New insights into Arctic paleogeography and tectonics from U-Pb detrital zircon geochronology

[ 1] To test existing models for the formation of the Amerasian Basin, detrital zircon suites from 12 samples of Triassic sandstone from the circum-Arctic region were dated by laser ablation-inductively coupled plasma-mass spectrometry (ICP-MS). The northern Verkhoyansk ( NE Russia) has Permo-Carboniferous ( 265 - 320 Ma) and Cambro-Silurian ( 410 - 505 Ma) zircon populations derived via river systems from the active Baikal Mountain region along the southern Siberian craton. Chukotka, Wrangel Island ( Russia), and the Lisburne Hills ( western Alaska) also have Permo-Carboniferous ( 280 - 330 Ma) and late Precambrian-Silurian ( 420 - 580 Ma) zircons in addition to Permo-Triassic ( 235 - 265 Ma), Devonian ( 340 - 390 Ma), and late Precambrian ( 1000 - 1300 Ma) zircons. These ages suggest at least partial derivation from the Taimyr, Siberian Trap, and/ or east Urals regions of Arctic Russia. The northerly derived Ivishak Formation (Sadlerochit Mountains, Alaska) and Pat Bay Formation ( Sverdrup Basin, Canada) are dominated by Cambrian - latest Precambrian ( 500 - 600 Ma) and 445 - 490 Ma zircons. Permo-Carboniferous and Permo-Triassic zircons are absent. The Bjorne Formation ( Sverdrup Basin), derived from the south, differs from other samples studied with mostly 1130 - 1240 Ma and older Precambrian zircons in addition to 430 - 470 Ma zircons. The most popular plate tectonic model for the origin of the Amerasian Basin involves counterclockwise rotation of the Arctic Alaska Chukotka microplate away from the Canadian Arctic margin. The detrital zircon data suggest that the Chukotka part of the microplate originated closer to the Taimyr and Verkhoyansk, east of the Polar Urals of Russia, and not from the Canadian Arctic.