Late Mesozoic to Cenozoic coolong histories of the Sangre de Cristo Mountains, Colorado and New Mexico
Shari A. Kelley
Apatite fission-track (FT) data collected in the Sangre de Cristo Mountains adjacent to the northern Rio Grande rift of New Mexico and Colorado indicate that rocks now exposed in the eastern margin of the rift cooled during uplift and erosion in a complex, three-dimensional pattern. The Santa Fe Range portion of the Sangre de Cristo Mountains cooled during the early stage of the Laramide orogenic event (Late Cretaceous– Eocene). At least three portions of the range, the high elevation samples at La Veta Pass, Trinchera Peak and Wheeler Peak, cooled during the late stage of the Laramide event (Eocene) and during the development of a regional late Eocene erosion surface. In contrast, Blanca Peak and the lower elevation samples at La Veta Pass, Trinchera Peak and Wheeler Peak cooled during early extension of the Rio Grande rift and waning of regional volcanism in the late Oligocene and early Miocene. Cooling rates increased from the early phase of the Laramide event (3-4°C/Ma followed by 1 °C/Ma) to the late phase of the Laramide event (3-4°C/Ma) to early development of the Rio Grande rift (5-9 °C/Ma). Blanca Peak, which is located at the intersection of three normal faults bounding the deep side of a half-graben (San Luis basin), has cooled very rapidly (9 °C/Ma). Tectonic denudation on three sides has possibly allowed unusually rapid isostatic uplift.
- Kelley, Shari A., 1990, Late Mesozoic to Cenozoic coolong histories of the Sangre de Cristo Mountains, Colorado and New Mexico, in: Tectonic development of the southern Sangre de Cristo Mountains, New Mexico, Bauer, Paul W.; Lucas, Spencer G.; Mawer, Christopher K.; McIntosh, William C., New Mexico Geological Society, Guidebook, 41st Field Conference, pp. 123-132.