论文部分内容阅读
选取珠江三角洲区域位于广州番禺的PD钻孔进行沉积物岩石磁学和环境磁学记录的研究.岩石磁学实验表明钻孔大部分沉积物以低矫顽力的磁铁矿类矿物为主要控磁矿物,但仍存在少量铁硫化物.在有机质丰富的灰黑色黏土沉积中,铁硫化物含量增加,成为影响沉积物磁性特征的主要矿物,标志着海退后富含有机质而缺氧的沼泽环境.以赤铁矿和针铁矿类矿物为主要控磁矿物的花斑黏土,表明了一个较长时期的暴露风化过程,代表着沉积间断.在以磁铁矿类矿物作为主要载磁矿物的沉积物中,磁铁矿浓度及粒度的变化主导磁化率(κ)、饱和等温剩磁(SIRM)等环境磁学参数的变化,SIRM/κ和χarm/SIRM的大小旋回响应于海平面的升-降过程,它们的高值反映了磁性矿物粒度变细、海平面上升.在沉积学分析的基础上,根据环境磁学参数截然不同的变化规律,结合微体古生物数据,将珠江三角洲沉积物代表的环境分为两次显著的海平面上升-下降旋回,晚更新世和全新世的海侵又包含若干个比较明显的次级海平面波动过程.
We selected the PD drilling in Panyu, Pearl River Delta region to study the sedimentary rock magnetism and environmental magnetism records.The rock magnetic experiments show that most of the sediments in the boreholes are dominated by magnetite minerals with low coercivity However, there is still a small amount of iron sulfide.With the accumulation of organic matter-rich gray-black clay, the content of iron sulfide increases and becomes the main mineral that affects the magnetic characteristics of sediments, marking the return of rich organic matter and hypoxic marsh Environment. The blooming clay with hematite and goethite minerals as the main magnetite indicates a longer period of exposure to weathering and represents a discontinuity in deposition. In the case of magnetite minerals as the major magnetite minerals , Changes in magnetite concentration and particle size dominate the changes in environmental magnetic parameters such as susceptibility (κ) and saturation isothermal remanence (SIRM). The magnitude of SIRM / κ and χarm / SIRM gyrations respond to changes in sea level - descending process, their high values reflect the finer grain size of magnetic minerals and sea level rise.On the basis of sedimentology analysis, based on the distinct variation of environmental magnetic parameters and the data of micro-organism paleontology, Environmental divided into two deposits on behalf of the delta significant sea level rise - fall cycle, the late Pleistocene and Holocene transgression also contains a number of sea-level fluctuations more obvious secondary process.