舟山DZ-1钻孔沉积物粒度特征与沉积环境辨别

Sediment grain-size characteristics and sedimentarysignificance of DZ-1 borehole near Zhoushan Islands,East China Sea

本文对在舟山群岛附近海域钻取的第四纪钻孔进行了粒度测试和分析。结果显示,沉积物平均粒径介于2.18～7.76Φ,分选较差—差,偏度介于-1.75～2.76之间,表现为平坦、正态分布。这些粒径变化特征揭示了沉积动力环境的变化,粗粒沉积物对应了高水动能环境,细粒沉积物对应了低水动能环境。用粒度参数散点图对沉积环境判别表明粗粒沉积物与现代东海陆架沙脊、扬子浅滩、潮流沙脊间洼地和河道沉积等类型相近,可能指示快速海进过程中的高能沉积环境,如河道等,亦或是陆相侵蚀环境;细粒沉积物与现代泥质区沉积类似。沉积物粒度在垂向上的准旋回性变化可能指示了气候冷暖交替背景下沉积动力发生了显著变化。

A research on the sediments of DZ-1 borehole drilled from East China Sea near Zhoushan Islands was conducted for sediment grain-size analysis.The results indicate that the average grain size ranges 2.18-7.76Φ,poorly sorted,mesokurtic,with skewness ranging-1.75-2.76.The coarse-fine changes of grain size can be correlated with sedimentary dynamics,which fine sediments indicate a relatively low dynamics,and coarse sediments indicate a high dynamics.The relationship among the sediment grain-size parameters of coarse sediments suggests the characters are close to continental sandy ridge of East China Sea,Yangtze Shoal,low-standings of tidal flats,and river in channels,indicating a high dynamics possible during a rapid transgression or erosional facies due to regression;and the one of fine sediments is similar to the modern sediments in muddy zone in East China Sea.The vertically quasi-cyclic changes of the sediment grain-size will be a potential indictor for cold-warm climate-related sediment dynamics.