Recognition of peat depositional environments in coal: A review

Shifeng Dai, Achim Bechtel, Cortland F. Eble, Romeo M. Flores, David French, Ian T. Graham, Madison M. Hood, James C. Hower, Vera A. Korasidis, Tim A. Moore, Wilhelm Püttmann, Qiang Wei, Lei Zhao, Jennifer M.K. O'Keefe

Research output: Contribution to journalReview articlepeer-review

253 Scopus citations

Abstract

Peat depositional environments, the sites where and conditions under which peat accumulates, significantly influence a resultant coal's physical properties, chemical composition, and coal utilization behavior. Recognition of peat depositional environments for coal is a challenging endeavor because coal's observed compositional properties not only result from a variety of geological processes operating during peat accumulation, but also reflect the influence of adjoining or external depositional sedimentary environments and alteration during later diagenesis and/or epigenesis. The maceral or microlithotype composition of any one layer of peat can be the product of years or decades of plant growth, death, decay, and post-burial infiltration by roots in addition to the symbiotic, mutualistic, parasitic, and saprophytic relationships with non-plant biota, such as arthropods, fungi, and bacteria. The overprint of increasing thermal maturation and fluid migration through time on the resulting coal can make these relationships difficult to recognize. Therefore, published models based on maceral composition alone must be used with great caution. Lipid compositions, even from lipid-poor low-rank coals, can provide important information about depositional environments and paleoclimate, especially if combined with the results of organic petrography and paleontological studies. Just as sulfur derived from seawater provides environmental clues, the ratios of two particularly relevant trace elements rather than a single trace element can be used to interpret peat depositional environments. Epigenetic minerals, as well as their corresponding chemical compositions should not be used for such a purpose; similarly, resistant terrigenous minerals deposited during peat accumulation in many cases should be used with considerable caution. The interactions of the biota present in the peat-forming ecosystem, often determined using palynological and geochemical proxies, and their interpretation in the context of geography and paleoclimate are important means for deciphering peat depositional environments. Overall, a combination of evidence from geochemistry, mineralogy, palynology, and petrology of coal and from stratigraphy, sedimentology, and sedimentary facies of related rocks is necessary for accurate and comprehensive determination of depositional environments. The need for interdisciplinary studies is underscored by peat compositional properties, which have been greatly affected by various processes during the syngenetic, diagenetic or epigenetic stages of coal formation.

Original languageEnglish
Article number103383
JournalInternational Journal of Coal Geology
Volume219
DOIs
StatePublished - Feb 15 2020

Bibliographical note

Funding Information:
This research was supported by the National Natural Science Foundation of China (nos. 91962220 and U1810202) and the 111 Project (no. B17042). This paper is dedicated to the memory of Prof. Colin R. Ward. The authors are grateful to Mrs. Yongjie Hou, Pan Yang, Ning Wang, and Shaobo Di for their work on polishing some figures presented in this paper. We thank Anne Raymond and Bill DiMichele for discussions of Paleozoic plant ecology and taphonomy. We thank our reviewers and editor Ralf Littke for their patience and diligence in taking on the task of handling such a large and expansive manuscript.

Funding Information:
This research was supported by the National Natural Science Foundation of China (nos. 91962220 and U1810202 ) and the 111 Project (no. B17042 ). This paper is dedicated to the memory of Prof. Colin R. Ward. The authors are grateful to Mrs. Yongjie Hou, Pan Yang, Ning Wang, and Shaobo Di for their work on polishing some figures presented in this paper. We thank Anne Raymond and Bill DiMichele for discussions of Paleozoic plant ecology and taphonomy. We thank our reviewers and editor Ralf Littke for their patience and diligence in taking on the task of handling such a large and expansive manuscript.

Publisher Copyright:
© 2020 The Authors

Keywords

  • Coal facies
  • Indicative elements
  • Lipid composition
  • Macerals
  • Minerals
  • Palynological compositions
  • Peat depositional environments
  • Sedimentary depositional systems

ASJC Scopus subject areas

  • Fuel Technology
  • Geology
  • Economic Geology
  • Stratigraphy

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