HR: 1340h
AN: T13D-1569    [Abstracts]
TI: Paleomagnetic Data From Alaska and Northeast Russia: Their Role in modeling the Opening of the Arctic Ocean.
AU: * Stone, D B
EM: dstone@gi.alaska.edu
AF: Geophysical Institute, UAF, 903 Koyukuk Dr., Fairbanks, AK 99775, United States
AB: The mode of origin of the Arctic Ocean has long been the focus of considerable debate. The conventional model involving a counterclockwise rotation of the Arctic Alaska terrane away from the Canadian Arctic Islands should have been an easy problem for a paleomagnetic answer. In practice almost all paleomagnetic studies in the region show a pervasive near-vertical magnetic overprint. Only two reliable studies exist for Arctic Alaska, one is from borehole core samples from the Early Cretaceous Kuparuk River Formation, and the other is from the late- Early Cretaceous Nanushuk Formation. The Kuparuk paleomagnetic pole is well constrained in time, has a good reversal stratigraphy indicating a primary magnetization and because it is part of a major oilfield is well understood in terms of its geological setting. The Nanushuk data pass a fold test, but are in the long Cretaceous normal chron, so no reversal test is possible. The Kuparuk data, when looked at in the light of recent apparent polar wander paths for North America, do not support the conventional rotation model. The Nanushuk data show that Arctic Alaska was in place with respect to North America at the time the rocks were magnetized. The Kuparuk paleomagnetic pole is permissive for many other models, including a rotation from an initial position nearer to Greenland or locations adjacent to Siberia. Attempts to constrain these possibilities are being made by comparing the Alaskan data with that from Siberia. Only two data points are available from the Chukotka block, and both of these are from the Okhotsk-Chukotka volcanic belt of latest Early Cretaceous age and give paleomagnetic poles close to those expected for the block being in-place with respect to present geography. Using data from the Kolyma-Omolon Superterrane, currently adjacent to the Chukotka block allows more constraints on the possible relative locations of the major blocks involved in the opening of the Arctic Ocean. These and other constraints result in an ever-evolving set of cartoons of possible paleogeographies.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 9315 Arctic region (0718, 4207)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting