Monazite ssion-track thermochronology as a possible proxy for low-magnitude erosion

Conventional low-temperature thermochronology can resolve cooling typically associated with ~2 6 km of erosion. Lower magnitudes of erosion produced by surface processes and climatic variations are often difficult to quantify. Here, we apply a new, low-temperature thermochronometer (closure temperature <50 25 C), monazite ssion-track (MFT), to the Catalina-Rincon metamorphic core complex, Arizona, USA which has a well-constrained tectonic and paleoclimatic history. In the Catalina-Rincon, traditional low-temperature thermochronology (apatite and zircon fission-track and apatite and zircon U-Th-Sm/He) record timing of cooling related to metamorphic core complex detachment faulting and subsequent Basin and Range normal faulting (26 20 Ma and 15 12 Ma, respectively). We collected two monazite ssion-track age-elevation profiles across southwestern and northeastern extent of the Catalina-Rincon. The southwestern profile (~ 1000 m relief) records a Plio-Pleistocene age-elevation trend, with older ages at higher elevations (4.5 1.5 Ma). Whereas the northwestern profile (~ 500 m) records a late Miocene-Pleistocene age-elevation trend, also with older ages at higher elevations (8.1 2.0 Ma). Across the two profiles these ages do not correlate with known tectonic activity in the region, they are consistent with Pliocene intensification of the North American Monsoon. However, such a low closure temperature could suggest that fission-tracks in monazite are not stable at surface temperatures and lie in the partial annealing zone. Despite this concern, we attribute Plio-Pleistocene thermochronometric ages to record climate-enhanced erosion during a known period of enhanced precipitation. These results suggest that MFT has potential for dating low-magnitude erosion associated with climate and relief-forming processes.