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class="vector-toc-link" href="#Footnotes"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Footnotes</span> </div> </a> <ul id="toc-Footnotes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Further_reading" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Further_reading"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>Further reading</span> </div> </a> <ul id="toc-Further_reading-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Geological formation</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 39 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-39" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">39 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%AA%D9%83%D9%88%D9%8A%D9%86_%D8%AC%D9%8A%D9%88%D9%84%D9%88%D8%AC%D9%8A" title="تكوين جيولوجي – Arabic" lang="ar" hreflang="ar" data-title="تكوين جيولوجي" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/Formaci%C3%B3n_xeol%C3%B3xica" title="Formación xeolóxica – Asturian" lang="ast" hreflang="ast" data-title="Formación xeolóxica" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Formaci%C3%B3_geol%C3%B2gica" title="Formació geològica – Catalan" lang="ca" hreflang="ca" data-title="Formació geològica" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Souvrstv%C3%AD" title="Souvrství – Czech" lang="cs" hreflang="cs" data-title="Souvrství" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Formation_(geologi)" title="Formation (geologi) – Danish" lang="da" hreflang="da" data-title="Formation (geologi)" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Formation_(Geologie)" title="Formation (Geologie) – German" lang="de" hreflang="de" data-title="Formation (Geologie)" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Kihistu" title="Kihistu – Estonian" lang="et" hreflang="et" data-title="Kihistu" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%A3%CF%87%CE%B7%CE%BC%CE%B1%CF%84%CE%B9%CF%83%CE%BC%CF%8C%CF%82_(%CE%B3%CE%B5%CF%89%CE%BB%CE%BF%CE%B3%CE%AF%CE%B1)" title="Σχηματισμός (γεωλογία) – Greek" lang="el" hreflang="el" data-title="Σχηματισμός (γεωλογία)" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Formaci%C3%B3n_geol%C3%B3gica" title="Formación geológica – Spanish" lang="es" hreflang="es" data-title="Formación geológica" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Geologia_formacio" title="Geologia formacio – Esperanto" lang="eo" hreflang="eo" data-title="Geologia formacio" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Formazio_geologiko" title="Formazio geologiko – Basque" lang="eu" hreflang="eu" data-title="Formazio geologiko" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%B3%D8%A7%D8%B2%D9%86%D8%AF_%D8%B2%D9%85%DB%8C%D9%86%E2%80%8C%D8%B4%D9%86%D8%A7%D8%B3%DB%8C" title="سازند زمین‌شناسی – Persian" lang="fa" hreflang="fa" data-title="سازند زمین‌شناسی" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Formation_g%C3%A9ologique" title="Formation géologique – French" lang="fr" hreflang="fr" data-title="Formation géologique" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Formaci%C3%B3n_xeol%C3%B3xica" title="Formación xeolóxica – Galician" lang="gl" hreflang="gl" data-title="Formación xeolóxica" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EB%88%84%EC%B8%B5" title="누층 – Korean" lang="ko" hreflang="ko" data-title="누층" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%AD%E0%A5%82%E0%A4%B5%E0%A5%88%E0%A4%9C%E0%A5%8D%E0%A4%9E%E0%A4%BE%E0%A4%A8%E0%A4%BF%E0%A4%95_%E0%A4%B0%E0%A4%9A%E0%A4%A8%E0%A4%BE" title="भूवैज्ञानिक रचना – Hindi" lang="hi" hreflang="hi" data-title="भूवैज्ञानिक रचना" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Formasi_geologi" title="Formasi geologi – Indonesian" lang="id" hreflang="id" data-title="Formasi geologi" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Formazione_(stratigrafia)" title="Formazione (stratigrafia) – Italian" lang="it" hreflang="it" data-title="Formazione (stratigrafia)" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%AA%D7%A6%D7%95%D7%A8%D7%94_(%D7%92%D7%90%D7%95%D7%9C%D7%95%D7%92%D7%99%D7%94)" title="תצורה (גאולוגיה) – Hebrew" lang="he" hreflang="he" data-title="תצורה (גאולוגיה)" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%92%E1%83%94%E1%83%9D%E1%83%9A%E1%83%9D%E1%83%92%E1%83%98%E1%83%A3%E1%83%A0%E1%83%98_%E1%83%A4%E1%83%9D%E1%83%A0%E1%83%9B%E1%83%90%E1%83%AA%E1%83%98%E1%83%90" title="გეოლოგიური ფორმაცია – Georgian" lang="ka" hreflang="ka" data-title="გეოლოგიური ფორმაცია" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Form%C3%A1ci%C3%B3_(r%C3%A9tegtan)" title="Formáció (rétegtan) – Hungarian" lang="hu" hreflang="hu" data-title="Formáció (rétegtan)" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Formatie_(stratigrafie)" title="Formatie (stratigrafie) – Dutch" lang="nl" hreflang="nl" data-title="Formatie (stratigrafie)" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E5%B1%A4_(%E5%9C%B0%E8%B3%AA%E5%AD%A6)" title="層 (地質学) – Japanese" lang="ja" hreflang="ja" data-title="層 (地質学)" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Geologisk_formasjon" title="Geologisk formasjon – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Geologisk formasjon" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Formacja_(geologia)" title="Formacja (geologia) – Polish" lang="pl" hreflang="pl" data-title="Formacja (geologia)" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Forma%C3%A7%C3%A3o_geol%C3%B3gica" title="Formação geológica – Portuguese" lang="pt" hreflang="pt" data-title="Formação geológica" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%A4%D0%BE%D1%80%D0%BC%D0%B0%D1%86%D0%B8%D1%8F_(%D1%81%D1%82%D1%80%D0%B0%D1%82%D0%B8%D0%B3%D1%80%D0%B0%D1%84%D0%B8%D1%87%D0%B5%D1%81%D0%BA%D0%BE%D0%B5_%D0%BF%D0%BE%D0%B4%D1%80%D0%B0%D0%B7%D0%B4%D0%B5%D0%BB%D0%B5%D0%BD%D0%B8%D0%B5)" title="Формация (стратиграфическое подразделение) – Russian" lang="ru" hreflang="ru" data-title="Формация (стратиграфическое подразделение)" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Geological_formation" title="Geological formation – Simple English" lang="en-simple" hreflang="en-simple" data-title="Geological formation" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/S%C3%BAvrstvie" title="Súvrstvie – Slovak" lang="sk" hreflang="sk" data-title="Súvrstvie" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Geolo%C5%A1ka_formacija" title="Geološka formacija – Slovenian" lang="sl" hreflang="sl" data-title="Geološka formacija" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/Geolo%C5%A1ka_formacija" title="Geološka formacija – Serbian" lang="sr" hreflang="sr" data-title="Geološka formacija" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Muodostuma_(stratigrafia)" title="Muodostuma (stratigrafia) – Finnish" lang="fi" hreflang="fi" data-title="Muodostuma (stratigrafia)" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Formation_(geologi)" title="Formation (geologi) – Swedish" lang="sv" hreflang="sv" data-title="Formation (geologi)" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-tl mw-list-item"><a href="https://tl.wikipedia.org/wiki/Pagkakabuo_(stratigrapiya)" title="Pagkakabuo (stratigrapiya) – Tagalog" lang="tl" hreflang="tl" data-title="Pagkakabuo (stratigrapiya)" data-language-autonym="Tagalog" data-language-local-name="Tagalog" class="interlanguage-link-target"><span>Tagalog</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Jeolojik_yap%C4%B1" title="Jeolojik yapı – Turkish" lang="tr" hreflang="tr" data-title="Jeolojik yapı" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%93%D0%B5%D0%BE%D0%BB%D0%BE%D0%B3%D1%96%D1%87%D0%BD%D0%B0_%D1%84%D0%BE%D1%80%D0%BC%D0%B0%D1%86%D1%96%D1%8F" title="Геологічна формація – Ukrainian" lang="uk" hreflang="uk" data-title="Геологічна формація" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Th%C3%A0nh_h%E1%BB%87_%C4%91%E1%BB%8Ba_ch%E1%BA%A5t" title="Thành hệ địa chất – Vietnamese" lang="vi" hreflang="vi" data-title="Thành hệ địa chất" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/%E5%9C%B0%E8%B3%AA%E7%B5%84" title="地質組 – Cantonese" lang="yue" hreflang="yue" data-title="地質組" data-language-autonym="粵語" data-language-local-name="Cantonese" class="interlanguage-link-target"><span>粵語</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E7%BB%84_(%E5%9C%B0%E8%B4%A8%E5%AD%A6)" title="组 (地质学) – Chinese" lang="zh" hreflang="zh" data-title="组 (地质学)" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q736917#sitelinks-wikipedia" title="Edit interlanguage links" class="wbc-editpage">Edit links</a></span></div> </div> </div> </div> </header> <div class="vector-page-toolbar"> <div class="vector-page-toolbar-container"> <div id="left-navigation"> <nav aria-label="Namespaces"> <div id="p-associated-pages" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-associated-pages" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-nstab-main" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/Geological_formation" 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data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Fundamental unit of lithostratigraphy</div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Grand_Canyon_geologic_column.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/62/Grand_Canyon_geologic_column.jpg/220px-Grand_Canyon_geologic_column.jpg" decoding="async" width="220" height="307" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/62/Grand_Canyon_geologic_column.jpg/330px-Grand_Canyon_geologic_column.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/62/Grand_Canyon_geologic_column.jpg/440px-Grand_Canyon_geologic_column.jpg 2x" data-file-width="600" data-file-height="836" /></a><figcaption>A geologic <a href="/wiki/Cross_section_(geology)" title="Cross section (geology)">cross section</a> of the <a href="/wiki/Geology_of_the_Grand_Canyon_area" title="Geology of the Grand Canyon area">Grand Canyon</a>. Black numbers correspond to <a href="/wiki/Group_(stratigraphy)" title="Group (stratigraphy)">groups</a> of formations and white numbers correspond to formations (click on picture for more information)</figcaption></figure> <p>A <b>geological formation</b>, or simply <b>formation</b>, is a body of rock having a consistent set of physical characteristics (<a href="/wiki/Lithology" title="Lithology">lithology</a>) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the <a href="/wiki/Stratigraphic_column" title="Stratigraphic column">stratigraphic column</a>). It is the fundamental unit of <a href="/wiki/Lithostratigraphy" title="Lithostratigraphy">lithostratigraphy</a>, the study of <a href="/wiki/Strata" class="mw-redirect" title="Strata">strata</a> or rock layers.<sup id="cite_ref-FOOTNOTEBoggs1987545–547_1-0" class="reference"><a href="#cite_note-FOOTNOTEBoggs1987545–547-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051567–1569_2-0" class="reference"><a href="#cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051567–1569-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>A formation must be large enough that it can be mapped at the surface or traced in the subsurface. Formations are otherwise not defined by the <a href="/wiki/Thickness_(geology)" title="Thickness (geology)">thickness</a> of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock.<sup id="cite_ref-FOOTNOTEBoggs1987545–547_1-1" class="reference"><a href="#cite_note-FOOTNOTEBoggs1987545–547-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051567–1569_2-1" class="reference"><a href="#cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051567–1569-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>The concept of a geologic formation goes back to the beginnings of modern scientific geology. The term was used by <a href="/wiki/Abraham_Gottlob_Werner" title="Abraham Gottlob Werner">Abraham Gottlob Werner</a> in his theory of the origin of the Earth, which was developed over the period from 1774 to his death in 1817.<sup id="cite_ref-FOOTNOTEFrank1938221–222_3-0" class="reference"><a href="#cite_note-FOOTNOTEFrank1938221–222-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> The concept became increasingly formalized over time and is now codified in such works as the North American Stratigraphic Code and its counterparts in other regions.<sup id="cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature2005_4-0" class="reference"><a href="#cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature2005-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p><a href="/wiki/Geologic_map" title="Geologic map">Geologic maps</a> showing where various formations are exposed at the surface are fundamental to such fields as <a href="/wiki/Structural_geology" title="Structural geology">structural geology</a>, allowing geologists to infer the tectonic history of a region or predict likely locations for buried mineral resources.<sup id="cite_ref-FOOTNOTEGhosh1993_5-0" class="reference"><a href="#cite_note-FOOTNOTEGhosh1993-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Defining_formations">Defining formations</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geological_formation&action=edit&section=1" title="Edit section: Defining formations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:SEUtahStrat.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/66/SEUtahStrat.JPG/300px-SEUtahStrat.JPG" decoding="async" width="300" height="170" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/66/SEUtahStrat.JPG/450px-SEUtahStrat.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/66/SEUtahStrat.JPG/600px-SEUtahStrat.JPG 2x" data-file-width="3161" data-file-height="1794" /></a><figcaption>The <a href="/wiki/Permian" title="Permian">Permian</a> through <a href="/wiki/Jurassic" title="Jurassic">Jurassic</a> strata of the <a href="/wiki/Colorado_Plateau" title="Colorado Plateau">Colorado Plateau</a> area of southeastern <a href="/wiki/Utah" title="Utah">Utah</a> demonstrate the principles of <a href="/wiki/Stratigraphy" title="Stratigraphy">stratigraphy</a>. These strata make up much of the famous prominent rock formations in widely spaced protected areas such as <a href="/wiki/Capitol_Reef_National_Park" title="Capitol Reef National Park">Capitol Reef National Park</a> and <a href="/wiki/Canyonlands_National_Park" title="Canyonlands National Park">Canyonlands National Park</a>. From top to bottom: Rounded tan domes of the <a href="/wiki/Navajo_Sandstone" title="Navajo Sandstone">Navajo Sandstone</a>, layered red <a href="/wiki/Kayenta_Formation" title="Kayenta Formation">Kayenta Formation</a>, cliff-forming, vertically jointed, red <a href="/wiki/Wingate_Sandstone" title="Wingate Sandstone">Wingate Sandstone</a>, slope-forming, purplish <a href="/wiki/Chinle_Formation" title="Chinle Formation">Chinle Formation</a>, layered, lighter-red <a href="/wiki/Moenkopi_Formation" title="Moenkopi Formation">Moenkopi Formation</a>, and white, layered <a href="/wiki/Cutler_Formation" title="Cutler Formation">Cutler Formation</a> sandstone. Picture from <a href="/wiki/Glen_Canyon_National_Recreation_Area" title="Glen Canyon National Recreation Area">Glen Canyon National Recreation Area</a>, Utah.</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Uluru_(Helicopter_view)-crop.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Uluru_%28Helicopter_view%29-crop.jpg/220px-Uluru_%28Helicopter_view%29-crop.jpg" decoding="async" width="220" height="104" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Uluru_%28Helicopter_view%29-crop.jpg/330px-Uluru_%28Helicopter_view%29-crop.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Uluru_%28Helicopter_view%29-crop.jpg/440px-Uluru_%28Helicopter_view%29-crop.jpg 2x" data-file-width="2025" data-file-height="953" /></a><figcaption><a href="/wiki/Uluru" title="Uluru">Uluru</a> (Ayers Rock) in <a href="/wiki/Australia" title="Australia">Australia</a> is underlain by the Mutitjulu Arkose, a formation composed almost entirely of a single lithology (arkosic sandstone).</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Summerville_Formation.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Summerville_Formation.jpg/220px-Summerville_Formation.jpg" decoding="async" width="220" height="293" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Summerville_Formation.jpg/330px-Summerville_Formation.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Summerville_Formation.jpg/440px-Summerville_Formation.jpg 2x" data-file-width="3000" data-file-height="4000" /></a><figcaption>The <a href="/wiki/Summerville_Formation" title="Summerville Formation">Summerville Formation</a> is composed of alternating thin beds of two lithologies, mudstone and sandstone, penetrated by veins of a third lithology, gypsum.</figcaption></figure> <p>The boundaries of a formation are chosen to give it the greatest practical lithological consistency. Formations should not be defined by any criteria other than lithology. The lithology of a formation includes characteristics such as chemical and mineralogical composition, texture, color, primary <a href="/wiki/Sedimentary_structures" title="Sedimentary structures">depositional structures</a>, <a href="/wiki/Fossil" title="Fossil">fossils</a> regarded as rock-forming particles, or other organic materials such as <a href="/wiki/Coal" title="Coal">coal</a> or <a href="/wiki/Kerogen" title="Kerogen">kerogen</a>. The <a href="/wiki/Taxonomy_(biology)" title="Taxonomy (biology)">taxonomy</a> of fossils is <i>not</i> a valid lithological basis for defining a formation. <sup id="cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051567–1569_2-2" class="reference"><a href="#cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051567–1569-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>The contrast in lithology between formations required to justify their establishment varies with the complexity of the geology of a region. Formations must be able to be delineated at the scale of geologic mapping normally practiced in the region; the thickness of formations may range from less than a meter to several thousand meters.<sup id="cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051567–1569_2-3" class="reference"><a href="#cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051567–1569-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>Geologic formations are typically named after a permanent natural or artificial feature of the geographic area in which they were first described. The name consists of the geographic name plus either "Formation" or a descriptive name. Examples include the <a href="/wiki/Morrison_Formation" title="Morrison Formation">Morrison Formation</a>, named for the town of <a href="/wiki/Morrison,_Colorado" title="Morrison, Colorado">Morrison, Colorado</a>, and the <a href="/wiki/Kaibab_Limestone" title="Kaibab Limestone">Kaibab Limestone</a>, named after the <a href="/wiki/Kaibab_Plateau" title="Kaibab Plateau">Kaibab Plateau</a> of Arizona. The names must not duplicate previous formation names, so, for example, a newly designated formation could not be named the Kaibab Formation, since the Kaibab Limestone is already established as a formation name. The first use of a name has precedence over all others, as does the first name applied to a particular formation.<sup id="cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051561–1562_6-0" class="reference"><a href="#cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051561–1562-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>As with other stratigraphic units, the formal designation of a formation includes a <i><a href="/wiki/Stratotype" title="Stratotype">stratotype</a></i> which is usually a <i><a href="/wiki/Type_section" class="mw-redirect" title="Type section">type section</a>.</i> A type section is ideally a good exposure of the formation that shows its entire thickness. If the formation is nowhere entirely exposed, or if it shows considerably lateral variation, additional <i>reference sections</i> may be defined. Long-established formations dating to before the modern codification of stratigraphy, or which lack tabular form (such as volcanic formations), may substitute a type locality for a type section as their stratotype. The geologist defining the formation is expected to describe the stratotype in sufficient detail that other geologists can unequivocally recognize the formation.<sup id="cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051563_7-0" class="reference"><a href="#cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051563-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p><p>Although formations should not be defined by any criteria other than primary lithology, it is often useful to define <a href="/wiki/Geologic_unit" class="mw-redirect" title="Geologic unit">biostratigraphic units</a> on <a href="/wiki/Paleontology" title="Paleontology">paleontological</a> criteria, <a href="/wiki/Geologic_unit" class="mw-redirect" title="Geologic unit">chronostratigraphic units</a> on the age of the rocks, and <a href="/wiki/Geologic_unit" class="mw-redirect" title="Geologic unit">chemostratigraphic units</a> on geochemical criteria, and these are included in stratigraphic codes.<sup id="cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051553–1554_8-0" class="reference"><a href="#cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051553–1554-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Usefulness_of_formations">Usefulness of formations</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geological_formation&action=edit&section=2" title="Edit section: Usefulness of formations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The concept of formally defined layers or strata is central to the geologic discipline of <a href="/wiki/Stratigraphy" title="Stratigraphy">stratigraphy</a>, and the formation is the fundamental unit of stratigraphy. Formations may be combined into <a href="/wiki/Group_(stratigraphy)" title="Group (stratigraphy)">groups</a> of strata or divided into <a href="/wiki/Geological_unit#Member" class="mw-redirect" title="Geological unit">members</a>. Members differ from formations in that they need not be mappable at the same scale as formations, though they must be lithologically distinctive where present.<sup id="cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051569_9-0" class="reference"><a href="#cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051569-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> </p><p>The definition and recognition of formations allow <a href="/wiki/Geologist" title="Geologist">geologists</a> to correlate geologic strata across wide distances between <a href="/wiki/Outcrop" title="Outcrop">outcrops</a> and exposures of rock <a href="/wiki/Stratum" title="Stratum">strata</a>. Formations were at first described as the essential <a href="/wiki/Geologic_time" class="mw-redirect" title="Geologic time">geologic time</a> markers, based on their relative ages and the <a href="/wiki/Law_of_superposition" title="Law of superposition">law of superposition</a>. The divisions of the <a href="/wiki/Geological_time_scale" class="mw-redirect" title="Geological time scale">geological time scale</a> were described and put in chronological order by the geologists and stratigraphers of the 18th and 19th centuries.<sup id="cite_ref-FOOTNOTEFrank1938_10-0" class="reference"><a href="#cite_note-FOOTNOTEFrank1938-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p>Geologic formations can be usefully defined for <a href="/wiki/Sedimentary_rock" title="Sedimentary rock">sedimentary rock</a> layers, low-grade <a href="/wiki/Metamorphic_rocks" class="mw-redirect" title="Metamorphic rocks">metamorphic rocks</a>, and <a href="/wiki/Volcanic_rock" title="Volcanic rock">volcanic rocks</a>. Intrusive igneous rocks and highly metamorphosed rocks are generally not considered to be formations, but are described instead as <a href="/wiki/Lithodemic_unit" class="mw-redirect" title="Lithodemic unit">lithodemes</a>.<sup id="cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051570–1572_11-0" class="reference"><a href="#cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051570–1572-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Other_uses_of_the_term">Other uses of the term</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geological_formation&action=edit&section=3" title="Edit section: Other uses of the term"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>"Formation" is also used informally to describe the odd shapes (forms) that rocks acquire through erosional or depositional processes. Such a formation is abandoned when it is no longer affected by the geologic agent that produced it. Some well-known <a href="/wiki/Cave" title="Cave">cave</a> formations include <a href="/wiki/Stalactite" title="Stalactite">stalactites</a> and <a href="/wiki/Stalagmite" title="Stalagmite">stalagmites</a>. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geological_formation&action=edit&section=4" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Geochronology" title="Geochronology">Geochronology</a> – Science of determining the age of rocks, sediments and fossils</li> <li><a href="/wiki/List_of_rock_formations" title="List of rock formations">List of rock formations</a></li> <li><a href="/wiki/List_of_fossil_sites" title="List of fossil sites">List of fossil sites</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Footnotes">Footnotes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geological_formation&action=edit&section=5" title="Edit section: Footnotes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-FOOTNOTEBoggs1987545–547-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-FOOTNOTEBoggs1987545–547_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-FOOTNOTEBoggs1987545–547_1-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><a href="#CITEREFBoggs1987">Boggs 1987</a>, pp. 545–547.</span> </li> <li id="cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051567–1569-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051567–1569_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051567–1569_2-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051567–1569_2-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051567–1569_2-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><a href="#CITEREFNorth_American_Commission_on_Stratigraphic_Nomenclature2005">North American Commission on Stratigraphic Nomenclature 2005</a>, pp. 1567–1569.</span> </li> <li id="cite_note-FOOTNOTEFrank1938221–222-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTEFrank1938221–222_3-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFFrank1938">Frank 1938</a>, pp. 221–222.</span> </li> <li id="cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature2005-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature2005_4-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFNorth_American_Commission_on_Stratigraphic_Nomenclature2005">North American Commission on Stratigraphic Nomenclature 2005</a>.</span> </li> <li id="cite_note-FOOTNOTEGhosh1993-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTEGhosh1993_5-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFGhosh1993">Ghosh 1993</a>.</span> </li> <li id="cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051561–1562-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051561–1562_6-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFNorth_American_Commission_on_Stratigraphic_Nomenclature2005">North American Commission on Stratigraphic Nomenclature 2005</a>, pp. 1561–1562.</span> </li> <li id="cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051563-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051563_7-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFNorth_American_Commission_on_Stratigraphic_Nomenclature2005">North American Commission on Stratigraphic Nomenclature 2005</a>, p. 1563.</span> </li> <li id="cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051553–1554-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051553–1554_8-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFNorth_American_Commission_on_Stratigraphic_Nomenclature2005">North American Commission on Stratigraphic Nomenclature 2005</a>, pp. 1553–1554.</span> </li> <li id="cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051569-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051569_9-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFNorth_American_Commission_on_Stratigraphic_Nomenclature2005">North American Commission on Stratigraphic Nomenclature 2005</a>, pp. 1569.</span> </li> <li id="cite_note-FOOTNOTEFrank1938-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTEFrank1938_10-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFFrank1938">Frank 1938</a>.</span> </li> <li id="cite_note-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051570–1572-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTENorth_American_Commission_on_Stratigraphic_Nomenclature20051570–1572_11-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFNorth_American_Commission_on_Stratigraphic_Nomenclature2005">North American Commission on Stratigraphic Nomenclature 2005</a>, pp. 1570–1572.</span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geological_formation&action=edit&section=6" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFBoggs1987" class="citation book cs1">Boggs, Sam Jr. (1987). <i>Principles of sedimentology and stratigraphy</i> (1st ed.). Merrill Pub. Co. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0675204879" title="Special:BookSources/0675204879"><bdi>0675204879</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Principles+of+sedimentology+and+stratigraphy&rft.edition=1st&rft.pub=Merrill+Pub.+Co&rft.date=1987&rft.isbn=0675204879&rft.aulast=Boggs&rft.aufirst=Sam+Jr.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeological+formation" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFFrank1938" class="citation book cs1">Frank, Adams Dawson (1938). <a rel="nofollow" class="external text" href="https://archive.org/details/birthanddevelopm031745mbp"><i>The Birth and Development of the Geological Sciences</i></a>. Baltimore: The Williams & Wilkins Company.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Birth+and+Development+of+the+Geological+Sciences&rft.place=Baltimore&rft.pub=The+Williams+%26+Wilkins+Company&rft.date=1938&rft.aulast=Frank&rft.aufirst=Adams+Dawson&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fbirthanddevelopm031745mbp&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeological+formation" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNorth_American_Commission_on_Stratigraphic_Nomenclature2005" class="citation journal cs1">North American Commission on Stratigraphic Nomenclature (November 2005). <a rel="nofollow" class="external text" href="https://ngmdb.usgs.gov/Geolex/resources/docs/AAPG_Bull-89_NACSN-Code.pdf">"North American Stratigraphic Code"</a> <span class="cs1-format">(PDF)</span>. <i>AAPG Bulletin</i>. <b>89</b> (11): 1547–1591. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2005BAAPG..89.1547.">2005BAAPG..89.1547.</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1306%2F07050504129">10.1306/07050504129</a><span class="reference-accessdate">. Retrieved <span class="nowrap">8 August</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=AAPG+Bulletin&rft.atitle=North+American+Stratigraphic+Code&rft.volume=89&rft.issue=11&rft.pages=1547-1591&rft.date=2005-11&rft_id=info%3Adoi%2F10.1306%2F07050504129&rft_id=info%3Abibcode%2F2005BAAPG..89.1547.&rft.au=North+American+Commission+on+Stratigraphic+Nomenclature&rft_id=https%3A%2F%2Fngmdb.usgs.gov%2FGeolex%2Fresources%2Fdocs%2FAAPG_Bull-89_NACSN-Code.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeological+formation" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGhosh1993" class="citation book cs1">Ghosh, S.K. (1993). <i>Structural geology : fundamentals and modern developments</i> (1st ed.). Pergamon Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-08-041879-1" title="Special:BookSources/0-08-041879-1"><bdi>0-08-041879-1</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Structural+geology+%3A+fundamentals+and+modern+developments&rft.edition=1st&rft.pub=Pergamon+Press&rft.date=1993&rft.isbn=0-08-041879-1&rft.aulast=Ghosh&rft.aufirst=S.K.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeological+formation" class="Z3988"></span></li></ul> <div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geological_formation&action=edit&section=7" title="Edit section: Further reading"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239549316">.mw-parser-output .refbegin{margin-bottom:0.5em}.mw-parser-output .refbegin-hanging-indents>ul{margin-left:0}.mw-parser-output .refbegin-hanging-indents>ul>li{margin-left:0;padding-left:3.2em;text-indent:-3.2em}.mw-parser-output .refbegin-hanging-indents ul,.mw-parser-output .refbegin-hanging-indents ul li{list-style:none}@media(max-width:720px){.mw-parser-output .refbegin-hanging-indents>ul>li{padding-left:1.6em;text-indent:-1.6em}}.mw-parser-output .refbegin-columns{margin-top:0.3em}.mw-parser-output .refbegin-columns ul{margin-top:0}.mw-parser-output .refbegin-columns li{page-break-inside:avoid;break-inside:avoid-column}@media screen{.mw-parser-output .refbegin{font-size:90%}}</style><div class="refbegin" style=""> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBrookfield2008" class="citation book cs1">Brookfield, Michael E. (2008). <i>Principles of Stratigraphy</i>. John Wiley & Sons. pp. 111–114, 200. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9780470693223" title="Special:BookSources/9780470693223"><bdi>9780470693223</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Principles+of+Stratigraphy&rft.pages=111-114%2C+200&rft.pub=John+Wiley+%26+Sons&rft.date=2008&rft.isbn=9780470693223&rft.aulast=Brookfield&rft.aufirst=Michael+E.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeological+formation" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFReySimone_Galeotti2008" class="citation book cs1">Rey, Jacques; Simone Galeotti, eds. (2008). <i>Stratigraphy : terminology and practice</i>. Paris, France: Editions OPHRYS. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9782710809104" title="Special:BookSources/9782710809104"><bdi>9782710809104</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Stratigraphy+%3A+terminology+and+practice&rft.place=Paris%2C+France&rft.pub=Editions+OPHRYS&rft.date=2008&rft.isbn=9782710809104&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGeological+formation" class="Z3988"></span></li></ul> </div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Geological_formation&action=edit&section=8" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Commons-logo.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/12px-Commons-logo.svg.png" decoding="async" width="12" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/18px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/24px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /></a></span> Media related to <a href="https://commons.wikimedia.org/wiki/Category:Geologic_formations" class="extiw" title="commons:Category:Geologic formations">Geologic formations</a> at Wikimedia Commons</li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist 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