stage

noun

The major subdivision of a series. A stage is the fourth order unit in chronostratigraphy, the equivalent of age in terms of geologic time units. It refers to the body of rock accumulated during one age unit. When used formally the initial letter of the term is capitalized, e.g. Frasnian Stage. In palaeoclimatology, a climatic, and partly geologic-climatic, term usually defined by a series of sediments or a sequence of fossil assemblages and named at a type locality. For example, the Hoxnian (a temperate stage) is named for organic interglacial deposits at Hoxne, Suffolk, England. The degree of development of a land-form or landscape over time, and which traditionally has been described by the terms `youthful`, `mature`, and `old age` (see Davisian Cycle). The recognition of such stages implies an orderly evolution and this is now seen as unlikely for many parts of the Earth`s land surface.