Great unconformity, Grand Canyon, AZ
sedimentary, Grand Canyon National Park, desert, stair-step topography, erosion, strata
Buttress Unconformity, northern Arizona. In buttress unconformities, the younger material
is deposited against the older material, resulting in the apparent truncation of the younger rock. On
closer inspection, however, one can see erosional features along the contact to indicate its depositional
origin. (ID SrU-25)