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Features of a geological map
Geologic maps usually illustrate geological features such as rock units and bedding, faults, folds, intrusions, unconformities, river traces etc.
Geologic map can be super-imposed on topographic contour map.

1. Formation: The fundamental unit of the geologic map is the formation. A formation is a sequence of rocks sufficiently homogeneous in composition to be regarded as constituting a rock unit. A formation may consist of one rock type e.g. sandstone or a mixture of two e.g. sandy shale, sandy limestone etc.
2. On a geologic map, a formation is designated by a distinctive colour and symbol. The symbol may be a number or letter. The boundary between any two geologic formations is called geological boundary or contact line or geological interface 
3. Outcrop: This refers to a point on the ground surface where bedrock is exposed while still remaining in place.
4. Legend: This refers to a listing of the formations of a geologic map which occur within the mapped area. For each formation, the legend indicates the distinctive colour and symbol, the nature and type of rock.
5. Arrangement. For sedimentary rocks, the legend is arranged in orderly sequence with oldest formation at the bottom, the younger ones above and the youngest at the top.
6. If igneous and metamorphic rocks occur within the mapped area, they are often arranged in a separate legend.