Paleostress

Palaeo means past, thus paleostress (or palaeostress) means stresses that acted in the geological past (i.e. thousands to millions of years ago). In Geology paleostress analysis is concerned with deriving the directions along which the stress acted and gave rise to present structural feature in the rocks on earth.

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

Microscopic:

Crystal deformation, including twinning,
pressure solution
Microfractures,
Aligned fluid inclusions.

Macroscopic:

Folding
fracturing
faulting (fracturing accompanied by offset of rock bodies on either side of the fracture surface)

Traditionally, deformation—either folding or fracturing—without dissolution are collectively termed mechanical strain. Both macroscopic and microscopic strain may be elastic, and only exist as long as differential stress 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 (Zoback et al., 1989) which continues as the World Stress Project. Only a small subset of measurements in the WSP database qualify as paleostresses.

A number of regional studies of paleostresses has been undertaken, including Europe (Bergerat, 1987); North America (synthesized by Bird, 2002; Pilger, 2003), Australia (Pilger, 1982).

References

Anderson, E. M., 1951, The Dynamics of Faulting and Dyke Formation, 2nd ed., Oliver & Boyd, Edinburgh.
Aleksandrowski, P. 1985. Graphical determination of principal stress
Bergerat, F., 1987. Stress fields in the European Platform at the time of Africa-Eurasia collision. Tectonics, 6(2): 99-132.
Bird, P., 2002, Stress direction history of the western United States and Mexico since 85 Ma, Tectonics, VOL. 21, NO. 3, doi:10.1029/2001TC001319, 2002.
Pilger, R. H., Jr. 1982, The origin of hotspot traces: evidence from eastern Australia, J. Geophys. Res., 87(B3), 1825–1834, doi:10.1029/JB087iB03p01825.
Pilger, R. H., Jr., 2003, Geokinematics: Prelude to Geodynamics, Springer-Verlag, Berlin.
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 (Dr. rer. nat.) im Fachbereich Geowissenschaften an der Freien Universität Berlin, http://bib.gfz-potsdam.de/pub/str0906/0906.pdf.
Zoback, M., et al., 1989, World Stress Project, Nature.
Zoback, M., and Zoback, M., 1986, DNAG volume.