Country rock (geology)

Country rock is a geological term meaning the rock native to an area. It is similar and in many cases interchangeable with the terms basement and wall rocks.

The term is used to denote the usual strata of a region in relation to the rock which is being discussed or observed.

The following are areas in geology when the term country rock is used;

• Intrusive settings; when describing a pluton or dike one may describe the igneous rock as intruding the surrounding country rock, the rock into which the pluton has intruded.
• In describing the texture or structure of lit-par-lit (layer by layer) intrusion, the intrusive is described in relation to the country rock or wall rock
• Alluvial settings; when describing recent alluvium the material that has arrived through volcanic, glacial or fluvial action can be described as a veneer on the country rock