Encyclopedia of Engineering Geology

2018 Edition
| Editors: Peter T. Bobrowsky, Brian Marker

Cap Rock

  • Rosalind MunroEmail author
Reference work entry
DOI: https://doi.org/10.1007/978-3-319-73568-9_43


The upper rock material that is more resistant to erosion than the underlying rock material; it also refers to a sedimentary unit of lower hydraulic conductivity than that of the underlying oil or gas reservoir rock that restricts upward migration of hydrocarbons, thus effectively capping the reservoir.

In geomorphology, the upper rock material that is more resistant to erosion than the underlying rock material is called cap rock. Cap rock typically forms a distinctive ledge at the crest of an escarpment (Fig. 1). An irregular escarpment that extends for more than 250 km in the northern part of western Texas in the American southwest marks the boundary between a gently undulating upland surface known as the High Plains of West Texas and New Mexico, with elevations ranging from 1,000 to 1,500 m, and the dissected rolling plains of Central Texas to the east, with elevations typically 300–500 m lower (Collins 1984). Approximately 120 km southeast of Amarillo, Texas, is Caprock...
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  1. Collins EW (1984) Styles of deformation in Permian strata, Texas Panhandle. Bureau of Economic Geology, The University of Texas at Austin Geological Circular 84-4. http://www.lib.utexas.edu/books/landscapes/publications/txu-oclc-11850252/txu-oclc-11850252.pdf. Accessed Oct 2016
  2. Machette MN (1985) Calcic soils of the southwestern United States.In: Weide DL (ed) Soils and quaternary geomorphology of the southwestern United States. Geological Society of America Special Paper, vol 203, pp 1–21. https://www.nrc.gov/docs/ML0037/ML003747879.pdf. Accessed Dec 2016

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Authors and Affiliations

  1. 1.Amec Foster WheelerLos AngelesUSA