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RTPrecambrian
 Proterozoic
 Neoproterozoic
 Cambrian
 Russian Federation
 Aldan Shield
 Lower Cambrian
 Eocambrian
 upper Precambrian
SNAldan Shield area, Russian Federation. Used most often to apply to Lower Cambrian, but some have used it to refer to Neoproterozoic. Indexed with additional age terms as applicable. Added to Thesaurus in 1985.