ABSTRACT

Reflectances were measured on a variety of macerals in 23 coals from two sections of the Jurassic- Cretaceous Kootenay Group in southeastern British Columbia. The study had two objectives: A. to examine reflectance differences between macerals, especially those of the inertinite group, and to determine the reflectance thresholds separating these macerals; B. to study reflectance variations of the non-vitrinite macerals with depth and to compare these with vitrinite. These results were obtained; 1. mean random reflectances on vitrinite A ranged from 0.96 to 1.41 in the 12 seams at Weary Ridge, and from 0.91 to 1.38 for the seams of the Sparwood section. The corresponding range for low- reflecting semifusinite at Weary Ridge was 1.15 to 1.70; for high-reflecting semifusinite 1.44 to 1.94; and for fusinite 1.88 to 2.63. At Sparwood Ridge corresponding ranges are: low-reflecting semifusinite, 1.15 to 1.67; high-reflecting semifusinite, 1.46 to 1.89; and fusinite 2.06 to 2.43. Liptinite reflectances, which could only be determined on some seams, ranged from 0.36 to 1.11. 2. vitrinite reflectance increases with depth, although there is a marked decrease in gradient (Ro change/lOOm) toward the base of both sections. Plots of semifusinite and fusinite reflectances with depth show similar characteristics. The decrease in gradient toward the base of the sections possibly is due to high sandstone content in this part of the section, since thermal conductivity is affected by changes in lithology. 3. the overlap between the two varieties of semifusinite is much greater than between low-reflecting semifusinite and vitrinite on one hand and high-reflecting semifusinite and fusinite on the other. This suggests that designation of low- and high-reflecting semifusinite is only partially successful in subdividing what appears to be a continuous population. 4. only a few measurements on fusinite showed reflectance values higher than 4.00. This suggests that there is very little pyrofusinite in the Kootenay coals. Comparison with published data on coals from other parts of the world indicates that much of the Kootenay fusinite would be classified as semi- fusinite by other workers.