What are the 3 types of unconformity and how can we identify an unconformity?

Before knowing about three types of Unconformity, we need to understand the term unconformity. An unconformity may be defined as an erosional or weathered surface, which separates the younger rocks or strata from the older rocks. It may parallel to the upper strata or makes an angular relationship with each upper rock that is inclined.

Types of unconformity:

Mainly there are three types of unconformity, Angular, Disconformity, and Non-conformity. But we add another type of unconformity called Local unconformity. Let's try to understand all kinds of unconformity-

1) Angular Unconformity: In angular unconformity, the two series of beds (younger and older rock beds) make an angular relationship with each other. Here the lower older series of beds dip at different angles to the younger upper beds. It also includes the case where the unfolded younger strata rest upon the folded older rocks.

2) Disconformity: In disconformity, the two series of beds (the younger series of beds and the lower series of beds) dip at the same angle and in the same direction. It covers a large area and represents a considerable amount of geological time.

3) Non-conformity: Here the younger rocks are of sedimentary origin and the older rocks are of igneous origin. When bedded younger sedimentary rocks overlain the non bedded igneous mass, then a structure is formed such structure is called non-conformity.

4) Local Unconformity: Local unconformity is similar to disconformity but as the name suggests, it covers a small area. It is also known as a non-depositional unconformity. These are generally found in flood-affected areas.

Identification of an Unconformity:

1) The younger series of rocks, which lie above the unconformity, and the older series of rocks, which are present below the unconformity show the different geological structures and both the younger and the older contain different kinds of fossil records. The younger series of rock beds contain high evolutionary organisms and the older series of rock beds contain low evolutionary organisms.

2) Presence of a conglomerate rock bed is highly possible to found an unconformity in the same area.

3) Difference in degree of metamorphism in the younger and the older rocks or the younger series of rocks are less metamorphosed than the rocks of older series. (Metamorphism- It is a process, in which pre-existing rocks are transformed structurally and mineralogically into a new type of rock called metamorphic rock due to the influence of high temperature, pressure, and chemically active fluid.)

4) Unconformities may be recognized by truncation of volcanic necks or other volcanic intrusions.

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