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R.W. Stanton

Publications and source records attributed to R.W. Stanton.

36 records · Page 2Linked to original sources
USGS1989

Comparative facies formation in selected coal beds of the Powder River Basin

Petrologic studies of thick coal beds [Warwick, 1985; Moore, 1986; Moore and others, 1986; Moore and others, 1987; Warwick and Stanton, in press], which build on sedimentological interpretations [Flores, this volume] of associated units, provide data to interpret and contrast the varieties of peat formation in the Powder River Basin. Detailed analyses of the composition of coal beds lead to more complete interpretations regarding the depositional environment on a regional and local scale. Our efforts in the Powder River Basin [areas A-D in fig. 1 of Flores, this volume] have resulted in a series of site-specific studies that interpret the types of peat formation from the arrangement of different facies which comprise the coal beds and from the spatial form of the coal beds. Our approach was to use a combination of megascopic criteria for facies sampling, and where only core was available, to analyze many interval samples to discriminate facies by their maceral composition. Coal beds in the Powder River Basin are composed of laterally continuous, compositional subunits of the bed (facies) that can be discerned most easily in weathered highwall exposures, less readily in fresh highwalls, and very poorly in fresh-cut core surfaces. In general, very low ash (

Montana, Wyoming↗
USGS1985

Paleoclimate controls on late paleozoic sedimentation and peat formation in the central appalachian basin (U.S.A.)

In the central Appalachian basin, at least two major climate changes affected sedimentation during the late Paleozoic. Stratigraphically, these two changes are indicated by the distribution of coal beds, the variation in coal quality, and the variation in rock lithologies. In latest Mississippian or earliest Pennsylvanian time, the climate changed from dry-seasonal tropical to ever-wet (equable) tropical. The equable climate prevailed into the Middle Pennsylvanian, influencing the morphology and geochemistry in peat-forming environments. Many of the peat deposits, which formed under the equable climate, were probably domed (raised bogs); low concentrations of dissolved solids in peat formation water resulted in low buffering capacity. Organic acids caused acidic (pH < 4), antiseptic conditions that resulted in intense leaching of mineral matter, minimal degradation of organic matter, and low-ash and low-sulfur peat deposits; the resulting coal beds are also low in ash and sulfur. Associated rocks are noncalcareous and consist of sequences of interbedded shale, siltstone, and sandstone including quartz arenite. Another climate change occurred in late Middle Pennsylvanian time when evapopation periodically exceeded rainfall resulting in an increase of both dissolved solids and pH (4 to ∼ 7) in surface and near-surface water. Throughout the remainder of the Pennsylvanian, the surfaces of peat deposits were probably planar (not domed); water in peat-forming and other depositional environments became more nearly neutral. The coal beds derived from these peats are highly variable in both ash and sulfur contents. Drier or more seasonal climates are also indicated by sequences of (1) calcareous sandstone and shale, (2) nonmarine limestone that shows shallow-water and subaerial exposure features, and (3) calcareous paleosols that have caliche characteristics. Our data and observations indicate that physical depositional environment models for the origin of coal do not adequately explain variations in mineral matter content and composition in commercial quality coal beds in the central Appalachian basin. Stratigraphic variation in mineral matter in coal beds, and in syngenetic and early diagenetic minerals in rocks associated with the coal beds, appears to be better explained by changes in geochemical conditions of nonmarine sedimentation. Paleoclimate was a principle control on these geochemical conditions.

International Journal of Coal Geology↗
USGS1985

GEOLOGIC PROCESSES AFFECTING THE QUALITY OF THE UPPER FREEPORT COAL BED, WEST-CENTRAL PENNSYLVANIA.

The number or types of origins of the components of a coal bed cannot be determined from its bulk composition. Minerals such as quartz, calcite, and pyrite as well as macerals such as vitrinite can originate from a variety of processes that result from different depositional conditions. The Upper Freeport coal bed was studied and characterized by sampling and analyzing its mappable subunits (facies) over a 120-sq mi area in west-central Pennsylvania. The study was based on field description of mine faces and description of X-ray radiographs of core. A geochemical model proposed for the origin of facies of the Upper Freeport coal bed is consistent with interpretations of modern peat formation resulting from the interaction of climate, plant types, rainfall, ground water geochemistry, nutrient supply, and sedimentation. This model provides a means to evaluate and predict more precisely the variability of a coal resource's quality.

Conference Paper↗
USGS1983

RECENT DEVELOPMENTS ON THE ORIGIN OF MINERAL MATTER IN COAL.

This study attempts to quantify some of the various origins of mineral matter. Data developed for the Upper Freeport coal bed indicates that mineral matter other than pyrite and calcite is primarily derived from the vegetal matter that ultimately became coal. Cathodoluminesence was used to verify that the quartz in the Upper Freeport coal is dominantly authigenic and not detrital in origin. Sulfur variability in coal beds of the central Appalachian Basin was investigated stratagraphically.

Conference Paper↗
USGS1982

Geologic factors that control mineral matter in coal

Elements other than organically derived and bound C, H, N, O, and S constitute mineral matter in coal. Mineral matter may consist of discrete minerals such as calcite, quartz, clays, and pyrite, and/or organic compounds that contain organically bonded elements such as Ca and CI. Processes that may affect the association and content of mineral matter are operable from the initial peat-forming stage to the time of utilization of the coal. However, the objective of this paper is to discuss some of the various geologic processes that may influence content and associations in unmined coal.

Book chapter↗
USGS1982

Determination of the true density of pulverized coal samples

A method using the gas-comparison pycnometer with helium gas as the penetrating medium measures precisely the true volume of a pulverized coal sample. The true density of a solid is calculated as the true unit volume of the solid exclusive of its pore space which is divided into the weight of the sample. The method is similar to that used to determine the density of refractory materials but the procedure is modified to yield precise density determinations of coal samples. These modifications diminish effects of trapped moisture and gases on the volume measurement. The helium gas-comparison pycnometer method is rapid, reliable, precise, and requires minimal analytical equipment and sample preparation, and also is non-destructive to the coal sample. Using this method, densities can be determined on coal samples of subbituminous to low-volatile bituminous rank and perhaps also on samples of lignite. The density of anthracite samples has not been determined by this method.

Open-File Report↗
USGS1978

Identification and significance of accessory minerals from a bituminous coal

A scanning electron microscope (SEM) has been used to study the in situ accessory minerals in polished blocks and pellets of petrographically analysed samples of the Waynesburg coal (hvb). Individual grains from the low-temperature ash (LTA) of the same coal were also studied. The visual resolution of the SEM permitted the detection of submicron mineral grains, which could then be analysed by the attached energy-dispersive system. Emphasis was placed on the highly reflective grains in the carbominerite bands. Among the most abundant accessory minerals observed were rutile, zircon, and rare-earth-bearing minerals. Small (1–5 μm) particles of what may be authigenic iron-rich chromite and a nickel silicate form rims on quartz grains. The SEM also permits the observation of grain morphology and mineral intergrowths. These data are useful in determining authigenicity and diagenic alteration. Substances in density splits of LTA include authigenic, detrital, extraterrestrial magnetite, tourmaline, and evaporite (?) minerals, and a fluorine-bearing amphibole. This analytical approach allows the determination of specific sites for many of the trace elements in coals. In the Waynesburg coal, most of the chromium is in the iron-chromium rims, the fluorine is in the amphibole, and the rare-earth elements are in rare-earth-bearing minerals. The ability to relate trace-element data to specific minerals will aid in predicting the behaviour of elements in coal during combustion, liquefaction, gasification, weathering, and leaching processes. This ability also permits insight into the degree of mobility of these elements in coal and provides clues to sedimentological and diagenetic conditions.

Pennsylvania↗