Permeability Alteration CIRF.B Simulation of the Piceance Basin,
Colorado. Permeability is determined from the sediment composition and texture.
The very low permeability of the lower-lying sediments reflects their shaly
composition compared to the more permeable overlying sandy units (or sediments).
Also shown is the change through time--20 million years (top) to 40 million years
(bottom).