Abstract
A 1.15 b.y. old diabase sill is exposed in the Rock Canyon monocline of the Salt River Canyon within the Transition Zone physiographic province of east-central Arizona. Various interpretations have been advanced regarding the age relationship of monoclinal folding and sill intrusion. Seventy oriented samples for paleomagnetic analysis were collected from 10 sites within the diabase sill through the hinge zone of the Rock Creek monocline. Alternating field demagnetization to peak fields of 50–70 mT was sufficient to isolate the characteristic natural remanent magnetization, which is a thermoremanent magnetism acquired during cooling of the sill. Statistical analysis of the resulting paleomagnetic data indicates passage of the fold test at the 95% confidence level. The monoclinal folding clearly post-dates intrusion of the diabase sill. When added to other geologic evidence, these data indicate that the Rock Canyon monocline is a Laramide compressional feature.
Published Version
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