- Title
- Utility of coal petrology for sequence-stratigraphic analysis
- Creator
- Diessel, Claus F. K.
- Relation
- International Journal of Coal Geology Vol. 70, Issue 1-3, p. 3-34
- Publisher Link
- http://dx.doi.org/10.1016/j.coal.2006.01.008
- Publisher
- Elsevier
- Resource Type
- journal article
- Date
- 2007
- Description
- Sequence stratigraphy seeks to predict the depositional architecture of sediments based on the principle that their superposition and lateral arrangement are largely determined by the rate at which accommodation is made below depositional base level relative to the supply rate of sediments. Depositional base level is generally correlated with sea level which in paralic peat/coal deposits controls the position of the groundwater table above which oxidation, ablation and erosion would occur. The current Late Quaternary sequence is used to discuss some of the constraints on coal formation that stem from the interaction of short- and long-period modulations on sequence-forming eustatic cycles. The results show that the mid-transgressive systems tract is unlikely to produce significant coal deposits, which is supported by a survey of the relevant literature from eight different countries. It reveals a bimodal distribution of coal deposits with the strongest mode being situated in the early transgressive systems tract, while a broader, secondary mode occurs in the early and mid-highstand position. This concentration contrasts with the complete absence of any significant coal deposits in the early and mid-lowstand systems tract, and only a low occupancy of the late highstand systems tracts. The reasons for this distribution are briefly discussed, and attention is drawn to the possible over-stating of the coal-forming potential of the late lowstand systems tract. Following a brief discussion of the sequence-stratigraphic interpretation of coal measures, emphasis is put on the application of sequence stratigraphy to the study of coal seams and their composition at various levels of petrographic detail. While in low-rank coals, botanical affinities contribute much to the lithotype-based analysis, a genetic assessment of bituminous coal seams relies primarily on physical and chemical palaeo-environmental signatures. Simple properties, such as maximum coal thickness, low detrital mineral content and maximum preservation of vitrinite, particularly of telovitrinite, define a good balance between the former rates of accommodation versus peat accumulation. Iso-metamorphic variations in telovitrinite reflectance and its dispersion measured by the coefficient of variation have also contributed to the palaeo-environmental interpretation. This paper confirms the identification within coal seams of most of the sequence-stratigraphically significant surfaces, e.g. sequence and parasequence boundaries, transgressive, flooding, and maximum flooding surfaces. It also gives examples of some new ones, referred to as accommodation reversal, non-marine flooding, give-up transgressive, terrestrialisation, and paludification surfaces. Some of these are specific to coal measures, but the give-up transgressive and accommodation reversal surfaces may have wider significance.
- Subject
- coal seams and coal measures; onshore sequence stratigraphy; significant surfaces; accommodation/peat accumulation ratio; coal-forming potential of systems tracts
- Identifier
- http://hdl.handle.net/1959.13/34032
- Identifier
- uon:3489
- Identifier
- ISSN:0166-5162
- Language
- eng
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