Geological structure of quaternary deposits of the right-hand bank of the Big Ob river (north of Western Siberia)

The main stages of the formation of the quaternary deposits at the right-hand bank of the Big Ob are characterized. For the first time, the Pitl’ar alluvium comparable with MIS-7 (II3) was separated into a stratotype. The Pitl’ar alluvium is widely distributed as megaclastes in the Khashgort glaciocomplex. Based on the reference sections, it was demonstrated that the local alluvial sands were deposited at a similar hypsometric level as a result of lateral erosion and accumulation. We recorded intensive changes in height of the lower contacts of fluvioglacial deposits formed at the stages of the descent of the sub-glacial lakes namely at the Tazovsky stage (II4), matched to MIS-6, and the Early Zyryanovsk stage (III2), matched to MIS-5b, d. These two events intensively dissected vast territories at the deglaciation stages that led to the formation of a complex picture of the geological structure of the local quaternary strata. A scheme of relationships of quaternary sediments for the right-hand bank of the Big Ob is constructed.