Further examination of the ragged edge of the Herrin Coal Bed, Webster County, Western Kentucky Coal Field

Ž .International Journal of Coal Geology 46 2001 145–155www.elsevier.comrlocaterijcoalgeo

Further examination of the ragged edge of the Herrin Coal Bed,Webster County, Western Kentucky Coal Field

James C. Hower a,), David A. Williams b

a UniÕersity of Kentucky Center for Applied Energy Research, 2540 Research Park DriÕe, Lexington, KY 40511, USAb Kentucky Geological SurÕey, Henderson, KY 42420, USA

Abstract

Ž .The Herrin Western Kentucky No. 11 coal bed in the Dixon 7 1r2 min quadrangle, Webster County, Kentucky,displays another manifestation of the thinning margin of the coal bed. Previous studies in adjacent Hopkins County havedemonstrated that the coal is brecciated as the margin is approached. The brecciated coal is not always thin; 1.5 m ofbrecciated, inertinite-rich coal was previously described to the southeast of the present study area. In general, the brecciated

Ž .coals are considerably thinner than the 1.5–2-m-thick, AnormalB Herrin coal. Both cores studied are thin 22.6 and 33 cmand display petrographic characteristics different from thicker Herrin coals. The cores described in the present study showsome signs of brecciation; in certain cases, the fragmented macerals are cemented by exsudatinite. Multiple generations ofpyrite mineralization were noted in one core, with total sulfur exceeding 13% in the upper 8.48 cm lithotype.

Overall, the cores investigated in this study, along with examples from previous studies, illustrate the progression of theHerrin coal from its absence, either through nondeposition or erosion, through thin, brecciated coals, to mineable coals. Noother economic coal in western Kentucky shows as many examples of the depositional edge as does the Herrin. All of theexamples studied are from cores, emphasizing the need to study more than just the thick, mineable coals if the total extent ofthe coal body is to be understood. q 2001 Elsevier Science B.V. All rights reserved.

Keywords: Kentucky; Coal; Petrology; Geochemistry; Herrin coal; Illinois basin

1. Introduction

Few coals have revealed such a wide array ofŽ .boundaries as the Herrin Western Kentucky No. 11Ž .coal bed. Hower et al. 1987 and de Wet et al.

Ž .1997 documented several areas where the coalpassed from a mineable thickness to no coal within atransition zone about one kilometer in width. In theprevious papers, such a transition was referred to asthe Aragged edgeB of the Herrin due to the breccia-

) Corresponding author. Tel.: q1-859-257-0261; fax: q1-859-257-0360.

Ž .E-mail address: [email protected] J.C. Hower .

tion of the coal. The Herrin transition is similar toŽthe depositional boundary of the Paradise Western

.Kentucky No. 12 coal bed, a few meters above theŽ .Herrin, as described by Austin 1979 .

In this study, we add another location to the list ofHerrin ragged edges with a study of the petrologyand geochemistry of the coal in the Dixon 7 1r2 minquadrangle, Webster County, Kentucky. The studyarea is small, two sites 3.45 km apart; however,along with the sites discussed in the previous studies,the opportunity to study the nature of the margin of acoal is worthwhile. Western Kentucky, and the Illi-nois Basin, in general, does not have an abundanceof road cut or natural exposures as do the Ap-

0166-5162r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved.Ž .PII: S0166-5162 01 00017-9

( )J.C. Hower, D.A. Williamsr International Journal of Coal Geology 46 2001 145–155146

palachian coal fields. Economic coals, such as theHerrin, are well exposed in mines; however, miningis halted before the coal diminishes to the thick-nesses seen here. Only in cores have we foundevidence of the nature of the margins of the Herrincoal body.

2. Previous studies

Ž .Hower et al. 1987 described two sites where theHerrin coal bed was too thin or too brecciated and

Ž .mineralized to be mineable Fig. 1 . The coal in theŽ .Gil-21 core, as described by Hower et al. 1987 in

Ohio County is thin, with a brecciated durain orŽcannel lithology in the upper 9.8 cm of coal split by.7.5-cm-thick claystone parting, the Blue band .

ŽThe so-called Hopkins County core Hower et al.,.1987 consists of more than 1.5 m of coal with a

claystone parting, the characteristic ABlue bandB ofthe Herrin coal bed, in the lower third of the coal bedand a 3.1 cm fossiliferous limestone parting in theupper third of the coal bed. The coal is brecciatedthroughout the core, with massive fusinite and semi-fusinite dominating the maceral assemblages. Ce-menting the coal fragments is a carbonate-rich ma-

Žtrix based on petrographic observation; supported.by CaO content, see Table 1 . The lower portion of

Fig. 1. Location of Herrin coal bed Aragged edgeB study sites inthe Western Kentucky coal field. The AHopkins County coreB is

Ž .from Hower et al. 1987 , the Nebo quadrangle sites are from deŽ .Wet et al. 1997 , and the Dixon quadrangle sites are from this

study.

the coal is characterized by a Mg–Fe–Mn carbonate.Mg–Fe–Mn contents diminish to the top of the coalbed.

The Herrin coal bed thins from about 2 m to zerothickness in a distance of about 1 km in the Nebo 71r2 min quadrangle in western Hopkins County.The organic petrology and ash geochemistry was

Ž . Ždescribed at six sites by de Wet et al. 1997 see.Table 2 . Cores from potentially mineable areas, up

to 2 m thick, were not made available for study. Thesites, in order of increasing complexity, pass from a1.03 m section that is limited to 31 cm coal above

Ž .the Blue band core 199 ; to several thin coals withŽ .no Blue band cores 179 and 180 ; to progressivelyŽ .brecciated coals cores 193 and 197 ; to a brecciated,

Ž .fusinized coal core 181 . The contrast between cores197 and 181 illustrates the transitional nature of theboundary. The lower 4 cm of core 197 representsAnormalB Herrin coal, with 87% vitrinite and 2.45%pyritic sulfur. The middle 7 cm has nearly equalamounts of fusinite and semifusinite. Pyritic sulfurdrops to 0.66%, indicative of the oxidizing environ-ment of deposition. The upper 8.31 cm is dominatedby fusinite. The entire thickness of core 181 isdominated by fusinite. The inertinite-dominatedlithotypes also have a carbonate matrix with a rela-tively high concentration of Mn. Overall, de Wet et

Ž .al. 1997 described a complex story of the develop-ment of both the coal and the overlying carbonates inthis particular marginal setting.

3. Procedure

Cores of the Herrin coal were obtained from twoboreholes in the Dixon 7 1r2 min quadrangle, Web-ster County, KY. The coal cores were describedmegascopically and split into multiple benches. Eachsubsequent bench was crushed for petrographic andchemical analyses, all conducted at the Center forApplied Energy Research. Petrographic analysis wasconducted on polished pellets of epoxy-bound minus20 mesh particles using reflected-light, oil-immer-sion microscopy at a final magnification of 500= .Proximate and ultimate analyses were conducted fol-lowing ASTM procedures. Major oxides and a suiteof minor elements were analyzed by X-ray fluores-cence following techniques described by Hower and

( )J.C. Hower, D.A. Williamsr International Journal of Coal Geology 46 2001 145–155 147

Table 1Ž .Ash chemistry of Hopkins County core coal samples discussed by Hower et al. 1987

Ž . Ž .Sample Bench Thickness Ash S total XRF %, ashŽ . Ž . Ž .cm dry dry MgO Na O Fe O TiO SiO CaO K O P O Al O SO2 2 3 2 2 2 2 5 2 3 3

7866 1r10 17.60 27.25 2.66 1.10 0.51 5.27 0.21 30.57 37.19 0.60 0.64 7.08 14.80Ž .top

7867 2r10 12.75 40.46 2.14 0.73 0.63 4.17 0.59 48.23 21.75 0.53 0.14 13.11 8.007868 3r10 9.58 32.87 2.94 1.30 0.63 7.61 0.35 44.09 18.32 1.00 0.78 8.07 15.607869 4r10 11.00 15.33 4.24 0.55 0.45 20.38 0.21 28.09 22.08 0.53 1.96 5.62 19.107870 5r10 17.93 18.18 4.05 1.60 0.32 16.70 0.21 14.77 27.57 0.45 0.05 4.61 31.607871 6r10 18.69 31.90 3.01 7.14 0.47 14.31 0.17 21.59 29.73 0.47 0.58 4.06 19.707872 7r10 22.10 38.40 3.06 7.73 0.55 11.93 0.21 27.98 27.07 0.68 0.07 6.65 16.507873 8r10 17.70 51.22 2.20 15.42 0.50 10.79 0.11 11.19 47.92 0.29 0.05 3.60 9.177874 9r10 15.06 39.63 1.76 10.69 0.53 12.88 0.13 23.14 34.14 0.47 0.26 5.37 8.607875 10r10 9.88 38.32 2.37 10.45 0.48 12.66 0.13 21.86 33.42 0.46 0.26 5.28 13.70

Ž . Ž .Sample Bench Thickness Ash S total XRF ppm, ashŽ . Ž . Ž .cm dry dry Mo Zn Cu Ni Co Cr Ba V Mn Rb Sr Zr

7866 1r10 17.60 27.25 2.66 42 227 6 97 23 63 238 167 1499 46 385 109Ž .top

7867 2r10 12.75 40.46 2.14 48 14 31 56 17 61 260 107 1930 35 232 1627868 3r10 9.58 32.87 2.94 121 240 13 91 22 126 271 155 1680 59 278 1187869 4r10 11.00 15.33 4.24 72 26 52 67 36 85 228 140 1380 27 415 3337870 5r10 17.93 18.18 4.05 43 33 16 8 28 24 142 58 2186 30 149 1777871 6r10 18.69 31.90 3.01 87 8 25 15 29 21 307 50 5141 35 247 737872 7r10 22.10 38.40 3.06 76 19 1 35 28 14 281 58 4851 45 322 867873 8r10 17.70 51.22 2.20 25 5 42 41 32 83 219 130 4890 49 395 1227874 9r10 15.06 39.63 1.76 98 154 0 22 29 0 154 58 5400 18 565 907875 10r10 9.88 38.32 2.37 47 246 13 54 34 24 220 38 5464 28 457 88

Ž . Ž .Major oxides % and minor elements parts per million both on ash basis. Chemistry not previously published.

Ž .Bland 1989 . Additional trace elements were ana-lyzed by inductively coupled plasma-mass spec-

Ž .troscopy ICP-MS following procedures outlined byŽ .Meier et al. 1996 .

4. Discussion

The Herrin coal is at the top of the CarbondaleŽ . Ž .Formation Westphalian D Fig. 2 . ANormalB sec-

tions of the Herrin and Paradise coal beds, as minedthrough central Hopkins, Muhlenberg and Ohiocounties, total to about 4 m of coal. The two coalshave nearly equal thicknesses within 6 m coal–limestone–coal sequences. To the north, the Paradisecoal thins, progressively losing benches from the top

Ž .of the coal. Austin 1979 described marine shalepartings bearing marine fossils within the coal. Such

partings eventually merge with the identical roofrock as the coal vanishes. The limestone parting in

Ž .the Herrin coal, as described by Hower et al. 1987 ,is similar to the limestone roof of the Herrin. TheHerrin coal, through the progressive north- to north-westward loss of the top lithotypes, thins via muchthe same mechanism as the Paradise coal. Complicat-ing the demise of the Herrin coal is the brecciation

Žobserved in the previous studies Hower et al., 1987;.de Wet et al., 1997 , a feature observed at one

Ž .Paradise coal site Austin, 1979 .Ž .Rogers 1985 mapped the northward thinning of

the Herrin coal bed to a zero edge in much of theNebo 7 1r2 min quadrangle to the south of thepresent study area. The thin coals in cores 623 and668, with coal plus partings thicknesses of 22.6 and33.0 cm, respectively, demonstrate that the Dixon 71r2 min quadrangle sites are north of the Azero-

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Table 2Ž .Ash chemistry and organic petrology of coal samples from Nebo quadrangle sites discussed by de Wet et al. 1997

Ž . Ž .Core Sample Bench Thickness Ash S total S pyritic Vitrinite Fusinite Semifusinite Micrinite Macrinite LiptiniteŽ .cm

Ž .181 71544 1r3 top 9.40 66.39 1.06 0.48 0.5 96.1 0.9 0.0 2.4 0.171543 2r3 8.38 45.13 1.22 0.22 0.0 97.1 1.6 0.0 1.3 0.071542 3r3 12.70 53.24 1.29 0.31 0.0 91.3 3.0 0.1 5.1 0.5

Ž .197 71627 1r3 top 8.31 37.24 1.38 0.70 0.1 50.0 48.5 0.0 1.3 0.171628 2r3 7.01 36.76 1.73 0.66 5.9 4.8 86.5 0.8 0.0 2.071629 3r3 3.99 22.42 4.56 2.45 87.3 5.6 2.6 0.2 0.0 4.3

Ž .179 71630 1r3 top 9.80 13.12 3.48 1.51 83.2 7.8 6.0 0.5 0.0 2.571631 2r3 13.00 21.69 9.67 4.01 82.7 10.0 4.4 0.3 0.1 2.571632 3r3 14.10 9.30 2.45 0.63 91.5 2.9 2.4 0.3 0.1 2.8

Ž .180 71660 1r3 top 10.01 14.01 2.91 1.09 87.6 4.6 4.0 0.3 0.2 3.371661 2r3 12.29 8.48 2.08 0.54 94.7 1.5 1.2 1.1 0.0 1.571662 3r3 13.49 8.98 2.82 0.95 89.5 3.3 2.3 0.4 0.0 4.5

Ž .193 71633 1r4 top 13.11 33.75 2.57 1.19 68.5 23.4 6.5 0.0 0.1 1.571634 2r4 8.00 14.65 2.57 0.86 94.1 2.7 1.0 0.5 0.0 1.771635 3r4 9.50 16.26 2.71 0.93 85.3 4.9 4.8 0.9 0.2 3.971636 4r4 6.71 24.59 11.03 6.32 84.6 6.0 6.6 0.5 0.0 2.3

Ž .199 71643 1r4 top 30.99 12.45 4.39 2.46 85.7 5.4 5.2 0.6 0.0 3.171644 2r4 19.05 10.44 6.22 4.64 90.6 3.7 3.4 0.3 0.0 2.071645 3r4 30.48 20.81 12.44 11.16 83.6 6.2 8.0 0.1 0.0 2.171646 4r4 26.16 11.83 2.38 0.74 92.4 2.6 3.0 0.1 0.0 2.1

Core Sample Bench SO MgO Na O Fe O TiO SiO CaO K O P O Al O3 2 2 3 2 2 2 2 5 2 3

Ž .181 71544 1r3 top 4.01 0.97 0.83 3.28 0.56 53.92 19.77 2.14 0.41 13.2671543 2r3 7.51 1.18 0.46 2.46 0.15 32.87 47.85 0.43 0.19 5.3471542 3r3 6.48 1.02 0.58 2.29 0.32 38.92 37.36 1.04 0.85 9.34

Ž .197 71627 1r3 top 8.27 0.56 0.51 3.52 0.18 39.48 36.84 0.21 0.42 6.5771628 2r3 8.84 0.42 0.27 3.92 0.16 64.89 16.12 0.45 0.06 3.6871629 3r3 11.74 0.60 0.12 19.50 0.48 49.73 8.08 0.99 0.10 6.46

Ž .179 71630 1r3 top 1.95 0.41 0.41 20.89 1.00 52.46 2.40 1.65 0.05 17.6471631 2r3 0.80 0.52 0.34 44.96 0.63 38.90 0.79 1.40 0.03 10.7871632 3r3 2.39 0.89 0.47 14.22 0.91 57.78 2.78 2.49 0.05 18.08

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Ž .180 71660 1r3 top 1.99 0.86 0.36 12.98 0.84 57.97 2.50 2.22 0.04 18.5471661 2r3 3.90 0.69 0.54 10.65 0.83 61.70 5.15 2.07 0.04 16.4171662 3r3 0.59 0.63 0.36 17.50 0.77 56.73 1.25 2.15 0.04 17.22

Ž .193 71633 1r4 top 5.89 0.40 0.35 7.95 0.30 71.00 4.84 0.65 0.04 77.0071634 2r4 2.91 0.51 1.06 12.59 0.57 65.92 3.11 1.42 0.04 11.0971635 3r4 2.41 0.61 0.46 12.97 0.62 64.50 2.64 1.88 0.04 13.0171636 4r4 2.36 0.41 0.34 45.38 0.54 36.12 2.64 1.45 0.48 9.65

Ž .199 71643 1r4 top 0.76 0.77 0.39 30.06 0.88 46.97 0.97 1.71 0.12 15.9371644 2r4 1.81 0.25 0.28 59.24 0.54 25.72 2.07 0.65 0.04 8.1171645 3r4 0.74 0.18 0.29 71.04 0.32 18.33 1.07 0.62 0.04 6.1371646 4r4 8.18 0.65 0.41 10.78 0.73 51.83 7.93 1.95 0.49 15.41

Core Sample Bench Mo Zn Cu Ni Co Cr Ba V Mn Rb Sr Zr

Ž .181 71544 1r3 top 0 270 73 82 19 324 323 312 920 170 640 30771543 2r3 1 097 72 70 19 307 72 254 2030 22 1230 19471542 3r3 9 1920 70 159 27 466 210 392 1340 71 1330 235

Ž .197 71627 1r3 top 468 43 69 184 19 262 284 179 2630 13 2910 28171628 2r3 550 129 72 198 16 257 940 325 1220 50 352 22571629 3r3 184 1320 270 930 39 690 279 1760 770 87 155 1480

Ž .179 71630 1r3 top 88 141 294 465 40 413 630 870 300 154 292 86071631 2r3 0 8750 382 342 18 243 421 208 52 80 56 9371632 3r3 13 316 276 540 40 354 740 367 380 233 428 496

Ž .180 71660 1r3 top 10 425 186 468 39 408 870 452 199 165 190 39871661 2r3 26 358 219 167 40 412 810 443 408 135 330 23671662 3r3 14 0 305 0 44 440 820 339 339 139 278 403

Ž .193 71633 1r4 top 221 213 110 242 20 214 690 264 373 78 268 54071634 2r4 7 1030 192 540 30 239 1990 215 303 142 288 22771635 3r4 4 163 216 305 29 268 920 197 316 187 246 24871636 4r4 0 184 439 282 19 266 276 339 248 74 134 217

Ž .199 71643 1r4 top 358 690 288 930 39 670 1620 1230 410 122 164 51071644 2r4 0 152 443 250 0 414 1570 630 201 28 121 14471645 3r4 0 164 380 45 0 199 220 168 58 26 9 7871646 4r4 7 151 96 173 38 312 488 452 493 127 359 301

Ž . Ž .Major oxides % and minor elements parts per million both on ash basis.


Fig. 2. Geologic column of a portion of the coal-bearing section ofŽ .the Dixon quadrangle from Hansen, 1976 . Coal thicknesses are

Ž . Žin inches 1 in.s2.54 cm and unit thickness are in feet 1.fts0.304 m .

thickness coalB embayment he described. Spacing ofthe cores, and the lack of additional coverage, doesnot permit further definition of the edge of the coal.

Lithologic descriptions of the coal cores are shownon Table 3. The coal in core 623 is thinner, morebrecciated, and lower in sulfur than the coal in core

Ž .668, 3.45 km to the north Fig. 1 . The Herrin coal incore 623 has a duller appearance than the northernoccurrence. The Herrin coal in core 668 is dominatedby bright clarain with thin fusain and pyrite bands

Žincluded in the sampled coal the 2.0 cm pyrite band

Table 3Lithologic descriptions of coal from two cores in the Dixon 7 1r2min quadrangle, Webster County, Kentucky

Ž .Sample no. Thickness cm Lithology

Core 623shale roof

71799 1.3 dull clarain0.3 clarain0.7 siltstone5.4 clarain

Ž .not sampled 2.6 blue band71800 1.2 dull clarain

8.1 clarain71801 4.8 clarain

0.5 dull clarain

Core 668green shale roof

71833 1.2 bright clarain0.4 fusain0.3 bright clarain0.4 fusain4.0 bright clarain0.1 pyrite2.4 bright clarain

Ž .not sampled 2.0 pyrite71834 3.4 bright clarain

0.1 pyrite1.0 bright clarain0.2 pyrite1.0 bright clarain0.2 pyrite0.2 bright clarain0.2 fusain0.2 bright clarain

71835 6.8 clarainŽ .not sampled 3.2 silty shale71836 4.1 bright clarain

1.9 clarain


.was excluded from the sample . The latter attributesare typical of many Western Kentucky coals. Thepetrography and chemistry of the Dixon quadrangleHerrin samples are shown on Tables 4 and 5. Thecoals are high volatile A bituminous, with 0.73%vitrinite maximum reflectance in sample 71836.

4.1. Core 623

The coal in core 623 shows an upward increase inash yield and decrease in total sulfur. The lowermostsample, 71801, is characterized by a high vitrinitecontent. Pyrite occurs in the most massive form ofany of the core 623 samples. Perhaps the moststriking attribute of sample 71801 is the high Srcontent, 22,500 ppm on the ash basis. Sr is highthroughout the core and the upward decrease may bea function of the diluent effects of the abundant claysin the upper portions of the coal. Sr may be associ-ated with phosphate minerals; note the P O concen-2 5

tration of 1.1%. The relatively high concentration ofrare-earth elements in the basal lithotype comparedto the upper two lithotypes may also be a function ofconcentration in phosphates. The suggestion of a Srand REE association with phosphate minerals is aninference based on the coincidence of high concen-trations of the elements. Phosphate minerals were notfound in SEM observations. The top two samplesboth show some signs of disrupted banding, althoughnot to the extreme degree seen in previous studiesdiscussed above. Broken macerals, primarily semi-

Žfusinite, are recemented in part by exsudatinite Fig..3 . Examples of other brecciated macerals are shown

on Fig. 4. Overall, semifusinite and fusinite increaseŽ .upwards to a total exceeding 36% Table 4 , an

indication of oxidation of the peat. Pyrite occurs asfine framboidal and euhedral forms in the upper

Ž .sample 71799 .

4.2. Core 668

Core 668 shows a progressive upward increase intotal sulfur. Details of the variation in pyrite formswill be discussed in detail. The maceral content isnot as varied as in core 623. Inertinite macerals areimportant constituents in the coal, although not to thedegree found in sample 71799 from core 623.

Sample 71836, the lowermost sample of core 668,contains small framboidal pyrite clusters, some ofthem internally overgrown with a second generationof pyrite. Massive overgrowths of framboidal clus-ters were observed.

Sample 71835 contains overgrowths of fram-boidal clusters, some as very massive multigenera-tional overgrowths. Smaller euhedral pyrite crystalsare not overgrown. An unusual pyrite form consistsof rounded globules truncated by fusinite. Breccia-tion of the coal was observed as a rare phenomenon.The maceral assemblages contain high-relief texturedinertinites and abundant liptinites, including cutiniteswith included resinite.

Sample 71834 has a brighter megascopic appear-ance than the underlying clarain of sample 71835.This observation is not necessarily borne out by themaceral analysis, sample 71834 has the highest fusi-nite plus semifusinite content of any of the core 668samples. As in the underlying sample, there is someevidence of brecciation. High-relief textured inerti-nite macerals were observed. Carbonate occurs infusinite lumens. Pyrite consists of very massive over-

Table 4Ž .Maceral content %, mineral free basis of coal samples from Dixon quadrangle cores

Core Location Sample Bench Thickness Vit Fus Sfus Mic Mac Ex ResŽ .cm

Ž .668 Dixon 14-M-22 71833 1r4 top 8.48 74.4 12.0 9.5 0.6 0.2 2.2 1.171834 2r4 6.50 65.6 17.6 9.5 0.1 0.0 6.3 0.971835 3r4 6.78 79.2 8.5 3.6 0.1 0.1 6.2 2.371836 4r4 5.99 77.9 10.5 7.9 0.0 0.1 3.0 0.3

Ž .623 Dixon 16-M-22 71799 1r3 top 5.41 51.9 6.0 30.4 3.5 0.2 4.0 4.071800 2r3 9.40 74.2 5.9 11.5 0.5 0.1 2.9 4.971801 3r3 5.33 92.7 2.5 1.9 0.2 0.0 1.5 1.2

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Table 5Ash chemistry of coal samples from Dixon quadrangle cores

Ž . Ž .Core Location Sample Bench Thickness Ash S total XRF %, ash basis.Ž . Ž . Ž .cm dry dry MgO Na O Fe O TiO SiO CaO K O P O Al O SO2 2 3 2 2 2 2 5 2 3 3

Ž .668 Dixon 14-M-22 71833 1r4 top 8.48 31.21 13.33 1.18 0.16 43.24 0.48 16.96 9.33 0.36 0.30 12.65 8.6771834 2r4 6.50 27.68 10.07 0.78 0.32 30.58 0.83 25.60 7.82 0.77 0.14 16.83 7.7071835 3r4 6.78 27.26 9.74 0.76 0.23 27.51 1.07 37.28 2.92 1.51 0.37 18.81 1.8471836 4r4 5.99 26.18 4.24 0.57 0.34 10.45 1.10 44.47 1.19 1.62 0.11 21.29 0.82

Ž .623 Dixon 16-M-22 71799 1r3 top 5.41 59.96 2.38 0.62 0.40 5.41 1.67 64.49 0.20 2.16 0.18 22.20 0.1071800 2r3 9.40 40.54 3.18 0.28 0.22 6.79 1.16 57.29 0.31 0.98 0.50 27.87 0.1971801 3r3 5.33 17.54 3.58 0.66 0.28 15.94 0.70 41.22 1.50 2.07 1.10 27.00 1.60

Ž .Core Location Sample Bench XRF ppm, ash basis

Mo Zn Cu Ni Co Cr Ba V Mn Rb Sr Zr

Ž .668 Dixon 14-M-22 71833 1r4 top 124 1652 0 150 102 108 2297 182 456 49 425 14571834 2r4 53 19 29 38 62 131 4160 186 440 60 278 16371835 3r4 45 83 119 94 62 307 461 351 164 96 143 18871836 4r4 31 143 226 102 23 496 348 540 73 125 279 312

Ž .623 Dixon 16-M-22 71799 1r3 top 42 72 84 83 20 211 363 236 36 274 2220 57071800 2r3 68 38 30 124 24 129 560 199 1 112 13700 87071801 3r3 117 398 41 610 62 106 1520 352 44 154 22500 1110

Ž .Core Location Sample Bench ICP-MS ppm, ash basis

Y Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Th

Ž .668 Dixon 14-M-22 71833 1r4 top 28 170 17.6 55.3 7.1 1.4 8.2 0.7 3.9 0.7 2.0 0.3 1.9 4.971834 2r4 74 77 10.2 43.4 12.6 3.4 15.7 2.5 13.6 2.5 7.5 1.0 6.5 11.771835 3r4 87 85 11.5 51.6 15.1 3.6 14.9 2.5 14.2 2.5 7.5 1.0 6.3 18.871836 4r4 47 152 16.2 55.8 9.3 1.9 8.3 1.0 6.9 1.3 4.0 0.6 3.7 32.8

Ž .623 Dixon 16-M-22 71799 1r3 top 24 79 7.1 20.4 2.6 0.5 3.2 0.3 2.0 0.4 1.3 0.2 1.3 7.071800 2r3 28 97 9.8 32.9 5.0 0.8 3.9 0.5 2.7 0.5 1.5 0.2 1.5 3.971801 3r3 28 177 20.8 82.5 16.6 2.6 10.2 0.9 5.4 0.9 3.0 0.5 3.2 6.3

Ž . Ž .Major oxides % and minor elements parts per million both on ash basis.


Ž . Ž .Fig. 3. a Semifusinite cemented by exsudatinite sample 71799Ž330 mm across long axis; oil immersion, reflected white-light

. Ž .image . b Semifusinite fragment in mixed maceral–mineral mat-Ž . Žter matrix. sample 71799 330 mm across long axis; oil immer-

.sion, reflected white-light image .

Ž .growth forms and globular overgrowths Fig. 5 , thelatter containing 5 mm cores overgrown by 50-mm-diameter pyrite globules.

Sample 71833, separated from the lithologicallysimilar sample 71834 by a 2.0 cm pyrite band,contains several types of epigenetic pyrite. Massivepyrite occurs in both fusinite and vitrinite. Fusinitelumens can also be filled with carbonate and spha-

Ž .lerite Fig. 6 . Overgrowths of framboidal clusters,outer rims of pyrite around the overgrowths, arepresent, as in the underlying samples. Euhedral crys-tals, approximately 10 mm in diameter, occur in thecoal and smaller isolated and clustered euhedra arefound along the banding. The only evidence of brec-ciation appeared to be in the inertinites.

Overall, the Herrin coal in core 668 shows anincreasing epigenetic overprint from the base of thecoal to the upper lithotype. Pyrite mineralization issupplemented by a minor amount of sphalerite andby carbonate mineralization.

5. Summary

Together, the two cores illustrate the progressionof the Herrin coal from its absence, as known from

Ž . Ž .the work of Rogers 1985 and de Wet et al. 1997 ;through its appearance as thin, brecciated, and oxi-

Ždized during deposition; to a thicker albeit still not.mineable coal with extensive emplacement of syn-

genetic and epigenetic sulfides and epigenetic car-bonates. Mineable thicknesses of the Herrin coal arenot found in the Dixon quadrangle and, indeed,mining of the Herrin has not been conducted innorthern Webster County.

No other economic coal in western Kentucky isknown to show as many examples of the deposi-tional edge as the Herrin. If nothing else, the trilogy

Žof Herrin ragged edge studies Hower et al., 1987; de.Wet et al., 1997; this study illustrates the impor-

tance of retaining thin or otherwise uneconomic coresamples for future study. None of the examplespublished came from an underground or a surface

Žmine. Unless abrupt changes undocumented by ex-.ploratory drilling in the coal quality or thickness

occur, we should not expect to see the full extent ofa coal body in mining situations.

Core 623 contains the brecciated maceral assem-blage characteristic of the previously investigatedsites. Also, characteristic of the coal at other sites isthe fusinized breccia. The coarse fusinite and semi-fusinite suggest that oxidation occurred at the time ofthe deposition and subsequent reworking of the peat.The breccia is mixed with clay, further indication ofthe reworking experienced by the peat at the locationof core 623.

In contrast, core 668 does not show the intensereworking as in the southern core, although subtlesigns of brecciation were observed, particularly,among the inertinites. The Herrin coal in core 668 ischaracterized by an upward increase in epigenetic


Ž . Ž . ŽFig. 4. a–d Liptinite-rich fragments in maceral and maceral–mineral matter breccia sample 71799 330 mm across long axis; oil.immersion, reflected white-light image .

Fig. 5. Pyrite and marcasite overgrowths of framboidal aggregates.Multiple generations of sulfide growth can be seen from theoriginal framboids to the successive overgrowth stages, to theemplacement of a AspongyB sulfide between the overgrown sul-

Ž . Žfide globules. sample 71834 330 mm across long axis; oil.immersion, reflected white-light image .

Ž . Ž .Fig. 6. Fusinite fragment with pyrite p , sphalerite s , andŽ .carbonate all other unlabeled fusinite lumens filling of lumens

Ž . Žsample 71833 330 mm across long axis; oil immersion, re-.flected white-light image .


pyrite, carbonate, and minor sphalerite. Complexityof pyrite overgrowths of syngenetic and early epige-netic forms increase in the upper lithotypes of thecore.

No one series of sites can be considered represen-tative of all marginal depositional settings, and theHerrin models will certainly not hold for all coalbodies. The similarity of all of the known Herrinmargins supports the notion that the lateral termina-tion of the coal body involved the progressive loss ofthe upper lithologies through a combination of non-deposition and marginal erosion and reworking. Inthis manner, the lowermost bench of the coal is alsothe most widespread. Upper benches and partings,notably the Blue band, were added with progres-sively less aerial extent as deposition progressedupwards, a structure not unlike a tiered layer cake.Similar models were advanced for the overlying

Ž .Paradise coal bed Austin, 1979 . Indeed, the Herrinand Paradise coals, at least along the southern mar-gin of the coal field, should be considered as compo-nent coals in the same depositional system, with theParadise adding benches to the south of the marginof the full development of the Herrin.

References

Austin, S.A., 1979. Depositional environment of the KentuckyŽ .No. 12 coal Bed Middle Pennsylvanian of Western Ken-

tucky, with special reference to the origin of coal lithotypes.PhD thesis, The Pennsylvania State University, UniversityPark, PA, 390 pp.

de Wet, C.B., Moshier, S.O., Hower, J.C., de Wet, A.P., Brennan,S.T., Helfrich, C.T., Raymond, A.L., 1997. Disrupted coal andcarbonate facies within two Pennsylvanian cyclothems, south-ern Illinois basin, United States. Geological Society of Amer-ica Bulletin 109, 1231–1248.

Hansen, D.E., 1976. Geologic map of the Dixon quadrangle,Webster County, Kentucky. U.S. Geological Survey Map GQ-1293, 1:24,000.

Hower, J.C., Bland, A.E., 1989. Geochemistry of the Pond Creekcoal bed, Eastern Kentucky coalfield. International Journal ofCoal Geology 11, 205–226.

Hower, J.C., Trinkle, E.J., Graese, A.M., Neuder, G.L., 1987.Ž .Ragged edge of the Herrin No. 11 coal, Western Kentucky.

International Journal of Coal Geology 7, 1–20.Meier, A.L., Lichte, F.E., Briggs, P.H., Bullock, J.J., 1996. In:

Ž .Arbogast, B.F. Ed. , Analysis of Coal Ash by InductivelyCoupled Plasma-Mass Spectrometry: Analytical Methods forthe Mineral Resources Surveys Program, U.S. GeologicalSurvey Open File 96-525, pp. 109–125.

Rogers, T.J., 1985. Sedimentation and contemporaneous structuresin part of the Western Kentucky Coal Field. MS thesis, TheUniversity of Kentucky, Lexington, 52 pp.

Documents

Further examination of the ragged edge of the Herrin Coal Bed, Webster County, Western Kentucky Coal Field