Distribution, stratigraphy, petrochemistry, and palaeomagnetism of the late Pleistocene Old Crow tephra in Alaska and the Yukon
| Autor: | M. P. Gorton, John A. Westgate, G. W. Pearce, R. C. Walter |
|---|---|
| Rok vydání: | 1985 |
| Předmět: | |
| Zdroj: | Canadian Journal of Earth Sciences. 22:893-906 |
| ISSN: | 1480-3313 0008-4077 |
| DOI: | 10.1139/e85-093 |
| Popis: | Revision accepted January l I, 1985 The late Quaternary Old Crow tephra is a two-pyroxene, calc-alkaline dacite whose known areal extent is broadly delimited by a triangle with apices at the Seward Peninsula, the Wrangell Mountains, and the Old Crow Basin in the northern Yukon. Everywhere the tephra is fine grained (Mdu = 5.33 2 0.32) and moderately to poorly sorted (6u = 1.33 * 0.29). Samples from the extremities of the fall-out zone have similarity coefficients of 0.95. A palaeomagnetic excursion is recorded in sediments just below Old Crow tephra in the Fairbanks area and at Imuruk Lake on the Seward Peninsula. A short, full reversal of the magnetic field has been preserved at the corresponding stratigraphic level near Old Crow in the northern Yukon. Chronological controls based on I4C and fission-track dates and sedimentation rates show that these palaeornagnetic features are almost certainly partial records of the complex geomagnetic Blake Event, which occurred 100- 120 ka ago. New petrochemical data demonstrate that the source of Old Crow tephra is in the eastern Aleutian arc. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|