PALEOMAGNETISM, PALEOLATITUDES AND RECONSTRUCTIONS OF NORTHEAST RUSSIA AND ALASKA

STONE, David B., Geophysical Institute, University of Alaska, 903 Koyukuk Drive, P.O.Box 757320, Fairbanks, AK 99775, [email protected]

The general consensus is that what is now the Chukotka-Alaska composite terrane migrated across the Arctic Ocean, closing the South Anuyi and Angayucham oceanic basins to join the terranes of Northeast Russia and Alaska. It is also well established that the major terranes of interior Northeast Russia, notably the Omulevka and Omolon terranes, migrated from southerly latitudes to roughly their present latitudes in mid-Mesozoic time. On the Alaskan side, the travel histories of the terranes making up interior Alaska (north of the very mobile southern terranes and south of the Arctic Alaska terrane) is not well known, however they too appear to have been roughly in place by mid-Mesozoic time. There is very little reliable paleomagnetic data for the Chukotka-Arctic Alaska composite terrane. However there are paleomagnetic data for the combined terranes of interior NE Russia and Alaska. The available paleomagnetic data for late Cretaceous – Early Tertiary time suggest that they may have been displaced to the north of their present locations when the Chukotka-Alaska terrane arrived, thus requiring the Arctic Ocean to continue opening after the South Anuyi and Angayucham sutures formed. Most of the data supporting this northward displacement come from volcanic rocks associated with the Okhotsk-Chukotka Volcanic Belt (OCVB) which overlaps many of the interior terranes. Comparing the paleomagnetic results from these rocks with the latest Apparent Polar Wander (APW) path for North America and that for Northeast Russia (derived from the Eurasian APW path) it seems that the OCVB was more closely connected to the North America than Siberia in addition to being a little north of its present position with respect to either of these continental blocks.