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".
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 formed 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.
The term basement is used mostly in disciplines of geology like basin geology, sedimentology and petroleum geology in which the (typically Precambrian) crystalline basement is not of interest as it rarely contains petroleum or natural gas.
- Teresa Moreno, et al., The geology of Chile, Geological Society of London, 2007, Ch. 2 Metamorphic and Igneous Basement Complexes, p. 5, ISBN 978-1-86239-220-5
- A. Gómez-Tuena, Ma.T. Orozco-Esquivel, and L. Ferrari Igneous petrogenesis of the Trans-Mexican Volcanic Belt, Ch 5, in Susana A. Alaniz-Álvarez and Angel F. Nieto-Samaniego, eds., Geology of México, Geological Society of America Special Paper 422, 2007, p.142 - 145 ISBN 978-0-8137-2422-5
- Gay, Parker (2002) Mapping Geologic Structure of Basement and Role of Basement in Hydrocarbon Entrapment, Search and Discovery Article #40052 (adapted from: AAPG Explorer (November and December, 1999)
- Parker, Sybil P. (Ed.). 1997. McGraw-Hill Dictionary of Geology and Mineralogy. New York: McGraw-Hill.
- Bates, Robert L. and Julia A. Jackson (Eds.) 1994. Dictionary of Geological Terms. American Geological Institute. New York: Anchor Books, Doubleday Dell Publishing.
- Ben A. Van Der Pluijm (Editor), 1996, Basement and Basins of Eastern North America, Special Paper Geological Society of America ISBN 978-0-8137-2308-2