Unconformity

An unconformity represents a break in the layers of rocks when no sediment was deposited. It could have been a short time or up to an interval of millions of years. the rocks below the unconformity will be older than those above it and the age difference may be millions of years the older and younger rocks are separated by a plane of unconformity the angle of dip and strike of rocks above and below the unconformity will be different above theplane of unconformity a basal conglomerate may form of pebbles of the older rocks in a sand or mud matrix

sediments deposited as beds of sedimentary rock beds of sediment are uplifted, folded or tilted sediments are eroded younger sediments are laid down in horizontal beds on te eroded surface to make a plane of unconformity further uplift and erosion exposes the angular unconformity

An angular unconformity can be identified in several ways: a difference in strike and dip of beds below and above line of unconformity older beds cut off by younger rocks above plane of unconformity faults in the older rocks are cut off by younger rocks above the plane of unconformity fold axial plane trace in older rocks can be cut off by younger rocks above plane of unconformity igenous intrustions such as dykes, sillis and mineral veins cut off presence of a basal bed or basal conglomerate one or more ages of rocks may be missing

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Origin of Angular Unconformities