# Lithostratigraphy > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Lithostratigraphy > Markdown URL: https://mediated.wiki/source/Lithostratigraphy.md > Source: https://en.wikipedia.org/wiki/Lithostratigraphy > Source revision: 1325981247 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|Sub-discipline of stratigraphy}} {{More citations needed|date=January 2017}} [[Image:SEUtahStrat.JPG|thumb|upright=1.3|The [Permian](/source/Permian) through [Jurassic](/source/Jurassic) lithostratigraphy of the [Colorado Plateau](/source/Colorado_Plateau) area of southeastern [Utah](/source/Utah) that makes up much of the famous prominent rock formations in protected areas such as [Capitol Reef National Park](/source/Capitol_Reef_National_Park) and [Canyonlands National Park](/source/Canyonlands_National_Park). From top to bottom: Rounded tan domes of the [Navajo Sandstone](/source/Navajo_Sandstone), layered red [Kayenta Formation](/source/Kayenta_Formation), cliff-forming, vertically jointed, red [Wingate Sandstone](/source/Wingate_Sandstone), slope-forming, purplish [Chinle Formation](/source/Chinle_Formation), layered, lighter-red [Moenkopi Formation](/source/Moenkopi_Formation), and white, layered [Cutler Formation](/source/Cutler_Formation) sandstone. Picture from [Glen Canyon National Recreation Area](/source/Glen_Canyon_National_Recreation_Area), Utah.]] [[Image:Quebrada de Cafayate, Salta (Argentina).jpg|upright=1.3|thumb|Strata in [Salta](/source/Salta_province), Argentina]] '''Lithostratigraphy''' is a sub-discipline of [stratigraphy](/source/stratigraphy), the [geological](/source/geology) [science](/source/science) associated with the study of [strata](/source/stratum) or rock layers. Major focuses include [geochronology](/source/geochronology), comparative geology, and [petrology](/source/petrology). In general, strata are primarily [igneous](/source/igneous) or [sedimentary](/source/sedimentary) relating to how the rock was formed. [Sedimentary](/source/Sedimentary_rock) layers are laid down by [deposition](/source/Deposition_(sediment)) of [sediment](/source/sediment) associated with [weathering](/source/weathering) processes, decaying organic matter (biogenic) or through chemical precipitation. These layers are often distinguishable as having many [fossils](/source/fossils) and are important for the study of [biostratigraphy](/source/biostratigraphy). Igneous layers occur as stacks of lava flows, layers of lava fragments (called [tephra](/source/tephra)) both erupted onto the Earth's surface by volcanoes, and in [layered intrusion](/source/layered_intrusion)s formed deep underground. Igneous layers are generally devoid of fossils and represent [magmatic](/source/Magmatism) or [volcanic activity](/source/volcanic_activity) that occurred during the geologic history of an area. There are a number of principles that are used to explain relationships between strata. When an igneous rock cuts across a formation of sedimentary rock, then we can say that the igneous intrusion is younger than the sedimentary rock. [The principle of superposition](/source/Law_of_superposition) states that a sedimentary rock layer in a tectonically undisturbed stratum is younger than the one beneath and older than the one above it. The [principle of original horizontality](/source/principle_of_original_horizontality) states that the deposition of sediments occurs as essentially horizontal beds. == Types of lithostratigraphic units == The principles of lithostratigraphy were first established by the Danish naturalist, [Nicolas Steno](/source/Nicolas_Steno), in his 1669 ''Dissertationis prodromus''.{{sfn|Steno|1916}} A lithostratigraphic unit conforms to the [law of superposition](/source/law_of_superposition), which in its modern form states that in any succession of [strata](/source/Stratum), not disturbed or overturned since [deposition](/source/Deposition_(geology)), younger rocks lies above older rocks.{{sfn|Boggs|2006|p=399}} The [principle of lateral continuity](/source/principle_of_lateral_continuity) states that a set of bed extends and can be traceable over a large area.{{sfn|Brookfield|2004|p=116}} Lithostratigraphic units are recognized and defined on the basis of observable physical rock characteristics. The [lithology](/source/lithology) of a unit includes characteristics such as chemical and mineralogical composition, texture, color, primary [depositional structures](/source/Sedimentary_structures), [fossil](/source/fossil)s regarded as rock-forming particles, or other organic materials such as [coal](/source/coal) or [kerogen](/source/kerogen). The [taxonomy](/source/Taxonomy_(biology)) of fossils is ''not'' a valid lithological basis for defining a lithostratigraphic unit. The descriptions of strata based on physical appearance define [facies](/source/facies).{{sfn|North American Commission on Stratigraphic Nomenclature|2005|pp=1547–1591}} The formal description of a lithostratigraphic unit includes a ''[stratotype](/source/stratotype)'' which is usually a ''[type section](/source/type_section).'' A type section is ideally a good exposure of the unit that shows its entire thickness. If the unit is nowhere entirely exposed, or if it shows considerably lateral variation, additional ''reference sections'' may be defined. Long-established lithostratigraphic units dating to before the modern codification of stratigraphy, or which lack tabular form (such as volcanic domes), may substitute a type locality for a type section as their stratotype. The geologist defining the unit is expected to describe the stratotype in sufficient detail that other geologists can unequivocally recognize the unit.{{sfn|North American Commission on Stratigraphic Nomenclature|2005|pp=1563}} '''''Lithosome''''': Masses of rock of essentially uniform character and having interchanging relationships with adjacent masses of different [lithology](/source/lithology). e.g.: [shale](/source/shale) lithosome, [limestone](/source/limestone) lithosome. The fundamental Lithostratigraphic unit is the [formation](/source/Formation_(stratigraphy)). A formation is a lithologically distinctive [stratigraphic unit](/source/stratigraphic_unit) that is large enough to be mappable and traceable. Formations may be subdivided into members and beds and aggregated with other formations into groups and supergroups. {{Further|topic=these hierarchical Lithostratigraphic divisions as stratigraphic units|Stratigraphic unit#Lithostratigraphic units}} == Stratigraphic relationship == thumb|Diagrams showing stratigraphic relations: A: an angular unconformity; B: a disconformity; C: a nonconformity. [[Image:EdwardsDisconformity.jpg|thumb|[Disconformity](/source/Disconformity) with the Lower Cretaceous Edwards Formation overlying a Lower Permian limestone; hiatus is about 165 million years; Texas.]] Two types of contact: ''conformable'' and ''unconformable''. ''Conformable'': unbroken deposition, no break or hiatus (break or interruption in the continuity of the geological record). The surface strata resulting is called a ''conformity''. Two types of contact between conformable strata: ''abrupt contacts'' (directly separate beds of distinctly different lithology, minor depositional break, called ''[diastem](/source/diastem)s'') and ''gradational contact'' (gradual change in deposition, mixing zone). ''Unconformable'': period of erosion/non-deposition. The surface stratum resulting is called an [unconformity](/source/unconformity). Four types of unconformity: *''Angular unconformity'': younger sediment lies upon an eroded surface of tilted or folded older rocks. The older rock [dips](/source/Strike_and_dip) at a different angle from the younger. *''Disconformity'': the contact between younger and older beds is marked by visible, irregular [erosional surfaces](/source/erosion_surface). [Paleosol](/source/Paleosol) might develop right above the disconformity surface because of the non-deposition setting. *''Paraconformity'': the bedding planes below and above the unconformity are parallel. A time gap is present, as shown by a faunal break, but there is no erosion, just a period of non-deposition. *''Nonconformity'': relatively young sediments are deposited right above older [igneous](/source/Igneous_rock) or [metamorphic rock](/source/metamorphic_rock)s. == Lithostratigraphic correlation == To correlate lithostratigraphic units, geologists define facies, and look for key beds or key sequences that can be used as a datum. * Direct correlation: based on lithology, color, structure, thickness... * Indirect correlation: electric log correlation (gamma-ray, density, resistivity...){{sfn|Olea|Sampson|2003}} thumb|alt=Correlation scheme|(A) Correlation scheme indicates which layers penetrated at different locations belong to the same body Geological correlation{{CN|date=November 2023}} is the main tool for reconstructing the geometry of layering in [sedimentary basins](/source/sedimentary_basins). The lithological correlation is a procedure, decisive what [layers](/source/strata) (strata) in geological cross-sections located in different places belong to the same geological body now (or belonged in the past).{{sfn|Voronin|1973}} The identification is based on comparison of physical and mineralogical characteristics of the rocks, and on general assumptions known as the [Steno's](/source/Nicolas_Steno) principles:{{cite web |title=Steno's Principles of Stratigraphy |url=http://www.geologyin.com/2014/03/stenos-principles-of-stratigraphy.html |website=Geology In |language=en |access-date=2019-11-29 |archive-date=2021-09-17 |archive-url=https://web.archive.org/web/20210917200513/http://www.geologyin.com/2014/03/stenos-principles-of-stratigraphy.html |url-status=live }} 1. The sedimentary strata occurred sequentially in time: the youngest at the top.
2. The strata are originally horizontal.
3. The stratum extends in all directions until it thins out or encounters a barrier. The results are presented as a correlation scheme (A). Practical correlation has a lot of difficulties: fuzzy borders of the layers, variations in composition and structure of the rocks in the layer, [unconformities](/source/unconformities) in the sequence of layers, etc. This is why errors in correlation schemes are not seldom. When the distances between available cross-sections are decreasing (for example, by drilling new wells) the quality of correlation is improving, but meanwhile the wrong geological decisions could be made that increases the expenses of geological projects. ==Lithodemic stratigraphy== {{anchor|Lithodeme}} The law of superposition is inapplicable to intrusive, highly deformed, or metamorphic bodies of rock lacking discernible stratification. Such bodies of rock are described as ''lithodemic'' and are determined and delimited based on rock characteristics. The 1983 North American Stratigraphic Code adopted the formal terms '''lithodeme''', which is comparable to a formation; a ''suite'', which is analogous to a group, and a ''supersuite'', similar to a supergroup. A lithodeme is the fundamental unit and should possess distinctive and consistent lithological features, comprising a single rock type or a mixture of two or more types that distinguishes the unit from those around it. As with formations, a lithodemic unit is given a geographical name combined with either a rock name or some term describing its form. The term ''suite'' is deprecated. Also formalized is the term ''[complex](/source/Complex_(geology))'', which applies to a body of rock of two or more genetic classes (sedimentary, metamorphic, or igneous). This establishes two hierarchies of lithodemic units:{{sfn|Subcommission on Quaternary Stratigraphy|2002}} {| class="wikitable" |- | Supersuite || Supercomplex |- | Suite || Complex |- | Lithodeme || (no equivalent) |} Similar rules have been adopted in Sweden.{{sfn|Kumpulainen|2016}} However, the 1994 International Stratigraphic Guide regards plutons and non-layered metamorphic rocks of undetermined origin as special cases within lithostratigraphy.{{sfn|Subcommission on Quaternary Stratigraphy|2002}} ==See also== * [Biostratigraphy](/source/Biostratigraphy) * [Chronostratigraphy](/source/Chronostratigraphy) * [Topostratigraphy](/source/Topostratigraphy) *[Earth science](/source/Earth_science) == Footnotes == {{Reflist}} == References == * {{cite book |last1=Boggs |first1=Sam |title=Principles of sedimentology and stratigraphy |date=2006 |publisher=Pearson Prentice Hall |location=Upper Saddle River, N.J. |isbn=0131547283 |edition=4th}} * *{{cite book|last=Brookfield|first=Michael E.|title=Principles of stratigraphy|year=2004|publisher=Blackwell Publ.|location=Malden, Mass.|isbn=978-1-4051-1164-5|url=https://books.google.com/books?id=Ecgdvth9EjkC|access-date=12 November 2014}} * {{cite journal |last1=Kumpulainen |first1=Risto A. |title=Guide for geological nomenclature in Sweden |journal=GFF |date=17 October 2016 |volume=139 |issue=1 |pages=3–20 |doi=10.1080/11035897.2016.1178666|doi-access=free }} * {{cite journal |author=North American Commission on Stratigraphic Nomenclature |title=North American Stratigraphic Code |journal=AAPG Bulletin |date=November 2005 |volume=89 |issue=11 |pages=1547–1591 |doi=10.1306/07050504129 |bibcode=2005BAAPG..89.1547. |url=https://ngmdb.usgs.gov/Geolex/resources/docs/AAPG_Bull-89_NACSN-Code.pdf |access-date=8 August 2020}} * {{cite web |last1=Olea |first1=Ricardo A. |last2=Sampson |first2=Robert J. |year=2003 |title=CORRELATOR, an interactive computer program for high-resolution, lithostratigraphic, well-log correlation. |url=http://www.kgs.ku.edu/Publications/OFR/2002/OFR02_51/ManualOFR2002-51.pdf |access-date=1 November 2020}} * {{cite book|last=Steno|first=Nicolas|translator-last1=Winter|translator-first1=John|title=Nicolas Steno's Dissertation Concerning a Solid Body Enclosed by Process of Nature within a Solid: An English Version with an Introduction and Explanatory Notes|date=1916|orig-year=1669|url=https://archive.org/details/cu31924012131458|publisher=New York, The Macmillan company; London, Macmillan and company, limited}} * {{cite web |last1=Subcommission on Quaternary Stratigraphy |title=Lithodemic stratigraphy |url=http://quaternary.stratigraphy.org/stratigraphic-guide/lithodemic-stratigraphy/ |access-date=10 May 2020 |year=2002}} * {{cite book |last1=Voronin |first1=Y.A. |title=Methodological issues of application of mathematical methods and computers in geology |publisher=The Computer Center, Siberian Division of the USSR Academy of Sciences |location=Novosibirsk, Yakutsk |year=1973}} ==External links== * [https://web.archive.org/web/20080821075310/http://www.bslsonline.com/ Online stratigraphic column generator] * [http://www-odp.tamu.edu/publications/208_IR/chap_02/c2_4.htm Tamu.edu: Lithostratigraphy] * [https://www.usgs.gov/science/science.php?term=668 USGS.gov: Lithostratigraphy] * [http://www.agenames.org Agenames] {{Authority control}} Category:Lithostratigraphy Category:Geochronological dating methods Category:Petrology Category:Stratigraphy --- Adapted from the Wikipedia article [Lithostratigraphy](https://en.wikipedia.org/wiki/Lithostratigraphy) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Lithostratigraphy?action=history)). 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