近4万年渤海西岸海侵时古海面的现代标高对比研究^*   总被引：2，自引：1，他引：1       下载免费PDF全文

魏灵  贾玉连  易朝路  王洪波  郭盛乔 《第四纪研究》2006,26(3):361-369

近4万年以来,相应于两次高太阳辐射暖湿期渤海西岸曾经两次海水泛陆事件,即40~28kaB.P.与10~4kaB.P.海侵事件。文章基于众多钻孔海相层中有孔虫、介形类等海相微体生物化石的组合特征恢复海水深度,重建了海侵最大时的古海面的现代标高。结果显示: 40~28kaB.P.海侵,海面的现代标高最高可达-11~-5m;10~4kaB.P.海侵则为2~3m。后者同众多研究所认为的中全新世存在高海面,海面高度为2~3m的结论大致吻合,前者则与全球气候尚处在间冰阶,冰川部分消融,世界洋面处在-50m的大背景不协调。而辽东与山东半岛沿海众多钻孔揭示,40~28kaB.P.渤海地区并没有高于-50~-20m海面存在的证据。通过区域环境的综合分析,认为40~28kaB.P.渤海西岸的海侵,是早玉木冰期持续4~5万年之久的冰期低海面环境,这种特殊的环境使现代渤海西岸的大部分区域远离沉积环境,成为冲刷侵蚀区,这种效应叠加在冰期边缘海式构造下沉与弧后盆地性质的构造下沉背景之上造成区域性异常地面低洼;渤海西岸异常地面低洼在间冰阶全球趋暖,冰川型海侵的过程中形成的区域性强烈"视"海侵(指示当时海侵时海水深度很大,而不是海水的陆泛范围大)。  相似文献   

Composition and assemblage characteristics of magnetic minerals in layer S<Subscript>5-1</Subscript> of Xifeng and Duanjiapo sections     

Jia?RongfenEmail author  Peng?Xianzhi  Zhou?Zheng  Liu?Dehan  Wang?Guanxin  Wang?Deqiang 《中国地球化学学报》2004,23(3):197-206

Relatively strongly magnetic fine components (< 30μm, XS-4J and DS-4J) which are most environmentally sensitive were separated from layer S_5-1 in the Xifeng and Duanjiapo loess sections and analyzed by MPV-3 for their morphometric characteristics and reflectance, SEM-ESD for their element contents and XRD for their mineral phases, respectively. The results showed that minerals in both samples are dominated by detrial Fe-Ti oxides of aeolian origin. In sample XS-4J the reflectance and iron contents of magnetic minerals are usually high. In addition to magnetite (Fe₃O₄), maghemite (γFe₂O₃) and hematite (Fe₂O₃), some Fe-high oxide (72.25 wt%–86.67 wt%), ilmenite (FeTiO₃), and magnetite-ulvöspinel [Fe(FeCr)O₄, Fe (FeNi)O₄] were also detected. In sample DS-4J obvious negative linear correlations were found between Ti and Fe, and the contents of Mn, Si, Al and Ca are usually high and the minerals are dominated by magnetite (maghemite), goethite (FeOOH) and limonite (containing Si and OH). In addition, the signs of corrosion of magnetic minerals and newly crystallized magnetite (maghemite) were recognized. Differences in the composition and assemblage characteristics of magnetite minerals between XS and DS reflect significant differences in source rocks and preserving conditions.  相似文献   

Geochronology and geochemistry of eclogites from the Mariánské Lázně Complex,Czech Republic: Implications for Variscan orogenesis     

Brian L. Beard  L. Gordon Medaris Jr  Clark M. Johnson  Emil Jelínek  J. Tonika  Lee R. Riciputi 《International Journal of Earth Sciences》1995,84(3):552-567

The Mariánské Lázn complex (MLC) is located in the Bohemian Massif along the north-western margin of the Teplá-Barrandian microplate and consists of metagabbro, amphibolite and eclogite, with subordinate amounts of serpentinite, felsic gneiss and calcsilicate rocks. The MLC is interpreted as a metaophiolite complex that marks the suture zone between the Saxothuringian rocks to the north-west and the Teplá-Barrandian microplate to the south-east. Sm-Nd geochronology of garnet-omphacite pairs from two eclogite samples yields ages of 377±7, and 367±4 Ma. Samples of eclogite and amphibolite do not define a whole rock Sm-Nd isochron, even though there is a large range in Sm/Nd ratio, implying that the suite of samples may not be cogenetic. Eclogites do not have correlated _Nd values and initial ⁸⁷Sr/⁸⁶Sr ratios. Five of the eight eclogite samples have high _Nd values (+10.2 to +7.1) consistent with derivation from a MORB-like source, but variable ⁸⁷Sr/⁸⁶Sr ratios (0.7033 to 0.7059) which probably reflect hydrothermal seawater alteration. Three other eclogite samples have lower _Nd values (+ 5.4 to –0.8) and widely variable ⁸⁷Sr/⁸⁶Sr ratios (0.7033 to 0.7096). Such low _Nd values are inconsistent with derivation from a MORB, source and may reflect a subduction or oceanic island basalt component in their source. The MLC is an important petrotectonic element in the Bohemian Massif, providing evidence for Cambro-Ordovician formation of oceanic crust and interaction with seawater, Late Devonian (Frasnian-Famennian) high- and medium-pressure metamorphism related to closure of a Saxothuringian ocean basin, Early Carboniferous (Viséan) thrusting of the Teplá terrane over Saxothuringian rocks and Late Viséan extension.  相似文献   

挡土结构古典内力计算方法的讨论     

郑刚  顾晓鲁 《岩土力学》1999,20(2):67-70

根据软土地区大量基坑支护的经验,对目前挡土结构古典内力计算常用的平衡法（悬臂结构）、等值梁法（单支撑结构）和弹性抗力法的计算结果进行了分析与比较,指出了古典内力计算方法的适用性。  相似文献   

磷矿中P2O5的快速测定   总被引：2，自引：0，他引：2  

刘兴利 《矿物岩石》1999,19(3):97-99

本文用自行设计的一种简易,安全的聚四氟乙烯溶样罐,与新型,高效的微波溶样技术相结合,进行磷矿的分解,溶样时间仅需２ｍｉｎ,并首次将该技术与流动注射一分光光度法联用,测定其中Ｐ２Ｏ２质量分数,结果准确,可靠,实现了从溶样到测定的一套快速分析方法。  相似文献   

怎样欣赏山水风光     

颜怀学  陈晓东 《安徽地质》1999,(3)

大自然造化的山水风光对人们具有极大的精神感召力, 而人们要欣赏自然风光的经常途径是旅游。因此, 山水风光已经成为发展国民经济的重要自然资源。旅游地学将地质学、地理学的理论与研究方法运用于旅游资源的调查与开发, 对发展国民经济有重要的理论和经济意义。欣赏山水风光首先要观察山水风光内在的成景因素, 同时也要探索山水与周围环境和社会环境的相互关系和相互作用。前者指山水的自然形态、线条、体积、数量、音响、色彩和动势以及植被; 后者主要指相适应的建筑, 有时还包括气象特征和人文特色。它们共同谓之风景的构成因素。  相似文献   

等温剩磁各向异性及其在磁倾角校正中的应用   总被引：4，自引：0，他引：4  

方大钧  沈忠悦  谈晓冬 《地球物理学报》2000,43(5):719-724

等温剩磁各向异性是一种新的磁组构研究方法 .与非滞后剩磁各向异性的参数一样 ,等温剩磁各向异性的参数直接与岩石中的携磁矿物颗粒形状有关 ,它直接反映了岩石形成与压实作用下携磁矿物的变形和变位 .利用等温剩磁各向异性技术 ,有可能对磁倾角偏低进行有效的校正 .本文介绍了等温剩磁各向异性及其在磁倾角校正中的应用 ,并以塔里木盆地库车拗陷的苏维依组红色砂岩的实验为实例 ,获得磁倾角校正值 ,与理想的欧亚板块磁倾角值十分吻合  相似文献   

冬季黔北境内云贵准静止锋影响下最高气温预报订正方法研究          下载免费PDF全文

罗晨艺 《中低纬山地气象》2023,47(5):52-56

本文为探索静止锋位于遵义上空不同位置时,各城镇精细化预报考核站点当日高温的规律,通过普查2009至2020年12月到次年2月间14时、17时地面天气图,并结合探空资料、卫星云图等资料,筛选出云贵准静止锋（以下简称为静止锋）位于遵义境内时的所有个例,分型统计不同类型个例对应的白天最高温、EC2m温度预报数据,EC细网格850hPa温度,计算不同温度预报方法下的准确率,并分析是否可继续订正。结果表明：（1）离锋面越远,温度的预报准确率越高,基于客观预报方法的可订正性越强,实际业务中可以参考本文分析得到的各站点数据。（2）当静止锋呈Ⅰ1型时,遵义市西部站点用EC预报当日20时的850hPa温度进行预报（以下简称850hPa温度预报方法）准确率较高,北部、东部站点可用EC2m最高温度进行订正（以下简称2m温度订正方法）。（3）当静止锋呈Ⅰ2型时,可以同时参考850hPa温度预报方法和2m温度订正方法,订正后准确率高。（4）当静止锋为Ⅱ2型时,对于离锋面较远的东部、南部可着重使用2m温度订正方法。  相似文献   

流速仪信号采集系统设计   总被引：1，自引：1，他引：0       下载免费PDF全文

金福一 《水文》2016,36(1):88-91

介绍了流速仪检定系统的工作原理,分析流速仪信号特点和采集难点,针对流速仪信号受外界干扰信号波形复杂问题,设计信号采集硬件调理电路。针对流速仪信号周期多样性问题,对测频法和测周法进行误差分析和比较,确定在不同速度区间使用不同软件滤波的方法。通过硬件调理电路及软件滤波仿真验证,证明设计的可行性,可有效提高流速仪信号采集的精度,并在单片机平台上完成了硬件设计。  相似文献   

‘I want to take risks,like my mother’: Memory,affect, and Vietnamese masculinities – the legacy of gendered variations in socio-economic mobility during Ðổi mới     

Philip Martin 《Norsk geografisk tidsskrift. Norwegian journal of geography》2013,67(4):210-218

Young Vietnamese men who witnessed their mother's changing economic and labour market situations through the early years of Ð?i m?i (the policy of economic liberalization in Vietnam after 1986) have developed conceptions of masculinity that are ambivalent to notions of male power and authority within what is often termed the ‘traditional’ neo-Confucian family. On the basis of the life narratives of a small group of men in their early twenties, the author suggests that the value young men place on their mother's work and familial influence during Ð?i m?i contrasts with the findings of much gender scholarship on women's social and economic (im) mobility in the 1990s in Vietnam and on young men's own masculinist narratives. Most gender-sensitive research in this area has suggested that Vietnamese women remained curtailed in the early 1990s by a resurgence of male-oriented kinship systems and patriarchal structures at household level. However, the author discusses the young men as being equivocal. While invoking broad Confucian tropes, these men remember their mothers as economically dynamic relative to their fathers. This led to the informants citing their mother's histories of economic risk-taking as exemplifying free-market capability. Further, the finding suggests that Vietnamese women's social and economic mobility in the 1990s strongly affected young men's contemporary ideas and practices related to masculinity.  相似文献