吐哈盆地侏罗系砂岩储层中粘土矿物组成和分布的控制因素   总被引：1，自引：0，他引：1       下载免费PDF全文

张小青  黄天雪  刘军  杨传宏 《沉积与特提斯地质》2001,21(4):66-69

在大量分析数据基础上，总结了吐哈盆地侏罗系砂岩储层中粘土矿物组成及其在纵横向上的分布特征，重点对吐哈盆地侏罗系岩储层中粘土矿物组成和分布的主控因素进行了分析，笔者认为吐哈盆地的成岩过程中砂岩孔隙介质条件，不同沉只环境砂体渗滤条件的差异，盆地的大地构造背景和构造发育史以及盆地演化过程中的古气候变化等是影响盆地砂岩粘放物组成和分布的主控因素。由此可以为寻找有利储层和设计酸化采油方案提供重要的依据。  相似文献   

Estimating Population Attribute Values in a Table: “Get Me Started in” Iterative Proportional Fitting     

Nik Lomax  Paul Norman 《The Professional geographer》2016,68(3):451-461

Iterative proportional fitting (IPF) is a technique that can be used to adjust a distribution reported in one data set by totals reported in others. IPF is used to revise tables of data where the information is incomplete, inaccurate, outdated, or a sample. Although widely applied, the IPF methodology is rarely presented in a way that is accessible to nonexpert users. This article fills that gap through discussion of how to operationalize the method and argues that IPF is an accessible and transparent tool that can be applied to a range of data situations in population geography and demography. It offers three case study examples where IPF has been applied to geographical data problems; the data and algorithms are made available to users as supplementary material.  相似文献   

Environmental controls on food web regimes: A fluvial perspective     

Mary E. Power 《Progress in Oceanography》2006,68(2-4):125

Because food web regimes control the biomass of primary producers (e.g., plants or algae), intermediate consumers (e.g., invertebrates), and large top predators (tuna, killer whales), they are of societal as well as academic interest. Some controls over food web regimes may be internal, but many are mediated by conditions or fluxes over large spatial scales. To understand locally observed changes in food webs, we must learn more about how environmental gradients and boundaries affect the fluxes of energy, materials, or organisms through landscapes or seascapes that influence local species interactions. Marine biologists and oceanographers have overcome formidable challenges of fieldwork on the high seas to make remarkable progress towards this goal. In river drainage networks, we have opportunities to address similar questions at smaller spatial scales, in ecosystems with clear physical structure and organization. Despite these advantages, we still have much to learn about linkages between fluxes from watershed landscapes and local food webs in river networks. Longitudinal (downstream) gradients in productivity, disturbance regimes, and habitat structure exert strong effects on the organisms and energy sources of river food webs, but their effects on species interactions are just beginning to be explored. In fluid ecosystems with less obvious physical structure, like the open ocean, discerning features that control the movement of organisms and affect food web dynamics is even more challenging. In both habitats, new sensing, tracing and mapping technologies have revealed how landscape or seascape features (e.g., watershed divides, ocean fronts or circulation cells) channel, contain or concentrate organisms, energy and materials. Field experiments and direct in situ observations of basic natural history, however, remain as vital as ever in interpreting the responses of biota to these features. We need field data that quantify the many spatial and temporal scales of functional relationships that link environments, fluxes and food web interactions to understand how they will respond to intensifying anthropogenic forcing over the coming decades.  相似文献   

Geomorphic controls and transition zones in the lower Sabine River     

Jonathan D. Phillips 《水文研究》2008,22(14):2424-2437

Instream flow science and management requires identification of characteristic hydrological, ecological, and geomorphological attributes of stream reaches. This study approaches this problem by identifying geomorphic transition zones along the lower Sabine River, Texas and Louisiana. Boundaries were delineated along the lower Sabine River valley based on surficial geology, valley width, valley confinement, network characteristics (divergent versus convergent), sinuousity, slope, paleomeanders, and point bars. The coincidence of multiple boundaries reveals five key transition zones separating six reaches of distinct hydrological and geomorphological characteristics. Geologic controls and gross valley morphology play a major role as geomorphic controls, as does an upstream‐to‐downstream gradient in the importance of pulsed dam releases, and a down‐to‐upstream gradient in coastal backwater effects. Geomorphic history, both in the sense of the legacy of Quaternary sea level changes, and the effects of specific events such as avulsions and captures, are also critical. The transition zones delineate reaches with distinct hydrological characteristics in terms of the relative importance of dam releases and coastal backwater effects, single versus multi‐channel flow patterns, frequency of overbank flow, and channel‐floodplain connectivity. The transitional areas also represent sensitive zones which can be expected to be bellwethers in terms of responses to future environmental changes. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Scale Dependencies of Vegetation and Topography in a Mountainous Environment of Montana   总被引：2，自引：2，他引：2  

Ling Bian  Stephen J. Walsh 《The Professional geographer》1993,45(1):1-11

This research examines the effects of spatial scale on estimating the relationship between vegetation biomass and topography within a portion of Glacier National Park, Montana. The Reflectance/Absorptance vegetation index, developed from processed Landsat Thematic Mapper digital data, is related to three topographic variables obtained through processed Digital Elevation Models: elevation, slope angle, and slope aspect. R² values between the vegetation index and the topographic variables are obtained from regression analyses at a series of aggregated spatial scales. The effective range of spatial scales within which the two sets of variables are spatially dependent and the degree of the spatial dependencies are characterized through semivariance and fractal analyses.  相似文献   

Cyclic facies architecture as a key to depositional controls in a distal foredeep: Campanian Mesaverde Group,Wyoming, USA     

B. Klug 《International Journal of Earth Sciences》1993,82(2):306-326

The Mesaverde Group consists of a thick wedge of fluvial, littoral-deltaic and shallow marine clastics shed into the Cretaceous Western Interior Seaway of North America. The western parts of the seaway lay within the strongly subsiding foredeep of the active Sevier fold and thrust belt further to the west. The study area is located east of the axis of maximum subsidence and is thus in a favourable position to record competing effects of eustasy, sediment supply and thrust-load induced subsidence. Facies and sequence analysis carried out on high quality outcrop and well log data led to the recognition of a complex depositional cycle hierarchy within the typical storm- and wave-dominated inner shelf/shoreface/strand plain and delta systems of the Mesaverde. Fourth-order parasequences and parasequence bundles of estimated 100–400 ka duration are the best recognizable, ubiquitous and most useful stratigraphic units. Their arrangement with respect to sequence boundaries, however, varies with their overall stratigraphic position and also differs from the Exxon models. Mesaverde progradation was interrupted by a major transgression that occurred out of phase with the aggradational to progradational stacking trend of third-order sequences. A proposed genetic model relates large-scale (second-order) sequence architecture to tectonics: a Sevier thrust event as well as Laramide uplift within the foredeep controlled non-linear changes in the accommodation/supply ratio. Parasequence stacking patterns and sequence boundary formation, in contrast, were the product of (global?) eustasy enhanced by short-term, perhaps local, changes in the rates of subsidence and detrital influx.  相似文献   

Environmental study on a long history of Cu mining in Hubei, central China     

Mingqi WANG 《中国地球化学学报》2006,25(B08):33-34

The Tonglushan Cu mine situated in a densely populated, humid temperate ecoregional domain, so called the Birthplace of the Bronze age in the world, has been mined for over three thousand years. However, there is no significant pollution in surrounding area yet. To understand the mechanism controlling the environment the geological controls, including regional geology, deposit type, deposit size, host rocks, mineralogy, texture, alteration, ore controls, were studied by re-evaluating data from mineral exploration and mining activities; the geochemical factors including soils both in rice field and dry land, underground water and rice were investigated in 2003-2004. The results show that the ground water around the mine is not contaminated,  相似文献   

Factors influencing ammonia volatilization from urea in soils of the shortgrass steppe   总被引：2，自引：0，他引：2  

D. G. Milchunas  W. J. Parton  D. S. Bigelow  D. S. Schimel 《Journal of Atmospheric Chemistry》1988,6(4):323-340

The effects of soil moisture, temperature, and humidity treatments on urea hydrolysis and NH₃ volatilization were assessed in the laboratory. Field studies were conducted to determine seasonal NH₃ losses from simulated urine patches applied to contrasting soils of a representative hillslope of the shortgrass steppe region in the North American Great Plains.Losses of NH₃–N were most influenced by soil moisture. The effects of temperature and humidity on total, or temporal, losses of NH₃ were dependent on soil moisture. Losses ranged from 18.5% under conditions of low-temperature/high-humidity/wet soil to 7.7% under conditions of high-temperature/low-humidity/dry soil. In contrast, urea hydrolysis was not affected by soil moisture.Losses of NH₃–N from simulated urine applied to field plots ranged from 1.5% on footslope soils in summer to 14.1% on backslope (midslope) soils in summer, whereas losses were 8.1% on back-slope soils in winter. Factors such as soil texture, microbial activity, and plant productivity along a toposequence had larger effects than climatic variables on variation in the volatile losses of NH₃–N from this grassland.This paper is a report on the work presented at the international symposium Influence of marine and terrestrial biosphere on the chemical composition of the atmosphere, held in Mainz, F.R.G., on 16–22 March 1986.  相似文献   

Geology of the Ranger Uranium Mine, Northern Territory, Australia: structural constraints on the timing of uranium emplacement   总被引：1，自引：0，他引：1  

K. A. A. Hein   《Ore Geology Reviews》2002,20(3-4)

The geology of the No 1 and 3 pits at the Ranger Mine in the Pine Creek Inlier (PCI) of Australia is dominated by Palaeoproterozoic volcanic, carbonate and sedimentary sequences that unconformably overlie Archaean granitic gneiss of the Nanambu Complex (2470±50 Ma). These sequences are folded, faulted and sheared, and crosscut by east-trending granite (sensu stricto) dykes and pegmatite veins, and gently dipping N–NE trending mafic dykes of the Oenpelli Dolerite (1690 Ma). Regional metamorphism is to greenschist facies and contact metamorphism is to hornblende-hornfels facies.The rocks of the Ranger Mine have been subjected to at least two phases of ductile–brittle deformation (D2–D3) and one phase of brittle deformation (D4). These events were preceded by regional diastathermal or extension-related metamorphism (D1) and the development of an ubiquitous bedding-parallel cleavage (S1).D2 resulted in the development of NNE–NNW trending mesoscopic folds (F2) and a network of thrusts and dextral reverse shears. The modelled palaeo-stress directions for the emplacement of pegmatite veins suggests that they formed early in D2. D3 resulted in the development of WNW–NW trending mesoscopic folds (F3), a weakly defined axial planar cleavage (S3) and sinistral reactivation of D2 shears. D2–D3 are correlated with deformation during the Maud Creek Event of the Top End Orogeny (1870–1780 Ma), while the emplacement of granite dykes and pegmatite veins is correlated with emplacement of regional granites at 1870–1860 Ma.D4 is associated with brittle deformation and resulted in the development of normal faults and fault breccias during a period of east–west extension. This event is correlated with regional east–west extension during deposition of Palaeo- to Mesoproterozoic platform sequences.The sequence of tectonic events established in this study indicates that uranium-bearing ore shoots in the Ranger No 1 and 3 pits formed during extension in D4, and after emplacement of the Oenpelli Dolerite at 1690 Ma. However, the currently accepted 1737±20 U–Pb Ma age places the mineralising event at time of regional post-orogenic erosion, after the Top End Orogeny and before emplacement of the Oenpelli Dolerite and extension in D4. The U–Pb age is not consistent with Sm–Nd ages for primary uranium mineralisation at Nabarlek and Jabiluka at 1650 Ma [Econ. Geol. 84 (1989) 64] and does not concur with currently accepted regional tectonic data of Johnston [Johnston, J.D., 1984. Structural evolution of the Pine Creek Inlier and mineralisation therein, Northern Territory, Australia. Unpublished PhD Thesis, Monash University, Australia], Needham et al. [Precambrian Res. 40/41 (1988) 543] and others. Consequently, the absolute age of uranium mineralisation at the Ranger Mine is open.  相似文献   

企业内部控制存在的问题及对策     

李仲夏 《广东海洋大学学报》2006,26(5):30-33

针对我国的企业在内部控制方面存在的问题:内部控制环境弱化,内部控制体系不完善、会计系统设计未充分考虑内部控制,会计资料过于简化,内部控制评价缺乏具体标准和尺度;提出加强企业内部控制的一些对策:要加强内部控制体系建设;加强企业内部控制环境;营造重视内部控制的氛围。  相似文献