Susan M. Rimmer

Geochemistry of the blue gem coal bed, Knox county, Kentucky

Abstract The Blue Gem coal bed (Middle Pennsylvanian Westphalian B, Breathitt Formation), has low-ash (with some sample sites having less than 1% ash) and low-sulfur contents through parts of Knox County, Kentucky. Most collection sites exhibit similar vertical elemental trends in ash geochemistry. The relatively high-ash (>1% ash) lower part of the bed displays enrichment in TiO2, Zr, Cr, V and Ni; Co, Zn, Rb and Mn show enrichment at some sites. A low-ash ( 1% ash and a relative enrichment in SiO2, K2O and Rb and a relative decrease in Cu, Ni, Co, Ba and Mn when compared to the middle part of the bed. Principal components analysis indicates that the samples with an ash content 0.63–1.0% show associations for Ni, Cu, Cr and Co. Samples with between 1.01–2.0% ash display strong element associations that suggest increased clastic sediment contributions (TiO2, Zr, K2O, Rb, SiO2). The low-ash content and the upwards decrease in trace concentrations both suggest that the Blue Gem peat swamp was ombrotrophic through at least a part of its geologic history.

Coal rank trends in the Central Appalachian coalfield: Virginia, West Virginia, and Kentucky

Abstract Coal rank, determined from vitrinite maximum reflectance and from chemical rank parameters, increases from high volatile C bituminous in portions of the Eastern Kentucky coalfield to low volatile bituminous in Buchanan County, Virginia, and McDowell County, West Virginia, and then decreases significantly to the Dry Fork anticline, 20 km to the southeast. The latter rank decrease, as noted when rank data from individual coals is used across the fold (400–500 m structural relief), can be accounted for by post-tectonic coalification at a paleogeothermal gradient of about 40–45°C/km. Reflectance gradients decrease from about 0.09% Rmax /100 m in central Buchanan County, Virginia, to 0.06% Rmax/100 min southeastern Pike County, Kentucky, to 0.03% max/100 m and less among the high volatile A and B coals to the nortwest of Pike County. The reflectance gradients are likely an indication of a decrease in paleogeothermal gradient to the northwest. Depth of burial may have also decreased to the northwest. Northward-trending rank anomalies superimposed on the regional trend in Kentucky may have been caused by subtle changes in the geothermal gradients associated with basement discontinuities or, alternately, by a depth of burial not accounted for at present, perhaps under now-eroded thrust sheets.

The influence of depositional environments on coal petrographic composition of the Lower Kittaning seam, western Pennsylvania

Abstract Lateral variations in maceral composition of the Lower Kittanning seam can be explained in terms of differential preservation of plant materials, which is influenced by the pH/Eh of water within the peat swamp and by the rate of subsidence. Within the central part of the basin, high telocollinite contents are observed; this type of vitrinite represents large, well-preserved pieces of woody tissue whose preservation was favored by rapid burial. Towards the margins of the basin, high desmocollinite contents are seen; slower burial, combined with the influx of neutral, oxygenated fresh water permitted decomposition of the precursor materials, producing this highly degraded type of vitrinite. Vertical variations in telocollinite and desmocollinite content can also be related to burial rates and pH/Eh conditions within the swamp. Throughout the basin, high telocollinate contents observed in the lower part of the seam resulted from rapid burial under relatively low pH conditions. Continued high rates of subsidence led to an influx of neutral pH, oxidizing waters associated with the encroaching marine environment. Under these new conditions, more degradation of plant tissues occurred, producing the high desmocollinite contents observed in the upper part of the seam. This effect was most pronounced in the center of the basin. An alternative explanation would be a change in vegetation type in response to the changing conditions; the high desmocollinite content would then reflect a shift to a community dominated by smaller, possibly herbaceous, plants. In addition to a change in vitrinite type towards the top of the seam, a decrease in total vitrinite content, and increases in total liptinite and inertinite contents are observed. The increase in liptinite content is due to either (1) the higher resistance to decomposition of liptinite precursor materials (when compared to vitrinite precursors) in the more neutral conditions, or (2) a change from a dominantly arborescent vegetation to a more herbaceous one. The increase in inertinite results from an increase in transported material (inertodetrinite) and/or an increase in the formation of inertinite macerals, such as degrado-fusinite, possibly in response to the encroaching marine conditions. An additional control on maceral composition is the level of metamorphism of the coal. Total liptinite content decreases towards the southeast; in this area, the coal has attained a sufficiently high rank that the reflectance of liptinite macerals approaches that of vitrinite, thus making their identification difficult.

Rock-eval pyrolysis and vitrinite reflectance trends in the Cleveland Shale Member of the Ohio Shale, eastern Kentucky

Within eastern Kentucky, organic petrographic and geochemical data indicate a southeastwards increase in maturation of the Cleveland Shale Member of the Ohio Shale (Devonian-Mississippian). Reflectance levels of dispersed organic material in the Cleveland Shale increase from 0.5% in the outcrop belt in central Kentucky, to slightly over 1.0% in Pike County, eastern Kentucky. A decrease in fluorescence intensity of liptinitic components, such as Tasmanites, accompanies this reflectance increase, as does a shift in fluorescence color of the alginite towards the red. In the highest rank areas, fluorescence is almost absent. Groundmass fluorescence is observed also, and follows trends similar to those shown by the alginite. Kerogen in the Cleveland Shale is primarily Type II, as indicated by petrographic observations and Rock-Eval data. Total organic carbon contents of this shale decrease from over 12% in the outcrop belt, to less than 2% in the eastern-most part of the study area. Source rock potential ranges from good to very good, with the highest potentials occurring in the outcrop belt. Tmax values for this unit increase from under 430°C in the outcrop belt to over 450°C in the southeast, confirming the increase in maturation trends indicated by vitrinite reflectance data. Both petrographic and geochemical maturation parameters place the Cleveland Shale of eastern Kentucky within the oil window. Comparison with maturation data for Pennsylvanian-age coals upsection suggests that maturation indices are retarded, or suppressed, in the Devonian shales. The level of maturation indicated for the Cleveland may be problematical considering that the Ohio Shale is a major gas-producer in this area.

Petrography and palynology of the Blue Gem coal bed (Middle Pennsylvanian), southeastern Kentucky, USA

Petrographic and palynological trends in the Blue Gem coal bed (Middle Pennsylvanian Westphalian B, Breathitt Formation), a thin, low-sulfur, low-ash coal in southeastern Kentucky, were studied in order to establish a depositional model for the seam. Within the study area, the coal bed averages 67 cm and has two distinct zones. The lower and middle parts of the seam (the lower 45–55 cm) are enriched in well-preserved vitrinite and are dominated by arborescent lycopods, sphenopsids, and tree ferns. Fusinite-rich layers, dominated by arborescent lycopods, but also containing herbaceous lycopods and sphenopsids, occur within the lower and middle parts of the seam. The upper part of the seam (the upper 15–25 cm) is recognizable in the field and is distinct in that it contains a greater amount of degraded macerals, and is characterized by high palynomorph diversity, primarily by miospores that are associated with sphenopsids, herbaceous lycopods and arborescent lycopods. These data, in conjunction with geochemical data available for the seam, suggest that initially the peat swamp was fairly diverse and well-nourished (the base of the seam being characterized by a relatively diverse miospore assemblage and a slightly higher ash content). Following this initial planar stage, the Blue Gem peat swamp was probably planar to slightly domed during accumulation of most of the lower and middle parts of the seam, as suggested by the very low ash and sulfur contents, the high telovitrinite content, and the preponderance of arborescent lycopod spores. In its final stages, the peat swamp was domed and is characterized by a more diverse flora and greater levels of degradation of the peat constituents. Sulfur content of this seam is generally low (<1%) but can increase locally to 3–4%. Factors influencing sulfur content include the thickness and nature of the overburden (shale versus sandstone) and petrographic composition.

Organic petrography of Mississippian and Devonian shales in east-central Kentucky

The Devonian and Mississippian oil shales of east-central Kentucky are classified as marinites. The petrographic composition of the kerogen in the shales is complex, and significant amounts of macerals from all of the major groups are present. Unfigured alginite (lamalginite) and bituminite are the most abundant macerals present, followed by vitrinite and inertinite (fusinite and semifusinite). Figured alginite (telalginite) includes Leosphoridia and Tasmanites; a minor amount of sporinite (~1% or less) is also present. The maceral composition of the Cleveland and Sunbury Shale interval from a core taken in Fleming County, Kentucky was determined quantitatively. The liptinite suite in the Sunbury interval was dominated by bituminite, while the Cleveland contained higher proportions of alginite. The total amount of inertinite plus vitrinite was found to be relatively constant. Variations in maceral composition affect the scatter of Fischer assay oil yield versus organic carbon relations for Eastern US oil shale. The kerogen macerals were found to correlate selectively with certain trace elements (e.g. Cr, Cu, V and Zn), suggesting that the maceral composition may be related to shale provenance. Bituminite:alginite ratio was found to correlate selectively with trace element concentration and supports the concept that the organic precursors for this maceral were bacterial decay products.

Distributions and associations of selected trace elements in the lower Kittanning seam, western Pennsylvania, U.S.A.

Abstract Trace elements within the Lower Kittanning seam (western Pennsylvania) show significant basinal variations. Many of these variations can be related to differences in the depositional environments of the peat, as inferred by the nature of the overlying shales, in that the distribution of minerals in this seam, particularly that of clay minerals, is controlled by depositional environment. Chromium, Cu, V and Zr show significant increases towards the northwestern and southeastern margins of the basin. These trends can be explained by an association with clay minerals (Cr, V, and, in part, Cu), or with minor amounts of other detrital minerals (Zr). Clay composition of the Lower Kittanning seam reflects proximity to the sediment source and stability of the various clay minerals in the swamp environment. Kaolinite, which increases in concentration towards the basin margins, is primarily authigenic and shows a distribution that reflects the stability of this mineral in the relatively low pH, freshwater areas of the peat swamp. In this seam, illite-mica is predominantly detrital, as inferred by polytype studies, and increases along isolated sections of the basin margins where a greater detrital influx was experienced. Within the Beryllium and Ni also increase towards the basin margins. These elements may have been trapped at the margins of the basin by the organic fraction of the peat or coal. Similarly, Cu may owe its distribution, at least in part, to organic trapping. A decrease in Be content along the southeastern margin of the basin may be due to the increase in coal rank observed in that area. No basin-wide trends were seen for Ba, Mn and Zn and their concentrations are controlled by local mineral occurences. Manganese variations, for example, can be related to local occurrences of siderite.

Constraints on the Emplacement and Uplift History of the Pine Mountain Thrust Sheet, Eastern Kentucky: Evidence from Coal Rank Trends

In this paper coal rank trends on both sides of the Pine Mountain thrust in eastern Kentucky are used to place constraints on thrust evolution. Vitrinite reflectance (\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage{wasysym} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document}

Latest Permian chars may derive from wildfires, not coal combustion

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