What is the difference between a nonconformity and an angular unconformity

Several types of unconformity are recognized refer to figure above : Disconformity: exists where the layers above and below an erosional boundary have the same orientation Nonconformity: develops where sediments are deposited on top of an eroded surface of igneous or metamorphic rocks Paraconformity: strata on either side of the unconformity are parallel, there is little apparent erosion Angular unconformity: strata is deposited on tilted and eroded layers such as at Siccar Point These six photos are examples of different types of unconformities from around the world.

Use dropdown boxes to label these correctly and click the "Check" button to see if you are correct. Remember the discussion board for exchanging questions, ideas and answers with fellow students or a TA. To see full size images right-click alt-click and pick "view image". You saw this view of Siccar point earlier. The diagonal band is roughly metres thick. Here tilted sedimentary rocks of Precambrian age lower half of photo are overlain by younger sedimentary rocks of Phanerozoic age Cambrian and younger, upper half of photo.

The two packages of strata are clearly separated by an angular unconformity that is best seen just left of the center of the photo. Angular Unconformities are those where an older package of sediments has been tilted, truncated by erosion, and than a younger package of sediments was deposited on this erosion surface.

Disconformities are also an erosion surface between two packages of sediment, but the lower package of sediments was not tilted prior to deposition of the upper sediment package. The sequence of events is as follows: First: subsidence and sediment deposition ; Second: uplift and erosion ; Third: renewed subsidence and deposition.

Because the beds below and above the disconformity are parallel, disconformities are more difficult to recognize in the sedimentary record. In the diagram at left, the disconformity is indicated by an irregular black line between the 3rd and 4th rock unit from the bottom.

A nonconformity is what its called when sedimentary rock strata are over crystalline metamorphic or igneous strata. A disconformity is when the sedimentary strata is over another sedimentary strata. Thursday, November 11, Sign in. Forgot your password? Get help. Password recovery. Geology Page. Home Latest News Video.

Debris Flow Dynamics. Sampling Hot Molten Lava. Incredible moment Anak Krakatau erupts, Oct Download Google Earth For Free. Remote Sensing Downloader. Thunder Egg. What are Types of Unconformity? Geologic Features Top Posts.