Jurassic continental deposits in the sections of the Irkutsk Coal Basin stratoregion

Age of the coal accumulation in the Irkutsk basin based on accessory zircon dating in the Azeisk deposit tonstein (LA-ICP-MS)

“…However, this contradicts to U-Pb dating of tonstein provided in this study. It should be noted that the stratigraphy of the Jurassic age of the Irkutsk basin is mainly based on palynological data (Saks et al, 1981;Skoblo et al, 2001), and the recent papers (Akulov et al, 2015;Kirichkova et al, 2016;Kiritchkova et al, 2017) are the result of phytostratigraphic research. Thus, palynological data provide more robust constraints on the age of the Jurassic continental deposits, at least, for the Irkutsk basin.…”

“…The age of the Irkutsk basin sediments was determined by the biostratigraphic method, which gives a rather wide time interval. At that, while the lower limit of the sedimentation onset is determined in the Pliensbachian age (Akulov et al, 2015;Kiritchkova et al, 2017;Saks et al, 1981;Skoblo et al, 2001), the upper one remains drifting from the Aalenian to the Bajocian age (Akulov et al, 2015;Kirichkova et al, 2016;Saks et al, 1981;Skoblo et al, 2001). The age of the sediments was determined mainly by plant residues Mashchuk, 2018, 2014;Kirichkova and Travina, 2000); fauna findings are rare and are mainly related to the lower sub-formation of the Prisayan Fm.…”

“…Despite the large number of publications devoted to studies of the Irkutsk basin (Adamenko et al, 1971;Akulov et al, 2015;Feinstein, 1971;Kiritchkova et al, 2017;Odintsov, 1967;Skoblo et al, 2001;Timofeev, 1970), questions related to the age and position of the stratigraphic units still remain undetermined (Fig. 2).…”

Geochemistry of the Cheremkhovo and Lower Prisayan Formations from the Jurassic Irkutsk Coal-Bearing Basin: Evidence for Provenance and Climate Change in Pliensbachian–Toarcian

“…Based on biostratigraphy, different scholars attribute the Cheremkhovo Fm. to the Pliensbachian [3], Pliensbachian-Toarcian [2][3][4] or Pliensbachian-Aalenian [5] intervals. The only radioisotopic date (187.44 +0.45/−1.60 Ma, Pliensbachian) was obtained by the U-Pb method using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) on zircon of a tonstein (altered volcanic ash) layer from an industrial coal seam of the Azeysk deposit [6].…”

“…Despite the large number of publications devoted to studies of the Irkutsk coal-bearing basin [3][4][5][7][8][9][10][11], there are too few modern analytical data for this area. In recent years, the study of the Irkutsk coal-bearing basin was focused on stratigraphy, structural evolution, and sedimentology [5,[11][12][13][14][15][16]. Geochemical data were only obtained for coals of the Azeisk coal deposit [17] and the uppermost Prisayan Fm.…”