Comparing maceral ratios from tropical peatlands with assumptions from coal studies: do classic coal petrographic interpretation methods have to be discarded? Raphael A.J. Wu ¨st * , Michelle I. Hawke, R. Marc Bustin Department of Earth and Ocean Sciences, Tropical Peat Research Group, University of British Columbia, 6339 Stores Road, Vancouver, B.C., Canada, V6T 1Z4 Received 12 December 2000; accepted 7 August 2001 Abstract Petrographic investigations of tropical peat deposits from the Tasek Bera Basin, Malaysia, show that petrographic methods can contribute valuable information about paleoecological settings of mire deposits. Comparing modern peat-forming environments and the pre-maceral composition of peat samples allows the reconstruction of paleoecological conditions, such as floral composition, fires, microbial activity, etc., and gives insight into paleodepositional environments. In the past, maceral ratios of coals have been used to interpret paleodepositional settings of coal deposits. Such a procedure assumes that coal texture and coal maceral composition are dictated solely by the depositional environment, and thus different depositional environments should be clearly discriminated based on maceral ratios. In the modern peat deposits of Tasek Bera, divergent petrographic results occur in similar depositional environments, hence, poor correlation occurs between the petrography, the degree of decomposition, and the depositional environment. Furthermore, from the time of peat deposition, peat is subject to considerable alteration. During subsequent diagenesis, preservation of structured and strongly altered material, such as inertinite, gelified material or funginite, is favoured and results in biased coal maceral compositions. Because maceral indexes in modern peat studies are of little utility in the reconstruction of paleoenvironmental settings, it follows that coal maceral indexes should not be utilized in the future to interpret paleodepositional environments of coals. D 2001 Elsevier Science B.V. All rights reserved. Keywords: Tropical peat; Petrography; Macerals; Depositional environment; TPI; Coal analogue; Malaysia 1. Introduction Depositional environments play a major role in determining the composition and preservation of peat and coals. The geology, climate, vegetation, and the hydrological regime (e.g. level and flow of ground- water) of the peat deposits influence the distribution and quality of coal. Coal maceral compositions, de- termined through petrographic analyses, are used to determine the paleoenvironment and contribute to the understanding of composition, compaction and degree of preservation of plant material. Macerals are frequently considered to be plant- and/or envi- ronment-specific, and so the assessment of vegeta- 0166-5162/01/$ - see front matter D 2001 Elsevier Science B.V. All rights reserved. PII:S0166-5162(01)00050-7 * Corresponding author. Tel.: +1-604-822-2449; fax: +1-604- 822-6088. E-mail addresses: rwuest@interchange.ubc.ca (R.A.J. Wu ¨st), ess-cal-mhawke@NRCan.gc.ca (M.I. Hawke), bustin@interchange.ubc.ca (R. Marc Bustin). www.elsevier.com/locate/ijcoalgeo International Journal of Coal Geology 48 (2001) 115 – 132