Provenance and tectonic setting transition as recorded in the Neoproterozoic strata,western Jiangnan Orogen:Implications for South China within Rodinia     

Jiawei Zhang  Taiping Ye  Yaran Dai  Jianshu Chen  Hui Zhang  Chuangu Dai  Guohua Yuan  Kaiyuan Jiang 《地学前缘(英文版)》2019,10(5):1823-1839

The Neoproterozoic Tonian strata(ca.870-725 Ma)in the western Jiangnan Orogen archive the records of sedimentary provenance and tectonic setting which can be used to understand the geological evolution of the South China Continent.These strata are separated into the basement and cover sequences by a regional angular unconformity.The basement sequence can be subdivided into the lower and the upper parts by the widespread interbedded ca.840 Ma basalt with pillow structure.In the present work,234 concordant detrital zircon analyses are obtained from three Tonian sandstone samples in the Fanjingshan district,Guizhou Province.Combined with previous results,a total of 1736 analyses of detrital zircon U-Pb ages derived from 12 formations of Tonian strata in the western Jiangnan Orogen are used to decipher the integrated sedimentary and tectonic histories.The zircons from the lowermost part of the basement sequence(the Yujiagou Formation)show oval morphology and display two Paleoproterozoic age peaks at 2325 Ma and 1845 Ma which are similar with the detrital zircon age peaks from the Late Paleoproterozoic to Early Mesoproterozoic Dongchuan/Dahongshan/Hekou groups,suggesting a passive margin basin in which the sediments were mainly sourced from the southwestern Yangtze Block.However,the zircon age population of the lower part of the basement sequence(the Xiaojiahe,Huixiangping formations and their equivalents)indicates the sedimentary derivation from bidirectional sources(the ca.870 Ma arc materials in the south and the old detritus from the southwestern Yangtze Block)which is consistent with a back arc setting for the deposition of the sediments.Zircons from the upper part of the basement sequence(the Duyantang Formation and its equivalent)show euhedral and subangular morphology and display a unimodal age peak at ca.835 Ma.This sequence was possibly deposited in a convergent setting and the detritus were came from the locally distributed syn-collisional igneous rocks.The lower part of the cover sequence(the Xinzhai and Wuye formations and their equivalents)shows a distinct zircon age peak at 815—809 Ma and two subordinate peaks at 2485 Ma and 2018 Ma,suggesting that the basin had gradually transformed into a continental rift basin and received the detritus from the ca.815 Ma post-collisional magmatic rocks as well as from different Paleoproterozoic source rocks in the northern Yangtze Block.We propose a tectonic evolution model that envisages eruption of ca.840 Ma basalt in a back arc basin that existed during ca.870-835 Ma,an angular unconformity was formed during amalgamation of the Yangtze Block and the Cathaysia Block at ca.835-820 Ma and the rifting of the South China Continent was initiated at ca.800 Ma.Our study concludes that the South China Continent was formed on the periphery of the Rodinia supercontinent.  相似文献   

FAH方法与气体敏化方法的对比     

姚保安  经嘉云  徐宗海  童建华 《中国天文和天体物理学报》1987,(2)

我们使用上海天文台的敏化实验室,用同一批号的同盒底片,对比研究了气体敏化方法和BAH方法对几种常用柯达天文底片的效果。结果表明,BAH方法虽然不象原提出者所说的那样理想,但它不失为一种简便易行的好方法。 我们还研究了把气体敏化方法和FAH方法结合的问题。看来,对于某些品种底片,结合是有希望的。  相似文献   

Geometric assessment of the kodak DCS Pro back     

Jon P. Mills  Danilo Schneider  David M. Barber  Paul G. Bryan 《The Photogrammetric Record》2003,18(103):193-208

This paper reports on an investigation into the suitability of the Kodak DCS Pro Back for use in close range photogrammetric measurement. The camera back, being used in conjunction with a medium-format non-metric camera, has been assessed with a view to using it for low- to medium-order photogrammetric work in architectural recording. Examinations centred upon the stability of the camera back with respect to the camera body and the effects of the removable infrared filter that is present immediately above the camera's focal plane. Ultimately the camera combination was deemed suitable for application in recording of this kind and is now in active use by the Metric Survey Team at English Heritage.  相似文献   

Assessment of a coastal landslide subjected to building loads at Sinop, Black Sea region, Turkey, and stabilization measures   总被引：1，自引：0，他引：1  

《Engineering Geology》2004,75(1):69-88

The large landslides along the Black Sea shore in Turkey are well-known instability phenomena and responsible for considerable economic losses each year. The severity of the problem increased particularly in recent years as increased scarcity of land forced utilization of inherently unstable areas. In 1988, severe rainstorms at the city of Sinop on the Black Sea shore triggered ground movements on a gentle coastal slope subjected to building loads and caused extensive damage to buildings founded on the slope. Comprehensive investigations of the failure were carried out and used to establish a geotechnical model for the slide. The model allowed consideration of building loads and different groundwater conditions. In addition, the model studies were complimented by limit-equilibrium and finite-element stress analyses. The results indicated movements on a circular sliding surface through stiff clay. The toe of the landslide is located at the shoreline and remains active. The failure was probably initiated by rising groundwater level combined with surcharge loads imposed by buildings on the slope. Other contributing factors include sand extraction and coastal erosion. Remedial works are recommended involving a rockfill buttress at the toe of the slide and drainage improvements on the surface of the slope.  相似文献   

Concentration and gas/particle partitioning of polychlorinated biphenyls (PCBs) at an industrial site at Bursa, Turkey   总被引：1，自引：0，他引：1  

S. S&#x;dd&#x;k Cindoruk  Fatma Esen  Yücel Tasdemir 《Atmospheric Research》2007,85(3-4):338-350

Gas and particle phase concentrations of atmospheric polychlorinated biphenyls (PCBs) were measured at an urban/industrial site in the city of Bursa, Turkey. PCB concentration levels were presented between July 2004 and May 2005. Average particle and gas phase concentrations of individual PCB congeners ranged from 0.08 (PCB-183) to 6.86 (PCB-49) pg m^− 3 and from 0.01 (PCB-209) to 47.2 (PCB-33) pg m^− 3, respectively. The mean concentration of total (gas + particle) PCBs varied between 24.27 and 666.21 pg m^− 3 with an average of 287.27 ± 174.80 pg m^− 3. PCB concentrations at the sampling site were higher than the concentrations reported at non-urban sites. PCBs partitioned between gas and particle phases and the partitioning was examined according to different approaches such as logK_p–logP_L^o, logK_p–logK_OA and the Junge–Pankow model. In order to present possible interactions, a correlation matrix based on PCB congeners and meteorological parameters was constructed. Application of the Clausius–Clapeyron equation yielded a low slope value indicating possible emissions from local and regional sources originating mainly from urban/industrial areas, landfill and waste incineration plant. Then, likely dry deposition fluxes were estimated depending on reported dry deposition velocity and atmospheric concentration values.  相似文献   

神经网络计算机及其在遥感应用中的展望     

谈正 《遥感学报》1991,(3)

本文概述了神经网络计算机的基本特点、神经网络的形式化描述、目前国际上神经网络计算机的现况以及在遥感图像处理中应用的潜力和展望。  相似文献   

TerraExplorer Pro和ArcGIS Engine三维GIS系统设计与实现     

王昌翰 《测绘科学》2010,35(5)

TeaExplorer Pro是功能强大的三维地理信息平台,其特点是以三维的形式集成与管理多数据源空间数据,并具有三维空间分析功能,ArcGIS是目前开发二维地理信息系统的主流平台,本文提出了将二者有机结合,利用TerraExplorer Pro和ArcGIS Engine组件构建三维GIS系统的原理和方法。  相似文献   

Prediction of daily sediment discharge using a back propagation neural network training algorithm: A case study of the Narmada River,India     

Nibedita Bisoyi  Harish Gupta  Narayan Prasad Padhy  Govind Joseph Chakrapani 《国际泥沙研究》2019,34(2):125-135

Most of the studies on Artificial Neural Network (ANN) models remain restricted to smaller rivers and catchments. In this paper, an attempt has been made to correlate variability of sediment loads with rainfall and runoff through the application of the Back Propagation Neural Network (BPNN) algorithm for a large tropical river. The algorithm and simulation are done through MATLAB environment. The methodology comprised of a collection of data on rainfall, water discharge, and sediment discharge for the Narmada River at various locations (along with time variables) and application to develop a threelayer BPNN model for the prediction of sediment discharges. For training and validation purposes a set of 549 data points for the monsoon (16 June-15 November) period of three consecutive years (1996–1998) was used. For testing purposes, the BPNN model was further trained using a set of 732 data points of monsoon season of four years (2006–07 to 2009–10) at nine stations. The model was tested by predicting daily sediment load for the monsoon season of the year 2010–11. To evaluate the performance of the BPNN model, errors were calculated by comparing the actual and predicted loads. The validation and testing results obtained at all these locations are tabulated and discussed. Results obtained from the model application are robust and encouraging not only for the sub-basins but also for the entire basin. These results suggest that the proposed model is capable of predicting the daily sediment load even at downstream locations, which show nonlinearity in the transportation process. Overall, the proposed model with further training might be useful in the prediction of sediment discharges for large river basins.  相似文献   

基于模糊神经网络(FNN)的赤潮预警预测研究   总被引：6，自引：0，他引：6  

王洪礼  葛根  李悦雷 《海洋通报》2006,25(4):36-41

为研究各种理化因子与赤潮藻类浓度间的非线性对应规律和有效预测赤潮藻类浓度,构建了基于BP算法的一个四层模糊神经网络模型。将模糊神经网络(FNN)技术引入赤潮预测研究,并与普通BP网络、RBF网络的结果作比较,结果表明,该模型能够较好地反演出各种理化因子与夜光藻密度的非线性对应变化规律,有更好的预测功能。  相似文献   

CT机和核磁共振成像(MRI)机之间的比较研究   总被引：5，自引：1，他引：4  

吉永星  俎栋林 《CT理论与应用研究》2000,9(3):1-8

ＣＴ和ＭＲＩ是当今应用最普遍的两大类临床影像诊断设备。本文应邀就普遍关心的问题对ＣＴ和ＭＲＩ两大设备在原理、性能、指标、功能、参数、敏感性、安全性、信号性质、图像标准、图像重建的方法学理论等诸多方面进行了有益和有意义的比较。并沿两类机器发展的轨迹追溯了两种影像在历史上的交汇点（源宗）。阐明了两套数学方法（Ｒａｄｏｎ变换和Ｆｏｕｒｉｅｒ变换）的平行发展根源于其信号性质的重大区别。ＭＲ是时域信号,而Ｘ  相似文献