HR: 14:40h
AN: GP43C-05    [Abstracts]
TI: Paleomagnetic Paleolatitudes for Northeast Russia: an Update
AU: * Stone, D B
EM: dstone@gi.alaska.edu
AF: Geophysical Institute, University of Alaska 903 Koyukuk Dr., Fairbanks, AK 99775-7320 United States
AB: It is now generally accepted that Northeast Russia east of the Verkhoyansk fold and thrust belt is made up of multiple tectonic terranes. It also seems that these terranes can be divided into three main groups, the Kolyma-Omolon Superterrane (KOS) in the interior, the western extension of the Chukotka-Alaska Superterrane to the north and the "outboard" terranes to the south and east. The outboard terranes are separated from the other terrane groups by the Late Cretaceous Okhotsk-Chukotka volcanic belt. To date there are no reliable paleomagnetic data from within the Chukotka part of the northern superterrane, so reconstructions are based on models of the opening of the Arctic Ocean. The latest compilation of paleomagnetic data show large but systematic changes in paleolatitude with time for both the KOS and the outboard terranes. For the KOS, comparisons of the paleolatitudes with those for the Siberian craton shows that they could have been in their current relative positions in Devonian time, been displaced by as much as 40o southward by Permo-Triassic time, then moved rapidly northward during the Jurassic to regain their original relative latitude with respect to the craton. The record for the outboard terranes is much shorter, but supports the idea that they were carried by the plates of the Pacific and collided with the KOS in Cretaceous and later times. The paleomagnetic data from both the KOS and the outboard terranes hint at the possibility that there was a small southward paleolatitude change in Late Cretaceous-Early Tertiary time, perhaps indicating that the South Anuyi Ocean, which separated Chukotka from the KOS, closed before the Arctic ocean had finished opening.
DE: 9315 Arctic region
DE: 9320 Asia
DE: 8155 Plate motions--general
DE: 1525 Paleomagnetism applied to tectonics (regional, global)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting