{{Carboniferous European subdivisions}} The '''Westphalian''' is a regional stage or age in the regional stratigraphy of northwest Europe, with an age between roughly 315<ref name=":9">{{Cite web |last1=Cohen |first1=K. M. |last2=Finney |first2=S. C. |last3=Gibbard |first3=P. L. |last4=Fan |first4=J X. |date=2023 |title=International chronostratigraphic chart. |url=https://stratigraphy.org/chart |website=www.stratigraphy.org}}</ref><ref name=":3">{{Cite journal |last1=Opluštil |first1=Stanislav |last2=Laurin |first2=Jiří |last3=Hýlová |first3=Lada |last4=Jirásek |first4=Jakub |last5=Schmitz |first5=Mark |last6=Sivek |first6=Martin |date=2022-05-01 |title=Coal-bearing fluvial cycles of the late Paleozoic tropics; astronomical control on sediment supply constrained by high-precision radioisotopic ages, Upper Silesian Basin |url=https://www.sciencedirect.com/science/article/pii/S0012825222000824 |journal=Earth-Science Reviews |volume=228 |article-number=103998 |doi=10.1016/j.earscirev.2022.103998 |bibcode=2022ESRv..22803998O |issn=0012-8252|url-access=subscription }}</ref> and 307<ref name=":9" /><ref name=":2" /> Ma (million years ago). It is a subdivision of the Carboniferous System or Period and the regional Silesian Series. The Westphalian is named for the region of Westphalia (German: ''Westfalen'') in western Germany where strata of this age occur. The Coal Measures of England and Wales are also largely of Westphalian age, though they also extend into the succeeding Stephanian.
The Westphalian is preceded by the Namurian Stage/Age (which corresponds to the Millstone Grit Series of Great Britain) and succeeded by the Stephanian Stage/Age (which corresponds to the uppermost part of the Coal Measures of Great Britain).
In the official geologic time scale of the International Commission on Stratigraphy (ICS<ref name=":9" />), the Westphalian is placed within the Pennsylvanian Subsystem/Subperiod (323-299 Ma) of the Carboniferous System/Period. As a regionally defined stage, the Westphalian overlaps with official ICS stages which are in use on an international level. The Westphalian extends from the approximately the upper half of the Bashkirian Stage through the Moscovian Stage,<ref name=":1" /> and possibly includes a small portion of the Kasimovian Stage.<ref name=":5" /> Many older scientific sources refer to the Westphalian as an epoch or series, which are higher geological ranks than its current status.
== Stratigraphy == Since 1935, the Westphalian has been split into four substages, from oldest to youngest: Langsettian (Westphalian A), Duckmantian (Westphalian B), Bolsovian (Westphalian C), and "Asturian" (Westphalian D). These substages are defined by guide fossils, or "index fossils," particularly plant macrofossils, miospores, and ammonoids.<ref name=":0">{{Citation |last=Waters |first=C.N. |title=Definitions of chronostratigraphic subdivisions: geochronology and event stratigraphy |date=2011-07-13 |url=https://pubs.geoscienceworld.org/books/book/1774/chapter/107660806 |work=A Revised Correlation of Carboniferous Rocks in the British Isles |pages=3–10 |editor-last=Waters |editor-first=C.N. |access-date=2023-10-09 |edition=First |publisher=The Geological Society of London |language=en |doi=10.1144/sr26.2 |isbn=978-1-86239-694-4 |editor2-last=Somerville |editor2-first=I.D. |editor3-last=Jones |editor3-first=N.S. |editor4-last=Cleal |editor4-first=C.J.|url-access=subscription }}</ref><ref name=":8">{{Citation |last1=Waters |first1=C.N. |title=Biostratigraphy |date=2011-07-13 |url=https://pubs.geoscienceworld.org/books/book/1774/chapter/107660861 |work=A Revised Correlation of Carboniferous Rocks in the British Isles |pages=11–22 |editor-last=Waters |editor-first=C.N. |access-date=2023-10-09 |edition=First |publisher=The Geological Society of London |language=en |doi=10.1144/sr26.3 |isbn=978-1-86239-694-4 |last2=Somerville |first2=I.D. |last3=Stephenson |first3=M.H. |last4=Cleal |first4=C.J. |last5=Long |first5=S.L. |editor2-last=Somerville |editor2-first=I.D. |editor3-last=Jones |editor3-first=N.S. |editor4-last=Cleal |editor4-first=C.J.|url-access=subscription }}</ref><ref name=":1">{{Citation |last1=Aretz |first1=M. |title=The Carboniferous Period |date=2020 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780128243602000231 |work=Geologic Time Scale 2020 |pages=811–874 |access-date=2023-10-09 |publisher=Elsevier |language=en |doi=10.1016/b978-0-12-824360-2.00023-1 |isbn=978-0-12-824360-2 |last2=Herbig |first2=H.G. |last3=Wang |first3=X.D. |last4=Gradstein |first4=F.M. |last5=Agterberg |first5=F.P. |last6=Ogg |first6=J.G.|url-access=subscription }}</ref> The Westphalian exhibits distinctive changes in plant diversity, and many plant macrofossil assemblage zones have been defined across an area encompassing Europe, Turkey, and the Maritime Provinces of Canada.<ref name=":6">{{Cite journal |last1=Opluštil |first1=Stanislav |last2=Cleal |first2=Christopher J. |last3=Wang |first3=Jun |last4=Wan |first4=Mingli |date=2022 |title=Carboniferous macrofloral biostratigraphy: an overview |url=https://www.lyellcollection.org/doi/10.1144/SP512-2020-97 |journal=Geological Society, London, Special Publications |language=en |volume=512 |issue=1 |pages=813–863 |doi=10.1144/SP512-2020-97 |bibcode=2022GSLSP.512..813O |issn=0305-8719|url-access=subscription }}</ref>
=== Langsettian === The '''Langsettian''', previously known as '''Westphalian A''', is named after the village of Langsett in South Yorkshire, England. It marks the base of the Westphalian regional stage, as defined by the ammonoid ''Gastrioceras subcrenatum''.<ref name=":0" /> The base of the Langsettian (and the Westphalian as a whole) has been dated to around 319.9<ref name=":4">{{Cite journal |last1=Pointon |first1=Michael A. |last2=Chew |first2=David M. |last3=Ovtcharova |first3=Maria |last4=Sevastopulo |first4=George D. |last5=Crowley |first5=Quentin G. |date=2012 |title=New high-precision U–Pb dates from western European Carboniferous tuffs; implications for time scale calibration, the periodicity of late Carboniferous cycles and stratigraphical correlation |url=https://www.lyellcollection.org/doi/10.1144/jgs2011-092 |journal=Journal of the Geological Society |language=en |volume=169 |issue=6 |pages=713–721 |doi=10.1144/jgs2011-092 |bibcode=2012JGSoc.169..713P |issn=0016-7649|hdl=2262/79149 |hdl-access=free }}</ref> or 319.2<ref name=":3" /> Ma.
The Langsettian corresponds to the ''Calymmotheca ("Lyginopteris") hoeninghausii'' assemblage zone.<ref name=":6" /> Many widespread plant species first appear near the base of the Langsettian, indicating a spike of diversification in tropical coal swamp habitats.<ref name=":6" /><ref name=":7">{{Cite journal |last1=Molina-Solís |first1=Azucena |last2=Cleal |first2=Christopher J. |last3=Capel |first3=Eliott |last4=Cascales-Miñana |first4=Borja |date=2023 |title=Vegetation dynamics in the Early–Middle Pennsylvanian coal swamps of the Nord-Pas-de-Calais Coalfield, France |url=https://linkinghub.elsevier.com/retrieve/pii/S1871174X2300046X |journal=Palaeoworld |volume=33 |issue=2 |pages=328–340 |language=en |doi=10.1016/j.palwor.2023.04.005}}</ref> Plant diversity steadily increases through the entire Langsettian, though this may be a result of ecological factors such as the receding coastline.<ref name=":6" />
=== Duckmantian === The '''Duckmantian''', previously known as '''Westphalian B''', is named after the village of Duckmanton in Derbyshire, England. The base of the Duckmantian is defined by the ammonoid ''Anthracoceratites vaderbeckei''.<ref name=":0" /> The boundary between the global Bashkirian and Moscovian stages (~315.2 Ma)<ref name=":1" /> corresponds to the mid-late part of the Duckmantian.<ref name=":4" /><ref name=":1" />
The lower-middle part of the Duckmantian corresponds to the ''Lonchopteris rugosa'' Assemblage-zone, the most diverse plant biozone in the Carboniferous coalfields of Europe. The rising diversity trend of the Langsettian continues into this biozone, with few notable changes in species composition. In the majority of European coalfields, plant diversity reached a plateau around halfway through the Duckmantian. Coal swamps became increasingly unstable in the ''Paripteris linguaefolia'' assemblage zone, which begins in the upper part of the Duckmantian.<ref name=":6" /><ref name=":7" />
=== Bolsovian === The '''Bolsovian''', previously known as '''Westphalian C''', is named after the town of Bolsover in Derbyshire. The base of the Bolsovian is defined by the ammonoid ''Donetzoceras aegiranum'',<ref name=":0" /> and has an estimated age of around 313.8<ref name=":4" /> or 313.7<ref name=":5">{{Cite journal |last1=Opluštil |first1=Stanislav |last2=Schmitz |first2=Mark |last3=Cleal |first3=Christopher J. |last4=Martínek |first4=Karel |date=2016 |title=A review of the Middle–Late Pennsylvanian west European regional substages and floral biozones, and their correlation to the Geological Time Scale based on new U–Pb ages |url=https://linkinghub.elsevier.com/retrieve/pii/S0012825216300046 |journal=Earth-Science Reviews |language=en |volume=154 |pages=301–335 |doi=10.1016/j.earscirev.2016.01.004|bibcode=2016ESRv..154..301O |url-access=subscription }}</ref> Ma.
The ''Paripteris linguaefolia'' assemblage zone continues into the Bolsovian, and a decline in plant diversity is apparent across the entirety of Europe.<ref name=":6" /> In a few coalfields, such as the Nord-Pas-des-Calais basin of northern France, the decline is delayed until the mid-Bolsovian, while in other areas it may begin as early as the late Duckmantian. The overall downward diversity trend is slight, but several notable lycopsid and sphenopsid species disappear from European coal swamps at this time.<ref name=":7" />
=== Westphalian D === '''Westphalian D''' is often referred to as the '''Asturian''', named after the Asturias region of northwest Spain.<ref>{{Cite journal |last1=Wagner |first1=R.H. |last2=Sánchez de Posada |first2=L.C. |last3=Martínez Chacón |first3=M.L. |last4=Fernández |first4=L.P. |last5=Villa |first5=E. |last6=Winkler Prins |first6=C.F. |date=2002 |title=The Asturian Stage: a preliminary proposal for the definition of a substitute for Westphalian D |journal=Canadian Society of Petroleum Geologists, Memoir |volume=19 |pages=832–850}}</ref> In most of Europe, Westphalian D is distinguished by plant fossils. Asturias is one of the few European regions with enough late Westphalian marine fossils to allow for precise correlations with other marine strata. The proposal to fully implement the name "Asturian" has yet to be ratified, as some stratigraphic difficulties in Spain are not fully resolved.<ref name=":1" /><ref name=":2">{{Cite journal |last1=Knight |first1=John A. |last2=Cleal |first2=Christopher J. |last3=Álvarez-Vázquez |first3=Carmen |date=2023-06-14 |title=The challenge of relating the Kasimovian to west European chronostratigraphy: a critical review of the Cantabrian and Barruelian substages of the Stephanian Stage |journal=Geological Society, London, Special Publications |language=en |volume=535 |issue=1 |pages=31–71 |doi=10.1144/SP535-2022-189 |issn=0305-8719|doi-access=free |bibcode=2023GSLSP.535..189K }}</ref>
The lower part of the Asturian belongs to the ''Linopteris obliqua'' assemblage zone<ref name=":6" /> (sometimes termed the ''Linopteris bunburii'' zone).<ref name=":5" /> This biozone is notably lower in diversity than previous Westphalian biozones. Plant fossils are still common over much of Europe, with ''Neuropteris ovata'' as a particularly abundant species.<ref name=":6" /> An important ecological turnover occurs about halfway through the Asturian (~309 Ma),<ref name=":5" /> with the arrival of the ''Crenulopteris acadica'' assemblage zone<ref>{{Cite journal |last1=Wittry |first1=Jack |last2=Glasspool |first2=Ian J. |last3=Béthoux |first3=Olivier |last4=Koll |first4=Rebecca |last5=Cleal |first5=Christopher J. |date=2015-08-03 |title=A revision of the Pennsylvanian marattialean fern Lobatopteris vestita auct . and related species |url=http://www.tandfonline.com/doi/full/10.1080/14772019.2014.936915 |journal=Journal of Systematic Palaeontology |language=en |volume=13 |issue=8 |pages=615–643 |doi=10.1080/14772019.2014.936915 |bibcode=2015JSPal..13..615W |issn=1477-2019|url-access=subscription }}</ref><ref name=":5" /><ref name=":6" /><ref name=":7" /> (previously known as the ''Lobatopteris vestita'' zone).<ref name=":8" /> Lycopsid fossils become very rare, while marattialean ferns become abundant in coal swamp deposits.<ref name=":6" /> Many European coalfields were positioned in a foreland basin north of the Variscan orogeny. As mountain-building continued, uplift accelerated in the basin, endangering the survival of coal swamp environments.<ref name=":6" /><ref name=":7" />
Plant fossils (and coal deposits as a whole) are uncommon in the following "Cantabrian" substage of the Stephanian Stage.<ref name=":2" /> The end of the Asturian is a topic of strong debate; most estimates place the Westphalian-Stephanian boundary before the start of the Kasimovian global stage (~307 Ma),<ref name=":0" /><ref name=":1" /><ref name=":2" /> whereas a few place the boundary within the Kasimovian.<ref name=":5" /> U-Pb radiometric dating of tonstein beds in Spain estimate that the Asturian lasted from 310.7 to 307.5 Ma, ending just prior to the Kasimovian.<ref name=":2" />
==Life== The Westphalian interval is widely recognized for its coal deposits—rocks that were deposited broadly across regions that were in low paleolatitudes. These deposits, from so-called "coal swamps" have yielded rich assemblages of fossils including spore-bearing and seed-bearing plants, fishes, and tetrapods.<ref>{{Cite journal |last1=Hook |first1=R. W. |last2=Ferm |first2=J. C. |date=1985 |title=A depositional model for the Linton tetrapod assemblage (Westphalian D, Upper Carboniferous) and its palaeonenvironmental significance. |journal=Philosophical Transactions of the Royal Society of London |volume=B 311 |issue=1148 |pages=101–108}}</ref><ref>{{Cite journal |last1=Hook |first1=R. W. |last2=Baird |first2=D. |date=1986 |title=The Diamond Coal Mine of Linton, Ohio, and its Pennsylvanian-age vertebrates. |journal=Journal of Vertebrate Paleontology |volume=6 |issue=2 |pages=174–190|doi=10.1080/02724634.1986.10011609 |bibcode=1986JVPal...6..174H }}</ref><ref>{{Cite journal |last=Babcock |first=L. E. |date=2024 |title=Replacement names for two species of Orthacanthus Agassiz, 1843 (Chondrichthyes, Xenacanthiformes), and discussion of Giebelodus Whitley, 1940, replacement name for Chilodus Giebel, 1848 (Chondrichthyes, Xenacanthiformes), preoccupied by Chilodus Müller & Troschel, 1844 (Actinopterygii, Characiformes). |journal=ZooKeys |issue=1188 |pages=219–226|doi=10.3897/zookeys.1188.108571 |doi-access=free |pmc=10790574 }}</ref> Amphibians were diverse and dominated some communities. The collapse of the rainforest ecology between the Moscovian and Kasimovian removed many amphibian species that did not survive as well in the cooler, drier conditions. Reptiles, however prospered due to specific key adaptations and underwent a major evolutionary radiation, in response to the drier climate that led to the rainforest collapse.<ref name="SahneyBentonFerry2010RainforestCollapse">{{ cite journal | url=http://geology.geoscienceworld.org/cgi/content/abstract/38/12/1079 | author= Sahney, S., Benton, M.J. & Falcon-Lang, H.J. | year=2010 | title= Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica | journal=Geology | volume = 38 | pages = 1079–1082 | format=PDF | doi=10.1130/G31182.1 | issue=12| url-access=subscription }}</ref><ref name=Kazlev>M. Alan Kazlev (1998) [http://www.palaeos.com/Paleozoic/Carboniferous/Carboniferous.htm The Carboniferous Period of the Paleozoic Era: 299 to 359 million years ago], Palaeos.org, Retrieved on 2008-06-23</ref>
==References== {{reflist}}
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Category:Carboniferous geochronology Category:Pennsylvanian geochronology . Category:Carboniferous Germany Category:Kasimovian Category:Moscovian age Category:Stratigraphy of Europe