Estimating the potential for submergence for two wetlands in the Mississippi River Delta

We used a combined field and modeling approach to estimate the potential for submergence for one rapidly deteriorating (Bayou Chitigue Marsh) and one apparently stable (Old Oyster Bayou Marsh) saltmarsh wetland in coastal Louisiana, given two eustatic sea level rise scenarios: the current rate (0.15 cm year⁻¹); and the central value predicted by the Intergovernmental Panel on Climate Change (48 cm by the year 2100). We also used the model to determine what processes were most critical for maintaining and influencing salt marsh elevation including, mineral matter deposition, organic matter production, shallow subsidence (organic matter decomposition + primary sediment compaction), deep subsidence, and sediment pulsing events (e.g., hurricanes). Eight years of field measurements from feldspar marker horizons and surface elevation tables revealed that the rates of vertical accretion at the Bayou Chitigue Marsh were high (2.26 (0.09) cm yr⁻¹ (mean ± SE)) because the marsh exists at the lower end of the tidal range. The rate of shallow subsidence was also high (2.04 (0.1) cm yr⁻¹), resulting in little net elevation gain (0.22 (0.06) cm yr⁻¹). In contrast, vertical accretion at the Old Oyster Bayou Marsh, which is 10 cm higher in elevation, was 0.48 (0.09) cm yr⁻¹. However, there was a net elevation gain of 0.36 (0.08) cm yr⁻¹ because there was no significant shallow subsidence. When these rates of elevation gain were compared to rates of relative sea level rise (deep subsidence plus eustatic sea level rise), both sites showed a net elevation deficit although the Bayou Chitigue site was subsiding at approximately twice the rate of the Old Oyster Bayou site (1.1 cm yr⁻¹ versus 0.49 cm yr⁻¹ respectively). These field data were used to modify, initialize, and calibrate a previously published wetland soil development model that simulates primary production and mineral matter deposition as, feedback functions of elevation. Sensitivity analyses revealed that wetland elevation was most sensitive to changes in the rates of deep subsidence, a model forcing function that is difficult to measure in the field and for which estimates in the literature vary widely. The model also revealed that, given both the current rate of sea level rise and the central value estimate, surface elevation at both sites would fall below mean sea level over the next 100 years. Although these results were in agreement with the field study, they contradicted long term observations that the Old Oyster Bayou site has been in equilibrium with sea level for at least the past 50 years. Further simulations showed that the elevation at the Old Oyster Bayou site could keep pace with current rates of sea level rise if either a lower rate for deep subsidence was used as a forcing function, or if a periodic sediment pulsing function (e.g., from hurricanes) was programmed into the model.     

A Model for the polar motion of the deformable Earth adequate for astrometric data

Refined analytical expressions for the frequencies corresponding to the Chandler motion of the pole and the diurnal rotation of the deformable Earth are derived. Numerical estimates of the period and amplitude of the polar oscillations are presented. The trajectory of the Chandler polar motion derived via numerical modeling is in qualitative and quantitative agreement with experimental data from the International Earth Rotation Service (IERS). An evolutionary model describing slow variations in the Earth’s rotation parameters under the action of the dissipative moments of the tidal gravitational forces on time scales considerably longer than the precession period of the Earth’s axis is constructed. The axis of the Earth’s figure tends to approach the angular momentum vector of the proper rotation.     

Computerized vision for the geologist

The digital computer can be a tireless friend and assistant to the geologist. The computer has no innate intelligence, but given adequate programs to analyze and interrelate the information on maps, photos, surveys, and other material, the computer can serve as an analytical tool and consultant. To the geologist's qualitative knowledge, theories, and models can be added the possibility of the computer's mathematically precise numerical answers, confirming or refuting the original ideas. In the interactive mode in particular, a dialogue between the geologist and the computer is established, where the geologist and the computer can complement each other's abilities. The basic principles of processing two-dimensional geological data, such as maps, charts, photos, and survey results, are discussed. Some comparisons are also made between the rule-based methods of Prospector, developed at Stanford Research Institute, and the more intuitively guided image-based procedures of GIAPP, developed on the equipment at the National Research Council of Canada, in collaboration with the Geological Survey of Canada and the University of Ottawa.     

Stratigraphic evidence for the extinction of the ichthyosaurs

The extinction of ichthyosaurs is not well understood both in terns of time and of causation although it is supposed to have happened at some point of the Late Cretaceous. Four species of ichthyosaurs attributed to the single cosmopolitan genus Platypteygius Huene, 1922 are currently recognized from the Albian and Cenomanian, but after that time only fragmentary remains have been described. A review of these available post-Cenomanian ichthyosaur remains reveals that all are doubtful either from a stratigraphic or a systematic point of view. Ichthyosaur extinction may be tentatively correlated with the Cenomanian-Turonian boundary events. During this interval, biological factors such as a break in the food chain attested by severe extinction in marine invertebrates, especially belemnites, may have led to the extinction of ichthyosaurs.     

混凝剂处理钻井废泥浆液的研究

通过烧杯搅拌实验对混凝剂处理钻井废泥浆液进行研究,从混凝剂适应p H值范围、混凝效果、沉降速度三方面研究比较,找出一种较为理想的混凝剂,并分析了影响混凝剂性能的主要因素,确定了混凝剂的最佳投放剂量。      

浅谈矿山企业露天开采成本的核算

矿山企业露天开采成本的核算是矿山企业经济核算最重要的内容,露天开采成本核算直接关系到企业的发展与稳定。本文针对矿山企业目前的成本核算提出了一些新思路。     

大回线瞬变电磁法全区视电阻率的逆样条插值计算

给出了一种方便快捷的瞬变电磁全区视电阻率数值计算方法--逆样条插值法。对几例由2.5维正演程序获得的理论数据的计算结果表明,逆样条插值法用于全区视电阻率的定义是可行的。与此同时,该方法的实现也为瞬变电磁自动反演中初始模型的构制奠定了基础。     

尾矿坝非饱和带滞水曲线模型的建立及应用

尾矿坝非饱和带的滞水现象是影响坝体稳定性的重要因素。基于尾矿沉积物土工技术的经验参数,建立了含水率与基质吸力的经验模型。经黄山岭铅锌矿尾矿坝和试验室模拟分析验证,预测结果与实际观测结果基本吻合。     

On Distance Measures for the Fuzzy K-means Algorithm for Joint Data

Summary  The analysis of data collected on rock discontinuities often requires that the data be separated into joint sets or groups. A statistical tool that facilitates the automatic identification of groups of clusters of observations in a data set is cluster analysis. The fuzzy K-means cluster technique has been successfully applied to the analysis of joint survey data. As is the case with all clustering algorithms, the results of an analysis performed with the fuzzy K-means algorithm for discontinuity data are highly dependent on the distance metric employed in the analysis. This paper explores the significant issues surrounding the choice and use of various distance measures for clustering joint survey data. It also proposes an analogue of the Mahalanobis distance norm (used for data in Euclidean space) for clustering spherical data. Sample applications showing the greater flexibility and power of the new distance measure over the originally proposed distance metric for spherical data are given in the paper.     

Error Estimates for a Time Discretization Method for the Richards' Equation

We present a numerical analysis of a time discretization method applied to Richards' equation. Written in its saturation-based form, this nonlinear parabolic equation models water flow into unsaturated porous media. Depending on the soil parameters, the diffusion coefficient may vanish or explode, leading to degeneracy in the original parabolic equation. The numerical approach is based on an implicit Euler time discretization scheme and includes a regularization step, combined with the Kirchhoff transform. Convergence is shown by obtaining error estimates in terms of the time step and of the regularization parameter.     

Selection Assistance for the Evaluation of Geoconstruction Technologies for Transportation Applications

A new comprehensive, web-based information system summarizes forty-six geoconstruction technologies, or ground improvement methods, applicable to transportation infrastructure from the following areas: geosynthetics, geotextiles, ground improvement, grouting, slope stabilization, soil reinforcement, soil stabilization, and alternative/recycled materials. Selection assistance was developed as part of the overall information system to aid the user in identifying potential geoconstruction technologies for a project-specific set of conditions. A knowledge base to assist a user in evaluating the current status of each technology with regard to the U.S. practice and the potential applications for each technology is described in detail. Selection assistance includes qualitative ratings for each technology, a listing of the technologies sorted by classification or desired improvement, and a dynamic, Interactive Selection tool. After assisting the user in identifying a short list of potential technologies, the user can access the technology specific data in the information system to further evaluate the technologies. Engineers, planners, and owners will be able to utilize the entire information system to assess the feasibility of technologies to address project-specific requirements and constraints.     

Quantitative technique for assessing the geomorphic thresholds for floodplain instability and braiding in the semi-arid environment

For the semi-arid environment of southern California, a reach-scale classification system and conceptual model were created to synthesize the observed floodplain forms into three basic floodplain continuums: armored, non-armored, and active-regional alluvial fan. These continuums are comprised of three to five alluvial floodplain forms (cascade, step-pool, plane-coarse-bed, plane-mixed-bed, plane-fine-bed, pool-riffle, braided, and dune-ripple). For the non-armored floodplain continuum, a floodplain state diagram has been generated to quantitatively describe the natural downstream progression of floodplain forms and geometry, using specific stream power and the width-to-depth ratio as the state and shape metrics, respectively. Based on field data for 91 cross sections along 14 watercourses, this floodplain state diagram provided the basis to define geomorphic thresholds for floodplain instability and braiding using logistic regression analyses. This method for defining floodplain instability thresholds provides a unique management tool by providing both a systematic and a quantitative means to assess the stability state of watercourses and, thereby, provide a means for assessing the potential for the hazards associated with watercourse instability.     

GPS results for Macedonia and its importance for the tectonics of the Southern Balkan extensional regime

GPS results from 25 stations in Macedonia measured in 1996 and 2000 show that Macedonia moves SSE relative to Eurasia essentially as a single crustal piece along with parts of westernmost Bulgaria. Geological studies show active N–S normal faults and two NNW-striking right-lateral faults in western Macedonia, and NW-trending left-lateral faults SE Macedonia, with a region in central Macedonia essentially devoid of active faults. Distribution of seismic activity supports the geological studies. However, the GPS results cannot discriminate the active faulting, except perhaps in the northern part of Macedonia in the Skopje and adjacent areas, where active ~NS extension occurs. Slip-rates on the strike-slip faults must be low, in the range of 0–2 mm/year. There is a progressive increase in GPS velocities southward in northern Greece toward the North Anatolian fault zone, across which the velocities increase and change direction dramatically.     

Source basins for sediment-hosted stratiform Cu deposits: implications for the structure of the Zambian Copperbelt

The Central African Copperbelt in Zambia and the Democratic Republic of Congo is the world's largest sediment-hosted stratiform Cu province. The source for the Cu in sediment-hosted stratiform Cu deposits is generally believed to be thick sections of oxidised siliciclastic sediments (red beds) and volcanic rocks deposited in early rift sequences underlying or laterally adjacent to the ore-bearing sediments. The volume of red beds beneath or lateral to the Zambian portion of the copperbelt relative to the amount of known metal in the deposits is small in comparison to the volumes of source beds in other well-known districts such as the Polish Kupferschiefer and the White Pine District, USA. Previous structural studies suggest that the rocks hosting the Zambian Cu deposits may be allochthonous or para-autochthonous. The apparent absence of source sediments for the metals, combined with the known structural geology, strongly suggests that the Zambian deposits were tectonically displaced from their source rocks. Defining the present location of the source basins would constrain the amount of tectonic transport in this portion of the Lufilian Arc and would stimulate mineral exploration in new areas.     

花岗质岩石新地球化学分类介绍及有关问题评述

Frost等主要依据花岗岩类常量元素分析,考虑铁镁指数,修改的碱钙指数(MALI)和铝饱和指数三个参数,将花岗岩类岩石划分为16个成分组,即16种类型。该分类方案能对岩浆来源和大地构造背景提供信息,基本上保留了以前一些花岗岩分类方案的最佳品质。本文对这个分类方案进行了详细介绍,并对各种花岗岩类分类方案进行了简要评述。     

Timescales for mechanisms for the dynamical evolution of open star clusters

We have obtained the stellar velocity dispersion in three mutually perpendicular directions in the halos and cores of clusters as a function of time for several non-stationary open-cluster models. During the dynamical evolution of the open-cluster models, the velocity dispersions undergo oscillations that do not decay during 5–10 violent-relaxation timescales, τ _vr . We estimated the time for synchronization of the rotation of the open-cluster models and their motion around the center of the Galaxy, t _s , which, depending on the model parameters, is t _s ? (5–27)τ _vr . Synchronization mechanisms for the models are discussed. The disruption of the systems in the force field of the Galaxy is strongly affected by tidal friction. We have also estimated the time for the formation of a spherical stellar-velocity distribution in the cluster models, t _σ ? (6 ? 25)τ _vr . The impact of instability in the stellar motions in a cluster on the formation of a spherical velocity distribution in the open-cluster models is discussed. We have noted a tendency for a weakening of the dependence of the coarse phase density of the cluster on small initial perturbations of the stellar phase coordinates in the model cluster cores for times about five times longer than the violent-relaxation time.