浙江缙云县大洋山石鼓尖花岗岩坑穴成因   总被引：3，自引：0，他引：3  

朱诚  崔之久  李中轩  高洁  王立新  邬祥林  郑朝贵  沈庆凡  郑献章 《地理学报》2008,63(7):735-743

浙江缙云县大洋山石鼓尖海拔1477m,在其山顶花岗岩表面发现大量直径几十厘米至1m左右、深度10cm至45cm的坑穴。经对60处坑穴的形态量测发现,坑穴主要发育在山坡的NE和SE一侧;坑穴积水后出水口流向亦主要朝向NE和SE。对岩石标本的偏光显微镜和X荧光光谱鉴定分析发现,该处基岩为易风化、泥化明显的中细粒钾长花岗岩。该处年平均气温9.2oC,年降水量在1700mm以上,每年12月至翌年3月会经历4个月日气温在0oC上下波动的冰缘作用期,雨雪水冻融交替对基岩的崩解作用明显。该处位于夏季台风雨迎风坡（NE和SE坡）一侧,暴雨常伴随有10级以上大风。现场常可见风力吹蚀带动坑穴中细岩屑对坑穴内壁产生加速旋转磨蚀作用。上述研究表明,该处花岗岩坑穴形成的主要动力成因首先是冰缘寒冻风化作用,暴雨和山顶大风的风力吹蚀加速了坑穴的形成。观察表明,此种作用目前仍在进行之中,风向的转变是造成坑穴出现多种形态的主要原因。由于此处海拔距雪线尚有1500m高差,即使在第四纪盛冰期也仅是接近雪线高度,且因山顶无积雪屯冰的低洼地形,因此,第四纪“冰臼”成因说难以成立。  相似文献   

Reconstruction of the climate in the Tianmu Mountain area,Zhejiang Province,in the last 160 years by σ<Superscript>13</Superscript>C sequence of tree ring α-cellulose     

Junlong?QianEmail author  Jun?Lü  Qipu?Tu  Wang?Sumin 《中国科学D辑(英文版)》2002,45(5):409-419

Based on cross-dating tree rings from the Tianmu Mountain, Zhejiang Province, the tree rings α-cellulose σ¹³C time series was measured. By spectrum analysis, the variation of tree-ring σ¹³C sequence shows a quasi periodicity of 4.4 years, which is coincident with the standard cycle of El Niño. After removing the long-term decrease trend of the σ¹³C variation related to atmospheric CO₂ concentration, the response of the σ¹³C to climate elements was analyzed using meteorology data from a nearby weather station. The results suggest that there is a distinct relativity between high-frequency variation of tree ring σ¹³C series and seasonal climate parameters, e.g. temperature and precipitation, with a significant time-lag effect. In addition, the high frequency also reflects the strength change of the East Asian Monsoon. The multiple regression method was employed to reconstruct the historical climate, and to analyze the climate change and trend in the last 160 years in the northern Zhejiang Province.  相似文献   

Modelling of differential single difference receiver clock bias for precise positioning   总被引：3，自引：0，他引：3  

Xianglin?LiuEmail author  Christian?Tiberius  Kees?de Jong 《GPS Solutions》2004,7(4):209-221

A receiver hardware delay should be seriously considered for time-transfer and determination of ionospheric delay corrections for wide area differential GPS positioning. A receiver hardware delay does not generally effect the common geo-position application, as suitable differences of observations are used, or equivalently, clock error parameters are introduced, epoch-wise, that also absorb the delays. This paper investigates the behavior of inter-frequency (or observation-type) receiver hardware delays by using a single difference (SD) model, which estimates the receiver delay along with the receiver clock error (and SD ambiguities of a reference satellite with carrier phase observations) for zero and short baselines. The purpose of this paper is to model the between-observation-type delays for the purpose of precise positioning, under practical circumstances. The focus is on data series of differential SD receiver clock biases, since they reflect the behavior of receiver hardware delays with time. A simple linear regression of the data series is employed to study the behavior, and test statistics are employed to assess both the significance of the parameters and the observations fit for the linear regression. The statistical analysis results indicate that almost all inter-observation type receiver delays can be modeled as the sum of a constant (offset) and a constant rate of change (slope). The analysis shows that the differential receiver delay is generally at the mm- to cm-level on phase, while at the dm-level on code for the equipment used in the experiments.  相似文献   

湖北经济的空间结构及发展布局模式     

涂人猛 《云南地理环境研究》1991,3(2):55-63

本文论述了区域空间结构的构成要素和形成基础,分析了湖北省经济空间结构的现状、特征,并提出了其经济空间结构发展的模式。  相似文献   

高空探测资料气球漂移的计算方法   总被引：1，自引：0，他引：1       下载免费PDF全文

李伟 王志文谢庄  刘凤琴徐磊 涂满红 《应用气象学报》2005,16(6):835-840

随着数值模式的不断发展，探空气球的漂移偏差越来越不可忽视。为了提高高空观测数据的质量，减小在探测过程中由于气球漂移造成探测资料在空间上的误差，中国气象局提出一套探空、测风报的空间、时间扩充编码方案。该文从探空雷达探测系统、探测原理分析出发，介绍了该方案计算方法，并用个例说明方案的使用方法及业务应用前景。  相似文献   

Limited Consequences of Seagrass Decline on Benthic Macrofauna and Associated Biotic Indicators     

V. Tu Do  Hugues Blanchet  Xavier de Montaudouin  Nicolas Lavesque 《Estuaries and Coasts》2013,36(4):795-807

Marine phanerogams are ecosystem engineers, as their presence induces major environmental changes that impact on the benthic fauna. Consequently, modifications to the structure of benthic communities would be expected to be associated with seagrass decline. Since 2005, Zostera noltii seagrass beds in Arcachon Bay (France), the largest in Europe, have undergone a severe decline. Twelve stations distributed throughout the lagoon were sampled in 2002, and all were found to be densely planted at that time. Subsequently, the same stations were revisited in 2010 and seagrass cover had drastically decreased by that time. Based on benthic macrofauna, multidimensional scaling (MDS) analysis identified four groups. Years were separated. In 2002, two groups were distinct in relation to the water body, since in 2010 separation between the two other groups was related to seagrass occurrence. When looking at community structure and dominant species there were moderate differences within and between years, independent of seagrass decline. Seagrass loss did not drastically modify the species composition as they were preserved in the remaining seagrass patches. However, there was a drop in macrofauna abundance in unvegetated muddy compared with abundance in the remaining seagrass areas. Epifauna was particularly affected by seagrass decline. Among biotic indicators based on macrofauna, multivariate indicator MISS (Macrobenthic Index in Sheltered Systems) was in agreement with the similarity of macrofauna structure among groups, while other tested indicators performed badly in relation to seagrass occurrence. However, no index detected seagrass loss, highlighting the necessity of maintaining a separate survey on seagrass cover.  相似文献   

勘探早—中期的沉积盆地有效烃源岩综合预测方法探讨——以北黄海某盆地为例     

冯常茂  白志琳  涂广红  王后金  胡小强  杜民 《海相油气地质》2013,(2):65-71

针对勘探程度较低的地区,提出了一套有效烃源岩的综合预测方法。其基本思路是,从钻井出发,井震结合,按由点到面、由剖面到平面的顺序分五步进行:确定有利沉积相带;确定烃源岩平面分布;划分区域沉积相分布;确定平面热演化分布;有效烃源岩分布预测。利用该方法,对北黄海某盆地侏罗系SQ1层序进行了有效烃源岩预测。  相似文献   

基于优化背景值的MGM(1,m)模型在建筑物沉降监测中的应用     

程方  徐泮林  郭祥琳 《北京测绘》2018,32(1):70-74

根据MGM(1,m)模型的基本建模原理,发现了模型背景值的构造形式对模型精度存在影响,从传统MGM(1,m)模型背景值构造形式的角度对其进行改造,重新构建灰色MGM(1,m)模型背景值。通过实例分析,改进后的灰色MGM(1,m)模型相较传统的MGM(1,m)模型,在精度方面有了很大的提高。  相似文献   

粤西北印支期太保岩体的锆石U-Pb年代学、地球化学及岩石成因          下载免费PDF全文

李响  王令占  涂兵  田洋  谢国刚  张楗钰  张宗言 《地球科学》2021,46(4):1199-1216

华南早中生代构造-岩浆演化还存在不同的争议.以广东西北部连山地区晚三叠世含暗色微粒包体(MMEs)的太保岩体为研究对象,进行了岩石学、锆石U-Pb年代学、地球化学和Sr-Nd-Hf同位素组成研究.4个花岗岩样品的锆石206Pb/238U加权平均年龄分别为219.8±1.8 Ma、220.5±1.0 Ma、221.5±1.7 Ma和220.2±1.1 Ma,为印支晚期岩浆作用的产物.地球化学分析显示,寄主花岗岩为高钾钙碱性花岗岩,低硅、高碱,铝饱和指数A/CNK值为0.79~1.16.包体SiO₂含量为55.13%~62.56%,铁、镁含量明显高于寄主花岗岩,MgO和FeOT含量分别为2.31%~4.60%和5.53%~6.63%.包体与寄主花岗岩均富集轻稀土,并表现出显著的Ba、Sr、Ti负异常.寄主花岗岩和包体均具有较高的ε_Nd(t)值(-3.42~-2.60和-0.90~-0.52)和较小的二阶段Nd模式年龄(T_DM2分别为1.30~1.35 Ga、1.10~1.13 Ga).寄主花岗岩具有较宽泛的ε_Hf(t)值(-2.6~+4.3,平均值为+0.7)和两阶段Hf模式年龄(0.95~1.39 Ga)变化范围,指示太保岩体形成于中元古代下地壳变基性岩物质的熔融,并与亏损地幔物质发生岩浆混合作用.基于以上数据,笔者认为太保岩体是印支晚期伸展条件下亏损地幔和下地壳物质混合的产物.结合近年来报道的邻近区域的基性岩浆活动,认为华南古特提斯构造域向古太平洋构造域的转换可能开始于晚三叠世(233 Ma).   相似文献   

四川垭紫罗裂陷槽西北缘（黔水地1井）发现上古生界海相页岩气          下载免费PDF全文

陈相霖  苑坤  林拓  金春爽  康海霞 《中国地质》2021,48(2):661-662

正1研究目的(Objective)目前志留系龙马溪组页岩气在四川盆地已基本实现商业开发,寒武系、震旦系和二叠纪等页岩层系也相继取得重要突破,而中国南方石炭纪地层尽管同样被认为是一套重要页岩层系,但至今仍未取得实质性突破。"垭都—紫云—罗甸"裂陷槽为一个从泥盆系开始发育的狭长海槽,裂陷槽中心内发育石炭系打屋坝组富有机质页岩,具有页岩沉积厚度大、有机质丰度高、热演化成熟度适中等特点,有较大勘探潜力。因此,为进一步探索石炭系打屋坝组页岩气形成地质条件及含气性,在裂陷槽西北缘的威水背斜部署实施了黔水地1井。  相似文献