Reference work entry
A platform is a tectonic unit of the crust that is relatively stable and has not been deformed or metamorphosed. Typical examples are the North China Platform, Yangtze Platform, and Tarim Platform. Platforms usually have a ‘double-layered structure’, in which the upper part has not been deformed or metamorphosed (1 in the diagram) and is generally a horizontal sedimentary cover that lies on top of a strongly deformed and metamorphosed crystalline basement above an unconformity (2 in the diagram). The unconformity surface marks the period of stable platform formation (Fig. 23).
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