Geotectonic setting of the Tertiary Uyandina and Indigirka-Zyryanka basins, Republic Sakha (Yakutia), Northeast Russia, using coal rank data

Abstract. Outcrops along the Inach River in the Uyandina basin and those along the Myatis' River in the Indigirka-Zyryanka basin were studied in detail and sampled for coal rank determinations. The Uyandina basin is an intramontane pull-apart basin characterized by extensional structures within the Moma rift system. The coal rank is below 0.3% vitrinite reflectance (R_r), which indicates shallow, immature conditions of basin formation and very low subsidence. The Myatis' River coal-bearing outcrops in the Indigirka-Zyryanka basin reveal compression induced by continent collision. The compressive deformation includes also lowermost Pliocene strata. Due to the position in the Verkhoyansk-Chersky fold belt adjacent to the Kolyma-Omolon microcontinent the Indigirka-Zyryanka basin has much in common with a foredeep, i.e. the asymmetry in thickness and tectonic structure. The vitrinite reflectance data (R_r) which range from 0.25% to more than 5% reinforce the accepted models that describe basin subsidence and geothermal history and the tectonic deformation.