Publication History: This article was written especially for "Crain's Petrophysical Handbook" by E. R. Crain, P.Eng in 2007. This webpage version is the copyrighted intellectual property of the author.

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Coding Lithology on Plots
Both hand drawn and computer drawn plots may be coded with symbols to represent various rock types and accessory information. The recommended codes and colours are given in the illustrations below. Some symbols and codes must be simplified for computer use, and the coding or shading should be identified in a legend on each plot or diagram.

For a complete list of abbreviations and symbols used in geological sample descriptions, see This List.


Lithology codes as displayed on a modern computer drawn strip log. Older strip logs are black and white illustrations but colour may be added by hand.

Lithology coding on petrophysical analysis depth plots is less detailed than on sample description logs. The codes are somewhat limited by the software designer but the colours are usually under user control.

Typical lithology codes from a modern petrophysical software package 











Log analysis lithology plot (left) in a complex sequence, and sample description plot (right) over the same interval.

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