Science, Tech, Math › Science Unconformity Types and Examples Share Flipboard Email Print Science Geology Types Of Rocks Landforms and Geologic Features Geologic Processes Plate Tectonics Chemistry Biology Physics Astronomy Weather & Climate By Andrew Alden Geology Expert B.A., Earth Sciences, University of New Hampshire Andrew Alden is a geologist based in Oakland, California. He works as a research guide for the U.S. Geological Survey. our editorial process Andrew Alden Updated March 06, 2017 01 of 05 Diagram of Unconformity Types Unconformity Types and Examples Symbols on the left are for Pennsylvanian age (bottom) and Triassic age (top), separated by at least 50 million years. Diagram (c) 2011 Andrew Alden, licensed to About.com ( fair use policy) Unconformities are breaks or gaps in the geologic record, as shown by the arrangement of sedimentary (stratigraphic) features in the rock. This gallery shows the basic unconformity types recognized by U.S. geologists plus photos of examples from outcrops. This article gives more details about unconformities. Here are the four main unconformity types. British geologists classify the disconformity and paraconformity as nonsequences because the rock beds are conformable, that is, parallel. Learn more in this article. 02 of 05 Angular Unconformity, Pebble Beach, California Unconformity Types and Examples. Photo (c) 2010 Andrew Alden, licensed to About.com ( fair use policy Strongly tilted sedimentary rocks have been eroded and covered with much younger flat-lying sediments. Wave erosion of the young layers has exhumed the old erosion surface. 03 of 05 Angular Unconformity, Carlin Canyon, Nevada Unconformity Types and Examples From the Nevada Geological Attractions Gallery. Photo courtesy Ron Schott, all rights reserved This famous unconformity involves two rock units of Mississippian (left) and Pennsylvanian (right) ages, both of which are now tilted. 04 of 05 Angular Unconformity in Conglomerate Unconformity Types and Examples. Photo (c) 2011 Andrew Alden, licensed to About.com ( fair use policy The tilted pebbles in the lower half mark the bedding plane in this conglomerate. The erosion surface is covered by finer material laid down parallel to the photo frame. The time gap represented here may be very short. 05 of 05 Nonconformity, Red Rocks, Colorado Unconformity Types and Examples From the Red Rocks of Red Rocks Gallery. Photo (c) 2007 Andrew Alden, licensed to About.com ( fair use policy This widespread feature is known as the Great Unconformity, but the Precambrian rock on the right is gneiss overlain by Permian sandstone, making it a nonconformity. It dramatically represents a billion-year time gap.