Unconformity


Also found in: Dictionary, Thesaurus, Wikipedia.
Related to Unconformity: disconformity

unconformity

[¦ən·kən′fȯr·məd·ē]
(geology)
The relation between adjacent rock strata whose time of deposition was separated by a period of nondeposition or of erosion; a break in a stratigraphic sequence.

Unconformity

 

(geology), the occurrence of relatively young strata of rock on the erosion surface of older strata. There are two main types of unconformities: parallel and angular. In parallel unconformities (disconformities), strata of different ages lie parallel to one another and are separated only by an erosion surface—a stratigraphic break. In angular unconformities (disconformities), strata of different ages are not only separated by an erosion surface but dip at different angles; as a result, the ends of the old strata abut the base of the younger overlying stratum. Angular unconformities are formed when previously deposited strata have been tilted or folded and then the upper parts of the strata destroyed (by marine erosion, for example) and layers of a new stratum deposited on the erosion surface.

The study of unconformities is of great importance in elucidating the history of the movements and deformations of the earth’s crust. Analysis of unconformities also helps date magmatic activity, ore formation, and other geological processes.

Mentioned in ?
References in periodicals archive ?
The existence of a pockmark directly over a sediment mound at the unconformity found at a location close to the Oak Bay Fault in Passamoquoddy Bay (Figs.
Seafloor pockmarks and gas seepages, northwestern Bay of Fundy, New Brunswick, Canada
This cover tectonically undisturbed rests over an unconformity that is Bajocian in age and forms the base of the Middle Jurassic succession (Dieni et al., 1983).
The Middle Jurassic Alpine Tethyan unconformity and the eastern Sardinia - Corsica Jurassic high: a sedimentary and regional analysis
The Rift or Beaufortian is marked by the Jurassic unconformity, overlain by a layer of sandstone, the Kuparuk Formation and upper Kingak shale and lower Kingak shale.
Chukchi shelf stratigraphy: core study reveals pre-Cenozoic bedrock
Therefore, the layer volume can be obtained by filling the empty space between the underlying layer and unconformity.
A comprehensive approach to the 3D geological modelling of sedimentary basins: example of Latvia, the central part of the Baltic Basin/Settebasseinide 3D modelleerimine Balti basseini keskosa (Lati) naitel
The Permian-Triassic boundary located near Haftad Gholleh is an erosional unconformity or disconformity, as in other parts of Iran, where Permian sequences contain dolomitic limestone, shale and sandstone situated below the Triassic sequence at a disconformity.
Using conodont elements to distinguish Permian-Triassic boundary disconformity near Haftad Gholleh, central Iran
Seismic interpretation reveals a regional Early Miocene Unconformity (EMU) separating pre-Oligocene to Miocene rifted basement from overlying undeformed Upper Miocene-Pliocene bathyal sediments.
Mazlan Madon, Cheng Ly Kim, Robert Wong, 2013, The structure and stratigraphy of deepwater Sarawak, Malaysia: Implications for tectonic evolution
The depth to the Athabasca unconformity is very shallow, ranging from zero to 350 metres (1,148 ft).
Purepoint to form JV with Cameco, Areva
The Paleocene sequence is separated from the underlying Upper Cretaceous sequence by a regional unconformity with local conglomerate at its base.
Geophysical and sedimentological evaluation of quaternary groundwater aquifers, eastern Hafit anticline, Al-Ain, United Arab Emirates (UAE)
New research shows that the answer may lie in a second geological curiosity - a dramatic boundary, known as the Great Unconformity, between ancient igneous and metamorphic rocks and younger sediments.
'The Great Unconformity' may hold key to understanding Cambrian explosion
The findings described here are also supported, as (1) the Cervini and Muntiacicni split is reported at the transition of Miocene-Pliocene; due to this reason Early Pliocene age is referred to these fossil sites, (2) Some isolated molar remains of Hipparion also indicate the Early Pliocene age, and (3) an unconformity is present close to the Miocene-Pliocene boundary.
EVIDENCES OF EARLY PLIOCENE FOSSIL REMAINS OF TRIBE CERVINI (MAMMALIA, ARTIODACTYLA, CERVIDAE) FROM THE SIWALIKS OF PAKISTAN
The company has completed five holes in November and December 2011, with two holes encountering anomalous alteration, and another containing chloritic alteration at various intervals below the unconformity, a common feature found in host rocks containing uranium mineralisation.
-Athabasca Uranium Inc completes 2011 diamond drilling programme at Keefe Lake Uranium Project
The expansion is the result of two years of study by experts supplied via a Compass Foundation grant, and work by the graphic design and communications firm Unconformity.
A lobbying team for D.C. stages

Encyclopedia browser ?
Full browser ?