河北省阳原盆地井儿洼钻孔磁化率、粒度反映的环境意义

ENVIRONMENTAL SIGNIFICANCE OF MAGNETIC SUSCEPTIBILITY AND GRAIN SIZE IN JINGERWA CORE, YANGYUAN BASIN

根据河北省阳原盆地井儿洼钻孔岩芯湖相沉积物的粒度特征 ,划分出大约0 2Ma以来 ,井儿洼地区经历了湖沼 -浅湖 -滨浅湖 -滨湖的演化过程 ,其中至少存在 8个高 -低水位变化旋回。湖泊不同的演化阶段应用不同的粒级颗粒含量来作为环境指标。在滨湖环境下 ,50～ 1 0 0 μm ,>50 μm及中值粒径具有良好的环境指示意义 ;浅湖环境中 ,<5μm或 2～ 50 μm的细颗粒是较好的指标。不同的沉积相中 ,磁化率的强度与分粒级颗粒含量的相关性不同 :滨 -浅湖相中磁化率强度与粗粒沉积物呈正相关 ;湖滨沼泽相中磁化率强度与细粒含量呈正相关 ;咸化滨湖中磁化率与粒度基本不相关。

Based on the characteristic of grain size, the evolution of Yangyuan lake was divided into swamp, shallow lake, shallow-coastal lake and coastal lake, including eight high-low cycles, during the past 200ka. The 50～100μm grain size, >50μm grain size and median are the valid indicators of environmental change in coastal lake. The fine particle, <5μm and 2～50μm grain size, is good porxy in shallow lake. The values of magnetic susceptibility in Yanyuan lake are controlled by the amount of chemical deposit, grain size and sedimentary facies. They have positive correlation with the content of coarse particles in shallow-coastal lake, and with the content of fine particles in shallow lake. They have no clear correlation in coastal salt lake.