Abstract

After two decades, paleomagnetic study of Cretaceous plutonic, volcanic, and sedimentary rocks consistently shows that both the continental borderland and the batholithic terrane of peninsular California have moved north 14° ±5° and rotated 25° to 40° clockwise between the end of the Cretaceous and the end of the Paleocene. A variety of geologic data across the borderland-batholith boundary, within the peninsula, across the Gulf of California, and within the State of Sonora, Mexico, appear to preclude the existence of a megashear along which peninsular California could have traveled northward. Lacking an acceptable scenario for moving the rocks from their proposed position of magnetization to their present position, the data of paleomagnetism and other elements of geology are in direct conflict. The resolution of this enigma will require an important revision of current assumptions.

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