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Paleomagnetism of mesozoic red chert from Cedros Island and the San Benito Islands, Baja California, Mexico revisited
Author(s) -
Hagstrum Jonathan T.,
Sedlock Richard L.
Publication year - 1992
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/91gl02692
Subject(s) - geology , paleomagnetism , mesozoic , pillow lava , paleontology , clockwise , pacific plate , oceanography , subduction , fold (higher order function) , structural basin , volcanic rock , mechanical engineering , volcano , engineering , tectonics
Previous paleomagnetic study of Mesozoic subduction‐complex rocks on Cedros Island and the San Benito Islands, Mexico, shows that these rocks have been remagnetized; a single‐polarity magnetization was found in chert sections and underlying pillow basalt deposited during a mixed‐polarity interval of the geomagnetic field. Reanalysis of the Cedros and San Benito chert samples (101 total) shows that 13 samples also retain a high blocking‐temperature component of magnetization (600° to 680°C) indicating a polarity stratigraphy and deposition of the bedded chert near 2° ± 3° paleolatitude. These data are similar to those for red chert in California and Japan implying that many of the Mesozoic ophiolitic chert sequences now exposed around the Pacific rim were initially deposited within the equatorial zone of high biologic productivity. These new data also support accretion of the Cedros and San Benito chert to the American margin at tropical paleolatitudes requiring significant northward translation (and clockwise rotation) to bring them to their present position with respect to the continental interior.