Early Cretaceous paleolatitude of the Yukon-Koyukuk province, Alaska

Journal of Geophysical Research Solid Earth
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Abstract

We report results from a paleomagnetic study of the Yukon-Koyukuk province, a key region for reconstructing the Cretaceous paleogeography of northern Alaska and northeastern Asia. The province lies between the displaced continental fragment of Arctic Alaska and the accreted terranes of southern Alaska. Although Lower Cretaceous volcanogenic rocks of the Yukon-Koyukuk province preserve primary remanent magnetizations, the primary component is masked by a pervasive overprint. The over-printing magnetization, which has dual polarity, was acquired after a Late Cretaceous orogeny left the region highly deformed. By fitting planes to tilt-corrected thermal demagnetization data and solving for the best intersection of the corresponding remagnetization circles, we separated the primary component, presumably a vestige of the original thermoremanent magnetization, from the overprinting component of the natural remanence. The primary magnetization corresponds to a mean paleopole of Early Cretaceous age at 60.2°N, 159°E. The mean paleolatitude is 69°N with the 95% confidence ellipse ranging from 60° to 75°N. This analysis was successful because the tilt corrections of the sampled strata had sufficient variation to ensure a strong intersection of the remagnetization circles. We infer that Lower Cretaceous rocks of the Brooks Range and the Yukon-Koyukuk province were once separated by a wide ocean basin that was closed by subduction, probably during the Cretaceous. The northern limb of the Angayucham terrane, which lies between the Brooks Range and the Yukon-Koyukuk province, may contain remnants of the now-closed ocean basin.

Publication type Article
Publication Subtype Journal Article
Title Early Cretaceous paleolatitude of the Yukon-Koyukuk province, Alaska
Series title Journal of Geophysical Research Solid Earth
DOI 10.1029/JB093iB10p11735
Volume 93
Issue B10
Year Published 1988
Language English
Publisher American Geophysical Union
Description 18 p.
First page 11735
Last page 11752
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