in pa,leomag-netism of unconsolidated sediments. The feasibility and the advantage of ap-plying the method to speleothems (secondary deposits of limestone cave) are nga.Iso demonstrated. We applied the me thud to a stalagmite sample from Cruangxi, China and estimated the variation in relative intensity of paIeomagnetic field over the past 6000 years. "Che variation has three major features:1 .Several short-period oscillations of 1000 years are superimposed on a longer-periori oscillation.2. There are fiva maximum peaks and five minimum peaks in the variation.3. The present }eo:na}netic field intensity approaches the minimum value.