Petrology, Rock-Eval and facies analyses of the McLeod coal seam and associated beds, Pictou Coalfield, Nova Scotia, Canada

Authors

  • J. Paul Geologisches Institut der Universitdt Koln, Zulpicherstr. 49, 5 Koln 1, Germany
  • W. Kalkreuth Institute of Sedimentary and Petroleum Geology, Geological Survey of Canada, 3303-33rd Street N.W., Calgary, Alberta T2L 2A7, Canada
  • R. Naylor Nova Scotia Department of Mines and Energy, 1701 Hollis Street, Halifax, Nova Scotia B3J 2X1, Canada
  • W. Smith Nova Scotia Department of Mines and Energy, 1701 Hollis Street, Halifax, Nova Scotia B3J 2X1, Canada

DOI:

https://doi.org/10.4138/1673

Abstract

Coals, caimel coals and oil shales of the McLeod sequence from two boreholes in the Pictou Coalfield, Nova Scotia were analysed using methods of organic petrology and organic geochemistry. Petrographic composition was determined by maceral and microlithotype analyses. Within the McLeod coal seam, varying amounts of alginite, vitrinite, inertinite, and mineral matter indicate significant changes in the environment of deposition. High amounts of lamalginite and minerals, i.e., clay minerals and pyrite at the base and top of the seam indicate a lirnnic depositional environment, whereas much dryer conditions are indicated for the middle portion of the seam by better tissue preservation, typical for a wet forest type of swamp. This is confirmed also by results from microlithotype analyses. In the oil shales the predominant maceral is alginite. Coals, cannel coals and oil shales vary significantly in TOC values and hydrocarbon potentials. Parameters such as hydrogen and oxygen indices and hydrocarbon potentials are in good agreement with results from petrographic analyses. Methods of organic petrology and organic geochemistry define distinct types of organic matter in coals, cannel coals and oil shales which can be related to facies changes and environments of deposition. From the preliminary results it appears that these methods also can be applied regionally for stratigraphic correlations within sequences of rapid facies changes. RÉSUMÉ Des charbons, des charbons de spores et pollens, ainsi que des schistes bitumineux appartenant à la série de McLeod et provenant de deux sondages dans le bassin houiller de Pictou (Nouvelle-Écosse) furent analyses à l'aide de méthodes de pérologie et de géochimie organiques. On détermina la composition pétrographique grace à une analyse des macévaux et des microlithotypes. La variation des teneurs en alginite, vitrinite, inertinite et en composants min&aux au sein du filon charbormeux de McLeod témoigne de changements majeurs dans le milieu de dépôt. Un milieu de dépôt limnique est indiqué par des teneurs élevées en lamalginite et en minévaux, i.e. minéraux argileux et pyrite, tant à la base qu'au sommet du filon. En revanche, une meilleure conservation des tissus, typique des marécages de foret humide, trahit des conditions beaucoup plus seches pour la portion centrale du filon. Les resultats de analyses de microlithotype confirment cet état de chose. L'alginite est le macéral prédominant dans les schistes bitumineux. Les charbons, les charbons de spores et pollens, ainsi que les schistes bitumineux varient fortement aux plans du COT et du potentiel pétroligène. Certains paramétres, comme les indices d'hydrogene et d'oxygène et les potentiels pétroligènes, confortent les résultats obtenus grace aux analyses pétrographiques. Au sein des charbons, charbons de spores et pollens, et schistes bitumineux, les méthodes de la pétrologie et de la géochimie organiques détuiissent des types distincts de matiere organique qui peuvent être liés aux changements de faciès et aux milieux de dépôt. À partir de ces résultats préliminaires, il semble qu'on puisse utiliser ces méthodes à une échelle régionale pour nialiser des corrélations stratigraphiques à l’intérieur de séries montrant des changements rapides de faciès. [Traduit par le journal]

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Published

1989-04-01

How to Cite

Paul, J., Kalkreuth, W., Naylor, R., & Smith, W. (1989). Petrology, Rock-Eval and facies analyses of the McLeod coal seam and associated beds, Pictou Coalfield, Nova Scotia, Canada. Atlantic Geoscience, 25(1). https://doi.org/10.4138/1673

Issue

Vol. 25 No. 1 (1989)

Section

Articles

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