Apatite fission track ages for samples collected from three mountain ranges on the eastern margin of the Rio Grande rift are used to examine the late Cretaceous to middle Miocene uplift and erosional history of north central New Mexico. The dates indicate that uplift and erosion was in progress in the Sandia Mountains near Albuquerque and in the Taos Range portion of the Sangre de Cristo Mountains near Taos at least 30-35 m.y. ago. Uplift and erosion continued in the Sandia Mountains at a relatively costant rate (81 m/m.y.) until 15 Ma; the rate of uplift and erosion in this area has approximately tripled in the past 15 m.y.(230 m/m.y.).

Igneous activity in the Taos Range has largely obscured the early Tertiary uplift and erosional history of this portion of the Sangre de Cristo Mountains. A fission track date from one of the middle Teritary intrusions in the Taos Range is used to calculate the cooling rate due to uplift and erosion in this area for the past 14-15 m.y. (210 m/m.y.). The uplift and erosion rates derived from the fission track data for the past 14-15 m.y. are similar to those obtained from other geological evidence. In contrast to the Oligocene to Miocene ages found in the other two areas, the apatite fission track ages from the Santa Fe Range portion of the Sangre de Cristo Mountains near Santa Fe are Late Cretaceous to early Eocene. These dates record the cooling of the area due to uplift and erosion during the Laramide event. The preservation of these older ages indicates that the Santa Fe Range was a low-lying area during the Oligocene to Miocene, while the surrounding areas (Sandia Mountains and Taos Range) underwent uplift and erosion. Volcanic activity occurred in the vicinity of the two areas of positive relief. Localized crustal extension associated with the volcanism may have contributed, in part, to the uplift of these areas. Using simple, two-dimensional thermal models, we found that the apparent denudation rates derived from the fission track age data may represent true denudation rates derived from the fission track age data may represent true denudatin rates, given certain geologic conditions that may have existed during the uplift and erosion of the Sandia Mountains in the middle Tertiary and the Santa Fe Range in the late Cretaceous.