The Spitsbergen archipelago is at the junction of the northern segment of the Norwegian-Greenland Basin and the western part of the Arctic Ocean, which makes it a key area for deciphering the formation history and geological structure of the region. Crystalline basement rocks and sedimentary cover units outcrop here, including those that constitute the petroleum-bearing complexes of the shelf. There is a clear need to substantiate the presence of evidence for the Baikalian (Timanian) tectono-magmatic activation within the Earth’s crust of the Spitsbergen archipelago, as well as to determine the conditions of its manifestation. To address this objective, a comprehensive description of the Trollheimen volcanogenic formation – whose rocks are known within Oscar II Land – is provided for the first time, based on the authors’ own data. We examine geotectonic features, material composition, age, and geodynamic interpretations of the formation settings. The authors identified that the sedimentary-volcanogenic complex described in the mountainous glacial part of Oscar II Land was formed during the Vendian (574-558 Ma) as a result of tectono-magmatic activation of the epi-Grenvillian paraplatform. They provide the petrographic and petro‑geochemical profile of the identified metabasalts, metaandesites, and metatuffs. The results of studying the petrochemical features of the Trollheimen volcanogenic formation indicate magma generation at great depths; the rift-related nature of these formations is determined. The authors carry out a correlation with the previously identified sedimentary-volcanogenic complex of the Chamberlaindalen Series in the northern part of Wedel Jarlsberg Land. The presented data confirm the previously proposed arguments for the Vendian-Baikalian, Timanian intraplate activation in the archipelago, as well as the widespread development of these complexes within the cover of the epi-Grenvillian paraplatform of Spitsbergen.