Angular Unconformity

Definition - What does Angular Unconformity mean?

Angular Unconformity is a type of rock unconformity in which depositions of horizontally parallel strata of sedimentary rocks are formed on the eroded and tilted layers of nearby sedimentary rocks. Due to this formation an angular discordance is created with the overlying horizontal layers. With time further orogenic activities take place which further deform and tilt the sedimentary rocks.

Petropedia explains Angular Unconformity

Angular Unconformity in a sedimentary rock arises due to the erosion of its tilted layers. These eroded surfaces of the sedimentary rocks get buried under the horizontal layers of the young sedimentary rocks. Angular Unconformities in the rocks are created based on the following steps:

  • Sediments get weathered from land and move into the sea where they accumulate at the seabed and over millions of years are converted into layers of rock.
  • As the earth's crust constantly shifts, lifts or tilts, it collides with this new formation at the seabed and tends to lift it above the seabed where it is eroded or weathered again by nature.
  • Because of this natural erosion, the edges of the tilted layers become flat.
  • Finally the sea level rises and the land sinks in the sea which again washes down the sediments and new horizontal layers are formed which look like angled unconformities in the rock formation.

It takes hundred of million years to produce Angular Unconformities in the rocks.

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