Variation of petrological and geochemical compositions in a sequence of humic coals, cannel coals, and oil shales

Coals, cannel coals, and oil shales of the McLeod sequence from two boreholes in the Pictou Coalfield, Nova Scotia, Canada, were analyzed by use of microscopical and organic geochemical methods. Changes in the environment during deposition of the organic-rich rocks are reflected in varying proportions of vitrinite, liptinite, and inertinite macerals and mineral matter. In parts of the sequence, a decrease of telalginite (mainly composed of Botryococcus algae) is associated with an increase of bituminite/lamalginite. The composition of the extractable organic matter shows that parameters such as the pristane/phytane ratio, the pristane/n-C 17 ratio, and the methylphenanthrene ratio (MPR) provide higher values exclusively in extracts from the humic coal-bearing horizon