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101.
W.John Nelson Donald L. Eggert William A. Dimichele Amy C. Stecyk 《International Journal of Coal Geology》1985,4(4):355-370
Basal Pennsylvanian coal-bearing strata exposed along Roaring Creek, west-central Indiana, exhibit extreme lateral discontinuity. Coal seams abruptly change in thickness and elevation; they split, grade into shale, are cut out by channels and disrupted by soft-sediment deformational structures. Initial sediments were laid down by a network of southwest-flowing streams that traversed a deeply channelized upland surface of Mississippian carbonate rocks. Channels aggraded rapidly as uplands were worn down, so the region changed through time from uplands to upper deltaic plain. Local environments included channels, localized point bars, small natural levees and crevasse splays, overbank deposits, and swamps. Differential compaction and subsidence, slumping stream banks, and possibly collapsing sinkholes influenced sedimentation. As a consequence, coals are too discontinuous for economical mining, although they are locally thick and high in quality. 相似文献
102.
Amy Lobben 《The Professional geographer》2003,55(3):318-328
The development of a definition and classification scheme for cartographic animation is now warranted, since focus on the visualization method increased during the 1990s. This article offers a comprehensive definition of animation, distinguishing between animation, slide shows, multimedia, and hypermedia. In addition, a classification system identifies and offers specific characteristics for four different methods or types of cartographic animation: time, areal, thematic, and process. 相似文献
103.
Accurate and reliable methods for quantifying grain size are important for river science, management and in various other sedimentological settings. Remote sensing offers methods of quantifying grain size, typically providing; (a) coarse outputs (c. 1 m) at the catchment scale where individual grains are at subpixel level, or; (b) fine resolution outputs (c. 1 mm) at the patch scale. Recently, approaches using unmanned aerial vehicles (UAVs) have started to fill the gap between these scales, providing hyperspatial resolution data (< 10 cm) over reaches a few hundred metres in length, where individual grains are at suprapixel level. This ‘mesoscale’ is critical to habitat assessments. Most existing UAV‐based approaches use two‐dimensional (2D) textural variables to predict grain size. Validation of results is largely absent however, despite significant differences in platform stability and image quality obtained by manned aircraft versus UAVs. Here, we provide the first quantitative assessment of the accuracy and precision of grain size estimates produced from a 2D image texture approach. Furthermore, we present a new method which predicts subaerial gravel size using three‐dimensional (3D) topographic data derived from UAV imagery. Data is collected from a small gravel‐bed river in Cumbria, UK. Results indicate that our new topographic method gives more accurate measures of grain size (mean residual error ‐0.0001 m). Better results for the image texture method may be precluded by our choice of texture measure, the scale of analysis or the effects of image blur resulting from an inadequate camera gimbal. We suggest that at our scale of assessment, grain size is more strongly related to 3D variation in elevation than to the 2D textural patterns expressed within the imagery. With on‐going improvements, our novel method has potential as the first grain size quantification approach where a trade‐off between coverage and resolution is not necessary or inherent. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
104.
Marine protected areas (MPAs) are among the most widely accepted methods of marine management. MPAs are not, however, always placed such that they can maximize impact on conservation and livelihoods. Current MPA guidelines fall short in focusing primarily on biophysical criteria, overlooking interrelated socioeconomic factors. We identified 32 socioeconomic factors that influence whether MPA placement has an impact on biodiversity and/or livelihoods and weighted the quality of evidence using a novel “Evidence for Impact” Score. Results suggest that stakeholder engagement, poverty, population density, and strong leadership have most potential to positively impact biodiversity and/or livelihoods, but the direction of impact (i.e., positive or negative) can be context-dependent. We found a generally poor evidence base for impact evaluation of socioeconomic factors: though some factors were highly cited, few studies actually evaluate impact. Results indicate the need for a more interdisciplinary approach to MPA placement and more empirical studies that assess impact. 相似文献
105.
Prediction of hydrocarbon recovery from turbidite sandstones with linked-debrite facies: Numerical flow-simulation studies 总被引:1,自引:1,他引:0
Lawrence A. Amy Simon A. Peachey Andy A. Gardiner Peter J. Talling 《Marine and Petroleum Geology》2009,26(10):2032
A series of two-dimensional numerical flow simulations were carried out to investigate the production characteristics of a sheet sandstone bed with a linked-debrite interval. A deterministic geological model was used based on a two-dimensional representation of a bed from the Marnoso Arenacea Formation. The model was 60 km long and 1 m thick and contained three zones, arranged in a vertical facies arrangement typical of many linked-debrite beds: i) a lower, coarse-to-medium grained, clean turbidite sandstone interval; ii) a middle, muddy sandstone, debrite interval; iii) an upper, fine-grained, clean, laminated sandstone interval. Simulation involved only a 3-km long sector of the model, with one injector well and one production well, placed 1-km apart in the middle of the sector model. The simulated sector was moved progressively down the length of the bed, in 1-km steps, sampling different parts of the bed with different facies proportions. The petrophysical properties of the debrite interval were varied to produce different porosity–permeability cases. All other modelling parameters, including the upper and lower interval petrophysics, were kept constant. Results indicate that, in most cases, key production parameters such as cumulative oil production with time and water cut are proportional to the volume of movable oil between the wells. This relationship does not hold, however, for cases with relatively low values of debrite porosity (≤0.15) and permeability (kh ≤ 100 mD) where the debrite interval accounts for more than 20% of the interwell volume. In these models, production efficiency declines systematically with reducing reservoir quality and increasing debrite percentage, resulting in relatively low oil production and early water breakthrough. 相似文献
106.
Knowledge of groundwater seepage to and from lakes can be an important component of scientific investigations involving water and geochemical budgets. Measurements of groundwater seepage at Lake Anna, a man-made lake in central Virginia, show that inflow to the lake occurs even under dry summer conditions. Seepage rates were found to be correlated with the elevation of the near-shore water table, which responded rapidly to rainfall events in the fractured rock terrane in which Lake Anna is located. Seepage rates did not decline uniformly with distance offshore. This result contrasts with those for lakes underlain by relatively homogeneous porous media where measurements generally confirm the prediction that seepage rates drop off exponentially with distance from shore. The along shore variability of seepage rates in Lake Anna was related to a topographic index that is used to describe drainage from hillslopes. This suggests that seepage in impoundments such as Lake Anna may be strongly controlled by drainage pathways that pre-date the lake. 相似文献
107.
Jupiter's equatorial atmosphere, much like the Earth's, is known to show quasi-periodic variations in temperature, particularly in the stratosphere, but variations in other jovian atmospheric tracers have not been studied for any correlations to these oscillations. Data taken at NASA's Infrared Telescope Facility (IRTF) from 1979 to 2000 were used to obtain temperatures at two levels in the atmosphere, corresponding to the upper troposphere (250 mbar) and to the stratosphere (20 mbar). We find that the data show periodic signals at latitudes corresponding to the troposphere zonal wind jets, with periods ranging from 4.4 (stratosphere, 95% confidence at 4° S planetographic latitude) to 7.7 years (troposphere, 97% confidence at 6° N). We also discuss evidence that at some latitudes the troposphere temperature variations are out of phase from the stratosphere variations, even where no periodicity is evident. Hubble Space Telescope images were used, in conjunction with Voyager and Cassini data, to track small changes in the troposphere zonal winds from 20° N to 20° S latitude over the 1994-2000 time period. Oscillations with a period of 4.5 years are found near 7°-8° S, with 80-85% significance. Further, the strongest evidence for a QQO-induced tropospheric wind change tied to stratospheric temperature change occurs near these latitudes, though tropospheric temperatures show little periodicity here. Comparison of thermal winds and measured zonal winds for three dates indicate that cloud features at other latitudes are likely tracked at pressures that can vary by up to a few hundred millibar, but the cloud altitude change required is too large to explain the wind changes measured at 7° S. 相似文献
108.
Amy Hessl Jennifer Miller James Kernan David Keenum Don McKenzie 《The Professional geographer》2007,59(1):87-104
Fire history studies have traditionally emphasized temporal rather than spatial properties of paleo‐fire regimes. In this study we compare four methods of mapping paleo‐fires in central Washington from binary point data: indicator kriging, inverse distance weighting, Thiessen polygons, and an expert approach. We evaluate the results of each mapping method using a test (validation) dataset and receiver operating characteristic plots. Interpolation methods perform well, but results vary with fire size and spatial pattern of points. Though all methods involve some subjectivity, automated interpolation methods perform well, are replicable, and can be applied across varying landscapes. 相似文献
109.
Mark P. S. Krekeler Pete Probst Misha Samsonov Cynthia M. Tselepis William Bates Lance E. Kearns J. Barry Maynard 《Environmental Geology》2007,53(4):709-726
Subsurface flow constructed wetlands in the village of Akumal, Quintana Roo, Mexico were surveyed to determine the general
status of the wetland systems and provide baseline information for long term monitoring and further study. Twenty subsurface
flow wetlands were surveyed and common problems observed in the systems were overloading, poor plant cover, odor, and no secondary
containment. Bulk mineral composition of aggregate from two subsurface flow constructed wetlands was determined to consist
solely of calcite using bulk powder X-ray diffraction. Some soil structure is developed in the aggregate and aggregate levels
in wetlands drop at an estimated rate between 3 and 10 cm/year for overloaded wetlands owing to dissolution. Mineral composition
from fresh aggregate samples commonly is a mixture of calcite and aragonite. Trace amounts of Pb, Zn, Co, and Cr were observed
in fresh aggregate. Coefficients of permeability (k) varied from 0.006 to 0.027 cm/s with an average values being 0.016 cm/s. Grain size analysis of fresh aggregate samples
indicates there are unimodal and multimodal size distributions in the samples with modes in the coarse and fine sand being
common. Investigations of other geologic media from the Reforma region indicate that a dolomite with minor amounts of Fe-oxide
and palygorskite is abundant and may be a better aggregate source that the current materials used. A Ca-montmorillonite bed
was identified in the Reforma region as well and this unit is suitable to serve as a clay liner to prevent leaks for new and
existing wetland systems. These newly discovered geologic resources should aid in the improvement of subsurface flow constructed
wetlands in the region. Although problems do exist in these wetlands with respect to design, these systems represent a successful
implementation of constructed wetlands at a community level in developing regions. 相似文献
110.
Amy?L?Ryser Daniel?G?StrawnEmail author Matthew?A?Marcus Jodi?L?Johnson-Maynard Mickey?E?Gunter Gregory?M?ller 《Geochemical transactions》2005,6(1):1
Mining activities in the US Western Phosphate Resource Area (WPRA) have released Se into the environment. Selenium has several
different oxidation states and species, each having varying degrees of solubility, reactivity, and bioavailability. In this
study we are investigating the speciation of Se in mine-waste rocks. Selenium speciation was determined using bulk and micro-x-ray
absorption spectroscopy (XAS), as well as micro-x-ray fluorescence mapping. Rocks used for bulk-XAS were ground into fine
powders. Shale used for micro-XAS was broken along depositional planes to expose unweathered surfaces. The near edge region
of the XAS spectra (XANES) for the bulk rock samples revealed multiple oxidation states, with peaks indicative of Se(-II),
Se(IV), and Se(+VI) species. Micro-XANES analysis of the shale indicated that three unique Se-bearing species were present.
Using the XANES data together with ab initio fitting of the extended x-ray absorption fine structure region of the micro-XAS data (micro-EXAFS) the three Se-bearing species
were identified as dzharkenite, a di-selenide carbon compound, and Se-substituted pyrite. Results from this research will
allow for a better understanding of the biogeochemical cycling of Se in the WPRA. 相似文献