Magnetic properties of sediments from the Pearl River Delta,South China:Paleoenvironmental implicati

来源 :Science in China(Series D:Earth Sciences) | 被引量 : 0次 | 上传用户:qxy489354518
下载到本地 , 更方便阅读
声明 : 本文档内容版权归属内容提供方 , 如果您对本文有版权争议 , 可与客服联系进行内容授权或下架
论文部分内容阅读
Magnetic parameters and their environmental implications of sediments in a core (PD) from the Pearl River Delta, South China, indicate that ferrimagnetic minerals with low coercivity, such as magnetite, dominate the magnetic properties although small amounts of Fe-sulphides occur. The fraction of Fe-sulphides increases and becomes the dominant minerals determining the magnetic characteristics in grey-black organic-rich clay horizons, indicating an anoxic, sulphate-reducing swamp environment resulting from a marine regression. In the “Huaban clay” , hard magnetic minerals, such as hematite and goethite, largely control the magnetic properties of the sediments and imply a long period of exposure and weathering. Where magnetite is the main magnetic mineral, its fraction and grain size determine properties such as magnetic susceptibility (κ ) and saturation isothermal remanent magnetization (SIRM). Ratios of SIRM/κ and χarm/SIRM reflect changes in sea level with high SIRM/κ and χarm/SIRM correlating with a smaller magnetic mineral grain size and rising sea level. Based on downcore variations of these environmental magnetic parameters along with sediment characteristics and microfauna, the sedimentary environment of the Pearl River Delta area can be divided into two main cycles of transgression and regression during the late Pleistocene and Holocene with more sub-cycles of sea level fluctuation during each transgression. Magnetic parameters and their environmental implications of sediments in a core (PD) from the Pearl River Delta, South China, indicate that ferrimagnetic minerals with low coercivity, such as magnetite, dominate the magnetic properties are small amounts of Fe-sulphides occur. The fraction of Fe-sulphides increases and becomes the dominant minerals determining the magnetic characteristics in gray-black organic-rich clay horizons, indicating an anoxic, sulphate-reducing swamp environment resulting from a marine regression. In the “Huaban clay”, hard magnetic minerals, such as hematite and goethite, largely control the magnetic properties of the sediments and imply a long period of exposure and weathering. Where magnetite is the main magnetic mineral, its fraction and grain size determine properties such as magnetic susceptibility (κ) and saturation isothermal remanent magnetization (SIRM). Ratios of SIRM / κ and χarm / SIRM reflect changes in sea level with high SIRM / κ and χarm / SIRM correlating with a smaller magnetic mineral grain size and rising sea level. Based on downcore variations of these environmental magnetic parameters along with sediment characteristics and microfauna, the sedimentary environment of the Pearl River Delta area can be divided into two main cycles of transgression and regression during the late Pleistocene and Holocene with more sub-cycles of sea level fluctuation during each transgression.
其他文献
1、请求促成战术或称直接请求购买促成战术、直接发问战术。即在推销过程的适当时机直接向顾客提出购买推销产品,这是一种最简单、最基本的成交战术。推销员在推销过程的适
镧对磷钒催化剂性能的影响李铭岫,王心葵,杨述韬,张志新,刘翠格,周敬来(河北师范学院化学系,石家庄050091;中国科学院山西煤炭化学研究所,太原030001)关键词镧,磷钒催化剂,正丁烷,选择,氧化,顺丁烯二酸酐
无应力状态法在大跨径斜拉桥施工控制中得到了广泛的应用,通过它将桥梁施工中间状态与最终的成桥状态之间联系起来,为桥梁施工控制仿真分析计算提供了一种有效的方法,使得在
古时候形容一个人有钱,常说他有“万贯家财”。“万贯”是多少钱,得看什么币种。西汉流行布币,北宋流行铁钱,明初流行纸 In ancient times to describe a person rich, ofte
目的:观察蕲蛇蛇毒对胶原诱导型关节炎(CIA)大鼠的治疗作用,及其对血清肿瘤坏死因子-α(TNF-α)、基质金属蛋白酶-9(MMP-9)、金属蛋白酶组织抑制剂-1(TIMP-1)的影响。方法:采用牛Ⅱ型胶
记者:西部大开发是第三代中央领导集体提出的世纪宣言,具有重大的战略意义。但这次西部大开发的条件、环境与以前相比已发生了很大的变化。经济体制正处于转型时期,市场机制
为认真贯彻执行《新型农村合作医疗基金财务制度》和《新型农村合作医疗基金会计制度》,稳步推进新型农村合作医疗(简称“新农合”)地市级统筹,内蒙古包头市近2年针对市、县
摘要:本文结合网络学习环境的实践运用,探讨目前网络学习环境存在的问题,针对性地提出一套适合Web2.0时代,运用Mashup技术创建网络学习环境的模式。  关键词:网络学习环境;Web2.0;MashupUGC    网络自诞生以来作为知识学习的一种载体,不断发展并逐渐形成了网络学习环境。现在网络环境下的信息服务面临越来越多的挑战,人们努力寻求新的技术和应用来提高信息服务的效率和质量。而运用Web
在当前西部开发的热浪中,全国人大常委、著名经济学家厉以宁提醒人们,开发西部要注意三大问题:第一,西部开发的钱从哪里来?国家可以拨款,但是它主要是搞基础设施,其余的恐怕要
目的探讨极低频电磁场对大鼠生精细胞凋亡相关基因Bax和Bcl-2表达的影响。方法Wistar大鼠60只随机分为低剂量(0.1mT)、高剂量(12.8mT)电磁场暴露组及对照组,每组20只,分别有1