The law of superposition is an axiom that forms one of the bases of the sciences of geology, archaeology, and other fields pertaining to geological stratigraphy. In its plainest form, it states that in undeformed stratigraphic sequences, the oldest strata will lie at the bottom of the sequence, while newer material stacks upon the surface to form new deposits over time. This is paramount to stratigraphic dating, which requires a set of assumptions, including that the law of superposition holds true and that an object cannot be older than the materials of which it is composed. To illustrate the practical applications of superposition in scientific inquiry, sedimentary rock that has not been deformed by more than 90° will exhibit the oldest layers on the bottom, thus enabling paleontologists and paleobotanists to identify the relative ages of any fossils found within the strata, with the remains of the most archaic lifeforms confined to the lowest. These findings can inform the community on the fossil record covering the relevant strata, to determine which species coexisted temporally and which species existed successively in perhaps an evolutionarily or phylogenetically relevant way.
Layer upon layer of rocks on north shore of Isfjord, Svalbard, Norway. Since there is no overturning, the rock at the bottom is older than the rock on the top by the law of superposition.
The law of superposition was first proposed in 1669 by the Danish scientist Nicolas Steno, and is present as one of his major theses in the groundbreaking seminal work Dissertationis prodromus (1669).[1]
In the English-language literature, the law was popularized by William "Strata" Smith, who used it to produce the first geologic map of Britain.[2] It is the first of Smith's laws, which were formally published in Strata Identified by Fossils (1816–1819).
Archaeological considerationsedit
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. Human-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.
Other limitations to stratification and superpositionedit
Original stratification induced by natural processes can subsequently be disrupted or permutated by a number of factors, including animal interference and vegetation, as well as limestone crystallization.
Stratification behaves in a different manner with surface-formed igneous depositions, such as lava flows and ash falls, and thus superposition may not always successfully apply under certain conditions.
See alsoedit
The Wikibook Historical Geology has a page on the topic of: Steno's principles
^David Thomas, Robert Kelly, Archaeology, p. 153, Cengage Learning, 2005 ISBN0155058991.
^Patrick Wyse Jackson, The Chronologers' Quest: The Search for the Age of the Earth, Cambridge University Press, 2006 ISBN1139457578, pp.127-8.
General sourcesedit
Hamblin, W.K. The Earth's Dynamic Systems: A Textbook in Physical Geology, by W. Kenneth Hamblin, BYU, Provo, UT, Illus. William L. Chesser, Dennis Tasa, (Burgess Publishing Company, Minneapolis, Minnesota), c 1978, pg. 115, "The Principle of Superposition and Original Horizontality;" pg. 116: The Law of Faunal Succession, "The Principle of Crosscutting Relations;" pg 116-17: "The Principle of Inclusion," (as in the Steno discussion above).
Principles of Archaeological Stratigraphy. 40 figs. 1 pl. 136 pp. London & New York: Academic Press ISBN0-12-326650-5
February 16, 2024
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For other uses see Superposition disambiguation 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 The law of superposition is an axiom that forms one of the bases of the sciences of geology archaeology and other fields pertaining to geological stratigraphy In its plainest form it states that in undeformed stratigraphic sequences the oldest strata will lie at the bottom of the sequence while newer material stacks upon the surface to form new deposits over time This is paramount to stratigraphic dating which requires a set of assumptions including that the law of superposition holds true and that an object cannot be older than the materials of which it is composed To illustrate the practical applications of superposition in scientific inquiry sedimentary rock that has not been deformed by more than 90 will exhibit the oldest layers on the bottom thus enabling paleontologists and paleobotanists to identify the relative ages of any fossils found within the strata with the remains of the most archaic lifeforms confined to the lowest These findings can inform the community on the fossil record covering the relevant strata to determine which species coexisted temporally and which species existed successively in perhaps an evolutionarily or phylogenetically relevant way Layer upon layer of rocks on north shore of Isfjord Svalbard Norway Since there is no overturning the rock at the bottom is older than the rock on the top by the law of superposition Contents 1 History 2 Archaeological considerations 3 Other limitations to stratification and superposition 4 See also 5 References 5 1 General sourcesHistory editThe law of superposition was first proposed in 1669 by the Danish scientist Nicolas Steno and is present as one of his major theses in the groundbreaking seminal work Dissertationis prodromus 1669 1 In the English language literature the law was popularized by William Strata Smith who used it to produce the first geologic map of Britain 2 It is the first of Smith s laws which were formally published in Strata Identified by Fossils 1816 1819 Archaeological considerations editSuperposition 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 Human 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 Other limitations to stratification and superposition editOriginal stratification induced by natural processes can subsequently be disrupted or permutated by a number of factors including animal interference and vegetation as well as limestone crystallization Stratification behaves in a different manner with surface formed igneous depositions such as lava flows and ash falls and thus superposition may not always successfully apply under certain conditions See also edit nbsp The Wikibook Historical Geology has a page on the topic of Steno s principles Harris matrix Principle of cross cutting relationships Principle of faunal succession Principle of lateral continuity Principle of original horizontality Stratification archeology Stratigraphy Structural geologyReferences edit David Thomas Robert Kelly Archaeology p 153 Cengage Learning 2005 ISBN 0155058991 Patrick Wyse Jackson The Chronologers Quest The Search for the Age of the Earth Cambridge University Press 2006 ISBN 1139457578 pp 127 8 General sources edit Hamblin W K The Earth s Dynamic Systems A Textbook in Physical Geology by W Kenneth Hamblin BYU Provo UT Illus William L Chesser Dennis Tasa Burgess Publishing Company Minneapolis Minnesota c 1978 pg 115 The Principle of Superposition and Original Horizontality pg 116 The Law of Faunal Succession The Principle of Crosscutting Relations pg 116 17 The Principle of Inclusion as in the Steno discussion above Principles of Archaeological Stratigraphy 40 figs 1 pl 136 pp London amp New York Academic Press ISBN 0 12 326650 5 Retrieved from https en wikipedia org w index php title Law of superposition amp oldid 1149019766, wikipedia, wiki, 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