Clastic dike

A clastic dike is the geological term used to describe a seam of 'foreign' sedimentary material (often breccia) that fills cracks in sedimentary strata. Since sedimentary strata are usually formed by deposition in the horizontal plane, they usually remain in that orientation, except when subjected to tilt. Clastic dikes are, therefore, more likely to be vertical or near-vertical. They can vary in thickness from a few centimetres to several metres wide and their height is usually many times their width.

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Clastic dikes are typically produced by seismic disturbance of high water content sediments. Examples include sand filled sills and dikes in mudstones injected by fluidized sand from below during a penecontemporaneous earthquake event in the Annedale, Northern Wairarapa, New Zealand tectonic area.^[1] Clastic dike swarms associated with salt dome diapirism is reported from the Dead Sea region. ^[2]

Clastic dikes are used in paleoseismological studies as evidence of ancient earthquakes.^[3]

References

1. ^ G. Neef, A clastic dike-sill assemblage in late Miocene (c. 6 Ma) strata, Annedale, Northern Wairarapa, New Zealand, New Zealand Journal of Geology & Geophysics, 1991, Vol. 34: 87—91 http://www.rsnz.org/publish/nzjgg/1991/11.php
2. ^ Tsafrir Levi et al., Earthquake-induced clastic dikes detected by anisotropy of magnetic susceptibility, GEOLOGY, February 2006, v. 34; no. 2; p. 69–72; http://geophysics.tau.ac.il/personal/shmulik/ClasticDikes-AMS-Geology06.pdf
3. ^ Kevin G. Stewart, 2003, Paleoseismology http://www.unc.edu/~kgstewar/web_pages/paleoseismology.html