THE ROLE OF PALYNOLOGY IN PALEOECOLOGICAL ANALYSES OF TERTIARY COALS

Pollen, spores, and other plant microfossils are important constituent s of Tertiary coals, both as petrographic components (the maceral spor inite) and as distinctive indicators of the nature of the depositional environment in which the coal-forming Feat accumulated. Palynological analyses, which have been conducted on Tertiary coals since the 1930' s, play an increasingly important role in modem paleoecological analys es of coals. Among the most important factors controlling the petrogra phic composition and facies characteristics of coal deposits are the t ypes and relative abundances of plants that composed the peat. At pres ent, wetland environments in which peat accumulates (mires) range from marshes and bogs to forested swamps; each is inhabited by distinctive plant communities. These plant communities are associated with varied conditions of climate, water depth, chemistry, and nutrient supply, a nd the floras can be indicative of these conditions. In the Tertiary P eriod, plant communities of mires were also highly diverse and special ized (especially as compared with those of the Carboniferous). The dom inant species in some Paleocene mire floras were gymnosperms, but cont inuing a trend begun in Late Cretaceous time, angiosperms became incre asingly prominent through the Tertiary. The diverse angiosperm-dominat ed mire floras produced coals that vary significantly in facies and he nce in quality. Such contrasts are evident in contemporaneous coals fr om different paleolatitudes, as well as among coals of different ages within the Tertiary, as exemplified by selected deposits in the wester n United States. The palynofloras of these coals reflect the floristic composition of the plant communities of the ancient mires.