TS 3387

TS 3387 is a graphical-symbols standard that sets out general rules for showing rock types on geological maps and cross sections. Its technical purpose is to support a consistent visual language so that geological units can be read, compared, and interpreted more clearly across different drawings.

Why rock-type representation needs its own conventions

In geological documentation, symbols are more than decoration: they carry information about lithology, unit boundaries, and the structure of the interpreted ground. Separate rules for rock types help distinguish, for example, units that differ in composition, origin, or age. This kind of convention makes map legends and cross-section graphics easier to read within a shared technical framework.

The standard covers the general principles for representing rock types on geological maps and cross sections. In practice, that means a common approach to how these symbols are presented so their meaning remains consistent across documents. The information here describes the subject matter at a technical level; it does not restate clause-by-clause requirements. In geological work, such conventions support field mapping, compilation, and interpretation by giving all users the same visual reference language.

Graphical symbols in the context of geological mapping

• On geological maps, symbols communicate the type and distribution of rock units quickly.
• On cross sections, the same visual language helps connect surface data with subsurface interpretation.
• Consistent graphics improve comparability between maps prepared by different teams or institutions.
• Rock-type representation is a core part of geological symbology because it directly supports interpretation.