3.9 Planar structural units
3.9.1 General properties and rules
Planar structural units include many large- and small-scale structures, such as cleavages, foliations, axial planes, joints and faults. This Code only deals with those structures which are sufficiently large and prominent to be mappable at ordinarily used map scales, and which can be recorded directly in the field or with the aid of remote sensing. They are surfaces formed by fracturing (Fig. 16), i.e. fracture zones, joint zones, faults, fault zones, fault complexes, fault systems and thrusts. Subtypes, variants and related units are included in several of these unit divisions. The mutual relationship between units with the rank of zone, set, system and complex is shown in figure 17. Unconformity surfaces are dealt with separately in Section 3.7. The units dealt with in the present section can be given formal names. The proper name component can consist of one or two geographical names (or alternative names on the continental shelf, Section 2.2.4). If two geographical names are used these should be names of places near the extremities of the structure. These names should be linked with a dash (see Chapter 2 and Section 2.2.3). When thrusts are being named (Section 3.9.9) these are to be given the same geographical name as the proper name of the nappe or thrust sheet of which they form the floor or sole.
