2. Widespread melting of the CLM in the mid-Tertiary is plausible if the southern Rockies metasomatized in the early Tertiary by fluids derived from the dehydration of shallowly subducting oceanic lithospere. Farmer et al. : Mantle Source Volumes of Ignimbrite Flare Up

3. HYPOTHESIS : The Rockies rose immediately after the Laramide as a thermal response to the exposure of mantle lithosphere to upwelling of hot sub-lithospheric mantle (slab roll back). Slab roll back (Farmer et al.)