Geological maps portray the distribution of different rock types, the location of faults, shear zones and folds, and the orientation of primary and structural features. Mines, quarries, mineral occurrences, fossil localities, geochronological sampling sites, oil and water wells may also be shown. Geological maps illustrate rock relationships that enable the depositional, intrusive, and structural history of an area to be established, and the three-dimensional geometry to be visualized. They provide fundamental information for mineral and petroleum exploration and for hydrological and environmental investigations.

In small areas such as exploration tenements where detailed maps are required, it is common practice to undertake grid mapping. After a grid is surveyed and pegged, the geologist carries out detailed traverses along grid lines. Rock types, lithological contacts, and alteration are noted and structural measurements made using a compass-clinometer. Information may be recorded by hand on traverse maps or collected digitally...