东海海底末次冰期埋藏风尘黄土地层初步研究

大量海底调查及钻孔岩芯资料揭示,东海海底全新世疏松沉积物之下,往往埋藏着一层厚度不大的黄褐色、暗绿色硬质粘土层。类似的硬土层在长江三角洲东部平原地层中普遍存在。作者曾对苏北、苏南平原地层中该硬土层与下蜀黄土地层进行对比研究工作,并在野外地层剖面上发现两者为连续延伸地层,认为该硬土层为末次冰期风尘黄土沉积物经埋藏后的次生成土作用演变而成。 本文通过对东海海底硬土层岩芯地层综合分析研究,以及与长江三角洲东部平原区硬土层和下蜀黄土地层沉积物特征对比,认为东海海底硬土层为末次冰期低海面期间,干、冷气候条件下的风尘黄土堆积物,后经埋藏后的次生变化而形成。而在绝大部分海底,由于受到全新世海进作用的强烈冲蚀而缺失,只在局部地区仍有保留。

ON THE BURIED AEOLIAN LOESS STRATA OF THE LAST GLACIAL PERIOD IN THE FLOOR OF THE EAST CHINA SEA

East China Sea floor investigation and core data have showed that Holocene basement consists of yellow-brown or dark-green hard clay of 0.1-2m in thickness, buried beneath the soft Holocene deposits. The similar hard clay is widely distributed in the eastern plain and western hilly area of the Yangtze Delta. We concluded that the hard clay of the East China Sea,the buried plain hard clay and hilly loess are quite similar to each other in particles,chemical composition,mineral assemblage,clay mineral and trace element under scanning electron microscope. It is found that they have a continuous stratigraphy. Therefore,it is supposed that the hard clay in the East China Sea floor is aeolian loess in origin,deposited in dry-cold climate condition during the last glacial period. Because of severe scouring by Holocene transgression, most of the hard clay in the East China Sea floor is absent,only part of it is preserved now.