New Timing and Depth Constraints for the Catalina Metamorphic Core Complex, Southeast Arizona Tectonics
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The Santa Catalina ‐Tortolita ‐Rincon Mountains of Southeast Arizona are a classic metamorphic core complex (MCC) and represent footwall exposures of crustal rocks exhumed by a detachment system. This study presents new evidence for the formation of the majority of ductiledeformation during the Eocene (~46 Ma), synchronous with the emplacement of the regionally signi ficant Wilderness Sills Suite (57 –45 Ma). The evidence is provided by Eocene U ‐Pb ages of syn ‐to late kinematic dikes emplaced in the principal ductile mylonitic fabric of the Catalina forerange, earlier than the brittlenormal fault system and the formation of Tucson basin beginning with the latest Oligocene. Well‐documented shear sense indicators may not re flect extension at that time (Eocene), but more likely the direction of crustal flow now rotated during later extension. Muscovite ‐plagioclase Rb ‐Sr isochron ages of
