Paleostress is a term used in geology (specifically in the fields of

structural geology Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories. The primary goal of structural geology is to use measurements of present-day rock geometries to uncover informatio ...

and

tectonics Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents k ...

) to indicate

mechanical stress In continuum mechanics, stress is a physical quantity. It is a quantity that describes the magnitude of forces that cause deformation. Stress is defined as ''force per unit area''. When an object is pulled apart by a force it will cause elonga ...

that has affected rock formations in the geological past. In practice, a paleostress

tensor In mathematics, a tensor is an algebraic object that describes a multilinear relationship between sets of algebraic objects related to a vector space. Tensors may map between different objects such as vectors, scalars, and even other tenso ...

may be quantified based on the measurement of certain geological structures (e.g. faults), whose specific geometries and spatial organization are theoretically linked to the parameters of the tensor (see

paleostress inversion Paleostress inversion refers to the determination of paleostress history from evidence found in rocks, based on the principle that past tectonic stress should have left traces in the rocks. Such relationships have been discovered from field stud ...

). The latter are quantified through inversion of the structures measured in the field (or potentially on rock samples in the lab). Paleostress is a subset of

within geology. Variations in stress fields within the Earth's crust can result in a variety of mechanical responses: *Microscopic: :*

Crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

deformation Deformation can refer to: * Deformation (engineering), changes in an object's shape or form due to the application of a force or forces. ** Deformation (physics), such changes considered and analyzed as displacements of continuum bodies. * Defo ...

, including twinning, :*

Pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

solution Solution may refer to: * Solution (chemistry), a mixture where one substance is dissolved in another * Solution (equation), in mathematics ** Numerical solution, in numerical analysis, approximate solutions within specified error bounds * Soluti ...

:*Microfractures, :*Aligned

fluid inclusions image:Inclumed.gif, 250px, Trapped in a time capsule the same size as the diameter of a human hair, the ore-forming liquid in this inclusion was so hot and contained so much dissolved solids that when it cooled, crystals of halite, sylvite, gypsum, ...

. *Macroscopic: :*

Folding Fold, folding or foldable may refer to: Arts, entertainment, and media * ''Fold'' (album), the debut release by Australian rock band Epicure *Fold (poker), in the game of poker, to discard one's hand and forfeit interest in the current pot *Above ...

Fracturing Fracture is the separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. If a displa ...

Faulting In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

(fracturing accompanied by offset of rock bodies on either side of the fracture surface) Traditionally, deformations (either folding or fracturing—without

dissolution Dissolution may refer to: Arts and entertainment Books * ''Dissolution'' (''Forgotten Realms'' novel), a 2002 fantasy novel by Richard Lee Byers * ''Dissolution'' (Sansom novel), a 2003 historical novel by C. J. Sansom Music * Dissolution, in mu ...

) are collectively termed mechanical

strain Strain may refer to: Science and technology * Strain (biology), variants of plants, viruses or bacteria; or an inbred animal used for experimental purposes * Strain (chemistry), a chemical stress of a molecule * Strain (injury), an injury to a mu ...

. Both

macroscopic The macroscopic scale is the length scale on which objects or phenomena are large enough to be visible with the naked eye, without magnifying optical instruments. It is the opposite of microscopic. Overview When applied to physical phenomena an ...

and

microscopic The microscopic scale () is the scale of objects and events smaller than those that can easily be seen by the naked eye, requiring a lens (optics), lens or microscope to see them clearly. In physics, the microscopic scale is sometimes regarded a ...

strain may be

elastic Elastic is a word often used to describe or identify certain types of elastomer, elastic used in garments or stretchable fabrics. Elastic may also refer to: Alternative name * Rubber band, ring-shaped band of rubber used to hold objects togeth ...

, and only exist as long as

differential stress Differential stress is the difference between the greatest and the least compressive stress experienced by an object. For both the geological and civil engineering convention \sigma_1 is the greatest compressive stress and \sigma_3 is the weakest, ...

exists, or it may be inelastic -- that is the deformation due to a particular stress event remains even after the stress is removed. In the latter case, inelastic deformation, the stress field responsible for the deformation if it can be inferred, is, then, the ''paleostress''. Anderson's classic analysis of faulting serves as a simple application of paleostress analysis in terms of principal components of stress. Zoback and Zoback's (1986) synthesis of contemporary stress measurements in North America was subsequently expanded to a global study which continues as the World Stress Project. A number of regional studies of paleostresses has been undertaken, including Europe; North America; and Australia.Pilger, R. H., Jr. 1982, The origin of hotspot traces: evidence from eastern Australia, J. Geophys. Res., 87(B3), 1825–1834,

References

*Aleksandrowski, P. 1985. Graphical determination of principal stress *Pascal, C., 2021. Paleostress Inversion Techniques: Methods and Applications for Tectonics, Elsevier, 400 p. https://www.elsevier.com/books/paleostress-inversion-techniques/pascal/978-0-12-811910-5 *Sippel, J., 2009, The Paleostress History of the Central European Basin System, Scientific Technical Report STR09/06, Dissertation zur *Erlangung des akademischen Grades doctor rerum naturalium im Fachbereich Geowissenschaften an der Freien Universität Berlin, http://bib.gfz-potsdam.de/pub/str0906/0906.pdf. {{Structural geology Structural geology Deformation (mechanics)