The Global Tectonic Models

The vast geological knowledge of the structure and history of the world unified by the plate tectonic theory has been synthesised with much simplification into the Tectonic models. Ten 'global tectonic' models are presented as Figures 2.4 to 2.13 in the Models Appendix. We have added to Figure 2.2 and Table 2.2 the approximate correlation with our Tectonic models, where appropriate. Where there is no close single equivalent, we have quoted two or more models.

The models must be considered quite idealised. They represent conceptual end members defined from the plate tectonic theory and are not drawn to represent any specific location but to indicate the particular association of rock types and structure that typically occur. It is emphasised that all the models are meant to be self-explanatory, drawn for engineering geology purposes, and to help lead the site investigator on to the site scale models. Each drawing lists the possible lithological and structural associations within the model. A real area is likely to contain parts of a variety of models brought together during a long geological history.

The Tectonic models also list as a guide the more likely initial 'site scale geological' models that could occur within the parent Tectonic model. However, this list is not exhaustive and judgment on each locality must be made. Thus, by identifying the Tectonic model, the site scale models for the project site can be narrowed down to a limited number.

Three principal groups of global Tectonic models have been produced to relate to the foregoing discussion: a group of three relating to intra plate systems (cratonic cores, mobile belts, platforms/basins); a group of two relating to divergent plate boundaries (continental rift, ocean rift) and a group of five relating to convergent plate boundaries (fold and thrust belts, magmatic arc, collision complexes, foreland basins, accretionary prisms).

Case histories related to the models have been added.