PHYTOSTRATIGRAPHY OF JURASSIC COAL-BEARING FORMATIONS OF THE IRKUTSK BASIN

Abstract

The Jurassic stratotype and reference sections in the Irkutsk basin located along the Angara River and its tributaries are studied along with remains of fossil plants sampled in the bed-by-bed manner. Paleobotanical data are used to subdivide Jurassic sections into the phytostratigraphic units (beds with flora) and to substantiate their lateral correlation. Isolated sections are correlated between each other and their succession in the Jurassic sequence is defined. Based on the paleobotanical data, sedimentary formations of the Jurassic basin are correlated with the coeval deposits of southern West and Central Siberia. The age of the Cheremkhovo Formation, except for its upper member, is arbitrarily estimated to be of the terminal Early Jurassic (Toarcian) age, whereas the upper silty-sandy member is dated back to the initial Middle Jurassic, and the Prisayanskaya Formation is correlated with the Bajocian.