190-2 Quantifying the Relationships Between Coal Thickness, Ash, Sulfur, and Sequence-stratigraphic Position: Pennsylvanian Breathitt Group, eastern Kentucky, USA

Session: Global Stratigraphy (Posters)

Presenting Author:

Authors:

Abstract:

A fundamental question in coal stratigraphy is the relationship between the thickness and properties of coal and its sequence-stratigraphic position. Several studies have predicted that the thickest coals should be associated with the beginning and end of transgression because these are times when accommodation is high and peat production can keep pace (Bohacs and Suter, 1997; Diessel, 2007). Similarly, the thickest coals in a depositional basin are expected to occur in mid-dip positions where subsidence rates are neither too high nor too low. Thick coals are also therefore more likely to be low-ash and low-sulfur, which is generally associated with dulling-up lithotypes. These relationships have been anecdotally reported from the Lower to Middle Pennsylvanian Breathitt Group of eastern Kentucky (Aitken and Flint, 1994, 1995; Jerrett et al., 2010, 2011; Eble et al., 1999), but here, we quantitatively evaluate them. To test these hypotheses, we measured coal thickness, its properties, and its sequence-stratigraphic context for 56 coals in the Pikeville Formation of the Breathitt Group in eastern Kentucky. Nine of these coals were sampled at ~10 cm spacing for ash and sulfur content. The data indicate that 83% of the coal beds are less than 40 cm thick; only three are thicker than 100 cm, with the thickest being 140 cm. Median coal thickness is lowest within the TST and HST, and it is greatest at the maximum regressive surface and immediately beneath incised valley fills. Thick coals (> 40 cm) occur primarily at the maximum regressive surface and immediately below incised valley fills, but only rarely within the TST. Laterally, the thickest coals occur in the depositionally updip and middip regions (i.e., towards the southeast), with only one of the downdip coals (i.e., towards the northwest) exceeding 40 cm. Our results support the hypothesized relationships that the thickest coals should be associated with the TST and mid-dip positions in the basin. Other depositional basins should be similarly evaluated to provide more quantitative tests of the expected variation in coal thickness and quality with sequence-stratigraphic and basin architecture.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9886

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