View source for Earth:Maastrichtian

{{Short description|Sixth and last age of the Late Cretaceous}}
{{Infobox geologic timespan
| name                         = Maastrichtian
| color                        = Maastrichtian
| time_start                   = 72.1
| time_start_uncertainty       = 0.2
| time_end                     = 66.0
| image_map                    = Opening of western Indian Ocean 70 Ma.png
| caption_map                  = Opening of the western Indian Ocean in the Maastrichtian
| image_outcrop                =
| caption_outcrop              =
| image_art                    =
| caption_art                  =
<!--Chronology-->  
| timeline                     = Cretaceous
| formerly_part_of             =
| partially_contained_in       =
| partially_contains           =
<!--Etymology-->
| name_formality               = Formal
| name_accept_date             =
| alternate_spellings          =
| synonym1                     =
| synonym1_coined              =
| synonym2                     =
| synonym2_coined              =
| synonym3                     =
| synonym3_coined              =
| nicknames                    =
| former_names                 =
| proposed_names               =
<!--Usage Information--> 
| celestial_body               = earth
| usage                        = Global ([[Organization:International Commission on Stratigraphy|ICS]])
| timescales_used              = ICS Time Scale
| formerly_used_by             =
| not_used_by                  =
<!--Definition-->
| chrono_unit                  = Age
| strat_unit                   = Stage
| proposed_by                  =
| type_section                 =
| timespan_formality           = Formal
| lower_boundary_def           = Mean of 12 biostratigraphic criteria
| lower_gssp_location          = Grande Carrière quarry, Landes, {{wipe|France}}
| lower_gssp_coords            = {{Coord|43.6795|N|1.1133|W|display=inline}}
| lower_gssp_accept_date       = February 2001<ref name=OdinLamaurelle2001>{{cite journal |last=Odin |first=Gilles S. |author2=Michèle A. Lamaurelle |title=The global Campanian-Maastrichtian stage boundary |journal=Episodes |year=2001 |volume=24 |issue=4 |pages=229–238  |doi=10.18814/epiiugs/2001/v24i4/002 |doi-access=free}}</ref>
| upper_boundary_def           = [[Chemistry:Iridium|Iridium]] enriched layer associated with a major meteorite impact and subsequent K-Pg extinction event.
| upper_gssp_location          = El Kef Section, El Kef, Tunisia
| upper_gssp_coords            = {{Coord|36.1537|N|8.6486|E|display=inline}}
| upper_gssp_accept_date       = 1991
<!--Atmospheric and Climatic Data-->
| o2                           =
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}}

The '''Maastrichtian''' ({{IPAc-en|pron|m|ɑː|ˈ|s|t|r|ɪ|k|t|i|ə|n}} {{respell|mah|STRICK|tee|ən}}) is, in the [[Organization:International Commission on Stratigraphy|ICS]] geologic timescale, the latest [[Earth:Age (geology)|age]] (uppermost [[Physics:Stage (stratigraphy)|stage]]) of the [[Earth:Late Cretaceous|Late Cretaceous]] [[Earth:Epoch (geology)|Epoch]] or [[Earth:Upper Cretaceous|Upper Cretaceous]] [[Earth:Series (stratigraphy)|Series]], the [[Earth:Cretaceous|Cretaceous]] Period or [[Earth:System (stratigraphy)|System]], and of the [[Earth:Mesozoic|Mesozoic]] Era or [[Earth:Erathem|Erathem]]. It spanned the interval from {{ma|Maastrichtian|Danian|million years ago}}. The Maastrichtian was preceded by the [[Earth:Campanian|Campanian]] and succeeded by the [[Earth:Danian|Danian]] (part of the [[Earth:Paleogene|Paleogene]] and [[Earth:Paleocene|Paleocene]]).<ref name=OggEtal2004>{{cite book |last1=Ogg |first1=James G. |last2=Gradstein |first2= Felix M.  |last3=Smith |first3=A.G. |title=A geologic time scale 2004 |publisher=Cambridge University Press |location=Cambridge, UK |year=2004 |isbn=0-521-78142-6 |url=https://books.google.com/books?id=rse4v1P-f9kC |access-date=8 May 2022}}</ref>

The [[Earth:Cretaceous–Paleogene extinction event|Cretaceous–Paleogene extinction event]] (formerly known as the Cretaceous–[[Earth:Tertiary|Tertiary]] extinction event){{efn|This designation has as a part of it a term, '[[Earth:Tertiary|Tertiary]]', that is now discouraged as a formal geochronological unit by the [[Organization:International Commission on Stratigraphy|International Commission on Stratigraphy]].}} occurred at the end of this age.<ref name=OggEtal2004/>  In this [[Biology:Extinction event|mass extinction]], many commonly recognized groups such as non-avian [[Biology:Dinosaur|dinosaur]]s, [[Biology:Plesiosaur|plesiosaur]]s and [[Biology:Mosasaur|mosasaur]]s, as well as many other lesser-known groups, died out. The cause of the extinction is most commonly linked to [[Astronomy:Chicxulub impactor|an asteroid]] about {{convert|10|to|15|km|mi}} wide<ref name="AGU-20140409">{{cite web |last1=Sleep |first1=Norman H. |last2=Lowe |first2=Donald R. |title=Scientists reconstruct ancient impact that dwarfs dinosaur-extinction blast |url=https://news.agu.org/press-release/scientists-reconstruct-ancient-impact-that-dwarfs-dinosaur-extinction-blast/ |date=9 April 2014 |publisher=[[Organization:American Geophysical Union|American Geophysical Union]] |access-date=15 March 2018}}</ref><ref>{{cite web |url=https://www.bbc.com/news/science-environment-39922998 |title=Dinosaur asteroid hit 'worst possible place' |last=Amos |first=Jonathan |date=15 May 2017 |website=BBC News Online |access-date=16 March 2018}}</ref> colliding with Earth, ending the Cretaceous.

==Stratigraphic definitions==
[[File:Rendzina soil on the Maastrichtian Chalk in Kozubów Landscape Park, Poland.JPG|thumb|upright|[[Earth:Rendzina|Rendzina]] soil on the Maastrichtian Chalk in Kozubów Landscape Park, Poland]]

===Definition===
The Maastrichtian was introduced into scientific literature by Belgian geologist André Hubert Dumont in 1849, after studying rock strata of the [[Earth:Chalk Group|Chalk Group]] close to the Dutch city of Maastricht. These strata are now classified as the [[Earth:Maastricht Formation|Maastricht Formation]] - both formation and stage derive their names from the city.<ref name=JagtJagtYazykova2012>{{cite journal |last1=Jagt |first1=J.W.M |last2=Jagt-Yazykova |first2=E.A. |year=2012 |title=Stratigraphy of the type Maastrichtian – a synthesis |journal=Scripta Geologica |volume=08 |pages=5–32 |url=https://repository.naturalis.nl/pub/428924 |access-date=8 May 2022}}</ref> The Maastricht Formation is known for its fossils from this age, most notably those of the giant sea reptile ''[[Biology:Mosasaurus|Mosasaurus]]'', which in turn derives its name from the nearby river Maas (''mosa'' being Latin for the river Maas).<ref name=StreetThesis>{{cite thesis|author=Hallie P. Street|year=2016|title=A re-assessment of the genus ''Mosasaurus'' (Squamata: Mosasauridae)|type=PhD|publisher=University of Alberta|url=https://era.library.ualberta.ca/items/53bb82a0-7a66-4afb-a26d-b611b5f86136/view/f59a5ee9-9c57-4409-9988-5c8958216f80/Street_Hallie_P_201604_PhD.pdf|doi=10.7939/R31N7XZ1K}}</ref><ref name=OOKMosasaurus1>{{cite web|author=Mike Everhart|title=''Mosasaurus hoffmanni''-The First Discovery of a Mosasaur?|date=May 14, 2010|website=Oceans of Kansas|access-date=November 6, 2019|url=http://oceansofkansas.com/mosahoff.html|archive-url=https://web.archive.org/web/20190904012849/http://oceansofkansas.com/mosahoff.html|archive-date=September 4, 2019|url-status=live}}</ref>

The base of the Maastrichtian Stage is at the first appearance of [[Biology:Ammonite|ammonite]] species ''[[Biology:Pachydiscus|Pachydiscus neubergicus]]''. At the original type locality near Maastricht, the stratigraphic record was later found to be incomplete. A reference profile for the base was then appointed in a section along the Ardour river called ''Grande Carrière'', close to the village of Tercis-les-Bains in southwestern {{wipe|France}}.<ref name="Odin2001">{{cite journal |last1=Odin |first1=G.S. |title=Chapter E5c Numerical age calibration of the Campanian-Maastrichtian succession at Tercis les Bains (landes, france) and in the Bottaccione Gorge (Italy) |journal=Developments in Palaeontology and Stratigraphy |date=2001 |volume=19 |pages=775–782 |doi=10.1016/S0920-5446(01)80068-6|isbn=9780444506474 }}</ref><ref name=OdinLamaurelle2001/> The top of the Maastrichtian Stage is defined to be at the [[Chemistry:Iridium|iridium]] anomaly at the [[Earth:Cretaceous–Paleogene boundary|Cretaceous–Paleogene boundary]] (K–Pg boundary), which is also characterised by the [[Biology:Extinction|extinction]] of many groups of life.{{sfn|Ogg|Gradstein|Smith|2004|p=345}}

===Subdivision===
The Maastrichtian is commonly subdivided into two substages (Upper and Lower) and three ammonite [[Earth:Biozone|biozone]]s. The biozones are (from young to old):<ref name=WardKennedy1993>{{cite journal |jstor=1315613| title=Maastrichtian Ammonites from the Biscay Region (France, Spain) | last1=Ward | first1=Peter D. | last2=Kennedy | first2=W. James | journal=Memoir (The Paleontological Society) | year=1993 | volume=34 | issue=S34 | pages=1–58 | doi=10.1017/S0022336000062223 | bibcode=1993JPal...67S...1W | s2cid=181450798 }}</ref>
*zone of ''[[Biology:Anapachydiscus|Anapachydiscus terminus]]''
*zone of ''Anapachydiscus fresvillensis''
*zone of ''[[Biology:Pachydiscus|Pachydiscus neubergicus]]'' till ''Pachydiscus epiplectus''

The Maastrichtian is roughly coeval with the [[Earth:Lancian|Lancian]] North American Land Mammal Age.

==Palaeogeography and paleoclimate==
The breakup of [[Earth:Pangaea|Pangaea]] was nearly complete in the Maastrichtian, with Australia beginning to break away from Antarctica and Madagascar breaking away from India. However, Arabia had not yet rifted away from Africa. North America was separated from Europe by rift basins, but sea floor spreading had not yet commenced between the two continents.<ref>{{cite book |last1=Torsvik |first1=Trond H. |last2=Cocks |first2=L. Robin M. |title=Earth history and palaeogeography |date=2017 |publisher=Cambridge University Press |location=Cambridge, United Kingdom |isbn=9781107105324 |pages=220, 222, 230}}</ref>

The Pacific Plate was rapidly growing in size as the surrounding oceanic plates were consumed by [[Earth:Subduction|subduction]], and the Pacific-Izanagi Ridge was rapidly approaching Asia.{{sfn|Torsvik|Cocks|2017|p=220}}

Eruption of the [[Earth:Deccan Traps|Deccan Traps]] [[Earth:Large igneous province|large igneous province]] began during the Maastrichtian, at around 67 million years ago. This is thought to be a consequence of India drifting over the Réunion hotspot.{{sfn|Torsvik|Cocks|2017|p=234}}

During the Maastrichtian, the global climate began to shift from the warm and humid climate of the Mesozoic to the colder and more arid climate of the Cenozoic.{{sfn|Torsvik|Cocks|2017|p=234}} Variation of climate with latitude also became greater. This was likely caused by a major reorganization of oceanic circulation that took place at the boundary between the early and late Maastrichtian. This reorganization was triggered by the breach of tectonic barriers in the South Atlantic, permitting deep ocean water to begin circulating from the nascent North Atlantic to the south. This initiated [[Earth:Thermohaline circulation|thermohaline circulation]] similar to that of the modern oceans. At the same time, the [[Earth:Laramide orogeny|Laramide orogeny]] drained the [[Earth:Western Interior Seaway|Western Interior Seaway]] of North America, further contributing to global cooling.<ref name="FrankArthur1999">{{cite journal |last1=Frank |first1=Tracy D. |last2=Arthur |first2=Michael A. |title=Tectonic forcings of Maastrichtian ocean-climate evolution |journal=Paleoceanography |date=April 1999 |volume=14 |issue=2 |pages=103–117 |doi=10.1029/1998PA900017|bibcode=1999PalOc..14..103F |s2cid=30926910 |doi-access=free }}</ref>

==Paleontology==
[[File:Hemipneustes leymeriei MHNT.jpg|thumb|Fossil of ''Hemipneustes leymeriei'']]
Dinosaurs remained the dominant large terrestrial animals throughout the Maasastrichtian, though mammals with internal organs similar to modern mammals were also present. Both ammonites and pterosaurs were in serious decline during the Maastrichtian.{{sfn|Torsvik|Cocks|2017|p=238, 239}}

=== Dinosaurs ===

==== Birds ====
Several archaic clades of birds, such as [[Biology:Enantiornithes|Enantiornithes]], [[Biology:Ichthyornithes|Ichthyornithes]], and [[Biology:Hesperornithes|Hesperornithes]], persisted to the latest Maastrichtian but became extinct during the Cretaceous-Paleogene extinction event.<ref>{{cite journal |last1=Longrich |first1=Nicholas R. |last2=Tokaryk |first2=Tim |last3=Field |first3=Daniel J. |title=Mass extinction of birds at the Cretaceous–Paleogene (K–Pg) boundary |journal=Proceedings of the National Academy of Sciences |date=13 September 2011 |volume=108 |issue=37 |pages=15253–15257 |doi=10.1073/pnas.1110395108|pmid=21914849 |pmc=3174646 |bibcode=2011PNAS..10815253L |doi-access=free }}</ref>

=== Pterosaurs ===

Traditionally, pterosaur faunas of the Maastrichtian were assumed to be dominated by [[Biology:Azhdarchidae|azhdarchids]], with other pterosaur groups having become extinct earlier on. However, more recent findings suggest a fairly composite pterosaur diversity: at least six ("Nyctosaurus" ''lamegoi'', a Mexican humerus, a Jordan humerus and several taxa from Morocco) [[Biology:Nyctosauridae|nyctosaur]]s date to this period, as do a few [[Biology:Pteranodontidae|pteranodontids]], and ''Navajodactylus'', tentatively assigned to Azhdarchidae, lacks any synapomorphies of the group.<ref>Wilton, Mark P. (2013). Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press. {{ISBN|0691150613}}.</ref><ref>Barrett, P. M., Butler, R. J., Edwards, N. P., & Milner, A. R. (2008). Pterosaur distribution in time and space: an atlas. Zitteliana: 61-107.[1].</ref> This seems to underscore a higher diversity of terminal Cretaceous pterosaurs than previously thought.<ref>Carroll, N. REASSIGNMENT OF MONTANAZHDARCHO MINOR AS A NON-AZHDARCHID MEMBER OF THE AZHDARCHOIDEA, SVP 2015.</ref><ref>{{cite journal | doi=10.5252/g2012n4a10 | title=Systematic reinterpretation of ''Piksi'' barbarulna ''Varricchio'', 2002 from the Two Medicine Formation (Upper Cretaceous) of Western USA (Montana) as a pterosaur rather than a bird | year=2012 | last1=Agnolin | first1=Federico L. | last2=Varricchio | first2=David | journal=Geodiversitas | volume=34 | issue=4 | pages=883–894 | s2cid=56002643 | url=https://zenodo.org/record/5376780 }}</ref><ref>{{cite journal | doi=10.1371/journal.pbio.2001663 | title=Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary | year=2018 | last1=Longrich | first1=Nicholas R. | last2=Martill | first2=David M. | last3=Andres | first3=Brian | journal=PLOS Biology | volume=16 | issue=3 | pages=e2001663 | pmid=29534059 | pmc=5849296 | doi-access=free }}</ref>

[[File:Main floristic types from the Maastrichtian - journal.pone.0052455.g007-left.png|thumb|Maastrichtian landscape]]

=== Flora ===
The radiation of [[Biology:Angiosperms|angiosperms]] (flowering plants) was well under way in the Maastrichtian. From 50% to 80% of all [[Biology:Genus|genera]] of land plants were angiosperms, though gymnosperms and ferns still covered larger areas of the land surface.{{sfn|Torsvik|Cocks|2017|p=238}}

==Notes==
{{notelist}}

==References==
{{Reflist}}

==External links==
*[https://web.archive.org/web/20100822030129/http://www.stratigraphy.org/bak/geowhen/stages/Maastrichtian.html GeoWhen Database - Maastrichtian]
*[http://ghkclass.com/ghkC.html?Maastrichtian ghK Classification - Maastrichtian]
*[http://stratigraphy.science.purdue.edu/charts/Timeslices/3_Late_Cret.pdf Late Cretaceous timescale], at the website of the subcommission for stratigraphic information of the ICS
*[https://web.archive.org/web/20040511104934/http://norges.uio.no/timescale/Fig18.1_Cret_colA.pdf Stratigraphic chart of the Late Cretaceous], at the website of Norges Network of offshore records of geology and stratigraphy
*[http://www.foraminifera.eu/querydb.php?stage=Maastrichtian&aktion=suche Maastrichtian Microfossils: 60+ images of Foraminifera]

{{Geological history|p|m}}

[[Category:Maastrichtian| ]]
[[Category:Maastrichtian life| ]]
[[Category:Late Cretaceous|*06]]
[[Category:Cretaceous geochronology]]

{{Sourceattribution|Maastrichtian}}