THERMAL ALTERATION OF JURASSIC VOLGA PLANT MICROFOSSILS OF WESTERN SIBERIA

Core samples from the Jurassic deposits of well sections of Chuel'skaya, Salymskaya, Ombinskaya, Priobskaya,Varioganskaya and other areas were studied. It was revealed that spores of Lycopodium sp., Coniopteris spp. and Gleicheniiditessp. are rare in plant microfossils assemblages; those of Klukiasporites sp. are extremely rare. The following representatives ofpollen were recorded: Pinus exilioides Bolch., P. divulgata Bolch., Sciadopitys sp. and Classopollis sp. Among spores, pollengrains, and microphytoplanktons, the latter dominates. Thus, Crassisphaera sp., Tasmanites sp., Pterospermopsis eurypterisCookson et Eisenack, P. harti Sarjeant and Cymatiospaera sp. are abundant; Pareodinia sp. and Trichodinium sp. sometimesoccur. Although the taxa of pollen, spores as well as microphytoplanktons vary quantitatively in the present assemblages,general composition of these assemblages is constant for different areas of Western Siberia. The colour of plant microfossils,indicating the level of thermal maturation of the sedimentary organic matter, can be different. Accordingly, plant microfossils(in particular very abundant in these deposits microphytoplanktons) can be used for testing catagenesis of the organic matter.

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Clc Number:

Q913.84