Cannel coals: implications for classification and terminology

International Journal of Coal Geology 41 Ž1999. 157–188

Cannel coals: implications for classification and terminology Adrian C. Hutton

a,)

, James C. Hower

b

a

b

School of Geosciences, UniÕersity of Wollongong, Wollongong, NSW 2522 Australia Center for Applied Energy Research, UniÕersity of Kentucky, Lexington, KY 40511, USA Received 28 May 1998; accepted 1 December 1998

Abstract Cannel coals are tough, massive coals with a dull luster that break with an even, compact grain and conchoidal cross fractures. Historically, cannel coals were of significant economic and social importance during the early industrialization of the USA. They were the source for a sophisticated petrochemical industry and a fuel source for heating, gas making, coke making and oil generation. Petrographic data, proximate analysis and ultimate analysis data were obtained for 68 cannel coals from Kentucky to decide how well the cannel coals fit the generally-accepted definitions of a cannel coal. Four maceral assemblages were found—sporinite with abundant medium-grained vitrinite and inertinite, sporinite with abundant fine-grained vitrinite and inertinite of which micrinite is abundant Žbituminite may be present., alginite with abundant fine-grained vitrinite and inertinite, and alginite and bituminite with minor vitrinite and inertinite. Volatile matter and HrC ratios are highest for those samples with abundant liptinite with a sample from Breckenridge having the highest value of each. Five samples were analyzed by the Rock-Eval method. The S2 and HI indices show that the coals would make excellent source rocks. Discrepancies between the values for the five samples are related to maceral composition and there may be a good correlation between source rock potential and importance as a feedstock for synthetic crude oil production in the 1800s. The maceral composition of the microlithotypes is related to the environment of deposition. Coal composed of assemblage Ži. formed in humic peat swamps in which unusually large numbers of spores were introduced, possibly because of unusual, climatically controlled reproductive cycles. Coals composed of assemblages Žii. to Živ. formed as sapropelic coals in lakes at some stage of peat swamp development. q 1999 Elsevier Science B.V. All rights reserved. Keywords: Kentucky; cannel coal; petrology; classification; organic chemistry

)

Corresponding author. Tel.: q61-2-42213832; Fax: q61-2-42214250; E-mail: [email protected]

0166-5162r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 6 - 5 1 6 2 Ž 9 9 . 0 0 0 1 5 - 4

158

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

1. Introduction Historically, cannel coals were of significant economic and social importance during the early industrialization of the United States. Ashley Ž1918. gave a succinct history and description of the cannel coal industry in the latter part of the 19th century. Cannel coal from Cannelton, PA, was probably known to the native Americans as early as 1750 ŽMansfield, 1905. and was used by them as a fuel in hunting camps at the mouth of the Cannel Ravine. William and George Foulks are reported to be the first white men to learn the source of the Cannelton cannel coal when the native Americans held them captive. It is documented that cannel coal was known to the white immigrants by 1787 ŽMansfield, 1905.. Kentucky has been described as the premier cannel coal state and possessed one of the largest resources of any state, albeit, small compared with the total present-day humic coal resources. Mining of cannel coal in Kentucky was reported to be as early as 1837 when the Breckenridge deposit was mined and transported to the Ohio River where it was sold for 10 cents per bushel as a steaming coal ŽMather, 1839.. Cannel coal from Troublesome Corner, near the Kentucky River, was also transported on flat-bottomed boats in 1838. Kentucky cannel coal has always been sold for premium prices. In 1910, cannel coal was being sold for US$2.51 per ton in Kentucky, compared with US$0.98 per ton for bituminous coal. In New York the price was higher, due to transport costs, with the Breckenridge coal being sold for US$13 to US$14 per ton compared with US$16 to US$17 per ton for overseas cannel coal ŽHower, 1995.. Principal uses were to produce high candlepower gas as an additive to the gas produced from bituminous coal, for direct heating because of its ignition point and ease with which it burns, and for the production of oil. All three uses are directly related to the composition of the cannel coal. Many publications, of which Moore Ž1968. and Stach et al. Ž1982. are good examples, distinguish between two end members of sapropelic coals: Ži. Cannel coals or those containing humic macerals andror liptinite, but only minor alginite, if any; they are fine-grained and have macerals of approximately equal size; and, Žii. Boghead coals Žs torbanite. or those containing abundant alginite Žboghead coal derives its name from the Boghead estate, Bathgate, Scotland where it was first described.. Also recognized is boghead-cannel coal, which is an intermediate type between the two end members. Cannel coals are one of the two end members of ‘sapropelic coals’ or coals that form from ‘an organic mud’. They are tough, elastic, compact, massive rocks that generally lack well-defined bedding or layering, have a dull luster and typically a conchoidal fracture when broken. The published literature is somewhat vague where cannel coals are discussed and the definition of cannel is somewhat obscure. Stach et al. Ž1982. stated that microscopically, two types of cannel coal could be recognized: fine-grained coals having vitrinite andror inertinite macerals of approximately equal size; and coals with abundant liptinite, mostly sporinite. Important features of cannel coals were stated to be the almost uniform size of the constituents and the lack of alginite. Stach et al.

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

159

summarized the maceral composition of cannel coals as similar to that of clarite, durite or trimacerite. The International Committee for Coal Petrography ŽInternational Committee for Coal Petrology, 1963, 1971, 1975. stated the term ‘cannel coal’ was an old term, dating at least to Leland in 1538 ŽInternational Committee for Coal Petrology, 1963; citing Leland, 1710 1 . for a coal burning with a steady luminous flame. A synonym is gayet and ‘parrot coal’. The ICCP also listed the terms ‘cutinite coal’, ‘resinite coal’, and ‘sporinite coal’, defining each as containing more than 50% of the respective liptinite maceral. The Glossary of Geology ŽGarry et al., 1977. defined cannel coal in much the same way as Stach et al. and gave candle coal, kennel coal, cannelite, parrot coal Ždefined as a coal that makes a crackling noise when burning. and curly coal as synonyms. It appears the term cannel coal is derived from ‘candle coal’ because candlercannel coals burn with ‘a long and steady flame’ Žvan Krevelen, 1981., similar to that of a candle. Earlier, Ashley Ž1918. adopted a pragmatic classification and divided cannel coals into three types: Ži. subcannel coal, which can be further subdivided into ‘brown subcannel’ of brown coal rank, and ‘black cannel coal’ of subbituminous rank; Žii. cannel coal of bituminous rank, which could be further divided into boghead cannel Žfuel ratio of less than 0.5., typical cannel coal Žfuel ratio less than 1.0., and lean cannel or semi-cannel Žfuel ratio more than 1. where the fuel ratio was defined as the ratio of fixed carbon to volatile matter; and Žiii. canneloid, semibituminous, semianthracite, or anthracite coal. van Krevelen Ž1981. gave a very different definition of cannel coal. He stated that cannel coal contains abundant micrinite with a large quantity of dispersed microspores and stated that boghead coal contains micrinite. According to van Krevelen, cannel coals form from floating spore accumulations transported by wind and water and ‘deposited with vegetable mud’. This hypothesis for the origin of cannel coals is problematic because van Krevelen included the oil shale tasmanite as an ‘extreme’ variety of cannel coals. Han and Crelling Ž1993. plotted the composition of cannel coals, although included in their data set were kukersite and tasmanite oil shales, on a ternary diagram Žwith apices of alginite, sporinite and other phytoclasts. and came up with the following seven compositional clusters: Ø torbanite Žexamples being Australian torbanites, tasmanite and kukersite., Ø boghead Žthe Scottish torbanite., Ø cannel boghead ŽPuxiang coal, China., Ø boghead cannel ŽBreckenridge, KY. Ø cannel Žmost eastern US cannel coals. Ø spore cannel ŽCanadian Melville Island coal. Ø canneloid ŽIndiana paper coal and Texas Eocene cannel coals.. Cannel coals from Kentucky are liptinite-rich coals that have a high volatile content, generally above 40% and generally greater than the fixed carbon content, and ignite

1

From: Leland, J., 1710. Itinerary of John Leland the Antiquary.

160

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

more easily than humic coals. During the 1800s and the early 1900s, when the coals were being used extensively, not a lot was known of their petrographic composition although the proximate analysis test was commonly done. Ashley Ž1918. gave the best summary of the distribution of cannel coal in the USA. Cannel coals have been found in Alabama, Illinois, Indiana, Iowa, Kentucky, Michigan, Missouri, Ohio, Pennsylvania, Tennessee, Texas, Utah and West Virginia but mining has only occurred in Indiana, Kentucky, Ohio, Pennsylvania and West Virginia. Kentucky had the highest production with outputs of 138,400 short tons in 1905, 118,600 short tons in 1903 and more than 90,000 short tons in 1907, 1911 and 1913 ŽGesner, 1865.. Of the counties, Morgan County had the greatest production but cannel coal has been reported or mined in at least 19 other counties.

2. Petrography For this study, 62 samples with 10% or more liptinite were selected from the database of samples held at the Center for Applied Energy Research, University of Kentucky. For those cannel coal samples that had a humic coal in the same seam, the corresponding humic coals were also studied petrographically. Each sample was crushed to ) 0.85 mm and set in quick-setting resins using standard petrographic methods. A surface of the pellet was ground flat and polished. The pellets were examined in incident white light and fluorescence modes. Using a cutoff of 20% sporinite, the minimum thought to fit the ‘cannel coal’ definition as prescribed by International Committee for Coal Petrology Ž1963. and Stach et al. Ž1982. in being ‘rich in sporinite’, only 14 of the samples examined in this study can be accommodated by the definition. One of these coals, a sample from Pond Creek ŽPike County. contained 56% sporinite and another sample from Cannel City ŽMorgan County. contained 40% sporinite. Of the other samples: two samples from the Breckenridge deposit, Hancock County, contained ) 70% bituminiteq telalginite; one sample from the Skyline Lower Split contained ) 20% telalginiteq sporinite; and all other sample contained less than 20% sporinite. Using petrographic composition, the Kentucky cannel and cannel-like coals can be divided into four groups based on liptinite-rich maceral assemblages: Ži. sporinite with abundant medium-grained vitrinite and inertinite Žmicrinite may be a minor component. wSIVx; Žii. sporinite with fine-grained vitrinite and inertinite including abundant micrinite Žbituminite may be present. wSIMVx; Žiii. telalginite with abundant fine-grained vitrinite and inertinite wTIVx; and, Živ. bituminite and telalginite with minor vitrinite and inertinite wBTx. Petrographically, the Kentucky coals of Group Žiii., the TIV composition, belong to the boghead-cannel coal category because of their alginite content. The coals of Group Živ., the BT composition, are best called boghead coals or torbanites. Given that few Kentucky coals have a high sporinite content, and due to the variability in vitrinite, inertinite and sporinite content in boghead-cannel coals from elsewhere, questioning the need for categorization of the sapropelic coals into the two end members is necessary.

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

161

One point to note is that many ‘cannel coals’ were given that name because of their physical properties and the volatile content, long before organic petrography was developed. It was not until approximately 1890 that torbanites were thought to contain algae. The definitive paper on the composition of torbanites was that of Blackburn and Temperley Ž1936.. It is suspected that many ‘cannel coals’ used in the 1800s derived their properties from algae rather than spores and should be placed in the boghead coal or torbanite group. It should be noted especially that although four maceral assemblages can be recognized, the boundaries between one assemblage and another overlap. 2.1. Sporinite–inertinite–Õitrinite (SIV) assemblage This assemblage is similar to the maceral assemblage commonly found in most Carboniferous coals of the Northern Hemisphere, including the Western and Eastern Kentucky humic coals. The SIV coals differ from banded coals only in that liptinite is more abundant than is the norm for Kentucky coals. These coals are dull, relatively hard, and have the typical physical appearance associated with cannel coals. Although not well documented, many of this type of coal probably go unreported because they occur as thin lenses, layers or plies within the normal humic coal seams. Vitrinite and inertinite are the dominant maceral groups in the SIV assemblage, as they are in many Carboniferous Northern Hemisphere coals. Vitrinite mostly comprises telocollinite and desmocollinite, whereas inertinite macerals include semifusinite, fusinite, inertodetrinite and minor macrinite and micrinite. Micrinite is commonly dispersed throughout the sample and rarely occurs in dense zones as in the following type ŽSIMV coal.. Texturally, coals of the SIV-type are typically well-banded because of the microlithotype arrangement, although in many samples there are layers of finer-grained macerals. Many microlithotypes are monomaceral microlithotypes Žwith telocollinite, fusinite and semifusinite the dominant macerals. or multimaceral microlithotypes Žwhere liptinite is a maceral.. The most abundant liptinite maceral is sporinite Žmostly miospores but also megaspores., making up to 20% of any sample and up to 50% of some microlithotypes. Resinite and cutinite are the next most abundant macerals. Alginite is absent. 2.2. Sporinite–inertinite– (micrinite) –Õitrinite (SIMV) assemblage Petrographically, this assemblage is similar to the SIV-type except that vitrinite and inertinite are fine-grained and probably attrital. Vitrinite is mostly small lens-shaped desmocollinite. Telocollinite, derived from roots or stems, is present in some samples. Inertodetrinite is the most abundant inertinite although clast-like fusinite and semifusinite are dispersed throughout the samples. Coals with this assemblage generally have typical ‘cannel coal’ textures. Invariably, micrinite is an abundant constituent and is dispersed throughout the microlithotypes or occurs in pods and lenses, especially in vitrinite. Sporinite is ubiquitous throughout the coal; miospores are dominant but megaspores and sporangia are also present. Cutinite and resinite are minor components; alginite and bituminite are minor components in some samples.

162

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

2.3. Telalginite–inertinite–Õitrinite (TIV) assemblage Telalginite and fine-grained vitrinite and inertinite characterize this assemblage. Telalginite is an ovoid, strongly fluorescing alginite that is derived from Botryococcusrelated colonial algae. In sections parallel to bedding, the morphology of many colonies is clearly that of the Pila form composed of many fan-shaped branches with the unicellular algae at the extremities of the branches. The telalginite is generally 0.02 to 0.20 mm in diameter with an average diameter of less than 0.1 mm. The Pila forms in these samples are therefore much smaller than the Reinschia form of Botryococcus that is the main component of Southern Hemisphere torbanites such as those from Australia and South Africa. As the rank of the coal increases, the fluorescence intensity of the telalginite decreases and changes from yellow to yellowish-orange. The abundance of telalginite is quite variable ranging from a minor component comprising as little as several colonies, up to several tens of percent per grain in the polished blocks. Minor liptinite components include sporinite, resinite and rarely cutinite and bituminite. Vitrinite is mostly desmocollinite with rare telocollinite. Inertodetrinite is the dominant inertinite with micrinite next most abundant. Minor semifusinite and fusinite are found in most samples. The vitrinite and inertinite form a groundmass that is interstitial to the telalginite and larger vitrinite and inertinite. Micrinite occurs in several samples. 2.4. Bituminite–telalginite (BT) assemblage This assemblage is found in the Breckenridge coal from Hancock County, western Kentucky, and has been reported in the Cretaceous King Cannel by Given et al. Ž1984, 1985.. Hower et al. Ž1987. described the petrography and geochemistry of the Breckenridge coal in detail and concluded that it fits into the torbanite or boghead coal group. Breckenridge coal is composed of abundant bituminite that has a weak to moderately intense yellow to greenish-yellow fluorescence, and is interstitial to telalginite derived from the Pila form of Botryococcus. Minor components include micrinite, inertodetrinite, detrital fusinite and semifusinite. Vitrinite is mostly desmocollinite of the form Hower et al. Ž1987. described as sapropelic vitrinite.

3. Geochemistry 3.1. Proximate and ultimate analysis data The Kentucky coals studied had relatively low moisture contents with a maximum of 7.54%, but with most below 5%. This is within the same range as those for the corresponding humic coals. Ash contents, on an as received basis vary considerably with a maximum value of 60% Žthis sample is probably best termed a canneloid shale rather than a cannel coal. and a low value of 2.95%. The corresponding humic coals had a much lower range of ash values with the maximum being 28.52%.

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

163

Fig. 1. Plot of HrC vs. OrC ratio for Kentucky coals analyzed in this study.

HrC and OrC ratios for the cannels and some humic coals are shown in Fig. 1. The cannel coals generally have higher HrC ratios than their corresponding humic coals with the OrC ratios in the same range. One humic coal, with a total liptinite content of Table 1 Rock-Eval data Sample Breckenridge Breckenridge mean Cannel City mean Clarion mean Skyline lower split Leatherwood mean

Tma x

443 443 443 434 436 435 447 447 447 443 443 443 443

S1 Žmg HCrg rock.

S2 Žmg HCrg rock.

S3 Žmg CO 2 rg rock.

HI

OC

TOC

9.77 14.85 13.54 14.20 11.71 11.03 11.37 9.11 8.22 8.67 2.28 5.76 6.76 6.26

400.17 454.05 448.12 451.09 325.65 320.72 323.19 367.25 352.14 359.70 271.63 236.44 238.94 237.69

4.00 4.55 4.06 4.31 3.13 2.88 3.01 3.23 3.36 3.30 6.38 3.84 3.84 3.84

559 651 617 634 434 443 439 499 509 504 347 366 367 367

5 6 5 5.5 4 3 3.5 4 4 4 8 5 5 5

71.57 69.67 72.61 71.16 75.00 72.38 73.69 73.59 69.09 71.34 78.11 64.55 65.06 64.81

164

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

Table 2 Proximate and ultimate analyses Ž% as received. Sample

Moisture Volatile Fixed Ash matter carbon

Total Carbon Hydrogen Nitrogen Oxygen HrC OrC sulfur

Breckenridge Skyline lower split Cannel City Clarion Leatherwood

2.27 1.21

55.70 51.67

32.05 38.06

9.98 3.30 9.06 1.05

71.85

7.35

1.64

5.88

1.22 0.06

2.89 4.77 3.24

45.20 38.50 37.40

40.32 52.42 54.55

11.59 1.21 4.31 0.62 4.81 0.71

70.33 75.54 77.57

5.68 5.20 5.47

1.47 1.46 1.63

9.72 12.87 9.81

0.96 0.10 0.82 0.13 0.84 0.10

9% and abundant vitrinite and inertinite, had an HrC ratio of 1.04. This high value may depend on experimental error or sample reproducibility. The Breckenridge samples, which contained ) 75% liptinite, had HrC ratios of 1.30 and 1.22. 3.2. Rock-EÕal data Rock-Eval data for selected cannels are presented in Table 1; proximaterultimate analysis and petrographic data for the same coals are presented in Tables 2 and 3. For all but one sample, duplicate analyses were done. The Tmax values were similar to each other and in the range 435 to 447 ŽTable 1.; these values place the samples at a maturity that is at or above the threshold for the oil generation window ŽPeters, 1986.. This position is also supported by the vitrinite reflectance data for only two of the coals. The Breckenridge sample and the Cannel City coal have the lowest R v max values, 0.55% Ždata from Hower et al., 1987. and 0.58%, based on the reflectance of humic coals associated with the cannel coals. Both values are just above the threshold of the oil generation window. Reflectance data for humic coals associated with the Clarion and Leatherwood samples were 0.77% to 0.85% and 0.83%, respectively. Mastalerz and Hower Ž1996. gave the reflectance of the Skyline Lower Split as 0.72%. The rank of the latter three coals would suggest that Tmax for these samples should be higher. The Breckenridge coal has the highest S1 Žmg hydrocarbons wHCxrg of rock., S2 Žalso expressed in mg HCrg of rock. ŽTable 1. and HI Ž S2rTOC wtotal organic carbonx.

Table 3 Maceral analysis Sample Breckenridge Cannel City Clarion Skyline lower split Leatherwood

thickness Žm.

Telalginite 6.6

0.33 0.38 0.11 1.68

Bituminite

Resinite

Sporinite

Liptinite Žtotal.

Vitrinite Žtotal.

Inertinite Žtotal.

4.3 0.7

20.0 20.6 23.8

77.5 24.3 21.3 46.6

19.8 8.8 23.9 19.0

2.7 66.9 54.8 34.4

1.9

10.1

12.0

62.7

25.3

70.9

22.8

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

165

values; the Skyline Lower Split sample has the lowest S1 and HI values, and the highest S3 Žmg CO 2rg of rock. value; the Cannel City sample has the lowest S2 value. Given values of the magnitude obtained for the various Rock-Eval parameters, the Kentucky coals examined in this study are excellent source rocks.

4. Discussion 4.1. Seam characteristics Cannel coals have been described as ‘‘layers or lenses up to several centimeters thickness’’ ŽInternational Committee for Coal Petrology, 1963. and ‘‘lenticular masses of limited horizontal extent, being found usually at the top or bottom of a coal seam’’ and generally less than 2 ft Ž60 cm. thick. Dulhunty Ž1951. stated that cannel coals are separated vertically from humic coals but laterally may grade into cannel–boghead or boghead–cannel, depending on the composition of the respective rocks. While there are few accessible cannel coal deposits with which to test the above generalizations, Ashley Ž1918. presented thickness data for 374 cannel coals either as measured seam sections or in tabulated form. Two hundred and two measurements were for cannel coals in Kentucky with the remainder from 11 other states. The data from Ashley provided a unique opportunity to test the thickness and cannelrbituminous coal hypotheses. Generally, the thickness data show extreme variation. For both Kentucky and other states, most cannels are less than 1.5 m thick ŽFig. 2. and some seams show significant variation within the individual seams. Ashley reported some extremely thick seams but these may be rather unique and restricted to specific local occurrences. In Indiana County, PA, Ashley stated that a correlative of the CX or Upper Kittanning bed had a 30 cm to 4.6 m cannel coal overlying approximately 1 m of bituminous coal. In one direction, the cannel decreased to - 40 cm and in the opposite direction, the cannel changed from 2.7 m to 30 cm over a very short distance ŽPlatt, 1878; cited in Ashley, 1918.. This coal had volatile matter of only 23% to 24%. Also reported were a 2.1 to 2.7 m cannel coal seam in Holmes County, OH, with volatile matter ranging from 28% to 44.7% Žsuggesting either vertical andror lateral variations in the properties of the coal, particularly volatile matter.. Seams in Armstrong and Beaver Counties, PA, were - 2.5 cm to 2.75 m and 4.6 m thick, respectively. The thickest seams were reported from Missouri. In Cole County, Missouri, seam thicknesses of 4.3, 6.1 to 9.1 m, 25.3, 26.2 m and ‘30 to 90 ft, chiefly of the cannel variety’ Ž9.1 to 27.5 m. were given. Based on the data given in Ashley, the average cannel thickness is 1.3 m Ž50.4 in.. for Kentucky, 1 m Ž42 in.. for other states; for all seams, irrespective of state, the average is 1.2 m Ž46 in... If the very thick seams in Pennsylvania and Missouri are not included, the average thickness is 0.8 m Ž32.7 in... To test the cannelrbituminous coal association hypothesis, the 124 measured sections for Kentucky cannel coals and 74 sections from other states, given in Ashley, were grouped into three divisions. Each division was further divided according to the presence or absence of intraseam clastic units in either the cannel or bituminous coal. Ashley’s

166

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

Fig. 2. Seam thickness for Kentucky cannel coals. Data given in Ashley Ž1918. for cannel coals from Kentucky and for cannel coals from other US states are also included.

data ŽFig. 3. show most cannel coals are associated with bituminous coal but a significant proportion occurs as cannel only seams. Specifically, Ø 22% of Kentucky cannel coals, and 16% of cannel coals in other states, occur as cannel-only seams; Ø 56% of Kentucky cannels, and 38% of cannels coals in other states, occur below a bituminous coal unit; Ø 7% of Kentucky cannels, and 34% of cannel coals in other states, occur above a bituminous coal layer; and, Ø 15% of Kentucky cannels, and 12% of cannel coals in other states, occur with bituminous coal both above and below the cannel coal. The data in Ashley Ž1918. are pertinent to any understanding of the environments of deposition of cannel coals and torbanites. The above data on cannel–humic coal relationships show that although slightly more than half the cannel coal deposits recorded occur below a humic coal, many do not; often, cannel coals are not associated with a humic coal. Thus, there may be no ‘evolutionary model’ for cannel coal–humic coal formation and therefore there is no ‘timing’ factor involved. It would appear that cannel coals can form anytime in the evolution of a sedimentary basin. It is suggested that the important factors for the formation of cannel coals and torbanites are: Ø formation of a depression, and a significant rise in the local water table within that depression, to form a ‘lake’; depressions formed by river erosion, fire or other erosion agents would be potential cannel coal sites;

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

167

Fig. 3. Plot showing the number of cannel coals seams associated with and without humic coal seams. Data from Ashley Ž1918..

Ø relatively fresh water with a good supply of nutrients for torbanites; Ø a flora with climatically controlled, unusually high reproductive cycles that produce exceedingly large supplies of spores for cannel coals. The cannel coal–torbanite episode would wane or stop if the following occurs. Ø A river brings excessive amounts of clastic detritus causing the lake to fill rapidly and cover the organic mud; occasionally a humic coal or a second cannel coal would develop depending on the extent of the relative rise in the water table; where rivers supply clastic detritus but not enough to preclude the input of spores then a canneloid shale would form. Ø For lakes with algae, rivers bring an increased clastic input or an influx of dissolved salts into the lake, leading to increased turbidity or salinity and promulgation of conditions not conducive to algal growth. Ø The organic mud fills the lake causing a drop in the water table and the promulgation of conditions, which encourage development of a peat mire. The ‘basins’ in which these cannel coals and torbanites were deposited were small, with some in Kentucky being little more than oxbow lakes or abandoned meanders. Ashley gives several examples to illustrate this: Ø the Cannelton deposit, Pennsylvania, contained up to 4.6 m of cannel coal in the deepest part of a 180 m wide channel that circumscribed a basin 3 km by 1.5 km; 45 m on each side of the channel axis, the cannel coal had thinned to less than 2 m;

168

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

Ø the Chenoa deposit in Kentucky, thinned dramatically within 120 m of the axis of the channel to such an extent that the cannel coal could not be worked; Ø the cannel coals in Missouri, which contained up to 27 m of coal, occupied 30 m wide channels eroded into the underlying limestone basement; these deposits were traced for at least 150 m in an east–west lengthwise direction; Ø another Missouri deposit was a 60 m diameter deposit with 4 m of cannel above 1.3 m of bituminous coal; and Ø in Moniteau County, Arkansas, one pocket of cannel coal was approximately 120 m long by 45 to 60 m wide with the cannel coal 14 m thick; the cannel coal resources were estimated to be 75,000 tons. In any shallow basin, several deposits or pockets of cannel coal probably formed close to one another. Data showing variation in mining thickness within closely spaced mines in Kentucky would support this hypothesis. 4.2. Geochemistry 4.2.1. Proximate and ultimate analyses Ashley Ž1918. stated cannel coals generally have 25% to 45% fixed carbon compared with 45% to 75% for bituminous coals and 45% to 75% volatile matter compared with 25% to 45% for bituminous coals. However, many cannel coals that Ashley described have less than 45% volatile matter, with similar values obtained for the samples in this study. A review of the data for cannel coals given in Ashley Ž1918. also shows the following for both Kentucky and other US cannel coals: Ø a linear relationship between ash and specific gravity; Ø no relationship between ash and either fixed carbon or volatile matter; Ø no relationship between sulfur and ash contents; and Ø no relationship between seam thickness and ash content. For the cannel coals analyzed as part of this study, the volatile matter contents vary widely, in part reflecting the liptinite content ŽFig. 4.. Most of the samples studied had liptinite contents of less than 20%, clustered in the 10 to 20% liptinite range. The scatter of points for the samples with this range of volatile matter is probably related to the relative proportions of vitrinite and inertinite and mineral matter. Three samples, two Breckenridge samples and the Skyline Lower Split sample, contains 43% liptinite and these samples have the highest volatile contents. A sample from the Pond Creek seam also had 40% liptinite Žmostly sporinite. but it has a low volatile matter content. This coal was one of the higher rank coals examined. Proximate and ultimate analyses were not done for the sample with 56% sporinite. A plot of liptinite content vs. HrC ratio ŽFig. 5. shows a similar pattern except the Skyline Lower Split sample has an HrC ratio of 0.8, lower than expected given the 43% liptinite content. This sample has 34% inertinite and 19% vitrinite and this may account for the low HrC ratio. The cannel coals of Kentucky were exploited for their high gas and oil yields, largely attributable to the liptinite content. The Breckenridge cannel oil analyzed using pyrolysis–gc ŽFig. 6. is aliphatic, showing a predominance of alkeneralkane homologs in the C5 to C10 region with a dramatic decrease in the intensity of peaks beginning with C11

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

Fig. 4. Plot of volatile matter content vs. liptinite content for Kentucky cannel coals.

Fig. 5. Plot of HrC ratio vs. liptinite content for Kentucky cannel coals.

169

170

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

Fig. 6. Pyrolysis–gc chromatogram for Breckenridge cannel coal showing the alkeneralkane pairs dominant in the C6 to C10 range.

and a significant tailing-off between C23 and C30. The pyrolysis–gc trace for the Breckenridge coal is similar to that for Alpha torbanite, shown in Hutton and Madre Ž1990. and other torbanites shown in Crisp et al. Ž1987.. The pyrolysis–gc for Alpha torbanite, which is typical of those derived from torbanites, had a slight bimodal shape with maximum peak heights at C10 and the C19 to C23 region. The abundance of alkeneralkane pairs in the region below C23 for both the Breckenridge and Alpha torbanite oils is due to the abundance of liptinite macerals in each. The abundance of liptinite is the primary influence on oil yields from pyrolysed rocks and the type of liptinite determines the oil composition. A small yield of oil, with some differences in properties, is derived from vitrinite. Oil derived from rocks that contain a significant proportion of terrestrial liptinite and vitrinite are characterized by alkeneralkane homologs that are more abundant in the higher carbon number range than in the oils derived from alginite-rich rocks ŽHutton, 1990.. 1-Pristene, phenols and other aromatic compounds are more abundant than in the oil derived from oil shales that contain liptinite derived mostly from terrestrial liptinite. The terrestrial origin of the parent organic matter also imparts higher oxygen content than is in the oils derived from algal sources. The Breckenridge cannel coal contains ) 70% liptinite and approximately 16% vitrinite. Thus, the aliphatic oil derived from Breckenridge coal is derived principally from bituminite with most of the remainder from telalginite; vitrinite would contribute only a small amount of the oil. The Breckenridge coal was an important feedstock for the Kentucky cannel coal industry in the 1800s. Mining can be dated from 1837 but large scale mining commenced in the 1850s with up to 10,000 tons of the cannel coal shipped to England for gasification ŽHower, 1995.. Twelve retorts were constructed in 1855, with production of

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

171

600–700 gallons Ž2000 to 2400 l. per day. An additional 18 retorts were constructed after 1856. The high yields of oil and the aliphatic nature of the Breckenridge oil were the two prime reasons for the significant status of the Breckenridge coal. As discussed above, it is the bituminite and the telalginite that ultimately determine the oil properties and consequently the status of the Breckenridge coal. 4.2.2. Rock-EÕal Rock-Eval is one of the geochemical techniques commonly used to assess petroleum source rocks, both for maturity and for petroleum generation potential. With the Rock-Eval technique, pulverized samples are pyrolysed under a programmed temperature regime. Three products are given off and pyrograms show three peaks consequently. The first peak Ž S1 . represents the extractable or free organic compounds Žs bitumen, Peters, 1986. given off first followed by the distillation products of the insoluble organic matter Žs kerogen. but does not correspond directly to the soluble or solvent extractable organic matter. The S2 parameter is a measure of the hydrocarbons generated by the pyrolytic degradation of the insoluble organic matter or kerogen. The third peak Ž S3 . represents the products from the combustion of residual carbon. In commercial retorts, the oil yield is the sum of the extractable and distillation products. Katz Ž1983. stated that three fundamental assertions for a reliable interpretive scheme are: Ø pyrolytic yields of hydrocarbons and carbon dioxide are independent of the associated mineral matrix; Ø relative yields of hydrocarbons and carbon dioxide remain constant per unit weight of organic carbon; and Ø S2 hydrocarbons are derived solely from the pyrolytic breakdown of kerogen. Although the cannel coals of Kentucky are unlikely to be considered source rocks based on their thickness and extent, Rock-Eval data was obtained to compare the source rock potential of the cannel coals with the known retorting behavior of the cannel coals. The five samples sent for routine Rock-Eval analysis were selected because they were of historical significance, they were the samples with the highest liptinite contents, and the liptinite type and content varied from one sample to another. Using HI and OI Ž S3rTOC., the Breckenridge coal plots as Type I and the four others plot as oil-prone marginally-mature Type II with the Skyline Lower Split coal plotting as the most mature. HI and OC indices depend on the maceral composition and the maturity of the samples. The Breckenridge coal is the least mature sample, has the highest liptinite content, and plots accordingly. The Cannel City coal is only slightly more mature but has a much higher vitrinite and inertinite content, thus it plots in the Type II region. The other samples are more mature and plot in a similar position to the Cannel City sample. The Leatherwood and Skyline Lower Split coals plot as the most mature samples. The atomic ratio data for the cannel coals mirrors the data obtained from the Rock-Eval analysis. Plots of OrC vs. HrC ratios ŽFigs. 1 and 7. for data obtained from this study and data given in Ashley Ž1918. and Moore Ž1968. show: Ø the recent sediments coorongite and balkashite, which are almost entirely composed of algae, have the highest HrC ratios ) 1.7; Ø the HrC ratios of the Kentucky cannel coals range from 1.13 to 0.76;

172

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

Fig. 7. Plot of HrC ratio vs. OrC ratio for cannel coals and torbanites Ždata from this study and from Ashley Ž1918...

Ø among Kentucky cannel coals, the Breckenridge coal has the highest HrC ratios, 1.2 to 1.3, with the Clarion sample having the lowest, 0.82; Ø overall, the HrC values reflect the abundance and type of liptinite with the Breckenridge containing ) 70% bituminiteq telalginite; the other samples have much lower liptinite contents, and dominated by terrestrially-derived organic matter; Ø of the other US cannel coals, the Utah samples have the higher HrC ratios reflecting differences in either rank or coal type compared with the Kentucky coals; Ø where the HrC ratios for both the Kentucky cannel coal and the corresponding humic coals are plotted, the cannel coals have the higher HrC ratios; Ø multiple samples of the Cannel City cannel have HrC ratios ranging from 0.83 to 1.11 with the samples with more abundant liptinite having the highest HrC ratios; for these samples both liptinite and volatile matter are linearly related to HrC; Ø of the five samples analyzed by Rock-Eval, the Breckenridge coal has the highest HI and HrC ratios and the Skyline Lower Split and Leatherwood coals have the lowest HI and HrC ratios; and Ø HrC is linearly related to volatile matter ŽFig. 8.. Mastalerz and Hower Ž1996. showed that the elemental compositions of the coals, for which Rock-Eval data were obtained in this study, could also be interpreted in terms of the organic petrography. They found HrC ratios decreased with increasing maturation as expected, given the petrographic composition, but the OrC ratios showed consider-

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

173

Fig. 8. Plot of volatile matter content vs. HrC ratio for selected Kentucky cannel coals.

able variation and did not reflect maturation trends. This was thought to reflect variable depositional conditions. An alternative explanation for the OrC ratios could be that the range in maturation levels, 0.55% vitrinite reflectance for the Breckenridge to 0.85% for the Leatherwood coal, may be too small to produce a trend in oxygen content. Also, because the coals have significant inertinite and vitrinite contents, differences in oxygen content might also reflect differences in the types of vitrinite and inertinite. The Productivity Index ŽPI;s S1rŽ S1 q S2 .. and Tmax , are commonly used to assess the maturity of petroleum source rocks. Table 1 shows the five samples have Tmax values between 435 ŽCannel City. and 447 ŽClarion. which are near the top of the oil generation window ŽPeters, 1986.. However, as noted, the reflectance data for three samples does not support the Rock-Eval results. Kalkreuth and Macauley Ž1986. found decreasing Tmax with increasing vitrinite content in the torbanite from the Pictou Coalfield and attributed the lower than expected Tmax values for torbanite in the Pictou Coalfield, Canada, to increased vitrinite content. A similar effect may be involved for the Kentucky cannels. Using PI as a maturity parameter, all samples are well below the lower limit of the oil generation window. PI values range from 0.008 ŽSkyline Lower Split. to 0.03 ŽBreckenridge and Cannel City.. The range is an order of magnitude below the accepted top of the oil generation window suggesting that all samples are immature. This conflicts with the Tmax values. Kalkreuth and Macauley Ž1986. found PI values of between 0.1 and 0.2 for the Albert Shale in New Brunswick, Canada, and suggested that given these

174

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

values, as much as 20% of the recovered oil in the Rock-Eval analysis represented geologically generated light hydrocarbons. They found lower PI values for the Pictou torbanite and Macauley et al. Ž1985. accounted for the lower PI values by suggesting that only the vitrinite in the samples had matured. If the interpretation of Macauley et al. is correct, it can be concluded that algal-derived organic matter produces oil at a higher maturity level than does vitrinite. Supporting evidence for this comes from Ottenjahnn Ž1988. who found that vitrinite produces hydrocarbons at a lower maturity than sporinite. Total Organic Carbon ŽTOC., S1 and S2 are Rock-Eval parameters used to assess petroleum generation potential or source rock richness. Using the criteria of Peters Ž1986., TOC values of the five cannel coals are at least an order of magnitude higher than the value assigned to the ‘ very good’ category. The samples have marginally higher values ŽSkyline Lower Split. up to seven times higher ŽBreckenridge, 14.42 mg of hydrocarbons per gram of rock. than the ‘ very good’ category with respect to S1. The five samples have S2 values at least an order of magnitude higher than the ‘ very good’ category for S2 . The HI values show that the cannel coals would produce oil under natural petroleum-generation conditions. The potential yield of the cannel coals can be estimated by converting the Rock-Eval oil yields to a yield per unit TOC. These calculations show the Breckenridge sample has the highest yields of both free hydrocarbons and pyrolysed hydrocarbons Ž0.199 and 6.341 mgrg per %TOC, respectively.. The Cannel City and Leatherwood samples have much lower values Ž0.029 and 3.478 mgrg per %TOC and 0097 and 3.668 mgrg per %TOC, respectively.. The pyrolysis yields show the retort oil potential when the Breckenridge coal is used in a commercial retort, underlining the reason the Breckenridge coal was regarded as the preferable feedstock for the emerging petrochemical industry in the 1800s. Hutton and Cook Ž1980., Kalkreuth and Macauley Ž1984., Wolf and Wolff-Fischer Ž1984. and Price and Barker Ž1985. postulated that lower than expected vitrinite reflectance may be caused by volatile components, hydrocarbons or resinous material absorbed by the vitrinite. Using TEM studies, Taylor and Liu Ž1989. confirmed that lipid-rich material derived from bacteria and fungi was present in some vitrinite. Ž1989. reported that Rouzard Ž1984. used electron microscopy to show oil Teichmuller ¨ droplets between the aromatic units of vitrinite. The free hydrocarbons manifested as the S1 peak probably represent hydrocarbons produced during the early stages of coalification from liptinite and vitrinite macerals. A less likely explanation is the S1 peak represents oil or bitumen that has migrated into the cannel coals from an alternative source. Liptinite is linearly related to HrC ratio, S2 ŽFig. 9. and HI ŽFig. 10.. The Skyline Lower Split sample, containing ) 22.5% telalginite and ) 23.5% sporinite, does not fit the plotted trends. With this liptinite content the S2 and HI values would be expected to be higher. The volatile mater is also lower than expected. Peters Ž1986. commented that heavy ends of migrated oil and indigenous bitumen influence S2 and Tmax . Contamination can be suspected where the S1 value is ) 2 mg HCrg rock, the HI is anomalously high, the Tmax is anomalously low and the S2 peak is bimodal. Although the S1 peaks for four of the five cannel coals are ) 6.28 HCrg rock, the S1 peak for the Skyline

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

Fig. 9. Plot of S2 values vs. liptinite content for selected Kentucky cannel coals.

Fig. 10. Plot of HI values vs. liptinite content for selected Kentucky cannel coals.

175

176

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

Lower Split sample is 2.28, the lowest yield of free hydrocarbons of the cannel coals. The HI value is also lower than that for the other samples and this suggests that contamination by migrated oil or bitumen is not the reason. The cannel coals studied have the following maceral compositions: Breckenridge—bituminite–vitrinite–telalginite Cannel City—micrinite–sporinite–inertiniteU –vitrinite Clarion—inertiniteU –vitrinite–sporinite–micrinite Skyline Lower Splita—sporinite–telalginite–vitrinite–micrinite–inertiniteU Leatherwoodq —vitrinite–inertiniteU –sporinite–micrinite U Ž fusinite and semifusinite; a—elemental data not available; q—specific maceral analysis not available.. Given the wide range of petrographic compositions for the five coals, some apparent discrepancies in the Rock-Eval data for the cannel coals are probably related to the composition of cannel coals rather than to problems encountered during the analyses. Hower et al. Ž1987. noted an increase in the relative ratios of aromatic components to straight chain aliphatic hydrocarbons in oils derived from pyrolysis of density separated fractions of the Breckenridge coal. They attributed increased aromaticity to increased vitrinite contents in the respective fractions, not to changes in the algal chemistry. In advocating this hypothesis they noted that there were substantial changes in the ratios of telalginite to bituminite in two of the concentrates although there were no obvious differences in the pyrograms. They concluded that the pyrolysis products derived from telalginite and bituminite are essentially the same in the Breckenridge coal. From this data it is concluded that variations in chemical behavior of cannel coals and torbanites are more closely related to the relative proportions of terrestrially-derived liptinite, vitrinite and inertinite than to the relative proportions of telalginite and bituminite. 4.3. EnÕironments of deposition The generally accepted origin for sapropelic coals is an open body of water, possibly surrounded by a peat mire that may grade from one vegetation type to another depending on factors such as climate. A similar scenario is envisaged for torbanite or boghead coal. This is the model given in Stach et al. Ž1982. where it is stated that sapropelic coals are deposited as subaquatic muds under more anaerobic conditions than humic coals. Humic coals may be occasionally deposited as humic muds under partly aerobic conditions. The important constituents of cannel coals are physical and biological degradation products. Thus, whereas humic coals were coalified from peat, sapropelic coals were coalified from gyttjae, finely detrital organic muds deposited under oxygen-deficient or reducing conditions which result from an excess of organic substances in stagnant water. Gyttjae in essence forms at the oxygen–hydrogen sulfide interface in fresh sediment with the water above sufficiently oxygen-rich to allow survival of algae and animals and for the formation of colloidal humic solutions called dy. The notion of a reducing environment for sapropelic coals is a general belief. Westoll Ž1968. cited a reducing environment as the reason for the dominance of vertebrate fauna in cannel coals compared with humic coals. A review of the literature shows that many authors give variations to this main theme. For example, Falcon and Snyman Ž1986. considered that sapropelic coals, and therefore

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

177

cannel coals by definition, have their origins in ‘open or deeper water’. However, elsewhere in the same publication, they stated that cannel coals are typically formed in ‘broad shallow lakes surrounded by vegetation’. With changing water level, cannel coals grade laterally and vertically into humic coals. Bustin et al. Ž1983. suggested that cannel coal and torbanite accumulate in shallow basins. Moore Ž1968. stated spores were an important constituent of cannel coals but algae were occasionally present when ‘algal cannels have been described’. He also stated that there is a gradation from cannel coal through boghead-cannel to boghead Žs torbanite. where a boghead cannel is presumed to have subequal amounts of spores and algae. Moore’s conclusions were based on studies by Sullivan Ž1959. who concluded that abrupt changes in the spore content of cannel coals compared with humic coals reflected changes in vegetation that in turn were caused by an abrupt environmental change due to marginal downwarping with flooding of the lower regions occupied by ferns. Sullivan also noted that cannel-boghead of the Flint Cannel Coal Seam at Flintshire, England, formed as a marginal facies whereas a torbanite formed 2 miles Ž3 km. away in the center of the basin. Diessel Ž1992. stated transitions from densosporite facies into sapropelic coals, as noted by Sullivan and reported in Moore Ž1968., are gradations from deposition of limnotelmatic environments into deeper water beyond the reach of rooted vegetation, where detrital or transported sediments are deposited. Thus, Diessel believed torbanites are also deeper water facies. Sullivan Ž1959. also attributed the preservation of spores in cannel coals to stagnant water. 4.3.1. Sporinite-rich coals Based on petrographic data from this study, cannel coals were apparently probably formed in several environments. The sporinite–inertinite–vitrinite coal differs from typical Carboniferous Kentucky humic coals only in that they contain an above average sporinite content. There is little difference in the textures and compositions of the humic macerals. This is interpreted as indicating that the SIV coal forms in the same environment as humic coals and that the increased sporinite content is an aberration resulting from such factors or phenomenon as an unusually high reproductive rate or climatic conditions. This implies that the factors controlling the input of sporinite were minor perturbations on the normal cycle of events and that the SIV coals are in reality humic coals that do not fit the normal statistical composition of humic coals. A similar environment is envisaged for some, but not necessarily all, sporinite–inertinite– Žmicrinite. –vitrinite cannel coals. These coals have the normal humic coal maceral composition but lack the coarser texture of those coals. Of interest is the abundance of micrinite. It is generally stated that micrinite forms from liptinite and vitrinite through disproportionation reactions which produce liquid and gaseous hydrocarbons ŽTeichmuller, 1974; Stach et al., 1982; Tissot and Welte, 1978, 1984; Ward, ¨ 1984; Diessel, 1992.. Less traditional mechanisms include sizing of coagulated humic matter into granular vs. massive forms through a cell wall filtration mechanism ŽSchopf, 1971. and derivation from semi-opaque granular materials in plant tissues in peat ŽSpackman and Barghoorn, 1966; Cohen and Spackman, 1980., suggesting an original primary plant structure or secretion. The main reason for the disproportionation hypothesis is the common association of micrinite with sporinite, exsudatinite and vitrinite.

178

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

Ward Ž1984. suggested that the micrinite derived from vitrinite formed from cell walls. Again, the main reason was the occurrence of micrinite as cell fillings in vitrinite. Tissot and Welte Ž1978, 1984. suggested that highly reflecting micrinite formed at a vitrinite reflectance 0.8 to 1.0%, the rank at which maximum petroleum generation occurs. Taylor and Liu Ž1989. and Taulbee et al. Ž1991. opted for a modified Teichmuller ¨ scheme by which disproportionation of bitumen produced lighter hydrocarbons and an opaque residue, micrinite. Taylor and Liu used transmitted electron microscopy ŽTEM. to identify several forms of micrinite. The form observed with the optical microscope and that which is the micrinite in Kentucky cannel coals consists of aggregates of submicron grains. Where the aggregates are large enough, they are visible with optical microscopy. Submicron, and therefore micrinite aggregates, formed from disproportionation of oil droplets, presumably formed from degraded liptinite macerals. The evidence for this was suggested to be the close association of degraded liptinite, especially alginite, with micrinite. Taulbee et al. Ž1991. argued that formation of micrinite from bitumen accounted for: Ø the occurrence of micrinite adjacent to the outer walls of macerals or within the walls of sporinite; Ø Teichmuller’s observations that micrinite be most commonly found in coals that ¨ reached a rank above that required for the onset of oil generation; and Ø represented a plausible explanation for the high reflectance of micrinite and the relatively high HrC and low density found in their study. Shibaoka Ž1978. published a comprehensive study of micrinite in Australian coals and raised some problems with the Teichmuller hypothesis. An important observation ¨ was the coexistence of resinous cell fillings, or any other form of liptinite, and micrinite does not prove a cause and effect relationship. Shibaoka suggested that porigelinite might be a possible precursor for micrinite although no mechanism was given. Porigelinite is finely porous to granular vitrinite found in low rank coals, commonly infilling cell lumens as shown in Shibaoka Ž1978; Fig. 4. and Stach et al. Ž1982; Fig. 74a wwith the contrast in color and reflectance between the ‘porigelinite’ and textiniterphlobaphinite in this photograph, the porigelinite is deceptively like micrinitex.. Plate 15 ŽFig. 5. in Falcon and Snyman Ž1986. showed cell lumens, typical of those filled with phlobaphinite and porigelinite, filled with micrinite. Five out of the six photographs showing micrinite in Falcon and Snyman have abundant mineral matter of probably detrital origin. Mineral matter of this type is brought into the peat mire by floods, which contain abundant oxygen. It is reasonable to suppose that in a peat mire, in the presence of oxygenated water, micrinite could form from porigelinite through oxidation reactions. Stach et al. Ž1982. stated that apart from alginite, micrinite is one of the characteristic macerals of Carboniferous boghead coals. This study of the Kentucky coals suggests there is a transition from humic coals to ‘cannel coals’ with abundant sporinite andror micrinite with minor to abundant telalginite. Micrinite is dispersed throughout the microlithotypes, especially if telalginite is present or occurs in pods and lenses, especially in vitrinite. In the latter types, the textures are similar to those shown in Shibaoka Ž1978; Figs. 1, 2 and 4. and Stach et al. Ž1982; Fig. 47 and plate 1, Fig. 1.. Similar occurrences are also found in typical humic coals, very abundantly in many samples. It is therefore inconsistent that a sapropelic environment is conducive to

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

179

micrinite formation instead of a peat mire. In addition, for micrinite to form by either the Teichmuller hypothesis or the Taylor and LiurTaulbee et al. hypothesis, the precursors ¨ and conditions need to be the same for both the humic and sporinite-rich coals. Derivation of micrinite from porigelinite by oxidation, as proposed by Shibaoka, is the preferential mechanism for the Kentucky sporinite-rich coals. To support the Taylor and LiurTaulbee et al. hypothesis would require an abundance of micrinite in the telalginite–bituminite ŽBT. assemblage given that Rock-Eval shows this coal to have by far the largest amount of free hydrocarbons, and therefore the most organic matter from which micrinite could be formed. In sporinite-rich coals, micrinite could just as easily form by the oxidation of liptodetrinite as by the Teichmuller method, especially if it is ¨ shown that micrinite is an oxidation product of porigelinite. The fine-grained texture of the sporinite-rich Kentucky coals does not require the textbook environment of an open or deeper-water, broad, shallow lake surrounded by vegetation or shallow basin, if the organic matter is comminuted before accumulation. Comminution could be by mechanical degradation. Dispersed organic matter Ždom. in petroleum source rocks is commonly vitrodetrinite and inertodetrinite of similar size to the humic macerals in SIMV and cannel coals. In source rocks, grain size of clastic grains is variable ranging from fine-grained shale and siltstone to coarser sandstone. The environments for these rocks vary from high-energy environments to quiet lacustrine and shallow basins, but the vitrodetrinite and inertodetrinite in each type of rock are commonly the same. The common factor in each case may be the finely-divided nature of the humic macerals. Petrographic studies clearly show that plants colonized the precursor ‘organic mud’ of some cannel coals before compaction. At least two samples of the studied coals show obliquely crosscutting vitrinite that, likely, resulted from compaction of a subvertical structure such as a root. In hand specimens of torbanite from Australia, the Permian fossil Vertebraria is clearly visible in many samples; this also shows that plants that later became incorporated into the coals above the torbanite lens could colonize the precursor torbanite ‘peatrorganic mud’. Other samples of SIMV coal from Kentucky have large vitrinite clasts parallel to bedding. Given that many coal-forming plants of the Carboniferous Period had horizontal roots, these vitrinite structures could also be interpreted as roots. Alternatively they could represent large stems, branches and trees incorporated into the coal ‘peat’ after breaking and falling from trees. It is unlikely that such structures were transported into the basin given the interbedded textures shown in polished blocks; the simplest explanation is they represent parts of vegetation growing in the cannel-coal peat. If the roots were growing at the time of deposition, this could be interpreted to show that there was not a large body of open water at the time of deposition. Alternatively, roots could penetrate the sapropelic mud from overlying humic swamps or from plants developed on clastic substrates. 4.3.2. Alginite-bearing coals Telalginite derived from Botryococcus algae is found in two maceral assemblages— the telalginite–inertinite–vitrinite ŽTIV. assemblage and the bituminite–telalginite ŽBT. assemblage. In both cases, the telalginite is a less-important, subsidiary maceral com-

180

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

pared with the inertinitervitrinite ŽTIV assemblage. and bituminite ŽBT assemblage.. Coals with either assemblage probably formed in shallow lakes as envisaged for the classic cannel coal. Botryococcus is a colonial green alga consisting of unicellular algae surrounded by inner membranes of soft cellulose enclosed in a bipartite outer structure of mucilaginous pectic substances and fatty materials ŽBlackburn and Temperley, 1936.. It has been found in many fresh water lakes, peat and older sedimentary rocks of Tertiary age. The older genera of Reinschia and Pila are thought to be fossil forms of the extant Botryococcus. Rare Botryococcus-derived telalginite in some SMIV coal does require open water. Falcon and Snyman Ž1986. reported Botryococcus requires open water, which does not have a high humic acid content. It was assumed that torbanites were deposited mainly toward the centers of small swamps or lakes, with cannel coals toward the lake margins, because the Pila and Reinschia algae needed oxygen levels that are only found toward the centers of lakes, that is, a certain minimum distance from the shore, where fewer organic substances flowed into the lakes. This incidentally also accounts for the lower ash content of torbanite compared with cannel coal. Clearly the ash content argument is tenuous. Many cannel coals have very low ash that, using the above argument, implies that the latter must have formed nearer the center of the lake. Also, humic coals have variable ash content that, by analogy, would be related to proximity, or otherwise, to the swamp margin. This doubtful hypothesis is hard to prove. Bauld Ž1986. argued that deposits of extant Botryococcus accumulate as wind-blown accumulations and thus suggested that wind might play a significant role in the accumulation of Reinschia and Pila during the formation of torbanites. As an alternative view, van Krevelen Ž1981. cited Potonie´ Ž1910. as stating that torbanite genesis is a transition stage between coal and mineral oil. Stach et al. Ž1982., and many other authors, have cited the recent rubbery materials balkashite ŽKazakhstan. and coorongite ŽAustralia. as modern precursors of torbanite. Coorongite is generally believed to be derived from Botryococcus algae ŽThiessen, 1925; Cane and Albion, 1971; Stach et al., 1982.. Cane and Albion argued the chemistry of coorongite showed the algae had undergone considerable microbial degradation with the implication that torbanite should not be considered to have been derived from a single source. Glikson Ž1984. also argued that coorongite was derived from a single algal source. The Botryococcus algae in coorongite had been altered by bacterial activity and diatoms were also present. Glikson suggested that torbanite was ‘‘composed of an organism reminiscent of mucilaginous material; of blue green algae Žcyano-bacteria. and occasional dense accumulations of cysts attributable to methanogenic bacteria’’. Whereas the presence of methanogenic bacteria is not disputed, the bulk of evidence that has accumulated since the pioneering studies of David Ž1889., Zalessky Ž1914. and Thiessen Ž1925. unequivocally suggests a green algal source, namely Botryococcus or its fossil forms of Reinschia and Pila as the precursors of torbanite. As to the validity of balkashite as a precursor of torbanite, comment is not given. However, coorongite is unlikely to be a precursor for torbanite for several reasons. The last formation of coorongite was in 1962 when ephemeral lakes of the Coorong area of southeastern South Australia were flooded by the Murray River. Coorongite formed and is still found as a rubbery black material on the surface or within the upper sandy layers

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

181

of the lake bed or dunes. The ephemeral lakes were clearly not as salty as the existing Coorong lakes in which black gelatinous masses of algae accumulate from time to time. What is more important, the lakes were ephemeral and virtually no humic matter was deposited with the algal matter. Any flood-deposited logs and debris have, or will, decay and oxidize with time. None is likely to be converted into coaly material. If the coorongite is an analogue for torbanite, why are there not coal precursors associated with it? Almost without exception, part, or all, of torbanite deposits are lenses associated with coal. In the Coorong area, the lakes evaporated long before any peat could form and the subsequent coalification processes take place. The coorongite was a curio, an aberration or an erratic event in the normal cycle of events, caused by an unusually wet climatic incident that produced high-nutrient, ephemeral lakes suitable for Botryococcus blooms. Millais and Murchison Ž1969. reported the type of coal formed in a shallow basin depends on the proportion of three classes of material: clastic detritus brought in by rivers, terrestrial organic matter, and dissolved mineral salts. Torbanite forms if the terrestrial organic matter input is low, thus permitting algal growth. For coorongite, the lakes do not even meet the criterion of a shallow basin because of their ephemeral nature. Given the ephemeral nature of the Coorong lakes, anticipating sufficiently large enough rates of sedimentation to cover the coorongite, and thus preserve it for future coalification, is difficult. Thiessen Ž1925. reported that coorongite was also found in the Coorong lakes in 1865, apparently the next most recent deposit of this material. With deposits as far apart as almost 100 years, we doubt that sufficient coorongite would accumulate to form a sufficiently thick deposit to be coalified into torbanite. A more constant body of water is probably required. The great variation in the abundance of telalginite in coals, ranging from - 1% to the dominant maceral Žin a boghead coal or a torbanite., suggests that the SIMV and TIV cannel coals may be end members of a transitional series, both of which accumulated in small depressions or lakes in the peat mire. In the Fraser Delta small ponds are formed after fires burn into the peat ŽBustin et al., 1983.. This could be one mechanism for producing the algal-inhabiting ponds or lakes needed to form cannel coals. Another mechanism could be atypically large floods that erode into the peat. Floods might also be the mechanisms by which abundant clay minerals, large grains of detrital quartz, other minerals and large pieces of woody tissue Žthe precursors of semifusinite and fusinite in cannel coal. are deposited in peat mires. Pyrite is generally reported to be a common constituent of cannel coal. Euhedral and some framboidal pyrite are probably of primary origin but some framboidal pyrite could be either primary or secondary. Clearly some euhedral pyrite is of secondary origin as it infills fractures in vitrinite and replaces clay minerals and organic matter. In the Alpha torbanite deposit ŽQueensland, Australia., pyrite replaces Reinschia colonies uncompacted at the time of replacement. An interesting point of note is the relatively low sulfur contents, usually less than 1%, in the cannel coal data provided by Ashley Ž1918.. The sulfur values seem inconsistent with the commonly held view that pyrite is abundant in cannel coals. Of course, as with any coal deposit, the highest quality of the most accessible deposits was mined first. Siderite is also found in some cannel coal and was obviously formed as an early-stage mineral before compaction as the organic laminae are draped around the nodules of

182

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

siderite. This is consistent with Stach et al. Ž1982. who remarked that siderite was generally more abundant in cannel coals than in humic coals because of the high pH in the gyttjae stage. The presence of Botryococcus-derived telalginite in the B–T coals, particularly the Breckenridge coal, requires open water. The precursors for, and the formation of bituminite, are equivocal. However, in BT cannel coal, bituminite is unlikely to be derived from Botryococcus-related algae. Telalginite is derived from these algae and is very well preserved as suggested by the preservation of primary cell structure in many colonies. Thus, if bituminite is derived from algae, the algae must be of a different type. Taylor et al. Ž1989. argued that some liptinite in Permian Gondwana coals was derived from lamalginite precursors. However, in oil shales that contain lamalginite, the morphology of the lamalginite is quite different to that in the Permian coals suggesting that the Taylor et al. hypothesis is not correct for the Breckenridge coal. Bituminite is the dominant maceral in the Breckenridge coal. Understanding how this maceral is formed helps to interpret the environment of deposition for this coal. Stach et al. Ž1982. stated that bituminite is a characteristic maceral of sapropelic coals, citing the study of the Katharina seam in the Ruhr of Germany ŽDiessel, 1961.. Several references are made to bituminite and its origin in Stach et al. Ž1982.. Much of the accepted understanding of the origin of bituminite, and the division of bituminite into Types I, II Ž1974.. She concluded that bituminite and III, has to be attributed to Teichmuller ¨ represents bacterial decomposition products derived from algae and plankton, with some bacterial biomass ŽTeichmuller, 1989; Taylor and Liu, 1991.. Precursors of bituminite in ¨ bogheads and cannel coals are attributed to fat- and protein-rich plankton, with fish scales, amphibian and insect remains also contributing to the muds. The fats and proteins form ‘diffuse bituminous matter’ which later becomes bituminite ŽStach et al., 1982.. Experimental work by Masran and Pocock Ž1981. reported amorphous material, Ž1989. interpreted as bituminite, could be produced from terrestrial which Teichmuller ¨ organic matter through physical, chemical and biogenic breakdown. Several forms of bituminite, which occurs with micrinite in many samples, have been defined especially for marine oil shales and black shales. Bituminite I has stronger fluorescence than bituminite II and III and is regarded as a decomposition product of algae; bituminite II is bacterially altered plant lipids and decomposition products of phytoplankton and zooplankton and bituminite III is degraded humic and liptinite derived from terrestrial plants ŽSnowdon et al., 1985.. Given et al. Ž1985. studied the King Cannel coal from southwest Utah, a coal containing both bituminite Žup to 53.4%. and telalginite Žup to 6.7%.. They argued that the bituminite formed from algal remains. The proposed mechanism was degradation of algal bodies by a bacterial bloom that coexisted with, but was below, the Botryococcus bloom. This mechanism also depleted the oxygen content of the water providing reducing conditions under the bacterial bloom, permitting further extensive degradation. The hypothesis was based partly on the recognition of algal bodies, some that were partly degraded whereas others were morphologically whole colonies. Snowdon et al. Ž1985. studied liptinite-rich needle coals from British Columbia, Canada that contained up to 99% liptinite, mostly bituminite II and III. They stated that bituminite formed from alginite, resinite, sporinite or cutinite during coalification.

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

183

Alternatively, bituminite formed through chemical or bacterial decomposition of animal, planktonic or bacterial lipids. The favored source for the bituminite in the needle coals was homogenization, and therefore bituminite formation, of non-algal lipids. The mechanism was extensive microbial degradation that selectively removed lignin and cellulose, leaving the liptinite components that were less susceptible to alteration. Puttman et al. Ž1994. proposed that the degradation of Botryococcus algae is related ¨ to the ferrous ion concentration in pore waters. In a study of the coals and oil shales in the upper Carboniferous strata of the Pictou Coalfield, they found alginite where siderite was least abundant and bituminite where siderite was most abundant. They concluded excess of ferrous ions in the pore water has a negative affect on the stability of the Botryococcus cell walls and ‘‘ . . . Obviously, the amount of siderite governs the degree of algae and vice versa’’. The mechanism for degradation of the algae was through bacteria using the algal cell walls as a food substrate and it was immaterial whether some sulfate-reducing or methanogenic bacterium was the organism. Taylor and Liu Ž1989. concluded that bituminite in a high volatile bituminous coal was derived from biodegraded lipid-rich algal colonies that were probably former single cells. The biodegradation resulted in preferential removal of the cell walls of the algae leaving a lipid-rich residue, particularly as globules less than 1-mm thick, and ultra-fine microbial and algal degradation products. In marine oil shales, the precursors of bituminite are algae. Robl et al. Ž1987. found an inverse relationship between alginite derived from marine organisms and bituminite in the Cleveland Member of the Ohio Shale in northeastern Kentucky and concluded bituminite was formed by bacterial degradation of alginite. Stasiuk Ž1993. studied the Devonian and Mississippian sequence of the Williston Basin, Canada, and attributed the formation of bituminite II to the degradation of phytoplankton organisms within the water column and at the water–sediment interface. In neither case is iron concentration regarded as an important part of the mechanism and siderite is not a significant mineral, if present at all, in either sequence. Although some samples of the cannel coals studied contain siderite, the Breckenridge coal does not have significant siderite and it is unlikely that this is a plausible mechanism for the formation of bituminite in the Breckenridge coal. Humic precursors have also been suggested for bituminite in coal. If this is the case, then an explanation is needed on why desmocollinite and other vitrinite accumulated besides the bituminite. The presence of both bituminite and vitrinite requires some sort of selection process whereby part of a precursor is destined to be vitrinite and other part is destined to be bituminite. Alternatively, there were two types of woody precursors, one producing vitrinite and the second bituminite. Moore Ž1968. cited the work of Drath Ž1939. who stated that algal remains accumulated under the ‘aegis of an oxidizing water layer’ with consequent drying and desiccation of the algal bodies permitting colonization by fungi. Drath attributed the alginite and matrix Žwhich he called eualginite. to algal precursors. The eualginite is probably equivalent to bituminite. Bouska ˇ Ž1981., citing Svoboda and Benesˇ Ž1955., stated that cannel coals form under water in a reducing environment in the bottom part of the peat bog, whereas true peat is deposited in the upper parts of the bog in an anaeroboic and mixed environment. Where trees dominate, an aerobic environment predominates and woody peat develops. This hypothesis as-

184

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

sumes the difference between cannel coal and humic coal formation is due to stratification and both form simultaneously. This hypothesis fits the geometry of cannel coals that occur under humic coals. Sapropelic coals do not always represent abrupt changes in the environment. Hower et al. Ž1987. noted thin-banded vitrinite mixed with bituminite layers at the base of two cores suggesting a very significant initial woody plant input to the basin. The vitrinite in one core decreased from 48% at the base of the core to a range of 11%–17% higher up. Both cores showed fluctuations in the bituminite and telalginite contents suggesting variations, on a microscale, in the input of the precursors for the two macerals. In one core, the telalginite content increases steadily upwards, whereas in the second core the central part of the core had the highest alginite content. The variations in alginite content can be attributed to either variations in the rate of preservation or, more likely, changes in the input of dead algae. If the latter are correct, it implies that water conditions, such as depth andror salinity, changed during the life of the lake in which the Breckenridge coal formed. After reviewing the various models published, the model for the formation of coals with alginite-rich assemblages, which were probably most of the coals worked as cannel coals in the 1800s, envisages a shallow lake or depression in a peat swamp with physically comminuted woody material derived from the margins of the lake. As summarized by Ashley Ž1918., the ‘‘greater the admixture of woody or peaty material derived from the usually adjoining peat marshes, the more closely the cannel resembles chemically the associated bituminous coal and the smaller the proportionate yield of oil by distillation.’’ Some least oxidized woody material would be further degradedraltered to form matrix desmocollinite. More oxidized woody material would be transposed into inertinite. The maceral composition of the coal would depend on the relative input of terrestrial humic material, terrestrial liptinite, algae and clastic detritus. Where algal input was high, torbanite formed; where terrestrial organic matter input was high, then algal-bearing coals formed; where spores and pollens were major components, cannel coals formed. For most coals, the liptinitic precursor accumulated as a steady input of spores, resins, waxes and algae with some clastic detritus. The alginite-rich coals, with perhaps at least 20% telalginite, formed after algal blooms. Perhaps the most important criteria are the development of a small basin, the relative height of the water table and an influx of nutrients to provide ideal conditions for Botryococcus blooms.

5. Summary This study of Kentucky cannel coals showed that, based on liptinite content, four maceral assemblages can be recognized: Ži. SIV—sporinite with abundant medium-grained vitrinite and inertinite Žmicrinite is a minor component only.; Žii. SIMV—sporinite with fine-grained vitrinite and inertinite including abundant micrinite Žbituminite may be present.; Žiii. TIV—alginite with abundant fine-grained vitrinite and inertinite; and, Živ. BT—alginite and bituminite with minor vitrinite and inertinite.

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

185

The boundaries between the groups are poorly defined and there is a continuum of coal types ranging from humic coals to two definitive end members, one with predominantly telalginite derived from Botryococcus and another with predominantly bituminite. Coals with assemblages Ži. and Žii. are humic coals with, sometimes, above average sporinite contents. Most do not fit the definition for cannel coals. Groups Žiii. and Živ. also are not cannel coals if the definition is used rigorously. Only 14 coals with maceral assemblages Ži. and Žii. contained more than 20% sporinite and, therefore, can be said to have abundant liptinite using the generally accepted definition of a cannel coal. Based on the literature review undertaken on ‘cannel coals’, and the petrographic data obtained for the Kentucky coals, it is suspected that true cannel coals are extremely rare. Many, if not most of the coals alluded to as cannel coals in the literature, contain algal components and therefore should not be included in the cannel coal group. The recognition of complex classification systems for sapropelic coals, most of which have arbitrary boundaries, is not warranted. Classifications, such as cannel coal, boghead cannel, and boghead, lack petrographic substance. Ten coals contained telalginite derived from Botryococcus algae; maximum telalginite content was 23%. Given the petrography of the samples examined, most of the high yielding ‘cannel coals’ used in the 1800s for heating, oil production and gasification were probably not true cannels as defined but were torbanites. The high volatile contents were a function of telalginite content, as well as the bituminite content in the case of the Breckenridge coal, rather than sporinite or other terrestrially derived liptinite. Rock-Eval data show that five cannel coals have excellent source rock potential as indicated by high S2 and HI values. The Breckenridge coal, which is composed of bituminite, telalginite and vitrinite has the best source rock potential. The high free hydrocarbon and pyrolysed hydrocarbon production from this coal underline the reason it was a favored coal for the fledgling ‘oil from coal’ industry in the United States in the 1800s.

Acknowledgements This study was completed at the Center for Applied Energy Research ŽCAER., University of Kentucky, while the first listed author was on study leave. The authors thank the CAER for financial support to complete the study. Maria Mastalerz and Robert Rathbone reviewed the manuscript.

References Ashley, G.H., 1918. Cannel coal in the United States. US Geol. Survey Bull. 659, 127. Bauld, J., 1986. Botryococcus-sourced oil shale and petroleum: a palaeoenvironmental model based on ecological considerations. 12th Int. Sedimentol. Congr. Abs., 24–30 August, 1986, 23. Blackburn, K.B., Temperley, B.N., 1936. Botryococcus and the algal coals. Trans. R. Soc. Edinburgh. LVIII, 841–868. Bouska, ˇ V., 1981. Geochemistry of Coal. Elsevier, Amsterdam, 284 pp.

186

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

Bustin, R.M., Cameron, A.R., Grieve, D.A., Kalkreuth, W.D., 1983. Coal petrology. Its Principles, Methods, and Applications. Geol. Soc. Can., Short Course Notes, Vol. 3, pp. 271. Cane, R.F., Albion, P.R., 1971. The phytochemical history of torbanites. Proc. R. Soc. NSW 104, 31–37. Cohen, A.D., Spackman, W., 1980. Phytogenic organic sediments and sedimentary environments in the Everglades–Mangrove complex of Florida: Part III. The alteration of plant material in peats and the origin of coal macerals. Paleographica 172, 125–149. Crisp, P.T., Ellis, J., Hutton, A.C., Korth, J., Martin, F.A., Saxby, J.D., 1987. Australian Oil Shales: A Compendium of Geological and Chemical Data. University of Wollongong, 109 pp. David, T.W.E., 1889. Note on the origin of kerosene shale. Proc. Lin. Soc. NSW 4, 483–500. Diessel, C.F.K., 1961. Zur Kenntnis der Bildungsweise des Flozes ¨ Katharina im Niederrheinisch-Westfalischen ¨ Steinkohlenbecken. Bergbau-Arch 22, 57–82. Diessel, C.F.K., 1992. Coal-bearing Depositional Systems. Springer, Berlin, 721 pp. Drath, A., 1939. Boghead coals from Radzionkow. Bull. Inst. Geol. Poland 21, 1–16. Dulhunty, J.A., 1951. Occurrence and origin of Australian torbanites; in Institute of Petroleum, Vol II. Institute of Petroleum, London. 109–113. Falcon, R.M.S., Snyman, C.P., 1986. An Introduction to Coal Petrography: Atlas of Petrographic Constituents in the Bituminous Coals of South Africa. Geological Society of South Africa, Review Paper No. 2., 27 pp. Garry, M., McAfee, R., Jr., Wolf, C.L., 1977. Glossary of Geology. American Geological Institute, Washington, D.C., 805 pp. Gesner, A., 1865. Practical Treatise on Coal, Petroleum, and other Distilled Oils, 2nd edn. Balliere Bros, New York, p. 8. Given, P.H., Mudumburi, Z., Shadle, L.J., 1984. Structural features of a Cretaceous coal of algal affinities. Am. Chem. Soc. Fuel Div. Preprints 29 Ž6., 1–9. Given, P.H., Davis, A., Kuehn, D., Painter, P.C., Spackman, W., 1985. A multifaceted study of a Cretaceous coal with algal affinities: I. Provenance of the coal samples and basic compositional data. Int. J. Coal Geol. 5, 247–260. Glikson, M., 1984. Microbiological precursors of coorongite and torbanite and the role of microbial degradation in the formation of kerogen. Org. Geochem. 4 Ž3r4., 161–172. Han, Z., Crelling, J.C., 1993. Observations on the petrology of sapropelic coals. 10th Annual Meeting of TSOP, Abs and Program, Norman, Oklahoma, October 9–13, 1993. Hower, J.C., 1995. Uncertain and treacherous: the cannel coal industry in Kentucky. Nonrenewable Resour. 4 Ž4., 310–324. Hower, J.C., Taulbee, D.N., Poole, C., Kuehn, D.W., 1987. Petrology and geochemistry of the Breckenridge seam—A torbanite from Western Kentucky. 1986 Eastern Oil Shale Symp., Nov. 19–21, 1986. Hutton, A., 1990. Classification, organic petrography and geochemistry of oil shales. Proc. 1990 Eastern Oil Shale Symp., November 6–8, 1990, Institute for Mining and Minerals Research, pp. 163–173. Hutton, A.C., Cook, A.C., 1980. Influence of alginite on the reflectance of vitrinite from Joadja, NSW, and some other coals and oil shales containing alginite. Fuel 59, 711–719. Hutton, A., Madre, D., 1990. Alpha torbanite deposit, Queensland, Australia. Proc. 1990 Eastern Oil Shale Symp., November 6–8, 1990, Institute for Mining and Minerals Research, pp. 195–203. International Committee for Coal Petrology, 1963. International Handbook of Coal Petrology. Centre National de la Recherche Scientifique, Paris. International Committee for Coal Petrology, 1971. International Handbook of Coal Petrology, 1st suppl., 2nd edn. Centre National de la Recherche Scientifique, Paris. International Committee for Coal Petrology, 1975. International Handbook of Coal Petrology, 2nd suppl., 2nd edn. Centre National de la Recherche Scientifique, Paris. Kalkreuth, W.D., Macauley, G., 1984. Organic petrology of selected oil shale samples from the Lower Carboniferous Albert Formation, New Brunswick, Canada. Bull. Can. Pet. Geol. 32, 38–51. Kalkreuth, W.D., Macauley, G., 1986. The organic petrology and geochemistry of Carboniferous oil shales from eastern Canada. Proc. 1986 Eastern Oil Shale Symp., Lexington, November 19–21, 1986, pp. 257–265. Katz, B.J., 1983. Limitations of ‘Rock-Eval’ pyrolysis for typing organic matter. Org. Geochem. 4 Ž3r4., 195–199. van Krevelen, D.W., 1981. Coal. 2nd Impression. Elsevier, Amsterdam, 514 pp.

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

187

Macauley, G., Snowdon, L.R., Ball, F.D., 1985. Effects of maturation on hydrocarbon recoveries from Canadian oil shale deposits. Proc. 19th Oil Shale Symposium, Colorado School of Mines, pp. 1–8. Mansfield, L.F., 1905. Cannel coal in the United States. US Geol. Surv. Bull. 659, 127. Masran, Th.C., Pocock, St.A.J., 1981. The classification of plant derived particulate organic matter in sedimentary rocks. In: Brooks, J. ŽEd.., Organic Maturation Studies and Fossil Fuel Exploration. Academic Press, London, pp. 157–17. Mastalerz, M., Hower, J.C., 1996. Elemental composition and molecular structure of Botryococcus alginite in Westphalian cannel coals from Kentucky. Org. Geochem. 24 Ž3., 301–308. Mather, W.W., 1839. Report on the geological reconnaissance of Kentucky made in 1838. Kentucky Geological Survey. Millais, R., Murchison, D.G., 1969. Properties of coal macerals: infra-red spectra on alginites. Fuel 48, 247–258. Moore, L.S., 1968. Cannel coals, bogheads and oil shales. In: Murchison, D., Westoll, T.S. ŽEds.., Coal and Coal-bearing Strata. Elsevier, New York, pp. 19–29. Ottenjahnn, K., 1988. Fluorescence alteration and its value for studies of maturation and bituminization. Org. Geochem. 12, 309–321. Peters, K.E., 1986. Guidelines for evaluating petroleum source rock using programmed pyrolysis. Am. Assoc. Pet. Geol. Bull. 70 Ž3., 318–329. Platt, W.G., 1878. Report of progress in Indiana County. Penn. 2nd Geol. Surv. Rep. H4, 228-231. Potonie, wie des Torfes, der ´ H., 1910. Die Entstehung der Kohle und der Kaustobiolithe uberhaupt, ¨ Braunkohle, des Petroleums, u.s.w., Berlin. Price, L.C., Barker, C.E., 1985. Suppression of Vitrinite Reflectance in Amorphous Kerogen Rich—A Major Unrecognised Problem, Vol. 8, pp. 59–84. Puttman, W., Sun, Y.Z., Kalkreuth, W., 1994. Variation of petrological and geochemical compositions in a ¨ sequence of humic coals, cannel coals, and oil shales. Energy Fuels 8, 1460–1468. Robl, T.L., Taulbee, D.N., Barron, L.S., Jones, W.C., 1987. Petrologic chemistry of a Devonian Type III kerogen. Energy Fuels 1, 507–513. Rouzard, J.N., 1984. Relations entre la microtexture et les proprietes carbones—Application a` la ´ ´ des materiax ´ ´ caracterisation des charbons. Thesis, University of Orleans, 150 pp. ´ Schopf, J.M., 1971. Comment about the origin of micrinite. Econ. Geol. 66, 1153–1156. Shibaoka, M., 1978. Micrinite and exsudatinite in some Australian coals, and their relation to the generation of petroleum. Fuel 57, 73–77. Snowdon, L.R., Brooks, P.W., Goodarzi, F., 1985. Chemical and petrological properties of some liptinite-rich coals from British Columbia. Fuel 65, 459–472. Spackman, W., Barghoorn, E.S., 1966. Coal Science. Adv. Chem. Series, Am. Chem. Soc. 55, 695–707, Washington D.C. Stach, E., Mackowsky, M.-Th., Teichmuller, M., Taylor, G.F., Chandra, G., Teichmuller, R., 1982. Stach’s ¨ ¨ Textbook of Coal Petrology, 3rd edn. Gebruder ¨ Borntraeger, Berlin, 535 pp. Stasiuk, L.D., 1993. Algal bloom episodes and the formation of bituminite and micrinite in hydrocarbon source rocks; evidence from the Devonian and Mississippian, northern Williston Basin, Canada. Int. J. Coal Geol. 24, 195–210. Sullivan, H.J., 1959. The description and distribution of miospores and other microfloral remains in some sapropelic coals and their associated humic coals and carbonaceous shales. PhD Thesis, University of Sheffield. Svoboda, J.V., Benes, ˇ K., 1955. Petrografie uhlı. ´ NCSAV, Praha, 262 pp. Taulbee, D.N., Hower, J.C., Greb, S.F., 1991. Examination of micrinite concentrates from the Cannel City coal bed of eastern Kentucky; proposed mechanism of formation. Org. Geochem. 17 Ž4., 557–565. Taylor, G.H., Liu, S.Y., 1989. Micrinite—its nature, origin and significance. Int. J. Coal Geol. 14, 29–46. Taylor, G.H., Liu, S.Y., 1991. Bituminite—A TEM view. Int. J. Coal Geol. 8, 71–85. Taylor, G.H., Liu, S.Y., Diessel, C.F.K., 1989. The cold-climate origin of inertinite-rich Gondwana coals. Int. J. Coal Geol. 11, 1–22. ¨ Teichmuller, M., 1974. Uber neue macerale der liptinit-Gruppe und die Enstehung des Micrinits. Fortschr. ¨ Geol. Rheinl. U. Westfalen 24, 37–64. Teichmuller, M., 1989. The genesis of coal from the viewpoint of coal petrology. Int. J. Coal Geol. 12, 1–87. ¨

188

A.C. Hutton, J.C. Howerr International Journal of Coal Geology 41 (1999) 157–188

Thiessen, R., 1925. Origin of boghead coals. US Geol. Surv. Prof. Paper. 132 I, 121–138. Tissot, B.P., Welte, D.H., 1978. Petroleum Formation and Occurrence. Springer, Berlin, 538 pp. Tissot, B.P., Welte, D.H., 1984. Petroleum Formation and Occurrence, 2nd edn. Springer, Berlin, 582 pp. Ward, C.R., 1984. Coal Geology and Coal Technology. Blackwell Scientific Publications, Melbourne, 345 pp. Westoll, T.S., 1968. Vertebrate faunas of coal-bearing strata. In: Murchison, D., Westoll, T.S. ŽEds.., Coal and Coal-bearing Strata, Elsevier, New York, pp. 179–193. Wolf, M., Wolff-Fischer, E., 1984. Alginit in Humuskohlen karbonischen Alters und sein Einfluss auf die optischen Eigensschaften des begleitenden Vitrinits. Gluckauf-Forschungsh. 45, 243–246. Zalessky, M.D., 1914. On the nature of the yellow bodies of boghead, and on sapropel of the Ala-Kool Gulf of the Lake Balkash. Com. Geol. ´ Bull. 33, 495–507.