Journal Title

Journal of Geophysical Research

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The Canelo Hills volcanics are exposed in the Canelo Hills, a northwest trending range in Santa Cruz County, southeast Arizona. The formation is composed of silicic tuffs and flows as well as volcaniclastic conglomerates and sandstones. Strikes of the rocks are generally to the northwest with moderate dips to the southwest and northeast. Apparent age results from the sequence studied paleomagnetically include two published isotopic dates of 147 ± 6 Ma (K-Ar, biotite) and 149 ± 11 Ma (whole rock, Rb-Sr) and a Rb/Sr isochron age, reported here, which indicates an age of 151 ± 2 Ma. Paleomagnetic samples were collected from 17 cooling units in the northern Canelo Hills. Samples from most of these units responded to alternating field (af) demagnetization, and secondary components were generally erased by peak af between 10 and 50 mT. Samples from five sites showed no response to af demagnetization. Thermal demagnetization of samples from these units produced no significant changes in direction of natural remanent magnetization (NRM), although within-site clustering of NRM directions was improved. Data from two sites were rejected because of failure to isolate a well-determined characteristic NRM. Of the remaining 15 sites, 10 sites were of normal polarity, while five sites showed reversed polarity. Intensities of the characteristic NRM ranged from 4 × 10−3 to 3 × 10−1 A/m. The data from these 15 cooling units yield a formation mean direction of I = 29.9°, D = 334.9° with k = 33.4 and α95 = 6.7°. The resulting paleomagnetic pole is at 62.2°N, 130.3° (dp = 4.1°, dm = 7.4°). This pole is between poles obtained from the Summerville and lower Morrison formations. The Canelo Hills pole is thus consistent both in position and age with the Late Jurassic episode of rapid apparent polar wander originally defined by paleomagnetic data from the Summerville and Morrison formations.



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Copyright 1982 American Geophysical Research. The original published version of this article may be found at





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Journal Article