Contributions to the Geology of the Bering Sea Basin and Adjacent Regions
Paleomagnetic Studies and Tectonics in the Aleutian Islands
Published:January 01, 1975
D. B. STONE, 1975. "Paleomagnetic Studies and Tectonics in the Aleutian Islands", Contributions to the Geology of the Bering Sea Basin and Adjacent Regions, R. B. Forbes
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Paleomagnetic vector directions were obtained for rocks collected in the Near Islands, the Andreanof Islands, and the Fox Islands. Potassium-argon dating indicates that the oldest of the extrusive rocks associated with the latest phase of volcanism in the Andreanof Islands are less than 0.5 m.y. old, and those in the Fox Islands about 2 m.y. old. The paleomagnetic directions for Miocene and younger rocks generally coincide with the field expected for an axial dipole, implying that no significant tectonic movement has taken place since the rocks were formed. This is in contrast to the generally steeply dipping Eocene rocks. On Adak Island the paleomagnetic vector directions obtained from a 4.9-m.y.-old intrusive complex and a sequence of Eocene sedimentary rocks indicate that the tilting of the sedimentary sequence was a simple rotation and was completed earlier than 4.9 m.y. ago. Similarily, the paleomagnetic data obtained on Shemya Island show that the steeply dipping Eocene(?) sedimentary rocks were tilted to nearly their present attitude before the emplacement of the late Miocene intrusive rocks exposed today.