中山舰沉积物基本特征与断年意义

通过中山舰沉积物的纹层、磁化率、铁磁性物质与长江水位、大气污染的磁性物质来源关系等,并结合文史资料,得出沉积物磁化率的显著变化可作判别沉积物相对年代的指标,而沉积物中与现代工业发展相关的圆球状磁性金属废渣可作为判别沉积物确切年代的标志。沉积物磁化率的明显增强的原因是环境变化引起的铁磁性物质的增多,圆球状金属废渣的首次出现是武钢投厂对大气环境污染的结果,其指示年代为1959年。磁化率相对较低的沉积物沉积年代为1938-1958年,而磁化率明显增强的沉积物年代为1959年以后。研究表明,采用的沉积物磁性特征与文史相结合的断年方法,具有原理简明、操作方便、研究成本低等特点,适合内陆人口密集地区大尺度沉积环境普查研究的需要,并且不受沉积环境、沉积类型差异的影响。

Primary Characteristics of Sediments from Zhongshan Warship and Its Dating Function

It is suggested that the remarkable changes of magnetic susceptibility in sediments can be used as the distinguishing indicator of the relative ages of sediments and the spherical magnetic metallic waste, which is related to modem industry in sediments, may be used as the marker of determining ages by analyzing the relations of veins, magnetic susceptibility and ferromagnetic minerals in sediments from Zhongshan warship and Yangtze water level and ferromagnetic minerals carried by atmospheric pollution, as well as historical documents, in this paper. The evident increasing magnetic susceptibility in sediments is considered as the increase of ferromagnetic minerals being caused by environmental changes. It is in 1959 that the spherical magnetic metallic waste is first found in sediments, which is corresponding to that Wuhan Company of Iron and Steel put into the river. It was among 1938 and 1958 when the magnetic susceptibility in sediments are relatively low and after 1959 when the magnetic susceptibility in sediments was evidently increased. It is concise in principle, convenient in practice and inexpensive in cost to use the dating method of combining magnetic characteristics of sediments with historical documents. The method can be used in investigations of great scale sedimentary environment in the crowded population regions in inland and will not be affected by the changes of sedimentary environment.