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Colours standing for the age of the rock beneath.
Also known as: Stratigraphic colours, Period colours
On a geological map colour stands for the age of the rock rather than its type, and the colours are conventional — Carboniferous grey-blue, Cretaceous green, Triassic mauve. Because the convention is about age, two different rocks of the same age share a colour.
Represent the age of the underlying rock rather than its type, using conventional colours for each geological period.
Contexts: Technical drawing, Maps
Give two different rock types of the same age the same colour, which is why ornament rather than colour carries lithology.
Contexts: Technical drawing, Maps
Follow conventions established in the nineteenth century and now recommended internationally, though national schemes still vary in shade.
Contexts: Technical drawing, Maps
Flat areas of distinct colour covering a map, bounded by lines and labelled with short letter codes.