An unconformity is a contact between two rock units in which the upper unit is usually much younger than the lower unit. There are three forms of unconformities: disconformity, nonconformity, angular unconformity. A nonconformity exists between sedimentary rocks and metamorphic or igneous rocks when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock.
Related Journals of Nonconformity Geology
Earth Science & Climatic Change, Coastal Zone Management, Quaternary Research, Journal of Geophysical Research, Earth Surface Processes and Landforms