PLATE KINEMATIC EVOLUTION OF THE PRESENT ARCTIC REGION SINCE THE ORDOVICIAN

Abstract

The Laurentian, Baltic, and Siberian blocks of the modern circum-Arctic were scattered across a broad area between 10°S and 30°N during the Late Ordovician. Closure of the Iapetus Ocean during the Ordovician and Early Silurian brought Baltica and the Chukotka block in contact with Laurentia, simultaneously producing the Scandian phase of the Caledonian orogeny and creating the supercontinent of Laurussia. The assembly of Laurussia brought the cores of most of the scattered circum-Arctic landmasses into roughly their present-day relative positions. This collisional event also attached Pearya to northern Ellesmere Island, transpressionally sutured Chukotka to the general region of the present-day Canadian Arctic Islands, and attached the Seward Peninsula to Laurentia. Devonian rifting, perhaps driven by a mantle plume, formed the Vilyui basin of eastern Siberia, opened the Oimyakon oceanic basin offshore, and rotated the Siberian block away from North America and toward Baltica. The major continental blocks that encircle the modern Arctic Ocean have migrated generally northward since the Carboniferous, although some, such as Siberia, have passed over the pole and are now moving southward. During the Jurassic and into the Early Cretaceous, the Chukotka-Barents shelf region passed over a nearly fixed Siberian Traps-Iceland hotspot. Opening of the Amerasia basin of the Arctic Ocean by seafloor spreading may have been initiated as seafloor spreading associated with continued subduction along the northeastern Pacific Rim, but additional stress produced by a hotspot converted what might have been originally orthogonal opening to rotational opening. Volcanism at the margins of the opposing plates of the newly forming Amerasia basin over the site of the fixed Siberian Traps-Iceland hotspot is thought to have created the major high-standing Alpha and Mendeleev submarine ridge system of the northern Amerasia basin. Beginning in the late Paleocene, North Atlantic seafloor spreading split Greenland and the Lomonosov Ridge from Eurasia, creating the Eurasia basin of the Arctic Ocean by slow spreading along the Nansen-Gakkel Ridge that continues to the present day, and produced transtension through parts of far-eastern Siberia.