Paleomagnetic Constraints on the Geographic Framework for the Origins of the Amerasian Basin
David B. Stone1, Pavel Minyuk2, and Evgenie Kolosev2
1Geophys. Inst., Univ. of Alaska, Fairbanks, AK.
2NEISRI, RAS Far East Div., Magadan, Russian Federation.
Recent improvements in the global Apparent Polar Wander (APW) paths have allowed better geographic reconstructions to be made showing the locations of the major continents surrounding the Arctic Ocean and their positions with respect to the geomagnetic pole. This allows the expected paleolatitude of specific locations to be determined. It should be noted that many published reconstructions are based on the Hot Spot reference frame and give very different paleolatitudes than are seen using the paleomagnetic poles for the frame of reference.
Conventional wisdom says the Amerasian Basin developed sometime during Late Jurassic to Late Paleocene time (about 150 to 60 Ma). During this time the major blocks forming the Arctic margin, consisting of Eurasia, North America and Greenland, remained essentially fixed with respect to each other. The effect of the opening of the Atlantic at about 70Ma and the initiation of the opening of the Eurasian basin at about 50Ma have very little effect on the geography of the region over the time of basin formation. The time of opening is also the time of the Cretaceous still-stand of the geomagnetic field (50Ma to 130Ma) when the circles of confidence of the poles overlap and the pole is located just offshore of NW Alaska. This means that any changes in paleolatitude for sites within the Arctic region imply relative motion with respect to the surrounding continental blocks.
Most models call for Arctic Alaska (defined as extending from Bering Straight to the Mackenzie River delta and from the south flank of the Brooks Range northwards) and Arctic Chukotka (defined as those parts north of the South Anuyi Suture including the East Siberian Sea continental shelf) to be a single package that originates in the Arctic Ocean region. The limited paleomagnetic data available from all of Arctic Alaska-Chukotka require an initial location near the Lomonosov Ridge - Ellesmere Island junction. Their postulated track heads towards the geomagnetic pole, with the Bering Straight crossing the pole at about 100Ma.
The backstop for the migrating Arctic Alaska-Chukotka terrane is made up of terranes which have migrated north from the Pacific and along the margin of North America. Data for this northward migration is more plentiful and give realistic, but complex models for the backstop paleogeography.
AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.���������������������������������������������������������������������������������������������������