Appalachian Plateau Province Research Articles

Engineering Geology, History and Geography of the Pittsburgh, Pennsylvania Area

ABSTRACTThe City of Pittsburgh, PA is located west of the Appalachian Mountains in the Appalachian Plateaus Province. The relatively flat surface of the plateau is dissected by drainage from the three principal rivers of the region, the Allegheny, Monongahela, and Ohio. The formation of Pittsburgh’s three rivers and drainages has a long history dating back to before the Pleistocene Epoch, linked closely to the advance and retreat of continental glaciation.Western Pennsylvania is associated with the westernmost formation of the Appalachian Mountain chain with deformation in the form of a series of nearly flat-lying, gently warped Paleozoic sedimentary rocks. Rocks cropping out in the region range in age from Devonian to Permian. Pennsylvanian strata are dominated by thin cyclic sequences of sandstone, shale, claystone, coal, and limestone. Most of the geologic hazards present in the region include slope instability, expansive shales and slags, mine subsidence, acid mine drainage, pyritic acid rock and flooding. The region also has an abundance of natural resources including coal, natural gas, oil, salt, limestone, sand and gravel and water.Pittsburgh's strategic location helped shape westward expansion during the formation of the Nation, largely because of the rivers, which served as an inexpensive, yet efficient means of transportation. Infrastructure was always significant in Pittsburgh. However, the existing aging infrastructure are deteriorating. Today, Pittsburgh has transcended the legacy name, “Steel City” and has revitalized itself with nationally-recognized universities and medical centers and a resurgence in natural gas exploration. However, many environmental legacy issues still burden the area.

Forecasting effects of tree species reintroduction strategies on carbon stocks in a future without historical analog.

American chestnut (Castanea dentata) was once an important component forests in the central Appalachians (USA), but it was functionally extirpated nearly a century ago. Attempts are underway to reintroduce blight-resistant chestnut to its former range, but it is uncertain how current forest composition, climate, and atmospheric changes and disturbance regimes will interact to determine future forest dynamics and ecosystem services. The combination of novel environmental conditions (e.g. climate change), a reintroduced tree species and new disturbance regimes (e.g. exotic insect pests, fire suppression) have no analog in the past that can be used to parameterize phenomenological models. We therefore used a mechanistic approach within the LANDIS-II forest landscape model that relies on physiological first principles to project forest dynamics as the outcome of competition of tree cohorts for light and water as a function of temperature, precipitation, CO2 concentration, and life history traits. We conducted a factorial landscape simulation experiment to evaluate specific hypotheses about future forest dynamics in two study sites in the center of the former range of chestnut. Our results supported the hypotheses that climate change would favor chestnut because of its optimal temperature range and relative drought resistance, and that chestnut would be less competitive in the more mesic Appalachian Plateau province because competitors will be less stressed. The hypothesis that chestnut will increase carbon stocks was supported, although the increase was modest. Our results confirm that aggressive restoration is needed regardless of climate and soils, and that increased aggressiveness of chestnut restoration increased biomass accumulation. The hypothesis that chestnut restoration will increase both compositional and structural richness was not supported because chestnut displaced some species and age cohorts. Although chestnut restoration did not markedly enhance carbon stocks, our findings provide hope that this formerly important species can be successfully reintroduced and associated ecosystem services recovered.

Lithium in fluids from Paleozoic-aged reservoirs, Appalachian Plateau region, USA

This study presents the spatial distribution of a compilation of lithium (Li) and selected other dissolved species concentrations in saline fluids from oil and gas wells in western Pennsylvanian and eastern Ohio that are producing from Silurian- to Devonian-age formations. Lithium concentrations in the data set range from about 40 to 40,000μmolkg−1 indicating water–rock reactions that added Li to the saline fluids. Chloride (Cl) concentrations range from about 160 to 5300mmolkg−1, likely the result of different burial fluids (seawater or evaporated seawater), variable dilution with meteoric water and variable interaction with marine evaporites. The Li/Cl in these fluids is not constant, potentially indicating multiple sources of Li in addition to multiple origins of Cl. Lithium and the Li/Cl ratio generally decrease from east to west across the study area in four or five bands of similar Li or Li/Cl. Lithium and Li/Cl are not correlated with petroleum-production formation and are only generally correlated with depth. A few of the fluid samples have anomalously high Li and Li/Cl. These anomalous samples coincide in location with northwesterly trending salients of high vitrinite reflectance, suggesting that Li in this segment of the Appalachian Plateau Province may provide insight into paleoflow pathways in the region, indicating where hot, chemically evolved, saline fluids might have been driven to the northwest, upwards and out of the basin, during tectonism.

Unraveling the stratigraphy of the Oriskany Sandstone: A necessity in assessing its site-specific carbon sequestration potential

The widespread distribution, favorable reservoir characteristics, and depth make the Lower Devonian Oriskany Sandstone a viable sequestration target in the Appalachian Basin. The Oriskany Sandstone is thickest in the structurally complex Ridge and Valley Province, thins toward the northern and western basin margins, and is even absent in other parts of the basin (i.e., the no-sand area of northwestern Pennsylvania). We evaluated four regions using petrographic data, core analyses, and geophysical log analyses. Throughout the entire study area, average porosities range from 1.35 to 14%. The most notable porosity types are primary intergranular, secondary dissolution, and fracture porosity. Intergranular primary porosity dominates at stratigraphic pinch-out zones near the Oriskany no-sand area and at the western limit of the Oriskany Sandstone. Secondary porosity occurs from dissolution of carbonate constituents primarily in the combination-traps natural gas play extending through western Pennsylvania, western West Virginia, and eastern Ohio. Fracture porosity dominates in the central Appalachian Plateau Province and Valley and Ridge Province. Based on average porosity, the most likely regions for successful sequestration in the Oriskany interval are (1) updip from Oriskany Sandstone pinch-outs in eastern Ohio, and (2) western Pennsylvania, western West Virginia, and eastern Ohio where production occurs from a combination of stratigraphic and structural traps. Permeability data, where available, were used to further evaluate the potential of these regions. Permeability ranges from 0.2 to 42.7 md. Stratigraphic pinch-outs at the northern and western limits of the basin have the highest permeabilities. We recommend detailed site assessments when evaluating the sequestration potential of a given injection site based on the variability observed in the Oriskany structure, lithology, and reservoir characteristics.

Empirical Models Based on the Universal Soil Loss Equation Fail to Predict Sediment Discharges from Chesapeake Bay Catchments

The Universal Soil Loss Equation (USLE) and its derivatives are widely used for identifying watersheds with a high potential for degrading stream water quality. We compared sediment yields estimated from regional application of the USLE, the automated revised RUSLE2, and five sediment delivery ratio algorithms to measured annual average sediment delivery in 78 catchments of the Chesapeake Bay watershed. We did the same comparisons for another 23 catchments monitored by the USGS. Predictions exceeded observed sediment yields by more than 100% and were highly correlated with USLE erosion predictions (Pearson r range, 0.73-0.92; p < 0.001). RUSLE2-erosion estimates were highly correlated with USLE estimates (r = 0.87; p < 001), so the method of implementing the USLE model did not change the results. In ranked comparisons between observed and predicted sediment yields, the models failed to identify catchments with higher yields (r range, -0.28-0.00; p > 0.14). In a multiple regression analysis, soil erodibility, log (stream flow), basin shape (topographic relief ratio), the square-root transformed proportion of forest, and occurrence in the Appalachian Plateau province explained 55% of the observed variance in measured suspended sediment loads, but the model performed poorly (r(2) = 0.06) at predicting loads in the 23 USGS watersheds not used in fitting the model. The use of USLE or multiple regression models to predict sediment yields is not advisable despite their present widespread application. Integrated watershed models based on the USLE may also be unsuitable for making management decisions.

Stream pH as an Abiotic Gradient Influencing Distributions of Trout in Pennsylvania Streams

AbstractElevation and stream slope are abiotic gradients that limit upstream distributions of brook trout Salvelinus fontinalis and brown trout Salmo trutta in streams. We sought to determine whether another abiotic gradient, base‐flow pH, may also affect distributions of these two species in eastern North America streams. We used historical data from the Pennsylvania Fish and Boat Commission's fisheries management database to explore the effects of reach elevation, slope, and base‐flow pH on distributional limits to brook trout and brown trout in Pennsylvania streams in the Appalachian Plateaus and Ridge and Valley physiographic provinces. Discriminant function analysis (DFA) was used to calculate a canonical axis that separated allopatric brook trout populations from allopatric brown trout populations and allowed us to assess which of the three independent variables were important gradients along which communities graded from allopatric brook trout to allopatric brown trout. Canonical structure coefficients from DFA indicated that in both physiographic provinces, stream base‐flow pH and slope were important factors in distributional limits; elevation was also an important factor in the Ridge and Valley Province but not the Appalachian Plateaus Province. Graphs of each variable against the proportion of brook trout in a community also identified apparent zones of allopatry for both species on the basis of pH and stream slope. We hypothesize that pH‐mediated interspecific competition that favors brook trout in competition with brown trout at lower pH is the most plausible mechanism for segregation of these two species along pH gradients. Our discovery that trout distributions in Pennsylvania are related to stream base‐flow pH has important implications for brook trout conservation in acidified regions. Carefully designed laboratory and field studies will be required to test our hypothesis and elucidate the mechanisms responsible for the partitioning of brook trout and brown trout along pH gradients.

Holocene colluvial soils and geoarchaeology in the unglaciated Appalachian Plateau: Two examples from West Virginia, USA

AbstractBuried and sometimes stratified prehistoric sites occur in upland landscapes of the Unglaciated Appalachian Plateau province, although archaeologists have traditionally believed that such settings contain only near surface cultural deposits. The age of colluvial slopes and the characteristics of associated soils vary considerably from north to south within the province, and with the size and order of the valley. We have identified numerous prehistoric sites in low‐order valleys in central and southern West Virginia, where the dominant valley fill is a variant of colluvium and alluvium (co‐alluvium) that is poorly to moderately sorted and usually stratified. Weakly developed buried soils containing archaeological materials often develop in these strata, and provide evidence of relatively short periods of landscape stability. The archaeological potential of colluvial settings is determined by both the attractiveness of a locale for settlement and by the prospects for preservation of the archaeological remains. In some cases, prehistoric components have been partially disturbed by co‐alluvial reworking and redeposition, but, in other cases, the archaeological remains are preserved in a relatively undisturbed context. © 2003 Wiley Periodicals, Inc.

Fate of ‘warm’ migrating fluids in the central Appalachians during the Late Paleozoic Alleghanian orogeny

Middle to Upper Devonian elastic rocks throughout the Valley and Ridge province in the central Appalachians contain evidence for fluid migration during the Late Paleozoic Alleghanian orogeny. Fluid inclusion microthermometry of vein minerals indicate that the migrating fluid was a ‘warm’ (160 to >220 °C) CH 4-saturated NaCl-CaCl 2 brine. However, rocks in the same stratigraphic interval immediately forelandward of the Valley and Ridge contain veins that have significantly different fluid inclusions, indicating that the ‘warm’ fluids did not significantly migrate into the rocks of the Appalachian Plateau province. The ‘warm’ fluids are interpreted to have migrated to the paleosurface as hot springs during the Late Paleozoic. Stable and strontium isotope chemistry of the vein minerals suggests that some infiltration of the 'warm' fluids into the easternmost Plateau province did occur. This indicates that wholesale flushing of a foreland during an orogeny may not be as common as originally thought.

Numerical fluctuations in the northern short‐tailed shrew: evidence of non‐linear feedback signatures on population dynamics and demography

Summary We studied a fluctuating population of the northern short‐tailed shrew (Blarina brevicauda) in the Appalachian Plateau Province of Pennsylvania, USA, spanning 21 years of monitoring. We analysed the pattern of annual temporal variation fitting both time‐series models and capture–mark–recapture (CMR) statistical models for survival and recruitment rates. We determined that non‐linear first‐order models explain almost 80% of the variation in annual per capita population growth rates. In particular, a non‐linear self‐excited threshold autoregressive (SETAR) model describes the time‐series data well. Average snowfall showed positive and non‐linear effects on population dynamics. The CMR statistical models showed that a non‐linear threshold model with strong effects of population density was the best one to describe temporal variation in survival rates. On the other hand, population density or climatic variables did not explain temporal variation in recruitment rates. Survival rates were high during the study period. Weekly changes in population size attributable to new recruits entering in the population fluctuate between 21% and 0%, while the changes in population size related to survival fluctuate between 79% and 100%. Two important results arise from this study. First, non‐linear models with first‐order feedback appear to capture the essential features of northern short‐tailed shrew dynamics and demography. Secondly, climate effects represented by snowfall appear to be small and non‐linear on this insectivore. The population dynamics of this shrew in the Appalachian Plateau are determined apparently by a strong non‐linear first‐order feedback process, which is related to survival rates. This study links population dynamics and demography by detecting the underlying demographic mechanisms driving population dynamics. The feedback structure of this shrew suggests the existence of population dynamics dominated by intraspecific competitive interactions, such as aggression, solitary nesting, non‐overlapping home ranges and territoriality.

Characterizing watershed-delineated landscapes in Pennsylvania using conditional entropy profiles

When the objective is to characterize landscapes with respect to relative degree and type of forest (or other critical habitat) fragmentation, it is difficult to decide which variables to measure and what type of discriminatory analysis to apply. It is also desirable to incorporate multiple measurement scales. In response, a new method has been developed that responds to changes in both the marginal and spatial distributions of land cover in a raster map. Multiscale features of the map are captured in a sequence of successively coarsened resolutions based on the random filter for degrading raster map resolutions. Basically, the entropy of spatial pattern associated with a particular pixel resolution is calculated, conditional on the pattern of the next coarser ‘parent’ resolution. When the entropy is plotted as a function of changing resolution, we obtain a simple two-dimensional graph called a ‘conditional entropy profile’, thus providing a graphical visualization of multi-scale fragmentation patterns. Using eight-category raster maps derived from 30-meter resolution LANDSAT Thematic Mapper images, the conditional entropy profile was obtained for each of 102 watersheds covering the state of Pennsylvania (USA). A suite of more conventional single-resolution landscape measurements was also obtained for each watershed using the FRAGSTATS program. After dividing the watersheds into three major physiographic provinces, cluster analysis was performed within each province using various combinations of the FRAGSTATS variables, land cover proportions and variables describing the conditional entropy profiles. Measurements of both spatial pattern and marginal land cover proportions were necessary to clearly discriminate the watersheds into distinct clusters for most of the state; however, the Piedmont province essentially only required the land cover proportions. In addition to land cover proportions, only the variables describing a conditional entropy profile appeared to be necessary for the Ridge and Valley province, whereas only the FRAGSTATS variables appeared to be necessary for the Appalachian Plateaus province. Meanwhile, the graphical representation of conditional entropy profiles provided a visualization of multi-scale fragmentation that was quite sensitive to changing pattern.

Fractal interrelationships between topography and structure

Factal interrelationships between topography and structure are investigated in two areas of the North American central Appalachian Mountains: one in the intensely deformed Valley and Ridge province and the other in the relatively undeformed foreland area of the Appalachian Plateau province. In the Valley and Ridge province the fractal dimensions of topographic and structural relief vary systematically along the strike of major folds following a second-order polynominal trend. Cross-correlation of the fractal dimensions of topography to structure indicates that there is a significant positive correlation between the two. Fractal analysis of topography in the relatively undeformed foreland area of the Appalachian Plateau revealed no significant variation in the fractal characteristics of topography across the study area, consistent with the lack of near-surface structure. However, fractal analysis of deeper structures beneath the Plateau area undertaken using reflection seismic data revealed step-wise increases in fractal dimension from the deeply buried Precambrian basement to the near-surface. These vertical changes in fractal dimension can be related to the tectonic history of the area. Taken together, these studies indicate that fractal analysis provides a means to quantify and compare the influence of near-surface structure on topographic development and lateral and vertical structural variability. Fractal analysis provides a means to characterize the systematic changes in the complex patterns formed by topography and structure and the interrelationships between them. Similarity in their fractal characteristics implies similarity in the relative amplitude and abundance of different wavelength features in the topographic or structural profile. © 1998 John Wiley & Sons, Ltd.

Fractal interrelationships between topography and structure

Factal interrelationships between topography and structure are investigated in two areas of the North American central Appalachian Mountains: one in the intensely deformed Valley and Ridge province and the other in the relatively undeformed foreland area of the Appalachian Plateau province. In the Valley and Ridge province the fractal dimensions of topographic and structural relief vary systematically along the strike of major folds following a second-order polynominal trend. Cross-correlation of the fractal dimensions of topography to structure indicates that there is a significant positive correlation between the two. Fractal analysis of topography in the relatively undeformed foreland area of the Appalachian Plateau revealed no significant variation in the fractal characteristics of topography across the study area, consistent with the lack of near-surface structure. However, fractal analysis of deeper structures beneath the Plateau area undertaken using reflection seismic data revealed step-wise increases in fractal dimension from the deeply buried Precambrian basement to the near-surface. These vertical changes in fractal dimension can be related to the tectonic history of the area. Taken together, these studies indicate that fractal analysis provides a means to quantify and compare the influence of near-surface structure on topographic development and lateral and vertical structural variability. Fractal analysis provides a means to characterize the systematic changes in the complex patterns formed by topography and structure and the interrelationships between them. Similarity in their fractal characteristics implies similarity in the relative amplitude and abundance of different wavelength features in the topographic or structural profile. © 1998 John Wiley & Sons, Ltd.

Joints and décollement zones in Middle Devonian shales: Evidence for multiple deformation events in the central Appalachian Plateau

Fractures in oriented Middle Devonian shale cores from the Appalachian Plateau province provide evidence for multiple deformation events associated with the Alleghanian orogeny, post-orogenic stress relaxation, and neotectonic ( ) stresses. The orientation, distribution, and mineral paragenesis of these fractures are used to establish the timing, regional extent, and stress orientation of each deformation event. During the Alleghanian orogeny, the Middle Devonian shale section was a regional decollement zone in the central Appalachian Plateau province. The decollement extends from the Appalachian Structural Front to northwestern Pennsylvania and east-central Ohio. It is defined by abundant joints, veins, and slick-ensided fractures localized within multiple zones of organic-rich brown and black shale. These zones are distributed over tens to hundreds of meters of the Middle Devonian shale section. The shale cores record a continuous counterclockwise rotation of the maximum compressive stress direction in the west-central Appalachians during the Alleghanian orogeny. Three stages are recognized. 68 refs., 10 figs., 3 tabs.

Three-dimensional folding of an embedded viscous layer in pure shear

A thick-plate analysis is carried out to first-order in interface slope for three-dimensional folding of a single linear viscous layer of thickness H and viscosity η embedded in a uniform viscous medium with viscosity η 1, Layer and medium are subject to a basic state of homogeneous pure shear with principal directions of strain-rate x and y lying in the plane of the layer. The solution is explicitly carried out for a fold perturbation in interface shape that is symmetric with respect to the principal strain-rate axes, f cos (lx) cos (my), but it is shown to apply to an arbitrary perturbation in the x,y plane. The growth rate of the perturbation is found to be ▪ are the principal strain-rates of the basic state. The wavenumber of the most rapidly growing perturbation, λ d , is the same as that obtained for a cylindrical perturbation ( m = 0) in a basic state of plane strain ϵ ̄ yy = 0) . For maximum rate of shortening parallel to x, the cylindrical fold form with axis normal to x, m/ l = 0, grows most rapidly for any ratio of ϵ ̄ yy/ ϵ ̄ xx < 1. If ϵ ̄ yy = ϵ ̄ xx all fold forms grow at the same rate and in particular, an ‘egg-carton’ fold form is not preterentially amplified. The velocity field for the perturbing flow consists of a poloidal field, which solely determines the growth of the fold form, and a toroidal field, with non-zero component of vorticity about the axis normal to the layer. The latter is required to satisfy both of the two independent shear traction continuity conditions at interfaces. There is no coupling between the two fields. Three-dimensional fold forms in the Appalachian Plateau province in western Pennsylvania are described.

Model studies of shallow common‐offset seismic data

For simplicity, optimum‐window common‐offset data‐acquisition procedures are frequently employed to collect near‐surface, high‐resolution, seismic reflection data. However, because of large incidence angles, interpretations of the data often cannot be evaluated accurately using zero‐offset simulations alone. Common‐offset hammer seismic data collected in the central Appalachian plateau province of West Virginia are examined in this paper. Synthetic shot records using a minimum‐phase wavelet estimated from the data and subsurface acoustic properties derived from full‐waveform and other geophysical logs are used to simulate the offset seismic response of near‐surface, coal‐bearing Pennsylvanian aged rocks. Zoeppritz equations are used to model amplitudes. This study indicates that offset simulations may be required to determine the origins of events observed at a given offset. Offset simulations also help determine whether amplitude variations with offset have a significant effect on the appearance of events observed at the optimum offset. The offset seismic response is significantly different from the zero‐offset response for reflections arising from depths less than about two‐thirds of the offset distance; for greater depths, zero‐offset simulations adequately approximate the offset response.

Effects of Deformation Mechanisms on Reservoir Potential in Central Appalachian Overthrust Belt

Finite strain associated with various deformation mechanisms can significantly alter the porosity and permeability of reservoir rocks in overthrust belts. Mechanisms such as pressure solution and cataclasis reduce porosity and permeability, whereas extension fracturing and brecciation increase them. A theoretical derivation of the relationship between finite strain and original and final porosity indicates that little porosity is preserved in rocks whose strain (R) exceeds 1.5. Studies of variations in the relative importance of these mechanisms are used to define regional and local variations in reservoir properties in the central Appalachian overthrust belt. Regional limits of hydrocarbon potential are defined by combining finite-strain data with thermal-maturation (con dont color alteration index or CAI) data. On the basis of these studies, I conclude that the potential for oil production is primarily restricted to the Appalachian Plateau province. The potential for gas production decreases from west to east in the Valley and Ridge and Plateau provinces, with its approximate eastern limit defined by the North Mountain thrust. Local variations in reservoir properties depend on original depositional and diagenetic fabric of the reservoir, the relative timing of different mechanisms, lithologic and textural characteristics, and structural and lithotectonic position. The possibility of retaining open fractures depends on the relative timing of fracturing and pressure solution. Fractures formed during the main phase of folding are more likely to be sealed by pressure-solved material, whereas fractures formed or reactivated late in the deformation are more likely to remain open. Lithologic units that enhance fracturing and inhibit pressure solution most likely have higher fracture and matrix porosity. Fine-grained argillaceous limestone is more susceptible to pressure solution than orthoquartzite, whereas fractu ing is more intense in brittle, thin-bedded and fine-grained units. Structural positions with high fracture potential include angular fold hinges, fault zones, and the steep forelimbs of folds. The steep forelimbs of folds also are characterized by intense pressure solution and cataclasis, which reduce porosity. Consideration of the above criteria can be useful in evaluating the reservoir potential of prospective structures in the central Appalachian and other overthrust belts.

High-Potential Gas Production and Fracture-Controlled Porosity in Upper Devonian Kane Sand,"Central-Western Pennsylvania: GEOLOGIC NOTE"

Cush Cushion field is a small gas-producing tract in central-western Pennsylvania. It lies physiographically within the Pittsburgh Plateau section of the Appalachian Plateau province. The Allegheny Front, which forms the border between the Appalachian Plateau province and the Valley and Ridge province, is 23 mi (37 km) east of the field. Cush Cushion is developed across the Brush Valley synclinal axis in eastern Indiana County. The Conemaugh Group (Pennsylvanian) is exposed at the surface, and production is from the multistory sandstone reservoirs of the Bradford Group (Upper Devonian) at depths ranging from 2600 to 3924 ft (792 to 1196 m). The Kane sand of the lower Bradford Group is the principal reservoir at Cush Cushion field. The Kane is interpreted as a distributary-channel sandstone associated with the westward progradational Catskill clastic wedge. Kane sand production is probably fracture controlled at Cush Cushion field. Surmised fracture porosities as high as 22% occur along a limited east-west trend. Natural open flow of up to 15 mmcfgpd are known from the fractured Kane interval. A zone of structural discontinuity is recognized at Cush Cushion field. Fracture porosity in the Kane may be related to the local disruption of the regional structural grain. Thismore » disruption could represent the extension of a documented cross-structural discontinuity from the overthrust belt into the undetached foreland. 7 figures, 1 table.« less

High Potential Gas Production and Fracture-Controlled Porosity in the Upper Devonian Kane Sandstone, Central-Western Pennsylvania: ABSTRACT

Cush Cushion field is a small gas-producing tract in central-western Pennsylvania. It lies physiographically within the Pittsburgh Plateau section of the Appalachian Plateau province. The Allegheny Front, which forms the border between the Appalachian Plateau province and the Valley and Ridge province, is 23 mi (37 km) east of the field. Cush Cushion is developed across the Brush Valley synclinal axis in eastern Indiana County. The Conemaugh Group is exposed at the surface and production is from the multistory sandstone reservoirs of the Bradford Group (Upper Devonian) at depths ranging from 2,600 to 3,924 ft (792 to 1,196 m). The Kane sandstone of the lower Bradford Group is the principal reservoir at Cush Cushion field. The Kane is interpreted as a distributary-channel sandstone associated with the westward progradational Catskill clastic wedge. Kane sandstone production is fracture controlled at Cush Cushion field. Fracture porosities as high as 13.8% occur along a limited east-west trend. Natural open flows of up to 13.8 MMcfgpd are known from the fractured Kane interval. A zone of structural discontinuity is recognized at Cush Cushion field. Fracture porosity in the Kane may be related to the local disruption of the regional structural grain. This disruption could represent the extension of a documented cross-structural discontinuity from the overthrust belt into the undetached foreland. End_of_Article - Last_Page 1666------------

Coal Resource Studies in Virginia: ABSTRACT

There are three coal-bearing areas of Virginia: the Richmond and Farmville Triassic basins in the Piedmont End_Page 1284------------------------------ province, the Valley coalfields in the Valley and Ridge province, and the Southwest Virginia coalfield in the Appalachian Plateau province. All present production and most coal resources are within the Southwest field. Coal production in 1978 was 32,004,341 short tons of which 31% was by surface mining methods. The Division of Mineral Resources is currently studying the geology of all of Virginia's coalfields, especially the Southwest field. For the past several years the Division has collected coal samples from the Southwest field to be analyzed by the U.S. Geological Survey and U.S. Bureau of Mines, with the results being entered into the National Coal Resources Data System. Mapping at a 1:24,000 scale is continuing on several quadrangles in the Southwest Virginia field and in parts of the Valley coalfields. The Division is compiling geologic data related to the methane potential of unminable coal beds, in cooperation with the Department of Mining and Minerals Engineering at Virginia Tech. A mine inventory for all active coal mines in Virginia has been completed. This information will be used, along with other information gathered by the Division, to revise the coal resource estimates for Wise, Lee, Dickenson, and Scott Counties. The U.S. Geological Survey will concurrently revise the resource estimates for Buchanan, Tazewell, and Russell Counties. Future work by the Division will include studies of mine-roof stability, hydrology, and geochemistry in the Southwest Virginia coalfield. In addition, we anticipate new mapping at 1:50,000 and 1:24,000 scales. Work is also planned in continuing existing sampling and mine inventory programs. End_of_Article - Last_Page 1285------------

Intensity of systematic joints: Methods and application

Intensity (joint surface area per unit volume of rock) of a multiset system of joints can be calculated from measurements of perpendicular spacings between adjacent joints in the same sets. Several estimators of intensity are easily calculated. The estimator that uses the trimean of spacings is least distorted by irregular spacing data that are observed and expected in joint systems. Such a measure of joint intensity can be used in academic, engineering, environmental, and economic geology, and in mine design. We apply it to evaluating an exposed analogue of probable fractured gas reservoirs. A field test shows that a major cross-strike structural discontinuity in the Valley and Ridge province of the central Appalachians crosses into the easternmost Appalachian Plateau province as a zone of about twice-normal intensity of systematic jointing.