东海浪岗山列岛风尘沉积的新证据

New Evidences of Aeolian Deposits at Langgangshan Islands in East China Sea

通过对浪岗山黄土粒度组成、磁化率、碳酸盐、微量化学元素、粘土矿物进行测试和分析，并与其他黄土地层对比发现：1）浪岗山黄土具有10～50μm粒组富集、磁化率为69．3×10^-8～93．8×10^-8m^3kg^-1、粘土矿物以伊利石为主（64．91％～79．35％）等与其他风成黄土相似的风尘沉积特征；2）根据红外释光测年（IRSL）结果，浪岗山黄土剖面底部的沉积年代为41．0±2．5kaB．P．，而沉积速率较快（约为1．53mm／a），应为晚更新世短期内快速堆积的一例风成黄土地层；3）与内陆黄土相比，浪岗山黄土大于50肿粒组均超过10％，明显偏高，表明该剖面除接受来自西北内陆的远源风尘物质外，还接受来自东海陆架的“近源”风尘物质；4）与内陆黄土相比，浪岗山黄土磁化率变化范围不大、碳酸盐含量极低、蛭石含量偏高、微量元素含量偏低，应考虑剖面沉积后气候环境的长期改造作用。

Based on a great deal of field investigations of the islands of East China Sea,an aeolian loess profile at Langgangshan islands was chosen as the study object. Some indices such as grain size, magnetic susceptibility, carbonate, microelement oontent, clay minerals, and infrared stimulated luminescence （IRSL） dating were systematically analyzed. What＇ s more, through the oontrasting to other loess in China, the primary results can be ooncluded as follows： 1）The loess deposits at Langgaugshan has the similar characteristics to the other aeolian loess of China, such as the size oomposition being mainly 10-50μm grains, the magnetic susceptibility varying from 69, 3 × 10^-8 m^3kg^-1 to 93.8 ×10^- 8 m^3kg^- 1, tile primary component of clay minerals being the illite. 2）The dating data of the bottom sample from the study profile determined by infra- red stimulated luminescence （IRSL） is 41.0± 2.5 kaB, P., which affirms that Langgangshan loess was formed during the last glacial period of late Pleistocene as well as Malan loess. But the sedimentation rate of Lauggangshan loess is relativdy higher,about 1.53 mm/a, Langgangshan loess profile is one of aeolian deposit stratigraphy that had formed rapidly in late Pleistocene. 3）Compared with that of other inland loess the content of 〉50μm grains of the loess is relatively higher. As a matter of fact, it indicates that the study profile received not only far aeolian deposit from northwest by strong winter monsoon as other inland loess but also proximal one from inshore shelf area. 4）Compared with that of other inland loess, Langgangshan loess has the inconsistent characteristics as the followings： The smaller variation range of magnetic susceptibility, the lower content of carbonate, the higher content of vermiculite and the lower content of microelement. These facts should be considered as the result from the long eluviations because of moist climate around Langgangshan islands since Holocene.