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An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger layer, but the term is used to describe any break in the ...
Explanations: A – folded rock strata cut by a thrust fault; B – large intrusion (cutting through A); C – erosional angular unconformity (cutting off A & B) on which rock strata were deposited; D – volcanic dyke (cutting through A, B & C); E – even younger rock strata (overlying C & D); F – normal fault (cutting through A, B, C & E).
Also called Indianite. A mineral from the lime-rich end of the plagioclase group of minerals. Anorthites are usually silicates of calcium and aluminium occurring in some basic igneous rocks, typically those produced by the contact metamorphism of impure calcareous sediments. anticline An arched fold in which the layers usually dip away from the fold axis. Contrast syncline. aphanic Having the ...
The Knox lies beneath a unconformity known as the Knox Unconformity. There is well-developed karst topography at the top of the Knox Supergroup. This demonstrates a prolonged period of erosion. This has modern economic impact because of forming reservoirs for hydrocarbons as well as some mineral deposits. [2]
Hutton's Unconformity is a name given to various notable geological sites in Scotland identified by the 18th-century Scottish geologist James Hutton as places where the junction between two types of rock formations can be seen. This geological phenomenon marks the location where rock formations created at different times and by different ...
Prior to the deposition of the Bass Formation, these rocks were uplifted to the Earth's surface from mid-crustal depths and eroded to form the surface of the nonconformity on which the Unkar Group lies. As these rocks were uplifted from mid-crustal depths, the timing of their cooling was recorded in cooling ages of feldspars and other minerals ...
The unconformity between the Tonto Group and the Vishnu Basement Rocks is a nonconformity. The break between the Tonto Group and the Grand Canyon Supergroup is an angular unconformity. [2] [3] [4] Powell's Great Unconformity is part of a continent-wide unconformity that extends across Laurentia, the ancient core of
In geology, a diastem is a short interruption in sedimentation with little or no erosion. [1] They can also be described as very short unconformities (more precisely as very short paraconformities). [2]