Reconnaissance paleomagnetic study of the Eocene Admiralty Island volcanics, southeast Alaska: evidence for pre-late Eocene accretion
Paleomagnetic data have shown that many of the terranes in southern and southeastern Alaska originated in equatorial paleolatitudes. The ages(s) of accretion of these terranes is much debated and paleomagnetic studies constraining this age are limited. As part of a larger study, reconnaissance samples of the Admiralty Island Volcanics (Eocene) were collected at Deepwater Point and Little Pybus Bay on the southern coast of Admiralty Island. Thermal or AF cleaning effectively isolated stable magnetic components in most specimens. Homoclinal dip of the flows precludes a fold test and reversals were not observed. However, 3 penecontemporaneous feeder dikes have magnetic directions which are statistically different from the magnetic directions of the flows they intrude (baked contact test). In addition, the flows have not been affected by a regional overprinting observed in most pre-Tertiary rocks. Thus, these magnetic directions are provisionally interpreted as primary. Assuming a reversed geomagnetic polarity during the eruption of the flows, the mean direction is not significantly different than the expected North American direction. Although more data are necessary to prove a primary remanence and to insure that secular variation has been averaged out, the preliminary evidence suggests that the Southern Alaska superterrane had accreted to North American by Eocene time. These results are similar to findings in south central Alaska, which also suggest that the major terrane translation and had been completed by the early Tertiary.
- Research Organization:
- Vanderbilt Univ., Nashville, TN (USA)
- OSTI ID:
- 6461499
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALASKA
PLATE TECTONICS
VOLCANIC ROCKS
PALEOMAGNETISM
PETROLOGY
EOCENE EPOCH
GEOLOGIC HISTORY
MAGMATISM
PETROGENESIS
VOLCANISM
CENOZOIC ERA
FEDERAL REGION X
GEOLOGIC AGES
GEOLOGY
IGNEOUS ROCKS
MAGNETISM
NORTH AMERICA
ROCKS
TECTONICS
TERTIARY PERIOD
USA
580203* - Geophysics- Geophysical Survey Methods- (1980-1989)
580300 - Mineralogy
Petrology
& Rock Mechanics- (-1989)