Basement (geology)

In geology, the terms basement and crystalline basement are used to define the rocks below a sedimentary platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic or igneous in origin. In the same way the sediments and/or sedimentary rocks on top of the basement can be called a "cover" or "sedimentary cover".

Usage

In a discussion of European geology, the basement generally refers to rocks older than the Variscan orogeny. On top of this older basement Permian evaporites and Mesozoic limestones were deposited. The evaporites form a weak zone on which the harder (stronger) limestone cover was able to move over the hard basement, making the distinction between basement and cover even more pronounced.

In Andean geology the basement refers to the Proterozoic, Paleozoic and early Mesozoic (Triassic to Jurassic) rock units as the basement to the late Mesozoic and Cenozoic Andean sequences developed following the onset of subduction along the western margin of the South American Plate.Teresa Moreno, et. al., The geology of Chile, Geological Society of London, 2007, Ch. 2 Metamorphic and Igneous Basement Complexes, p. 5, ISBN 978-1862392205

When discussing the Trans-Mexican Volcanic Belt of Mexico the basement include Proterozoic, Paleozoic and Mesozoic age rocks for the Oaxaquia, the Mixteco and the Guerrero terranes respectively.A. Gómez-Tuena, Ma.T. Orozco-Esquivel, and...
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