1. Dismemberment and northward migration of the Cordilleran orogen: Baja-BC resolved.
- Author
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Hildebrand, Robert S.
- Subjects
- *
PALEOMAGNETISM , *LARAMIDE orogeny , *IGNEOUS intrusions , *PORPHYRY - Abstract
Paleomagnetic results indicate that much of the North American Cordillera migrated more than 1000 km northward during the 80-58 Ma Laramide event, yet geologists cannot find either the faults along which such movement might have taken place or readily identifiable piercing points to document offset. Here, I suggest that the sinistral Texas Lineament, which extends west-northwest from the Gulf of Mexico to the Cordilleran fold-thrust belt southwest of Las Vegas, and the sinistral Lewis & Clark transverse zone, located about 1300 kilometers to the north, and extending from southern Vancouver Island east-southeast to the thrust belt in the Helena salient, can be restored to one through-going zone to provide a piercing point that constrains meridional migration. I interpret the zone as the result of plate interactions on a left-stepping transform margin formed along the southern margin of North America during Jurassic opening of the Atlantic Ocean. The structure was dismembered and partly transported northward along faults in and/or adjacent to the Cordilleran fold-thrust belt. The proposed restoration also reunites two conspicuous bands of Late Cretaceous-Paleocene slab-failure plutons and porphyry copper deposits into a single zone extending continuously along western North America. This reconstruction obviates the need for Laramide flat slab subduction. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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