An Early Cretaceous extinct spreading center in the northern Natal valley

We have identified an extinct E–W spreading center in the northern Natal valley on the basis of magnetic anomalies which was active from chron M11 (133 Ma) to 125.3 Ma, just before chron M2 (124 Ma) in the Early Cretaceous. Seafloor spreading in the northern Natal valley accounts for approximately 170 km of north–south motion between the Mozambique Ridge and Africa. This extension resolves the predicted overlap of the continental (central and southern) Mozambique Ridge and Antarctica in the chron M2 to M11 reconstructions from Mesozoic finite rotation parameters for Africa and Antarctica. In addition, the magnetic data reveal that the Mozambique Ridge was an independent microplate from at least 133 to 125 Ma. The northern Natal valley extinct spreading center connects to the spreading center separating the Mozambique Basin and the Riiser-Larsen Sea to the east. It follows that the northern Mozambique Ridge was either formed after the emplacement of the surrounding oceanic crust or it is the product of a very robust spreading center. To the west the extinct spreading center connects to the spreading center separating the southern Natal valley and Georgia Basin via a transform fault. Prior to chron M11, there is still a problem with the overlap of Mozambique Ridge if it is assumed to be fixed with respect to either the African or Antarctic plates. Some of the overlap can be accounted for by Jurassic deformation of the Mozambique Ridge, Mozambique Basin, and Dronning Maud land. It appears though that the Mozambique Ridge was an independent microplate from the breakup of Gondwana, 160 Ma, until it became part of the African plate, 125 Ma.     

在"数字国土工程"中我区地学数据库建设的现状及发展趋势

近年来,在国土资源部的高度重视下,我区相继建立了一系列地学数据库。这些地学数据库的建立不仅为地矿行业提供了基础性数据,也加速了"数字国土工程"和国土资源信息化建设的步伐。随着信息技术的高速发展,利用地理信息系统(GIS)将各类地学数据有机地结合起来,形成地学数据应用与管理系统,最终通过网络服务于社会,必将是各类地学数据发展的必然趋势。     

A method to predict the group fissuring and faulting caused by regional groundwater decline

Ground fissuring is a recurrent problem in many countries where water extraction surpasses the natural recharge of aquifers. Due to differential settlement, the soil layer undergoes deformation and cracks with serious consequences for civil infrastructure. Here, we propose an approximate analysis of the fissuring process that can be used to predict the location of cracks, which increasingly affect some middle- and large-sized cities in the world. For that purpose, the ground loss theory is applied to sediments overlying a sinusoidal-shaped graben. This analysis shows the existence of a tensile zone at the border of the graben with maximal values on its shoulder where tension cracks are more likely to appear. It also shows that soil deformation under differential settlement may evolve into ground faulting if water withdrawal continues. Finally, when a crack has completely developed, the tensile zone shifts towards the center of the graben, creating a new area for potential cracking and faulting.     

有限元分析方法在黄土地基震陷预测中的应用

将有限元方法应用于黄土地基的震陷量预测，定量地研究了黄土地基地震沉陷特性与场地条件、基础形式、土动力特性等因素的相关关系，为黄土地基基础的抗震增稳设计与处理提供了科学依据。     

中国耕地有机质含量变化对土地生产力影响的定量研究

在土地持续利用与管理研究中，土地质量变化对土地生产力影响的定量研究是核心内容之一。借助新古典经济学的生产函数法，构建了我国耕地的生产函数模型，定量模拟了我国耕地有机质含量变化的边际产出率性和边际生产力。初步结果表明，由于我国长期存在耕过度利用导致有机质含量及肥力下降问题，当前提高耕地质量的增产潜力十分可观。     

社会主义市场经济条件下的土地储备及其模式选择

社会主义市场经济建设的逐步完善，要求我们必须改变传统的土地管理思路，土地储备作为政府经营城市的一种重要手段，能够使政府在土地管理的实践中实现资源与资产并重的目标。在阐述土地储备的涵义、起源及其在我国的产生与发展的基础上，分析了土地储备的运行机制与最终目标，归纳了我国土地储备的基本做法，首次提出了城市土地储备的直接储备模式和间接土地储备模式概念，并提出了地方政府构建城市土地储备模式的基本原则和具体操作思路。     

城市群演化的空间过程及土地利用优化配置

城市群演化包含了诸多内容 ,如人口、产业、城市类型、城市职能等 ,而空间过程是最直接、最综合的表现。     

21世纪黄河系统工程方略

该文指出 :王化云的治黄思想 ,“上拦下排、两岸分滞、蓄水拦沙、宽河固堤、除害兴利、综合利用” ,实际上是治理黄河的系统工程 ,2 1世纪应该继承和发展黄河系统工程的方略。黄河地处中国腹地 ,是中华民族的摇篮 ,当今高新科技的发展 ,足以从更大的范围 ,以全国的水资源、土资源为核心来考虑黄河的建设。统一计算水资源中的大气水、地表水、地下水、壤中水、生态水、环境水、生产水、生活水 ;统一计算土资源中的土壤资源、沙资源、沙石资源 ,真正按照地理系统工程来建设黄河。     

宁夏回族自治区土地沙漠化研究

该文分析土地沙漠化的形成是不合理的人类经济活动和恶劣的自然环境相互作用的结果。人类不仅是促进土地沙漠化发生发展的主要动因 ,同时也是沙漠化的受害者。只有采取合理的符合生态原则的治理活动 ,诸如一系列政策保护与技术防治相结合的措施 ,才能实现土地沙漠化逆转     

分布式侵蚀预报模型中网格面积的选定——以黄土高原丘陵沟壑区为例

在分布式土壤侵蚀过程模型中 ,承载数据以及进行运算的最小单元 ,即基本地块的选取是非常关键的 ,它直接关系到模型的模拟精度和运算数据量。目前大多数分布式模型都采用平均布设矩形网格的方法 ,这种方法在基本网格的大小选取上存在着盲目性和不统一性。本文以黄土高原丘陵沟壑区为例 ,利用GIS和SPSS分析了黄土高原丘陵沟壑区属性均一的基本地块在面积上的统计规律 ,给出了基本地块选取的合理依据 ,以促进建立更好的分布式模型