Characteristics of lithotype thickness and sequential association of some Kentucky coals

Abstract

Twenty-two Pennsylvanian coal beds from 199 sites in the Eastern and Western Kentucky coal fields were described in terms of lithotypes, i.e. vitrain, bright clarain, clarain, dull clarain, durain, and fusain as well as mineral matter. The characteristics of the coals were analyzed through comparisons of thickness distributions of each lithotype as well as location in the Eastern and Western Kentucky coal fields. The thickness of each lithotype appeared to show normal distribution using the phi scale. Bright clarain and clarain showed a mode at — 6 phi (64 mm), while vitrain and fusain are much thinner, showing modes at — 2 phi (4 mm). The lithotype thickness distribution of all coal seams depended mainly on the relative abundance of bright clarain and clarain vs vitrain and fusain. Western Kentucky coals contain relatively more vitrain and fusain layers and less durain and dull clarain than do eastern Kentucky coals, suggesting different depositional settings for western and eastern Kentucky. Sequential analysis of lithotypes demonstrated that different lithotypes were not randomly associated in sequence. Overall, bright clarain and clarain showed close associations with fusain, while mineral matter and fusain showed negative association. This suggests that bright lithotypes with well-preserved plant tissue were formed in peat-forming paleomires which were periodically subjected to intense oxidation. Eastern Kentucky coals show a negative association between durain and fusain, indicating that the durain was formed in open water mires with little opportunity for intense oxidation. A close association between bright clarain and pyrite and negative association between fusain and pyrite in western Kentucky coals suggest a setting with only moderate acidity and a tendency toward oxidation.