Tectonic and climate driven fluctuations in the stratigraphic base level of a Cenozoic continental coal basin, northwestern Andes

Changes in the sedimentologic and stratigraphic characteristics of the coal-bearing middle Oligocene–late Miocene siliciclastic Amagá Formation, northwestern Colombia, reflect major fluctuations in the stratigraphic base level within the Amagá Basin, which paralleled three major stages of evolution of the middle Cenozoic Andean Orogeny. These stages, which are also traceable by the changes in the compositional modes of sandstones, controlled the occurrence of important coal deposits. The initial stage of evolution of the Amagá Basin was related to the initial uplift of the Central Cordillera of Colombia around 25 Ma, which promoted moderate subsidence rates and high rates of sediment supply into the basin. This allowed the development of aggradational braided rivers and widespread channel amalgamation resulting in poor preservation of both, low energy facies and geomorphic elements. The presence of poorly preserved Alfisols within the scarce flood plains and the absence of swamp deposits suggest arid climate during this stage. The compositional modes of sandstones suggest sediment supply from uplifted basement-cored blocks. The second stage of evolution was related to the late Oligocene eastward migration of the Pre-Andean tholeitic magmatic arc from the Western Cordillera towards the Cauca depression. This generated extensional movements along the Amagá Basin, enhancing the subsidence and increasing the accommodation space along the basin. As a result of the enhanced subsidence rates, meandering rivers developed, allowing the formation of extensive swamps deposits (currently coal beds). The excellent preservation of Entisols and Alfisols within the flood plain deposits suggests rapid channels migration and a humid climate during deposition. Moderate to highly mature channel sandstones support this contention, and point out the Central Cordillera of Colombia as the main source of sediment. Enhanced subsidence during this stage also prevented channels amalgamation and promoted both, high preservation of geomorphic elements and high diversity of sedimentary facies. This resulted in the most symmetric stratigraphic cycles of the entire Amagá Formation. The final stage of evolution of the Amagá Basin was related to the early stage of development of the late Miocene northwestern Andes tholeitic volcanism (from 10 to 8 Ma). The extensive thrusting and folding associated to this volcanism reduced the subsidence rates along the basin and thus the accommodation space. This permitted the development of highly aggradational braided rivers and promoted channels amalgamation. Little preservation of low energy facies, poor preservation of the geomorphic elements and a complete obliteration of important swamp deposits (coal beds) within the basin are reflected by the most asymmetric stratigraphic cycles of the whole formation. The presence of greenish/reddish flood plain deposits and Alfisols suggests a dry climate during this depositional stage. The presence of channel sandstones with high contents of volcanic rock fragments supports a dry climate, and suggests an incipient phase of the Combia tholeiitic magmatism present during deposition of the Amagá Formation. The subsequent eastward migration of the NW Andes magmatic arc (after 8 Ma) may have produced basin inversion and suppressed deposition along the Amagá Basin.     

线状要素移位的研究

制图综合常要求将地形图要素从其正确的图面位置偏移一点。本文就线状要素的移位问题进行讨论。首先提出移位场的概念,这对于由于移位所产生的“连锁反应”能较好地解决;然后,提出一种栅格探测——矢量计算方祛,加快移位计算的速度。     

控制网连接点坐标值粗差的可定位性研究

在原有测量控制网(称旧网)的基础上建立同级扩大网或低级加密网(称新网)时,新旧网之间的重合点(称连接点)坐标值粗差的检验是平差前的一个重要环节。本文将连接点坐标视为带协方差阵的观测值,采用数据探测法定位其粗差。借助于 Gauss-Markov模型下两个备选假设检验的理论,推导了连接点相关坐标观测值粗差可定位性基本公式,讨论了各类平面网中连接点坐标观测值粗差的可发现性和可区分性。     

地形图符号库的设计

地形图中符号可分为点状符号、面状符号和线状符号,不同比例尺的地形图,其符号的构造规律是一致的,只是符号的结构与尺寸不同。本文在于探索这些符号的构造规律,并进行有机组织。     

专题地图地理底图数据库的建立与管理

本地理底图数据库系统是一个小型的数据库系统,它具备了地图数据库的基本功能,适应同一底图服务多种专题图编制的要求,提供多种检索途径;运用大量的位操作,使得数据库结构具有动态性、灵活性。将频繁交换的数据纳入内存,加快了系统运进速度;通过多边形组织,可自行建立专题要素与底图要素的图形关系,建立区域间层次关系,减小数据采集工作量。     

Estimation of soil water content in watershed using artificial neural networks

Soil water content (SWC) is an important factor in transfer processes between soil and air, contributing to water and energy balances, and quantifying it remains a challenge. This study uses artificial neural networks (ANNs) to analyse spatial and temporal variation of SWC in a Brazilian watershed, based on climate information, soil physical properties and topographic variables. Thirty eight input variables were tested in 200 models. The outputs were compared with 650 gravimetric moisture measurements collected at 26 points (25 field studies). The results show that it is possible to estimate SWC efficiently (Nash-Sutcliffe statistic, NS = 0.77) using topographic data, soil physical properties and rainfall. If only climate information is considered, modelling is less efficient (NS = 0.28). Using many variables does not necessarily improve performance. Alternatively, SWC can be estimated by simplified models using rainfall and topographic maps information, although the performance is less good (NS = 0.65).     

Comparison of Extrapolation and Interpolation Methods for Estimating Daily Photosynthetically Active Radiation(PAR)——A Case Study of the Poyang Lake National Nature Reserve,China

Measurements of photosynthetically active radiation(PAR),which are indispensable for simulating plant growth and productivity,are generally very scarce.This study aimed to compare two extrapolation and one interpolation methods for estimating daily PAR reaching the earth surface within the Poyang Lake national nature reserve,China.The daily global solar radiation records at Nanchang meteorological station and daily sunshine duration measurements at nine meteorological stations around Poyang Lake were obtain...     

哈萨克斯坦东部斋桑盆地恐龙蛋壳化石与白垩系-古近系界线

在晚白垩世期间,哈萨克斯坦东部的斋桑盆地形成了一个湖盆,一直延续到现在。古斋桑湖中最老的沉积是Tayzhuzgen组,由厚达136m的泥岩、粉砂岩、页岩、石英砂岩、砾岩和淡水石灰岩红层组成。按照当地的地层名称,Tayzhuzgen组包括Manrak、Tayzhuzgen、Aulisbulak、Aktobe、Dysum bay和Kiin Kerish层。在斋桑湖以南的Tayzhuzgen河附近一个地点的Tayzhuzgen组下部,发现了恐龙蛋壳碎片,蛋壳至少包括有两个主要类型:圆形蛋类和长形蛋类。恐龙蛋壳指示了Tayzhuzgen组下部的时代为晚白垩世(可能是马斯特里赫特期)。在本组的较高层位,发现了晚?古新世的植物化石,因此斋桑盆地的白垩系-古近系界线在Tayzhuzgen组内部。在Tayzhuzgen组中,白垩纪与古新世化石层之间的地层间隔只有约50m,由此推测在Tayzhuzgen组内部可能存在一个或多个不整合,或是本组的中部为凝缩沉积,即在白垩系-古近系界线处的沉积速率非常缓慢。Tayzhuzgen组顶部有一个显著的不整合,那里中或晚始新世(Arshantan,Irdinmanhan或Egilian陆生哺乳动物"期")的地层存在于含哺乳动物化石剖面的底部。斋桑盆地的白垩系-古近系界线位于古斋桑湖沉积剖面的下部。这不是一个完整的界线剖面,可能是一个包含有一个或多个不整合和/或一个由慢速沉积造成的凝缩剖面。     

一种复杂海天背景下的红外舰船目标自动检测方法

提出了一种红外舰船目标检测算法。首先,利用设计好的频域组合高通滤波器对原始红外图像进行处理,以得到舰船目标可能存在的区域即目标潜在区;然后,对获得的目标潜在区进行尺度自适应的局部阈值分割,进而提取出较为完整的舰船目标或者虚假目标;最后通过检测吃水线特征来筛选出正确的舰船目标。实验结果表明,此算法能够有效地检测出复杂海天背景条件下的红外舰船目标,且具有一定的时效性。     

Virtual organisation in the SIMDAT meteorological activity: a decentralised access control mechanism for distributed data

The EU funded SIMDAT project is aimed at applying generic grid technology for the solution of complex application problems in several representative fields including automotive, aerospace, pharmaceutical and meteorology. To satisfy the requirements of the World Meteorological Organization (WMO) and the WMO Information Systems (WIS), the partners in the meteorology activity within SIMDAT (ECMWF, Deutscher Wetterdienst, the UK Met office, EUMETSAT and Météo-France), have developed grid-enabled software that provides generic distributed access to distributed meteorological data repositories via web-based portals, through a series of nodes organized in a mesh network. However, granting access to such an infrastructure, especially considering its fully distributed nature, is a serious challenge and a risk to the security of the overall grid infrastructure. SIMDAT solves this problem by implementing a security model based on a decentralized fine-grained access control mechanism that federates data providers and security issues using the notion of “trust domains”. In this paper we highlight the main features of the SIMDAT grid application and describe its security model in detail.