Abstract—: The results of petrographic, geochemical, and isotopic studies of the Neoproterozoic and Upper Paleozoic sandstones of the Eastern Taimyr complement the available data on their genesis and confirm their molassic origin. The sandstones and mudstones of the Neoproterozoic Stanovaya and Posadochnaya formations formed mostly from the erosion products of the magmatic and metamorphic complexes with ages of ~970–800 Ma and from older siliciclastic rocks. The Upper Paleozoic sandstones of the Byrranga, Sokolinaya, and Turuza formations are characterized by a somewhat lower degree of maturity. Most of them formed from erosion products of magmatic and metamorphic complexes with ages of ~500 and ~300 Ma, although sediments sourced from an older provenance were also encountered. The ages of the youngest detrital zircon grains from the Upper Paleozoic sandstones are close to the depositional ages in some cases and differ by more than 100 m.y. in other cases. This suggests that one should be cautious about using the maximum depositional ages for establishing the tectonic setting of sedimentary basin formation.