Baltica data makes it difficult to locate the margin in the Arctic. Ordovician faunas indicate that most of Svalbard, including Bjørnøya, was part of Laurentia, but Franz Josef Land and Kvitøya (an eastern island of the Svalbard archipelago) most likely became part of Baltica in the Timanide Orogeny. The Taymyr Peninsula, in contrast, never was part of Baltica: southern Taymyr was part of Siberia whilst northern Taymyr and the Severnaya Zemlya archipelago were part of the independent Kara Terrane in the early Palaeozoic. The eastern margin, the Uralide orogen, extends from the Arctic Novaya Zemlya archipelago to the Aral Sea. The
Novaya Zemlya are still used for airfields today. The Soviet Air Force maintained a presence at Rogachevo on the southern part of the southern island, on the westernmost peninsula (). It was used primarily for interceptor aircraft operations, but also provided logistical support for the nearby nuclear test area. Novaya Zemlya was the site of one of the two major nuclear test sites managed by the USSR, used for air drops and underground testing of the largest of Soviet nuclear bombs, in particular the October 30, 1961 air burst explosion of Tsar Bomba, the largest, most powerful nuclear weapon ever detonated. The