DESCRIPTION: An Unconformity is a plane representing a large gap in geologic time between the rocks above and below.the plane.
MILE 49.5. Unconformity
REDWALL LS (Miss)
MUAV LS (Camb)
Figure 1 - Grand Canyon - Unconformity (Disconformity). A Disconformity is a gap in time between parallel sedimentary strata. Notice that the Cambrian Muav Limestone is directly adjacent to the Mississippian Redwall Limestone. That is to say, there are no Ordovician, Silurian, or Devonian rocks here. In places within the Grand Canyon there are Devonian rocks (Temple Butte Formation). Here, the unconformity represents about 145 million years of missing time. The upper limit of the Redwall is marked by the beginning of the Supai red shales. (B13)
TAPEATS (570 MYA)
VISHNU SCHIST (1.7 BYA)
Figure 2 - Grand Canyon . Unconformity (Nonconformity). Outcropping of the Great Unconformity (1.1 billion years missing) A Nonconformity is a gap in time between sedimentary rock and crystalline rock.( D11)
Figure 3 - Grand Canyon. Angular Unconformity. Viewed from Navajo Point at the east end of the park. Note the distinctive Angular Unconformity between the PreCambrian Grand Canyon Series below and the Cambrian Tapeats above ("The Great Unconformity"). An Angular Unconformity is one in which the beds below the gap in time are at an angle to the beds above and parallel to the the gap.