Observations on the palynology, petrography and geochemistry of the Western Kentucky number 4 coal bed

Eight bench-column samples of the Western Kentucky Number 4 coal bed, colle cted from an area along the southern margin of the Western Kentucky Coal Fi eld, were analyzed palynologically, petrographically, and geochemically to document both temporal and spatial variability among these parameters. The Western Kentucky Number 4 coal occurs near the top of the Tradewater Format ion, is of Early Desmoinesian age, and is correlative with the lower part o f the Allegheny Formation of the Appalachian Basin, and Late Bolsovian stra ta of western Europe. Palynologically, the coal is co-dominated by spores t hat were produced by lycopod trees (Lycospora and Granasporites medius) and tree ferns. Thin-walled tree fern spores (Punctatisporites minutus, P, min utus, P. rotundus) are more abundant than thick-walled forms (Laevigatospor ites globosus, P. granifer). Calamitean spores (Calamospora and Laevigatosp orites spp.) are locally abundant as is cordaitean pollen (Florinites). Sma ll fern (Granulatisporites) and small lycopod spores (Densosporites, Cirrat riradites, Endosporites and Anacanthotriletes spinosus) are present, but oc cur in minor amounts. Temporal changes in palynomorph composition occur, bu t are not uniform between columns. Spatial variability among columns is als o evident. Petrographically, the coal is dominated by vitrinite macerals, w ith telinite and telocollinite generally occurring more commonly than desmo collinite and gelocollinite. Basal benches typically contain high percentag es of vitrinite; middle benches usually contain higher percentages of lipti nite and inertinite. In about half the studied columns, the terminal coal b enches show a slight increase in vitrinite. In the study area, the petrogra phy of the Western Kentucky Number 4 coal is more uniform than the palynolo gy. Ash yields and total sulfur contents are temporally uniform in some col umns, but variable in others. In the latter case, higher percentages of ash and sulfur occur at the base of the bed and decrease up to the middle of t he bed. The terminal benches of these columns often, but not always, show s light increases in ash or sulfur. Both syngenetic and epigenetic forms of s ulfur are present in the Western Kentucky Number 4 coal. The high vitrinite contents and moderate to high sulfur contents suggest that the Western Ken tucky Number 4 paleomire was mainly planar and rheotrophic throughout its d evelopmental history. Groundwaters carrying dissolved solutes may have help ed neutralize the normally acidic interstitial peat waters allowing for the production of sulfide minerals. Several of the columns with high sulfur co ntents at the base of the bed occur in faulted areas. The faults could have promoted the flow of groundwaters through the peat, providing an increased dissolved load for acid mitigation and sulfide formation. The concentratio n of sulfur at the base of the bed may be a function of the peat/underclay contact enhancing sulfide formation. The clay layer may also have acted as an impermeable boundary for downward moving groundwaters, causing mainly la teral, rather than vertical movement along the base of the coal bed. (C) 19 99 Elsevier Science B.V. All rights reserved.