<Table> <Tr> <Td> </Td> <Td> This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations . Please help to improve this article by introducing more precise citations . (March 2015) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations . Please help to improve this article by introducing more precise citations . (March 2015) (Learn how and when to remove this template message) </Td> </Tr> <P> The law of superposition is an axiom that forms one of the bases of the sciences of geology, archaeology, and other fields dealing with geological stratigraphy . In its plainest form, it states that in undeformed stratigraphic sequences, the oldest strata will be at the bottom of the sequence . This is important to stratigraphic dating, which assumes that the law of superposition holds true and that an object cannot be older than the materials of which it is composed . The law was first proposed in the late 17th century by the Danish scientist Nicolas Steno . </P> <P> Superposition in archaeology and especially in stratification use during excavation is slightly different as the processes involved in laying down archaeological strata are somewhat different from geological processes . Man - made intrusions and activity in the archaeological record need not form chronologically from top to bottom or be deformed from the horizontal as natural strata are by equivalent processes . Some archaeological strata (often termed as contexts or layers) are created by undercutting previous strata . An example would be that the silt back - fill of an underground drain would form some time after the ground immediately above it . Other examples of non vertical superposition would be modifications to standing structures such as the creation of new doors and windows in a wall . Superposition in archaeology requires a degree of interpretation to correctly identify chronological sequences and in this sense superposition in archaeology is more dynamic and multi-dimensional . </P>

When does the law of superposition not apply
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