Fission track analysis of the footwall of the Catalina detachment-fault, Arizona: Tectonic denudation, magmatism, and erosion

New apatite and zircon fission track ages obtained from the footwall of the ,Catalina metamorphic core complex record a complicated cooling history ass ociated With mid-Tertiary extension. Zircon fission track ages record the p rogressive unroofing of the Catalina metamorphic core complex along the Cat alina detachment fault. Zircon fission track ages range from 31.9 to 19.4 M a, generally decrease in the hanging-wall slip direction, and yield slip ra tes along the Catalina detachment fault ranging from 1.2 to 12 km Myr (-1). In contrast, apatite fission track ages increase in the hanging wall slip direction. Samples from the main range of the Santa Catalina Mountains yiel d apatite fission track ages of 20.5 to 14.6 Ma; samples from the Santa Cat alina Mountain forerange, located closer to the detachment fault, yield apa tite fission track ages of 21.4 to 18.8 Ma. Rapid cooling (40 degrees to 60 degrees C Myr (-1)) related to detachment faulting is best recorded by zir con fission track ages and higher-temperature thermochronometers in the mai n range and by nearly concordant zircon and apatite fission track ages in t he forerange. Slower cooling (30 - 7 degrees C Myr (-1)) of the footwall is recorded by shortened mean confined fission track lengths (< 14 mu m) and is related to erosional unroofing. Approximately 2 km of late-Tertiary eros ion played a significant role in the unroofing of the footwall of the Catal ina metamorphic core complex in contrast to metamorphic core complexes in w estern Arizona, where detachment faulting is the dominant unroofing mechani sm.