Review of paleomagnetic data from the Klamath Mountains, Blue Mountains, and Sierra Nevada; Implications for paleogeographic reconstructions

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Abstract

Paleomagnetic studies of the Klamath Mountains, Blue Mountains, Sierra Nevada, and northwestern Nevada pertain mostly to Jurassic and Cretaceous rocks, but some data also are available for Permian and Triassic rocks of the region. Large vertical-axis rotations are indicated for rocks in many of the terranes, but few studies show statistically significant latitudinal displacements. The most complete paleomagnetic record is from the Eastern Klamath terrane, which shows large post-Triassic clockwise rotations and virtual cessation of rotation by Early Cretaceous time, when accretion to the continent was completed. Data from Permian strata of the Eastern Klamath terrane indicate no paleolatitude anomaly, in contrast to preliminary results from coeval strata of Hells Canyon in the Blue Mountains region, which are suggestive of some southward movement. If these Hells Canyon results are confirmed, some of the terranes in these two regions must have been traveling on separate plates during late Paleozoic time. Data from Triassic and younger strata in the Blue Mountains region indicate paleolatitudes that are concordant with North America. Results from Triassic rocks of the Koipato Formation in west-central Nevada also indicate southward transport, but when this movement ceased is unknown. The Nevadan orogeny may have occurred in the Sierra Nevada during Jurassic accretion of the ophiolitic and volcanic-arc terranes of that province to the continent, whereas what has been considered to be the same orogeny in the Klamath Mountains may have occurred before accretion. Using the concordance of observed and expected paleomagnetic directions as a guide, the allochthonous Sierra Nevada, Klamath Mountains, and Blue Mountains composite terranes seem to have accreted to the continent sequentially from south to north.

Publication type Book chapter
Publication Subtype Book Chapter
Title Review of paleomagnetic data from the Klamath Mountains, Blue Mountains, and Sierra Nevada; Implications for paleogeographic reconstructions
DOI 10.1130/SPE255-p397
Volume 255
Year Published 1990
Language English
Publisher Geological Society of America
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center
Description 13 p.
Larger Work Type Book
Larger Work Title Paleozoic and Early Mesozoic Paleogeographic Relations; Sierra Nevada, Klamath Mountains, and Related Terranes: GSA Special Papers v. 255
First page 397
Last page 409
Country United States
Other Geospatial Blue Mountains, Klamath Mountains, Sierra Nevada
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