Geology topics

W.M. Andrews

Publications and source records attributed to W.M. Andrews.

3 recordsLinked to original sources

USGS2002

Multiple-bench architecture and interpretations of original mire phases - Examples from the Middle Pennyslvanian of the Central Appalachian Basin, USA

Coal seams often exhibit lateral and vertical variability in composition. When sampled as a whole seam this variability is masked. But if a seam is subdivided into correlateable components, this variability can be tested and better understood. Herein, an architectural approach is used to divide seams into intra-seam components. Clastic splits and mineral partings, as well as persistent fusain and durain layers, can be used as intra-seam bounding units to subdivide a seam into subdivisions called benches. Regional examination of Lower and Middle Pennsylvanian-age coal seams shows that many contain laterally persistent bounding surfaces that can be used to define multiple benches of coal within each seam. Inter-bench analyses from some of the most extensively mined seams in the central Appalachian Basin show that individual benches often have different spatial and quality trends. Hence, some component of whole-seam variability is a function of changes in the relative contribution of these different benches to the seam as a whole. Many coal benches also exhibit intra-bench variation in coal parameters. Intra-bench variation can be analyzed in terms of parameters such as sulfur content and ash yield in order to address changes in coal quality for regional resource evaluation. Intra-bench variation can also be analyzed in terms of a combination of palynologic, petrographic, and geochemical parameters, termed compositional groups, in order to better understand the development of the original mire systems. Compositional groups are defined by ranges of multiple criteria, which are inferred to owe their origin to the mire type in which they formed. Vertical changes in compositional groups within coal benches can be used to infer paleo-edaphic conditions during peat accumulation. If seam thickness is a product of bench configuration, and trends in compositional groups occur in benches, then trends in quality can be marginally predicted based upon seam thickness and inferred bench architecture. Additionally, changes in inter-bench and intra-bench thickness and compositional profiles can be used to infer original depositional controls, such as paleotopography, syndepositional structural movement, and syndepositional clastic influx for more accurate reserve estimates. ?? 2002 Elsevier Science B.V. All rights reserved.

International Journal of Coal Geology↗

USGS1996

A depositional model for the Taylor coal bed, Martin and Johnson counties, eastern Kentucky

This study investigated the Taylor coal bed in Johnson and Martin counties, eastern Kentucky, using field and petrographic techniques to develop a depositional model of the coal bed. Petrography and chemistry of the coal bed were examined. Multiple benches of the Taylor coal bed were correlated over a 10 km distance. Three sites were studied in detail. The coal at the western and eastern sites were relatively thin and split by thick clastic partings. The coal at the central site was the thickest and unsplit. Two major clastic partings are included in the coal bed. Each represents a separate and distinct fluvial splay. The Taylor is interpreted to have developed on a coastal plain with periodic flooding from nearby, structurally-controlled fluvial systems. Doming is unlikely due to the petrographic and chemical trends, which are inconsistent with modern Indonesian models. The depositional history and structural and stratigraphic setting suggest contemporaneous structural influence on thickness and quality of the Taylor coal bed in this area.

International Journal of Coal Geology↗

USGS1994

Paleoecology of the Fire Clay coal bed in a portion of the Eastern Kentucky Coal Field

Vertically continuous increment samples of the Fire Clay coal bed (mid-Middle Pennsylvanian, late Westphalian B), collected from a portion of the Central Appalachian Basin, were studied palynologically, petrographically and geochemically in order to partially reconstruct the paleoecology and processes associated with peat formation in the ancient Fire Clay paleomire. Results indicate that four compositional groups can be identified. They are: (1) a Lycospora —vitrinite dominant group, characterized by high percentages of Lycospora and vitrinite macerals and generally low, but variable ash yields and sulfur contents; (2) a mixed palynoflora-high vitrinite group that petrographically is similar to group 1 except that it contains a more diverse palynoflora; (3) a mixed palynoflora-moderate/low vitrinite group characterized by various admixtures of lycopsid, fern and calamite miospores, increased percentages of liptinite and inertinite macerals, and low ash yields and sulfur contents; and (4) a mixed palynoflora-high ash yield group characterized by high percentages of small lycopsid, fern, and occasionally calamite and cordaite miospores, high liptinite and inertinite contents, high ash yields, and moderate to high sulfur contents. The Fire Clay coal bed contains a distinctive flint clay parting of probable volcanic origin that naturally divides the bed into two benches. These two benches, (upper and lower), are highly disparte in occurrence, appearance and composition. In the study area the lower bench generally is thin (< 0.5 m), laterally discontinuous and mainly composed of dull (mainly durain) coal lithotypes. Ash yields typically are high; sulfur contents generally are moderate to high. Compositional group 4, the mixed palynoflora—high ash yield group defines all of the increments examined from the lower bench. In contrast, the upper bench is thick (> 0.75 m), laterally continous and mainly comprised of bright (mainly clarain) coal lithotypes. Overall ash yields and sulfur contents for this bench are generally low, although vertical variation is apparent. All of the compositional groups occur in the upper bench; in some columns, notably those that are thick and uninterrupted by clastic partings, groups 1 and 4 often occupy basal coal layers and groups 2 and 3 occur in higher layers. Other columns, especially those taken in areas of thin (< 0.5 m) Fire Clay coal, are dominated by groups 1 and 4.

Kentucky↗