A craton is a tectonic unit that has remained stable and has not experienced intense deformation since the Precambrian Period (540 million years ago) or the Pre-Nanhuan Period (800 million years ago). Cratons are similar to the ‘ancient continental platforms’ of the geosyncline-platform theory. A craton generally has a ‘binary structure’, which implies that it is composed of a crystalline basement formed from strong magmatic activity and metamorphism, and a sedimentary cover above an unconformity that has not experienced deformation or metamorphism. The term craton generally refers to all forms of ancient land over geologic history, particularly the ancient Canadian Shield and the Baltic Shield. In China, related terms such as ‘Ghiangnania’ and ‘Cathaysia’ have been proposed and are pending further determination. The term palaeocontinent is also translated into Chinese as having a similar meaning as craton, but this term has more stringent implications for its crustal nature.