ASPECTS OF PETROGRAPHY, PAL YNOLOGY AND INORGANIC CONSTITUENTS OF SUBBITUMINOUS COALS FROM CANYON CREEK, ALASKA: A HIGH LATITUDE TERTIARY COAL FIELD Public

Special Research Report SR-121 Samples representing eight Tertiary subbituminous coal seams from Canyon Creek, Alaska were analyzed in order to characterize their maceral, inorganic and palynological content. Comparisons of the maceral and inorganic composition were made with similar age and rank coals of the conterminous United States. In addition, the applicability of the low rank coal classification to the description of the higher rank, low rank coals of Canyon Creek was examined. The sampling area is located 70 miles northwest of Anchorage along the southern margin of the Yentna Coal Field. The small (2 X 10 mile) coal deposit is preserved in a structural graben; Tyonek Formation sediments rest unconformably on early Tertiary granitic rocks and Jura-Cretaceous metasedimentary marine rocks. The inferred depositional environment is nonmarine; low sulfur levels are consistent with the inferred environment. The presence of exotic broad-leaved deciduous pollen (Quercus, Fagus, Tilia, Juglans, Pterocarya, Ulmus, Carya) indicates that the coal-bearing sediments are referable to the Upper Seldovian paleobotanical stage, which spans the late Early to early Middle Miocene. Palynological analyses indicate that both angiosperms and conifers were present in the original wetland communities. Alnus, Betula, Taxodiaceae-Cupressaceae-Taxaceae pollen and Pinus-type were the major palynomorphs. Several types of plant communities may have been present, including: Glyptostrobus CTaxodium-type) tree swamps (with a large dicotyledonous input); shrubby, streamside plant communities with alder and willow; and Sphagnum-wetlands containing birch, alder and ericaceous shrubs.

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