Abstract— <p>This paper presents new geological, geochemical, and geochronological data for the Late Neoproterozoic volcanic sequence in the northwestern Taimyr Peninsula, whose geodynamic setting has been controversial. The sequence comprises high-K rocks ranging from tephrites to rhyolites, with geochemical signatures typical of both suprasubduction and intraplate settings. Felsic rocks, mainly tuffs, predominate in the section, which is more than 700 m thick. By analogy with similar complexes in the Andes, we conclude that the studied sequence formed in the rear of an active continental margin between 683 and 658 Ma, or possibly longer. An episode of extension likely occurred around 660 Ma. We suggest the discussing margin belonged to the Siberian paleocontinent.</p>